Capsid Proteins: Proteins that form the CAPSID of VIRUSES.Capsid: The outer protein protective shell of a virus, which protects the viral nucleic acid.Virus Assembly: The assembly of VIRAL STRUCTURAL PROTEINS and nucleic acid (VIRAL DNA or VIRAL RNA) to form a VIRUS PARTICLE.Virion: The infective system of a virus, composed of the viral genome, a protein core, and a protein coat called a capsid, which may be naked or enclosed in a lipoprotein envelope called the peplos.Molecular Sequence Data: 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.Viral Proteins: Proteins found in any species of virus.Cryoelectron Microscopy: Electron microscopy involving rapid freezing of the samples. The imaging of frozen-hydrated molecules and organelles permits the best possible resolution closest to the living state, free of chemical fixatives or stains.Amino Acid Sequence: 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.Viral Structural Proteins: Viral proteins that are components of the mature assembled VIRUS PARTICLES. They may include nucleocapsid core proteins (gag proteins), enzymes packaged within the virus particle (pol proteins), and membrane components (env proteins). These do not include the proteins encoded in the VIRAL GENOME that are produced in infected cells but which are not packaged in the mature virus particle,i.e. the so called non-structural proteins (VIRAL NONSTRUCTURAL PROTEINS).Genome, Viral: The complete genetic complement contained in a DNA or RNA molecule in a virus.DNA, Viral: Deoxyribonucleic acid that makes up the genetic material of viruses.Cell Line: Established cell cultures that have the potential to propagate indefinitely.RNA, Viral: Ribonucleic acid that makes up the genetic material of viruses.Antigens, Viral: Substances elaborated by viruses that have antigenic activity.Antibodies, Viral: Immunoglobulins produced in response to VIRAL ANTIGENS.Norwalk virus: The type species in the genus NOROVIRUS, first isolated in 1968 from the stools of school children in Norwalk, Ohio, who were suffering from GASTROENTERITIS. The virions are non-enveloped spherical particles containing a single protein. Multiple strains are named after the places where outbreaks have occurred.Virus Replication: The process of intracellular viral multiplication, consisting of the synthesis of PROTEINS; NUCLEIC ACIDS; and sometimes LIPIDS, and their assembly into a new infectious particle.Caliciviridae: A family of RNA viruses infecting a broad range of animals. Most individual species are restricted to their natural hosts. They possess a characteristic six-pointed starlike shape whose surfaces have cup-shaped (chalice) indentions. Transmission is by contaminated food, water, fomites, and occasionally aerosolization of secretions. Genera include LAGOVIRUS; NORWALK-LIKE VIRUSES; SAPPORO-LIKE VIRUSES; and VESIVIRUS.Calicivirus, Feline: A species of the genus VESIVIRUS infecting cats. Transmission occurs via air and mechanical contact.Spodoptera: A genus of owlet moths of the family Noctuidae. These insects are used in molecular biology studies during all stages of their life cycle.Poliovirus: A species of ENTEROVIRUS which is the causal agent of POLIOMYELITIS in humans. Three serotypes (strains) exist. Transmission is by the fecal-oral route, pharyngeal secretions, or mechanical vector (flies). Vaccines with both inactivated and live attenuated virus have proven effective in immunizing against the infection.Baculoviridae: Family of INSECT VIRUSES containing two subfamilies: Eubaculovirinae (occluded baculoviruses) and Nudibaculovirinae (nonoccluded baculoviruses). The Eubaculovirinae, which contain polyhedron-shaped inclusion bodies, have two genera: NUCLEOPOLYHEDROVIRUS and GRANULOVIRUS. Baculovirus vectors are used for expression of foreign genes in insects.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Dependovirus: A genus of the family PARVOVIRIDAE, subfamily PARVOVIRINAE, which are dependent on a coinfection with helper adenoviruses or herpesviruses for their efficient replication. The type species is Adeno-associated virus 2.RNA Viruses: Viruses whose genetic material is RNA.Genes, Viral: The functional hereditary units of VIRUSES.Reoviridae: A family of unenveloped RNA viruses with cubic symmetry. The twelve genera include ORTHOREOVIRUS; ORBIVIRUS; COLTIVIRUS; ROTAVIRUS; Aquareovirus, Cypovirus, Phytoreovirus, Fijivirus, Seadornavirus, Idnoreovirus, Mycoreovirus, and Oryzavirus.Parvovirus: A genus of the family PARVOVIRIDAE, subfamily PARVOVIRINAE, infecting a variety of vertebrates including humans. Parvoviruses are responsible for a number of important diseases but also can be non-pathogenic in certain hosts. The type species is MINUTE VIRUS OF MICE.Models, Molecular: Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.Polyomavirus: A genus of potentially oncogenic viruses of the family POLYOMAVIRIDAE. These viruses are normally present in their natural hosts as latent infections. The virus is oncogenic in hosts different from the species of origin.Caliciviridae Infections: Virus diseases caused by CALICIVIRIDAE. They include HEPATITIS E; VESICULAR EXANTHEMA OF SWINE; acute respiratory infections in felines, rabbit hemorrhagic disease, and some cases of gastroenteritis in humans.Parvoviridae: A family of very small DNA viruses containing a single molecule of single-stranded DNA and consisting of two subfamilies: PARVOVIRINAE and DENSOVIRINAE. They infect both vertebrates and invertebrates.Norovirus: A genus in the family CALICIVIRIDAE, associated with epidemic GASTROENTERITIS in humans. The type species, NORWALK VIRUS, contains multiple strains.Sindbis Virus: The type species of ALPHAVIRUS normally transmitted to birds by CULEX mosquitoes in Egypt, South Africa, India, Malaya, the Philippines, and Australia. It may be associated with fever in humans. Serotypes (differing by less than 17% in nucleotide sequence) include Babanki, Kyzylagach, and Ockelbo viruses.Parvovirus, Canine: A species of the genus PARVOVIRUS and a host range variant of FELINE PANLEUKOPENIA VIRUS. It causes a highly infectious fulminating ENTERITIS in dogs producing high mortality. It is distinct from CANINE MINUTE VIRUS, a species in the genus BOCAVIRUS. This virus can also infect cats and mink.Open Reading Frames: A sequence of successive nucleotide triplets that are read as CODONS specifying AMINO ACIDS and begin with an INITIATOR CODON and end with a stop codon (CODON, TERMINATOR).Nodaviridae: A family of RNA viruses infecting insects and fish. There are two genera: Alphanodavirus and Betanodavirus.Picornaviridae: A family of small RNA viruses comprising some important pathogens of humans and animals. Transmission usually occurs mechanically. There are nine genera: APHTHOVIRUS; CARDIOVIRUS; ENTEROVIRUS; ERBOVIRUS; HEPATOVIRUS; KOBUVIRUS; PARECHOVIRUS; RHINOVIRUS; and TESCHOVIRUS.Virus Uncoating: Intracellular step that follows VIRUS INTERNALIZATION during which the viral nucleic acid and CAPSID are separated.Microscopy, Electron: Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.Rotavirus: A genus of REOVIRIDAE, causing acute gastroenteritis in BIRDS and MAMMALS, including humans. Transmission is horizontal and by environmental contamination. Seven species (Rotaviruses A thru G) are recognized.Oncogene Proteins, Viral: Products of viral oncogenes, most commonly retroviral oncogenes. They usually have transforming and often protein kinase activities.Neutralization Tests: 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).Genetic Vectors: DNA molecules capable of autonomous replication within a host cell and into which other DNA sequences can be inserted and thus amplified. Many are derived from PLASMIDS; BACTERIOPHAGES; or VIRUSES. They are used for transporting foreign genes into recipient cells. Genetic vectors possess a functional replicator site and contain GENETIC MARKERS to facilitate their selective recognition.Aphthovirus: 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.Parvoviridae Infections: Virus infections caused by the PARVOVIRIDAE.Cercopithecus aethiops: A species of CERCOPITHECUS containing three subspecies: C. tantalus, C. pygerythrus, and C. sabeus. They are found in the forests and savannah of Africa. The African green monkey (C. pygerythrus) is the natural host of SIMIAN IMMUNODEFICIENCY VIRUS and is used in AIDS research.Epitopes: Sites on an antigen that interact with specific antibodies.Iridovirus: A genus of IRIDOVIRIDAE comprising small iridescent insect viruses. The infected larvae and purified virus pellets exhibit a blue to purple iridescence.Bromovirus: A genus of tripartite plant viruses in the family BROMOVIRIDAE. Transmission is by beetles. Brome mosaic virus is the type species.Rubella virus: The type (and only) species of RUBIVIRUS causing acute infection in humans, primarily children and young adults. Humans are the only natural host. A live, attenuated vaccine is available for prophylaxis.Enterovirus B, Human: A species of ENTEROVIRUS infecting humans and containing 36 serotypes. It is comprised of all the echoviruses and a few coxsackieviruses, including all of those previously named coxsackievirus B.Hemorrhagic Disease Virus, Rabbit: A species in the genus LAGOVIRUS which causes hemorrhagic disease, including hemorrhagic septicemia, in rabbits.Viral Vaccines: Suspensions of attenuated or killed viruses administered for the prevention or treatment of infectious viral disease.Parvovirus B19, Human: The type species of ERYTHROVIRUS and the etiological agent of ERYTHEMA INFECTIOSUM, a disease most commonly seen in school-age children.Vero Cells: A CELL LINE derived from the kidney of the African green (vervet) monkey, (CERCOPITHECUS AETHIOPS) used primarily in virus replication studies and plaque assays.Herpesvirus 1, Human: The type species of SIMPLEXVIRUS causing most forms of non-genital herpes simplex in humans. Primary infection occurs mainly in infants and young children and then the virus becomes latent in the dorsal root ganglion. It then is periodically reactivated throughout life causing mostly benign conditions.Mutation: 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.Papillomaviridae: A family of small, non-enveloped DNA viruses infecting birds and most mammals, especially humans. They are grouped into multiple genera, but the viruses are highly host-species specific and tissue-restricted. They are commonly divided into hundreds of papillomavirus "types", each with specific gene function and gene control regions, despite sequence homology. Human papillomaviruses are found in the genera ALPHAPAPILLOMAVIRUS; BETAPAPILLOMAVIRUS; GAMMAPAPILLOMAVIRUS; and MUPAPILLOMAVIRUS.Circovirus: A genus of the family CIRCOVIRIDAE that infects SWINE; PSITTACINES; and non-psittacine BIRDS. Species include Beak and feather disease virus causing a fatal disease in psittacine birds, and Porcine circovirus causing postweaning multisystemic wasting syndrome in pigs (PORCINE POSTWEANING MULTISYSTEMIC WASTING SYNDROME).Minute virus of mice: The type species of PARVOVIRUS prevalent in mouse colonies and found as a contaminant of many transplanted tumors or leukemias.Recombinant Fusion Proteins: Recombinant proteins produced by the GENETIC TRANSLATION of fused genes formed by the combination of NUCLEIC ACID REGULATORY SEQUENCES of one or more genes with the protein coding sequences of one or more genes.Cyclophilin A: A 17-KDa cytoplasmic PEPTIDYLPROLYL ISOMERASE involved in immunoregulation. It is a member of the cyclophilin family of proteins that binds to CYCLOSPORINE.Recombinant Proteins: Proteins prepared by recombinant DNA technology.Insect Viruses: Viruses infecting insects, the largest family being BACULOVIRIDAE.Panicum: A plant genus of the family POACEAE. The seed is one of the EDIBLE GRAINS used in millet cereals and in feed for birds and livestock (ANIMAL FEED). It contains diosgenin (SAPONINS).Enterovirus A, Human: A species of ENTEROVIRUS infecting humans and containing 10 serotypes, mostly coxsackieviruses.Orthoreovirus, Mammalian: A species of ORTHOREOVIRUS infecting mammals (other than baboons). There are four serotypes. In humans they are generally benign but may sometimes cause upper respiratory tract illness or enteritis in infants and children. MAMMALIAN ORTHOREOVIRUS 3 is a very pathogenic virus in laboratory rodents.Virosomes: Semi-synthetic complex derived from nucleic-acid free viral particles. They are essentially reconstituted viral coats, where the infectious nucleocapsid is replaced by a compound of choice. Virosomes retain their fusogenic activity and thus deliver the incorporated compound (antigens, drugs, genes) inside the target cell. They can be used for vaccines (VACCINES, VIROSOME), drug delivery, or gene transfer.Infectious bursal disease virus: A species of AVIBIRNAVIRUS causing severe inflammation of the bursa of Fabricius in chickens and other fowl. Transmission is thought to be through contaminated feed or water. Vaccines have been used with varying degrees of success.Mosaic Viruses: Viruses which produce a mottled appearance of the leaves of plants.Gene Expression Regulation, Viral: Any of the processes by which cytoplasmic factors influence the differential control of gene action in viruses.DNA Virus InfectionsNucleocapsid: A protein-nucleic acid complex which forms part or all of a virion. It consists of a CAPSID plus enclosed nucleic acid. Depending on the virus, the nucleocapsid may correspond to a naked core or be surrounded by a membranous envelope.Receptors, Virus: Specific molecular components of the cell capable of recognizing and interacting with a virus, and which, after binding it, are capable of generating some signal that initiates the chain of events leading to the biological response.Protein Conformation: The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain).HeLa Cells: The first continuously cultured human malignant CELL LINE, derived from the cervical carcinoma of Henrietta Lacks. These cells are used for VIRUS CULTIVATION and antitumor drug screening assays.Sequence Alignment: 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.Aleutian Mink Disease Virus: A species of PARVOVIRUS that causes a disease in mink, mainly those homozygous for the recessive Aleutian gene which determines a desirable coat color.Protein PrecursorsDNA Packaging: The folding of an organism's DNA molecule into a compact, orderly structure that fits within the limited space of a CELL or VIRUS PARTICLE.Cloning, Molecular: 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.Ranavirus: A genus of IRIDOVIRIDAE which infects fish, amphibians and reptiles. It is non-pathogenic for its natural host, Rana pipiens, but is lethal for other frogs, toads, turtles and salamanders. Frog virus 3 is the type species.Amino Acid Substitution: The naturally occurring or experimentally induced replacement of one or more AMINO ACIDS in a protein with another. If a functionally equivalent amino acid is substituted, the protein may retain wild-type activity. Substitution may also diminish, enhance, or eliminate protein function. Experimentally induced substitution is often used to study enzyme activities and binding site properties.Epitope Mapping: 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.Simian virus 40: A species of POLYOMAVIRUS originally isolated from Rhesus monkey kidney tissue. It produces malignancy in human and newborn hamster kidney cell cultures.Totivirus: A genus of RNA fungi viruses in the family TOTIVIRIDAE. Some of the viruses contain additional satellite RNA or defective RNA. Transmission occurs during cell division, sporogenesis and cell fusion. The type species is Saccharomyces cerevisiae virus L-A.Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Bacteriophage T4: Virulent bacteriophage and type species of the genus T4-like phages, in the family MYOVIRIDAE. It infects E. coli and is the best known of the T-even phages. Its virion contains linear double-stranded DNA, terminally redundant and circularly permuted.Rous sarcoma virus: A species of replication-competent oncogene-containing virus in the genus ALPHARETROVIRUS. It is the original source of the src oncogene (V-SRC GENES) and causes sarcoma in chickens.Enterovirus: A genus of the family PICORNAVIRIDAE whose members preferentially inhabit the intestinal tract of a variety of hosts. The genus contains many species. Newly described members of human enteroviruses are assigned continuous numbers with the species designated "human enterovirus".Bluetongue virus: The type species of ORBIVIRUS causing a serious disease in sheep, especially lambs. It may also infect wild ruminants and other domestic animals.Protein Structure, Tertiary: The level of protein structure in which combinations of secondary protein structures (alpha helices, beta sheets, loop regions, and motifs) pack together to form folded shapes called domains. Disulfide bridges between cysteines in two different parts of the polypeptide chain along with other interactions between the chains play a role in the formation and stabilization of tertiary structure. Small proteins usually consist of only one domain but larger proteins may contain a number of domains connected by segments of polypeptide chain which lack regular secondary structure.Hepatitis E virus: A positive-stranded RNA virus species in the genus HEPEVIRUS, causing enterically-transmitted non-A, non-B hepatitis (HEPATITIS E).Mamastrovirus: A genus of small, circular RNA viruses in the family ASTROVIRIDAE. They cause GASTROENTERITIS and are found in the stools of several vertebrates including humans. Transmission is by the fecal-oral route and there are at least eight human serotypes. The type species is Human astrovirus.Comovirus: A genus of plant viruses of the family COMOVIRIDAE in which the bipartite genome is encapsidated in separate icosahedral particles. Mosaic and mottle symptoms are characteristic, and transmission is exclusively by leaf-feeding beetles. Cowpea mosaic virus is the type species.Virus Release: Release of a virus from the host cell following VIRUS ASSEMBLY and maturation. Egress can occur by host cell lysis, EXOCYTOSIS, or budding through the plasma membrane.Cricetinae: A subfamily in the family MURIDAE, comprising the hamsters. Four of the more common genera are Cricetus, CRICETULUS; MESOCRICETUS; and PHODOPUS.Sequence Homology, Amino Acid: The degree of similarity between sequences of amino acids. This information is useful for the analyzing genetic relatedness of proteins and species.Cross Reactions: Serological reactions in which an antiserum against one antigen reacts with a non-identical but closely related antigen.Hepatovirus: A genus of PICORNAVIRIDAE causing infectious hepatitis naturally in humans and experimentally in other primates. It is transmitted through fecal contamination of food or water. HEPATITIS A VIRUS is the type species.Gene Products, gag: Proteins coded by the retroviral gag gene. The products are usually synthesized as protein precursors or POLYPROTEINS, which are then cleaved by viral proteases to yield the final products. Many of the final products are associated with the nucleoprotein core of the virion. gag is short for group-specific antigen.Cell Nucleus: Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (CELL NUCLEOLUS). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the ENDOPLASMIC RETICULUM. A cell may contain more than one nucleus. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)Virus Attachment: The binding of virus particles to receptors on the host cell surface. For enveloped viruses, the virion ligand is usually a surface glycoprotein as is the cellular receptor. For non-enveloped viruses, the virus CAPSID serves as the ligand.Enterovirus InfectionsRhinovirus: A genus of PICORNAVIRIDAE inhabiting primarily the respiratory tract of mammalian hosts. It includes over 100 human serotypes associated with the COMMON COLD.Satellite Viruses: Defective viruses which can multiply only by association with a helper virus which complements the defective gene. Satellite viruses may be associated with certain plant viruses, animal viruses, or bacteriophages. They differ from satellite RNA; (RNA, SATELLITE) in that satellite viruses encode their own coat protein.Virus Internalization: The entering of cells by viruses following VIRUS ATTACHMENT. This is achieved by ENDOCYTOSIS, by direct MEMBRANE FUSION of the viral membrane with the CELL MEMBRANE, or by translocation of the whole virus across the cell membrane.Feline panleukopenia virus: A species of PARVOVIRUS infecting cats with a highly contagious enteric disease. Host range variants include mink enteritis virus, canine parvovirus (PARVOVIRUS, CANINE), and raccoon parvovirus. After infecting their new hosts, many of these viruses have further evolved and are now considered distinct species.Insects: The class Insecta, in the phylum ARTHROPODA, whose members are characterized by division into three parts: head, thorax, and abdomen. They are the dominant group of animals on earth; several hundred thousand different kinds having been described. Three orders, HEMIPTERA; DIPTERA; and SIPHONAPTERA; are of medical interest in that they cause disease in humans and animals. (From Borror et al., An Introduction to the Study of Insects, 4th ed, p1)HIV-1: The type species of LENTIVIRUS and the etiologic agent of AIDS. It is characterized by its cytopathic effect and affinity for the T4-lymphocyte.Protein Binding: The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.Microscopy, Electron, Transmission: Electron microscopy in which the ELECTRONS or their reaction products that pass down through the specimen are imaged below the plane of the specimen.Aleutian Mink Disease: A slow progressive disease of mink caused by the ALEUTIAN MINK DISEASE VIRUS. It is characterized by poor reproduction, weight loss, autoimmunity, hypergammaglobulinemia, increased susceptibility to bacterial infections, and death from renal failure. The disease occurs in all color types, but mink which are homozygous recessive for the Aleutian gene for light coat color are particularly susceptible.DNA Viruses: Viruses whose nucleic acid is DNA.JC Virus: A species of POLYOMAVIRUS, originally isolated from the brain of a patient with progressive multifocal leukoencephalopathy. The patient's initials J.C. gave the virus its name. Infection is not accompanied by any apparent illness but serious demyelinating disease can appear later, probably following reactivation of latent virus.Levivirus: A bacteriophage genus of the family LEVIVIRIDAE, whose viruses contain the short version of the genome and have a separate gene for cell lysis.Closterovirus: A genus of plant viruses in the family CLOSTEROVIRIDAE containing highly flexuous filaments. Some members are important pathogens of crop plants. Natural vectors include APHIDS, whiteflies, and mealybugs. The type species is Beet yellows virus.Bacteriophages: Viruses whose hosts are bacterial cells.Antibodies, Monoclonal: Antibodies produced by a single clone of cells.Viral Core Proteins: Proteins found mainly in icosahedral DNA and RNA viruses. They consist of proteins directly associated with the nucleic acid inside the NUCLEOCAPSID.Chenopodium quinoa: A species of the Chenopodium genus which is the source of edible seed called quinoa. It contains makisterone A and other STEROIDS, some having ECDYSTEROID activity on insects.Sapovirus: A genus of the family CALICIVIRIDAE associated with worldwide sporadic outbreaks of GASTROENTERITIS in humans. The first recorded outbreak was in human infants in Sapporo, Japan in 1977. The genus is comprised of a single species, Sapporo virus, containing multiple strains.Bovine papillomavirus 1: A species of DELTAPAPILLOMAVIRUS infecting cattle.Protein Biosynthesis: The biosynthesis of PEPTIDES and PROTEINS on RIBOSOMES, directed by MESSENGER RNA, via TRANSFER RNA that is charged with standard proteinogenic AMINO ACIDS.Semliki forest virus: A species of ALPHAVIRUS isolated in central, eastern, and southern Africa.Iridoviridae: A family of large icosahedral DNA viruses infecting insects and poikilothermic vertebrates. Genera include IRIDOVIRUS; RANAVIRUS; Chloriridovirus; Megalocytivirus; and Lymphocystivirus.Mutagenesis, Site-Directed: Genetically engineered MUTAGENESIS at a specific site in the DNA molecule that introduces a base substitution, or an insertion or deletion.Electrophoresis, Polyacrylamide Gel: Electrophoresis in which a polyacrylamide gel is used as the diffusion medium.Bacteriophage P2: A species of temperate bacteriophage in the genus P2-like viruses, family MYOVIRIDAE, which infects E. coli. It consists of linear double-stranded DNA with 19-base sticky ends.Circoviridae Infections: Virus diseases caused by the CIRCOVIRIDAE.Plasmids: Extrachromosomal, usually CIRCULAR DNA molecules that are self-replicating and transferable from one organism to another. They are found in a variety of bacterial, archaeal, fungal, algal, and plant species. They are used in GENETIC ENGINEERING as CLONING VECTORS.Foot-and-Mouth DiseaseParvovirus, Porcine: A species of PARVOVIRUS causing reproductive failure in pigs.Protein Processing, Post-Translational: Any of various enzymatically catalyzed post-translational modifications of PEPTIDES or PROTEINS in the cell of origin. These modifications include carboxylation; HYDROXYLATION; ACETYLATION; PHOSPHORYLATION; METHYLATION; GLYCOSYLATION; ubiquitination; oxidation; proteolysis; and crosslinking and result in changes in molecular weight and electrophoretic motility.Densovirus: A genus of PARVOVIRIDAE, subfamily DENSOVIRINAE, comprising helper-independent viruses containing only two species. Junonia coenia densovirus is the type species.Helminthosporium: A mitosporic fungal genus including both saprophytes and plant parasites.Protein Multimerization: The assembly of the QUATERNARY PROTEIN STRUCTURE of multimeric proteins (MULTIPROTEIN COMPLEXES) from their composite PROTEIN SUBUNITS.Viral Plaque Assay: Method for measuring viral infectivity and multiplication in CULTURED CELLS. Clear lysed areas or plaques develop as the VIRAL PARTICLES are released from the infected cells during incubation. With some VIRUSES, the cells are killed by a cytopathic effect; with others, the infected cells are not killed but can be detected by their hemadsorptive ability. Sometimes the plaque cells contain VIRAL ANTIGENS which can be measured by IMMUNOFLUORESCENCE.Polyomavirus Infections: Infections with POLYOMAVIRUS, which are often cultured from the urine of kidney transplant patients. Excretion of BK VIRUS is associated with ureteral strictures and CYSTITIS, and that of JC VIRUS with progressive multifocal leukoencephalopathy (LEUKOENCEPHALOPATHY, PROGRESSIVE MULTIFOCAL).Centrifugation, Density Gradient: Separation of particles according to density by employing a gradient of varying densities. At equilibrium each particle settles in the gradient at a point equal to its density. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Protein Structure, Quaternary: The characteristic 3-dimensional shape and arrangement of multimeric proteins (aggregates of more than one polypeptide chain).Plant Viruses: Viruses parasitic on plants higher than bacteria.Microscopy, Immunoelectron: Microscopy in which the samples are first stained immunocytochemically and then examined using an electron microscope. Immunoelectron microscopy is used extensively in diagnostic virology as part of very sensitive immunoassays.HIV Core Protein p24: A major core protein of the human immunodeficiency virus encoded by the HIV gag gene. HIV-seropositive individuals mount a significant immune response to p24 and thus detection of antibodies to p24 is one basis for determining HIV infection by ELISA and Western blot assays. The protein is also being investigated as a potential HIV immunogen in vaccines.Luteovirus: A genus of plant viruses that infects both monocotyledonous and dicotyledonous plants. Its organisms are persistently transmitted by aphids, and weeds may provide reservoirs of infection.Adenoviridae: A family of non-enveloped viruses infecting mammals (MASTADENOVIRUS) and birds (AVIADENOVIRUS) or both (ATADENOVIRUS). Infections may be asymptomatic or result in a variety of diseases.Rabbits: The species Oryctolagus cuniculus, in the family Leporidae, order LAGOMORPHA. Rabbits are born in burrows, furless, and with eyes and ears closed. In contrast with HARES, rabbits have 22 chromosome pairs.Peptides: Members of the class of compounds composed of AMINO ACIDS joined together by peptide bonds between adjacent amino acids into linear, branched or cyclical structures. OLIGOPEPTIDES are composed of approximately 2-12 amino acids. Polypeptides are composed of approximately 13 or more amino acids. PROTEINS are linear polypeptides that are normally synthesized on RIBOSOMES.Crystallography, X-Ray: The study of crystal structure using X-RAY DIFFRACTION techniques. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Human papillomavirus 16: A type of ALPHAPAPILLOMAVIRUS especially associated with malignant tumors of the CERVIX and the RESPIRATORY MUCOSA.Sequence Analysis, DNA: A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.Recombination, Genetic: 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.Enzyme-Linked Immunosorbent Assay: 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.Viral Nonstructural Proteins: Proteins encoded by a VIRAL GENOME that are produced in the organisms they infect, but not packaged into the VIRUS PARTICLES. Some of these proteins may play roles within the infected cell during VIRUS REPLICATION or act in regulation of virus replication or VIRUS ASSEMBLY.Mengovirus: A strain of ENCEPHALOMYOCARDITIS VIRUS, a species of CARDIOVIRUS, isolated from rodents and lagomorphs and occasionally causing febrile illness in man.Protein Structure, Secondary: The level of protein structure in which regular hydrogen-bond interactions within contiguous stretches of polypeptide chain give rise to alpha helices, beta strands (which align to form beta sheets) or other types of coils. This is the first folding level of protein conformation.Transduction, Genetic: The transfer of bacterial DNA by phages from an infected bacterium to another bacterium. This also refers to the transfer of genes into eukaryotic cells by viruses. This naturally occurring process is routinely employed as a GENE TRANSFER TECHNIQUE.Tumor Virus Infections: Infections produced by oncogenic viruses. The infections caused by DNA viruses are less numerous but more diverse than those caused by the RNA oncogenic viruses.Replicon: Any DNA sequence capable of independent replication or a molecule that possesses a REPLICATION ORIGIN and which is therefore potentially capable of being replicated in a suitable cell. (Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)Mason-Pfizer monkey virus: A species of BETARETROVIRUS isolated from mammary carcinoma in rhesus monkeys. It appears to have evolved from a recombination between a murine B oncovirus and a primate C oncovirus related to the baboon endogenous virus. Several serologically distinct strains exist. MPMV induces SIMIAN AIDS.Escherichia coli: A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.Vaccines, Virus-Like Particle: Vaccines using supra-molecular structures composed of multiple copies of recombinantly expressed viral structural proteins. They are often antigentically indistinguishable from the virus from which they were derived.Binding Sites: The parts of a macromolecule that directly participate in its specific combination with another molecule.Adenoviruses, Human: Species of the genus MASTADENOVIRUS, causing a wide range of diseases in humans. Infections are mostly asymptomatic, but can be associated with diseases of the respiratory, ocular, and gastrointestinal systems. Serotypes (named with Arabic numbers) have been grouped into species designated Human adenovirus A-F.Moths: Insects of the suborder Heterocera of the order LEPIDOPTERA.Vaccines, Synthetic: Small synthetic peptides that mimic surface antigens of pathogens and are immunogenic, or vaccines manufactured with the aid of recombinant DNA techniques. The latter vaccines may also be whole viruses whose nucleic acids have been modified.DNA Primers: Short sequences (generally about 10 base pairs) of DNA that are complementary to sequences of messenger RNA and allow reverse transcriptases to start copying the adjacent sequences of mRNA. Primers are used extensively in genetic and molecular biology techniques.RNA Virus InfectionsTransfection: The uptake of naked or purified DNA by CELLS, usually meaning the process as it occurs in eukaryotic cells. It is analogous to bacterial transformation (TRANSFORMATION, BACTERIAL) and both are routinely employed in GENE TRANSFER TECHNIQUES.RNA, Double-Stranded: RNA consisting of two strands as opposed to the more prevalent single-stranded RNA. Most of the double-stranded segments are formed from transcription of DNA by intramolecular base-pairing of inverted complementary sequences separated by a single-stranded loop. Some double-stranded segments of RNA are normal in all organisms.Molecular Weight: The sum of the weight of all the atoms in a molecule.Tobacco: A plant genus of the family SOLANACEAE. Members contain NICOTINE and other biologically active chemicals; its dried leaves are used for SMOKING.Helper Viruses: Viruses which enable defective viruses to replicate or to form a protein coat by complementing the missing gene function of the defective (satellite) virus. Helper and satellite may be of the same or different genus.Endopeptidases: A subclass of PEPTIDE HYDROLASES that catalyze the internal cleavage of PEPTIDES or PROTEINS.Hepatitis A Antigens: Antigens produced by various strains of HEPATITIS A VIRUS such as the human hepatitis A virus (HEPATITIS A VIRUS, HUMAN).Negative Staining: The technique of washing tissue specimens with a concentrated solution of a heavy metal salt and letting it dry. The specimen will be covered with a very thin layer of the metal salt, being excluded in areas where an adsorbed macromolecule is present. The macromolecules allow electrons from the beam of an electron microscope to pass much more readily than the heavy metal; thus, a reversed or negative image of the molecule is created.Sequence Deletion: Deletion of sequences of nucleic acids from the genetic material of an individual.Bacteriophage PRD1: Bacteriophage and type species in the genus Tectivirus, family TECTIVIRIDAE. They are specific for Gram-negative bacteria.Mutant Proteins: Proteins produced from GENES that have acquired MUTATIONS.Nuclear Localization Signals: Short, predominantly basic amino acid sequences identified as nuclear import signals for some proteins. These sequences are believed to interact with specific receptors at the NUCLEAR PORE.Virulence: 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.Serotyping: Process of determining and distinguishing species of bacteria or viruses based on antigens they share.Encephalitis Virus, Venezuelan Equine: A species of ALPHAVIRUS that is the etiologic agent of encephalomyelitis in humans and equines. It is seen most commonly in parts of Central and South America.Viruses: Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells.Plum Pox Virus: A species of the genus POTYVIRUS that affects many species of Prunus. It is transmitted by aphids and by infected rootstocks.Rotavirus Infections: Infection with any of the rotaviruses. Specific infections include human infantile diarrhea, neonatal calf diarrhea, and epidemic diarrhea of infant mice.Reoviridae Infections: Infections produced by reoviruses, general or unspecified.Birnaviridae: A family of bisegmented, double-stranded RNA viruses causing infection in fish, mollusks, fowl, and Drosophila. There are three genera: AQUABIRNAVIRUS; AVIBIRNAVIRUS; and ENTOMOBIRNAVIRUS. Horizontal and vertical transmission occurs for all viruses.Gastroenteritis: INFLAMMATION of any segment of the GASTROINTESTINAL TRACT from ESOPHAGUS to RECTUM. Causes of gastroenteritis are many including genetic, infection, HYPERSENSITIVITY, drug effects, and CANCER.Blotting, Western: Identification of proteins or peptides that have been electrophoretically separated by blot transferring from the electrophoresis gel to strips of nitrocellulose paper, followed by labeling with antibody probes.Cytoplasm: The part of a cell that contains the CYTOSOL and small structures excluding the CELL NUCLEUS; MITOCHONDRIA; and large VACUOLES. (Glick, Glossary of Biochemistry and Molecular Biology, 1990)Cells, Cultured: Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.Simplexvirus: A genus of the family HERPESVIRIDAE, subfamily ALPHAHERPESVIRINAE, consisting of herpes simplex-like viruses. The type species is HERPESVIRUS 1, HUMAN.Myoviridae: A family of BACTERIOPHAGES and ARCHAEAL VIRUSES which are characterized by complex contractile tails.Species Specificity: 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.Alphavirus: A genus of TOGAVIRIDAE, also known as Group A arboviruses, serologically related to each other but not to other Togaviridae. The viruses are transmitted by mosquitoes. The type species is the SINDBIS VIRUS.Mice, Inbred BALB CEpitopes, B-Lymphocyte: Antigenic determinants recognized and bound by the B-cell receptor. Epitopes recognized by the B-cell receptor are located on the surface of the antigen.Hepatitis B virus: The type species of the genus ORTHOHEPADNAVIRUS which causes human HEPATITIS B and is also apparently a causal agent in human HEPATOCELLULAR CARCINOMA. The Dane particle is an intact hepatitis virion, named after its discoverer. Non-infectious spherical and tubular particles are also seen in the serum.Orbivirus: A genus of REOVIRIDAE infecting a wide range of arthropods and vertebrates including humans. It comprises at least 21 serological subgroups. Transmission is by vectors such as midges, mosquitoes, sandflies, and ticks.