Molecular characterization of the hemagglutinin and neuraminidase genes of influenza B circulating worldwide in the 2001-2002 season

Influenza B viruses have recently undergone significant genetic variations, including antigenic drift and antigenic shift, such as reassortment. We have characterized these changes using the following molecular methods: (i) sequence analysis of the hyper-variable HA1 domain of the hemagglutinin (HA) gene to examine antigenic drift; and (ii) TaqMan-based PCR to determine reassortment of the neuraminidase (NA) gene between two distinct B lineages, B/Victoria/2/87 and B/Yamagata/16/88. Approximately 400 wild-type influenza B isolates collected from Asia, Europe, South America (SAM), and South Africa (SAF) in the 2001-2002 season were analyzed. Based on the HA1 sequences, both influenza B lineages were found. The majority of European specimens belonged to the B/Yamagata/16/88 lineage. In contrast, the majority of non-European isolates belonged to the B/Victoria/2/87 lineage. This lineage was represented by two closely related strains, B/Hong Kong/330/2001 and B/Hong Kong/1351/2002. Of all the isolates examined, reassorted B/Hong Kong/1351/02 was the most dominant influenza B strain circulating worldwide. (C) 2003 Elsevier B.V. All rights reserved.