Influenza A virus subtype H1N1 hemagglutinin (HA)

Influenza A virus subtype H1N1 hemagglutinin (HA) is a critical homotrimeric surface glycoprotein that facilitates viral entry into host cells. It acts as a class I fusion protein, first binding to sialic acid receptors on the respiratory epithelium to initiate endocytosis (UniProt: P03452). Upon exposure to the acidic environment of the endosome, HA undergoes a significant structural rearrangement that triggers the fusion of the viral envelope with the endosomal membrane (PubMed: 22230667). This fusion process is essential for releasing the viral genome into the host cell cytoplasm for replication. As the primary antigen on the viral surface, HA is the central component of seasonal influenza vaccines and the main target for neutralizing antibodies (PubMed: 27466113). Therapeutic interventions targeting HA include small-molecule inhibitors like umifenovir, which prevents the fusion process, and monoclonal antibodies that target either the variable head or conserved stem regions. However, the high rate of mutation in the HA gene leads to antigenic drift, which allows the virus to evade host immunity and necessitates frequent vaccine updates (PubMed: 30104475). Understanding the structural dynamics of H1N1 HA remains a priority for developing "universal" influenza vaccines and more effective antiviral therapies.

Other names

HemagglutininHAH1H1N1 HASurface glycoproteinHemagglutinin HA1/HA2 chain

Inhibition of viral attachment to host sialic acid receptors; prevention of pH-dependent membrane fusion within the endosome; neutralization of viral particles by antibody binding to the globular head or stem regions (PubMed: 29345340, 27466113).