Influenza B virus Victoria lineage hemagglutinin (HA (when context is needed: HA of B/Victoria lineage))

Influenza B virus Victoria lineage hemagglutinin is a surface glycoprotein found on the envelope of Influenza B viruses belonging to the Victoria lineage. Hemagglutinin (HA) is responsible for attaching the virus to sialic acid-containing receptors on host cell surfaces, initiating infection via receptor-mediated endocytosis[7]. Once inside the endosome, HA undergoes a conformational change to mediate fusion between the viral envelope and the endosomal membrane, thereby releasing the viral genome into the host cytosol[1]. The Victoria and Yamagata lineages of Influenza B are antigenically distinct, and immunity is generally not cross-protective. HA is the primary target for neutralizing antibodies and is thus the main antigen included in seasonal influenza vaccines[5]. Mutations and deletions within HA, especially in defined antigenic sites (such as the 120, 150, and 160 loops and 190 helix), allow the virus to escape immune recognition—a process known as antigenic drift[2][3]. This necessitates continuous surveillance and periodic updates to vaccine composition. Experimentally, single-domain antibodies and monoclonal antibodies have been developed to target conserved regions of Influenza B HA, illustrating its clinical relevance as a therapeutic and preventive target[6]. HA from Victoria lineage viruses differs functionally and antigenically from the Yamagata lineage, and both lineages have caused epidemics in humans; however, only Victoria lineage viruses have continued to circulate widely in recent years[4][5].

Other names

Hemagglutinin of Influenza B Victoria lineageHA (of B/Victoria lineage)Influenza B Victoria HAB/Victoria/2/1987-like hemagglutinin

Neutralizing antibodies: block HA binding to sialic acid-containing host cell receptors, inhibiting virus entry. Vaccine: induces production of anti-HA antibodies, conferring protective immunity by preventing virus attachment and entry.