Hemagglutinin of H1N1v influenza virus (HA)

Hemagglutinin (HA) is the primary surface glycoprotein of the H1N1v influenza virus, specifically the 2009 pandemic strain (A/H1N1pdm09), and is essential for viral entry into host respiratory epithelial cells (UniProt: C3W5X2). It exists as a homotrimer on the viral envelope, where it mediates binding to terminal alpha-2,6-linked sialic acid residues on host cell surface receptors, triggering receptor-mediated endocytosis. Following internalization, the acidic environment of the endosome induces a massive conformational change in HA, exposing a hydrophobic fusion peptide that facilitates the merging of viral and endosomal membranes (PubMed: 21148485). As the major antigen against which neutralizing antibodies are directed, HA is the central component of seasonal and pandemic influenza vaccines. Therapeutic strategies targeting HA include small-molecule fusion inhibitors like Umifenovir and various investigational monoclonal antibodies, such as VIS410 and MEDI8852, which target the conserved stem region to provide broad protection (PubMed: 26863441). However, the high rate of antigenic drift in the HA head domain necessitates frequent vaccine updates and poses a significant challenge for long-term therapeutic efficacy (CDC: 2009 H1N1 Pandemic).

Other names

H1 hemagglutininHA1/HA2Hemagglutinin surface glycoproteinH1N1pdm09 HAHemagglutinin (HA) protein

Inhibition of viral attachment to host sialic acid receptors and prevention of pH-dependent membrane fusion within the endosome.