Influenza A virus H5N1 haemagglutinin and neuraminidase (H5N1 HA/NA)

Influenza A virus H5N1 haemagglutinin (HA) and neuraminidase (NA) are the two primary surface glycoproteins of the highly pathogenic avian influenza (HPAI) H5N1 subtype (Wikipedia). HA is a trimeric protein that mediates viral entry by binding to host cell sialic acid receptors—specifically alpha-2,3-linked sialic acids in avian hosts—and facilitating membrane fusion (NIH). NA is a tetrameric enzyme that cleaves these sialic acid residues to prevent the aggregation of progeny virions and enable their release from the host cell surface (ResearchGate). Together, these proteins determine the virus's host range, tissue tropism, and pathogenicity (NIH). They are the main targets for neutralizing antibodies and the primary components of influenza vaccines (PubMed). Therapeutic interventions primarily target NA using inhibitors like oseltamivir and zanamivir, which block viral shedding (NIH). HA is also a target for emerging fusion inhibitors and monoclonal antibodies designed to prevent infection (Exploration Pub). Due to the high mutation rate of the virus, monitoring antigenic drift and the emergence of drug-resistant mutations, such as the H274Y substitution in NA, is critical for pandemic preparedness (NIH). H5N1 is of particular concern due to its high mortality rate in humans and its potential to cause a global pandemic (WHO).

Other names

H5N1 surface glycoproteinsH5N1 envelope proteinsHemagglutinin-NeuraminidaseHA-NA

Neuraminidase inhibitors block the enzymatic activity of NA, preventing the cleavage of sialic acid residues and the subsequent release of progeny virions from infected cells. Hemagglutinin-targeted agents, including neutralizing antibodies and fusion inhibitors, block viral attachment to host sialic acid receptors or prevent the pH-dependent conformational changes required for viral-host membrane fusion.