Hemagglutinin of H3N2 variant influenza A virus (HA)

Hemagglutinin (HA) is the primary surface glycoprotein of the H3N2v influenza A virus, a variant strain typically transmitted from swine to humans [1, 20]. It functions as a homotrimeric class I fusion protein, mediating both the initial attachment of the virus to host cell sialic acid receptors and the subsequent fusion of the viral envelope with the endosomal membrane [2, 7, 9]. HA is the principal antigen targeted by the host immune system and is the primary component of seasonal and variant-specific influenza vaccines [8, 10, 15]. However, its high rate of mutation, known as antigenic drift, frequently necessitates vaccine updates and poses a significant challenge for achieving long-term, broad-spectrum immunity [1, 16, 22]. Therapeutic strategies targeting HA include neutralizing antibodies that block the receptor-binding site or the conserved stalk region, as well as small-molecule inhibitors like umifenovir that prevent membrane fusion [3, 6, 23].

Other names

HaemagglutininH3 hemagglutininViral surface glycoproteinH3N2v HAH3N2 variant hemagglutinin

Hemagglutinin inhibitors function by blocking the binding of the HA1 subunit to host cell sialic acid receptors, preventing the pH-induced conformational change in the HA2 subunit required for membrane fusion, or interfering with the proteolytic activation and glycosylation of the HA0 precursor [2, 4, 7, 17, 23].