Rapid detection of new B/Victoria-lineage haemagglutinin variants of influenza B viruses by pyrosequencing

During 2016/2017, several antigenically and genetically distinct variant viruses of the influenza B/Victoria/2/87-lineage (B/Vic) viruses, which have either deletions or mutations in the haemagglutinin (HA) emerged and co-circulated with other influenza B viruses from both the B/Vic and B/Yamagata/16/88-lineages (B/Yam). In this study we developed a pyrosequencing assay that can detect and differentiate multiple influenza B virus variants currently in circulation. The assay targets a region of HA sequence that is unique for each of the B/Yam, B/Vic and B/Vic variant viruses. Our results demonstrated that it is a rapid, robust, high-throughput assay, highly sensitive and specific in differentiating among the B/Yam, B/Vic and B/Vic variant viruses, giving it an advantage over an existing rRT-PCR method. It works well for influenza virus isolates as well as original clinical respiratory specimens, and can therefore be used to provide important information for surveillance by closely monitoring the spread of these B/Vic variants.