Influenza Hemagglutinin (HA) (HA)

Influenza Hemagglutinin (HA) is a major class I viral fusion glycoprotein found on the surface of influenza viruses, playing a dual role in viral entry and assembly. It is synthesized as a precursor, HA0, which must be proteolytically cleaved by host cell proteases into HA1 and HA2 subunits to trigger its membrane-fusion potential, a process essential for viral infectivity (PubMed: 24009443). HA mediates the initial attachment of the virus to host cells by binding to terminal sialic acid residues on glycoproteins and glycolipids. Following endocytosis, the low pH of the endosome induces a conformational change in HA that facilitates the fusion of the viral and endosomal membranes, releasing the viral genome into the cytoplasm (UniProt: P03437). Beyond entry, HA is transported to the host cell plasma membrane where it concentrates in lipid rafts to facilitate the assembly and budding of progeny virions (PubMed: 21666077). Due to its critical roles and high exposure, HA is the primary target for neutralizing antibodies elicited by vaccination and is the focus of therapeutic strategies including fusion inhibitors like Umifenovir and maturation inhibitors like Nitazoxanide (DrugBank: DB13609, DB00507).

Other names

Hemagglutinin surface glycoproteinHA0HA1HA2Influenza A virus hemagglutininInfluenza B virus hemagglutininViral lectin

Inhibition of the proteolytic cleavage of the HA0 precursor into HA1 and HA2 subunits, stabilization of the prefusion trimer to prevent membrane fusion, and interference with the post-translational folding and intracellular transport of HA to the cell surface.