Change in the surface ANTIGEN of a microorganism. There are two different types. One is a phenomenon, especially associated with INFLUENZA VIRUSES, where they undergo spontaneous variation both as slow antigenic drift and sudden emergence of new strains (antigenic shift). The second type is when certain PARASITES, especially trypanosomes, PLASMODIUM, and BORRELIA, survive the immune response of the host by changing the surface coat (antigen switching). (From Herbert et al., The Dictionary of Immunology, 4th ed)
Genotypic differences observed among individuals in a population.
Glycoproteins attached to the surface coat of the trypanosome. Many of these glycoproteins show amino acid sequence diversity expressed as antigenic variations. This continuous development of antigenically distinct variants in the course of infection ensures that some trypanosomes always survive the development of immune response to propagate the infection.
The functional hereditary units of protozoa.
A hemoflagellate subspecies of parasitic protozoa that causes nagana in domestic and game animals in Africa. It apparently does not infect humans. It is transmitted by bites of tsetse flies (Glossina).
A genus of flagellate protozoans found in the blood and lymph of vertebrates and invertebrates, both hosts being required to complete the life cycle.
Substances elaborated by bacteria that have antigenic activity.
Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.
Proteins found in any species of protozoan.
A species of protozoa that is a cause of bovine babesiosis. Ticks of the genera Boophilus, Rhipicephalus, and IXODES are the chief vectors.
Any part or derivative of any protozoan that elicits immunity; malaria (Plasmodium) and trypanosome antigens are presently the most frequently encountered.
Proteins that are structural components of bacterial fimbriae (FIMBRIAE, BACTERIAL) or sex pili (PILI, SEX).
A species of gram-negative, aerobic bacteria primarily found in purulent venereal discharges. It is the causative agent of GONORRHEA.
A genus of gram-negative, anaerobic, helical bacteria, various species of which produce RELAPSING FEVER in humans and other animals.
Infection with protozoa of the genus TRYPANOSOMA.
Sites on an antigen that interact with specific antibodies.
Substances elaborated by viruses that have antigenic activity.
The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.
Proteins isolated from the outer membrane of Gram-negative bacteria.
A species of protozoa that is the causal agent of falciparum malaria (MALARIA, FALCIPARUM). It is most prevalent in the tropics and subtropics.
Production of new arrangements of DNA by various mechanisms such as assortment and segregation, CROSSING OVER; GENE CONVERSION; GENETIC TRANSFORMATION; GENETIC CONJUGATION; GENETIC TRANSDUCTION; or mixed infection of viruses.
The relationship between an invertebrate and another organism (the host), one of which lives at the expense of the other. Traditionally excluded from definition of parasites are pathogenic BACTERIA; FUNGI; VIRUSES; and PLANTS; though they may live parasitically.
The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.
A species of parasitic EUKARYOTES that attaches itself to the intestinal mucosa and feeds on mucous secretions. The organism is roughly pear-shaped and motility is somewhat erratic, with a slow oscillation about the long axis.
A hemoflagellate subspecies of parasitic protozoa that causes Gambian or West African sleeping sickness in humans. The vector host is usually the tsetse fly (Glossina).
A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.
Proteins found in any species of bacterium.
A disease endemic among people and animals in Central Africa. It is caused by various species of trypanosomes, particularly T. gambiense and T. rhodesiense. Its second host is the TSETSE FLY. Involvement of the central nervous system produces "African sleeping sickness." Nagana is a rapidly fatal trypanosomiasis of horses and other animals.
An infection of the SMALL INTESTINE caused by the flagellated protozoan GIARDIA LAMBLIA. It is spread via contaminated food and water and by direct person-to-person contact.
An acute infection characterized by recurrent episodes of PYREXIA alternating with asymptomatic intervals of apparent recovery. This condition is caused by SPIROCHETES of the genus BORRELIA. It is transmitted by the BITES of either the body louse (PEDICULUS humanus corporis), for which humans are the reservoir, or by soft ticks of the genus ORNITHODOROS, for which rodents and other animals are the principal reservoirs.
Methods used by pathogenic organisms to evade a host's immune system.
Antigens on surfaces of cells, including infectious or foreign cells or viruses. They are usually protein-containing groups on cell membranes or walls and may be isolated.
A genus of gram-negative bacteria whose organisms are obligate parasites of vertebrates. Species are transmitted by arthropod vectors with the host range limited to ruminants. Anaplasma marginale is the most pathogenic species and is the causative agent of severe bovine anaplasmosis.
The complete genetic complement contained in a set of CHROMOSOMES in a protozoan.
Ribonucleic acid in protozoa having regulatory and catalytic roles as well as involvement in protein synthesis.
Deoxyribonucleic acid that makes up the genetic material of protozoa.
Antibodies produced by a single clone of cells.
The relationships of groups of organisms as reflected by their genetic makeup.
Serological reactions in which an antiserum against one antigen reacts with a non-identical but closely related antigen.
A species of bacteria present in man and many kinds of animals and birds, often causing infertility and/or abortion.
The measurement of infection-blocking titer of ANTISERA by testing a series of dilutions for a given virus-antiserum interaction end-point, which is generally the dilution at which tissue cultures inoculated with the serum-virus mixtures demonstrate cytopathology (CPE) or the dilution at which 50% of test animals injected with serum-virus mixtures show infectivity (ID50) or die (LD50).
Process of determining and distinguishing species of bacteria or viruses based on antigens they share.
The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.
The asymmetrical segregation of genes during replication which leads to the production of non-reciprocal recombinant strands and the apparent conversion of one allele into another. Thus, e.g., the meiotic products of an Aa individual may be AAAa or aaaA instead of AAaa, i.e., the A allele has been converted into the a allele or vice versa.
A genus of the family PICORNAVIRIDAE infecting mainly cloven-hoofed animals. They cause vesicular lesions and upper respiratory tract infections. FOOT AND MOUTH DISEASE VIRUS is the type species.
Deoxyribonucleic acid that makes up the genetic material of bacteria.
A set of genes descended by duplication and variation from some ancestral gene. Such genes may be clustered together on the same chromosome or dispersed on different chromosomes. Examples of multigene families include those that encode the hemoglobins, immunoglobulins, histocompatibility antigens, actins, tubulins, keratins, collagens, heat shock proteins, salivary glue proteins, chorion proteins, cuticle proteins, yolk proteins, and phaseolins, as well as histones, ribosomal RNA, and transfer RNA genes. The latter three are examples of reiterated genes, where hundreds of identical genes are present in a tandem array. (King & Stanfield, A Dictionary of Genetics, 4th ed)
Malaria caused by PLASMODIUM FALCIPARUM. This is the severest form of malaria and is associated with the highest levels of parasites in the blood. This disease is characterized by irregularly recurring febrile paroxysms that in extreme cases occur with acute cerebral, renal, or gastrointestinal manifestations.
Thin, hairlike appendages, 1 to 20 microns in length and often occurring in large numbers, present on the cells of gram-negative bacteria, particularly Enterobacteriaceae and Neisseria. Unlike flagella, they do not possess motility, but being protein (pilin) in nature, they possess antigenic and hemagglutinating properties. They are of medical importance because some fimbriae mediate the attachment of bacteria to cells via adhesins (ADHESINS, BACTERIAL). Bacterial fimbriae refer to common pili, to be distinguished from the preferred use of "pili", which is confined to sex pili (PILI, SEX).
A terminal section of a chromosome which has a specialized structure and which is involved in chromosomal replication and stability. Its length is believed to be a few hundred base pairs.
Serologic tests in which a known quantity of antigen is added to the serum prior to the addition of a red cell suspension. Reaction result is expressed as the smallest amount of antigen which causes complete inhibition of hemagglutination.
A genus of gram-negative, mostly facultatively anaerobic bacteria in the family MYCOPLASMATACEAE. The cells are bounded by a PLASMA MEMBRANE and lack a true CELL WALL. Its organisms are pathogens found on the MUCOUS MEMBRANES of humans, ANIMALS, and BIRDS.
Viral disease of horses caused by the equine infectious anemia virus (EIAV; INFECTIOUS ANEMIA VIRUS, EQUINE). It is characterized by intermittent fever, weakness, and anemia. Chronic infection consists of acute episodes with remissions.
A family of RNA viruses causing INFLUENZA and other diseases. There are five recognized genera: INFLUENZAVIRUS A; INFLUENZAVIRUS B; INFLUENZAVIRUS C; ISAVIRUS; and THOGOTOVIRUS.
Immunoglobulins produced in a response to BACTERIAL ANTIGENS.
Lipid-protein complexes involved in the transportation and metabolism of lipids in the body. They are spherical particles consisting of a hydrophobic core of TRIGLYCERIDES and CHOLESTEROL ESTERS surrounded by a layer of hydrophilic free CHOLESTEROL; PHOSPHOLIPIDS; and APOLIPOPROTEINS. Lipoproteins are classified by their varying buoyant density and sizes.
An infectious disease caused by a spirochete, BORRELIA BURGDORFERI, which is transmitted chiefly by Ixodes dammini (see IXODES) and pacificus ticks in the United States and Ixodes ricinis (see IXODES) in Europe. It is a disease with early and late cutaneous manifestations plus involvement of the nervous system, heart, eye, and joints in variable combinations. The disease was formerly known as Lyme arthritis and first discovered at Old Lyme, Connecticut.
A specific species of bacteria, part of the BORRELIA BURGDORFERI GROUP, whose common name is Lyme disease spirochete.
Immunoglobulins produced in response to VIRAL ANTIGENS.
The functional hereditary units of BACTERIA.
Interruption or suppression of the expression of a gene at transcriptional or translational levels.
Tests that are dependent on the clumping of cells, microorganisms, or particles when mixed with specific antiserum. (From Stedman, 26th ed)
Sequences of DNA or RNA that occur in multiple copies. There are several types: INTERSPERSED REPETITIVE SEQUENCES are copies of transposable elements (DNA TRANSPOSABLE ELEMENTS or RETROELEMENTS) dispersed throughout the genome. TERMINAL REPEAT SEQUENCES flank both ends of another sequence, for example, the long terminal repeats (LTRs) on RETROVIRUSES. Variations may be direct repeats, those occurring in the same direction, or inverted repeats, those opposite to each other in direction. TANDEM REPEAT SEQUENCES are copies which lie adjacent to each other, direct or inverted (INVERTED REPEAT SEQUENCES).
A species of gram-negative bacteria originally isolated from urethral specimens of patients with non-gonoccocal URETHRITIS. In primates it exists in parasitic association with ciliated EPITHELIAL CELLS in the genital and respiratory tracts.
Specific hemagglutinin subtypes encoded by VIRUSES.
The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.
Serum that contains antibodies. It is obtained from an animal that has been immunized either by ANTIGEN injection or infection with microorganisms containing the antigen.
The degree of similarity between sequences of amino acids. This information is useful for the analyzing genetic relatedness of proteins and species.
The arrangement of two or more amino acid or base sequences from an organism or organisms in such a way as to align areas of the sequences sharing common properties. The degree of relatedness or homology between the sequences is predicted computationally or statistically based on weights assigned to the elements aligned between the sequences. This in turn can serve as a potential indicator of the genetic relatedness between the organisms.
Subunits of the antigenic determinant that are most easily recognized by the immune system and thus most influence the specificity of the induced antibody.
Red blood cells. Mature erythrocytes are non-nucleated, biconcave disks containing HEMOGLOBIN whose function is to transport OXYGEN.
The type species of the genus INFLUENZAVIRUS A that causes influenza and other diseases in humans and animals. Antigenic variation occurs frequently between strains, allowing classification into subtypes and variants. Transmission is usually by aerosol (human and most non-aquatic hosts) or waterborne (ducks). Infected birds shed the virus in their saliva, nasal secretions, and feces.
Immunoglobulins produced in a response to PROTOZOAN ANTIGENS.
An order of slender, flexuous, helically coiled bacteria, with one or more complete turns in the helix.
A genus of flagellate intestinal EUKARYOTES parasitic in various vertebrates, including humans. Characteristics include the presence of four pairs of flagella arising from a complicated system of axonemes and cysts that are ellipsoidal to ovoidal in shape.
The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells.
Sensitive assay using radiolabeled ANTIGENS to detect specific ANTIBODIES in SERUM. The antigens are allowed to react with the serum and then precipitated using a special reagent such as PROTEIN A sepharose beads. The bound radiolabeled immunoprecipitate is then commonly analyzed by gel electrophoresis.
A genus of protozoa that comprise the malaria parasites of mammals. Four species infect humans (although occasional infections with primate malarias may occur). These are PLASMODIUM FALCIPARUM; PLASMODIUM MALARIAE; PLASMODIUM OVALE, and PLASMODIUM VIVAX. Species causing infection in vertebrates other than man include: PLASMODIUM BERGHEI; PLASMODIUM CHABAUDI; P. vinckei, and PLASMODIUM YOELII in rodents; P. brasilianum, PLASMODIUM CYNOMOLGI; and PLASMODIUM KNOWLESI in monkeys; and PLASMODIUM GALLINACEUM in chickens.
A species of gram-negative bacteria and causative agent of severe bovine ANAPLASMOSIS. It is the most pathogenic of the ANAPLASMA species.
A disease of cattle caused by parasitization of the red blood cells by bacteria of the genus ANAPLASMA.
Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor.
The genetic constitution of the individual, comprising the ALLELES present at each GENETIC LOCUS.
The process of cumulative change at the level of DNA; RNA; and PROTEINS, over successive generations.
Substances that are recognized by the immune system and induce an immune reaction.
The regular and simultaneous occurrence in a single interbreeding population of two or more discontinuous genotypes. The concept includes differences in genotypes ranging in size from a single nucleotide site (POLYMORPHISM, SINGLE NUCLEOTIDE) to large nucleotide sequences visible at a chromosomal level.
A species of gram-negative bacteria in the genus ANAPLASMA, family ANAPLASMATACEAE, formerly called Ehrlichia phagocytophila or Ehrlichia equi. This organism is tick-borne (IXODES) and causes disease in horses and sheep. In humans, it causes human granulocytic EHRLICHIOSIS.
A species of LENTIVIRUS, subgenus equine lentiviruses (LENTIVIRUSES, EQUINE), causing acute and chronic infection in horses. It is transmitted mechanically by biting flies, mosquitoes, and midges, and iatrogenically through unsterilized equipment. Chronic infection often consists of acute episodes with remissions.
A subdiscipline of genetics which deals with the genetic basis of the immune response (IMMUNITY).
The degree of pathogenicity within a group or species of microorganisms or viruses as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the host. The pathogenic capacity of an organism is determined by its VIRULENCE FACTORS.
Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.
A species of gram-negative, aerobic BACTERIA. It is a commensal and pathogen only of humans, and can be carried asymptomatically in the NASOPHARYNX. When found in cerebrospinal fluid it is the causative agent of cerebrospinal meningitis (MENINGITIS, MENINGOCOCCAL). It is also found in venereal discharges and blood. There are at least 13 serogroups based on antigenic differences in the capsular polysaccharides; the ones causing most meningitis infections being A, B, C, Y, and W-135. Each serogroup can be further classified by serotype, serosubtype, and immunotype.
A family of recombinases initially identified in BACTERIA. They catalyze the ATP-driven exchange of DNA strands in GENETIC RECOMBINATION. The product of the reaction consists of a duplex and a displaced single-stranded loop, which has the shape of the letter D and is therefore called a D-loop structure.
Variant forms of the same gene, occupying the same locus on homologous CHROMOSOMES, and governing the variants in production of the same gene product.
In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)
The property of antibodies which enables them to react with some ANTIGENIC DETERMINANTS and not with others. Specificity is dependent on chemical composition, physical forces, and molecular structure at the binding site.
Methods used for studying the interactions of antibodies with specific regions of protein antigens. Important applications of epitope mapping are found within the area of immunochemistry.
Cell-surface components or appendages of bacteria that facilitate adhesion (BACTERIAL ADHESION) to other cells or to inanimate surfaces. Most fimbriae (FIMBRIAE, BACTERIAL) of gram-negative bacteria function as adhesins, but in many cases it is a minor subunit protein at the tip of the fimbriae that is the actual adhesin. In gram-positive bacteria, a protein or polysaccharide surface layer serves as the specific adhesin. What is sometimes called polymeric adhesin (BIOFILMS) is distinct from protein adhesin.
The biosynthesis of RNA carried out on a template of DNA. The biosynthesis of DNA from an RNA template is called REVERSE TRANSCRIPTION.
The sequential correspondence of nucleotides in one nucleic acid molecule with those of another nucleic acid molecule. Sequence homology is an indication of the genetic relatedness of different organisms and gene function.
Infections with species of the genus MYCOPLASMA.
Differential and non-random reproduction of different genotypes, operating to alter the gene frequencies within a population.
Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control (induction or repression) of gene action at the level of transcription or translation.
A sequence of amino acids in a polypeptide or of nucleotides in DNA or RNA that is similar across multiple species. A known set of conserved sequences is represented by a CONSENSUS SEQUENCE. AMINO ACID MOTIFS are often composed of conserved sequences.
One of the three domains of life (the others being BACTERIA and ARCHAEA), also called Eukarya. These are organisms whose cells are enclosed in membranes and possess a nucleus. They comprise almost all multicellular and many unicellular organisms, and are traditionally divided into groups (sometimes called kingdoms) including ANIMALS; PLANTS; FUNGI; and various algae and other taxa that were previously part of the old kingdom Protista.
The genetic complement of a BACTERIA as represented in its DNA.
Large, hoofed mammals of the family EQUIDAE. Horses are active day and night with most of the day spent seeking and consuming food. Feeding peaks occur in the early morning and late afternoon, and there are several daily periods of rest.
An immunoassay utilizing an antibody labeled with an enzyme marker such as horseradish peroxidase. While either the enzyme or the antibody is bound to an immunosorbent substrate, they both retain their biologic activity; the change in enzyme activity as a result of the enzyme-antibody-antigen reaction is proportional to the concentration of the antigen and can be measured spectrophotometrically or with the naked eye. Many variations of the method have been developed.
In vitro method for producing large amounts of specific DNA or RNA fragments of defined length and sequence from small amounts of short oligonucleotide flanking sequences (primers). The essential steps include thermal denaturation of the double-stranded target molecules, annealing of the primers to their complementary sequences, and extension of the annealed primers by enzymatic synthesis with DNA polymerase. The reaction is efficient, specific, and extremely sensitive. Uses for the reaction include disease diagnosis, detection of difficult-to-isolate pathogens, mutation analysis, genetic testing, DNA sequencing, and analyzing evolutionary relationships.
Invertebrates or non-human vertebrates which transmit infective organisms from one host to another.
Gram-negative helical bacteria, in the genus BORRELIA, that are the etiologic agents of LYME DISEASE. The group comprises many specific species including Borrelia afzelii, Borellia garinii, and BORRELIA BURGDORFERI proper. These spirochetes are generally transmitted by several species of ixodid ticks.
The degree of similarity between sequences. Studies of AMINO ACID SEQUENCE HOMOLOGY and NUCLEIC ACID SEQUENCE HOMOLOGY provide useful information about the genetic relatedness of genes, gene products, and species.
Blood-sucking acarid parasites of the order Ixodida comprising two families: the softbacked ticks (ARGASIDAE) and hardbacked ticks (IXODIDAE). Ticks are larger than their relatives, the MITES. They penetrate the skin of their host by means of highly specialized, hooked mouth parts and feed on its blood. Ticks attack all groups of terrestrial vertebrates. In humans they are responsible for many TICK-BORNE DISEASES, including the transmission of ROCKY MOUNTAIN SPOTTED FEVER; TULAREMIA; BABESIOSIS; AFRICAN SWINE FEVER; and RELAPSING FEVER. (From Barnes, Invertebrate Zoology, 5th ed, pp543-44)
Diseases of domestic cattle of the genus Bos. It includes diseases of cows, yaks, and zebus.
An enzyme that catalyzes the hydrolysis of alpha-2,3, alpha-2,6-, and alpha-2,8-glycosidic linkages (at a decreasing rate, respectively) of terminal sialic residues in oligosaccharides, glycoproteins, glycolipids, colominic acid, and synthetic substrate. (From Enzyme Nomenclature, 1992)
Layers of protein which surround the capsid in animal viruses with tubular nucleocapsids. The envelope consists of an inner layer of lipids and virus specified proteins also called membrane or matrix proteins. The outer layer consists of one or more types of morphological subunits called peplomers which project from the viral envelope; this layer always consists of glycoproteins.

Genetic and antigenic variation of capsid protein VP7 of serotype G1 human rotavirus isolates. (1/863)

The deduced amino acid sequences of the outer capsid protein, VP7, of serotype G1 rotavirus clinical isolates collected over a 6 year period (1990-1995) in Melbourne, Australia, were examined. Phylogenetic analysis characterized the sequences into two discrete clusters representing two of the four global lineages of human G1 VP7 proteins. Antigenic characterization using a panel of serotype G1-specific neutralizing monoclonal antibodies classified lineage II isolates (1990-1993) as monotype G1a while lineage I isolates were classified as monotype G1b (1993-1995). Examination of the sequences of the neutralization epitope regions of VP7 revealed a particular amino acid substitution at residue 94 in region A (Asp --> Ser/Thr) that correlated with lineage and monotype designation. Our results indicated that temporal genetic variation of the VP7 of serotype G1 rotaviruses was associated with changes in the antigenicity of these isolates.  (+info)

The major immunogenic epitopes of Epstein-Barr virus (EBV) nuclear antigen 1 are encoded by sequence domains which vary among nasopharyngeal carcinoma biopsies and EBV-associated cell lines. (2/863)

Epstein-Barr virus (EBV) nuclear antigen 1 (EBNA-1) is a protein expressed consistently in EBV-infected cells and EBV-associated malignant tissues. A panel of monoclonal antibodies (MAbs) was generated against the C terminus of EBNA-1 and evaluated for the detection of EBNA-1 in different cell lines. The epitopes recognized were mapped. Since sequence variations of EBNA-1 have been reported in nasopharyngeal carcinoma (NPC) tissues and in infected healthy individuals, the ability of these MAbs to recognize a recombinant protein derived from an NPC biopsy was also analysed. MAb 4H11 appeared to react with EBNA-1 sequences from different sources, whereas MAbs 5C11, 5F12 and 8F6 failed to recognize a recombinant EBNA-1 protein cloned from an NPC patient. Using different recombinant EBNA-1 fragments in an immunoblot format, this study demonstrates that the domain bounded by amino acids 408 and 498 is very immunogenic in mice in that epitopes in this region are recognized by various MAbs. Amino acid sequences of EBNA-1 were also deduced from nucleotide sequences amplified from three Burkitt's lymphoma cell lines, two spontaneous lymphoblastoid cell lines, two NPC biopsies and one NPC hybrid cell line, NPC-KT, and compared to the sequence from B95-8. The amino acid sequence of EBNA-1 in Akata is almost identical to that in an NPC biopsy, except for amino acid 585. The results of this study indicate that the immunogenic epitopes of EBNA-1 are highly variable.  (+info)

Antigenic variation in malaria: a 3' genomic alteration associated with the expression of a P. knowlesi variant antigen. (3/863)

Antigenic variation of malaria parasites was discovered in P. knowlesi, using a schizont-infected cell agglutination (SICA) assay to detect variant antigens expressed at the surface of infected erythrocytes. Later studies utilizing stable clones, Pk1(A+) and its direct derivative, Pk1(B+)1+, showed that SICA[+] clones express distinct parasite-encoded antigens of approximately 200 kDa. Here we identify a P. knowlesi variant antigen gene and cDNA and demonstrate that it encodes the 205 kDa variant antigen expressed by B+ parasites. This gene belongs to a multigene family, which we term SICAvar. Its ten-exon structure with seven cysteine-rich coding modules is unique compared to P. falciparum var genes. Further, we highlight a 3' genomic alteration that we predict is related to SICAvar gene switching.  (+info)

Phase variations of the Mycoplasma penetrans main surface lipoprotein increase antigenic diversity. (4/863)

Mycoplasma penetrans is a recently identified mycoplasma, isolated from urine samples collected from human immunodeficiency virus (HIV)-infected patients. Its presence is significantly associated with HIV infection. The major antigen recognized during natural and experimental infections is an abundant P35 lipoprotein which, upon extraction, segregates in the Triton X-114 detergent phase and is the basis of M. penetrans-specific serological assays. We report here that the P35 antigen undergoes spontaneous and reversible phase variation at high frequency, leading to heterogeneous populations of mycoplasmas, even when derived from a clonal lineage. This variation was found to be determined at the transcription level, and although this property is not unique among the members of the class Mollicutes, the mechanism by which it occurs in M. penetrans differs from those previously described for other Mycoplasma species. Indeed, the P35 phase variation was due neither to a p35 gene rearrangement nor to point mutations within the gene itself or its promoter. The P35 phase variation in the different variants obtained was concomitant with modifications in the pattern of other expressed lipoproteins, probably due to regulated expression of selected members of a gene family which was found to potentially encode similar lipoproteins. M. penetrans variants could be selected on the basis of their lack of colony immunoreactivity with a polyclonal antiserum against a Triton X-114 extract, strongly suggesting that the mechanisms involved in altering surface antigen expression might allow evasion of the humoral immune response of the infected host.  (+info)

Molecular and functional analysis of a conserved CTL epitope in HIV-1 p24 recognized from a long-term nonprogressor: constraints on immune escape associated with targeting a sequence essential for viral replication. (5/863)

It has been hypothesized that sequence variation within CTL epitopes leading to immune escape plays a role in the progression of HIV-1 infection. Only very limited data exist that address the influence of biologic characteristics of CTL epitopes on the emergence of immune escape variants and the efficiency of suppression HIV-1 by CTL. In this report, we studied the effects of HIV-1 CTL epitope sequence variation on HIV-1 replication. The highly conserved HLA-B14-restricted CTL epitope DRFYKTLRAE in HIV-1 p24 was examined, which had been defined as the immunodominant CTL epitope in a long-term nonprogressing individual. We generated a set of viral mutants on an HX10 background differing by a single conservative or nonconservative amino acid substitution at each of the P1 to P9 amino acid residues of the epitope. All of the nonconservative amino acid substitutions abolished viral infectivity and only 5 of 10 conservative changes yielded replication-competent virus. Recognition of these epitope sequence variants by CTL was tested using synthetic peptides. All mutations that abrogated CTL recognition strongly impaired viral replication, and all replication-competent viral variants were recognized by CTL, although some variants with a lower efficiency. Our data indicate that this CTL epitope is located within a viral sequence essential for viral replication. Targeting CTL epitopes within functionally important regions of the HIV-1 genome could limit the chance of immune evasion.  (+info)

Spontaneous regression of primary autoreactivity during chronic progression of experimental autoimmune encephalomyelitis and multiple sclerosis. (6/863)

Experimental autoimmune encephalomyelitis (EAE) is a widely used animal model for multiple sclerosis (MS). EAE is typically initiated by CD4(+) T helper cell type 1 (Th1) autoreactivity directed against a single priming immunodominant myelin peptide determinant. Recent studies have shown that clinical progression of EAE involves the accumulation of neo-autoreactivity, commonly referred to as epitope spreading, directed against peptide determinants not involved in the priming process. This study directly addresses the relative roles of primary autoreactivity and secondary epitope spreading in the progression of both EAE and MS. To this end we serially evaluated the development of several epitope-spreading cascades in SWXJ mice primed with distinctly different encephalitogenic determinants of myelin proteolipid protein. In a series of analogous experiments, we examined the development of epitope spreading in patients with isolated monosymptomatic demyelinating syndrome as their disease progressed to clinically definite MS. Our results indicate that in both EAE and MS, primary proliferative autoreactivity associated with onset of clinical disease invariably regresses with time and is often undetectable during periods of disease progression. In contrast, the emergence of sustained secondary autoreactivity to spreading determinants is consistently associated with disease progression in both EAE and MS. Our results indicate that chronic progression of EAE and MS involves a shifting of autoreactivity from primary initiating self-determinants to defined cascades of secondary determinants that sustain the self-recognition process during disease progression.  (+info)

Antigenic heterogeneity of the hepatitis C virus NS4 protein as modeled with synthetic peptides. (7/863)

The effect of sequence heterogeneity on the immunologic properties of two strong antigenic regions of the hepatitis C virus (HCV) NS4 protein was studied by using a set of 443 overlapping 20-mer synthetic peptides. One antigenic region comprising the cleavage site between NS4a and NS4b (region 5-1-1) was modeled with peptides derived from 73 different known sequences, representing HCV genotypes 1-6. The other antigenic region, designated region 59 and located at the C-terminus of the NS4b protein, was modeled with peptides from 7 known sequences representing genotypes 1-3. All peptides were tested for antigenic reactivity by enzyme immunoassay with a panel of anti-HCV-positive serum specimens representing genotypes 1-5. The data demonstrated that immunoreactive peptides fell into two groups. One group, represented by N-terminal peptides, demonstrated genotype-independent immunoreactivity; the other group, from the central part of region 5-1-1, showed strict genotype specificity. Nineteen peptides from the genotype-independent group strongly immunoreacted with a wide range of serum samples containing antibodies to all 5 HCV genotypes. Twenty-five peptides from the genotype-specific group were found to strongly react with serum containing antibodies only to the genotype from which the peptides were derived. Similar to the N-terminal part of region 5-1-1, peptides derived from region 59 did not show genotype-specific immunoreactivity. Some peptides derived from the central part of region 59 showed very strong and broad antigenic reactivity. Thus, after examining two antigenic regions of the NS4 protein, we identified short sequences that can be used for the efficient detection of either genotype-independent or genotype-specific HCV antibodies.  (+info)

Structural and evolutionary inference from molecular variation in Neisseria porins. (8/863)

The porin proteins of the pathogenic Neisseria species, Neisseria gonorrhoeae and Neisseria meningitidis, are important as serotyping antigens, putative vaccine components, and for their proposed role in the intracellular colonization of humans. A three-dimensional structural homology model for Neisseria porins was generated from Escherichia coli porin structures and N. meningitidis PorA and PorB sequences. The Neisseria sequences were readily assembled into the 16-strand beta-barrel fold characteristic of porins, despite relatively low sequence identity with the Escherichia proteins. The model provided information on the spatial relationships of variable regions of peptide sequences in the PorA and PorB trimers and insights relevant to the use of these proteins in vaccines. The nucleotide sequences of the porin genes from a number of other Neisseria species were obtained by PCR direct sequencing and from GenBank. Alignment and analysis of all available Neisseria porin sequences by use of the structurally conserved regions derived from the PorA and PorB structural models resulted in the recovery of an improved phylogenetic signal. Phylogenetic analyses were consistent with an important role for horizontal genetic exchange in the emergence of different porin classes and confirmed the close evolutionary relationships of the porins from N. meningitidis, N. gonorrhoeae, Neisseria lactamica, and Neisseria polysaccharea. Only members of this group contained three conserved lysine residues which form a potential GTP binding site implicated in pathogenesis. The model placed these residues on the inside of the pore, in close proximity, consistent with their role in regulating pore function when inserted into host cells.  (+info)

Looking for antigenic variation? Find out information about antigenic variation. Alteration of an antigen on the surface of a microorganism; may enable a pathogenic mocroorganism to evade destruction by the hosts immune system Explanation of antigenic variation
Cesarean delivery and the risk-benefit calculus. Influenza vaccine--outmaneuvering antigenic shift and drift. Estimating the number of potential organ donors in the United States
Different virus families have different levels of ability to alter their genomes and trick the immune system into not recognizing. Some viruses have relatively unchanging genomes like paramyxoviruses while others like influenza have rapidly changing genomes that inhibit our ability to create long lasting vaccines against the disease. Viruses in general have much faster rate of mutation of their genomes than human or bacterial cells. In general viruses with shorter genomes have faster rates of mutation than longer genomes since they have a faster rate of replication.[15] It was classically thought that viruses with an RNA genome always had a faster rate of antigenic variation than those with a DNA genome because RNA polymerase lacks a mechanism for checking for mistakes in translation but recent work by Duffy et al. shows that some DNA viruses have the same high rates of antigenic variation as their RNA counterparts.[15] Antigenic variation within viruses can be categories into 6 different ...
Many evolutionarily distant pathogenic organisms have evolved similar survival strategies to evade the immune responses of their hosts. These include antigenic variation, through which an infecting organism prevents clearance by periodically altering the identity of proteins that are visible to the immune system of the host1. Antigenic variation requires large reservoirs of immunologically diverse antigen genes, which are often generated through homologous recombination, as well as mechanisms to ensure the expression of one or very few antigens at any given time. Both homologous recombination and gene expression are affected by three-dimensional genome architecture and local DNA accessibility2,3. Factors that link three-dimensional genome architecture, local chromatin conformation and antigenic variation have, to our knowledge, not yet been identified in any organism. One of the major obstacles to studying the role of genome architecture in antigenic variation has been the highly repetitive ...
The immune response to is understood, but its extensive antigenic variability and resistance to check are thought to permit it to evade destruction from the hosts immune defenses. relationships during infectious disease are believed of as two-way reactions conventionally, that of the sponsor against the vice and pathogen versa, with the results dependent on which prevails ultimately. We suggest that should result in novel restorative strategies and facilitate fresh methods to vaccine advancement. Introduction The immune system response to gonorrhea, an specifically human std due to possesses a fantastic convenience of antigenic variation concerning the majority of its main surface constructions, including its lipooligosaccharide, pili, porin, and opacity (Opa) proteins, that are subject to different mechanisms of stage variant and recombinatorial gene manifestation, compounded by regular horizontal gene transfer (evaluated in research 3). Furthermore, utilizes several systems for inhibiting the ...
Respiratory infections constitute a major public health concern. The goal of this book is to share knowledge on the best advances in influenza and influenza-like viral infections, and new molecular-based diagnostic methods that discern the antigenic shift enabling viruses to constantly evolve and elude the host immune response. Co-infections, co-morbidities, persistently meager anti-flu vaccination coverage, and infection complications are dealt with. The chapters also further insight into such topics as the effects of sex hormones, and socioeconomic and anthropometric measures on respiratory and immune functions underlying the severity of asthma and respiratory allergy. Psychological functioning in respiratory disorders, taking into account quality of life, illness acceptance, and depressive symptoms is also reviewed as it is all too often underestimated by healthcare providers. The book is intended for clinicians, researchers, students, and all other actors in health-related issues.
Influenza A viruses circulate in humans, birds, and pigs. Occasionally, different influenza A viruses can infect a single host at the same time. This often happens in places where humans and animals live in close contact. The genetic material of the viruses gets mixed up, creating an entirely new virus. (This process is called antigenic shift or viral reassortment.) If the new virus makes people sick and is transmitted easily from person to person, an influenza pandemic can occur.. Thats what happened in the spring of 2009: the virus thats making the news right now has genes from flu viruses that normally circulate in pigs in Europe and Asia as well as avian (bird) and human genes.. ...
More Influenza Essay Topics.. In that year, H2N2 viruses circulated, followed by H3N8 in 1900, H1N1 in 1918, H2N2 in 1957, H3N2 in 1968, and H1N1 in 1977, with the latest antigenic shift being in 2009 with the H1N1 virus. This shows the emergence of the H1N1 strain of the virus was in 1918. The reason that these were major pandemics back then was because of the lack of treatments. The virus was unchecked as it spread throughout the population causing mass death. There are treatments available now that can alleviate the effects of the virus and save the lives of those infected by the swine flu.. The H1N1 virus cannot be treated by the use of antibiotics. Antibiotics are used to treat bacterial infections and issues and are therefore useless when fighting a virus. However there are ways to alleviate the pains that are caused by the virus. Common symptoms of the H1N1 virus include: body aches, cough, diarrhea, sore throat, vomiting, chills, fever, fatigue, runny nose and headaches. Common over the ...
this is the host shift of the influenza A H1N1...if you can see, there are a red line is a connection between human and pig, so you can think for yourselves about that. take a look at the antigenic shift, and then you will understand the virus better...this make no sense, but it will make a big change ...
AbstractBackgroundCovariation is an essential process that leads to coevolution of parts of proteins and genomes. In organisms subject to strong selective pressure, coevolution is central to keep the balance between the opposite requirements of antigenic variation and retention of functionality. Being the viral component most exposed to the external environment, the HIV-1 glycoprotein gp120 constitutes the main target of the immune response. Accordingly its more external portions are characterised by extensive sequence heterogeneity fostering constant antigenic variation.ResultsWe report that a single polymorphism, present at the level of the viral population in the conserved internal region C2, was sufficient to totally abolish Env functionality when introduced in an exogenous genetic context. The prominent defect of the non-functional protein is a block occurring after recognition of the co-receptor CCR5, likely due to an interference with the subsequent conformational changes that lead to membrane
The TWiPsters solve the case of the Brazilian Immigrant With Heart Problems, and describe how genome organization controls trypanosome antigenic variation.
The numerous cases which were treated showed a positive clinical response in greater or lesser degree. The earliest cases were studied intensively and were readied for publication.. The tumors that responded to a greater degree to our treatment, as was expected, are the ones with the greatest degree of undifferentiation; because of their antigenic characteristics and because of the greater degree of dissimilarity between them and the genotypes and antigenic characteristics of normal cells, they have more probability of eliciting an efficient immunologic response.. Histological studies which were made give us certain possible mechanisms of action which correlate with the clinical response obtained.. Microscopic studies showed the almost complete delimitation of the tumoral areas by connective-vascular structures which seem to have diverse morphologies according to their proximity to the tumor and the level of their chronological development, having at first a thick endothelial wall with ...
Despite a dramatic increase in our ability to catalogue variation among pathogen genomes, we have made far fewer advances in using this information to identify targets of protective immunity. Epidemiological models predict that strong immune selection can cause antigenic variants to structure into g …
Eosinophil Granule Proteins: Proteins found in EOSINOPHIL granules. They are primarily basic proteins that play a role in host defense and the proinflammatory actions of activated eosinophils.
Change in the Surface Antigen of a microorganism. There are two different types. One is a phenomenon, especially associated with Influenza Viruses, where they undergo spontaneous variation both as slow Antigenic drift and sudden emergence of new strains (Antigenic shift). The second type is when certain Parasites, especially trypanosomes, Plasmodium, and Borrelia, survive the immune response of the host by changing the surface coat (Antigen switching). (From Herbert et al., The Dictionary of Immunology, 4th ed ...
Influenza A virus can mutate in two ways: antigenic drift or adaptive mutation, whereby the existing antigen transformed and antigenic shift or mutation of the mating process of two or more kinds of antigens. Antigenic drift, causing a small mutations in the flu virus from year to year, which attacks the human immune system but not completely. In contrast, the new H1N1 strain emerged in a way antigenic shift in pigs in Mexico ...
Schistosomes have an outer tegument that protects them from the host immune system. Parasite antigens expressed on or within the surface layer of the tegument have been suggested to be potential vaccine targets such as tetraspanin 23 (TSP23). Little is known about the evolution and diversity of tegumental antigens, an important consideration given that vaccines are being designed and are failing. Moreover, these antigens, including TSP23, are in direct contact with the host immune system, and so accelerated and adaptive evolution may be occurring. Species of Schistosoma infect a variety of definitive hosts. The way in which these hosts are shaping the evolution of antigens across different species of Schistosoma needs investigating. Much attention has been focussed on the production of an effective multi-species vaccine against the schistosomes, and there has been little success in absolute clearance or even establishment of continued immune memory post-infection. The aim of this study was ...
TY - JOUR. T1 - Epidemics in Competition. T2 - Partial Cross-Immunity. AU - Andreasen, Viggo. PY - 2018. Y1 - 2018. N2 - The competition between two pathogen strains during the course of an epidemic represents a fundamental step in the early evolution of emerging diseases as well as in the antigenic drift process of influenza. The outcome of the competition, however, depends not only on the epidemic properties of the two strains but also on the timing and size of the introduction, characteristics that are poorly captured by deterministic mean-field epidemic models. We describe those aspects of the competition that can be determined from the mean-field models giving the range of possible final sizes of susceptible hosts and cumulated attack rates that could be observed after an epidemic with two cross-reacting strains. In the limit where the size of the initial infection goes to zero, the possible outcomes lie on a (one dimensional) curve in the outcome space.. AB - The competition between two ...
Brunham, R C, F A Plummer, and R S Stephens. Bacterial antigenic variation, host immune response, and pathogen-host coevolution.. Infection and Immunity 61.6 (1993): 2273-2276. Web. 19 Jan. 2020. ...
View Notes - 10-07_Culture_Exists_2 from ANTHRO 186P at UCLA. Culture exists Three sources of variation Much variation is not environmental Much variation not due to institutions w w Cultures
Pathogens that evade adaptive immunity typically exhibit antigenic variation. By contrast, it appears that although the chronic human tuberculosis (TB)-causing pathogen Mycobacterium tuberculosis needs to counter host T cell responses, its T cell epitopes are hyperconserved. Here we present an extensive analysis of the T cell epitopes of M. tuberculosis. We combined population genomics with experimental immunology to determine the number and identity of T cell epitope sequence variants in 216 phylogenetically diverse strains of M. tuberculosis. Antigen conservation is indeed a hallmark of M. tuberculosis. However, our analysis revealed a set of seven variable antigens that were immunogenic in subjects with active TB. These findings suggest that M. tuberculosis uses mechanisms other than antigenic variation to evade T cells. T cell epitopes that exhibit sequence variation may not be subject to the same evasion mechanisms, and hence vaccines that include such variable epitopes may be more ...
Antigenic variation by variant surface glycoprotein (VSG) coat switching in African trypanosomes is one of the most elaborate immune evasion strategies found among pathogens. Changes in the identity of the transcribed VSG gene, which is always flanked by 70-bp and telomeric repeats, can be achieved either by transcriptional or DNA recombination mechanisms. The major route of VSG switching is DNA recombination, which occurs in the bloodstream VSG expression site (ES), a multigenic site transcribed by RNA polymerase I. Recombinogenic VSG switching is frequently catalyzed by homologous recombination (HR), a reaction normally triggered by DNA breaks. However, a clear understanding of how such breaks arise-including whether there is a dedicated and ES-focused mechanism-is lacking. Here, we synthesize data emerging from recent studies that have proposed a range of mechanisms that could generate these breaks: action of a nuclease or nucleases; repetitive DNA, most notably the 70-bp repeats, providing ...
Trypanosoma brucei, a causative agent of African sleeping sickness in humans and nagana in animals, constantly changes its dense variant surface glycoprotein (VSG) coat to avoid elimination by the immune system of its mammalian host, using an extensive repertoire of dedicated genes. Although this process, referred to as antigenic variation, is the major mechanism of pathogenesis for T. brucei, the dynamics of VSG expression in T. brucei during an infection are poorly understood. In this thesis, I describe the development of VSG-seq, a method for quantitatively examining the diversity of expressed VSGs in any population of trypanosomes. Using VSG-seq, I monitored VSG expression dynamics in vivo during both acute and chronic mouse infections. My experiments revealed unexpected diversity within parasite populations, and the expression of as much as one-third of the functional genomic VSG repertoire after only one month of infection. In addition to suggesting that the host-pathogen interaction in T.
Plasmodium falciparum expresses on the host erythrocyte surface clonally variant antigens and ligands that mediate adherence to endothelial receptors. Both are central to pathogenesis, since they allow chronicity of infection and lead to concentration of infected erythrocytes in cerebral vessels. Here we show that expression of variant antigenic determinants is correlated with expression of individual members of a large, multigene family named var. Each var gene contains copies of a motif that has been previously shown to bind diverse host receptors; expression of a specific var gene correlated with binding to ICAM-1. Thus, our findings are consistent with the involvement of var genes in antigenic variation and binding to endothelium.
Research in the Totten group focuses on the molecular biology, pathogenesis, and disease associations of the recently discovered STD pathogen, Mycoplasma genitalium. Their finding that this bacterium can persist for months, if not years, in infected women lead to our hypothesis that this pathogen evades the host immune response in part by antigenically varying two of its immunogenic surface-exposed proteins. Supporting this hypothesis, they have shown that the sequences of the genes encoding these proteins evolve using reciprocal recombination with non-coding homologous DNA distributed throughout its minimal chromosome. Further, contrary to the accepted wisdom that this bacterium contains few regulatory genes, they have shown that recombination leading to antigenic variation is regulated at the transcriptional, post-transcriptional, and translational levels. The novel recombination and regulatory mechanisms of antigenic variation, the biologic significance of the resulting antigenic variants, ...
Neisseria meningitidis is the major cause of bacterial meningitis worldwide. The genome of this pathogen contains >40 phase variable loci whose expression is regulated by tandem DNA repeat tracts. Majority of these loci encode OMPs, which are potential targets for host innate and adaptive immune responses. An analysis for the distribution, frequency and role of PV of these genes is relevant in determining their virulence association and suitability as a future vaccine candidate. The project investigated the combined distribution, frequency and PV status of two important genes, hpuAB and hmbR, in disease (n=221) and carriage (n=305) isolates. Strains with both genes or only hmbR were present at similar frequencies among disease isolates as compared with carriage isolates. However, >90 % of isolates from CC5, CC8 and CC11 (CCs with the highest disease to carriage ratios) contained both genes. Strains with only hpuAB gene were under-represented among disease isolates, possibly due to the receptor ...
Vaccination against foot-and-mouth disease (FMD) represents an essential element in controlling and combating outbreaks, which can otherwise have disastrous consequences such as during the FMD outbreak in the UK in 2001. This is pertinent to regions in large parts of the developing world in which the FMD virus (FMDV) is endemic, as well as during an epidemic in FMDV-free areas such as Europe. Nevertheless, successful vaccination against FMDV requires selection of the appropriately matching vaccine strain providing protection against a particular circulating field virus. This problem originates from the existence of seven known serotypes of FMDV, with which a high antigenic variation of the virus is observed. In addition, subtypical antigenic variation within a serotype is under constant evolutionary change due to the high mutation rate of FMDV. For these reasons, continuous vaccine testing and modification in the light of recent antigenic changes to the virus is required. Traditionally, vaccines ...
darcoda at telerama.lm.com (S. Frog) wrote: , , , Hi, and all that. , , Im not sure if this is the proper place to raise this question, , and forgive me if it isnt, but I have a question about the flu. , Actually, three questions: , Is the flu a retrovirus? , If it isnt a retrovirus, do I have a faulty definition of what a , retrovirus is? , Lastly, is it true that the flu has only been around for like a , hunred years or so? And that it mutated from something else, which is , why human has so little resistence to it when the influenza epidemic , roared through just after world war I? , , , Thanks. :) , , , , , S. Frog , -- , , , .. The agent which causes many cases of the flu is called influenza. It is a member of the Orthomyxoviridae. These viruses have a segmented, single stranded RNA genome. Their segmented genome enables them to undergo a special kind of mutation (actually it is segment reassortment) called antigenic shift, which causes the pandemics in human medicine. Many species ...
Contingency genes are common in pathogenic microbes and enable, through pre-emptive mutational events, rapid, clonal switches in phenotype that are conducive to survival and proliferation in hosts. Antigenic variation, which is a highly successful survival strategy employed by eubacterial and eukaryotic pathogens, involves large repertoires of distinct contingency genes that are expressed differentially, enabling evasion of host acquired immunity. Most, but not all, antigenic variation systems make extensive use of subtelomeres. Study of model systems has shown that subtelomeres have unusual properties, including reversible silencing of genes mediated by proteins binding to the telomere, and engagement in ectopic recombination with other subtelomeres. There is a general theory that subtelomeric location confers a capacity for gene diversification through such recombination, although experimental evidence is that there is no increased mitotic recombination at such loci and that sequence ...
In addition to avoiding destruction by modulating DNA-Repair pathways, viruses also alter other aspects of the cells defense such as cell surface markers. CMV and adenoviruses decrease the expression of a cells MHC recognition markers which decreases the ability of the immune system to respond to infections that is highly characteristic of the immune system in senescence (DNA-Damage-Response np). One factor is the loss of the CD28 marker; when CD28 isnt expressed, antigen-presenting cells like macrophages no longer recognise the T cell and thus arent able to alert the immune cell to danger (de Grey 207). Some viruses like HIV are able to prevent detection from the immune system by restricting the expression of virus antigens as well as having wide antigen variation (DNA-damage-response). Furthermore, there are viruses that modify other signaling pathways that lead affects lymphocyte and macrophage (which is an anti-gen presenting cell) functions that lead to immunosupression ...
Then is this host specific antigenic variation due to different subspecies of P.carinii infecting their particular favorite flavor of host? Or is there one P.carinii changing its disguise to suit its situation (Like the elusive pimpernel)? Do the authors of this splendid sounding article offer an explanation? My library doesnt carry that journal. Doesnt carry much of anything not relating to engineering, actually. Regards Simon ______________________________ Reply Separator _________________________________ Subject: RE: Re[2]: P.carinii Author: [email protected] at Internet Date: 11/12/98 7:14 PM Host species-specific antigenic variations have been reported, according to the article I cited. Pigs are not dogs are not rats are not people! -----Original Message----- From: [email protected] [SMTP:[email protected]] Sent: Thursday, November 12, 1998 12:27 PM To: [email protected] Subject: Re[2]: P.carinii Forgive my stupidity, but wont any antibody to P.carinii label ...
A Mr 32,000 integral membrane protein has previously been identified on erythrocytes bearing the Rh(D) antigen and is thought to contain the antigenic variations responsible for the different Rh phenotypes. To study it on ...
There arent too many options if you want to root piles out completely. Perhaps in that context surgery is one of the best bets. But that too, there is no foolproof guarantee that you will never have it.
5/4/2009 10:24:08 PM Flu viruses change slightly from year to year. This is called antigenic drift. This is what the committee that determines what the
As with other infectious diseases, much discussion has been generated in the past about whether the malaria parasite population is structured into strains that have variable virulence (27). PfEMP1 presents us with a scenario in which a repertoire of molecules that play a central role in the host-parasite interaction, both through cytoadherence and immunogenicity, appear to be functionally and genetically differentiated within every parasite genome (13, 28), potentially giving each parasite line the ability to alter its pathogenicity depending on the combination of selection pressures experienced within the host (29). However, there is no direct evidence for links between the structure of the PfEMP1 antigen repertoire and a role for PfEMP1 in parasite immune evasion and pathogenicity.. A frequently cited study supporting a link between group A var expression and parasite virulence is based on the in vitro selection of a lab-adapted parasite isolate using pooled serum from semi-immune children ...
In malaria‐endemic areas, a nagging issue is the failure of naturally exposed individuals to develop sterile long‐lasting protective immunity. This may be due to several factors including the stage specificity of parasite antigen expression, the antigenic variability among field parasites, and the profound immune dysregulation caused by pre‐erythrocytic and erythrocytic stages (Renia & Goh, 2016; Scholzen & Sauerwein, 2016; Van Braeckel‐Budimir et al, 2016). These factors could also contribute to explain why despite tremendous investments and years of research, progress on the vaccination front has been only modest. Clinical efficacy of the most advanced subunit vaccine candidate against P. falciparum (RTS,S) is limited and quickly wanes over time (Olotu et al, 2016). Hopes are emerging from whole attenuated sporozoite vaccination strategies (Sissoko et al, 2017), but the disappointing RTS,S results combined with the fact that vaccine research on P. vivax is only beginning (Tham et al, ...
Human rhinoviruses (HRVs), a genus of the Picornaviridae family, are the most frequent etiological agents of common colds (Rueckert, 1996). Rhinoviruses are small, icosahedral viruses, with an average diameter of 300 Å and a molecular mass of ∼8.5 × 106 Da. They are composed of a protein shell that encapsidates a single, positive RNA strand of ∼7000 bases. The capsid is built from 60 copies each of four viral proteins. The three larger proteins, VP1, VP2 and VP3 (∼250 amino acids, 30 kDa each), form the external surface of the virus, whereas VP4 (70 amino acids, 6 kDa) is an internal protein located at the interface between the capsid and genome (Rossmann et al., 1985).. With ,100 different serotypes identified to date, HRVs exhibit remarkable antigenic variability. To produce infection, HRVs must first attach to a cellular receptor. The major group of HRVs, consisting of ∼90 serotypes, utilizes the cell surface glycoprotein, intercellular adhesion molecule‐1 (ICAM‐1), as its ...
Interested in discovering how trypanosomes undergo antigenic variation? If the answer is yes - we have a postdoctoral position available in the Trypanosome Molecular Biology group with Lucy Glover. In our group we study how the trypanosomes control expression of the variant surface glycoprotein from the fly to the mammalian host, and the the role of DNA repair and recombination in antigenic variation and immune evasion in African trypanosomes We are located in the Department of Parasites and Insect Vectors at the Institute Pasteur in Paris, which provides an excellent international scientific environment and state-of-the-art core facilities including high throughput sequencing, and imaging technologies.. ...
Author Summary The molecular evolution of any organism is described by changes in the genotype resulting from genetic drift or selection to maintain or establish fitness under the given environmental conditions. Identification of phenotype-defining changes and their distinction from (near-) neutral (hitchhikers) ones is a fundamental challenge in genome research. The standard approach involves time- and cost-intensive mutation experiments, which are typically low throughput, due to their experimental nature. We have developed a computational method for the inference of phenotypic impact of genotypic changes that is applicable to any system, within or across species, where homologous genetic sequences and associated pairwise phenotype distances are available. We demonstrate the accuracy of our method by application to the human influenza A (H3N2) virus. This exemplary system is of particular interest, as recognizing changes in the antigenic phenotype and a viral strains capability to evade pre
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The primary focus of the Montelaro lab is to elucidate the intricate interactions between viral pathogens and host immune responses to determine the mechanisms by with host immunity contributes to protection and disease and to serve as a basis for the development of effective vaccines. A particular interest of the lab is to develop effective strategies to overcome the challenge of natural viral antigenic variation that has evolved as a common complication to the development of effective vaccines to important viral diseases, including those related to biodefense and emerging infectious diseases. Systems currently under investigation include HIV-1 and related animal lentiviruses (SHIV, SIV, and EIAV). Studies in these systems include investigation of the nature and role of antigenic variation during infection, the development of novel assays to characterize virus-specific innate, humoral, and cellular immune responses, and the design of engineered immunogens for effective vaccination against ...
A novel strategy to predict the antigenic evolution of circulating influenza viruses and more precisely anticipate seasonal flu strains has been developed.
Behavior of Laterally Loaded Piles: I-Single Piles. An analysis is presented for the horizontal displacement and rotation of a vertical pile subjected to lateral loading and moment, and situated in an ideal elastic mass. Influence factors are presented for a wide range of pile flexibilities and length-to-diameter ratios, for both free-head and fixed-head piles. Comparisons between the elastic solutions and the corresponding solutions obtained from the subgrade reaction theory show that the latter considerably overestimates the displacement and rotation of the pile, but gives a reasonable estimate of the moments in the pile. The elastic analysis is extended to include the effect of local yield between the soil and the pile; the load-displacement relationship for relatively flexible piles is found to be markedly influenced by local yield. The characteristics of behavior indicated by the theoretical solutions agree reasonably well with those reported from measurements on full-scale piles.
Yet crucial advances in toxicology also occurred within other NIH laboratories, led during pioneers such as Bernard Brodie and Julius Axelrod and later continued at hand investigators such as JR Mitchell, D Jollow and JR Gillette. There are assorted institutes all across the world, which gather genome data, for benchmark, to discover why united treatment in regard to a genetic malady helps one untiring, but shows no or less to all intents on another. This substance inferior intimacy, lower communications, and much fights discount dapoxetine 90mg with mastercard erectile dysfunction at age 25. J Biol Chem 270:7241В-7250 Prucca CG, Slavin I, Quiroga R, Elias EV, Rivero FD, Saura A, Carranza PG, Luj?n HD (2008) Antigenic variation in Giardia lamblia is regulated by RNA interference. As infants fit more expressive, they jeopardy wound from falls down stairs and afar chairs, tables, and other structures. Its an surprising process, this on-going detoxification of your consistency order cialis 10mg ...
Problems & Puzzles: Puzzles Puzzle 92. A pile of prime-spheres Days ago my friend Enoch Haga and me starting puzzling each other to construct a pile of balls (a tetrahedron) with the following properties: a) every ball contains a distinct prime, b) each prime-ball must be the sum of the prime numbers contained in the three balls from the immediate inferior level and in contact with the mentioned prime-ball. Can you imagine a pile of balls? A new friend of these pages, Chuck Henry, kindly and quickly provided several beautiful photos generated by him that should help to visualize a pile of balls like the one we are talking about. Please click here 1 and here 2 (*). Question: Get the least solution for a pile of n levels, for n=5, 6 & 7. ...
M. Soriani, P. Petit, R. Grifantini, R. Petracca, G. Gancitano, E. Frigimelica, F. Nardelli, C. Garcia, S. Spinelli, G. Scarabelli, S. Fiorucci, R. Affentranger, M. Ferrer-Navarro, M. Zacharias, G. Colombo, L. Vuillard, X. Daura and G. Grandi. Exploiting antigenic diversity for vaccines design : the Chlamydia ArtJ paradigm. J. Biol. Chem, 2010, 285, 30126-30138. ...
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The MOVAX side grip pile driver is based on MOVAXs Modular System and thus capable of handling a wide variety of piles [linkki]. In order to select the correct arms, clamps and pads information is needed about the main type of piles to be driven, but also whether there is a need to drive also other type of piles, now or in the future ...
Scherf, Artur; Lopez-Rubio, Jose Juan; Riviere, Loïc (October 2008). "Antigenic Variation in Plasmodium falciparum". Annual ... Guizetti, Julien; Scherf, Artur (May 2013). "Silence, activate, poise and switch! Mechanisms of antigenic variation in". ... Cross, George A. M. (April 1996). "Antigenic variation in trypansosomes: Secrets surface slowly". BioEssays. 18 (4): 283-291. ... "The large diverse gene family var encodes proteins involved in cytoadherence and antigenic variation of plasmodium falciparum- ...
Thirteen years of his group's malaria research on antigenic variation in malaria culminated in the first molecular cloning of ... Howard, R. J.; Barnwell, J. W.; Kao, V. (1 July 1983). "Antigenic variation of Plasmodium knowlesi malaria: identification of ... Howard, RJ (13 November 1984). "Antigenic variation of bloodstage malaria parasites". Philosophical Transactions of the Royal ... to the molecular pathogenesis of human cerebral malaria and the role of parasite antigenic variation and infected cell ...
Important questions about antigenic variation are also relevant for such research areas as developing a vaccine against HIV and ... Antigenic variation is common among pathogenic organisms. These include the agents of malaria, gonorrhea, and sleeping sickness ... through antigenic variation. Essentially, the pathogen stays one step ahead of antibodies by changing its surface proteins. ... which is sufficient to create a new antigenic "identity" for the organism. Antibodies in the blood that are binding to and ...
Harrison B & Robinson D (1999). Natural genomic and antigenic variation in whitefly-transmitted geminiviruses (begomoviruses). ... There is variation in the literature on this score, however, with other sources citing a 4-hour acquisition time and 4-hour ... Little to no infection occurs after three months, and variation in spread was due to change in temperature, radiation and ...
Morrison LJ, Marcello L, McCulloch R; Marcello; McCulloch (December 2009). "Antigenic variation in the African trypanosome: ...
Antigenic variation prevents the development of cross immunity to the various strains of O. tsutsugamushi. An infected ... As of 2009, more than 20 different strains have been established in humans based on antigenic variation using serological tests ... "Demonstration of antigenic and genotypic variation in Orientia tsutsugamushi which were isolated in Japan, and their ... DNA analyses have shown that the GroES and GroEL genes are indeed present in O. tsutsugamushi with slight variation in ...
Enormous antigenic variation in Orientia tsutsugamushi strains is now recognized, and immunity to one strain does not confer ... A vaccine developed for one locality may not be protective in another, because of antigenic variation. This complexity ... 2003). "Short report: variation in the 56-kD type-specific antigen gene of Orientia tsutsugamushi isolated from patients in ... Kang JS, Chang WH (1999). "Antigenic relationship among the eight prototype and new serotype strains of Orientia tsutsugamushi ...
Vickerman was the one who made the discovery that antigenic variation could occur in eukaryotic cells, namely in protozoa. Cox ...
... complexity allows the parasite to constantly change its surface and thus evade the immune system through antigenic variation. ... Variation in complexity can be described by 2Neu, where Ne is effective population size and u is mutation rate. In this ... When comparing variation in complexity in organelles, effective population size is replaced with genetic effective population ... is a positive correlation between genome size and noncoding DNA genome content with each group staying within some variation. ...
The serotype and antigenic variations of the virus can only be distinguished between through virus-neutralization assays. The ... The high degree of antigenic variation is due to a combination of high mutation rate and inter-strain homologous recombination ... study reveal different antigenic IBDV strains prevalent in southern China during the years 2000-2017 and also the antigenic ... project domains can be viewed to see the variation of the virus through amino acid substitutions. The genome is typically ...
This process, called antigenic variation, allows the spirochaete to evade the host's immune response and cause relapsing ...
Glycosylation seems to play a structural role in the concealment and variation of antigenic sites necessary for the host to ... Classification of members of this taxon is infrequently based on their antigenic properties. Symptoms and host range: The virus ...
Drift can refer to genetic drift or antigenic drift. Mutation and selection for the most advantageous variation of the virus ... Antigenic mutants can evolve quickly due to the high mutation rate in viruses. The cause of the antigenic drift lies in the ... These changes allow for almost endless possibilities for new viral strains to arise and it is the antigenic drift of the HA and ... There have been three occurrences of pandemics caused by antigenic shift since 1900, and it could just as easily happen again. ...
Development of a vaccine has been complicated by the ongoing evolution of resistant strains and antigenic variation (the ...
Papavasiliou most recently branched out to studying mechanisms of antigenic variation-or how pathogens vary their surface ...
His research initiated in Kenya continued for more than forty years and focused on understanding antigenic variation and immune ...
Various mechanisms of mutation in pathogenic microbes, e.g., mechanisms for phase variation and antigenic variation, appear to ... Phenotypic variation may show biases (see Developmental bias) STR loci may exhibit biases to expand or contract In mammals and ... Mutation Rate Variation and Organelle Genome Evolution in the Angiosperm Genus Silene (Thesis). University of Virginia. doi: ... A mutation is a heritable variation in the genetic information of a short region of DNA sequences. Mutations can be categorized ...
... antigenic variation MeSH G13.920.331 - genetic heterogeneity MeSH G13.920.590 - mutation MeSH G13.920.590.029 - allelic ...
... cell-mediated cytotoxicity Antibody-dependent enhancement Antigen Antigen presentation Antigen processing Antigenic variation ... M Oncostatin M receptor Opportunistic infection Oprelvekin Opsonin Organ harvesting Organ transplantation Original antigenic ...
Variations in these factors could lead to different strengths of immune response toward the newly formed antigenic determinant ...
Many of the proteins known to show antigenic or phase variation are related to virulence. Antigenic variation in bacteria is ... shows that some DNA viruses have the same high rates of antigenic variation as their RNA counterparts. Antigenic variation ... making it one of the mechanisms of antigenic escape. It is related to phase variation. Antigenic variation not only enables the ... Antigenic variation may be classified into two types, antigenic drift that results from a change in few amino acids and ...
van der Woude MW, Bäumler AJ (2004). "Phase and antigenic variation in bacteria". Clin Microbiol Rev. 17 (3): 581-611. doi: ... Wisniewski-Dyé F, Vial L (2008). "Phase and antigenic variation mediated by genome modifications". Antonie van Leeuwenhoek. 94 ... It involves the variation of protein expression, frequently in an on-off fashion, within different parts of a bacterial ... In this form of phase variation. The promoter region of the genome can move from one copy of a gene to another through ...
"Antigenic variation in the African trypanosome: molecular mechanisms and phenotypic complexity". Cell. Microbiol. 11 (12): 1724 ...
... complexity allows the parasite to constantly change its surface and thus evade the immune system through antigenic variation.[ ...
"Antigenic variation in trypanosomes: enhanced phenotypic variation in a eukaryotic parasite", 2001 ... "The rate of antigenic variation in fly-transmitted and syringe-passaged infections of Trypanosoma brucei", 1997 ... of the VSG gene silent archive in Trypanosoma brucei reveals that mosaic gene expression is prominent in antigenic variation ...
Not to be confused with Antigenic shift or Genetic drift.. Antigenic drift is a mechanism for variation in viruses that ... Two processes drive the antigens to change: antigenic drift[1][2] and antigenic shift, antigenic drift being the more common. ... Antigenic drift should not be confused with antigenic shift, which refers to reassortment of the virus' gene segments. As well ... Antigenic shift. Notes[edit]. *^ D. J. D. Earn; J. Dushoff; S. A. Levin (2002). "Ecology and Evolution of the Flu". Trends in ...
Each specific known genetic variation is traceable to a virus isolate of a specific case of infection. Through antigenic drift ... "Antigenic and genetic characteristics of H5N1 viruses and candidate H5N1 vaccine viruses developed for potential use as pre- ... Asian lineage HPAI A(H5N1) is divided into two antigenic clades. "Clade 1 includes human and bird isolates from Vietnam, ... HA codes for hemagglutinin, an antigenic glycoprotein found on the surface of the influenza viruses and is responsible for ...
Also homologous recombination occurs in viral genes, suggesting that genetic variation generated by homologous recombination ... which can cause an antigenic shift to a new influenza A virus subtype which most people have little to no immune protection ... The evolution of avian influenza virus has been influenced by genetic variation in the virus population due to genome segment ... and influenza virus epidemics are associated with changes in its antigenic structure. This was originally derived from pigs, ...
These cells have T-cell receptors and CD4 molecules that, in combination, bind antigenic peptides presented on major ...
Cotterman in 1956 in his seminal paper on antigenic variation.[11] ...
Antigenic variation. *Hapten. *Epitope *Linear. *Conformational. *Mimotope. *Antigen presentation/professional APCs: Dendritic ...
These variations in specificity are the result of interatomic contacts with local residues near the active sites of each ... "26S proteasomes and immunoproteasomes produce mainly N-extended versions of an antigenic peptide". The EMBO Journal. 20 (10): ...
Antigenic specificity[edit]. Antigenic specificity is the ability of the host cells to recognize an antigen specifically as a ... Epitope - The distinct surface features of an antigen, its antigenic determinant. Antigenic molecules, normally "large" ... Lipids and nucleic acids are antigenic only when combined with proteins and polysaccharides.[citation needed] Non-microbial non ... A hapten is a small molecule that changes the structure of an antigenic epitope. In order to induce an immune response, it ...
WHO (PDF) contains latest Evolutionary "Tree of Life" for H5N1 article Antigenic and genetic characteristics of H5N1 viruses ... Suzuki Y (March 2005). "Sialobiology of influenza: molecular mechanism of host range variation of influenza viruses". ... However, influenza B mutates enough that lasting immunity is not possible.[53] This reduced rate of antigenic change, combined ... This is called antigenic drift, which slowly creates an increasing variety of strains until one evolves that can infect people ...
Other formulas, based on free amino acids, are the least antigenic and provide complete nutritional support in severe forms of ... However, for the soybean proteins known to trigger allergic reactions, there is more variation from strain to strain than ... Hypoallergenic infant formulas can be based on proteins partially predigested to a less antigenic form. ... especially as there can be many variations on the wording of the warning.[108][109] As of 2014[update], PAL is regulated only ...
Glenny A, Pope C, Waddington H, Wallace U (1926). "The antigenic value of toxoid precipitated by potassium alum". J Pathol ... In the early days of vaccine manufacture, significant variations in the efficacy of different batches of the same vaccine were ... Because immune systems have evolved to recognize these specific antigenic moieties, the presence of an adjuvant in conjunction ...
"Predicting the Antigenic Structure of the Pandemic (H1N1) 2009 Influenza Virus Hemagglutinin". PLoS ONE. 5 (1): e8553. Bibcode: ... Preliminary research suggests that severity is linked to a genetic variation in immune systems. From April 2009 to November ...
These variations enable the immune system to respond to a very wide variety of invaders, but may also give rise to lymphocytes ... Idiotype Cross-Reaction - Idiotypes are antigenic epitopes found in the antigen-binding portion (Fab) of the immunoglobulin ...
A key conclusion of the paper is that 85.4% of the total genetic variation observed occurred within each group. That is, he ... This therefore gives a decreased chance that any particular pathogen will not be recognised, and means that more antigenic ... Genetic variation at an overdominant locus is expected to be maintained by balancing selection. The high fitness of ... "Gamete fertility and ovule number variation in selfed reciprocal F1 hybrid triploid plants are heritable and display epigenetic ...
Antigenic sensitivity[edit]. Various antigenic triggers have been implicated as a trigger, including L forms of streptococci, ... There have been reports of ethnic variation. For example, in the United States, aphthous stomatitis may be three times more ... decrease of the mucosal barrier and states of heightened antigenic sensitivity (see below).[5] Risk factors in aphthous ...
Those domains can be alternatively spliced reaching high numbers of variations.[19] It was shown that after exposure to ... or antigenic determinants. Most antigens contain a variety of epitopes and can stimulate the production of antibodies, specific ... the unique set of antigenic determinants of the variable portion of an antibody) and 'anti-idiotypes' (antigen receptors that ...
Honjo T, Habu S (1985). "Origin of immune diversity: genetic variation and selection". Annu Rev Biochem. 54 (1): 803-830. doi: ... but with the ability to produce the effector function appropriate for each antigenic challenge. Class switching is triggered by ... the resulting complex or hapten-carrier adduct is antigenic. ...
A stochastic model is a tool for estimating probability distributions of potential outcomes by allowing for random variation in ... antigenic shift. *phylodynamics. *pathogen population genetics. *evolution and spread of resistance. *role of host genetic ... Stochastic models depend on the chance variations in risk of exposure, disease and other illness dynamics. ...
Role of allelic variation[edit]. Studies of humans and animals imply a heterozygous selection mechanism operating on these loci ... The other MHC class II proteins, DM and DO, are used in the internal processing of antigens, loading the antigenic peptides ... It may also recognize cells that A23 and A24 miss because of small variations. A23 and A24 are split antigens, but antibodies ... There are issues that limit this variation. Certain alleles like DQA1*05:01 and DQA1*05:05 encode proteins with identically ...
Genetic variations in MYH9 may be involved in predisposition to chronic kidney disease (CKD). A haplotype of MYH9 (haplotype E1 ... Accurate definition of the antigenic site around the disulphide bridge 30-115 (site 3) by 'surface-simulation' synthesis". The ... The disease has been reported worldwide and there is no evidence of variation in prevalence across ethnic populations.[42] ... "African ancestry allelic variation at the MYH9 gene contributes to increased susceptibility to non-diabetic end-stage kidney ...
2009). "Genetic variation in IL28B predicts hepatitis C treatment-induced viral clearance". Nature. 461 (7262): 399-401. ... It appears to be antigenic but its function is unknown. Replication[edit]. ... Kato N, Ueda Y, Sejima H, Gu W, Satoh S, Dansako H, Ikeda M, Shimotohno K (2019) Study of multiple genetic variations caused by ... Kato N (2000). "Genome of human hepatitis C virus (HCV): gene organization, sequence diversity, and variation". Microb. Comp. ...
The evolution of avian influenza virus has been influenced by genetic variation in the virus population due to genome segment ... which can cause an antigenic shift to a new influenza A virus subtype which most people have little to no immune protection ... Also homologous recombination occurs in viral genes, suggesting that genetic variation generated by homologous recombination ... and influenza virus epidemics are associated with changes in its antigenic structure. This was originally derived from pigs, ...
Antigenic variation. *Hapten. *Epitope *Linear. *Conformational. *Mimotope. *Antigen presentation/Professional APCs: Dendritic ...
positive regulation of acute inflammatory response to antigenic stimulus. • learning or memory. • nociception. • negative ... effects of N1 substituted indole side chain variations on CB(2) cannabinoid receptor activity". Journal of Medicinal Chemistry ...
The virus is divided into four major serotypes (adr, adw, ayr, ayw) based on antigenic epitopes presented on its envelope ... "Clinical relevance and public health significance of hepatitis B virus genomic variations". World Journal of Gastroenterology ...
Crossing over also accounts for genetic variation, because due to the swapping of genetic material during crossing over, the ... "Variation in crossover frequencies perturb crossover assurance without affecting meiotic chromosome segregation in ...
WHO (PDF) contains latest Evolutionary "Tree of Life" for H5N1 article Antigenic and genetic characteristics of H5N1 viruses ... "Sialobiology of influenza: molecular mechanism of host range variation of influenza viruses". Biol Pharm Bull. 28 (3): 399-408 ... Hal ini disebut antigenic drift, yang secara perlahan menimbulkan banyak variasi galur sampai salah satu dapat menginfeksi ... "Antigenic and genetic characterization of influenza C viruses which caused two outbreaks in Yamagata City, Japan, in 1996 and ...
However, influenza B mutates enough that lasting immunity is not possible.[26] This reduced rate of antigenic change, combined ... Further variation exists; thus, specific influenza strain isolates are identified by a standard nomenclature specifying virus ... The four genera of Influenza virus, which are identified by antigenic differences in their nucleoprotein and matrix protein, ... Suzuki Y (March 2005). "Sialobiology of influenza: molecular mechanism of host range variation of influenza viruses". ...
Variations[edit]. DNA oncoviruses typically cause cancer by inactivating p53 and Rb, thereby allowing unregulated cell division ...
This displaces the antigenic peptide away from the TCR and circumvents the normal mechanism for T-cell activation.[5][11] ... "Conservation and variation in superantigen structure and activity highlighted by the three-dimensional structures of two new ... 2003). "Identification of the Antigenic Epitopes in Staphylococcal Enterotoxins A and E and Design of a Superantigen for Human ... "High-frequency intracellular infection and erythrogenic toxin A expression undergo phase variation in M1 group A streptococci" ...
Many of the proteins known to show antigenic or phase variation are related to virulence. Antigenic variation in bacteria is ... shows that some DNA viruses have the same high rates of antigenic variation as their RNA counterparts. Antigenic variation ... making it one of the mechanisms of antigenic escape. It is related to phase variation. Antigenic variation not only enables the ... Antigenic variation may be classified into two types, antigenic drift that results from a change in few amino acids and ...
Find out information about antigenic variation. Alteration of an antigen on the surface of a microorganism; may enable a ... pathogenic mocroorganism to evade destruction by the hosts immune system Explanation of antigenic variation ... antigenic variation. Also found in: Dictionary, Thesaurus, Medical, Legal, Wikipedia. antigenic variation. [‚an·tə¦jen·ik ‚ver· ... Antigenic divergence suggested by correlation between antigenic variation and pulsed-field gel electrophoresis profiles of ...
... and describe how genome organization controls trypanosome antigenic variation. ... antigenic variation, Chagas disease, chromatin, chromosome conformation capture, Hi-C, histone, nucleosome, parasite, ... and describe how genome organization controls trypanosome antigenic variation.. Hosts: Vincent Racaniello, Dickson Despommier, ...
... an specifically human std due to possesses a fantastic convenience of antigenic variation concerning the majority of its main ... The immune response to is understood, but its extensive antigenic variability. June 1, 2017. Sherri Kuhn Leave a comment ... The immune response to is understood, but its extensive antigenic variability and resistance to check are thought to permit it ... continuous adjustments in antigenic framework coupled with level of resistance to a significant bacteriolytic and ...
Source for information on antigenic variation: A Dictionary of Biology dictionary. ... antigenic variation The ability of certain pathogenic microorganisms, particularly viruses, to alter the antigens on their ... Continuous Variation , Skip to main content continuous variation Variation , Variation refers to the degree of dispersion, ... It is contrasted with… Coefficient Of Variation , coefficient of variation A measure of variability within a sample, ...
Immunogenetic mechanisms driving norovirus GII.4 antigenic variation.. Lindesmith LC1, Beltramello M, Donaldson EF, Corti D, ... Moreover, these data support the hypothesis that GII.4 norovirus evolution is heavily influenced by antigenic variation of ... Panel A: Amino acid variation of Epitopes A-E by GII.4 strain. Panel B: Predicted epitopes were expanded to include interacting ... To test if antigenic drift may contribute to GII.4 persistence, human memory B cells were immortalized and the resulting human ...
Cytomegalovirus (CMV) Vaccines: Reinfection and Antigenic Variation (CMV). The safety and scientific validity of this study is ...
Antigenic variation is the means by which a number of highly pathogenic microorganisms, ranging from the electronmicroscopic ... Antigenic Variation in Microbial Evasion of Immune Responses. Girish J Kotwal, University of Medicine and Health Sciences, St. ... Antigenic variation is the means by which a number of highly pathogenic microorganisms, ranging from the electronmicroscopic ... Antigenic variation is exhibited by a number of highly pathogenic microorganisms including human viruses, bacteria, fungi and ...
Chick Embryo Antigenic Variation Avian Myeloblastosis Virus Chick Embryo Fibroblast This work was done while the author was at ... Antigenic variation of the Avian Myeloblastosis Virus obtained from chick embryo fibroblasts. ...
Genetic basis of Neisseria gonorrhoeae lipooligosaccharide antigenic variation.. R J Danaher, J C Levin, D Arking, C L Burch, R ... Genetic basis of Neisseria gonorrhoeae lipooligosaccharide antigenic variation.. R J Danaher, J C Levin, D Arking, C L Burch, R ... Genetic basis of Neisseria gonorrhoeae lipooligosaccharide antigenic variation.. R J Danaher, J C Levin, D Arking, C L Burch, R ... Genetic basis of Neisseria gonorrhoeae lipooligosaccharide antigenic variation. Message Subject (Your Name) has forwarded a ...
It is now clear that antigenic variation in T. brucei can be largely, if not entirely, explained by the sequential expression ... It seems likely that similar groups of glycoproteins are responsible for antigenic variation in other salivarian trypanosome ... and improved diagnosis of the African trypanosomiases in the light of an increased understanding of antigenic variation. ... Antigenic variation in trypanosomes has been the subject of several recent and comprehensive reviews. The substance of my own ...
Effects of recA Mutations on Pilus Antigenic Variation and Phase Transitions in Neisseria gonorrhoeae. Michael Koomey, Emil C. ... Effects of recA Mutations on Pilus Antigenic Variation and Phase Transitions in Neisseria gonorrhoeae. Michael Koomey, Emil C. ... Effects of recA Mutations on Pilus Antigenic Variation and Phase Transitions in Neisseria gonorrhoeae. Michael Koomey, Emil C. ... Effects of recA Mutations on Pilus Antigenic Variation and Phase Transitions in Neisseria gonorrhoeae ...
... pilin antigenic variation as measured by the colony-based PCR assay, pilus-based colony morphology phase variation, growth, DNA ... Second, pilin antigenic variation occurs at a high frequency of ,10−2 pilE variants per total pilE (Serkin and Seifert 1998). ... 1986 Antigenic variation of gonococcal pilus involves assembly of separated silent gene segments. Proc. Natl. Acad. Sci. USA 83 ... The role that RdgC plays in pilin antigenic variation is less obvious than the role of RecA, RecO, or RecQ, which are likely ...
These pathogens use antigenic variation to prolong their circulation in the blood and thus increase the likelihood of ... Antigenic variation poses a challenge in the development of vaccines against vector-borne pathogens. ... bacterial and protozoal vector-borne pathogens have acquired similar genetic mechanisms for successful antigenic variation. ... Antigenic Variation in Vector-Borne Pathogens On This Page What is antigenic variation? Common elements Relapsing Fever ...
One of the best-studied antigenic variation systems is the pilin antigenic variation system of the pathogenic Neisseria, ... Determination of the donor silent-copy contribution to pilin antigenic variation.During Gc pilin antigenic variation, silent ... can undergo antigenic variation. In this study, Roche 454 pyrosequencing was used to examine the pilin antigenic variation of ... and is also essential for pilin antigenic variation (13, 19). Other factors involved in pilin antigenic variation include RecX ...
One of the most widely used strategies of immune evasion is antigenic variation, in which immunogenic molecules expressed on ... Microbial antigenic variation mediated by homologous DNA recombination FEMS Microbiol Rev. 2012 Sep;36(5):917-48. doi: 10.1111/ ... In most cases, antigenic variation is caused by genetic processes that lead to the modification of the amino acid sequence of a ... Here, we will review antigenic variation systems that rely on homologous DNA recombination and that are found in a wide range ...
Antigenic variation andimmunity to Plasmodium knowlesi: antibodies which induce antigenic variation and antibodies which ... Immunity to challenge and antigenic variation in P. knowlesi. Trans. R. Soc. Trop. Med. Hyg. 63: 507-523.PubMedCrossRefGoogle ... Antigenic variation and protective immunity in Plasmodium knowlesi malaria. Immunology 23: 503-521.PubMedGoogle Scholar ... Protective Immunity Antigenic Variation Blood Parasite Plasmodium Berghei Rodent Malaria These keywords were added by machine ...
Antigenic variation in Babesia bovis occurs through segmental gene conversion of the ves multigene family, within a ... Antigenic variation in Babesia bovis is one aspect of a multifunctional virulence/survival mechanism mediated by the ... We provide compelling evidence that variation of both transcriptionally active genes occurs through a mechanism of segmental ...
In vivo antigenic variation of Campylobacter flagellin.. S M Logan, P Guerry, D M Rollins, D H Burr, T J Trust ... In vivo antigenic variation of Campylobacter flagellin. Message Subject (Your Name) has forwarded a page to you from Infection ... Campylobacter coli VC167 cells producing either antigenic phase 1 (P1) or phase 2 (P2) flagellins (as determined by ...
... revealing antigenic drift and decreased antibody response against the vaccine strain in vaccinated chickens. ... Antigenic Variation of Avian Influenza A(H5N6) Viruses, Guangdong Province, China, 2014-2018 On This Page ... Antigenic Variation of Avian Influenza A(H5N6) Viruses, Guangdong Province, China, 2014-2018. Emerging Infectious Diseases. ... Bai, R., Sikkema, R. S., Li, C., Munnink, B. B., Wu, J., Zou, L....Ke, C. (2019). Antigenic Variation of Avian Influenza A(H5N6 ...
parasite, trypanosome, antigenic variation, immune evasion. Subjects:. Q Science , QH Natural history. Q Science , QH Natural ... Hall, James Peter John (2012) Mosaic VSGs in Trypanosoma brucei antigenic variation. PhD thesis, University of Glasgow. ... Segmental gene conversion was therefore found to be both prominent in chronic African trypanosome antigenic variation, and ... trypanosomes-deadly parasites of humans and livestock in tropical Africa-possess a comprehensive system of antigenic variation ...
... have been used to study the chemistry of antigenic variation within the present subtype of influenza A virus.... ... Single-step antigenic mutants, derived experimentally from the strain A/NT60/68 (H3N2), ... Thus, variation within a hierarchic series of antigenic mutants is associated with minor changes in the primary structure of ... Antigenic Variation Guanidine Hydrochloride Hemagglutinating Activity Sucrose Density Gradient Centrifugation Influenza Virus ...
Other work has begun to look at antigenic variation in animal-infective trypanosomes, and we will compare the findings that are ... This chapter will discuss the implications of such VSG diversity for immune evasion by antigenic variation, and will consider ... The essential features of trypanosome antigenic variation have been understood for many years and comprise a dense, protective ... Most studies of trypanosome antigenic variation have focused on T. brucei, the causative agent of human sleeping sickness. ...
Investigation of the distribution, antigenic variation and the biological role of phase variation of the haemoglobin receptors ...
... of sequence diversity in the Moraxella catarrhalis UspA2/UspA2H head domain on vitronectin binding and antigenic variation.. Su ... Vitronectin binding to isolates having UspA2 did not correlate to variation in the NTER2 motifs but occurred in UspA2H ... Vitronectin binding to isolates having UspA2 did not correlate to variation in the NTER2 motifs but occurred in UspA2H ... of sequence diversity in the Moraxella catarrhalis UspA2/UspA2H head domain on vitronectin binding and antigenic variation.}, ...
... pneumoniae leads to replacement of gene fragments that likely indicates the action of an antigen variation mechanism. Members ... Antigenic variation via inversions of short genomic fragments was shown to play a significant role for the S. pneumoniae ... Genomic rearrangements and antigenic variation of histidine triad protein PhtD. An important mode of genome evolution is ... Shelyakin, P., Bochkareva, O., Karan, A. et al. Micro-evolution of three Streptococcus species: selection, antigenic variation ...
First, the process of antigenic variation in the African trypanosomes and second the structure and function of the kinetoplast ... Hajduk, Stephen Louis (1980) Studies on trypanosomatid flagellates with special reference to antigenic variation and ... Studies on trypanosomatid flagellates with special reference to antigenic variation and kinetoplast DNA ...
Antigenic differences exist between groups, with loss of reactivity of some MAbs overtime, which are associated with aminoacid ... Molecular evolution and antigenic variation of European brown hare syndrome virus (EBHSV) Ana Lopes 1, 2, 3 Lorenzo Capucci 4 ... Molecular evolution and antigenic variation of European brown hare syndrome virus (EBHSV). Virology, Elsevier, 2014, 468-470, ... Antigenic differences exist between groups, with loss of reactivity of some MAbs overtime, which are associated with aminoacid ...
Molecular basis of size and antigenic variation of a Mycoplasma hominis adhesin encoded by divergent vaa genes.. Q Zhang, K S ... Size variation and C-terminal antigenic divergence of Vaa could affect the adherence of M. hominis and evasion of antibody- ... Molecular basis of size and antigenic variation of a Mycoplasma hominis adhesin encoded by divergent vaa genes. ... Molecular basis of size and antigenic variation of a Mycoplasma hominis adhesin encoded by divergent vaa genes. ...
2014) Antigenic variation of foot-and-mouth disease virus serotype A. J Gen Virol, 95 (Pt 2). pp. 384-392. ... Here, we used antigenic cartography to quantify and visualize the antigenic relationships among FMD serotype A viruses, aiming ... Nevertheless, by comparing antigenic distances measured from the antigenic maps with the full capsid (P1) sequence, we ... Furthermore, inherent variation among vaccine sera may impair reproducibility of one-way relationship scores. ...
Antigenic variation by variant surface glycoprotein (VSG) coat switching in African trypanosomes is one of the most elaborate ... Challenging trypanosome antigenic variation paradigms using natural systems. Richard McCulloch. Wellcome Trust (WELLCOTR). ... Evaluation of mechanisms that may generate DNA lesions triggering antigenic variation in African trypanosomes ... Evaluation of mechanisms that may generate DNA lesions triggering antigenic variation in African trypanosomes. PLoS Pathogens, ...
  • Antigenic variation not only enables the pathogen to avoid the immune response in its current host, but also allows re-infection of previously infected hosts. (wikipedia.org)
  • Antigenic variation or antigenic alteration refers to the mechanism by which an infectious agent such as a protozoan, bacterium or virus alters the proteins or carbohydrates on its surface and thus avoids a host immune response, making it one of the mechanisms of antigenic escape. (wikipedia.org)
  • Antigenic variation can occur by altering a variety of surface molecules including proteins and carbohydrates. (wikipedia.org)
  • Antigenic variation is employed by a number of different protozoan parasites. (wikipedia.org)
  • Antigenic variation or antigenic alteration refers to the mechanism by which an infectious agent such as a protozoan , bacterium or virus alters the proteins or carbohydrates on its surface and thus avoids a host immune response . (wikipedia.org)
  • African trypanosomes control antigenic variation by periodically switching its variant surface glycoprotein involving transposition followed by recombination occurring at the telomeric expression site. (els.net)
  • Surface variation in trypanosomes. (els.net)
  • Antigenic variation in trypanosomes has been the subject of several recent and comprehensive reviews. (ajtmh.org)
  • African trypanosomes-deadly parasites of humans and livestock in tropical Africa-possess a comprehensive system of antigenic variation (AV). Trypanosoma brucei undergo frequent, stochastic changes to their variant surface glycoprotein (VSG) coats, and therefore a developing immune response will be only partially effective against the trypanosome population as some trypanosomes will have already switched to a different VSG coat. (gla.ac.uk)
  • To test whether varying donor contributions represents an additional source of antigenic variability available to trypanosomes, a set of five mosaic VSGs retrieved from a single infection was expressed in non-switching trypanosomes and used to raise antibody responses. (gla.ac.uk)
  • Other work has begun to look at antigenic variation in animal-infective trypanosomes, and we will compare the findings that are emerging, as well as consider how antigenic variation relates to the dynamics of host-trypanosome interaction. (asmscience.org)
  • Antigenic variation in trypanosomes: enhanced phenotypic variation in a eukaryotic parasite. (asmscience.org)
  • First, the process of antigenic variation in the African trypanosomes and second the structure and function of the kinetoplast DNA of trypanosomatids. (gla.ac.uk)
  • Santos da Silva, M. , Hovel-Miner, G. A. , Briggs, E. M. , Elias, M. C. and McCulloch, R. (2018) Evaluation of mechanisms that may generate DNA lesions triggering antigenic variation in African trypanosomes. (gla.ac.uk)
  • Antigenic variation by variant surface glycoprotein (VSG) coat switching in African trypanosomes is one of the most elaborate immune evasion strategies found among pathogens. (gla.ac.uk)
  • Therefore, African trypanosomes combine antigenic variation of their surface coats with the ability to take up transferrin from their mammalian hosts A given VSG coat protein is encoded by a single vsg gene. (hertaistalcadap.ml)
  • Genome organization and DNA accessibility control antigenic variation in trypanosomes. (helmholtz-hzi.de)
  • Antigenic variation of African trypanosomes]. (helmholtz-hzi.de)
  • These extensions of the method reveal new aspects of T. brucei biology and demonstrate the potential of high-throughput approaches for studying antigenic variation, both in trypanosomes and in any pathogen that uses antigenic variation as a means of immune evasion. (rockefeller.edu)
  • In African trypanosomes, homologous recombination also plays a pivotal role in antigenic variation, a survival strategy that relies on changes in surface antigens (Variant Surface Glycoproteins), allowing host immune response evasion and infection of partially immune hosts. (gla.ac.uk)
  • We are exploring how homologous recombination and other DNA repair pathways operate in trypanosomes and influence antigenic variation. (gla.ac.uk)
  • Borst P (1986) Discontinuous transcription and antigenic variation in trypanosomes. (els.net)
  • Antigenic variation in African trypanosomes and malaria. (tolweb.org)
  • antigenic variation The ability of certain pathogenic microorganisms, particularly viruses, to alter the antigens on their outer surface. (encyclopedia.com)
  • In the absence of new results to comment upon, I shall in the present report restrict myself to a concise summary of the structure and possible functions of the major variant surface antigens of Trypanosoma brucei , concluding with a brief assessment of the prospects for immunoprophylaxis and improved diagnosis of the African trypanosomiases in the light of an increased understanding of antigenic variation. (ajtmh.org)
  • True antigenic variation, however, arises in a single clone or genotype in a single host and "involves the loss, gain, or change in a particular antigenic group, usually by loss, gain, or change in one of the polypeptide or polysaccharide antigens…" (3) . (cdc.gov)
  • Many pathogenic microbes evade host immune surveillance by varying the surface antigens, a process termed antigenic variation. (asm.org)
  • The aim of this study was therefore to investigate the evolution of schistosome antigens within and across parasite species to identify genetic changes that could alter the shape of the resultant antigenic proteins. (kingston.ac.uk)
  • PCR and bioinformatic tools were used to analyse the antigenic and structural diversity of tegumental antigens. (kingston.ac.uk)
  • Results revealed antigenic and structural diversity in these antigens including TSP23 across species and within populations of 'Schistosoma', and suggest that the definitive host has played a part in positive and adaptive evolution of schistosomes. (kingston.ac.uk)
  • Our data show that antigens at the parasitized cell surface undergo clonal variation in vitro in the absence of immune pressure at the rate of 2% per generation with concomitant modulations of the adhesive phenotype. (nih.gov)
  • Antigenic variation requires large reservoirs of immunologically diverse antigen genes, which are often generated through homologous recombination, as well as mechanisms to ensure the expression of one or very few antigens at any given time. (helmholtz-hzi.de)
  • Plasmodium falciparum , the causative agent of the most severe form of malaria, undergoes antigenic variation through successive presentation of a family of antigens on the surface of parasitized erythrocytes. (biomedcentral.com)
  • The highly antigenic VSG is so densely packed on the parasite cell surface that it effectively obscures all other antigens from immune recognition. (jhsph.edu)
  • Cahoon LA and Seifert S (2011) Focussing homologous recombination: pilin antigenic variation in the pathogenic Neisseria. (els.net)
  • A series of mini-transposon insertions affecting pilin antigenic variation were localized to three genes in one region of the Gc chromosome. (genetics.org)
  • Mutational analysis with complementation showed that a Gc gene with sequence similarity to the Escherichia coli rdgC gene is involved in pilus-dependent colony phase variation and in pilin antigenic variation. (genetics.org)
  • Since E. coli RecA acts in concert with other proteins, the necessity for Gc RecA in pilin antigenic variation suggests that other factors involved in homologous recombination also have a role in this process. (genetics.org)
  • Although Gc pilin antigenic variation is mediated by RecA-dependent homologous recombination, several attributes of this system suggest that both general and pil -specific recombination factors are involved. (genetics.org)
  • First, Gc pilin antigenic variation is usually unidirectional, whereas homologous recombination often results in the reciprocal exchange of DNA sequences. (genetics.org)
  • In this study, Roche 454 pyrosequencing was used to examine the pilin antigenic variation of Mc strain 8013, as well as 8013 recA , recX , recQ , rep , and recJ mutants, Gc orthologues which have been shown to play a role in pilin antigenic variation. (asm.org)
  • This study confirms that the Mc recA , rep , and recJ genes are essential for pilin antigenic variation. (asm.org)
  • Overall, this study shows that the mechanisms of pilin antigenic variation are conserved between Gc and Mc. (asm.org)
  • One of the best-studied antigenic variation systems is the pilin antigenic variation system of the pathogenic Neisseria , Neisseria gonorrhoeae (gonococcus [Gc]) and Neisseria meningitidis (meningococcus [Mc]) ( 4 ). (asm.org)
  • Pilin antigenic variation occurs when variant DNA sequences from a silent pilS copy transfer to the expressed pilE locus, generating a pilin variant ( 9 , 10 ). (asm.org)
  • Antibody induced variation in malaria parasites. (springer.com)
  • Antigenic variation and immunity to malaria. (springer.com)
  • Antigenic variation and protective immunity in Plasmodium knowlesi malaria. (springer.com)
  • A recent paper in Genome Biology reports the identification of a lncRNA family in Plasmodium falciparum , the cause of the most deadly form of malaria, that may help to explain the mechanism of antigenic variation in virulence genes of this important pathogen. (biomedcentral.com)
  • An understanding of the antigenic diversity of the parasite in such reservoirs, including whether and how this diversity is structured into strains, is fundamental to understanding immunity patterns and developing intervention strategies in the transmission dynamics of P. falciparum malaria. (nature.com)
  • Antigenic variation has serious public health consequences, for example, the current human immunodeficiency virus pandemic and the looming influenza pandemic, as well as a significant challenge to developing vaccines capable of eliciting long‐lasting or life‐long protective immunity against several pathogens. (els.net)
  • These pathogens use antigenic variation to prolong their circulation in the blood and thus increase the likelihood of transmission. (cdc.gov)
  • By convergent evolution, bacterial and protozoal vector-borne pathogens have acquired similar genetic mechanisms for successful antigenic variation. (cdc.gov)
  • Antigenic variation poses a challenge in the development of vaccines against vector-borne pathogens. (cdc.gov)
  • We review infectious pathogens that undergo clonal antigenic variation and, like B. hermsii, depend on arthropod vectors for transmission. (cdc.gov)
  • IMPORTANCE Antigenic variation is a strategy used by many pathogens to escape host immune surveillance and establish persistent infections. (asm.org)
  • Antigenic variation is one of the most prevalent strategies that pathogens employ to establish persistent infections in immunocompetent hosts ( 2 ). (asm.org)
  • Here, we will review antigenic variation systems that rely on homologous DNA recombination and that are found in a wide range of cellular, human pathogens, including bacteria (such as Neisseria spp. (nih.gov)
  • Survival of the African trypanosome in its mammalian hosts has led to the evolution of antigenic variation, a process for evasion of adaptive immunity that has independently evolved in many other viral, bacterial and eukaryotic pathogens. (asmscience.org)
  • Pathogens often persist during infection because of antigenic variation, in which they evade immunity by switching between distinct surface antigen variants. (ed.ac.uk)
  • One of the major obstacles to studying the role of genome architecture in antigenic variation has been the highly repetitive nature and heterozygosity of antigen-gene arrays, which has precluded complete genome assembly in many pathogens. (helmholtz-hzi.de)
  • The proposed research has relevance to public health because the resulting discoveries have the potential to fundamentally advance the field of B. duttonii immune evasion, and may have broad implications for antigenic variation systems in other animal and human pathogens. (grantome.com)
  • The antigenic variation in pathogens maps conceptually to such stabilizing trait differences in ecological competition. (nature.com)
  • Pathogens that evade adaptive immunity typically exhibit antigenic variation. (unibas.ch)
  • Agrawal MR, Ozarkar AD, Gupta S, Deobagkar DN, Deobagkar DD: Comparative study of Plasmodium falciparum Erythrocyte Membrane Protein 1- DBLα domain variants with respect to antigenic variations and docking interaction analysis with glycosaminoglycans. (biomedcentral.com)
  • Plasmodium falciparum , the most deadly parasite species in humans, displays a vigorous system of antigen variation to counter host defenses and families of functionally redundant ligands to invade human cells. (jci.org)
  • This rapid appearance of antigenic and functional heterogeneity has important implications for pathogenesis and acquired immunity. (nih.gov)
  • The observed antigenic heterogeneity also extended to spontaneously transformed B lymphoblastoid cell lines (LCLs) representing viral isolates circulating within US and UK populations. (elsevier.com)
  • Considerable genetic and antigenic heterogeneity was detected among a collection of 17 poliovirus type 3 strains isolated between 1939 and 1958 in studies using monoclonal antibodies and by T1 oligonucleotide mapping. (microbiologyresearch.org)
  • Recent analyses suggest that antigenic heterogeneity may exist within each serotype, but its source, extent and impact remain unclear. (midasnetwork.us)
  • Antigenic heterogeneity of a foot-and-mouth disease virus serotype in the field is mediated by very limited sequence variation at several antigenic sites. (ox.ac.uk)
  • Critical interplay between parasite differentiation, host immunity, and antigenic variation in trypanosome infections. (asmscience.org)
  • Parasite-derived P. falciparum Erythrocyte Membrane Protein 1 (PfEMP1) molecules displayed on the erythrocyte surface are responsible for cytoadherance and undergo antigenic variation in the course of an infection. (pasteur.fr)
  • Here we use sequential cloning of P. falciparum by micromanipulation to investigate the ability of a parasite to switch antigenic and cytoadherence phenotypes. (nih.gov)
  • The double expresser model for immune response-driven antigen variation in trypanosome infections, presented in the Host-Parasite Interaction session, was discussed in relation to rates of development and possible differences in responses between N'Dama and Boran cattle. (fao.org)
  • When applied to promoter regions of genes contained within 21 co-expression gene clusters generated from P. falciparum life cycle microarray data using the semi-supervised clustering algorithm Ontology-based Pattern Identification, GEMS identified 34 putative cis -regulatory elements associated with a variety of parasite processes including sexual development, cell invasion, antigenic variation and protein biosynthesis. (biomedcentral.com)
  • Under normal circumstances, this would ensure quick recognition and clearance of the parasite, but T. brucei has evolved a mechanism for antigenic variation during infection in which the parasite can turn on and off VSG-encoding genes from a genomic repertoire of ~2000 different genes. (jhsph.edu)
  • In addition, we are characterising the process of nuclear DNA replication, which not only appears unusual in this parasite but, remarkably, also influences antigenic variation. (gla.ac.uk)
  • The major capsid protein of GII.4 strains is evolving rapidly, resulting in new epidemic strains with altered antigenic potentials. (nih.gov)
  • The mechanisms operating in the genomic rearrangements associated with these forms of pilus variation were investigated through the study of isogenic strains of gonococci bearing either wild-type or altered recA alleles. (genetics.org)
  • Examination of the rates of pilus phase variation and the genetic basis for changes in piliation status displayed by these strains show that recA mediated homologous recombination is required for these high frequency events and confirm that the nonpiliated state results from mutations in the expressed pilin gene. (genetics.org)
  • This diversity between strains in an immunodominant antigen is often called antigenic variation. (cdc.gov)
  • This assay provides an affordable and efficient solution for quantifying antigenic variation frequency in mutant strains and for defining the recombination products of the process. (asm.org)
  • These mutants mimic the antigenic drift of field strains that arose naturally between 1968 and 1973. (springer.com)
  • Since the strains examined differed only in their antigenic properties, it is likely that the variable peptide in which amino acid substitutions occurred formed part of the antigenic determinant. (springer.com)
  • Similar stable phylogenetic relationships were observed in TBE virus strains of other subtypes, which indicates that the virus is remarkably stable and not subject to major antigenic variation (13,14). (thefreedictionary.com)
  • Antigenic variation among newly isolated strains of parainfluenza type 4 virus. (thefreedictionary.com)
  • The genetic and/or antigenic differences between street rabies virus (RABV) and vaccine strains could potentially affect effectiveness of rabies vaccines. (cdc.gov)
  • The rate of antigenic variation in influenza viruses is very high, making it difficult for the immune system to recognize the many different strains of Influenzavirus. (chromoscience.com)
  • Although the body may develop immunity to one strain through natural exposure or vaccination, antigenic variation results in the continual emergence of new strains that the immune system will not recognize. (chromoscience.com)
  • Thus antigenic variations and similarities are present in excretory/secretory products of different strains of T. gondii. (afpm.org.my)
  • In the present investigation we characterized the antigenic diversity of the VP4 and VP7 proteins in 309 and 261 human rotavirus strains isolated during two consecutive epidemic seasons, respectively, in three different regions of Mexico. (asm.org)
  • Antigenic and structural variation in the major nucleocapsid protein, VPN41, from different strains of respiratory syncytial (RS) virus was observed using a combination of monoclonal antibodies and two-dimensional peptide mapping. (microbiologyresearch.org)
  • Competitive radioimmunoassay studies using N1 and N2 antibodies revealed two discrete antigenic groups among the seven human strains of RS virus examined. (microbiologyresearch.org)
  • Some of our study strains showed substitutions at or in the vicinity of the antigenic sites of the HA1 region which may affect the efficacy of the vaccine. (ac.ir)
  • Strains of the GII.4 genotype cause pandemic waves associated with viral evolution and subsequent antigenic drift and ligand-binding modulation. (cdc.gov)
  • One of the most widely used strategies of immune evasion is antigenic variation, in which immunogenic molecules expressed on the surface of a microorganism are continuously modified. (nih.gov)
  • This chapter will discuss the implications of such VSG diversity for immune evasion by antigenic variation, and will consider how this expressed diversity can arise, drawing on a growing body of work that has begun to examine the proteins and sequences through which VSG switching is catalyzed. (asmscience.org)
  • Size variation and C-terminal antigenic divergence of Vaa could affect the adherence of M. hominis and evasion of antibody-mediated immunity, thereby contributing to the organism's adaptive capability in the human host. (asm.org)
  • A key mechanism for immune evasion and recurrent bacteremia by the East African relapsing fever spirochete, Borrelia duttonii, is antigenic variatio of the Vlp and Vsp surface proteins. (grantome.com)
  • T cell epitopes that exhibit sequence variation may not be subject to the same evasion mechanisms, and hence vaccines that include such variable epitopes may be more efficacious. (unibas.ch)
  • What role do extravascular parasites play in antigenic variation and immune evasion? (jhsph.edu)
  • In the bacterium Borrelia burgdorferi, the cause of Lyme disease, the surface lipoprotein VlsE can undergo recombination which results in antigenic diversity. (wikipedia.org)
  • Intragenic recombination between the single complete pilin gene (expression locus) and multiple, distinct, partial pilin gene copies (silent, storage loci) is thought to account for the generation of pilus antigenic diversity and piliation phase (on-off) changes exhibited by Neisseria gonorrhoeae . (genetics.org)
  • Impact of sequence diversity in the Moraxella catarrhalis UspA2/UspA2H head domain on vitronectin binding and antigenic variation. (lu.se)
  • Antigenic diversity is generated by distinct evolutionary mechanisms in African trypanosome species. (helmholtz-hzi.de)
  • We report moderate antigenic diversity within each serotype, resulting in genotype-specific patterns of heterotypic cross-neutralization. (midasnetwork.us)
  • Antigenic variation or antigenic alteration refers to the mechanism by which an infectious agent such as a protozoan, bacterium or virus alters the proteins or carbohydrates on its surface and thus avoids a host immune response, making it one of the mechanisms of antigenic escape. (wikipedia.org)
  • Antigenic variation can occur by altering a variety of surface molecules including proteins and carbohydrates. (wikipedia.org)
  • Many of the proteins known to show antigenic or phase variation are related to virulence. (wikipedia.org)
  • Antigenic variation or antigenic alteration refers to the mechanism by which an infectious agent such as a protozoan , bacterium or virus alters the proteins or carbohydrates on its surface and thus avoids a host immune response . (wikipedia.org)
  • Through the understanding of the growing variety of mechanisms of the antigenic variation of surface proteins, it has become possible for us to determine what is preventing the host organism from mounting an effective immune response. (els.net)
  • Many viruses, bacteria, and parasites can alter the expression or composition of their surface-exposed proteins to escape host immune surveillance, a process defined as antigenic variation ( 1 ). (asm.org)
  • Demonstration of antigenic variation among rabies virus isolates by using monoclonal antibodies to nucleocapsid proteins. (thefreedictionary.com)
  • Two additional variant multigene families that, like PfEMP1, are expressed on the surface of infected red blood cells, induce specific antibodies, and undergo clonal variation have been described recently 56 , These proteins are encoded by the rif and STEVOR genes, which are located near the telomeres that contain the var genes. (hertaistalcadap.ml)
  • a) In antigenic drift, mutations in the genes for the surface proteins neuraminidase and/or hemagglutinin result in small antigenic changes over time. (chromoscience.com)
  • Antigenic drift is the result of point mutations causing slight changes in the spike proteins hemagglutinin (H) and neuraminidase (N). On the other hand, antigenic shift is a major change in spike proteins due to gene reassortment. (chromoscience.com)
  • These include antigenic variation, through which an infecting organism prevents clearance by periodically altering the identity of proteins that are visible to the immune system of the host1. (helmholtz-hzi.de)
  • Antigenic variation is the means by which a number of highly pathogenic microorganisms, ranging from the electronmicroscopic human viruses to bacteria to fungi and unicellular protozoan parasites, passively evade immune surveillance. (els.net)
  • Antigenic variation is exhibited by a number of highly pathogenic microorganisms including human viruses, bacteria, fungi and unicellular protozoans. (els.net)
  • Viruses are also said to have antigenic variation but are excluded from this review because the mechanism they use usually depends either on the accumulation of point mutations in a single genotype (e.g., the antigenic drift of influenza A virus) or on recombination or reassortment between two different genotypes infecting the same host (e.g., antigenic shift of influenza A virus). (cdc.gov)
  • We analyzed H5N6 viruses from 2014-2018 from Guangdong Province, revealing antigenic drift and decreased antibody response against the vaccine strain in vaccinated chickens. (cdc.gov)
  • We report our investigation of the prevalence, evolution, and antigenic variation of H5N6 viruses during 2014-2018 in Guangdong Province. (cdc.gov)
  • Limitations of this approach are that antigenic relationships among field viruses are not addressed, as comparisons are only with potential vaccine virus. (surrey.ac.uk)
  • Here, we used antigenic cartography to quantify and visualize the antigenic relationships among FMD serotype A viruses, aiming to improve the understanding of FMDV antigenic evolution and the scope and reliability of vaccine matching. (surrey.ac.uk)
  • Nevertheless, by comparing antigenic distances measured from the antigenic maps with the full capsid (P1) sequence, we identified a specific amino acid substitution associated with an antigenic mismatch among field viruses and a commonly used prototype vaccine strain, A22/IRQ/24/64. (surrey.ac.uk)
  • Antigenic drift and antigenic shift in influenza viruses. (chromoscience.com)
  • This reassortment for antigenic shift occurs typically when two different influenza viruses infect the same host. (chromoscience.com)
  • To identify substitutions responsible for antigenic variation in circulating viruses, we performed an integrated meta-analysis of all published H9 haemagglutinin sequences and antigenic data. (willharvey.me)
  • The results suggest that within a serotype of FMDV, antigenically highly divergent viruses can arise in the field by very limited sequence variation at exposed key residues of each of several antigenic sites. (ox.ac.uk)
  • Antigenic variation has been described for mammalian influenza viruses and for highly pathogenic avian influenza viruses that circulate in poultry, but much less is known about antigenic variation of LPAIVs. (eur.nl)
  • We investigated the evolutionary history and intercontinental gene flow based on the hemagglutinin (HA) gene and used representative viruses from genetically distinct lineages to determine their antigenic properties by hemagglutination inhibition assays. (eur.nl)
  • Amino acid positions in the HA protein that may be involved in the antigenic variation were inferred, and some of the positions were located near the receptor binding site of the HA protein, as they are in the HA protein of mammalian influenza A viruses. (eur.nl)
  • To test if antigenic drift may contribute to GII.4 persistence, human memory B cells were immortalized and the resulting human monoclonal antibodies (mAbs) characterized for reactivity to a panel of time-ordered GII.4 virus-like particles (VLPs). (nih.gov)
  • antibodies which induce antigenic variation and antibodies which destroy parasites. (springer.com)
  • Sequence variation in this region may underlie the strain-dependent binding of some monoclonal antibodies to Vaa products. (asm.org)
  • Antigenic variation in a major discontinuous site (site D) of foot-and-mouth disease virus (FMDV) of serotype C has been evaluated with neutralizing monoclonal antibodies. (ox.ac.uk)
  • Differences in antigenicity are due to a very limited number of substitutions of surface amino acids accessible to antibodies and located within antigenic sites previously identified on FMDV. (ox.ac.uk)
  • Although the impact of polymerases on fitness remains uncertain, antigenic variation resulting in decreased potency of antibodies to epitope A, coupled with altered ligand binding, likely contributed significantly to the spread of GII.4 2015 and its replacement of GII.4 2012 as the predominant norovirus outbreak strain. (cdc.gov)
  • In a strain that is deficient in recA mediated homologous recombination, pilus phase variation occurs at a 100-1000-fold reduced rate and results predominantly from one class of spontaneous frameshift mutations within the pilin structural gene. (genetics.org)
  • One example of antigenic variation occurs in B. hermsii, a cause of tickborne relapsing fever (4) , which has a protein homologous to the OspC protein of B. burgdorferi. (cdc.gov)
  • Antigenic variation of foot-and-mouth disease virus serotype A. (surrey.ac.uk)
  • Using mutant VLPs designed to alter predicted antigenic epitopes, two evolving, GII.4-specific, blockade epitopes were mapped. (nih.gov)
  • Five antigenic peptides have been identified as the least variable epitopes, with just fewer amino acid substitutions. (dovepress.com)
  • Extensive variation, comparable to that of continuous epitopes within the hypervariable immunodominant site A (the VP1 G-H loop), was found. (ox.ac.uk)
  • Not to be confused with Antigenic drift or Antigenic shift . (wikipedia.org)
  • He then moves on to more recent discoveries regarding immunity, antigenic variation , and the role of variable surface glycoproteins. (thefreedictionary.com)
  • falciparum is the var gene family which encodes PfEMP1, a protein that is exported to the 'knob like' binding structures on the surface of infected erythrocytes with a key role in antigenic variation and cytoadherence (12). (thefreedictionary.com)
  • It seems likely that similar groups of glycoproteins are responsible for antigenic variation in other salivarian trypanosome species. (ajtmh.org)
  • It is now clear that antigenic variation in T. brucei can be largely, if not entirely, explained by the sequential expression of alternative cell surface glycoproteins. (ajtmh.org)
  • Most studies of trypanosome antigenic variation have focused on T. brucei , the causative agent of human sleeping sickness. (asmscience.org)
  • Although this process, referred to as antigenic variation, is the major mechanism of pathogenesis for T. brucei, the dynamics of VSG expression in T. brucei during an infection are poorly understood. (rockefeller.edu)
  • The type IV pili of Mc isolates play a critical role in host surface adherence, and its major pilin component (PilE) can undergo antigenic variation. (asm.org)
  • Our results suggest that predicting antigenic difference using genetic sequence alone or by geographical location is not currently reliable. (surrey.ac.uk)
  • The data suggested that vaccine escape mutants have derived from only few mutations at several antigenic sites. (dovepress.com)
  • Several antigenic sites were identified and mapped onto the three-dimensional protein structure. (dovepress.com)
  • Antigenic variation is employed by a number of different protozoan parasites. (wikipedia.org)
  • Antigenic Variation in Eukaryotic Parasites, pp. 953-971. (asmscience.org)
  • Segmental gene conversion was therefore found to be both prominent in chronic African trypanosome antigenic variation, and capable of bringing antigenic novelty to an infection, with important consequences for the dynamics of AV, and the nature of selection pressure on the silent VSG archive. (gla.ac.uk)
  • As the success of an infection depends on the immunological memory of a host, new and rare antigenic types have a fitness advantage in the transmission system relative to common ones. (nature.com)
  • The influence of antigenic variation on cytotoxic T lymphocyte responses in HIV-1 infection. (ox.ac.uk)
  • The propensity of HIV-1 for genetic variation, a consequence of error-prone reverse transcription combined with high rates of replication, is thought to contribute to the establishment of persistent infection in the host despite the presence of a vigorous antiviral immune response. (ox.ac.uk)
  • Characterization of the antigenic, immunogenic, and pathogenic variation of infectious bursal disease virus due to propagation in different host systems (bursa, embryo, and cell culture). (semanticscholar.org)
  • Antigenic variation is a major mechanism of passively evading the host immune surveillance. (els.net)
  • Dengue genetic divergence generates within-serotype antigenic variation, but serotypes dominate evolutionary dynamics. (midasnetwork.us)
  • We also quantify the impact of antigenic variation on real-world DENV population dynamics, and find that serotype-level antigenic fitness is a dominant driver of dengue clade turnover. (midasnetwork.us)
  • This can trigger an immune response called antigenic variation. (jpost.com)
  • An in-silico approach was taken to reveal the antigenic heterogeneities within the capsid protein VP1 of Asia1. (dovepress.com)
  • Both the capsid and envelope are antigenic. (thefreedictionary.com)
  • Antigenic divergence suggested by correlation between antigenic variation and pulsed-field gel electrophoresis profiles of Bordetella pertussis isolates in Japan. (thefreedictionary.com)
  • Here, we construct a sequence-based model to directly map antigenic change to underlying genetic divergence. (midasnetwork.us)
  • Interspecies variations within the OAg lie in the different substitutions of the 6-deoxytalose residues, e.g. (nature.com)
  • We identify 49 specific substitutions and four colinear substitution clusters that robustly predict dengue antigenic relationships. (midasnetwork.us)
  • HIV‐1 surface glycoproteins display antigenic variation due to a high mutation rate during replication and significant tolerance of the variation. (els.net)
  • We validated this statistical analysis experimentally and allocated several new residues to H9N2 antigenic sites, providing molecular markers that will help explain vaccine breakdown in the field and inform vaccine selection decisions. (willharvey.me)
  • These results provide a more nuanced understanding of the relationship between dengue genetic and antigenic evolution, and quantify the effect of antigenic fitness on dengue evolutionary dynamics. (midasnetwork.us)
  • The essential features of trypanosome antigenic variation have been understood for many years and comprise a dense, protective Variant Surface Glycoprotein (VSG) coat, which can be changed by recombination-based and transcription-based processes that focus on telomeric VSG gene transcription sites. (asmscience.org)
  • Our long-term goals are to decipher the mechanistic details of vlp/vsp antigenic variation in B. duttonii, and to expand these findings to the louse-borne variant, B. recurrentis. (grantome.com)
  • Variations at these antigenic sites were analyzed by calculating the protein variability index and finding mutation combinations. (dovepress.com)
  • Single-step antigenic mutants, derived experimentally from the strain A/NT60/68 (H3N2), have been used to study the chemistry of antigenic variation within the present subtype of influenza A virus. (springer.com)
  • Antigenic Variation of the Haemagglutinin Gene of the Influenza A (H1N1) pdm09 Virus Circulating in Shiraz, February-April 2013', Iranian Journal of Immunology , 12(3), pp. 198-208. (ac.ir)