Hemagglutinin (H1N1) (HA) (HA)

Hemagglutinin (HA) is a major surface glycoprotein of the H1N1 influenza A virus, functioning as a homotrimeric Class I fusion protein (UniProt: C3W5X2). It is responsible for binding the virus to host cell surface receptors containing terminal sialic acid residues, which triggers receptor-mediated endocytosis (PubMed: 21149602). Following endocytosis, the acidic environment of the endosome induces a massive conformational change in HA, leading to the fusion of the viral and endosomal membranes and the release of the viral genome into the cytoplasm (PubMed: 19833966). As the primary antigen recognized by the host immune system, HA is the central component of most influenza vaccines, which aim to elicit neutralizing antibodies that block viral entry (StatPearls: Influenza). However, HA is subject to frequent antigenic drift, necessitating annual vaccine updates to maintain efficacy against evolving H1N1 strains (PubMed: 30104475). Beyond vaccines, HA is a target for antiviral development, including fusion inhibitors like Umifenovir and broadly neutralizing monoclonal antibodies that target the conserved stem region of the protein (PubMed: 27229144).

Other names

H1 HAInfluenza A virus hemagglutininSurface glycoproteinHA proteinHemagglutinin protein

Inhibition of viral attachment to host sialic acid receptors and prevention of pH-dependent membrane fusion within the endosome (PubMed: 30812914, PubMed: 27229144).