Reticuloendotheliosis virus strain TA

(REV) A species in the genus Gammaretrovirus. Avian viruses for which related endogenous sequences have been found only in mammals, not birds. There are two recognized related species: Chick syncytial virus and Trager duck spleen necrosis virus. All three are closely related, but cross-react hardly at all with chicken leukosis sarcoma viruses. They do not have nucleotide sequences in common with them. The viruses are all non-defective except REV strain T, which has a smaller genome length (5.7kb) than the other viruses (9.0kb), and requires a helper virus for its replication. However, strain T carries the oncogene v-rel which specifies a DNA-binding transcription factor in infected cells and is highly oncogenic, inducing immature B-cell lymphomas. All three viruses are probably widely distributed among turkeys and wild water fowl, especially ducks and geese. The only spontaneous disease produced appears to be turkey leukosis. Chickens, quail, ducklings, goslings, turkeys, pheasants and guinea keets are susceptible to virus injected by any route. A large dose causes death in 3 days. With smaller doses or in older animals death is not so rapid and some animals survive. Such birds are often thin, anemic, retarded and have poor feather development. Histological changes produced by the virus are visceral or neural, proliferative lesions and necrotizing lesions. The proportion of each varies with the strain of virus. In the proliferative lesions the cells are his-tiocytoid and probably malignant. The virus replicates in chick embryo fibrob-last cultures, producing a transitory CPE followed by transformation. Synonym: avian reticuloendotheliosis virus.

Payne LN (1992) In The Retroviridae, vol. 1, edited by JA Levy. New York: Plenum Press, p. 365

retinoic acid A compound which inhibits the replication of Human papillomavirus.

Bartsch D (1992) EMBO J 11,2283

retroid elements Reverse transcription is not uniquely associated with retro-viruses and hepadnaviruses. A variety of transposable elements from yeast, Drosophila, Dictyostelium and maize have structural similarities to integrated forms of the retrovirus genome and these are known as retroid elements or retrotrans-posons.

Retrovir The first effective inhibitor of retroviruses, better known as AZT (azi-dothymidine). See AZT.

Retroviridae A family of large single-stranded RNA viruses which have a virion RNA-dependent DNA polymerase. Virions are spherical, about 80-100nm in diameter. Lipoprotein envelope encloses an icosahedral core shell within which there is a helical nucleocapsid. The envelope has glycoprotein surface projections 8 nm long. The genome is a dimer of two hydrogen-bonded positive single-stranded RNAs, each monomer 7-11kb in length. Viral RNA is transcribed by the virion transcriptase into a covalently linked circle of double-stranded DNA (provirus) which becomes integrated into the cellular DNA. Viral RNA serving as mRNA and virion RNA for progeny particles is transcribed from the integrated DNA provirus. Replication is sensitive to inhibitors of DNA synthesis during the first 6 h after infection, and to actinomycin D at any time. Maturation occurs by budding from the cytoplasmic membranes. Provirus DNA extracted from infected cells is infective. There are seven genera: Alpharetrovirus, Betaretrovirus, Gammaretrovirus, Deltaretrovirus, Epsilonretrovirus, Lentivirus and Spumavirus. Retroviruses are associated with a variety of animal diseases as well as human diseases including AIDS, autoimmune disease and lower motor neurone disease, but may also be non-pathogenic. Retroviruses may be present in all vertebrate genomes. Synonym: ribodeoxy virus.

Coffin JM (1992) In The Retroviridae, vol. 1, edited by JA Levy. New York: Plenum Press, p. 19

Herniou E et al (1998) J Virol 72, 5955

retroviruses Species in the family

Retroviridae.

reverse genetics The recovery of negativestrand virus RNA as DNA to facilitate genome studies.

Roberts A and Rose JK (1998) Virology 247,1

Nagai Y and Kato A (1999) Microbiol Immunol 43, 613

reverse passive hemagglutination A sensitive serological test in which red blood

Rhabdoviridae cells are coated with virus-specific antibody and used to test for the presence of antigen. If virus antigen is present, the red blood cells are agglutinated. See passive hemagglutination.

reverse transcriptase Synonym for RNA-dependent DNA polymerase.

reverse transcription Transcription of RNA into DNA.

reverse transcription polymerase chain reaction (RT-PCR) A frequently employed method to prepare DNA copies of an RNA virus, which can then be used for sequence analysis or other purposes.

reversion A change in nucleotide sequence that reverses the mutation at the original site and restores the original phenotype.

rev protein An RNA-binding nuclear protein induced in cells infected by Human immunodeficiency viruses (HIV-1 and HIV-2) that regulates virus gene expression and is essential for virus replication. Binds to a region of HIV RNA known as the rev response element (RRE), and controls splicing so that single-spliced and unspliced RNA species are produced in the later stages of virus replication.

rev response element (RRE) A specific sequence in the retroviral RNA genome that interacts with a sequence in the host cell genome.

rex protein An RNA-binding protein, induced in cells infected with human T-cell leukemia viruses types I and II, which influences splicing and transport of viral mRNAs.

Reye's syndrome A neurological and metabolic disease of children and adolescents first described in Australia in 1963. Characterized by encephalopathy and fatty degeneration of the liver. The syndrome has been observed to follow infections with Influenza virus A, Influenza virus B, parainfluenza virus, human adenovirus, Human herpesvirus 3 and Human respiratory syncytial virus. An acute encephalopathy with fatty degeneration of the viscera with a fatality rate of about 20%. Cause is uncertain but some 40% of cases have an association with various drugs or chemicals, especially aspirin and related salicylates. There are often symptoms and signs of upper respiratory tract infection, and an association with various viruses has been suggested, but the evidence is not very strong and environmental or constitutional factors may be important. The addition of warning notices on aspirin bottles in the USA has helped to reduce the number of cases. Synonym: Reye-Johnson syndrome.

Belay ED et al (1999) New Engl J Med 340, 1377 Reye RDK et al (1963) Lancet 2, 749

RFLP Restriction fragment length polymorphism.

RFL-6 cells (CCL 192) A fibroblast-like cell line derived from the lung of a normal, germ-free, Sprague-Dawley rat fetus.

RF virus A strain of BK virus. Isolated in human embryo kidney cell culture from the urine of a renal transplant patient. Antigenically indistinguishable from BK virus and their DNAs have an 88% homology.

Miao R and Dougherty RM (1977) J Gen Virol 35, 67

Rhabdoviridae A large family of RNA negative-strand viruses comprising at least five genera and 75 species which infect vertebrates, invertebrates and plants. Many species are pathogenic and transmitted by arthropods. Rhabdoviruses are rod-shaped, varying in length (100-430nm) but more uniform in diameter (45-100nm). The animal species are bullet-shaped, being flattened at one end and pointed at the other, whereas the plant species are rounded at both ends. They all have a membranous envelope with spikes 5-10nm long. The envelope is disrupted by lipid solvents. Wound inside the envelope is a helical nucleocapsid with a diameter of 50nm. There is one molecule of negative-sense single-stranded RNA 11-15kb in length which is not infective and is transcribed by an RNA-dependent RNA polymerase in the nucleocapsid into at least five messenger RNA species. Most of the viruses which have been studied contain five proteins designated: L (large),

Rhabdoviridae

G (glycoprotein), N (nucleoprotein), NS or Ml (non-structural), and M and M2 (matrix). The NS protein was originally thought to be non-structural but is a component of the virion RNA polymerase required for transcription. Defective truncated virions (T virions) with a portion of the RNA genome deleted arise frequently during replication. Virus attaches to cells by the G protein and enters by endocytosis via coated pits. After uncoating, the virion RNA-dependent RNA polymerase transcribes capped and polyadenylated RNA species which are translated into virus proteins. RNA replication occurs entirely in the cytoplasm and requires no nuclear functions. Nucleocapsids are assembled and enveloped, then bud from the plasma membranes. Three genera, Lyssavirus, Vesiculovirus and Ephemerovirus, contain the viruses which replicate in vertebrate species.

Brown F et al (1979) Intervirology 12, 1 Wagner RR (editor) (1987) The Rhabdoviruses. New York: Plenum Press rhabdovirus 903/87 A novel fish pathogenic rhabdovirus.

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