Hemagglutinin protein of Influenza A H7N9 virus (HA (for hemagglutinin; H7N9 denotes the subtype))

The **hemagglutinin protein of the Influenza A H7N9 virus** is a trimeric surface glycoprotein essential for viral entry into host cells[1][3][4][5]. It mediates the initial attachment of the virus by binding to sialic acid-containing receptors on the surface of host epithelial cells and promotes subsequent fusion of the viral and cell membranes, allowing the viral genome to enter the host cell cytoplasm[1][3][5]. H7N9 hemagglutinin exhibits a preference for avian-type sialic acid linkages but shows limited binding to human-type receptors, although further adaptation may enhance transmissibility in humans[4]. The protein is the predominant target for neutralizing antibodies and is therefore a primary component in influenza vaccine design and surveillance efforts[1][6]. Rapid antigenic drift poses a challenge for immunity and vaccine updates[6]. Hemagglutinin is not the target of currently approved small-molecule antivirals but is the principal target of host neutralizing immune responses and experimental antibody-based therapies[2][3].

Other names

Hemagglutinin (HA)Influenza A H7N9 hemagglutininHA proteinH7 hemagglutininH7N9 HA

Neutralizing antibodies block receptor binding and/or interfere with membrane fusion[2]. Potential inhibitors could block the conformational change required for fusion or interfere with sialic acid binding