Influenza A virus H9 hemagglutinin (HA) (HA)

The Influenza A H9 hemagglutinin (HA) from the A/Hong Kong/1073/99 (H9N2) strain is a primary surface glycoprotein that mediates viral entry into host cells. It acts as a Class I fusion protein, facilitating attachment to host sialic acid receptors and subsequent membrane fusion within the endosome [UniProt: Q9ICB8]. This specific H9 subtype is recognized for its zoonotic potential, having caused human infections and circulating widely in avian populations [PubMed: 11160664]. As a major antigen, HA is the principal target for the host immune response and the primary component of influenza vaccines [PubMed: 22658769]. Drugs such as Umifenovir (Arbidol) target the HA-mediated fusion process, while neutralizing monoclonal antibodies aim to block viral attachment or the conformational changes necessary for entry [PubMed: 30108119]. Understanding the structural and antigenic properties of this HA is vital for pandemic preparedness and the development of broad-spectrum antivirals [CDC: H9N2].

Other names

H9 hemagglutininHemagglutinin H9Surface glycoproteinHA proteinA/Hong Kong/1073/99 HA

The hemagglutinin protein mediates viral entry by binding to host cell surface sialic acid receptors and subsequently facilitating the fusion of the viral envelope with the endosomal membrane through a pH-dependent conformational change [PubMed: 30108119].