Hemagglutinin (Influenza B virus - Yamagata lineage) (HA)

Hemagglutinin (HA) is the primary surface glycoprotein of the influenza B virus, essential for viral infectivity by mediating host cell attachment and membrane fusion. Influenza B viruses are divided into two antigenically distinct lineages, Victoria (Lineage 1) and Yamagata (Lineage 2), which diverged in the 1970s. The HA protein of the Yamagata lineage has historically been a key component of quadrivalent influenza vaccines, designed to elicit neutralizing antibodies that prevent viral entry. However, global surveillance indicates that the Yamagata lineage has not been detected in circulation since March 2020, likely due to COVID-19 mitigation measures, leading to recent regulatory recommendations to remove this component from future vaccines. Therapeutic research continues to focus on HA as a target for broadly neutralizing antibodies and universal vaccine candidates that can provide cross-protection against both lineages by targeting conserved epitopes in the HA stem.

Other names

HAHemagglutinin proteinB/Yamagata/16/88-like hemagglutininInfluenza B lineage 2 HAYamagata lineage hemagglutinin

Induction of neutralizing antibodies that block viral attachment to host sialic acid receptors or inhibit pH-dependent membrane fusion in the endosome.