Influenza B virus hemagglutinin (HA) glycoprotein (Victoria lineage) (HA)

The Influenza B/Victoria-lineage hemagglutinin (HA) glycoprotein is a major surface antigen of the Influenza B virus, which belongs to the Orthomyxoviridae family (Wikipedia, 2024). It is a class I viral fusion protein that plays a dual role in viral entry: the HA1 subunit binds to sialic acid receptors on the host cell surface to facilitate attachment, while the HA2 subunit mediates the fusion of the viral envelope with the endosomal membrane under low-pH conditions (UniProt, 2024; NIH, 2021). This protein is the primary target for neutralizing antibodies induced by infection or vaccination, making it central to the design of quadrivalent influenza vaccines (Britannica, 2024; MDPI, 2020). The Victoria lineage is characterized by frequent antigenic drift in the globular head domain, which can lead to immune escape and necessitates regular updates to vaccine components (NIH, 2023). The Victoria lineage diverged from the Yamagata lineage in the 1970s and has since co-circulated, though Victoria-lineage strains have recently become the predominant Influenza B variant globally (NIH, 2024). Structural studies have identified key antigenic sites in the 160-loop and 190-helix of the HA head that are prone to mutations, facilitating the emergence of drift variants (NIH, 2025). Therapeutic interventions include vaccines that incorporate lineage-specific HA and experimental treatments such as broadly neutralizing monoclonal antibodies (e.g., CR9114) and small-molecule inhibitors like umifenovir that target the conserved stalk region or block receptor binding (NIH, 2021; Exploration Pub, 2020).

Other names

HemagglutininHAB/Victoria HAInfluenza B HAB/Victoria/2/87-like hemagglutininHA1HA2

Neutralization of viral attachment by blocking the receptor-binding site and inhibition of membrane fusion by preventing conformational changes in the HA stalk.