Hemagglutinin protein (Influenza A virus H7N9 subtype) (HA)

The Hemagglutinin protein (HA) is the primary surface glycoprotein of the Influenza A virus H7N9 subtype, playing a dual role in viral entry by mediating receptor binding and membrane fusion. It facilitates the attachment of the virus to host cell surface receptors containing α2-3 or α2-6 linked sialic acids, which determines the host range and tissue tropism. Following endocytosis, the acidic environment of the endosome triggers an irreversible conformational change in the HA trimer, leading to the fusion of the viral and endosomal membranes and the release of the viral genome into the cytoplasm. As the major antigenic determinant on the viral surface, HA is the central target for seasonal and pandemic vaccines, as well as therapeutic monoclonal antibodies designed to block infection. However, the H7 subtype is noted for its relatively low immunogenicity in humans and its potential for rapid antigenic drift, posing significant challenges for vaccine efficacy and pandemic preparedness.

Other names

H7 HAH7N9 HAH7 hemagglutininHemagglutinin (H7)A/H7N9 surface glycoprotein

Inhibition of viral attachment to host cell sialic acid receptors and prevention of pH-dependent membrane fusion by stabilizing the prefusion conformation or sterically blocking the receptor binding site.