Hemagglutinin protein of Influenza A H1N1 subtype (HA)

Hemagglutinin is a trimeric glycoprotein found on the surface of Influenza A virus, including the H1N1 subtype[1][3][5]. Each monomer is synthesized as an HA0 precursor, cleaved by host proteases into HA1 and HA2 subunits[3][7]. The HA1 subunit forms the globular head containing the receptor-binding site, while HA2 forms the stem and contains the fusion peptide responsible for merging viral and host membranes[1][3][5][7]. HA binds sialic acid–containing receptors on host cells, mediating viral entry, and its structure determines both host range and antigenicity[1][5][6][7]. As the primary target of neutralizing antibodies, it is a major component of influenza vaccines and central to immune surveillance strategies[6][7]. Antigenic variation in HA underlies seasonal influenza epidemics and the emergence of pandemic strains such as H1N1[1][5][7]. The high immunogenicity and surface exposure of HA make it a principal target for preventive and therapeutic interventions, but also a locus of antigenic drift and shift conferring immune evasion[6][7].

Other names

Influenza hemagglutininInfluenza A virus hemagglutininHA glycoproteinH1 hemagglutinin

Neutralizing antibodies inhibit HA’s ability to bind sialic acid–containing receptors (block viral entry) Antibodies targeting the stem region inhibit membrane fusion post-entry Antigenic drift/shift in HA allows viral immune evasion