Hemagglutinin protein (H5 subtype) and Neuraminidase protein (N1 subtype) from Influenza A virus (HA (H5N1), NA (H5N1))

Hemagglutinin (HA) and neuraminidase (NA) are the principal antigenic glycoproteins on the surface of the influenza A H5N1 virus. HA (H5 subtype) mediates viral attachment to host cell sialic acid receptors and membrane fusion, allowing for entry and infection. HA is a trimer composed of HA1 and HA2 subunits, and its receptor-binding specificity can shift through single mutations, influencing host range. NA (N1 subtype) is a tetrameric sialidase that cleaves sialic acid residues during viral release, enabling efficient spread of progeny virions and maintaining balance with HA activity. Both are key targets for antiviral drugs (especially NA inhibitors) and form the basis of licensed and investigational influenza vaccines, with neutralizing antibodies against these antigens correlating with protection. Hemagglutinin and neuraminidase exhibit substantial antigenic variability, contributing to the ongoing risk of pandemic emergence from H5N1 viruses.

Other names

H5 hemagglutininN1 neuraminidaseInfluenza A H5N1 surface antigensinfluenza virus spike glycoproteinsH5N1 HAH5N1 NA

Neuraminidase inhibitors: competitive inhibition of sialidase active site, blocking virion release. Monoclonal antibodies: neutralization by blocking conformational changes or fusion, not directly inhibiting receptor binding for some anti-HA antibodies. Vaccines: induction of neutralizing antibodies against HA and/or NA epitopes.