Influenza A virus H5N1 hemagglutinin protein (HA)

Hemagglutinin (HA) is the primary surface glycoprotein of the Influenza A H5N1 virus, playing a critical role in the initial stages of infection. It functions as a homotrimeric protein that mediates both viral attachment to host cell sialic acid receptors and the subsequent fusion of the viral envelope with the endosomal membrane [1, 13]. The H5 subtype is a major determinant of the virus's high pathogenicity and host range, typically binding to α2,3-linked sialic acids prevalent in avian species, though mutations can enable binding to human-type α2,6-linked receptors [7, 14]. As the principal target for neutralizing antibodies, HA is the central component of H5N1 vaccines and a focus for developing novel entry inhibitors [4, 15]. Therapeutic strategies targeting HA include monoclonal antibodies that bind to the conserved stem region to prevent fusion and small molecules that interfere with its conformational changes [15, 21]. However, the rapid evolution of HA through antigenic drift poses significant challenges for long-term vaccine efficacy and pandemic preparedness [16, 17].

Other names

H5Hemagglutinin H5H5 HAH5N1 HAViral hemagglutininH5 surface glycoprotein

Hemagglutinin-targeted drugs primarily act as entry inhibitors by either blocking the receptor-binding site on the globular head to prevent viral attachment or binding to the conserved stem region to inhibit the pH-induced conformational changes required for membrane fusion [13, 15, 21].