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 rel atively low (1987-8) or high (1990-1) influenza B activity were charac terized antigenically using a microneutralization assay. These isolate s were antigenically similar to contemporary reference strains from ei ther of two separate lineages represented by B/Victoria/2/87 and B/Yam agata/16/88. The evolutionary relationships of the variable portion of the haemagglutinin (HA1) genes of these viruses were determined by co mparison with influenza B HA1 sequences previously obtained. The Isola te B/USSR/2/87, collected during the 1987-8 influenza season, was foun d 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. S equence analysis of the isolates from the 1990-1 influenza season demo nstrated co-circulation of viruses from both the B/Victoria/2/87 and B /Yamagata/16/88 lineages in Russia, confirming the antigenic analysis.