Hemagglutinin antigen of Influenza B virus (HA)

The **Hemagglutinin antigen of Influenza B virus** is a trimeric viral surface glycoprotein that mediates the virus’s entry into host cells. HA binds to sialic acid-containing receptors on the host cell surface, determining viral attachment and host specificity[1][2][4][5][6]. After receptor binding, HA undergoes a pH-triggered conformational change that drives the fusion of the viral envelope with the endosomal membrane, allowing genomic entry[1][2][5][6]. It is the major antigenic determinant of the Influenza B virus, being the principal target of neutralizing antibodies and the primary component evaluated in seasonal influenza vaccines[5][6]. HA structural variability underlies both susceptibility to immune recognition (hence the efficacy of vaccines and antibodies) and the antigenic drift that necessitates frequent vaccine updates[3][5][6]. Because of its essential role in infection and immunogenicity, HA is a leading therapeutic and diagnostic target in influenza research and public health[4][5][6]. **Notes:** - No small-molecule drugs directly target HA in Influenza B infection; anti-HA monoclonal antibodies are an area of research, and vaccines are the main interacting interventions. - "Hemagglutinin" can refer to analogous proteins in other viruses (such as Influenza A), but structure, sequence, and immunogenicity may differ substantially between types[2][3]. - For structural and epitope details, the HA from Influenza B shows about 25% sequence identity with that of Influenza A, though domain organization is conserved[3][2]. - The standard functional assays for anti-HA immunity include the hemagglutination inhibition assay[5]. If more specificity is needed (e.g., strain/subtype context), include the appropriate strain name or subtype.

Other names

Hemagglutinin (Influenza B)Influenza B hemagglutininHA (Influenza B)B/Lee/1940 HAHAb

Neutralizing antibodies bind HA, blocking receptor binding or fusion; Vaccines induce antibodies targeting HA to prevent infection