Influenza A hemagglutinin glycoprotein (HA)

Influenza A hemagglutinin glycoprotein (HA) is the principal surface glycoprotein of influenza A virus, existing as a trimeric structure composed of identical monomers, each split into two disulfide-linked subunits (HA1 and HA2) following proteolytic activation[1][2][3][7][9]. HA mediates two key steps in viral infection: binding to sialic acid-containing receptors on host cells via the HA1 head domain, which is crucial for host specificity and cellular entry, and the acid-triggered fusion of the viral envelope with the endosomal membrane via the HA2 stem domain[1][2][3][7]. HA is highly variable, with 18 known subtypes (H1–H18, grouped into Group 1 and Group 2), and is the main antigenic determinant shaping immune response and vaccine development[7][9]. It is a central target for neutralizing antibodies and vaccine-induced immunity, as well as for experimental antiviral drugs chiefly aiming to block fusion or attachment functions[6][7]. Due to its role in viral entry and antigenic variation (including antigenic drift and shift), HA is a pivotal factor in influenza pandemic potential and vaccine update requirements[7][9].

Other names

HemagglutininInfluenza A HAInfluenza A surface glycoprotein HAInfluenza A virus hemagglutinin

Inhibition of HA-mediated membrane fusion; Neutralization via antibody binding (blocking receptor attachment or conformational changes); Allosteric inhibition of structural rearrangement