H5 influenza virus hemagglutinin (H5 HA) (H5 HA)

H5 influenza virus hemagglutinin (HA) is a critical surface glycoprotein found on H5 subtype Influenza A viruses, including the highly pathogenic H5N1 strain (UniProt P03452). It functions as a class I fusion protein, responsible for recognizing and binding to alpha-2,3-linked sialic acid receptors on the surface of host cells, which triggers viral internalization via endocytosis (PubMed: 16543414). Following internalization, the HA protein undergoes a pH-dependent conformational change that mediates the fusion of the viral and endosomal membranes, releasing the viral genome into the cytoplasm. Because it is the primary target for neutralizing antibodies, H5 HA is the focal point for the development of vaccines, such as Audenz, and monoclonal antibody therapies aimed at preventing zoonotic transmission and potential pandemics (FDA: STN 125692). However, the protein's high rate of antigenic drift and the potential for reassortment necessitate continuous surveillance and periodic updates to therapeutic and preventive interventions (WHO: Influenza Fact Sheet).

Other names

H5 hemagglutininHA5Influenza A virus H5N1 hemagglutininHemagglutinin H5

Neutralization of viral entry by blocking the interaction between the hemagglutinin globular head and host sialic acid receptors, or by stabilizing the hemagglutinin stem to prevent the conformational change required for viral-host membrane fusion (PubMed: 19229033).