Influenza A virus Hemagglutinin (H5 subtype) (H5 HA)

Influenza A virus Hemagglutinin (H5 subtype) is a major surface glycoprotein of the influenza A virus, playing a pivotal role in viral entry and pathogenesis [8, 9]. It exists as a homotrimeric class I fusion protein that mediates the attachment of the virus to host cell sialic acid receptors and the subsequent fusion of the viral and endosomal membranes [8, 16]. The H5 subtype is particularly significant due to its association with highly pathogenic avian influenza (HPAI), which can cause severe respiratory disease and high mortality in poultry and humans [4, 10]. As the primary target for the host immune response, H5 HA is the central component of vaccines and a key focus for the development of antiviral therapies, including fusion inhibitors and broadly neutralizing antibodies [1, 5, 6]. These drugs and vaccines aim to prevent infection by either blocking the receptor-binding site or stabilizing the protein's prefusion conformation to inhibit the structural rearrangements necessary for membrane fusion [2, 3, 5]. The protein's ability to undergo rapid antigenic drift and shift poses a continuous challenge for vaccine efficacy and pandemic preparedness [13, 15]. Furthermore, mutations in the H5 HA can alter its receptor specificity, potentially facilitating transmission from birds to humans [9, 14]. Understanding the structural and functional properties of H5 HA is therefore essential for monitoring emerging strains and designing effective countermeasures [12, 18].

Other names

H5H5 HAHemagglutinin H5HA0HA1HA2H5N1 Hemagglutinin

Drugs and antibodies targeting H5 HA primarily act through fusion inhibition by stabilizing the prefusion conformation, viral neutralization by blocking the receptor-binding site, or preventing the low-pH-induced conformational changes required for membrane fusion [2, 3, 5, 6].