Hemagglutinin and neuraminidase from influenza A virus (HA and NA from influenza A virus)

Hemagglutinin and neuraminidase are the two principal surface glycoproteins of the influenza A virus, responsible for the virus's ability to infect host cells and to spread within a host. Hemagglutinin (HA) mediates viral attachment to host cell sialic acid receptors and triggers fusion of viral and endosomal membranes, enabling viral entry. Neuraminidase (NA) cleaves sialic acid residues from host cell surfaces and viral glycoproteins, facilitating release of newly formed virions and preventing virion aggregation. Both proteins are major antigens recognized by the immune system, form the basis of current seasonal influenza vaccines, and serve as drug targets, especially NA (for which inhibitors are widely used antivirals). Immune responses against these proteins are critical for protection against influenza infection. Their high variability, due to antigenic drift and shift, allows influenza viruses to evade immunity, causing annual epidemics and occasional pandemics.

Other names

Hemagglutinin (HA)Neuraminidase (NA)Influenza surface glycoproteinsInfluenza A envelope glycoproteinsViral HA and NA

Competitive inhibition of neuraminidase, blocking virion release from infected cells (NA inhibitors); Induction of neutralizing antibodies (HA and NA in vaccines); Blocking viral attachment and membrane fusion (HA-targeted antibodies, vaccine-induced or monoclonal)