Influenza A Hemagglutinin Protein H3N2 Subtype (HA H3N2)

The hemagglutinin (HA) protein is a surface glycoprotein of the influenza A virus, essential for viral entry into host cells. The H3N2 subtype refers to one of the major human-infecting forms, first emerging in 1968 and responsible for significant seasonal influenza outbreaks. HA binds sialic acid-containing receptors on respiratory epithelial cells, determining species specificity and initiating infection. After endocytosis into host cells, acidic pH triggers conformational changes in HA that expose its fusion peptide, allowing viral and cellular membranes to merge—releasing viral RNA into the cytoplasm for replication. H3N2 has circulated in humans since 1968 and undergoes frequent antigenic drift, mutations that allow escape from immune recognition while maintaining function. Major antigenic sites overlap with or surround the receptor-binding site on HA1, leading to continual changes requiring regular updates to seasonal vaccines targeting this protein.

Other names

H3N2 HemagglutininHAHemagglutininH3 Hemagglutinin

Neutralization of HA through antibody binding; Inhibition of receptor binding; Prevention of membrane fusion