Oligoadenylate synthetase 25OAS

An enzyme involved in the early stages of interferon induction. Upon activation by double-stranded RNA, 2'5'-OAS polymerizes ATP into pppA(2'p5'A)n(2'5'A). 2'5'A then activates a cellular endonucle-ase, 2'5'-OAS-dependent RNase L, which then degrades both cellular and viral RNAs at UU or AU nucleotides.

Samuel CE (1991) Virology 183,1

oligonucleotide mapping A technique for RNA characterization based upon the use especially of T1 ribonuclease to obtain RNA fragments separable by chromatog-raphy. Now replaced by more specific sequence analysis.

oligonucleotides Short polynucleotides containing about 2-10 nucleotides joined by phosphodiester bonds.

oligopeptide A short-chain linear peptide containing from 2 to 10 amino acids joined by peptide bonds.

Oliveros virus (OLI) A serologically distinct species of the Tacaribe complex of the family Arenaviridae, isolated in 1990 in Oliveros, a village in Argentina from a trapped rodent, Bolomys obscurus. Phylogenetic analysis confirmed that the virus is a distinct member of the Tacaribe complex of New World arenaviruses, most closely related to Latino virus. Role in human disease unknown.

Bowen MD et al (1996) Virology 217, 362 Mills JN et al (1996) Am J Trop Med Hyg 54, 399

OLV virus Synonym for H-3 virus.

Omo virus (OMOV) A serotype of Qalyub virus in the genus Nairovirus. Isolated from the rodent Mastomys erythroleucus in Ethiopia.

Rodhain F et al (1985) Ann Inst Pasteur Virol 136E, 243

Omsk hemorrhagic fever virus (OHFV) A tick-borne species in the genus Flavivirus, member of the Mammalian tick-borne encephalitis serogroup. Vectors are ticks,

Dermacentor pictus and D. marginatus, in which transovarian transmission is reported. Man may also be infected by direct contact with infected muskrats. Causes a biphasic illness in humans with fever, enlargement of lymph nodes, gastrointestinal symptoms, and hemorrhages from nose, stomach and uterus, but little or no CNS involvement. Mortality 1-2%. Disease occurs in the former central USSR. Causes fever in rhesus monkeys injected i.p. On first isolation does not infect adult mice.

Netzky GI (1967) Jap J Med Sci Biol (suppl) 20, 141

Omsk virus See Omsk hemorrhagic fever virus.

Onchorhynchus masou herpesvirus Synonym for salmonid herpesvirus 2.

Oncorhynchus masou virus Synonym for salmonid herpesvirus 2.

oncogene A gene which encodes a protein whose expression leads to cell transformation. Originally discovered during studies of Rous sarcoma virus in the 1970s when the src gene was isolated and shown to have a cell homolog. Since then, more than 100 viral oncogenes and proto-oncogenes (cellular genes that may become disregulated to cause cell transformation) have been described. In general, viral oncogenes are transduced genetic sequences found in the genome of acutely transforming viruses which have cellular homologs (proto-oncogenes) from which they were derived. Evolutionary changes in the virus genome have led in some cases to considerable differences between the products of the viral oncogenes and their cellular homologs, but their relationship can be clearly seen at the genetic level. In describing oncogenes, the gene is italicized (e.g. jun) and the protein product capitalized (e.g. JUN protein). The viral oncogene is written v-jun and the cellular gene counterpart c-jun.

Cooper GM (1995) Oncogenes, Second edition.

Boston: Jones and Bartlett

Hesketh R (1994) The Oncogene Handbook.

London: Academic Press

Rasheed S (1995) In The Retroviridae, vol. 4, edited by JA Levy. New York: Plenum Press, p. 293


oncogenic Tumor-inducing.

oncogenic RNA virus Old name for group of RNA tumor viruses, now included in the family Retroviridae.

oncoproteins Proteins produced from onco-genes: tumor-inducing proteins.

oncornaviruses Old name for the RNA tumor viruses.

Oncovirinae An old name for a subfamily of oncogenic retroviruses. No longer in use.

one-hit kinetics In systems where one particle can initiate infection, the number of plaques appearing is directly proportional to the first power of the concentration of the inoculum. If this concentration is doubled, the number of plaques will be doubled.

one-step growth curve An experiment in which all the cells in a particular culture are infected simultaneously, so that events in individual cells can be inferred from events in the whole population.

Ontario encephalomyelitis virus Synonym for Porcine hemagglutinating encephalo-myelitis virus.

O'Nyong-Nyong virus (ONNV) A species in the genus Alphavirus. The complete nucleotide sequence shows a close genetic relationship to Semliki Forest virus. In humans it causes a febrile illness with lymphadenitis, severe joint pains and rash. Epidemic spread occurs with anopheline mosquitoes as vector. Occurs in Uganda, Kenya, Tanzania, Malawi and Senegal. Pathogenic for suckling mice given i.c.; older mice are resistant. Infant mice which survive the infection are stunted and show patchy alopecia. Virus is propagated in chick embryo fibroblast cell cultures.

Chanas AC et al (1979) Arch Virol 59, 231 Levinson R et al (1990) Virology 175, 110

opal codon UGA One of the three termination codons. See nonsense codons.

opal mutant Virus with mutation resulting in a chain termination codon UGA.

open circular DNA Circular DNA in which one or both strands are not covalently closed.

open reading frame (ORF) A set of codons for amino acids uninterrupted by stop codons. Usually encodes one or more proteins.

opossum adenovirus A possible species in the genus Mastadenovirus. Isolated from an opossum, Didelphis marsupialis, primary kidney cell culture showing spontaneous CPE. Did not replicate in rabbit, hamster, human or rhesus monkey kidney cell cultures, or in HeLa or HEP-2 cells.

Morales-Ayala F et al (1964) Bacterial Proc, p. 117

opossum viruses A and B Not viruses. Chlamydiae.

opportunistic infections Infections which become established due to immuno-suppression of the patient, e.g. as a result of chemotherapy or AIDS.

Glaser CA et al (1994) Clin Infect Dis 18, 14

opportunistic pathogens A variety of infectious pathogens, including many viruses, cause opportunistic infections in immunosuppressed persons. Amongst the viruses, those that are normally latent, such as cytomegalovirus, herpes simplex virus, JC polyoma virus and varicella-zoster virus, cause most common problems, especially in AIDS patients.

OPV Oral poliovirus vaccine, originally developed by Albert Sabin.

Oran virus A strain of Andes virus in the genus Hantavirus isolated from Oligoryzomys longicaudatus in Argentina. Caused fatal hantavirus pulmonary syndrome in humans.

Calderon G et al (1999) Emerg Inf Dis 5, 792

orangutan herpesvirus Synonym for

Pongine herpesvirus 2.

Orbivirus (Latin: orbis = a ring) A genus of the family Reoviridae containing 19 recognized species and 13 tentative species. All multiply in insects and several also in vertebrates. Virion 80nm in diameter, with a double protein shell: the outer one without readily definable capsomeres, the inner with 32 seemingly ring-shaped cap-someres arranged with icosahedral symmetry and visible in the presence of the outer shell. Only slightly sensitive to lipid solvents, inactivated at pH 3. The double-stranded RNA genome consists of 10 segments between 822 and 3954 bp, total 19.2kb. There are seven virion and three non-structural proteins. The single-shelled nucleocapsid having lost the outer shell has transcriptase activity with an optimum temperature of 28°C. Replicate with CPE in BHK21 cells. Kill newborn mice but not adults on i.c. injection. Do not kill mice of any age on i.p. injection. The type species is Bluetongue virus. They have no common antigen but the 153 known viruses are divided into 19 species on the basis of antigenic cross-reactions. The species and their principal vectors are:

  • 1) African horse sickness virus (9 serotypes) (Culicoides)
  • 2) Bluetongue virus (24 serotypes) (Culicoides)
  • 3) Changuinola virus (12 serotypes) (phlebotomines or culicine mosquitoes)
  • 4) Chenuda virus (7 serotypes) (ticks)
  • 5) Chobar Gorge virus (2 serotypes) (ticks)
  • 6) Corriparta virus (5 serotypes) (culicine mosquitoes)
  • 7) Epizootic hemorrhagic disease virus (8 serotypes) (Culicoides)
  • 8) Equine encephalosis virus (7 serotypes) (Culicoides)
  • 9) Eubenangee virus (4 serotypes) (Culicoides, anopheline and culicine mosquitoes)
  • 10) Great Island virus (36 serotypes) (ticks)
  • 11) Ieri virus (3 serotypes) (mosquitoes)
  • 12) Lebombo virus (1 serotype) (culicine mosquitoes)
  • 13) Orungo virus (4 serotypes) (culicine mosquitoes)
  • 14) Palyam virus (11 serotypes) (Culicoides, culicine mosquitoes)
  • 15) Umatilla virus (4 serotypes) (culicine mosquitoes)
  • 16) Wad Medani virus (2 serotypes) (ticks)
  • 17) Wallal virus (3 serotypes) (Culicoides)
  • 18) Warrego virus (3 serotypes)
  • Culicoides, anopheline and culicine mosquitoes) (19) Wongorr virus (8 serotypes) (Culicoides, mosquitoes)

In addition there are 13 tentative species in the genus awaiting further characterization.

Mertens PPC (1999) In Encyclopedia of Virology, Second edition, edited by A Granoff and RG Webster. London: Academic Press, p. 1043 Roy P and Gorman B (editors) (1990) Curr Top Microbiol Immun 162, 200 pp orcinol reaction A colorimetric assay for the presence of carbohydrates, especially pentose sugars. Used to determine RNA concentrations, e.g. the amount of RNA in a virus preparation. See dipheny-lamine reaction.

Lin RIS and Schjeide OA (1969) Anal Biochem 27, 473

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