Hemagglutinin protein (H5) (H5 HA)

The Hemagglutinin (H5) protein is a critical surface glycoprotein of the H5N1 influenza A virus, serving as the primary mediator of viral entry into host cells. It functions by binding to sialic acid receptors on the host cell surface—specifically alpha-2,3-linked sialic acids in avian species and potentially alpha-2,6-linked receptors in humans—followed by a pH-induced conformational change that triggers membrane fusion in the endosome (UniProt: P03454; CDC, 2023). As the major antigen on the viral surface, H5 is the primary target for neutralizing antibodies and the central component of H5N1 vaccines like Audenz (FDA, 2020). Therapeutic strategies targeting H5 include broadly neutralizing monoclonal antibodies (bnAbs) such as MEDI8852, which target the conserved stem region to prevent the fusion process across multiple influenza subtypes (Nature, 2016). Understanding the structural dynamics of H5 is essential for pandemic preparedness, as mutations in this protein can alter host range and increase the risk of human-to-human transmission (NIH, 2024).

Other names

H5HemagglutininSurface glycoproteinHA glycoproteinInfluenza A virus H5N1 hemagglutinin

Neutralization of viral infectivity by blocking the interaction between the hemagglutinin protein and host cell sialic acid receptors, or by inhibiting the pH-dependent conformational change required for membrane fusion.