Influenza A virus H5 hemagglutinin (clade 2.3.4.4b) (H5 HA)

The Influenza A H5 hemagglutinin (HA) is the primary surface glycoprotein of the H5 subtype influenza virus, specifically within the highly pathogenic clade 2.3.4.4b. This protein is essential for viral infectivity, as the HA1 subunit mediates attachment to host cell sialic acid receptors while the HA2 subunit facilitates the fusion of the viral envelope with the host endosomal membrane [1, 3]. The A/Astrakhan/3212/2020 strain is a significant representative of this clade, having been associated with the first documented human infections of H5N8 in 2020 [2]. As the major target for the host immune response, HA is the central antigen used in the development of pandemic preparedness vaccines and therapeutic monoclonal antibodies [1, 4]. Mutations in the HA protein, particularly in the receptor-binding domain, are closely monitored for their potential to increase human-to-human transmissibility. Therapeutic strategies targeting this molecule focus on preventing viral entry, thereby neutralizing the virus before it can initiate the replication cycle [4]. Sources: [1] World Health Organization (WHO). Antigenic and genetic characteristics of zoonotic influenza A viruses and development of candidate vaccine viruses for pandemic preparedness. (2021). [2] Pyankova, O. G., et al. Isolation of influenza A(H5N8) virus from humans, Russia, 2021. Emerging Infectious Diseases (2021). [3] UniProt Consortium. Hemagglutinin [Influenza A virus]. [4] Centers for Disease Control and Prevention (CDC). H5N1 Bird Flu: Current Situation and Pandemic Preparedness.

Other names

HemagglutininHAH5N8 hemagglutininH5N1 hemagglutininSurface glycoproteinA/Astrakhan/3212/2020 HA

Neutralization of viral entry by blocking the HA1 subunit from binding to host sialic acid receptors or by binding the HA2 stalk region to inhibit pH-dependent membrane fusion.