Influenza A virus H7 hemagglutinin and N9 neuraminidase (H7N9 antigens)

H7 hemagglutinin (HA) and N9 neuraminidase (NA) are the primary surface glycoproteins of the Influenza A virus H7N9 subtype, which emerged as a significant human pathogen in 2013 (CDC, 2021). HA mediates viral entry by binding to host cell sialic acid receptors and facilitating membrane fusion, while NA is a glycoside hydrolase that enables the release of progeny virions by cleaving these same receptors (Nature, 2013). These proteins are the central targets for the adaptive immune system; vaccines aim to induce neutralizing antibodies against the HA head or stem to block infection, while the NA protein is the target of neuraminidase inhibitors like oseltamivir and zanamivir (PubMed, 2015). H7N9 is noted for its high mortality rate and its ability to cause severe pneumonia and acute respiratory distress syndrome in humans (WHO, 2018). Therapeutic challenges include the rapid evolution of the virus through antigenic drift and the emergence of drug-resistance mutations, such as the R292K substitution in the NA protein (Lancet, 2013).

Other names

H7 HAN9 NAH7N9 surface glycoproteinsHemagglutinin H7Neuraminidase N9Influenza A virus (A/Anhui/1/2013(H7N9)) antigens

Neuraminidase inhibitors block the enzymatic site of N9 to prevent viral shedding from infected cells; vaccines present H7 and N9 antigens to the immune system to elicit protective neutralizing antibody and T-cell responses.