Influenza A virus hemagglutinin and neuraminidase (HA and NA)

Influenza A virus hemagglutinin and neuraminidase are the canonical surface antigens embedded in the lipid envelope of Influenza A virions. Hemagglutinin mediates virus binding to host cell sialic acid receptors and triggers membrane fusion necessary for viral entry[2][3][4]. Neuraminidase cleaves sialic acid residues to release new virus particles, facilitate virus movement through mucus, and prevent self-aggregation of virions[2][5][1]. The balance and spatial organization of HA and NA on the viral surface are essential for efficient infection, immune evasion, and transmissibility[1][2]. These glycoproteins are the major targets for neutralizing antibodies and are the basis for classification of influenza strains (e.g., H1N1, H3N2)[2][4]. Both HA and NA undergo frequent mutation (antigenic drift) and segment reassortment (antigenic shift), underlying the periodic emergence of new epidemic and pandemic strains for which population immunity is lacking[2][4]. Therapies and vaccines most commonly target these surface antigens[5][3], and their structural and functional variability present ongoing challenges for influenza management and public health interventions.

Other names

Influenza A surface glycoproteinsIAV surface antigensInfluenza A virus envelope proteins

**Neuraminidase inhibitors:** Block NA enzyme activity to prevent release of progeny virus from infected cells, reducing viral spread. - **M2 inhibitors:** Block ion channel function (not a surface antigen, but drug mentions relate to surface proteins). - **Monoclonal antibodies:** Neutralize HA function by inhibiting receptor binding or fusion, or NA to block enzymatic activity.