Antigenic and genetic characteristics of influenza B virus/Victoria lineage in Shanghai, 2018–2020

  Objective  To analyze the antigenic and genetic characteristics and variation of influenza B virus /Victoria lineage in Shanghai during 2018–2020.

  Methods  Hemagglutinin inhibition test was performed to analyze the antigenicity of 142 strains of influenza B virus/Victoria lineage isolated in Shanghai from April 2018 to March 2020, in which 63 strains were used for hemagglutinin and neuraminidase gene sequencing and analysis.

  Results  V1A.3 was predominant clade in influenza B virus B/Victoria lineage circulating in Shanghai. A few circulating strains belonged to clade V1A.1 and clade V1A without deletion. Only 26.76% of the circulating virus strains were antigenically similar to the B/Colorado/06/2017 vaccine strain. Five amino acids loci had mutation in the HA protein sequence of clade V1A.3 compared with the B/Colorado/06/2017 vaccine strain, involving 4 important epitopes and receptors, such as 120 loop, 150 loop, 160 loop and 190 helix.

  Conclusion  The majority of influenza B virus /Victoria lineage circulating in Shanghai did not match well with the vaccine strain B/Colorado/06/2017 recommended by WHO. It is necessary to further strengthen the surveillance for influenza virus variation to provide reliable data for the screening of influenza vaccine strain.