Influenza A virus hemagglutinin (H3N2) (HA)

Influenza A virus hemagglutinin (H3N2) is a multifunctional viral surface glycoprotein that plays essential roles in the influenza virus life cycle. It exists as a homotrimer with each monomer consisting of two subunits: HA1, which forms the globular head containing the receptor-binding site, and HA2, which forms the stem region responsible for membrane fusion. The protein is initially synthesized as an inactive precursor (HA0) that requires proteolytic cleavage to become functional. The primary functions of hemagglutinin are binding to sialic acid receptors on host cell surfaces (initiating viral attachment) and mediating fusion between the viral and host cell membranes (enabling viral entry). The receptor-binding site in H3N2 hemagglutinin is composed of structural elements including the 130-loop, 150-loop, 190-helix, and 220-loop, with several highly conserved residues across influenza subtypes[1]. H3N2 is one of the major influenza A subtypes causing seasonal influenza in humans and has been associated with more severe disease, particularly in older adults[2]. The high mutation rate of hemagglutinin leads to antigenic drift, necessitating frequent updates to seasonal influenza vaccines. Due to its critical role in viral infection and as the primary target of neutralizing antibodies, hemagglutinin remains a key focus for antiviral drug development and vaccine design.

Other names

HA proteinHemagglutinin glycoproteinH3 hemagglutinin

Drugs and therapeutic approaches targeting hemagglutinin include: - Neutralizing antibodies (act by blocking receptor binding or preventing conformational changes required for fusion)