CORONAVIRUSES

From Big Medical Encyclopedia

CORONAVIRUSES (Coronaviridae) — the family of viruses combining the RNA-containing polymorphic viruses of average size on which surface there are characteristic fringed fibers. Originally the viruses entering into this family were carried to myxoviruses, but results of the subsequent researches gave the grounds (1968) to allocate them in independent taxonomical group. Patrimonial division of family K. it is not defined.

To. are everywhere widespread on the globe and are etiol, a factor of acute respiratory diseases of the person, inf. bronchitis of birds, hepatitises of mice, pneumonia at rats, a gastroenteritis and encephalomyelitis at the pigs who are often coming to an end at animals with death.

To. contain RNA, edges its molecular weight 9 X 10 is characterized by the odnotyazhevy not segmented structure, 6 dalton. RNA K. has no infectivity. By means of an electrophoresis in polyacrylamide gel it is revealed that To. contain 6 or 8 polypeptides which molecular weight makes at To. the person from 13 000 to 210 000 dalton, at others To. — from 14 000 to 180 000 dalton. Some proteins of virions K. are glycoproteins. In virions K. the person the RNA-dependent RNA polymerase is found. A number of strains To. contains Hemagglutinins.

Fig. 1. The diffraction pattern of the coronavirus got from cultural liquid of organ culture of a trachea of an embryo of the person: on the surface of virions fringed fibers are visible — are specified by shooters (To. McIntosh, 1974).

Virions K. pleomorfna, diameter various To. varies from 80 to 220 nanometers. For To. existence of a cover with fibers (fig. 1), more rare, than at an influenza virus is characteristic. Fibers are attached to virion by means of narrow «stalk» and extend by the distal end, reminding a solar crown during an eclipse (the name of family from here). Length of fibers makes 12 — 24 nanometers. Virions K. have a lipidic cover. The nucleocapsid having an appearance of a spiral is twirled freely, to its dia. 55 nanometers. The floating specific density of virions is equal in solutions of sucrose 1,18 — 1,19 g/ml, coefficient of sedimentation To. person 374-416S.

Property K is characteristic. — their sensitivity to zhirorastvoritel. Influence both ether, and chloroform considerably reduces infectivity of these viruses. Stability To. at a certain temperature of storage depends on amount of virions in units and on existence in the environment of ions and colloids. Nevertheless it is established that the inactivation of viruses at t ° 56 ° comes to the end in 10 — 15 min., at t ° 37 ° their infectivity remains several days, and at t ° 4 ° — several months. To. are steady against freezing and thawing, at t ° — 60 ° below within several years keep inf. properties without change, are stablest at pH 6,0 — 6,5.

Fig. 2. The diffraction pattern of cytoplasm of cells of W1-38 infected with a coronavirus of the person, a strain 229 E: the synthesized crescent structures (1) and the budding virions (2) coronaviruses in the field of large vacuoles are visible (To. McIntosh, 1974).

To. breed in cytoplasm of the infected cells. At the same time affiliated virions appear in 4 — 6 hours after infection, and the maximum manifestation of infectivity associated with cells is noted in 12 — 36 hours. At electronic microscopic examination infected To. cells quite characteristic morphology comes to light To.: near cytoplasmatic vacuoles emergence of the crescent structures representing the synthesized virions is observed, and in the vacuole there are budding virions (fig. 2). Budding through cytoplasmatic vacuoles is characteristic feature To., distinguishing them from the myxoviruses budding through a plasma membrane.

Type-species To. it is considered to be a virus inf. bronchitis of birds. In family K. also enter To. the person — respiratory viruses, a virus of hepatitis of mice, a virus of a transmissible gastroenteritis of pigs, a virus of a sialodakrioadenit of rats, a virus of a blue comb of turkey-cocks, the virus of neonatal diarrhea of calfs Hemagglutinating a virus of encephalomyelitis of pigs. On antigenic properties the called viruses of a geterogenna. In the immunodiffusion test at them it was possible to reveal from one to four precipitation lines. However between certain human (a serotype of OS 43) and mouse strains there are some antigenic bonds.

All To. ability to fix a complement in the presence of the hyperimmune serums or serums received from had is inherent.

Only two look To. (To. the person, strains of OS 38 and OS 43 and the Hemagglutinating virus of encephalomyelitis of pigs) cause hemagglutination; at the same time To. the person erythrocytes of the person and monkeys only at t agglutinate ° 4 ° whereas erythrocytes of hens, rats and mice they agglutinate both at t ° 4 °, and at the room temperature and at t ° 37 °. Ability to cause hemagglutination was broken after processing by ether and trypsin. Moreover, it is shown that as a result of influence on called To. bromine of l not only disturbance of hemagglutination, but also disturbance komplementfiksiruyushchy and inf happened the Ainu destroying fringed fibers.

K. K. activities can breed only in a limited circle of cellular cultures, and during the use of the cells which are grown up in the form of a monolayer it is possible to receive very poor harvest of a virus. To. various origin breed, as a rule, only in the cells corresponding to their origin. So, initially allocated bird's To. breed only in cells of birds, mouse To. breed only in tissues of mice; the same can be told about rat and pork strains. In chicken embryos breed only To. inf. bronchitis of birds. To. the person breed, showing shtammovy distinctions, in human diploid cells, in cells of L-132 (the cellular line received from an easy embryo of the person), and also in cells of HeLa, cells of primary culture of a kidney of an embryo of the person and other cells of the person. The reproduction of some viruses can be revealed only in organ cultures (e.g., a reproduction of a virus of the person in explants of an epithelium of a trachea of an embryo of the person). Tsitol, methods of any inclusions in the struck cells does not come to light. It is necessary to emphasize, as the cytopathic effect To, is shown not in all cases. Some viruses (e.g., To. the person, a strain of B814) can be found only by means of a supermicroscope or by an interference with other viruses (for called as an example To. the person such interfering virus is the ECHO virus of the 11th type). At a covering of cells methyl cellulose possible to observe plaque formation in cultures of cells of L-132 and Wl-38.

In an experiment it was possible to try to obtain adaptation To. to cells in which they initially were not reproduced. So, synthesis of a virus inf. bronchitis of birds observed in primary culture of cells of a kidney of a monkey, and To. the person — in culture of cells of a kidney of a monkey and an organism of mice suckers.

To. the person are, as a rule, causative agents of acute diseases of upper respiratory tracts, however cases of bronchitis and pneumonia of a koronavirusny etiology are known (at children). Exact establishment of a role of this virus in comparison with epidemiol, data is extremely complex challenge in connection with wide variability of strains and labor input of a diagnostic method.

To. usually allocate from a nasal secret, scrapings and rinsing waters of a nasopharynx, using the corresponding cellular or organ cultures. Efficiency of allocation To. it is rather small. Diagnosis is based on virologic (a submicroscopy of the infected cultures, and also the cytopathic effect revealed in the corresponding monolayer cellular culture) and serological (increase in blood serum of sick quantity of antibodies to complement-linked antigen K. the person, a strain 229 E, and antibodies to hemagglutinin of a strain of OS 43) methods (see. Virologic researches ).

In most cases To. cause diseases of people during the period from January to March. Spread of a disease preferential intra family.

Vaccinal prevention and chemotherapy of koronavirusny diseases are not developed.

See also Viruses , Respiratory viral diseases .



Bibliography: Zakstelskaya L. Ya. and Shcheboldov A. V. Coronaviruses of the person and animals, M., 1977, bibliogr.; Me I n t about s h K. Coronaviruses, Curr. Top. Microbiol. Immunol., v. 63, p. 86, 1974; Tyrrell D. A. a. o. Coronaviruses, Nature (Lond.), v. 220, p. 650, 1968; T at of r e 1 1 D. A. a. o. Coronaviridae, In-tervirology, y. 5, p. 76, 1975; Viral infections of humans, ed. by A. S. Evans, N. Y., 1976.


I. G. Balangding.

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