Hemagglutinin (Influenza A virus A(H1N1)pdm09) (HA)

Hemagglutinin (HA) is the primary surface glycoprotein of the A(H1N1)pdm09 influenza virus, which emerged in 2009 as a novel swine-origin strain (Wikipedia, 2024; TandfOnline, 2014). It plays a dual role in viral entry: the HA1 subunit mediates attachment by binding to alpha-2,6-linked sialic acid receptors on host respiratory epithelial cells, while the HA2 subunit facilitates the fusion of the viral envelope with the endosomal membrane under acidic conditions (SinoBiological, 2024; NIH, 2021). As the immunodominant antigen on the virion surface, HA is the principal target for neutralizing antibodies and the primary component of both seasonal and pandemic influenza vaccines (CDC, 2024; NIH, 2017). Therapeutic interventions targeting HA include monoclonal antibodies like MEDI8852 that target the conserved stalk region and small-molecule fusion inhibitors such as umifenovir (Arbidol) (NIH, 2016; ASM, 2024). The rapid evolution of HA through antigenic drift, characterized by point mutations such as D222G, poses a significant challenge to long-term vaccine efficacy and necessitates continuous global surveillance (NIH, 2014; ThermoFisher, 2024).

Other names

H1HA1HA2pdm09 HASwine-origin influenza hemagglutininH1N1pdm09 hemagglutininInfluenza A/California/04/2009 HA

Neutralization of viral attachment by blocking the receptor-binding site and inhibition of membrane fusion by preventing low-pH-induced conformational changes in the stalk region.