Hemagglutinin (H7N9) (HA)

Hemagglutinin (HA) is the primary surface glycoprotein of the H7N9 influenza A virus and serves as a critical mediator of viral entry into host cells (NCBI: Influenza Virus). It functions by binding to sialic acid receptors on the host cell membrane; while H7N9 originally favored avian-type α2,3-linked sialic acids, certain variants have evolved increased affinity for human-type α2,6-linked receptors, facilitating zoonotic transmission (PubMed: 23616126). Following receptor-mediated endocytosis, HA undergoes a pH-induced conformational change within the endosome that triggers the fusion of the viral envelope with the host membrane, releasing the viral genome into the cytoplasm (UniProt: P0CGA0). Due to its essential role in the viral life cycle and its prominent exposure on the virion surface, HA is the central target for neutralizing antibodies and seasonal or pandemic vaccine development. Therapeutic strategies targeting H7 HA include broadly neutralizing monoclonal antibodies that block the receptor-binding site or the conserved stem region to inhibit fusion, as well as small molecule inhibitors like Umifenovir that stabilize the prefusion state (PubMed: 30061512). Monitoring mutations in the HA protein, particularly in the globular head domain, is vital for assessing the pandemic potential and vaccine efficacy against emerging H7N9 strains.

Other names

H7 HemagglutininH7 HAInfluenza A virus H7N9 hemagglutininSurface glycoproteinHA7

Blocking of viral attachment to host sialic acid receptors and inhibition of pH-dependent membrane fusion to prevent viral entry into host cells.