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The influence of bronchoalveolar washing fluid (BAWF), as well as BAWF cells, obtained from mice infected with influenza virus, on the formation of exogenic spleen colony-forming units (CFUs) of lethally irradiated syngeneic recipients was studied. BAWF and BAWF cells of intact syngeneic mice stimulated the growth of CFUs. BAWF of mice infected with nonpathogenic strain A/PR/8/34 lost its capacity for stimulating the growth of colonies, and BAWF cells greatly suppressed colony formation in the spleen of recipients. The participation of interferon, colony-stimulating factor and the virus itself in the process of the modulation of colony formation is discussed.

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A model is proposed for the study of molecular mechanisms of a low pH-induced interaction of fusion proteins of enveloped viruses and cell membranes. The model consists of large monolamellar liposomes containing ionophore nigericin in their membranes and ectodomains of fusion protein in their inner space. The process of interaction of the protein with the lipid bilayer is triggered by acidification of the liposomal constituents to the pH of fusion with the help of nigericin by adding citric acid to the outer medium. To visualize the protein structural reorganization, the tritium planigraphy was used. Comparison of the values of specific labelling of the proteins and distribution of radioactivity in individual amino acids in control (at neutral pH) and experimental liposome samples (at the pH of fusion) permits to realise the character of protein-membrane interaction. We have obtained the first results in the study of interaction of the bromelain-released soluble ectodomain of the HAXX molecule (BHA)--with the lipid membrane. The observed increase in the protein specific activity and selective increase in the specific activity of hydrophobic amino acids Ile, Phe and Tyr in experimental liposome samples as compared with the controls did not contradict to the conventional concept, that a hydrophobic N-terminus of HA2 subunit of hemagglutinin is responsible for its interaction with lipid membranes.

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The replication of pathogenic influenza virus A/PR/8/34 in the lungs and the synthesis of virus-neutralizing (VN) and haemagglutination-inhibition (HI) antibodies has been studied in mice with endogenous hypocorticism induced by a bilateral adrenalectomy. The adrenalectomized mice appeared to be more susceptible to influenza infection as compared to the mock-operated ones. This was evident from earlier deaths and higher death rate in mice inoculated with 50 EID50, 1000 EID50, and 6000 EID50 of the virus, respectively. A tendency towards decrease of specific antibody titres and the resistance to reinfection with influenza virus A/PR/8/34 was also observed.

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Somatic hybridization produced a set of 6 mouse hybridomas producing monoclonal antibodies of G isotype to influenza A/Krasnodar/101/59 (H2N2) virus. MCA were characterized by solid phase enzyme-immunoassay, hemagglutination-inhibition test, and indirect immunofluorescence technique. According to the results of radioimmunoprecipitation, all 6 hybridomas produced MCA to hemagglutinin of influenza A/Krasnodar/101/59 (H2N2) virus.

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The clinico-experimental studies of mixed influenza-staphylococcal infection constantly point to the development of the aggravation of the infectious process due to the synergic action of the bacterial and viral infective agents. But, as shown by the authors of the present work, in those cases when the experimental infection with the virus was preceded by staphylococcal infection by 72 hours no synergism was observed. In cases of infection with adaptogenic virus the mortality rate of mice resulting from meningococcal infection was twice as low. The possible explanation of this fact is discussed.

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Expression of the inactivation effect of the stem colony-forming marrow cells of male mice CBA, C57B1/6, (CBA.C57B1/6)F1 and (C57B1/6.CBA)F1 by syngeneic lymphocytes of lymphatic nodes of females in conditions of transplantation of cell mixtures into lethally irradiated recipients was studied. The maximum inactivation effect of stem cells (86.3%) is determined in mice F1 with differences of H-Y antigen, the minimum effect (2.4%)--in mice CBA, an intermediate effect (54%) being registered in mice C57B1/6. Sensibility of target cells to the inactivation influence of lymphocytes distinguished by weak transplantation H-Y antigen depended on the maternal effect and direction of reaction. The inactivation effect was maximal in the combination CBA----C57B1/6 and C57B1/6----C57B1/6, as compared with the combination CBA----CBA and C57B1/6----CBA. Possible mechanisms by which the killer action of syngeneic lymphocytes on the antigen H-Y of target cells is developed differently, are under discussion.

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The studies demonstrated that antibody synthesis under conditions of the investigated fatal influenza infection differs in certain parameters from that in non-fatal infection. The mouse-pathogenic A/PR8/34 strain of influenza virus actively induced synthesis of antibodies detectable both by HI and NT. The less pathogenic A/Krasnodar/101/59 strain induced synthesis of antibodies detectable by NT sufficiently well but was a poor inducer of antibodies inhibiting virus hemagglutination of chick erythrocytes. Antibodies detectable by HI and NT appear to represent different molecules of immunoglobulins which differ in their immunochemical properties. These antibodies could be separated by means of affinity chromatography on an immunosorbent. The results of the above studies confirm that the protective and virus-neutralizing activity of an immune preparation in passive immunization is determined by the qualitative and quantitative composition of antibodies in a given preparation. The ratio of virus-induced antibodies may possibly determine the severity of the course and outcome of primary influenza infection.

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The influence of different routes of immunization on the protective effect of liposome-incorporated influenza A/PR/8/34 virus surface antigens was studied. Influenza virus surface antigens, neuraminidase and hemagglutinin, incorporated into liposomes, were shown to have a significant protective effect upon intraperitoneal and intranasal administration against a lethal dose of influenza virus as compared with immunization using a free antigen solution against the same infection. The protective effect is poor in intravenous immunization with influenza virus antigen-containing liposomes. It is concluded that combining of influenza virus antigens with liposomes may be used for preparation of new influenza vaccines.

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The sensitivity of mice of CBA (H-2k haplotype), C57BL/6 (H-2b haplotype) strains and their hybrids M1 and F2 to the pathogenic influenza A/PR8/34 (H0N1) and nonpathogenic A/Krasnodar/101/59 (H2N2) virus strains was studied. The lethality, virus replication in the lungs, and the thymic index were determined. An increase in the resistance to the pathogenic influenza virus was found in male C57BL/6 and male F1 (CBA X C57BL/6) hybrids in the summer period as compared with winter. Replication of the pathogenic virus in the lungs of mice, in contrast to the nonpathogenic one, was accompanied by marked atrophy of the thymus. The study suggests the existence of a certain association between the resistance to influenza infection and phenotypic changes in the host connected with the weight of the thymus and the presence of mature T-lymphocytes.

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The data are presented dealing with the construction of algorithm of numerical classification of RNA- and DNA-containing viruses of vertebrates. The possibility of using of a limited number of parameters with certain coefficients was demonstrated. Suitable parameters for this purpose were elucidated and coefficients (weights) for them determined.

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The possibility of using cluster analysis for allocation of viruses into groups having a taxonomic rank below the family was studied. As a result, a modified variant of cluster analysis is proposed which may be used for investigation of similarities and differences among viruses within individual families and formation of groups corresponding to those of a lower taxonomic rank than the family. The use of this modified variant of cluster analysis allowed the authors to distinguish groups in the majority of the families studied corresponding to ICTV genera. The data have been obtained suggesting the necessity of changing the taxonomic rank of some virus groups. The above studies have shown the possibility of developing numerical classification of viruses at the subfamily and genus levels, in other words, a single hierarchical numerical classification of viruses.

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A methodologic approach to the comparative study of viruses producing objective data not given by experimental biological studies has been developed. The comparative study is based on the quantitation of similarities of viruses based on integral differences of viruses in all the parameters under study. The results obtained permit us to consider all the viruses as a single system possessing a certain structure which reflects the degrees of similarity and differences between individual virus groups. The analysis of the immediate surroundings of each group determined 5 chains consisting of virus groups situated in the order of their retreat from the group corresponding to the Picornaviridae family. The revealed structure of the virus system allows modelling of evolutionary relations between individual virus groups to be made.

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A comparative study of chromatography and centrifugation as applied to purification of 2 influenza virus strains with different antigenic structure (H0N1 and H2N2) and of some biological properties of the resulting preparations was carried out. Certain strain-specific differences manifested in their chromatographic behaviour and in the degree of purification of virions from the allantoic fluid proteins were found. Some quantitative differences observed in the capacity of the resulting virus preparations to infect chick embryos and primary and continuous cells are insignificant and cannot be used for judgement of advantages of one or the other of the methods used for influenza virus purification.

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The cytotoxic activity of lymphocytes of C3HA and C3H (H-2X) mice immunized with the mouse-pathogenic A/PR8/34 (H0N1) and nonpathogenic A/Krasnodar/101/59 (H2N2) strains of influenza virus and with isolated membrane protein was studied. The sensitized lymphocytes were shown to be capable of recognizing and lysing the cells infected with homologous or heterologous virus.

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Some chemical properties of neuraminidase of the mouse-pathogenic strain A/PR/8/34 (H0N1) and the mouse-apathogenic strain A/Krasnodar/101/59 (H2N2) were studied. Neuraminidase of the pathogenic strain was shown to have a lower specific activity, lower resistance and lower sensitivity to the inhibiting effect of CI ions than neuraminidase of the nonpathogenic strain.

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Three methodical approaches were used for reduction of the number of markers necessary for division of viruses into groups corresponding to certain families. Division of the markers into groups characterizing various properties of virions and their components as well as certain stages of virus reproduction in sensitive systems allowed some groups of markers to be excluded without losing the informative value of the marker set. The use of correlationships between markers helped to replace 64 initial parameters with 26 factors. The employment of the method of major components demonstrated the possibility of further reduction of the size of space in which virus clustering is done.

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The cytotoxic activity of spleen lymphocytes of mice C3H and C3HA lines immunized with whole virions and membrane protein of influenza A/PR8/34 virus strain was studied. The cytotoxic activity of lymphocytes of mice immunized with whole virions was found to be higher for cells of primary mouse kidney cultures inoculated with the homologous virus than for cells of a continuous L929 line. The cytotoxic lymphocytes formed in response to the inoculation with membrane protein have a higher lysing activity for target cells of the continuous L929 line.

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