Hemagglutinin or Neuraminidase viral protein (HA (for hemagglutinin), NA (for neuraminidase))

Hemagglutinin (HA) and neuraminidase (NA) are two distinct envelope glycoproteins on the surface of influenza viruses (types A and B) essential for the viral life cycle and central to both infectivity and immune recognition[6][3][2][7]. Hemagglutinin mediates viral attachment to host cells by binding to sialic acid residues and promotes fusion of the viral envelope with the endosomal membrane, initiating entry[6]. Neuraminidase acts later in infection to cleave sialic acid from host cell surfaces and viral glycoproteins, enabling release of progeny virions and preventing their aggregation[2][3]. Both proteins are highly antigenic and the major serological determinants; their combination (e.g., H1N1, H3N2) defines influenza virus subtypes[2][6]. NA is a key antiviral drug target (oseltamivir, zanamivir), while HA is the main vaccine antigen and subject of neutralizing antibody responses. Mutations in either protein drive antigenic variation, contributing to epidemic and pandemic influenza[2][6][7].

Other names

Influenza hemagglutininHAviral hemagglutininhaemagglutininInfluenza neuraminidaseNAsialidase

Neuraminidase: Drugs are competitive inhibitors of the enzymatic active site, blocking cleavage of sialic acid and thus viral release[2][3][4][7][8]. Hemagglutinin: Targeted by neutralizing antibodies (as vaccines/therapeutics), which block attachment to sialic acid and prevent viral entry[6].