A newly developed real-time PCR assay for discriminating influenza B virus Yamagata and Victoria lineages

Currently, two distinct lineages of influenza B virus (IBV), B/Victoria and B/Yamagata lineage, have been co-circulating in human beings. Assessment of the prevalent lineage is key for the recommendation of the seasonal influenza vaccine composition and the evaluation of its efficacy. In this study, a multiplex qRT-PCR assay for the discrimination of the IBV lineages was designed based on the genetic differences of the hemagglutinin genes between B/Yamagata and B/Victoria lineages. The assay was highly specific and able to discriminate the lineages of IBV without any non-specific reaction against other influenza A viruses. The detection limit of the assay was determined to be 10 genome-equivalent copies and 2.8 × 10^-2 50% tissue culture infectious doses (TCID₅₀ ) of live IBV per reaction. Moreover, our assay was able to discriminate the lineages of IBVs in clinical samples with 100% accuracy, when compared with pyrosequencing. Our results indicate that this assay may represent an update of the existing qRT-PCR assays and will be of great use for the rapid and accurate diagnosis and surveillance of the circulating IBVs.