Influenza B virus hemagglutinin (Victoria lineage) (HA)

Influenza B virus hemagglutinin (HA) from the Victoria lineage is a trimeric viral envelope glycoprotein responsible for binding sialic acid receptors on host cells to facilitate attachment and mediating membrane fusion via low-pH-induced conformational changes in its HA1 (receptor-binding and vestigial esterase subdomains) and HA2 (fusion peptide and coiled-coil) subunits. It features conserved structural elements like disulfide bridges, glycosylation sites (e.g., HA1-145 on 150 loop), and ionizable residues for pH sensitivity, with major antigenic sites (120 loop, 150 loop, 160 loop, 190 helix) forming a continuous surface prone to substitutions for immune evasion. Crystal structures (e.g., B/Hong Kong/8/73 at 2.8 Å) reveal differences from influenza A HA, such as fusion peptide positioning and unique disulfides, while Victoria-lineage viruses show key substitutions near the RBS (e.g., 150KN, 203TK) defining antigenic separation from Yamagata lineage.

Other names

B/Victoria hemagglutininInfluenza B Victoria HAB/Hong Kong/8/73 hemagglutinin (related strain example)B/Victoria/2/1987 hemagglutinin

Neutralizing antibodies bind receptor-binding site (RBS) or antigenic sites to block attachment or fusion