Genetic variability of circulating influenza B victoria viruses in Hainan, 2021−2022

Objective In order to understand the prevalence of influenza B virus, the antigenic, resistance to antiviral medications, and genetic characteristics of influenza B viruses circulating in Hainan province during 2021−2022 were analyzed. Methods The antigenic charactetistics of 33 influenza B Victoria lineage viruses were analyzed with reference ferret anti-sera and were tested for neuraminidase inhibitors using a phenotypic assay. The genome of influenza B Victoria lineage viruses were sequenced using the MiSeq™ platform (Illumina). Multi-sequence alignment analyses were undertaken using MEGA 10.1.8 and DNAStar 7.0.1. A phylogenetic tree was constructed with the neighbor-joining method. Results The result showed the B Victoria lineage viruses were prevalent in Hainan Province during 2021−2022. The hemagglutinin (HA) and neuraminidase (NA) gene sequences from Hainan circulating viruses were grouped in clade 1A.3, reassortant between HA and NA was not identified. The isolated viruses were antigenically closely related to the recommend vaccine strain B/Washington/02/2019 (2020−2022). All 33 viruses were sensitive to Oseltamivir; one viruse had highly reduced sensitivity to Zanamivir with the mutation sites of D197E. Conclusions Overall, the predominant circulating B Victoria lineage viruses in Hainan province during 2021−2022 were matched by current influenza vaccine and have retained susceptibility to neuraminidase inhibitors.