Laboratory characterization of influenza A viruses (H3N2)--pathogens of Leningrad 1983 epidemic.

: Seventy strains of influenza A virus (H3N2) isolated in Leningrad during the influenza epidemic in January--March 1983 were studied. The virus isolates appeared to be markedly heterogeneous with respect to antigenic characteristics of surface glycoproteins, biological properties (haemagglutinating and neuraminidase activities, sensitivity to gamma-inhibitors, etc.) as well as genome structure. The identity of the virus isolates with the reference influenza A virus was as follows: 10% were similar to A/Texas/1/77 virus, 30% to A/Bangkok/1/79 virus, and 20% to A/Philippines/2/82 virus. A large part of the isolated viruses (27 of 70) were characterized by a certain (mainly unilateral) relatedness with the virus A/Victoria/35/72. The isolates were extremely heterogeneous with respect to genomic characteristics as determined by cRNA-vRNA hybridization test and differed from the corresponding reference strains by the homology of genes 1-6.