Hemagglutinin (H5N1) (HA)

Hemagglutinin (HA) is the primary surface glycoprotein of the H5N1 influenza virus, responsible for binding to host cell sialic acid receptors and mediating viral entry through membrane fusion (Skehel & Wiley, 2000). In the context of vaccination, HA serves as the principal antigen that the immune system recognizes to produce neutralizing antibodies. The use of the MF59 adjuvant, a squalene-based oil-in-water emulsion, enhances the immune response by promoting the recruitment and activation of antigen-presenting cells at the injection site (O'Hagan et al., 2013). This synergistic approach is designed to overcome the low immunogenicity often associated with avian influenza antigens in humans. By targeting the HA protein, the vaccine-induced immune response prevents the virus from infecting host cells, thereby providing protection against H5N1 infection (FDA, 2020). This mechanism is critical for pandemic preparedness against highly pathogenic avian influenza strains.

Other names

H5 HAHemagglutinin proteinInfluenza A virus H5N1 hemagglutininH5 antigen

The vaccine delivers H5N1 hemagglutinin antigens which are recognized by B-cells and T-cells; the MF59 adjuvant enhances this process by creating an immunocompetent environment at the injection site, recruiting antigen-presenting cells and increasing the breadth and magnitude of the neutralizing antibody response against the HA protein (O'Hagan et al., 2013; FDA, 2020).