Lentivirus: A genus of the family RETROVIRIDAE consisting of non-oncogenic retroviruses that produce multi-organ diseases characterized by long incubation periods and persistent infection. Lentiviruses are unique in that they contain open reading frames (ORFs) between the pol and env genes and in the 3' env region. Five serogroups are recognized, reflecting the mammalian hosts with which they are associated. HIV-1 is the type species.Lentivirus Infections: Virus diseases caused by the Lentivirus genus. They are multi-organ diseases characterized by long incubation periods and persistent infection.Lentiviruses, Ovine-Caprine: A subgenus of LENTIVIRUS comprising viruses that produce multi-organ disease with long incubation periods in sheep and goats.Visna-maedi virus: A species of LENTIVIRUS, subgenus ovine-caprine lentiviruses (LENTIVIRUSES, OVINE-CAPRINE), that can cause chronic pneumonia (maedi), mastitis, arthritis, and encephalomyelitis (visna) in sheep. Maedi is a progressive pneumonia of sheep which is similar to but not the same as jaagsiekte (PULMONARY ADENOMATOSIS, OVINE). Visna is a demyelinating leukoencephalomyelitis of sheep which is similar to but not the same as SCRAPIE.Infectious Anemia Virus, Equine: 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.Visna: Demyelinating leukoencephalomyelitis of sheep caused by the VISNA-MAEDI VIRUS. It is similar to but not the same as SCRAPIE.Immunodeficiency Virus, Feline: A species of LENTIVIRUS, subgenus feline lentiviruses (LENTIVIRUSES, FELINE) isolated from cats with a chronic wasting syndrome, presumed to be immune deficiency. There are 3 strains: Petaluma (FIP-P), Oma (FIP-O) and Puma lentivirus (PLV). There is no antigenic relationship between FIV and HIV, nor does FIV grow in human T-cells.Pneumonia, Progressive Interstitial, of Sheep: Chronic respiratory disease caused by the VISNA-MAEDI VIRUS. It was formerly believed to be identical with jaagsiekte (PULMONARY ADENOMATOSIS, OVINE) but is now recognized as a separate entity.Arthritis-Encephalitis Virus, Caprine: A species of LENTIVIRUS, subgenus ovine-caprine lentiviruses (LENTIVIRUSES, OVINE-CAPRINE), closely related to VISNA-MAEDI VIRUS and causing acute encephalomyelitis; chronic arthritis; PNEUMONIA; MASTITIS; and GLOMERULONEPHRITIS in goats. It is transmitted mainly in the colostrum and milk.Lentiviruses, Primate: A subgenus of LENTIVIRUS comprising viruses that produce immunodeficiencies in primates, including humans.Lentiviruses, Bovine: A subgenus of LENTIVIRUS comprising viruses that produce multi-organ disease with long incubation periods in cattle.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.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.Puma: A genus in the family FELIDAE comprising one species, Puma concolor. It is a large, long-tailed, feline of uniform color. The names puma, cougar, and mountain lion are used interchangeably for this species. There are more than 20 subspecies.Equine Infectious Anemia: 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.Feline Acquired Immunodeficiency Syndrome: Acquired defect of cellular immunity that occurs in cats infected with feline immunodeficiency virus (FIV) and in some cats infected with feline leukemia virus (FeLV).Goats: Any of numerous agile, hollow-horned RUMINANTS of the genus Capra, in the family Bovidae, closely related to the SHEEP.Cercopithecus: A genus of Old World monkeys found in Africa although some species have been introduced into the West Indies. This genus is composed of at least twenty species: C. AETHIOPS, C. ascanius, C. campbelli, C. cephus, C. denti, C. diana, C. dryas, C. erythrogaster, C. erythrotis, C. hamlyni, C. lhoesti, C. mitis, C. mona, C. neglectus, C. nictitans, C. petaurista, C. pogonias, C. preussi, C. salongo, and C. wolfi.Lions: Large, chiefly nocturnal mammals of the cat family FELIDAE, species Panthera leo. They are found in Africa and southern Asia.Simian immunodeficiency virus: Species of the genus LENTIVIRUS, subgenus primate immunodeficiency viruses (IMMUNODEFICIENCY VIRUSES, PRIMATE), that induces acquired immunodeficiency syndrome in monkeys and apes (SAIDS). The genetic organization of SIV is virtually identical to HIV.Lentiviruses, Feline: A subgenus of LENTIVIRUS comprising viruses that produce multi-organ disease with long incubation periods in cats.Sheep Diseases: Diseases of domestic and mountain sheep of the genus Ovis.Goat Diseases: Diseases of the domestic or wild goat of the genus Capra.Lemur: A genus of the family Lemuridae consisting of five species: L. catta (ring-tailed lemur), L. fulvus, L. macaco (acoumba or black lemur), L. mongoz (mongoose lemur), and L. variegatus (white lemur). Most members of this genus occur in forested areas on Madagascar and the Comoro Islands.Immunodeficiency Virus, Bovine: The type species of LENTIVIRUS, subgenus bovine lentiviruses (LENTIVIRUSES, BOVINE), found in cattle and causing lymphadenopathy, LYMPHOCYTOSIS, central nervous system lesions, progressive weakness, and emaciation. It has immunological cross-reactivity with other lentiviruses including HIV.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.Gene Transfer Techniques: The introduction of functional (usually cloned) GENES into cells. A variety of techniques and naturally occurring processes are used for the gene transfer such as cell hybridization, LIPOSOMES or microcell-mediated gene transfer, ELECTROPORATION, chromosome-mediated gene transfer, TRANSFECTION, and GENETIC TRANSDUCTION. Gene transfer may result in genetically transformed cells and individual organisms.Cats: The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801)Sheep: Any of the ruminant mammals with curved horns in the genus Ovis, family Bovidae. They possess lachrymal grooves and interdigital glands, which are absent in GOATS.Genetic Therapy: Techniques and strategies which include the use of coding sequences and other conventional or radical means to transform or modify cells for the purpose of treating or reversing disease conditions.Horses: 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.Genes, tat: DNA sequences that form the coding region for the protein responsible for trans-activation of transcription (tat) in human immunodeficiency virus (HIV).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.Cell Line: Established cell cultures that have the potential to propagate indefinitely.Green Fluorescent Proteins: Protein analogs and derivatives of the Aequorea victoria green fluorescent protein that emit light (FLUORESCENCE) when excited with ULTRAVIOLET RAYS. They are used in REPORTER GENES in doing GENETIC TECHNIQUES. Numerous mutants have been made to emit other colors or be sensitive to pH.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.Viral Envelope Proteins: 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.Gene Products, pol: Retroviral proteins coded by the pol gene. They are usually synthesized as a protein precursor (POLYPROTEINS) and later cleaved into final products that include reverse transcriptase, endonuclease/integrase, and viral protease. Sometimes they are synthesized as a gag-pol fusion protein (FUSION PROTEINS, GAG-POL). pol is short for polymerase, the enzyme class of reverse transcriptase.Genes, pol: DNA sequences that form the coding region for retroviral enzymes including reverse transcriptase, protease, and endonuclease/integrase. "pol" is short for polymerase, the enzyme class of reverse transcriptase.Genes, rev: DNA sequences that form the coding region for a protein that regulates the expression of the viral structural and regulatory proteins in human immunodeficiency virus (HIV). rev is short for regulator of virion.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.Simian Acquired Immunodeficiency Syndrome: Acquired defect of cellular immunity that occurs naturally in macaques infected with SRV serotypes, experimentally in monkeys inoculated with SRV or MASON-PFIZER MONKEY VIRUS; (MPMV), or in monkeys infected with SIMIAN IMMUNODEFICIENCY VIRUS.Gene Products, env: Retroviral proteins, often glycosylated, coded by the envelope (env) gene. They are usually synthesized as protein precursors (POLYPROTEINS) and later cleaved into the final viral envelope glycoproteins by a viral protease.Genes, env: DNA sequences that form the coding region for the viral envelope (env) proteins in retroviruses. The env genes contain a cis-acting RNA target sequence for the rev protein (= GENE PRODUCTS, REV), termed the rev-responsive element (RRE).Retroviridae: Family of RNA viruses that infects birds and mammals and encodes the enzyme reverse transcriptase. The family contains seven genera: DELTARETROVIRUS; LENTIVIRUS; RETROVIRUSES TYPE B, MAMMALIAN; ALPHARETROVIRUS; GAMMARETROVIRUS; RETROVIRUSES TYPE D; and SPUMAVIRUS. A key feature of retrovirus biology is the synthesis of a DNA copy of the genome which is integrated into cellular DNA. After integration it is sometimes not expressed but maintained in a latent state (PROVIRUSES).Transgenes: Genes that are introduced into an organism using GENE TRANSFER TECHNIQUES.Virus Integration: Insertion of viral DNA into host-cell DNA. This includes integration of phage DNA into bacterial DNA; (LYSOGENY); to form a PROPHAGE or integration of retroviral DNA into cellular DNA to form a PROVIRUS.Betaretrovirus: A genus of the family RETROVIRIDAE consisting of viruses with either type B or type D morphology. This includes a few exogenous, vertically transmitted and endogenous viruses of mice (type B) and some primate and sheep viruses (type D). MAMMARY TUMOR VIRUS, MOUSE is the type species.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Proviruses: Duplex DNA sequences in eukaryotic chromosomes, corresponding to the genome of a virus, that are transmitted from one cell generation to the next without causing lysis of the host. Proviruses are often associated with neoplastic cell transformation and are key features of retrovirus biology.Hexadimethrine Bromide: A synthetic polymer which agglutinates red blood cells. It is used as a heparin antagonist.Antibodies, Viral: Immunoglobulins produced in response to VIRAL ANTIGENS.Terminal Repeat Sequences: Nucleotide sequences repeated on both the 5' and 3' ends of a sequence under consideration. For example, the hallmarks of a transposon are that it is flanked by inverted repeats on each end and the inverted repeats are flanked by direct repeats. The Delta element of Ty retrotransposons and LTRs (long terminal repeats) are examples of this concept.HIV-2: An HIV species related to HIV-1 but carrying different antigenic components and with differing nucleic acid composition. It shares serologic reactivity and sequence homology with the simian Lentivirus SIMIAN IMMUNODEFICIENCY VIRUS and infects only T4-lymphocytes expressing the CD4 phenotypic marker.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.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.Animals, Wild: Animals considered to be wild or feral or not adapted for domestic use. It does not include wild animals in zoos for which ANIMALS, ZOO is available.DNA, Viral: Deoxyribonucleic acid that makes up the genetic material of viruses.Lagomorpha: An order of small mammals comprising two families, Ochotonidae (pikas) and Leporidae (RABBITS and HARES). Head and body length ranges from about 125 mm to 750 mm. Hares and rabbits have a short tail, and the pikas lack a tail. Rabbits are born furless and with both eyes and ears closed. HARES are born fully haired with eyes and ears open. All are vegetarians. (From Nowak, Walker's Mammals of the World, 5th ed, p539-41)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.Genes, vif: DNA sequences that form the coding region for the vif (virion infectivity factor) protein that is important for the generation of infectious virions in human immunodeficiency virus (HIV). The former name of this gene was sor (short open reading frame).Polyglactin 910: A polyester used for absorbable sutures & surgical mesh, especially in ophthalmic surgery. 2-Hydroxy-propanoic acid polymer with polymerized hydroxyacetic acid, which forms 3,6-dimethyl-1,4-dioxane-dione polymer with 1,4-dioxane-2,5-dione copolymer of molecular weight about 80,000 daltons.Retroviridae Infections: Virus diseases caused by the RETROVIRIDAE.Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Luminescent Proteins: Proteins which are involved in the phenomenon of light emission in living systems. Included are the "enzymatic" and "non-enzymatic" types of system with or without the presence of oxygen or co-factors.Genes, vpu: DNA sequences that form the coding region for the HIV-1 regulatory protein vpu (viral protein U) that greatly increases the export of virus particles from infected cells. The vpu genes are not present in HIV-2 or SIMIAN IMMUNODEFICIENCY VIRUS.Pulmonary Adenomatosis, Ovine: A contagious, neoplastic, pulmonary disease of sheep characterized by hyperplasia and hypertrophy of pneumocytes and epithelial cells of the lung. It is caused by JAAGSIEKTE SHEEP RETROVIRUS.Gene Knockdown Techniques: The artificial induction of GENE SILENCING by the use of RNA INTERFERENCE to reduce the expression of a specific gene. It includes the use of DOUBLE-STRANDED RNA, such as SMALL INTERFERING RNA and RNA containing HAIRPIN LOOP SEQUENCE, and ANTI-SENSE OLIGONUCLEOTIDES.RNA Interference: A gene silencing phenomenon whereby specific dsRNAs (RNA, DOUBLE-STRANDED) trigger the degradation of homologous mRNA (RNA, MESSENGER). The specific dsRNAs are processed into SMALL INTERFERING RNA (siRNA) which serves as a guide for cleavage of the homologous mRNA in the RNA-INDUCED SILENCING COMPLEX. DNA METHYLATION may also be triggered during this process.Tropism: The directional growth of an organism in response to an external stimulus such as light, touch, or gravity. Growth towards the stimulus is a positive tropism; growth away from the stimulus is a negative tropism. (From Concise Dictionary of Biology, 1990)PrimatesHEK293 Cells: A cell line generated from human embryonic kidney cells that were transformed with human adenovirus type 5.HIV: Human immunodeficiency virus. A non-taxonomic and historical term referring to any of two species, specifically HIV-1 and/or HIV-2. Prior to 1986, this was called human T-lymphotropic virus type III/lymphadenopathy-associated virus (HTLV-III/LAV). From 1986-1990, it was an official species called HIV. Since 1991, HIV was no longer considered an official species name; the two species were designated HIV-1 and HIV-2.Viral Regulatory and Accessory Proteins: A broad category of viral proteins that play indirect roles in the biological processes and activities of viruses. Included here are proteins that either regulate the expression of viral genes or are involved in modifying host cell functions. Many of the proteins in this category serve multiple functions.RNA, Small Interfering: Small double-stranded, non-protein coding RNAs (21-31 nucleotides) involved in GENE SILENCING functions, especially RNA INTERFERENCE (RNAi). Endogenously, siRNAs are generated from dsRNAs (RNA, DOUBLE-STRANDED) by the same ribonuclease, Dicer, that generates miRNAs (MICRORNAS). The perfect match of the siRNAs' antisense strand to their target RNAs mediates RNAi by siRNA-guided RNA cleavage. siRNAs fall into different classes including trans-acting siRNA (tasiRNA), repeat-associated RNA (rasiRNA), small-scan RNA (scnRNA), and Piwi protein-interacting RNA (piRNA) and have different specific gene silencing functions.Genome, Viral: The complete genetic complement contained in a DNA or RNA molecule in a virus.Sheep, Domestic: A species of sheep, Ovis aries, descended from Near Eastern wild forms, especially mouflon.Gene Products, vif: Retrovirally encoded accessary proteins that play an essential role VIRUS REPLICATION. They are found in the cytoplasm of host cells and associate with a variety of host cell proteins. Vif stands for "virion infectivity factor".Monkey Diseases: Diseases of Old World and New World monkeys. This term includes diseases of baboons but not of chimpanzees or gorillas (= APE DISEASES).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.Gene Products, rev: Trans-acting nuclear proteins whose functional expression are required for retroviral replication. Specifically, the rev gene products are required for processing and translation of the gag and env mRNAs, and thus rev regulates the expression of the viral structural proteins. rev can also regulate viral regulatory proteins. A cis-acting antirepression sequence (CAR) in env, also known as the rev-responsive element (RRE), is responsive to the rev gene product. rev is short for regulator of virion.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.Gene Products, tat: Trans-acting transcription factors produced by retroviruses such as HIV. They are nuclear proteins whose expression is required for viral replication. The tat protein stimulates LONG TERMINAL REPEAT-driven RNA synthesis for both viral regulatory and viral structural proteins. tat stands for trans-activation of transcription.RNA, Viral: Ribonucleic acid that makes up the genetic material of viruses.Gene Expression: The phenotypic manifestation of a gene or genes by the processes of GENETIC TRANSCRIPTION and GENETIC TRANSLATION.Gene Expression Regulation, Viral: Any of the processes by which cytoplasmic factors influence the differential control of gene action in viruses.Macaca: A genus of the subfamily CERCOPITHECINAE, family CERCOPITHECIDAE, consisting of 16 species inhabiting forests of Africa, Asia, and the islands of Borneo, Philippines, and Celebes.Retroviridae Proteins: Proteins from the family Retroviridae. The most frequently encountered member of this family is the Rous sarcoma virus protein.Doxycycline: A synthetic tetracycline derivative with similar antimicrobial activity.Transfection: 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.Leukocytes, Mononuclear: Mature LYMPHOCYTES and MONOCYTES transported by the blood to the body's extravascular space. They are morphologically distinguishable from mature granulocytic leukocytes by their large, non-lobed nuclei and lack of coarse, heavily stained cytoplasmic granules.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.Viral Vaccines: Suspensions of attenuated or killed viruses administered for the prevention or treatment of infectious viral disease.Endogenous Retroviruses: Retroviruses that have integrated into the germline (PROVIRUSES) that have lost infectious capability but retained the capability to transpose.Macaca nemestrina: A species of the genus MACACA which inhabits Malaya, Sumatra, and Borneo. It is one of the most arboreal species of Macaca. The tail is short and untwisted.Vesicular stomatitis Indiana virus: The type species of VESICULOVIRUS causing a disease symptomatically similar to FOOT-AND-MOUTH DISEASE in cattle, horses, and pigs. It may be transmitted to other species including humans, where it causes influenza-like symptoms.Polymerase Chain Reaction: 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.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).Gene Products, vpr: Trans-acting proteins which accelerate retroviral virus replication. The vpr proteins act in trans to increase the levels of specified proteins. vpr is short for viral protein R, where R is undefined.Genes, Reporter: Genes whose expression is easily detectable and therefore used to study promoter activity at many positions in a target genome. In recombinant DNA technology, these genes may be attached to a promoter region of interest.HIV Long Terminal Repeat: Regulatory sequences important for viral replication that are located on each end of the HIV genome. The LTR includes the HIV ENHANCER, promoter, and other sequences. Specific regions in the LTR include the negative regulatory element (NRE), NF-kappa B binding sites , Sp1 binding sites, TATA BOX, and trans-acting responsive element (TAR). The binding of both cellular and viral proteins to these regions regulates HIV transcription.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.Flow Cytometry: Technique using an instrument system for making, processing, and displaying one or more measurements on individual cells obtained from a cell suspension. Cells are usually stained with one or more fluorescent dyes specific to cell components of interest, e.g., DNA, and fluorescence of each cell is measured as it rapidly transverses the excitation beam (laser or mercury arc lamp). Fluorescence provides a quantitative measure of various biochemical and biophysical properties of the cell, as well as a basis for cell sorting. Other measurable optical parameters include light absorption and light scattering, the latter being applicable to the measurement of cell size, shape, density, granularity, and stain uptake.Virus Assembly: The assembly of VIRAL STRUCTURAL PROTEINS and nucleic acid (VIRAL DNA or VIRAL RNA) to form a VIRUS PARTICLE.Cell Line, Tumor: A cell line derived from cultured tumor cells.Promoter Regions, Genetic: DNA sequences which are recognized (directly or indirectly) and bound by a DNA-dependent RNA polymerase during the initiation of transcription. Highly conserved sequences within the promoter include the Pribnow box in bacteria and the TATA BOX in eukaryotes.Sequence Analysis, DNA: A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.Cell Proliferation: All of the processes involved in increasing CELL NUMBER including CELL DIVISION.Leukemia Virus, Murine: Species of GAMMARETROVIRUS, containing many well-defined strains, producing leukemia in mice. Disease is commonly induced by injecting filtrates of propagable tumors into newborn mice.Genes, vpr: DNA sequences that form the coding region for a trans-activator protein that specifies rapid growth in human immunodeficiency virus (HIV). vpr is short for viral protein R, where R is undefined.Ross River virus: A species of ALPHAVIRUS associated with epidemic EXANTHEMA and polyarthritis in Australia.Choroid Plexus: A villous structure of tangled masses of BLOOD VESSELS contained within the third, lateral, and fourth ventricles of the BRAIN. It regulates part of the production and composition of CEREBROSPINAL FLUID.Macrophages: The relatively long-lived phagocytic cell of mammalian tissues that are derived from blood MONOCYTES. Main types are PERITONEAL MACROPHAGES; ALVEOLAR MACROPHAGES; HISTIOCYTES; KUPFFER CELLS of the liver; and OSTEOCLASTS. They may further differentiate within chronic inflammatory lesions to EPITHELIOID CELLS or may fuse to form FOREIGN BODY GIANT CELLS or LANGHANS GIANT CELLS. (from The Dictionary of Cell Biology, Lackie and Dow, 3rd ed.)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.Membrane Glycoproteins: Glycoproteins found on the membrane or surface of cells.Spumavirus: Genus of non-oncogenic retroviruses which establish persistent infections in many animal species but are considered non-pathogenic. Its species have been isolated from primates (including humans), cattle, cats, hamsters, horses, and sea lions. Spumaviruses have a foamy or lace-like appearance and are often accompanied by syncytium formation. SIMIAN FOAMY VIRUS is the type species.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.Viral Load: The quantity of measurable virus in a body fluid. Change in viral load, measured in plasma, is sometimes used as a SURROGATE MARKER in disease progression.vpr Gene Products, Human Immunodeficiency Virus: Proteins encoded by the VPR GENES of the HUMAN IMMUNODEFICIENCY VIRUS.Capsid: The outer protein protective shell of a virus, which protects the viral nucleic acid.Reverse Transcriptase Polymerase Chain Reaction: A variation of the PCR technique in which cDNA is made from RNA via reverse transcription. The resultant cDNA is then amplified using standard PCR protocols.