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

Influenza B virus hemagglutinin (HA) Victoria lineage is a primary surface glycoprotein of the influenza B virus and a critical mediator of viral infection. It acts as a Class I viral fusion protein, where the HA1 subunit binds to sialic acid-containing receptors on the host respiratory epithelium to facilitate attachment, and the HA2 subunit undergoes a pH-triggered conformational change to enable the fusion of viral and endosomal membranes. This protein is the principal antigen targeted by seasonal influenza vaccines, which aim to elicit neutralizing antibodies that block viral entry or egress. Since the 1980s, influenza B has diverged into two antigenically distinct lineages, Victoria and Yamagata; the Victoria lineage is currently the dominant circulating lineage following the reported disappearance of Yamagata during the COVID-19 pandemic. Antigenic drift driven by mutations in the globular head domain, particularly in the 120-loop and 150-loop regions, necessitates continuous monitoring and periodic updates to vaccine compositions to ensure protective efficacy.

Other names

B/Victoria hemagglutininVictoria-lineage HAInfluenza B Victoria HAB/Victoria-like hemagglutininHemagglutinin Victoria-lineage

Vaccines containing Victoria-lineage hemagglutinin induce the production of neutralizing antibodies that primarily target the globular head domain to block receptor binding or the stem domain to inhibit membrane fusion, thereby preventing viral entry into host cells and subsequent replication.