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Conditions for pseudosuspension culturing of continuous cells of the kidneys of dogs (MDCK), green marmosets (CV-1), and swine (SPEV) on two types of microcarriers (Cytogel-3 and cytolar-2) under semiproduction conditions (50 liter bioreactor) were developed on a model of reassortants of influenza viruses A and B. To standardize the conditions, native sera were replaced by growth-stimulating proteins isolated from the sera of various animals (cattle, northern deer, swine). A better adhesive capacity and more active cell proliferation on porous microcarrier cytogel-3 were observed. The highest proliferative activity of cells was observed when porcine growth-stimulating proteins were used. Influenza A virus reassortant (H3N1) was actively reproduced in MDCK cells. The reproduction of influenza B virus reassortant was similarly higher in MDCK cells, in comparison with SPEV cells; at the same time, no differences in hemagglutinin titers in the two cell cultures were observed. The pseudosuspension method of cell culturing is recommended for the preparation of influenza antigens.

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The primary structure of hemagglutinin of the members of three main antigenic groups of current influenza A (H3N2) viruses was determined. A phenomenon of "antigenic mimicry" was found to be due to the accumulation of reversions in hemagglutinin structure at late stages of antigenic drift.

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The study included 230 strains of influenza A (H3N2) virus isolated in the epidemic of 1985. A high degree of heterogeneity of the virus population was established with polyclonal sera, monoclonal antibodies and the method of kRNA-bRNA hybridization for the determination of the genome composition. Among the strains of one epidemic (1985) three antigenically heterogenous groups of strains were detected similar with reference A/Philippines/2/82, A/Ken/1/84, and A/Mississippi/1/85 strains. It was shown that in the process of antigenic drift in some strains there occurred a reversion of the antigenic determinants similar to those of previously circulating epidemic A/Texas/1/77 strain.

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Influenza A viruses (H3N2) isolated in the USSR, 1986, from children were antigenically similar to the prototype A/Hong Kong/1/68 strain. Alongside with the similarity with the latter virus, the new isolates had a number of distinctive features both in the antigenic specificity of hemagglutinin and in the structure of the polymerase complex proteins. All the foregoing allows to exclude laboratory contamination and suggests the possibility of circulation of such viruses among children.

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In 1985, a new epidemic variant of influenza virus, A/Berlin/6/85 (H3N2) was isolated which differed antigenically from the reference A/Philippines/2/82 virus. The results of the study of population immunity in adults and children of the USSR and GDR to these virus variants confirm the data on the continuing drift of virus A (H3N2).

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The antigenic structure of hemagglutinin of influenza A virus (H3N2) strains isolated in 1985 was studied using a series of monoclonal antibody to A/Dunedin/4/73/A (H3N2) and A/Bangkok/1/79/A (H3N2), and biological and physico-chemical properties of these strains were compared with those of influenza A (H3N2) virus of 1983 and reference A (H3N2) of 1979-1984 (the rate of adsorption on chick erythrocytes and eluting activity, thermostability of hemagglutinin and neuraminidase, sensitivity to nonionic detergents, sensitivity to remantadine, analysis of virion polypeptide composition). A high degree of heterogeneity of the 1985 strain population of influenza A (H3N2) virus was revealed both in the antigenic structure of hemagglutinin and in all the biological and physico-chemical parameters tested. It was suggested that the A/Caen/1/84 strain originated not from A/Philippines/2/82 but directly from A/Texas/1/77.

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Between 1980 and 1985, Czechoslovakia had experienced 4 and the USSR 3 major influenza outbreaks. Of the 3 epidemic outbreaks in the USSR, 2 were associated with influenza B virus (in the 1980/81 and 1983/84 seasons) and 1 with influenza A virus of the H3N2 subtype. In the USSR, influenza A (H1N1) virus never predominated as a cause of epidemic during the 5 years period. In Czechoslovakia, 2 epidemics (in the 1980/81 and 1983/84 seasons) were due to influenza A (H1N1) virus. The epidemic in the 1981/82 season had two waves of unequal heights and a mixed type B and subtype A (H3N2) etiology; a two-wave epidemic associated with isolates of influenza A (H1N1) and influenza B viruses was also recorded in the 1983/84 season. The influenza A (H3N2) epidemic in 1983 was of explosive character. All influenza viruses circulating in the two countries between 1980 and 1985 were of the same antigenic profile, but were isolated from the epidemics that occurred in different influenza seasons. The virological surveillance revealed strains of virus closely related to drift variants detected from outbreaks in 1977-1979 and the new variants A/Chile 1/83, A/Philippines 2/82, A/Caen 1/84 and B/USSR 100/83.

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Influenza A and B viruses isolated from animals and man were studied by solid phase radioimmunoassay (SP RIA) using monoclonal antibodies to the A/Dunedin/4/73 strain nucleoprotein (NP). Only influenza A viruses isolated before 1980 interacted with the monoclonal antibody set used, while strains isolated between 1980 and 1983 failed to do so. It was shown that RIA employing monoclonal antibodies was useful for rapid identification of influenza virus NP in the allantoic fluid containing fresh influenza A virus isolates.

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In the interepidemic period of 1982-1983, acute respiratory viral infections and pneumonias in infants in Alma-Ata were in 40.2% of cases etiologically associated with influenza infection. In the studied period in Alma-Ata and during an epidemic outbreak of influenza in Kzyl-Orda (March, 1983), two influenza A virus subtypes, H1N1 and H3N2, were in circulation. In a number of cases these subtypes were isolated from the same infants.

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Internal proteins of influenza B/USSR/14/80 virus retaining their antigenic and immunogenic activities were obtained by electrophoresis in 1% agarose. Antisera to eluted NP and M polypeptides were prepared. Study of influenza B viruses isolated in 1940-1984, performed by solid-phase radioimmunoassay, revealed no differences in the antigenic properties of nucleoprotein and matrix protein, except in the B/Yamagata/73 virus.

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Parallel studies of influenza A (H1N1) strains by the micro-HI method using monoclonal antibodies, antivirion sera obtained by immunization of rats, and by the immunoadsorption of rats, and by the immunoadsorption test showed monoclonal antibodies to detect the antigenic drift most definitely. Among 156 strains isolated in 1977-1982 in various parts of the USSR and abroad, 6 antigenic drift variants were detected differing in the content and combination of epitopes recognized by different monoclonal antibodies to the A/USSR/90/77 strain. Three of them have first been found. The quantitative decrease in an epitope activity was established to precede its disappearance and may be used as a prognostic sign. Among 5 epitopes tested, most labile were those recognized by monoclones Nos. 264, 110, and 18. They began to disappear since 1978-1979. The epitopes recognized by monoclones Nos. 70 and 22 were most conservative and were still found in the strains isolated in 1982.

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The principal possibility of using beta-propiolactone-inactivated and lyophilized antigens of influenza A and B viruses and of mouse immune ascitic fluids to them for the determination of the antigenic specificity of neuraminidase has first been established. A simpler and easier method requiring no expensive reagents: inhibition of influenza virus release from erythrocytes was tested. This method is as specific as the labour-consuming and difficult test of neuraminidase activity inhibition, and allows a rapid and accurate identification of the type of neuraminidase of influenza viruses of various origins to be made.

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Investigation of influenza viruses isolated from man and animals and having hemagglutinin of the H3 subtype according to the new nomenclature (H3, Heq2 and Hav7 according to the old nomenclature) by serological methods (including the use of monoclonal antibody) and oligopeptide mapping showed that many animal isolates reflected an antigenic drift of the Hong Kong virus series which has been going on since 1968 until now. At the same time a number of isolates represent precursors of viruses of the Hong Kong series circulating among the human population. It is suggested that this is not the first time that viruses of the Hong Kong series have been introduced into the human population.

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Comparison of some avian influenza virus strains possessing haemagglutinin Havl revealed the greatest differences in strains A/FPV/Weybridge and A/FPV/Rostock/34. These strains differed in the degree of homology of eight genome fragments, electrophoretic mobility of the majority of proteins, size of plaques and rct42 marker and displayed significant differences in antigenic specificity of haemagglutinin. Strains A/FPV/Weybridge and A/FPV/Dobson proved to be more close in the degree of genome homology but differed in three genes, electrophoretic mobility of some proteins, size of plaques, rct42 marker and antigenic specificity of haemagglutinin. The data obtained indicate that avian influenza virus strains of the Havl subtype may differ from each other in the degree of gene homology and some other properties including antigenic specificity of haemagglutinin like influenza viruses with other haemagglutinin subtypes.

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A comparative study of influenza A virus NP proteins was carried out using peptide mapping. Thirty-five strains of all main serotypes of human and animal viruses were tested. The greatest diversity was found in NP proteins of human influenza viruses belonging to different serotypes, while within serotypes the variability is less pronounced. Four main groups of NP proteins were distinguished and designated NP0, NP1, NP2, and NP3. The NP0 group includes proteins of viruses of HON1 serotype, NP proteins of all avian viruses with the exception of A/shearwater/Australia/1/71 (Hav6Nav5), NP proteins of A/horse/Prague/56 (Heq1Neq1), A/swine/Iowa/1/30 (Hsw1N1), and A/whale/Pacific/76 (HONav2). The NP1 group comprises NP proteins of viruses of HIN1 serotype (with the exception of A/California/78), A/Singapore/57 (H2N2) and NP protein of A/New Jersey/76 (Hsw1N2) virus. The NP2 group includes NP proteins of H3N2 virus serotype and NP protein of A/California/78 (H1N1) virus. NP proteins of A/horse/Miami/63 (Heq2Neq2) and A/shearwater/Australia/1/71 viruses comprise NP3 group.

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