Influenza virus H3 hemagglutinin (H3 HA)

The Influenza virus H3 hemagglutinin is a major surface glycoprotein found on Influenza A viruses, particularly the H3N2 subtype which has circulated in humans since the 1968 pandemic. It functions as a class I viral fusion protein, responsible for binding the virus to sialic acid receptors on the host cell surface and mediating the subsequent fusion of the viral envelope with the endosomal membrane. Because it is the primary target for neutralizing antibodies, H3 HA is the central component of seasonal influenza vaccines. However, the protein undergoes frequent 'antigenic drift,' where mutations in the antibody-binding sites allow the virus to evade prior immunity. Therapeutic strategies targeting H3 HA include the development of universal vaccines and broadly neutralizing monoclonal antibodies that target the more conserved stem region of the molecule. Understanding the structural evolution of H3 HA is critical for monitoring viral spread and improving the efficacy of annual influenza immunizations (Source: NIH, PubMed, UniProt).

Other names

Hemagglutinin subtype 3H3 antigenInfluenza A virus H3HAHA3

Neutralization of viral infectivity by blocking the attachment of the virus to host cell sialic acid receptors or by inhibiting the pH-dependent conformational change required for membrane fusion in the endosome.