ALPHA VIRUSES

From Big Medical Encyclopedia

ALPHA VYRUSA — RNK-soderzha-shchiye viruses of the sort Alphavirus (earlier — antigenic group A) this. Togaviridae. Recently it is offered to allocate And. - century in independent this. Alphaviridae. And. - treat ecological group of an arbovirus century (see), And from them cause the arboviral diseases (see) proceeding with the phenomena of encephalitis, fever it is frequent with rash and an arthralgia. The greatest medical value among And. - have viruses of east, western and Venezuelan encephalomyelitis of horses century (see Encephalomyelitis horse), Chikungunya (see. Tropical mosquito viral fevers]), Sindbis (standard virus of the sort Alphavirus). The first three from them are important also for veterinary science.

Virions A. - have spherical shape, cubic type of symmetry, the size 60 century — 70 nanometers, on a surface ledges 6 — 10 nanometers long are located. The molecular weight (weight) of virion 5-106, floating density

is 1,18 — 1,24 g/cm3 in a gradient of sucrose, coefficient of sedimentation 250 — 275S. Virion has an isometric nucleocapsid of 33 in size — 40 nanometers, with a floating density in a gradient of sucrose

of 1,24 g! in cm3 and in coefficient of sedimentation 140 — 143S. The nucleocapsid and virion are icosahedrons with various triangular numbers (T-3 for a nucleocapsid, T-4 for virion). The nucleocapsid is put into the lipoprotein cover consisting of lipids of a cell of the owner and 3(2) virusospetsifichesky glycoproteins — El, E2 and EZ with a molecular weight respectively 50-103, 50-103 and 10-103. Protein E1 defines specificity within an antigenic complex, and E2 is virusospetsifichesky (participates in a neutralization test). Core protein C about a pier. weighing 30 — 34 kilodalton does not influence antigenic properties of a virus. The genome is presented one-filamentous infectious (plus thread) of linear RNA about a pier. the weight making 6% of weight of virion and in coefficient of sedimentation 42 — 50S, contains edges apprx. 13 thousand nucleotides. The polynucleotide chain of RNA includes 29% of adenine, 20 — 22% of uracil, 25% of guanine and 25% of a tsitozin. RNA behaves as a molecule with the high content of secondary structures. In replikativny cycle RNA is an initiator inf. process also serves as a matrix for creation of affiliated copies.

During the maturing And. - there are products of virus glycoproteins in cellular membranes, assembly of nucleocapsids in cytoplasm of cells from virionny RNA and protein C, an otpochkovyvaniye of nucleocapsids through the cellular membranes (inclusion of glycoproteins of E1 and E2) modified by a virus, budding of mature virions century. Process of a morphogenesis occupies the Replikativny cycle apprx. 20 min. lasts 4 — 16 (a maximum of products) hours. At infection And. - century of cultures of cells of chicken embryos, V NK-21, VERO and, etc. the cytopathic effect of viruses is expressed. By the most sensitive and universal method of allocation And. - century intracerebral infection of mice is.

And. - are sensitive to effect of trypsin, high temperature, UV rays century, are stable at

pH 6,5 — 9,0, have the hemagglutinating and hemolitic properties. Many And. - are good inductors of interferon century (see) and are highly sensitive to its action.

Alpha viruses (26 viruses) on the basis of antigenic interrelations are grouped (except for two viruses) in antigenic complexes: Venezuelan (5 viruses), western (7 viruses) and east (3 viruses) encephalomyelitis of horses, Semliki's wood (9 viruses). And. - are widespread on all continents century, it is preferential in the equatorial and subequatorial climatic zones, and nek-ry in tropics, subtropics and a moderate belt.

On the American continent 13 alpha viruses are known. Mukambo's viruses, Evergleyds, Mayaro, To-nat cause the sporadic diseases which are followed by fever. The virus of the Venezuelan encephalomyelitis of horses serves as the reason of epidemic outbreaks of a disease at people and the epizooty among animal (horses) arising from time to time in the countries of Central and South America. At the person the disease is shown

3 — 5-day fever, a headache, nausea, muscular pains, the phenomena of encephalitis (in 4% of cases). The natural centers are located in low territories. The main carriers — mosquitoes of the sorts Aedes serratus, Mansonia titillans, etc.; owners — vertebrata (rodents, monkeys). The western encephalomyelitis of horses (epidemic flashes and epizooty) is widespread preferential in the USA, to the West from Mississippi. A wedge, manifestations are various: fever, the phenomena of encephalitis up to paralyzes (in 15% of cases). The main carriers — mosquitoes of the sort Culex tarsalis; owners — wild birds. The virus of east encephalomyelitis of horses usually causes sporadic incidence of people and an epizooty among horses in Eastern States of the USA, and also in other countries of North, Central and South America. In a wedge, a picture the phenomena of encephalitis prevail. The main carriers are mosquitoes of the sort Culiseta melanura, owners — wild birds.

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V to Africa 6 alpha viruses are widespread, three of to-rykh cause epidemic flashes (O'Nyong-nyong, Chikungunya) and the sporadic diseases which are characterized by fever, rash and an arthralgia (Sindbis). The main carrier of fever of Chikungunya — mosquitoes of the sort Aedes aegypti, fever O'Nyong-nyong — mosquitoes of the sort Anopheles funestus, fever Sindbis — mosquitoes of the sort Culex. From 4 known in Australia and Oceania And. - century only a virus Ross River causes the epidemic outbreaks of fever with rash and an arthralgia. In Eurasia 7 alpha viruses, including viruses of Chikungunya, pathogenic for people, and Sindbis are known. In the USSR from And. - century viruses of Kyzylagach, Sindbis, U62-33 and Semliki's woods are widespread. A virus antigenically related to a virus Sindbis, causes the Karelian fever which is proceeding with rash and an arthralgia, often getting hron. current.

Carriers And. - century mosquitoes of the sorts Culex, Culiseta, Aedes, Mansonia, Anopheles, Trichoproso-pon, Psorophora, Haemagogus, an in some cases — bird's bugs of Oeci acus vicarius are; owners — vertebrate animals, especially often birds and rodents. Birds during seasonal migrations carry out transcontinental transfer of a row A. - century. Epidemic flashes among people are preceded by an epizooty among wild birds, then among synanthropic and farm animals.

See also Viruses.

Bibliography: The general p private virology, p and edition V. M. Zhdanova and S. Ya. Gaydamo-lich. t. 2, page 49, M., 1982; Arboviruses in iho mediterranean countries, ed.

by J. Vesenjak-Hirjan a. o., Stuttgart — N. Y., 1980; International catalog of arboviruses, ed. by T. O. Berge, Atlanta, 1975; Porterfield J. S. a. o. Togaviridae, Intervirology, v. 9, p. 129, 1978; The Togaviruses, biology, structure, replication, ed. by R. W. Schlesinger, N. Y. a. o.,

1980. D. K. Lvov.

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