Vilyuisk human encephalomyelitis virus

(VHEV) A strain of Theilovirus in the genus Cardiovirus. Encephalitis occurs in northern Siberia and subsequently one-third of patients develop chronic progressive disease similar to amy-otrophic lateral sclerosis. Virus isolated from CSF, blood and brain resembles Encephalomyocarditis virus. Relation to disease not established.

Casals J (1963) Nature 200, 339

vinblastine An alkaloid derived from the periwinkle plant, Vinca rosea. Inhibits synthesis of cellular RNA and protein. Mitosis is arrested in metaphase and there is attachment and uncoating of infecting viruses but no viral macro-molecules are made.

Vinces virus (VINV) A strain of Caraparu virus in the genus Bunyavirus, belonging to the group C virus group. Isolated from mosquitoes in Ecuador.

Calisher CH et al (1983) Am J Trop Med Hyg 32, 877

Vindeln/L20Cg/83 virus A strain of Puumala virus in the genus Hantavirus.

Viper retrovirus (VRV) The type species of the reptilian virus group, in the genus Gammaretrovirus. First observed in a cell line VSW, established from the spleen of an Asian pit viper, Vipera russelli. Two further strains have been obtained from two different viper heart cell lines, neither of which were producing virus particles at first but spontaneously commenced to do so. These strains have been designated VV-VH-2 and VV-VH-3 to distinguish them from the original strain VV-VSW. Characterization of VRV showed a reverse transcriptase with a preference for Mg2+ and a genome similar in size to that of murine retroviruses.

Andersen PR et al (1979) Science 204, 318 Lunger PD and Clark HF (1978) Adv Virus Res 23, 159

Viracept Trade name for an orally active antiviral drug, nelfinavir, which inhibits HIV protease.

viral deformity virus (VDV) A disease first seen in 1993 in young yellowtail in Japan. A birnavirus that is not infectious pancreatic necrosis virus (IPNV) was isolated from diseased fish.

Nakajima K and Sorimachi N (1996) Fish Pathol 31, 87

viral epidermal hyperplasia A disease of young flounder Paralichthys olivaceu. First described in 1989 in Japan. Herpesvirus-like particles have been seen in diseased tissues.

viral erythrocytic infection A seasonal infectious disease of Mediterranean sea bass, Dicentrarchus labras, which is probably caused by a species in the family Retroviridae.

Pinto RM et al (1995) Arch Virol 140, 721

viral hemorrhagic fever viruses of humans A term with no precise meaning applied to a group of viruses which cause diseases characterized by fever and hem-orrhagic phenomena resulting from various forms of capillary damage. They usually have natural animal hosts (arthropod- or rodent-borne), and humans may become infected through venturing into the ecological domain of the virus and its natural host. The term began to appear in the literature in the early 1950s in discussions of Korean hemorrhagic fever virus. Examples are given in Table V2.

Shelokov A (1970) J Infect Dis 122, 560 Simpson DIH (1978) Bull Wld Hlth Org 56, 819

Viral hemorrhagic septicemia virus (VHSV) A species in the genus

Table V2. Examples of viral hemorrhagic fever viruses of humans

Virus

Means of transmission

Chikungunya virus

Mosquito-borne

Dengue virus

Mosquito-borne

Rift Valley fever virus

Mosquito-borne

Yellow fever virus

Mosquito-borne

Crimean-Congo hemorrhagic fever viruses

Tick-borne

Kyasanur Forest disease virus

Tick-borne

Omsk hemorrhagic fever virus

Tick-borne

Guanarito virus

Rodent-borne

Junin virus

Rodent-borne

Korean hemorrhagic fever virus

Rodent-borne

Lassa fever virus

Rodent-borne

Machupo virus

Rodent-borne

Sin Nombre virus

Rodent-borne

Sabia virus

Rodent-borne

Marburg virus

Unknown

Ebola virus

Unknown

Novirhabdovirus, first recognized in the Danish village of Egtved. Formerly believed to be confined to portions of the European continent, but in 1988 VHSV was isolated from adult chinook, Oncorhynchus tshawytsha, and coho, O. kisutch, salmon returning to two hatcheries in the north-western part of Washington State, USA. Subsequently isolated from many species from the North Sea and the Baltic Sea. European and USA isolates are thought to be of independent origin. Causes a severe and often fatal hemorrhagic septicemia in salmonids, both young and sexually mature fish. Rainbow trout are severely affected but other trout are susceptible to inoculation. Pike, Esox lucius, turbot, Scophthalmus maximus, Atlantic cod, Gadus morhua, Pacific cod, Gadus macro-cephalus and herring Clupea harengus pallasi, and several other fish species are susceptible. They lose appetite, become apathetic or swim abnormally. Abdomen is swollen, gills pale, with hemorrhages in the gill filaments, around the eyes and at fin bases. VHSV can be propagated in cultures of trout ovarian cells: best at 12-14°C and not above 22°C. Complete sequence analysis of several strains shows that the marine and freshwater viruses differ by as few as 10 amino acid substitutions.

Synonyms: hemorrhagic septicemia virus of fish; salmonis virus; viral hemorrhagic septicemia of trout virus; Egtved virus; Atlantic cod ulcus syndrome virus.

Bernard J et al (1992) J Gen Virol 73, 1011 Betts AM and Stone DM (2000) Virus Genes 20, 259

Virazole Trade name for ribavirin.

viremia The presence of virus infectivity in the blood. May occur as free infectious particles in the plasma or as infected peripheral blood cells. Occurs transiently in many infections but virus is rarely isolated, probably because the viremia only occurs very early in the infection. Chronic viremia occurs in a few infections: for example, in aleutian disease of mink, Hepatitis B or C or Human immunodeficiency virus infections in humans and Lactate dehydrogenase-ele-vating virus infection in mice. Infective virus may also circulate as virus-antibody complexes and immune complex disease may occur.

Virgin River virus (VRV) A strain of Tacaiuma virus in the genus Bunyavirus, belonging to the Anopheles A virus group.

virion Synonym for virus particle.

viroceptors Virus gene products, especially of large DNA viruses, that have homol-ogy with cellular receptors for cytokines, and inhibit cytokine-induced defense mechanisms.

McFadden G and Graham K (1994) Semin Virol 5, 421

virus virogenes Cell DNA sequences carrying information for production of components of virus particles. See endogenous virus.

virogenic cells Cells carrying a latent viral genome and not producing infective virus, but able to do so on being grafted into an animal of a suitable species, or on co-cultivation or fusion with a cell of a different species, or induction by irradiation or certain chemicals.

viroid A term introduced by Altenburg (1946) to designate hypothetical sym-bionts, akin to viruses, supposed to occur universally within the cells of animals and to give rise by mutation to viruses. Experimental verification of this theory has not materialized. Diener (1971) proposed that the term be redefined and used as a name for agents such as potato spindle tuber 'virus', a small infective nucleic acid with no capsid protein and too little nucleic acid to code for its own replication. No helper virus has been demonstrated. Viroids are the smallest known agents of infectious disease, consisting of a highly structured RNA molecule 246-375 nt in length in different viroids. More than 20 viroids have been completely sequenced. The RNA is not translated but is replicated by pre-existing host enzymes. Viroids have as yet only been found in plants where they induce economically important diseases. One example of a small RNA genome in vertebrate virology is the Hepatitis delta virus, but this does not replicate autonomously, and requires a helper virus (Hepatitis B virus).

Altenburg E (1946) Am Natur 80, 559 Diener TO (1979) Science 205, 859 Taylor JM (1998) In Virology, vol. 1 of Topley and Wilson's Microbiology & Microbial Infections, Ninth edition, edited by BWJ Mahy and L Collier. London: Arnold, p. 775

virokines Virus gene products that have functional homology with cytokines and affect cellular function in a similar way.

Palumbo GJ et al (1994) J Virol 68,1737

virolysis Irreversible structural damage which may go as far as complete disintegration of virus particles. When certain enveloped viruses are exposed to specific antiserum in the presence of complement at +2°C there is neutralization of infectiv-ity but no gross structural damage. However, at 37°C there is virolysis, presumably mediated by late-acting components of complement.

Radwan AI et al (1973) Virology 83, 372

viropexis The engulfment of virus particles by cells. A form of pinocytosis. An active process by the cell and an important method of virus penetration. Synonym: engulfment.

viroplasms A term used to describe inclusion bodies in rotavirus-infected cells which are the sites for assembly of subviral particles enclosing the 11 segments of mRNA which are then replicated to form double-stranded RNA molecules.

viroporin A term introduced by Carrasco to describe virus proteins that enhance cell membrane permeability.

Carrasco L (1993) Adv Virus Res 45, 61

virosomes Liposomes with viral proteins on their surfaces. For example, the hemagglutinin and neuraminidase surface units of Influenza virus A can be removed from the virus and relocated on the surface of liposomes. Such virosomes can be used as antigens. Liposomes are particles consisting of aqueous dispersions of phospholipid in the form of either multi- or unilamellar lipid bilay-ers. They are formed when a dried film of a phospholipid such as lecithin is shaken with buffer and then sonicated.

Morein B and Simons K (1985) Vaccine 3, 83 Morein B et al (1978) Nature 276, 715

virostatic Able to prevent viral replication.

virucidal Causing inactivation of a virus.

virulence The capacity of a virus to cause disease in the host.

viruria Presence of infectious virus in the urine.

virus Infectious units (obligate intracellular parasites) consisting of either RNA or DNA enclosed in a protective coat. Viruses are not organisms, and contain no functional ribosomes or other cellular organelles and no energy-producing enzyme systems, although many viruses contain enzymes involved in nucleic acid transcription. They cannot grow in size but their nucleic acid contains the necessary information for their replication in a susceptible host cell. This cell may provide some of the enzymes necessary for viral replication but its main function is to provide the energy-producing systems. The host cell may or may not be destroyed in the process of viral replication and release. The Latin noun virus is defective, i.e. does not have a full set of case-forms, singular and plural. Ancient grammarians used only the singular form. Modern usage has made the word a countable entity and modern languages each pluralize it in their own fashion.

Smutny RJ (1999) ASM News 65, 388

virus III Synonym for leporid herpesvirus 2. Nesburn AB (1969) J Virol 3, 59

virus assembly Formation of a virus particle from its constituent parts. The process can vary from the autoassembly of protein subunits around viral nucleic acid, to assembly of complex viruses at cell membranes.

virus de rue renforcé A term applied to certain strains of Rabies virus (street virus) of unusual virulence.

virus induction Activation of a provirus to replicate complete virus. May occur spontaneously or be promoted by various factors, e.g. exposure to compounds such as idoxuridine.

virus-like particle Structure resembling a virus particle but which has not been demonstrated to be infectious.

virus N A strain of avian influenza A virus.

virus replication The process of forming progeny virus from input virus. It involves the expression and replication of the viral genomic nucleic acid and the assembly of progeny virus particles.

virus rescue See reactivation.

virus X of bovine serum A possible species in the genus Orbivirus. Found in a culture of BHK21 hamster cells and thought to have been derived from the bovine serum in the medium.

Verwoerd DW (1970) Prog Med Virol 12, 192

virusoid A term used to describe single-stranded RNA satellite viruses. Consist of a single-stranded RNA genome encap-sidated in protein structures which are provided by the helper virus. Most species are found in plants but one, Hepatitis delta virus, infects humans.

virus transport medium A solution used to preserve virus infectivity as much as possible during transport from a field location to a virus laboratory. It contains sterile buffered salt (e.g. 0.9% saline in phosphate buffer at pH 7.4), protein (usually bovine serum albumin), antibiotics and a pH indicator. See transport medium.

visceral disease virus Synonym for Human herpesvirus 5 (human cytomegalovirus).

visceral lymphomatosis of fowls An old term for the leukoses involving the viscera: Marek's disease and the leukosis-sarcoma group of diseases.

Visna/maedi virus (strain 1514) (VISNA) (Icelandic: visna = shrinking or wasting) A species in the genus Lentivirus, in the ovine/caprine lentivirus group. Causes a slowly progressive demyelinating disease of the CNS in sheep. Early signs are lip tremor and abnormal carriage of the head. Later there is progressive paralysis and death. The disease was imported into Iceland in 1933 with a shipment of 20 Karakul rams from Germany, intended to provide a new gene pool for the relatively isolated Icelandic sheep. Within 2 years the two diseases maedi (dyspnea) and visna (wasting) emerged. Sporadic cases were reported between 1935 and 1951 in Iceland, when an extensive slaughter policy was started to eliminate pulmonary adenomatosis and maedi as well as visna. Localized outbreaks of maedi occurred again between 1958 and 1965 but there was no recurrence of the other two diseases. Virion is 85nm in diameter

Vranica virus with a dense core. Genome RNA is related to that of Caprine arthritis encephalitis virus with homologies of 75-78% in the gag and pol genes, and 60% in the env gene. Transmission requires close contact and seldom occurs between sheep outdoors. Antibodies are formed but virus is not eliminated from the animal. The virus undergoes antigenic change and antibodies are formed to the new antigenic type. This can occur several times. These changes appear to be limited and are probably not due to mutations so much as selection of strains expressing various alternative antigens. Replicates in cultures of sheep and human cells. Giant cells and CPE occur in 2-3 weeks. Transforms mouse cells in vitro. On injection into mice these cells will form sarcomas from which the virus can be rescued. See also progressive pneumonia of sheep. Synonyms: chronic progressive pneumonia of sheep virus; Zwoegerziekte virus; La Bouhite; Graaf Reinet; ovine progressive pneumonia.

Narayan O et al (1993) In The Retroviridae, vol. 2, edited by JA Levy. New York: Plenum Press, p. 229

Sonigo P et al (1985) Cell 42, 369 Zink MC (1992) Semin Virol 3, 147

Volepox virus (VPXV) A species in the genus Orthopoxvirus isolated from a Pinon mouse, Peromyscus truei, and a vole, Microtus californicus, in California, USA. More closely related to raccoon poxvirus than to Old World poxviruses.

Knight JJ et al (1992) Virology 190, 423 Regnery DC (1987) Arch Virol 94, 159

vole poxvirus (VPV) An unassigned virus in the family Poxviridae. Isolated in Turkmenia from Microtus oeconomus and in Canada from Microtus pennsylvan-icus.

vomiting and wasting disease of pigs virus Synonym for Porcine hemagglutinat-ing encephalitis virus.

v-onc General term for a viral oncogene.

von Magnus phenomenon A phenomenon observed during repeated passage of Influenza virus A at high multiplicity. Results in a progressive increase in the proportion of defective virus particles produced.

von Magnus P (1954) Adv Virus Res 2, 59

VPg Abbreviation for virion protein, genome-linked. A small virus-coded protein attached through a phosphodiester linkage from an amino acid (e.g. the phenolic hydroxyl group of a tyrosine residue in poliovirus) to the 5' end of the virion nucleic acid of certain viruses, e.g. picornaviruses.

Vpr protein A protein induced in cells infected with Human immunodeficiency virus type 1 which upregulates HIV gene expression.

Vpu protein A non-structural membrane-associated protein induced in cells infected by Human immunodeficiency virus (HIV) type 1 which functions during virus release and also acts to downregulate the CD4 glycoprotein by causing its retention and degradation in the endoplasmic reticulum.

Vpx protein A protein component of the virion of Human immunodeficiency virus (HIV) type 2. Non-essential for replication in vitro. Exact function unknown.

Vranica virus A strain of Puumala virus in the genus Hantavirus. Isolated from a bank vole in Bosnia.

Reip A et al (1995) Arch Virol 140, 2011

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