Influenza A virus hemagglutinin protein (H5)

The hemagglutinin (HA) protein is a major surface glycoprotein of the influenza A virus, responsible for both binding to host cell receptors and mediating membrane fusion during viral entry. The H5 subtype of HA is notably associated with highly pathogenic avian influenza viruses, such as H5N1, which can infect both birds and humans. HA binds to sialic acid-containing receptors on host cell surfaces via its globular head domain, mainly through HA1. After endocytosis and exposure to acidic pH in endosomes, it undergoes conformational changes that expose the fusion peptide in HA2, enabling membrane fusion and release of viral ribonucleoproteins into the cytoplasm. It is a major target for neutralizing antibodies; and is also targeted by macrocyclic peptides.

Other names

H5 hemagglutininHA (H5 subtype)H5N1 hemagglutinin

Neutralizing antibodies bind to the receptor-binding site, stem region, or other vulnerable sites preventing viral entry. Macrocyclic peptides bind to conserved regions within the stem domain, inhibiting membrane fusion.