Protozoan Vaccines: Suspensions of attenuated or killed protozoa administered for the prevention or treatment of infectious protozoan disease.Vaccines: Suspensions of killed or attenuated microorganisms (bacteria, viruses, fungi, protozoa), antigenic proteins, synthetic constructs, or other bio-molecular derivatives, administered for the prevention, amelioration, or treatment of infectious and other diseases.Vaccines, Inactivated: Vaccines in which the infectious microbial nucleic acid components have been destroyed by chemical or physical treatment (e.g., formalin, beta-propiolactone, gamma radiation) without affecting the antigenicity or immunogenicity of the viral coat or bacterial outer membrane proteins.Viral Vaccines: Suspensions of attenuated or killed viruses administered for the prevention or treatment of infectious viral disease.Protozoan Infections: Infections with unicellular organisms formerly members of the subkingdom Protozoa.Vaccines, Combined: Two or more vaccines in a single dosage form.Vaccines, DNA: Recombinant DNA vectors encoding antigens administered for the prevention or treatment of disease. The host cells take up the DNA, express the antigen, and present it to the immune system in a manner similar to that which would occur during natural infection. This induces humoral and cellular immune responses against the encoded antigens. The vector is called naked DNA because there is no need for complex formulations or delivery agents; the plasmid is injected in saline or other buffers.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.Bacterial Vaccines: Suspensions of attenuated or killed bacteria administered for the prevention or treatment of infectious bacterial disease.AIDS Vaccines: Vaccines or candidate vaccines containing inactivated HIV or some of its component antigens and designed to prevent or treat AIDS. Some vaccines containing antigens are recombinantly produced.Vaccines, Subunit: Vaccines consisting of one or more antigens that stimulate a strong immune response. They are purified from microorganisms or produced by recombinant DNA techniques, or they can be chemically synthesized peptides.Vaccines, Conjugate: Semisynthetic vaccines consisting of polysaccharide antigens from microorganisms attached to protein carrier molecules. The carrier protein is recognized by macrophages and T-cells thus enhancing immunity. Conjugate vaccines induce antibody formation in people not responsive to polysaccharide alone, induce higher levels of antibody, and show a booster response on repeated injection.Protozoan Proteins: Proteins found in any species of protozoan.Vaccination: Administration of vaccines to stimulate the host's immune response. This includes any preparation intended for active immunological prophylaxis.Malaria Vaccines: Vaccines made from antigens arising from any of the four strains of Plasmodium which cause malaria in humans, or from P. berghei which causes malaria in rodents.Papillomavirus Vaccines: Vaccines or candidate vaccines used to prevent PAPILLOMAVIRUS INFECTIONS. Human vaccines are intended to reduce the incidence of UTERINE CERVICAL NEOPLASMS, so they are sometimes considered a type of CANCER VACCINES. They are often composed of CAPSID PROTEINS, especially L1 protein, from various types of ALPHAPAPILLOMAVIRUS.Eukaryota: 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.DNA, Protozoan: Deoxyribonucleic acid that makes up the genetic material of protozoa.Meningococcal Vaccines: Vaccines or candidate vaccines used to prevent infection with NEISSERIA MENINGITIDIS.Ciliophora: A phylum of EUKARYOTES characterized by the presence of cilia at some time during the life cycle. It comprises three classes: KINETOFRAGMINOPHOREA; OLIGOHYMENOPHOREA; and POLYMENOPHOREA.Hepatitis B Vaccines: Vaccines or candidate vaccines containing inactivated hepatitis B or some of its component antigens and designed to prevent hepatitis B. Some vaccines may be recombinantly produced.Measles Vaccine: A live attenuated virus vaccine of chick embryo origin, used for routine immunization of children and for immunization of adolescents and adults who have not had measles or been immunized with live measles vaccine and have no serum antibodies against measles. Children are usually immunized with measles-mumps-rubella combination vaccine. (From Dorland, 28th ed)Genes, Protozoan: The functional hereditary units of protozoa.Pertussis Vaccine: A suspension of killed Bordetella pertussis organisms, used for immunization against pertussis (WHOOPING COUGH). It is generally used in a mixture with diphtheria and tetanus toxoids (DTP). There is an acellular pertussis vaccine prepared from the purified antigenic components of Bordetella pertussis, which causes fewer adverse reactions than whole-cell vaccine and, like the whole-cell vaccine, is generally used in a mixture with diphtheria and tetanus toxoids. (From Dorland, 28th ed)RNA, Protozoan: Ribonucleic acid in protozoa having regulatory and catalytic roles as well as involvement in protein synthesis.Haemophilus Vaccines: Vaccines or candidate vaccines containing antigenic polysaccharides from Haemophilus influenzae and designed to prevent infection. The vaccine can contain the polysaccharides alone or more frequently polysaccharides conjugated to carrier molecules. It is also seen as a combined vaccine with diphtheria-tetanus-pertussis vaccine.BCG Vaccine: An active immunizing agent and a viable avirulent attenuated strain of Mycobacterium tuberculosis, var. bovis, which confers immunity to mycobacterial infections. It is used also in immunotherapy of neoplasms due to its stimulation of antibodies and non-specific immunity.Poliovirus Vaccine, Inactivated: A suspension of formalin-inactivated poliovirus grown in monkey kidney cell tissue culture and used to prevent POLIOMYELITIS.Rabies Vaccines: Vaccines or candidate vaccines used to prevent and treat RABIES. The inactivated virus vaccine is used for preexposure immunization to persons at high risk of exposure, and in conjunction with rabies immunoglobulin, for postexposure prophylaxis.Rotavirus Vaccines: Vaccines or candidate vaccines used to prevent infection with ROTAVIRUS.Cholera Vaccines: Vaccines or candidate vaccines used to prevent infection with VIBRIO CHOLERAE. The original cholera vaccine consisted of killed bacteria, but other kinds of vaccines now exist.Typhoid-Paratyphoid Vaccines: Vaccines used to prevent TYPHOID FEVER and/or PARATYPHOID FEVER which are caused by various species of SALMONELLA. Attenuated, subunit, and inactivated forms of the vaccines exist.Smallpox Vaccine: A live VACCINIA VIRUS vaccine of calf lymph or chick embryo origin, used for immunization against smallpox. It is now recommended only for laboratory workers exposed to smallpox virus. Certain countries continue to vaccinate those in the military service. Complications that result from smallpox vaccination include vaccinia, secondary bacterial infections, and encephalomyelitis. (Dorland, 28th ed)Tuberculosis Vaccines: Vaccines or candidate vaccines used to prevent or treat TUBERCULOSIS.Antibodies, Viral: Immunoglobulins produced in response to VIRAL ANTIGENS.Genome, Protozoan: The complete genetic complement contained in a set of CHROMOSOMES in a protozoan.Chickenpox Vaccine: A live, attenuated varicella virus vaccine used for immunization against chickenpox. It is recommended for children between the ages of 12 months and 13 years.Diphtheria-Tetanus-Pertussis Vaccine: A vaccine consisting of DIPHTHERIA TOXOID; TETANUS TOXOID; and whole-cell PERTUSSIS VACCINE. The vaccine protects against diphtheria, tetanus, and whooping cough.Protozoan Infections, Animal: Infections with unicellular organisms formerly members of the subkingdom Protozoa. The infections may be experimental or veterinary.Mumps Vaccine: Vaccines used to prevent infection by MUMPS VIRUS. Best known is the live attenuated virus vaccine of chick embryo origin, used for routine immunization of children and for immunization of adolescents and adults who have not had mumps or been immunized with live mumps vaccine. Children are usually immunized with measles-mumps-rubella combination vaccine.Hepatitis A Vaccines: Vaccines or candidate vaccines used to prevent infection with hepatitis A virus (HEPATOVIRUS).Immunization Schedule: Schedule giving optimum times usually for primary and/or secondary immunization.Adjuvants, Immunologic: Substances that augment, stimulate, activate, potentiate, or modulate the immune response at either the cellular or humoral level. The classical agents (Freund's adjuvant, BCG, Corynebacterium parvum, et al.) contain bacterial antigens. Some are endogenous (e.g., histamine, interferon, transfer factor, tuftsin, interleukin-1). Their mode of action is either non-specific, resulting in increased immune responsiveness to a wide variety of antigens, or antigen-specific, i.e., affecting a restricted type of immune response to a narrow group of antigens. The therapeutic efficacy of many biological response modifiers is related to their antigen-specific immunoadjuvanticity.Immunization, Secondary: Any immunization following a primary immunization and involving exposure to the same or a closely related antigen.Measles-Mumps-Rubella Vaccine: A combined vaccine used to prevent MEASLES; MUMPS; and RUBELLA.Streptococcal Vaccines: Vaccines or candidate vaccines used to prevent STREPTOCOCCAL INFECTIONS.Anthrax Vaccines: Vaccines or candidate vaccines used to prevent ANTHRAX.Antigens, Protozoan: Any part or derivative of any protozoan that elicits immunity; malaria (Plasmodium) and trypanosome antigens are presently the most frequently encountered.Dengue Vaccines: Vaccines or candidate vaccines used to prevent infection with DENGUE VIRUS. These include live-attenuated, subunit, DNA, and inactivated vaccines.Vaccines, Virosome: Vaccines using VIROSOMES as the antigen delivery system that stimulates the desired immune response.Immunization: Deliberate stimulation of the host's immune response. ACTIVE IMMUNIZATION involves administration of ANTIGENS or IMMUNOLOGIC ADJUVANTS. PASSIVE IMMUNIZATION involves administration of IMMUNE SERA or LYMPHOCYTES or their extracts (e.g., transfer factor, immune RNA) or transplantation of immunocompetent cell producing tissue (thymus or bone marrow).Entamoeba histolytica: A species of parasitic protozoa causing ENTAMOEBIASIS and amebic dysentery (DYSENTERY, AMEBIC). Characteristics include a single nucleus containing a small central karyosome and peripheral chromatin that is finely and regularly beaded.Viral Hepatitis Vaccines: Any vaccine raised against any virus or viral derivative that causes hepatitis.Poliovirus Vaccine, Oral: A live vaccine containing attenuated poliovirus, types I, II, and III, grown in monkey kidney cell tissue culture, used for routine immunization of children against polio. This vaccine induces long-lasting intestinal and humoral immunity. Killed vaccine induces only humoral immunity. Oral poliovirus vaccine should not be administered to immunocompromised individuals or their household contacts. (Dorland, 28th ed)Mice, Inbred BALB CYellow Fever Vaccine: Vaccine used to prevent YELLOW FEVER. It consists of a live attenuated 17D strain of the YELLOW FEVER VIRUS.Antibodies, Bacterial: Immunoglobulins produced in a response to BACTERIAL ANTIGENS.Plague Vaccine: A suspension of killed Yersinia pestis used for immunizing people in enzootic plague areas.Giardia lamblia: 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.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.Fungal Vaccines: Suspensions of attenuated or killed fungi administered for the prevention or treatment of infectious fungal disease.Trypanosoma cruzi: The agent of South American trypanosomiasis or CHAGAS DISEASE. Its vertebrate hosts are man and various domestic and wild animals. Insects of several species are vectors.Rubella Vaccine: A live attenuated virus vaccine of duck embryo or human diploid cell tissue culture origin, used for routine immunization of children and for immunization of nonpregnant adolescent and adult females of childbearing age who are unimmunized and do not have serum antibodies to rubella. Children are usually immunized with measles-mumps-rubella combination vaccine. (Dorland, 28th ed)Leishmania: A genus of flagellate protozoa comprising several species that are pathogenic for humans. Organisms of this genus have an amastigote and a promastigote stage in their life cycles. As a result of enzymatic studies this single genus has been divided into two subgenera: Leishmania leishmania and Leishmania viannia. Species within the Leishmania leishmania subgenus include: L. aethiopica, L. arabica, L. donovani, L. enrietti, L. gerbilli, L. hertigi, L. infantum, L. major, L. mexicana, and L. tropica. The following species are those that compose the Leishmania viannia subgenus: L. braziliensis, L. guyanensis, L. lainsoni, L. naiffi, and L. shawi.Vaccines, Acellular: Vaccines that are produced by using only the antigenic part of the disease causing organism. They often require a "booster" every few years to maintain their effectiveness.SAIDS Vaccines: Vaccines or candidate vaccines designed to prevent SAIDS; (SIMIAN ACQUIRED IMMUNODEFICIENCY SYNDROME); and containing inactivated SIMIAN IMMUNODEFICIENCY VIRUS or type D retroviruses or some of their component antigens.Salmonella Vaccines: Vaccines or candidate vaccines used to prevent infection with SALMONELLA. This includes vaccines used to prevent TYPHOID FEVER or PARATYPHOID FEVER; (TYPHOID-PARATYPHOID VACCINES), and vaccines used to prevent nontyphoid salmonellosis.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.Toxoplasma: A genus of protozoa parasitic to birds and mammals. T. gondii is one of the most common infectious pathogenic animal parasites of man.Ebola Vaccines: Vaccines or candidate vaccines used to prevent EBOLA HEMORRHAGIC FEVER.Influenza, Human: An acute viral infection in humans involving the respiratory tract. It is marked by inflammation of the NASAL MUCOSA; the PHARYNX; and conjunctiva, and by headache and severe, often generalized, myalgia.Alveolata: A group of three related eukaryotic phyla whose members possess an alveolar membrane system, consisting of flattened membrane-bound sacs lying beneath the outer cell membrane.Antiprotozoal Agents: Substances that are destructive to protozoans.Tetrahymena pyriformis: A species of ciliate protozoa used extensively in genetic research.Apicomplexa: A phylum of unicellular parasitic EUKARYOTES characterized by the presence of complex apical organelles generally consisting of a conoid that aids in penetrating host cells, rhoptries that possibly secrete a proteolytic enzyme, and subpellicular microtubules that may be related to motility.Antibodies, Neutralizing: Antibodies that reduce or abolish some biological activity of a soluble antigen or infectious agent, usually a virus.Staphylococcal VaccinesDiphtheria-Tetanus-acellular Pertussis Vaccines: Combined vaccines consisting of DIPHTHERIA TOXOID; TETANUS TOXOID; and an acellular form of PERTUSSIS VACCINE. At least five different purified antigens of B. pertussis have been used in various combinations in these vaccines.Kinetoplastida: An order of flagellate protozoa. Characteristics include the presence of one or two flagella arising from a depression in the cell body and a single mitochondrion that extends the length of the body.Trypanosoma: A genus of flagellate protozoans found in the blood and lymph of vertebrates and invertebrates, both hosts being required to complete the life cycle.Cytomegalovirus Vaccines: Vaccines or candidate vaccines used to prevent infection with CYTOMEGALOVIRUS.Trypanosoma brucei brucei: 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).Immunization Programs: Organized services to administer immunization procedures in the prevention of various diseases. The programs are made available over a wide range of sites: schools, hospitals, public health agencies, voluntary health agencies, etc. They are administered to an equally wide range of population groups or on various administrative levels: community, municipal, state, national, international.Intestinal Diseases, Parasitic: Infections of the INTESTINES with PARASITES, commonly involving PARASITIC WORMS. Infections with roundworms (NEMATODE INFECTIONS) and tapeworms (CESTODE INFECTIONS) are also known as HELMINTHIASIS.Injections, Intramuscular: Forceful administration into a muscle of liquid medication, nutrient, or other fluid through a hollow needle piercing the muscle and any tissue covering it.Immunoglobulin G: The major immunoglobulin isotype class in normal human serum. There are several isotype subclasses of IgG, for example, IgG1, IgG2A, and IgG2B.Diphtheria-Tetanus Vaccine: A combined vaccine used to prevent infection with diphtheria and tetanus toxoid. This is used in place of DTP vaccine (DIPHTHERIA-TETANUS-PERTUSSIS VACCINE) when PERTUSSIS VACCINE is contraindicated.Poliovirus Vaccines: Vaccines used to prevent POLIOMYELITIS. They include inactivated (POLIOVIRUS VACCINE, INACTIVATED) and oral vaccines (POLIOVIRUS VACCINE, ORAL).Administration, Intranasal: Delivery of medications through the nasal mucosa.Escherichia coli Vaccines: Vaccines or candidate vaccines used to prevent or treat both enterotoxigenic and enteropathogenic Escherichia coli infections.West Nile Virus Vaccines: Vaccines or candidate vaccines used to prevent infection with WEST NILE VIRUS.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.Trypanosomatina: A suborder of monoflagellate parasitic protozoa that lives in the blood and tissues of man and animals. Representative genera include: Blastocrithidia, Leptomonas, CRITHIDIA, Herpetomonas, LEISHMANIA, Phytomonas, and TRYPANOSOMA. Species of this suborder may exist in two or more morphologic stages formerly named after genera exemplifying these forms - amastigote (LEISHMANIA), choanomastigote (CRITHIDIA), promastigote (Leptomonas), opisthomastigote (Herpetomonas), epimastigote (Blastocrithidia), and trypomastigote (TRYPANOSOMA).Leishmania major: A parasitic hemoflagellate of the subgenus Leishmania leishmania that infects man and animals and causes cutaneous leishmaniasis (LEISHMANIASIS, CUTANEOUS) of the Old World. Transmission is by Phlebotomus sandflies.Hemagglutination Inhibition Tests: 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.Shigella Vaccines: Vaccines or candidate vaccines used to prevent bacillary dysentery (DYSENTERY, BACILLARY) caused by species of SHIGELLA.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).Parasites: Invertebrate organisms that live on or in another organism (the host), and benefit at the expense of the other. Traditionally excluded from definition of parasites are pathogenic BACTERIA; FUNGI; VIRUSES; and PLANTS; though they may live parasitically.Trichomonas: A genus of parasitic flagellate EUKARYOTES distinguished by the presence of four anterior flagella, an undulating membrane, and a trailing flagellum.Antibody Formation: The production of ANTIBODIES by proliferating and differentiated B-LYMPHOCYTES under stimulation by ANTIGENS.Leishmaniasis Vaccines: Vaccines or candidate vaccines used to prevent infection with LEISHMANIA.Herpes Zoster Vaccine: An attenuated vaccine used to prevent and/or treat HERPES ZOSTER, a disease caused by HUMAN HERPESVIRUS 3.Polysorbates: Sorbitan mono-9-octadecanoate poly(oxy-1,2-ethanediyl) derivatives; complex mixtures of polyoxyethylene ethers used as emulsifiers or dispersing agents in pharmaceuticals.Hartmannella: A genus of free-living amoebae found in fresh water. The cysts usually pass harmlessly through the intestinal tract of man and may thus be found in feces. Occasionally, these organisms cause respiratory tract infections or generalized fatal meningoencephalitis.Immunity, Humoral: Antibody-mediated immune response. Humoral immunity is brought about by ANTIBODY FORMATION, resulting from TH2 CELLS activating B-LYMPHOCYTES, followed by COMPLEMENT ACTIVATION.Brucella Vaccine: A bacterial vaccine for the prevention of brucellosis in man and animal. Brucella abortus vaccine is used for the immunization of cattle, sheep, and goats.Crithidia: A genus of parasitic protozoans found in the digestive tract of invertebrates, especially insects. Organisms of this genus have an amastigote and choanomastigote stage in their life cycle.Rumen: The first stomach of ruminants. It lies on the left side of the body, occupying the whole of the left side of the abdomen and even stretching across the median plane of the body to the right side. It is capacious, divided into an upper and a lower sac, each of which has a blind sac at its posterior extremity. The rumen is lined by mucous membrane containing no digestive glands, but mucus-secreting glands are present in large numbers. Coarse, partially chewed food is stored and churned in the rumen until the animal finds circumstances convenient for rumination. When this occurs, little balls of food are regurgitated through the esophagus into the mouth, and are subjected to a second more thorough mastication, swallowed, and passed on into other parts of the compound stomach. (From Black's Veterinary Dictionary, 17th ed)Tetanus ToxoidTrichomonas vaginalis: A species of TRICHOMONAS that produces a refractory vaginal discharge in females, as well as bladder and urethral infections in males.Herpesvirus Vaccines: Vaccines or candidate vaccines used to prevent infection by any virus from the family HERPESVIRIDAE.Entamoeba: A genus of ameboid protozoa characterized by the presence of beaded chromatin on the inner surface of the nuclear membrane. Its organisms are parasitic in invertebrates and vertebrates, including humans.Injections, Intradermal: The forcing into the skin of liquid medication, nutrient, or other fluid through a hollow needle, piercing the top skin layer.Aluminum Hydroxide: A compound with many biomedical applications: as a gastric antacid, an antiperspirant, in dentifrices, as an emulsifier, as an adjuvant in bacterins and vaccines, in water purification, etc.Influenza A Virus, H1N1 Subtype: A subtype of INFLUENZA A VIRUS with the surface proteins hemagglutinin 1 and neuraminidase 1. The H1N1 subtype was responsible for the Spanish flu pandemic of 1918.Alum Compounds: Aluminum metal sulfate compounds used medically as astringents and for many industrial purposes. They are used in veterinary medicine for the treatment of ulcerative stomatitis, leukorrhea, conjunctivitis, pharyngitis, metritis, and minor wounds.Herpes Simplex Virus Vaccines: Vaccines or candidate vaccines used to prevent infection with viruses from the genus SIMPLEXVIRUS. This includes vaccines for HSV-1 and HSV-2.Antigens, Bacterial: Substances elaborated by bacteria that have antigenic activity.Diphtheria Toxoid: The formaldehyde-inactivated toxin of Corynebacterium diphtheriae. It is generally used in mixtures with TETANUS TOXOID and PERTUSSIS VACCINE; (DTP); or with tetanus toxoid alone (DT for pediatric use and Td, which contains 5- to 10-fold less diphtheria toxoid, for other use). Diphtheria toxoid is used for the prevention of diphtheria; DIPHTHERIA ANTITOXIN is for treatment.SqualeneLeishmania donovani: A parasitic hemoflagellate of the subgenus Leishmania leishmania that infects man and animals and causes visceral leishmaniasis (LEISHMANIASIS, VISCERAL). The sandfly genera Phlebotomus and Lutzomyia are the vectors.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.Respiratory Syncytial Virus Vaccines: Vaccines or candidate vaccines used to prevent infection with RESPIRATORY SYNCYTIAL VIRUSES.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.CD8-Positive T-Lymphocytes: A critical subpopulation of regulatory T-lymphocytes involved in MHC Class I-restricted interactions. They include both cytotoxic T-lymphocytes (T-LYMPHOCYTES, CYTOTOXIC) and CD8+ suppressor T-lymphocytes.Giardiasis: 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.Immunity, Cellular: Manifestations of the immune response which are mediated by antigen-sensitized T-lymphocytes via lymphokines or direct cytotoxicity. This takes place in the absence of circulating antibody or where antibody plays a subordinate role.Cross Protection: Protection conferred on a host by inoculation with one strain or component of a microorganism that prevents infection when later challenged with a similar strain. Most commonly the microorganism is a virus.Coccidiosis: Protozoan infection found in animals and man. It is caused by several different genera of COCCIDIA.Japanese Encephalitis Vaccines: Vaccines or candidate vaccines used to prevent infection with Japanese B encephalitis virus (ENCEPHALITIS VIRUS, JAPANESE).Mass Vaccination: Administration of a vaccine to large populations in order to elicit IMMUNITY.Host-Parasite Interactions: 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.Vaccines, Contraceptive: Vaccines or candidate vaccines used to prevent conception.Interferon-gamma: The major interferon produced by mitogenically or antigenically stimulated LYMPHOCYTES. It is structurally different from TYPE I INTERFERON and its major activity is immunoregulation. It has been implicated in the expression of CLASS II HISTOCOMPATIBILITY ANTIGENS in cells that do not normally produce them, leading to AUTOIMMUNE DISEASES.Vaccines, Edible: Vaccines or candidate vaccines derived from edible plants. Transgenic plants (PLANTS, TRANSGENIC) are used as recombinant protein production systems and the edible plant tissue functions as an oral vaccine.Acanthamoeba: A genus of free-living soil amoebae that produces no flagellate stage. Its organisms are pathogens for several infections in humans and have been found in the eye, bone, brain, and respiratory tract.Mice, Inbred C57BLCryptosporidium: A genus of coccidian parasites of the family CRYPTOSPORIDIIDAE, found in the intestinal epithelium of many vertebrates including humans.Amoebozoa: A supergroup (some say phylum) of ameboid EUKARYOTES, comprising ARCHAMOEBAE; LOBOSEA; and MYCETOZOA.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Cross Reactions: Serological reactions in which an antiserum against one antigen reacts with a non-identical but closely related antigen.Cryptosporidium parvum: A species of parasitic protozoa that infects humans and most domestic mammals. Its oocysts measure five microns in diameter. These organisms exhibit alternating cycles of sexual and asexual reproduction.Leishmania mexicana: A parasitic hemoflagellate of the subgenus Leishmania leishmania that infects man and animals including rodents. The Leishmania mexicana complex causes both cutaneous (LEISHMANIASIS, CUTANEOUS) and diffuse cutaneous leishmaniasis (LEISHMANIASIS, DIFFUSE CUTANEOUS) and includes the subspecies amazonensis, garnhami, mexicana, pifanoi, and venezuelensis. L. m. mexicana causes chiclero ulcer, a form of cutaneous leishmaniasis (LEISHMANIASIS, CUTANEOUS) in the New World. The sandfly, Lutzomyia, appears to be the vector.Antibodies, Protozoan: Immunoglobulins produced in a response to PROTOZOAN ANTIGENS.Whooping Cough: A respiratory infection caused by BORDETELLA PERTUSSIS and characterized by paroxysmal coughing ending in a prolonged crowing intake of breath.Spores, Protozoan: A vegetative stage in the life cycle of sporozoan protozoa. It is characteristic of members of the phyla APICOMPLEXA and MICROSPORIDIA.Immunotherapy, Active: Active immunization where vaccine is administered for therapeutic or preventive purposes. This can include administration of immunopotentiating agents such as BCG vaccine and Corynebacterium parvum as well as biological response modifiers such as interferons, interleukins, and colony-stimulating factors in order to directly stimulate the immune system.Blastocystis hominis: A species of parasitic protozoa found in the intestines of humans and other primates. It was classified as a yeast in 1912. Over the years, questions arose about this designation. In 1967, many physiological and morphological B. hominis characteristics were reported that fit a protozoan classification. Since that time, other papers have corroborated this work and the organism is now recognized as a protozoan parasite of humans causing intestinal disease with potentially disabling symptoms.Vaccine Potency: The relationship between an elicited ADAPTIVE IMMUNE RESPONSE and the dose of the vaccine administered.Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Feces: Excrement from the INTESTINES, containing unabsorbed solids, waste products, secretions, and BACTERIA of the DIGESTIVE SYSTEM.Sarcocystosis: Infection of the striated muscle of mammals by parasites of the genus SARCOCYSTIS. Disease symptoms such as vomiting, diarrhea, muscle weakness, and paralysis are produced by sarcocystin, a toxin produced by the organism.Measles: A highly contagious infectious disease caused by MORBILLIVIRUS, common among children but also seen in the nonimmune of any age, in which the virus enters the respiratory tract via droplet nuclei and multiplies in the epithelial cells, spreading throughout the MONONUCLEAR PHAGOCYTE SYSTEM.Plasmodium falciparum: A species of protozoa that is the causal agent of falciparum malaria (MALARIA, FALCIPARUM). It is most prevalent in the tropics and subtropics.Rickettsial Vaccines: Vaccines for the prevention of diseases caused by various species of Rickettsia.Smallpox: An acute, highly contagious, often fatal infectious disease caused by an orthopoxvirus characterized by a biphasic febrile course and distinctive progressive skin eruptions. Vaccination has succeeded in eradicating smallpox worldwide. (Dorland, 28th ed)Helminths: Commonly known as parasitic worms, this group includes the ACANTHOCEPHALA; NEMATODA; and PLATYHELMINTHS. Some authors consider certain species of LEECHES that can become temporarily parasitic as helminths.Eimeria: A genus of protozoan parasites of the subclass COCCIDIA. Various species are parasitic in the epithelial cells of the liver and intestines of man and other animals.Parainfluenza Vaccines: Vaccines or candidate vaccines used to prevent infection with parainfluenza viruses in humans and animals.T-Lymphocytes: Lymphocytes responsible for cell-mediated immunity. Two types have been identified - cytotoxic (T-LYMPHOCYTES, CYTOTOXIC) and helper T-lymphocytes (T-LYMPHOCYTES, HELPER-INDUCER). They are formed when lymphocytes circulate through the THYMUS GLAND and differentiate to thymocytes. When exposed to an antigen, they divide rapidly and produce large numbers of new T cells sensitized to that antigen.Legionella pneumophila: A species of gram-negative, aerobic bacteria that is the causative agent of LEGIONNAIRES' DISEASE. It has been isolated from numerous environmental sites as well as from human lung tissue, respiratory secretions, and blood.Parasitic Diseases: Infections or infestations with parasitic organisms. They are often contracted through contact with an intermediate vector, but may occur as the result of direct exposure.Immunity, Mucosal: Nonsusceptibility to the pathogenic effects of foreign microorganisms or antigenic substances as a result of antibody secretions of the mucous membranes. Mucosal epithelia in the gastrointestinal, respiratory, and reproductive tracts produce a form of IgA (IMMUNOGLOBULIN A, SECRETORY) that serves to protect these ports of entry into the body.CD4-Positive T-Lymphocytes: A critical subpopulation of T-lymphocytes involved in the induction of most immunological functions. The HIV virus has selective tropism for the T4 cell which expresses the CD4 phenotypic marker, a receptor for HIV. In fact, the key element in the profound immunosuppression seen in HIV infection is the depletion of this subset of T-lymphocytes.Theileria parva: A protozoan parasite that is the etiologic agent of East Coast fever (THEILERIASIS). Transmission is by ticks of the Physicephalus and Hyalomma genera.Plasmodium: 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.Tetrahymena: A genus of ciliate protozoa commonly used in genetic, cytological, and other research.Cryptosporidiosis: Intestinal infection with organisms of the genus CRYPTOSPORIDIUM. It occurs in both animals and humans. Symptoms include severe DIARRHEA.Rotavirus Infections: Infection with any of the rotaviruses. Specific infections include human infantile diarrhea, neonatal calf diarrhea, and epidemic diarrhea of infant mice.Influenza A Virus, H5N1 Subtype: A subtype of INFLUENZA A VIRUS comprised of the surface proteins hemagglutinin 5 and neuraminidase 1. The H5N1 subtype, frequently referred to as the bird flu virus, is endemic in wild birds and very contagious among both domestic (POULTRY) and wild birds. It does not usually infect humans, but some cases have been reported.Influenza A Virus, H3N2 Subtype: A subtype of INFLUENZA A VIRUS comprised of the surface proteins hemagglutinin 3 and neuraminidase 2. The H3N2 subtype was responsible for the Hong Kong flu pandemic of 1968.Influenza B virus: Species of the genus INFLUENZAVIRUS B that cause HUMAN INFLUENZA and other diseases primarily in humans. Antigenic variation is less extensive than in type A viruses (INFLUENZA A VIRUS) and consequently there is no basis for distinct subtypes or variants. Epidemics are less likely than with INFLUENZA A VIRUS and there have been no pandemics. Previously only found in humans, Influenza B virus has been isolated from seals which may constitute the animal reservoir from which humans are exposed.Toxoplasmosis: The acquired form of infection by Toxoplasma gondii in animals and man.Pseudorabies Vaccines: Vaccines or candidate vaccines used to prevent PSEUDORABIES (Aujeszky's disease), a herpesvirus of swine and other animals.Acanthamoeba castellanii: A species of free-living soil amoebae in the family Acanthamoebidae. It can cause ENCEPHALITIS and KERATITIS in humans.Macaca mulatta: A species of the genus MACACA inhabiting India, China, and other parts of Asia. The species is used extensively in biomedical research and adapts very well to living with humans.Vaccinia virus: The type species of ORTHOPOXVIRUS, related to COWPOX VIRUS, but whose true origin is unknown. It has been used as a live vaccine against SMALLPOX. It is also used as a vector for inserting foreign DNA into animals. Rabbitpox virus is a subspecies of VACCINIA VIRUS.T-Lymphocytes, Cytotoxic: Immunized T-lymphocytes which can directly destroy appropriate target cells. These cytotoxic lymphocytes may be generated in vitro in mixed lymphocyte cultures (MLC), in vivo during a graft-versus-host (GVH) reaction, or after immunization with an allograft, tumor cell or virally transformed or chemically modified target cell. The lytic phenomenon is sometimes referred to as cell-mediated lympholysis (CML). These CD8-positive cells are distinct from NATURAL KILLER CELLS and NATURAL KILLER T-CELLS. There are two effector phenotypes: TC1 and TC2.Tritrichomonas: A genus of flagellate EUKARYOTES possessing three long anterior flagella.Hemagglutinin Glycoproteins, Influenza Virus: Membrane glycoproteins from influenza viruses which are involved in hemagglutination, virus attachment, and envelope fusion. Fourteen distinct subtypes of HA glycoproteins and nine of NA glycoproteins have been identified from INFLUENZA A VIRUS; no subtypes have been identified for Influenza B or Influenza C viruses.Chagas Disease: Infection with the protozoan parasite TRYPANOSOMA CRUZI, a form of TRYPANOSOMIASIS endemic in Central and South America. It is named after the Brazilian physician Carlos Chagas, who discovered the parasite. Infection by the parasite (positive serologic result only) is distinguished from the clinical manifestations that develop years later, such as destruction of PARASYMPATHETIC GANGLIA; CHAGAS CARDIOMYOPATHY; and dysfunction of the ESOPHAGUS or COLON.Cattle: 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.Papillomavirus Infections: Neoplasms of the skin and mucous membranes caused by papillomaviruses. They are usually benign but some have a high risk for malignant progression.Poliomyelitis: An acute infectious disease of humans, particularly children, caused by any of three serotypes of human poliovirus (POLIOVIRUS). Usually the infection is limited to the gastrointestinal tract and nasopharynx, and is often asymptomatic. The central nervous system, primarily the spinal cord, may be affected, leading to rapidly progressive paralysis, coarse FASCICULATION and hyporeflexia. Motor neurons are primarily affected. Encephalitis may also occur. The virus replicates in the nervous system, and may cause significant neuronal loss, most notably in the spinal cord. A rare related condition, nonpoliovirus poliomyelitis, may result from infections with nonpoliovirus enteroviruses. (From Adams et al., Principles of Neurology, 6th ed, pp764-5)Disease Outbreaks: Sudden increase in the incidence of a disease. The concept includes EPIDEMICS and PANDEMICS.Drug Storage: The process of keeping pharmaceutical products in an appropriate location.Antigens, Viral: Substances elaborated by viruses that have antigenic activity.Rabies: Acute VIRAL CNS INFECTION affecting mammals, including humans. It is caused by RABIES VIRUS and usually spread by contamination with virus-laden saliva of bites inflicted by rabid animals. Important animal vectors include the dog, cat, bat, fox, raccoon, skunk, and wolf.Disease Models, Animal: Naturally occurring or experimentally induced animal diseases with pathological processes sufficiently similar to those of human diseases. They are used as study models for human diseases.Clinical Trials as Topic: Works about pre-planned studies of the safety, efficacy, or optimum dosage schedule (if appropriate) of one or more diagnostic, therapeutic, or prophylactic drugs, devices, or techniques selected according to predetermined criteria of eligibility and observed for predefined evidence of favorable and unfavorable effects. This concept includes clinical trials conducted both in the U.S. and in other countries.Entamoebiasis: Infection with amoebae of the genus ENTAMOEBA. Infection with E. histolytica causes DYSENTERY, AMEBIC and LIVER ABSCESS, AMEBIC.Epitopes, T-Lymphocyte: Antigenic determinants recognized and bound by the T-cell receptor. Epitopes recognized by the T-cell receptor are often located in the inner, unexposed side of the antigen, and become accessible to the T-cell receptors after proteolytic processing of the antigen.RNA, Ribosomal, 18S: Constituent of the 40S subunit of eukaryotic ribosomes. 18S rRNA is involved in the initiation of polypeptide synthesis in eukaryotes.Orthomyxoviridae Infections: Virus diseases caused by the ORTHOMYXOVIRIDAE.Dose-Response Relationship, Immunologic: A specific immune response elicited by a specific dose of an immunologically active substance or cell in an organism, tissue, or cell.Sarcocystis: A genus of protozoa found in reptiles, birds, and mammals, including humans. This heteroxenous parasite produces muscle cysts in intermediate hosts such as domestic herbivores (cattle, sheep, pigs) and rodents. Final hosts are predators such as dogs, cats, and man.Leishmania infantum: A parasitic hemoflagellate of the subgenus Leishmania leishmania that infects man and animals and causes visceral leishmaniasis (LEISHMANIASIS, VISCERAL). Human infections are confined almost entirely to children. This parasite is commonly seen in dogs, other Canidae, and porcupines with humans considered only an accidental host. Transmission is by Phlebotomus sandflies.Dendritic Cells: Specialized cells of the hematopoietic system that have branch-like extensions. They are found throughout the lymphatic system, and in non-lymphoid tissues such as SKIN and the epithelia of the intestinal, respiratory, and reproductive tracts. They trap and process ANTIGENS, and present them to T-CELLS, thereby stimulating CELL-MEDIATED IMMUNITY. They are different from the non-hematopoietic FOLLICULAR DENDRITIC CELLS, which have a similar morphology and immune system function, but with respect to humoral immunity (ANTIBODY PRODUCTION).Theileriasis: Infection of cattle, sheep, or goats with protozoa of the genus THEILERIA. This infection results in an acute or chronic febrile condition.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Immunity: Nonsusceptibility to the invasive or pathogenic effects of foreign microorganisms or to the toxic effect of antigenic substances.