Hemagglutinin (influenza A virus H5N8) (HA)

Hemagglutinin (HA) is the primary surface glycoprotein of the influenza A virus, specifically the H5N8 subtype, which is recognized as a highly pathogenic avian influenza (HPAI). It serves a dual role in the viral life cycle: the HA1 subunit mediates attachment to host cell receptors containing alpha-2,3-linked sialic acids, while the HA2 subunit facilitates the fusion of the viral envelope with the host endosomal membrane following a pH-triggered conformational change. In H5N8, the presence of a multi-basic cleavage site (MBCS) allows the protein to be activated by a wide range of host proteases, leading to systemic infection and high mortality in avian species. As the major antigen on the viral surface, HA is the central target for vaccine development and the primary focus for neutralizing antibodies. Therapeutic strategies targeting HA include monoclonal antibodies that block receptor binding or stabilize the stalk to prevent fusion, as well as small-molecule inhibitors like Umifenovir. Its rapid evolution through antigenic drift and the risk of zoonotic transmission to humans make it a critical target for global pandemic surveillance and antiviral research.

Other names

HaemagglutininH5 HAH5 hemagglutininSurface glycoproteinHA0HA1/HA2

Neutralization of receptor binding and inhibition of pH-dependent membrane fusion