Influenza A virus hemagglutinin (H5 and H7 subtypes) (HA (H5/H7))

Influenza A virus hemagglutinin (HA) is a type I transmembrane glycoprotein and the primary surface antigen of the influenza virus [3, 9]. It plays a dual role in viral infection: the HA1 subunit mediates binding to sialic acid receptors on the host cell surface, while the HA2 subunit facilitates the fusion of the viral envelope with the endosomal membrane following endocytosis [1, 12]. The H5 and H7 subtypes are of particular clinical and global health concern because they can evolve into highly pathogenic avian influenza (HPAI) strains, which are characterized by a polybasic cleavage site that allows for systemic viral spread and high mortality rates in both avian and human hosts [11, 20]. HA is the principal target for neutralizing antibodies and the primary component of seasonal and pandemic vaccines [4, 10]. Therapeutic development focuses on broadly neutralizing monoclonal antibodies and small-molecule entry inhibitors that target conserved regions, such as the HA stalk, to provide protection against diverse and emerging H5 and H7 strains [2, 7].

Other names

HemagglutininHAH5 antigenH7 antigenViral surface glycoproteinH5N1 HAH7N9 HAHemagglutinin-neuraminidase

Inhibition of viral attachment to host cell sialic acid receptors and blockade of the pH-triggered conformational change required for membrane fusion.