Hemagglutinin protein, H5 subtype, Influenza A virus (H5)

The Hemagglutinin protein, H5 subtype, of Influenza A virus is a trimeric glycoprotein spike on the viral envelope that mediates host cell attachment by binding to sialic acid-containing receptors, determining host specificity such as avian versus human cells. It undergoes a pH-triggered conformational change in the endosome, exposing a fusion peptide that drives merger of viral and host membranes, enabling genome release into the cell. The H5 subtype, prominent in highly pathogenic avian influenza like H5N1, features a globular head for receptor binding and a conserved stem for fusion, with mutations potentially enhancing mammalian transmission. This protein's variability across 18 HA subtypes drives antigenic drift and shift, complicating vaccine design and necessitating annual updates. As a key viral antigen, H5 hemagglutinin elicits neutralizing antibodies targeting the head to block binding or the stem for broader protection against fusion. Its role in pandemics, such as potential zoonotic jumps from birds to humans, underscores ongoing surveillance needs.

Other names

HAInfluenza A virus hemagglutinin H5H5 hemagglutinin