Influenza A virus hemagglutinin H2 subtype (H2 HA)

Influenza A virus hemagglutinin H2 subtype (H2 HA) is a major surface glycoprotein of the H2N2 influenza virus, which was responsible for the 1957 Asian Flu pandemic (CDC, 2019). It functions as a Class I viral fusion protein, existing as a homotrimer where each monomer consists of HA1 and HA2 subunits (UniProt P03451). The HA1 subunit is responsible for recognizing and binding to sialic acid receptors on the host cell surface, while the HA2 subunit mediates the fusion of the viral envelope with the endosomal membrane following endocytosis (PubMed: 24336214). As the primary antigen for neutralizing antibodies, H2 HA is a critical target for vaccine design and therapeutic monoclonal antibodies, such as MEDI8852 and CR6261, which often target the conserved stem region (PubMed: 26823431). Small molecule inhibitors like Umifenovir (Arbidol) also target the HA-mediated fusion process to block viral entry (DrugBank DB13609). Given that H2N2 has not circulated in humans since 1968, there is significant concern regarding the lack of population immunity and the potential for a new pandemic if the subtype re-emerges from avian reservoirs (PubMed: 23637406).

Other names

H2 hemagglutininHemagglutinin H2HA2Influenza A H2 HAH2N2 hemagglutinin

Inhibition of viral entry by blocking sialic acid receptor binding or preventing the pH-dependent conformational change required for membrane fusion (PubMed: 24336214).