Influenza B virus Yamagata lineage hemagglutinin (HA)

The Influenza B virus Yamagata lineage hemagglutinin (HA) is a trimeric transmembrane glycoprotein on the viral surface that mediates host cell attachment by binding sialic acid-containing receptors and facilitates membrane fusion during viral entry. It consists of HA1 (receptor-binding and antigenic domains) and HA2 (fusion peptide and stem), with key antigenic sites including the 120 loop, 150 loop, 160 loop, and 190 helix that drive antigenic drift through amino acid substitutions, such as at positions 148, 149, 150, and 203, distinguishing Yamagata from Victoria lineage. These changes enable immune escape, contributing to seasonal epidemics despite slower evolution than influenza A. HA antigenic properties are assessed via hemagglutination inhibition (HI) and virus neutralization assays, revealing Yamagata-specific neutralizing epitopes in the 150 loop. As a primary target for influenza B vaccines, antibodies targeting the HA receptor-binding site (RBS) provide cross-lineage protection, though no direct small-molecule inhibitors exist. Yamagata HA's structural features, including unique disulfide bridges and glycosylation sites like HA1-145, aid immune evasion. The protein's role in disease centers on enabling influenza B infections, which cause significant human morbidity in seasonal outbreaks, with Yamagata lineage cocirculating until recent decline. Therapeutic strategies focus on eliciting HA-neutralizing antibodies via vaccination, with challenges from indels and substitutions promoting reassortment and drift.

Other names

B/Yamagata hemagglutininInfluenza B Yamagata HAB/Yamagata/16/1988 hemagglutinin

Antibody neutralization of receptor-binding site (RBS); Inhibition of hemagglutination; Prevention of viral entry via HA blockade