Avian influenza virus hemagglutinin and neuraminidase (HA/NA)

Avian influenza hemagglutinin (HA) and neuraminidase (NA) are the primary surface glycoproteins of avian influenza A viruses, such as H5N1 and H7N9. HA functions as a lectin that mediates viral binding to host cell sialic acid receptors and facilitates membrane fusion for viral entry (Skehel & Wiley, 2000, Annual Review of Biochemistry). NA is a glycoside hydrolase enzyme that cleaves terminal sialic acid residues, which is essential for the release of progeny virions from infected cells and preventing viral aggregation (Gamblin & Skehel, 2010, Journal of Biological Chemistry). These proteins are the principal targets for the host immune response; vaccines aim to induce neutralizing antibodies against HA to prevent infection, while antiviral drugs like oseltamivir target the enzymatic site of NA to limit viral replication (Gubareva et al., 2000, The Lancet). Because avian influenza viruses pose a significant zoonotic threat and exhibit high rates of mutation, these antigens are central to global surveillance and pandemic preparedness (WHO, 2024, Influenza Fact Sheet). Understanding the structural evolution of HA and NA is critical for the development of universal vaccines and next-generation antivirals.

Other names

Influenza surface glycoproteinsHemagglutinin-neuraminidaseHANASialidaseH5N1 antigensH7N9 antigens

Neuraminidase inhibitors prevent the enzymatic cleavage of sialic acid residues, thereby trapping progeny virions on the host cell surface and preventing spread; Hemagglutinin-targeting vaccines induce neutralizing antibodies that sterically hinder viral attachment to host receptors.