Influenza virus surface antigen

The principal **surface antigens** of the influenza virus are the **hemagglutinin (HA)** and **neuraminidase (NA)** glycoproteins, which are embedded in the virus’s lipid envelope[2][3][4][5][7]. HA mediates binding to host cell sialic acid receptors and membrane fusion, while NA cleaves sialic acids to enable release of newly formed virions and movement through respiratory mucus. These proteins are the primary targets for host neutralizing antibodies and antiviral drugs (neuraminidase inhibitors). Antigenic drift (small mutations) and antigenic shift (segment reassortment) in the HA and NA genes are responsible for seasonal variation, vaccine escape, and pandemic potential[2][3][7]. Hemagglutinin outnumbers neuraminidase on the viral surface by about five to tenfold, and both antigens are targets for antibody-mediated immunity induced by infection or vaccination, as well as diagnostic and monitoring tools for influenza disease and vaccine effectiveness[2][5][7].

Other names

Influenza surface glycoproteinsInfluenza envelope antigensInfluenza A virus surface proteins

Neuraminidase inhibitors (oseltamivir, zanamivir, peramivir, laninamivir): Block enzymatic cleavage of sialic acid, preventing virus release and spread[5]. Anti-hemagglutinin antibodies: Bind to HA and block receptor binding or fusion, preventing viral entry or fusion with host cell membrane[2][4]. Vaccines generate antibody and T-cell responses against HA and NA[7].