Influenza hemagglutinin and neuraminidase antigen (HA and NA)

Influenza hemagglutinin and neuraminidase are the two major surface glycoproteins of the influenza virus. Hemagglutinin (HA) is a trimeric class I fusion protein responsible for binding the virus to sialic acid-containing host cell receptors and mediating membrane fusion needed for viral entry; it is the principal antigen recognized by neutralizing antibodies and the main driver of antigenic drift and shift[1][5][7]. Neuraminidase (NA) is a tetrameric exosialidase enzyme that cleaves terminal sialic acid residues from host receptors, facilitating release of progeny virions and preventing self-aggregation of virus particles; NA is the target of neuraminidase inhibitor antiviral drugs and is important for viral spread[2][3][4][6]. Both proteins are highly variable, with multiple subtypes (H1–H16 for HA, N1–N9 for NA in influenza A), and are critical for viral infectivity, host adaptation, immune recognition, and serve as the main targets for vaccines and therapeutic interventions.

Other names

Hemagglutinin (HA)Neuraminidase (NA)Influenza surface glycoproteinsInfluenza HA/NA

Neuraminidase inhibitors block the enzymatic cleavage of sialic acid, preventing efficient viral release[3][4]. HA-targeted antibodies block receptor binding or fusion, neutralizing the virus[5][7].