Influenza A virus hemagglutinin (H7N9) (H7 HA)

The Influenza A virus hemagglutinin (H7N9) is a critical surface glycoprotein that facilitates the entry of the H7N9 virus into host cells (UniProt: P0CG37). It functions as a homotrimer, where each monomer consists of two subunits, HA1 and HA2, linked by a disulfide bond (PubMed: 23619126). The HA1 subunit contains the receptor-binding site that recognizes sialic acid on the host cell surface, while the HA2 subunit mediates the fusion of the viral envelope with the endosomal membrane following a pH-induced conformational change (PubMed: 24045094). In the context of H7N9, this protein has evolved to bind more effectively to human-type alpha-2,6-linked sialic acid receptors, increasing its pandemic potential (Nature: 10.1038/nature12379). As a primary target for the host immune system, it is the focus of most influenza vaccines and neutralizing monoclonal antibody therapies (PubMed: 27440010). Drugs targeting this molecule, such as Umifenovir, typically aim to block receptor binding or inhibit the fusion process to prevent viral replication (PubMed: 30107239). Understanding its structural variations is essential for monitoring viral evolution and developing effective countermeasures against severe respiratory infections (WHO, 2023).

Other names

HemagglutininHAH7 hemagglutininH7N9 surface glycoproteinH7N9 HA

Neutralization of viral entry by blocking the binding of the hemagglutinin globular head to host sialic acid receptors or by inhibiting the pH-dependent conformational change required for membrane fusion (PubMed: 27440010, 30107239).