Influenza Hemagglutinin Antigen H1N1 Subtype A Virus Protein (HA)

Influenza hemagglutinin (HA) is a surface glycoprotein and the principal antigen of the influenza A virus, including the H1N1 subtype. It plays a central role in viral infectivity and immune recognition. HA is responsible for binding to host cell receptors and mediating fusion between the viral envelope and host cell membrane, enabling viral entry. It is a homotrimeric protein, with each monomer comprising a globular head domain (receptor binding) and a stem domain (membrane fusion). The mature HA protein results from cleavage of an inactive precursor (HA0) into two subunits: HA1 (head) and HA2 (stem), which remain linked by a disulfide bond. HA is a major target of neutralizing antibodies, and its rapid evolution through mutation leads to frequent emergence of new strains capable of evading pre-existing immunity. This necessitates regular updates to seasonal vaccines. Its critical role as both an attachment factor/receptor binder *and* fusion protein makes it a prime target for antiviral drugs, monoclonal antibodies, diagnostics, surveillance programs, and vaccine design efforts.

Other names

HemagglutininH1N1 HemagglutininHA proteinInfluenza HAH1HA1 (subunit)HA2 (subunit)

Binding to sialic acid receptors on host cells, mediating fusion of viral and host cell membranes.