PAPOVA VIRUSES (Papovaviridae) — the family combining the DNA-containing group of viruses. The name is formed of the first syllables of names of the viruses which were originally making this group: a pas (pa) — a virus of papilloma (papilloma), on (po) — a virus of a polioma (polyoma) and va (va) — a monkey vakuoliziruyushchy virus.
Items cause latent and chronic forms of an infection. Oncogenous properties of most of them are revealed in experiments on animals. Nek-rye P. cause development of primary malignant tumors in newborn rodents soon after their infection. Under natural conditions cause single benign tumors in wild and domestic animals of P., to-rye can malignizirovatsya; Items have high specificity in relation to the owner. P. on animals parasitize; nek-ry of them, napr, viruses of papilloma, affect also the person (see. Papilloma, papillomatosis ).
Virions P. represent small isometric particles. The cover at P. is absent, the capsid has the slanting ikosaedrichesky structure constructed of 72 capsomeres representing hollow cylinders 7,5 — 10 nanometers long. Also filamentozny forms P. and empty spherical particles (they have no DNA) with a floating density of 1,29 g/cm are described 3 (fig. 1).
P.'s genome is presented by a cyclic molecule two-filamentous super spiralizovannoy to DNA (fig. 2) with a molecular weight (weighing) 3 — 5 X 106 dalton. Nucleinic to - that, allocated from many viruses, has the infectious and transforming properties; the rupture of one of chains does not influence these properties.
Item of a termostabilna: heating at t ° 50 ° within an hour is practically not reflected in a titre of viruses and only at t ° 70 — 80 ° the full inactivation is reached. P.'s heat stability decreases at addition of salts of magnesium. They are steady in acid medium (to pH 3,0). Carbohydrates and lipids in virions are not found out that, in particular, explains their nonsensitivity to zhirorastvoritel (ether). Dodetsilsulfat of sodium breaks integrity of structure of virions. A row P. has the hemagglutinating activity, interacting with the receptors of erythrocytes destroyed by a neuraminidase. The called enzyme at P. is absent. Group antigens at P. are not revealed.
The cycle of a reproduction of P. is carried out in kernels of the infected cells of vertebrata, long course of this cycle having long stage of latency is characteristic: the new virus develops only in 24 hours, the maximum accumulation of a virus and cytopathic changes in culture of cells are noted during from 1 to 2 — 3 weeks.
Two sorts are a part of family P.: papillomaviruses and poliomavirusa.
Sort of papillomaviruses — Papillomavirus (Latin papilla of pacifiers + — oma). Type-species — a virus of papilloma of rabbits (Shoup's virus). Also viruses of papillomas (warts) of the person and various animals are a part of a sort: (cows, dogs, hamsters, etc.) - At certain owners various serotypes of causative agents of papillomas reveal that, apparently, will be used during the development of classification of viruses of this sort.
Papillomaviruses have in the diameter of 55 nanometers, weight 28 X Yu6 dalton * are characterized with a floating density of 1,34 g/cm 3 and coefficient of sedimentation of 296 — 300 S. The molecular weight of DNA (makes apprx. 10% of weight of virion) 5 X 106 dalton, the content of guanine and a tsitozin from 41% (a virus of the person) to 48 — 49% (a virus of rabbits). Infectivity of DNA is established only for a virus of papilloma of rabbits. The method of hybridization does not reveal a homology between DNA of various viruses of this sort.
Proteins of papillomaviruses are studied badly. Cross serol, reactions in immunodiffusion tests of viruses of papillomas of dogs, the person, cows and rabbits give the negationist the ny answer that testifies to lack of type-specific is scarlet-tigenov.
Process of a reproduction of papillomaviruses is studied a little. It is known that the virus is formed in a kernel where its DNA is synthesized and structural proteins accumulate. Pathogenicity of each virus is limited to its feral host and shown by formation of papillomas, to-rye can regenerate in carcinomas. Infection of animals happens through traumatic injuries of skin. The possibility of mechanical transfer of a virus of papilloma of rabbits is proved by arthropods.
The virus of papilloma of rabbits is eurysynusic among wild American rabbits (Sylvilagus floridanus), at to-rykh it causes large, is quite long the existing keratizirovanny tumors of skin («horn») having an epithelial origin. Domestic rabbits (Oryctolagus cuniculus) easily catch this virus owing to what also their similar tumors are developed. Unlike papillomas of wild rabbits, in to-rykh virions form, in papillomas of domestic rabbits the reproduction of this virus is absent. 4 — 9 months of papilloma later regenerate in planocellular cancer that is observed as in an experiment at wild and domestic rabbits, and under natural conditions at wild rabbits. In the formed carcinomas viruses usually are not synthesized any more. Feature of a virus of papilloma of rabbits is the possibility of allocation infectious nucleinic to - you from cells of a tumor, free of the corresponding virus.
The virus of papilloma of cattle is morphologically identical to a virus of papilloma of rabbits. Both the intact virus, and DNA emitted from it transform bull and mouse cells (with a low performance).
The virus of papilloma of the person causes developing of contagious papillomas and is morphologically identical to the papillomaviruses called above. Frequency of transformation of cells of the person in culture is extremely low. Papillomas arise from one infected cell of a basal epithelium, cells share, and clonal descendants of the stem infected cell form papilloma. Involvement of the next basal cells in papilloma does not happen, obviously, owing to absence in them an infectious virus, to-ry it is found only in the cells which began to be keratinized.
Sort of poliomavirus — Polyomavirus (Greek poly is a lot of + - oma). Type-species — a virus of a polioma of mice (poliomavi-rus type 1, virus SE полиомы of mice). Are a part of a sort also monkey vakuoliziruyushchy virus (OB40 or SV40 where S from English simian monkey, and V from virus) — poliomavirus type 2; virus K (poliomavirus type 3); rabbit vakuoliziruyushchy virus (poliomavirus type 4); the VK virus allocated from urine of the person after transplantation of a kidney (poliomavirus type 5); the GC virus allocated from the person with a progressive multiple leukoencephalopathy (poliomavirus type 6).
Studying of poliomavirus of the person began in 1971 when they were for the first time found in tissues of the person. Apprx. 70% of adults have to them antibodies. Consider that primary infection of a poliomavirusama occurs in the period of early children's age. In the subsequent poliomavirusa are at the person in an abeyance and can come to light at decrease in the immune status owing to hron, diseases, inborn defects, pregnancy or chemotherapy. The virus is localized in a brain and urinary tract. Allocation of a virus from an organism happens to urine. Etiol, a role of poliomavirus in pathology of the person is not clear. Are suggested about communication of the VK virus with pathology of kidneys. The G C virus was repeatedly allocated from patients with the progressing multiple leukoencephalopathy. There is a hypothesis that the GC virus is the causative agent of a demyelinating disease with a lethal outcome. The B K and G C viruses caused in an experiment development of tumors at a lab. animals, however for the person the oncogenous potentiality of these viruses is not established.
Poliomavirusa have in the diameter of 45 nanometers, weight 20 — 25 X Yu6 dalton, with a floating density of 1,34 g/cm are characterized 3 and coefficient of sedimentation 220 — 240S. The molecular weight of DNA (makes apprx. 12% of weight of virion) 3 X 10 6 dalton; content of guanine and a tsitozin from 41% (a monkey vakuoliziruyushchy virus) to 49% (a virus of a polioma of mice), all in DNA apprx. 5000 couples of the bases. DNA of nek-ry poliomavirus has both the infectious, and transforming properties.
Proteins of poliomavirus contain polypeptides 6 or 7 of types, 70 — 80% of total quantity of protein are the share of one of to-rykh. Three components of protein with the smallest molecular weight (15 000, 14 000 and 12 000 dalton), rather rich with the main amino acids, are most strongly connected with virus DNA that allows to consider them internal virus proteins (i.e. localized in virion). Believe that these proteins are coded by a cellular genome and are included a virus particle in the course of its assembly. Other proteins — kapsidny are also coded by a virus genome. The virus of a polioma of mice and a monkey vakuoliziruyushchy virus do not find an antigenic affinity in serological tests, but the virus of a polioma of the person gave cross-reactions with the monkey vakuo-lyseing virus. The virus of a polioma of mice at t ° 4 ° agglutinates erythrocytes of Guinea pigs whereas the monkey vakuoliziruyushchy virus has no this ability.
Poliomavirusa in kernels of the infected cells are reproduced. In laboratories for studying and accumulation of a virus of a polioma of rabbits use cells of embryos of mice (ZTZ), and for a monkey vakuoliziruyushchy virus — a cell of a kidney of the African green monkey and a kidney of a rabbit (BSC-1) where virions of viruses (fig. 3, 4) are formed. Various forms of phenomena of genetic interaction, except multiple reactivation are described. Cause an inapparantny infection in animals of a poliomavirusa, under certain conditions they are oncogenes. These viruses show oncogenous activity and at animals who are not their feral hosts, mainly at immunodeficient newborn hamsters. Poliomavirusa cause transformation of cells in culture. The transformed cells differ from initial in the morphology (fig. 5).
In process carcinogenesis (see) virus DNA it is built in a genome of the transformed cells, and at infection of the based cells there is a stimulation of synthesis of cellular DNA.
Are most studied a virus of a polioma of mice (poliomavirus type 1) and a monkey vakuoliziruyushchy virus (poliomavirus type 2). The virus of a polioma of mice is often called just a virus of a polioma. It is endemic in populations of wild and laboratory mice, at to-rykh this virus does not cause formation of spontaneous tumors. Tumors arise only at newborn mice in a lab. conditions. The virus of a polioma entered to newborn mice causes development in them of the various, histologically differing tumors (sarcoma and fibroma). This virus causes also developing of tumors and in nek-ry other animals if infection is carried out soon after the birth: sensitivity to such infection is especially high at hamsters and remains at them to 3 weeks age. Tumors at hamsters come to light for the 7th day after infection, most often it is sarcomas of kidneys; at mice of a tumor come to light not earlier than the 6th week. Sarcoma is induced also at rats whereas at rabbits multiple benign hypodermic fibromas are formed, to-rye regress within 4 months. Tumors do not contain a virus, and under a supermicroscope in cells of a tumor it is not possible to find virus particles.
The monkey vakuoliziruyushchy virus was revealed as a contaminant of cultures of cells of kidneys of monkeys, to-rye were used for production of a poliomyelitic vaccine. As this virus causes in the cells infected with it a peculiar cytopathic effect — vacuolation of cytoplasm and kernels, he also received the name a vakuoliziruyushchy virus. This virus causes tumors in newborn hamsters and rats. The cultivated cells of many animal species infected with this virus can be transformed in the conditions of in vitro. At hamsters development of tumors of several types is observed: hypodermic fibrosarcomas, ependymomas, nefroblastoma. Usually the virus manages to be observed only in separate tumors. However by means of various methods (x-ray and UF-radiation, processing hydrogen peroxide and mitomitsiny, cultivation of neoplastic cells with sensory cells) possible to find viruses more often. Concerning a virus of a polioma of mice all called methods were ineffectual, as distinguishes this virus from a monkey vakuoliziruyushchy virus. Carriers of a monkey vakuoliziruyushchy virus are monkeys a Rhesus factor and tsinomolgus. Under natural conditions infectiousness of these monkeys does not exceed 10%, but owing to close contact between them infectiousness sharply increases in bondage, including also green African monkeys are infected, to-rye are under natural conditions free from this virus. For the person this virus nepatogenen though antibodies to it were found in nek-ry persons, napr, employees have laboratories, adjoining to this virus.
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