Influenza A virus hemagglutinin (HA) (HA)

Influenza A virus hemagglutinin (HA) is a critical homotrimeric surface glycoprotein that mediates viral entry into host cells by binding to sialic acid receptors and facilitating membrane fusion (UniProt P03435). The A/Astrakhan/3212/2020-like designation refers specifically to the HA of a clade 2.3.4.4b H5N8 avian influenza virus, which was identified in the first reported human cases of H5N8 infection in Russia in 2021 (WHO, 2021). As the primary antigen on the viral surface, HA is the central target for neutralizing antibodies elicited by vaccination and is the basis for the development of candidate vaccine viruses (CVVs) for pandemic preparedness (CDC, 2021). Therapeutic interventions targeting this protein include small-molecule fusion inhibitors like Umifenovir and monoclonal antibodies that prevent viral attachment or entry (PubMed: 30639314). Monitoring mutations in the A/Astrakhan/3212/2020-like HA is essential for assessing zoonotic risk and ensuring the efficacy of seasonal and pre-pandemic vaccines.

Other names

H5 hemagglutininHemagglutinin surface glycoproteinHA1/HA2 complexA/Astrakhan/3212/2020 (H5N8) hemagglutininInfluenza A virus hemagglutinin – A/Astrakhan/3212/2020-like

Inhibition of viral entry by blocking the binding of hemagglutinin to host sialic acid receptors or preventing the pH-dependent conformational change required for membrane fusion (PubMed: 29111234, PubMed: 30639314).