Influenza A virus hemagglutinin subtype H7 (HA) (H7 HA)

Influenza A virus hemagglutinin subtype H7 (H7 HA) is a class I fusion glycoprotein responsible for viral attachment and membrane fusion during influenza A infection. The protein functions through two sequential steps: first, the HA1 globular domain recognizes and binds sialic acid receptors on target cell surfaces, facilitating viral attachment; second, following endocytosis and exposure to acidic pH, the HA2 domain undergoes dramatic conformational reorganization that extrudes a fusion peptide, effectively "grappling" the endosomal membrane and pulling it into contact with the viral membrane to enable fusion and viral genome release. H7 HA subtypes, particularly highly pathogenic variants like H7N7, demonstrate preferential binding to avian-type α2-3-linked sialic acid receptors, though certain mutations and glycosylation patterns influence human receptor recognition and pathogenicity. The protein's structural features, including polybasic cleavage sites and specific glycosylation motifs, directly correlate with viral replication efficiency and tissue distribution. As a major surface antigen and the primary viral protein mediating host cell entry, H7 HA represents both a critical target for antiviral interventions and the primary driver of host adaptation and pandemic potential in influenza A viruses.

Other names

H7 hemagglutininInfluenza A H7 HAHA7

Receptor recognition: HA1 domain binds sialic acid on target cell surfaces; Membrane fusion: Following endocytosis, acidic pH (5.0-5.5) triggers conformational change, releasing fusion peptide from HA2 domain; Viral entry: Fusion peptide inserts into endosomal membrane and retracts, pulling viral and cellular membranes together for fusion