Antigenic and genetic characteristics of influenza B virus Victoria lineage in Quzhou, Zhejiang, 2021−2022

  Objective  To understand the antigenicity and genetic characteristics of influenza B virus Victoria lineage isolated in Quzhou, Zhejiang, from 2021 to 2022, and to provide evidence for the prevention and control of influenza.

  Methods  A total of 14 influenza B virus Victoria lineage strains isolated in Quzhou during 2021−2022 were selected for whole genome sequencing and bioinformatics software was used to analyze the evolutionary variation characteristics. The antigenicity of the strains was analyzed by hemagglutination inhibition test.

  Results  In the 14 strains of influenza B virus Victoria lineage, 10 were similar strains of the contemporaneous vaccine strain B/Washington/02/2019, and 4 were less reactive strains. The phylogenetic analysis showed that the isolated strains of influenza B virus Victoria lineage evolved into clades of V1A.3a.2 from V1A.3a.1. The strains were far from B/Washington/02/201, but close to B/Austria/1359417/2021 in the following year (2022−2023), and clustered in clade V1A.3a.2. The hemagglutinin (HA) amino acid sites of the isolated strains changed compared with the vaccine strain B/Washington/02/2019, involving 14 amino acid mutations. These variations covered 3 antigenic epitopes and 1 glycosylation site (197NET). There were multiple mutation sites of the amino acids of neuraminidase (NA), but no mutation were found in the drug resistant sites of NA.

  Conclusion  The results revealed the obvious evolution trend of influenza B virus Victoria lineage isolated in Quzhou during 2021−2022, and the matching degree between the B/Victoria strains isolated and contemporaneous vaccine strain B/Washington/02/2019 was reduced. Therefore, surveillance for influenza B virus Victoria lineage should be strengthened to provide evidence for the recommendation of influenza B virus vaccine strains.