Influenza A Hemagglutinin Protein (HA)

Influenza A hemagglutinin (HA) is a homotrimeric glycoprotein found on the surface of influenza A viruses. It is a type I transmembrane protein and serves as the primary antigenic determinant of the virus, playing essential roles in both viral entry into host cells and immune recognition. HA exists as a trimer, with each monomer composed of two subunits: HA1 and HA2, generated by proteolytic cleavage of an initial precursor polypeptide (HA0). The globular head binds to sialic acid-containing receptors on host cell surfaces and the stem domain anchors the protein to the viral membrane and mediates membrane fusion during viral entry. Antigenic variation within its structure underlies seasonal flu epidemics/pandemics. Stabilization of prefusion forms of HA has become a key strategy for improving vaccine efficacy.

Other names

HemagglutininHA proteinInfluenza hemagglutinin

NAbs block receptor binding or membrane fusion. Vaccines elicit antibody response against HA.