Antigenic and genetic analyses of influenza type B viruses isolated in Russia, 1987-91.

Four influenza type B viruses isolated in Russia during periods of relatively low (1987-8) or high (1990-1) influenza B activity were characterized antigenically using a microneutralization assay. These isolates were antigenically similar to contemporary reference strains from either of two separate lineages represented by B/Victoria/2/87 and B/Yamagata/16/88. The evolutionary relationships of the variable portion of the haemagglutinin (HA1) genes of these viruses were determined by comparison with influenza B HA1 sequences previously obtained. The Isolate B/USSR/2/87, collected during the 1987-8 influenza season, was found to be closely related to viruses on the B/Victoria/2/87 lineage that circulated during the 1988-9 influenza season in the United States. Sequence analysis of the isolates from the 1990-1 influenza season demonstrated cocirculation of viruses from both the B/Victoria/2/87 and B/Yamagata/16/88 lineages in Russia, confirming the antigenic analysis.