Influenza hemagglutinin H5 (H5 HA) (H5 HA)

Influenza hemagglutinin H5 (H5 HA) is a critical surface glycoprotein found on the envelope of H5-subtype influenza A viruses, such as the highly pathogenic avian influenza (HPAI) H5N1 [UniProt: P03452]. It functions as a class I viral fusion protein, responsible for recognizing and binding to sialic acid receptors on the host cell surface to initiate viral entry via endocytosis [PubMed: 22705105]. Following internalization, a pH-induced conformational change in the HA molecule triggers the fusion of the viral envelope with the endosomal membrane, releasing the viral genome into the cytoplasm [Nature: 457, 1101–1104]. As the primary antigen against which neutralizing antibodies are directed, H5 HA is the focal point for vaccine development and the design of broad-spectrum monoclonal antibodies [WHO: H5N1 Fact Sheet]. The H5 subtype is particularly significant in public health due to its high mortality rate in humans and its potential to evolve into a pandemic strain through reassortment or mutation [CDC: H5N1 Bird Flu]. Therapeutic interventions targeting H5 HA aim to either block the receptor-binding site on the globular head or stabilize the conserved stem region to inhibit the fusion process [Science: 324, 1297-1301].

Other names

H5HA5Hemagglutinin subtype 5H5N1 hemagglutininHemagglutinin [Influenza A virus]

Inhibition of viral attachment to alpha-2,3-linked sialic acid receptors and prevention of the pH-dependent conformational change required for membrane fusion within the host cell endosome [PubMed: 22705105, Science: 324, 1297-1301].