Hemagglutinin of influenza A virus subtype H7N9 (HA)

Hemagglutinin (HA) of the influenza A/H7N9 virus is a critical surface glycoprotein that mediates viral entry into host cells. It functions by binding to sialic acid receptors on the host cell surface and subsequently facilitating the fusion of the viral envelope with the endosomal membrane [10, 11]. As the primary antigen of the virus, HA is a major target for the host immune response and the development of vaccines and antiviral therapies [5, 17]. In the context of H7N9, HA has evolved to recognize both avian-type (alpha-2,3-linked) and human-type (alpha-2,6-linked) sialic acid receptors, contributing to its potential for zoonotic transmission and pandemic risk [11, 16]. Therapeutic strategies targeting H7N9 HA include small molecule fusion inhibitors like Umifenovir, broadly neutralizing antibodies that target the conserved stalk region such as CR6261 and FI6, and novel subunit vaccines [1, 4, 6, 15]. Despite its importance as a target, challenges such as rapid antigenic drift and the relatively low immunogenicity of the H7 subtype complicate the development of long-lasting medical countermeasures [15, 21].

Other names

H7 HAH7N9 HAHemagglutinin glycoproteinInfluenza A virus H7N9 hemagglutininSurface glycoprotein HA

Inhibition of viral attachment to host sialic acid receptors, prevention of pH-dependent membrane fusion between the viral envelope and host endosomal membrane, and impairment of hemagglutinin protein transportation to the host cell plasma membrane [1, 2, 4, 7, 9].