Influenza A virus H3N2 Hemagglutinin and Neuraminidase (HA/NA (H3N2))

Hemagglutinin (HA) and Neuraminidase (NA) are the two major surface glycoproteins of the Influenza A virus H3N2 subtype and serve as the primary targets for the host immune system. HA is responsible for binding to sialic acid receptors on host respiratory epithelial cells and mediating the fusion of the viral envelope with the endosomal membrane. NA is an exo-enzyme that cleaves terminal sialic acid residues from glycoproteins, a process essential for the release of newly formed viral particles from infected cells and for preventing viral aggregation. In the context of therapeutics, HA is the principal component of seasonal influenza vaccines, which aim to elicit neutralizing antibodies that block viral entry. NA is the primary target for small-molecule antiviral drugs known as neuraminidase inhibitors, which limit the spread of the infection within the host. Because H3N2 viruses undergo rapid antigenic drift, the specific molecular structure of these antigens is monitored globally to update vaccine compositions annually.

Other names

H3N2 surface glycoproteinsInfluenza A H3N2 antigensHemagglutinin (HA)Neuraminidase (NA)Sialidase

Vaccines present HA and NA antigens to the host immune system to stimulate the production of neutralizing antibodies and T-cell responses. Neuraminidase inhibitors (e.g., Oseltamivir) competitively bind to the active site of the NA enzyme to prevent the cleavage of sialic acid, thereby trapping progeny virions on the host cell surface and preventing further viral spread.