Influenza A virus hemagglutinin (H3N2 variant) (HA)

The Influenza A H3N2 variant hemagglutinin (HA) glycoprotein is a critical surface protein of the H3N2v virus, a swine-origin influenza virus that occasionally infects humans (CDC, 2023). HA functions as a lectin that mediates the binding of the virus to sialic acid receptors on the surface of host respiratory epithelial cells, facilitating viral entry (UniProt, 2024). Following endocytosis, HA undergoes a dramatic pH-induced conformational change that triggers the fusion of the viral envelope with the endosomal membrane, releasing the viral genome into the cytoplasm (PubMed, 2013). As the primary target of the host's neutralizing antibody response, HA is the central component of most influenza vaccines (NIH, 2022). However, the protein's high rate of mutation, known as antigenic drift, allows the virus to escape existing immunity, necessitating frequent vaccine updates (Nature, 2018). Therapeutic strategies targeting HA include monoclonal antibodies that block the receptor-binding site or the conserved stem region, as well as small-molecule fusion inhibitors like umifenovir (PubChem, 2024). Monitoring the evolution of this glycoprotein is essential for pandemic preparedness, as H3N2v strains possess the potential for sustained human-to-human transmission (WHO, 2023).

Other names

HemagglutininHAH3 hemagglutininH3N2v HASurface glycoprotein HA

Inhibition of viral attachment to host cell sialic acid receptors or prevention of the pH-dependent conformational change required for membrane fusion.