[Features of interepidemic influenza A and B viruses].

The comparison of interepidemic influenza viruses with the pathogens of resultant influenza epidemics has revealed that they belong to the same type (subtype) of influenza virus. A definite correlation has been found between the antigenic specificity of haemagglutinin of epidemic and interepidemic strains. The antigenic structure of the interepidemic viruses and the pathogens of further epidemics of influenza B viruses have been found to be completely identical.

[The determination of the genotype of natural reassortant influenza A viruses according to the core protein genes by the methods of competitive dot hybridization and sequencing].

Simultaneous circulation of different subtypes of influenza A viruses provides conditions for reassortant strains formation. A comparative investigation of genome of 47 influenza A virus strains (H1N1, H2N2, and H3N2) was carried out by competitive dot hybridization technique and sequence analysis of some of cDNA-copies of the virus genes. All the genes of 43 strains encoding nonglycolysed proteins corresponded to the serum subtype of surface glycoproteins.

[Primary structure of the hemagglutinin gene in strains of the influenza virus A/Leningrad/624/86 and A/Leningrad/621/86 serologic subtype H1N1].

A molecular analysis was made of genomes of influenza A (H1N1) virus strains, the causative agents of an epidemic in Leningrad, 1986. The primary structure of hemagglutinin gene of two of these strains, A/Leningrad/624/86 and A/Leningrad/621/86, was established, as well as partial primary structure of PB1 gene of certain current strains of the A (H1N1) subtype. A hypothesis of a "shift" of PB1 gene in 1950-1957 is suggested.

[The primary structure of the hemagglutinin gene of strain A/Riga/9977/86--a drift variant of influenza virus A(H3N2)].

The hemagglutinin gene primary structure of influenza virus A/Riga/9977/86 (H3N2) belonging to the "Coen/84" antigenic subgroup was determined by primer sequencing. A comparative analysis confirmed that the reversions of amino acids in the late stages of the H3 influenza virus subtype antigenic drift became more frequent and the antigenic variants remained in epidemic circulation longer. The possible role of some mutations is discussed.