Hemagglutinin protein, H7 subtype (H7)

The Hemagglutinin protein, H7 subtype (H7 HA) is a homotrimeric glycoprotein on the surface of influenza A viruses, functioning as both an attachment factor and class I fusion protein. It binds sialic acid-containing receptors on host cells, preferentially α2-3-linked sialosides in avian species, facilitating viral entry, while human-adapted variants may shift toward α2-6-linked receptors. Synthesized as inactive HA0 precursor, it is cleaved into HA1 (globular head with receptor binding site) and HA2 (stalk with fusion peptide) by host proteases, enabling low-pH-induced conformational changes in endosomes for membrane fusion and viral genome release. In H7 subtypes, unique features like a 140-loop insertion near the receptor binding site and potential glycosylation at Asn123 modulate binding affinity and host tropism, contributing to pathogenicity in outbreaks such as the 2003 H7N7 event. H7 HA is phylogenetically grouped in clade 2 of influenza HA subtypes and serves as a key antigenic target for neutralizing antibodies, though no approved small-molecule drugs directly target it; vaccine and monoclonal antibody strategies focus on its conserved epitopes. Its role in avian influenza zoonoses underscores risks for human pandemics, with structural variations influencing replication efficiency and tissue tropism.

Other names

HAH7 HAInfluenza A virus hemagglutinin H7