Hemagglutinin of Influenza A virus (H1N1) 2009 pandemic strain (HA)

Hemagglutinin (HA) is the major surface glycoprotein of the 2009 pandemic H1N1 influenza A virus (H1N1pdm09) and is essential for viral infectivity (UniProt P03452). It functions as a trimeric class I fusion protein that mediates two critical steps of the viral life cycle: binding to host cell sialic acid receptors and facilitating the fusion of the viral envelope with the endosomal membrane (PubMed: 20110523). The 2009 pandemic HA specifically evolved to prefer alpha-2,6-linked sialic acids, which are abundant in the human upper respiratory tract, enabling efficient transmission among humans (Nature, 2009). As the primary target for neutralizing antibodies, HA is the key component of both inactivated and live-attenuated influenza vaccines (CDC, 2023). Therapeutic strategies targeting HA include small molecule inhibitors like umifenovir, which prevents the conformational changes required for membrane fusion, and broadly neutralizing monoclonal antibodies that target the conserved stem region of the protein to provide protection across multiple influenza strains (DrugBank DB13609; PubMed: 30104377).

Other names

H1N1pdm09 HemagglutininHA proteinH1 HemagglutininInfluenza A virus (A/California/04/2009(H1N1)) hemagglutininHemagglutinin surface glycoprotein

Inhibition of the pH-dependent conformational change of the hemagglutinin protein, which prevents the fusion of the viral envelope with the host cell endosomal membrane, or steric blockade of the receptor-binding site to prevent viral attachment (PubMed: 27433872, 27284199).