[ts-Mutations in the genomes of cold-adapted variants of influenza A/Hong Kong/1/68(H3N2) and A/Victoria/35/72(H3N2) viruses]. / ts-Mutatsii v genome kholodadaptirovannykh variantov virusov grippa A/Honkong/1/68(H3N2) i A/Viktoriia/35/72(H3N2).

The phenotype and localization of ts mutations in genomes of the influenza A/Victoria/30-ir (A/Vic/30-ir) and A/Hong Kong/17-ir (A/HK/17-ir) cold-adapted (ca) viruses were studied. Using the recombination analysis in chick embryo fibroblasts (CEF) we determined that influenza A/HK/17-ir ca virus carries ts mutations in three "internal" genes, i.e., PB1, NP and M, and influenza A/Vic/30-ir ca virus carries ones in four genes, i.e., PA, NP, M and NS. We have revealed ts mutations for NA gene in none of these viruses. Prior to the analysis of ts mutations in HA gene of influenza A/HK/17-ir and A/Vic/30-ir ca viruses, three cloning steps were performed in chick embryos (CE) by the method of limiting dilutions at 34 degrees C followed by selection of some strains with the most prominent ts phenotype. The cloned strains with such phenotypes were shown to repeat stable results within the recombination analysis in CE, i.e., none from the cloned strains of A/HK/17-ir ca virus recombined in CE at 40 degrees C with the 46 ts mutant, while recombination of this mutant with the cloned A/Vic/30-ir ca strains led to formation of the ts progeny. Thereafter our data result in conclusion that ts mutations in the PA gene must lead to some insignificant contribution for the expression of general ts phenotype among the ca strains as far as this sign is clearly displayed by both viruses, although only one of them, i.e., A/HK/17-ir carries ts mutation in the HA gene.

[Role of individual genes in expression of phenotypic properties of the cold-adapted strain A/Leningrad/134/47/57 (H2N2)-a donor of attenuation of live influenza vaccine]. / Rol' otdel'nykh genov v proiavlenii fenotipicheskikh svoistv kholodoadaptirovannogo shtamma A/Leningrad/134/47/57 (H2N2)-- donora attenuatsii zhivykh grippoznykh vaktsin.

The influenza A/Leningrad/134/47/57 (H2N2) (A/Len/47) cold-adapted virus expresses the ability to reproduce at 25 degrees C (the ca phenotype) and inability to reproduce at 40 degrees C (the ts phenotype). It was attenuated for mice. Reassortants of this donor virus with the genes coding for the surface glycoproteins from the epidemic viruses, i.e. hemagglutinin (HA) and neuraminidase (NA), have been shown to be attenuated, immunogenic and genetically stable. We made attempts to reveal the influence of individual genes from the A/Len/47 ca virus on the expression of some phenotypic properties. Different "single-gene" reassortants were created and investigated using the influenza A/PR/8/34 (H1N1) virus as another parent with the opposite phenotypic properties, i.e. lack of ca+ and ts+ phenotypes and high virulence for mice. We managed to obtain "single-gene" reassortants with PB1, NA and NS genes at this stage of the work. None of them (probably including the M gene as well) could determine the ca or ts phenotypes, nor could the presence of the NA and NS genes from the strain A/Len/47 influence these properties. However, our findings show that the combined influence (synergism) of the PB1 and NS genes from the ca donors results in the ts phenotype of the reassortants. Significant role of the NS gene for attenuation of influenza viruses in mice has been revealed.

[The evaluation of the degree of attenuation of cold-adapted influenza A virus strains in CBA-strain mouse and Syrian hamster models]. / Otsenka stepeni attenuatsii kholodo-adaptirovannykh shtammov virusa grippa A na modeliakh myshei linii CBA i siriiskikh khomiachkov.

The pattern of the infectious process induced by the epidemic A/Leningrad/134/57 (H2N2) virus and its cold-adapted (CA) variants in CBA mice and Syrian hamsters was studied. The strains under study inoculated into the animals under a mild ether anesthesia differed by virulence, reproductive capacity in the nasopharynx, trachea and lungs, as well as by the isolation rate from extrarespiratory organs of both mice and hamsters. Upon intranasal inoculation of mice without anesthesia, the CA strains were found to be incapable of dissemination into the lower parts of the respiratory tract with distinguished these viruses from the original epidemic strain A/Leningrad/134/57 as well as from the mouse-adapted strain A/PR/8/34 (H1N1) used as control. The experimental results show that both models are suitable for laboratory evaluation of the attenuation degree of human influenza viruses.

[Mutations in the genes coding for hemagglutinin and neuraminidase in cold-adapted variants of the influenza virus A/Leningrad/134/57 (H2N2)]. / Mutatsii v genakh, kodiruiushchikh gemaggliutinin i neiraminidazu, u kholodoadaptirovannykh variantov virusa grippa A/Leningrad/134/157 (H2N2).

An analysis of ts-mutations in the genomes of native and cold-adapted variants of influenza A/Leningrad/134/57 (H2N2) virus based on the use of fowl plague virus ts mutants was carried out. The recombination test was done by the conventional method in chick embryo fibroblast culture (genes PB2, PB1, PA, NP, NA, M and NS) or cell systems permissive for reproduction of human influenza virus (gene HA). The cold-adapted strain A/Len/17 used for preparation of live influenza vaccine (LIV) for adults was shown to have 4 ts mutations: three in "internal" genes (PB2, NP, and M) and one in gene 4 coding for hemagglutinin (HA). The more attenuated cold-adapted donor A/Len/47 for preparation of similar LIV for children acquired three additional ts mutations: two (PB1 and NS) in "internal" genes and one in gene 6 coding for neuraminidase (NA). The accumulation of ts mutations in the genome of cold-adapter strains was found to be accompanied by a decrease in their pneumotropicity for mice as well as their detectability in different organs of these animals.