Influenza group 1 hemagglutinin (HA (Group 1))

Influenza group 1 hemagglutinin (HA) is a major surface glycoprotein found on Influenza A viruses, encompassing subtypes such as H1, H2, H5, H6, H8, H9, H11, H12, H13, H16, H17, and H18 (CDC, 2023). It plays a dual role in the viral life cycle: the HA1 subunit mediates binding to sialic acid receptors on the host cell surface, while the HA2 subunit facilitates the fusion of the viral envelope with the endosomal membrane (Skehel & Wiley, 2000). Because the stem region of Group 1 HA is highly conserved across different subtypes, it has become a primary focus for the development of broadly neutralizing antibodies and universal influenza vaccines (Throsby et al., 2008). Unlike seasonal vaccines that target the rapidly mutating head region, therapeutics targeting the Group 1 HA stem aim to provide cross-protective immunity against multiple strains, including those with pandemic potential (Corti et al., 2011). Successful inhibition of this target prevents viral entry into host cells, effectively halting the infection process. This target is also the focus of small molecule fusion inhibitors that bind to the hydrophobic pocket in the HA stem, preventing the conformational change required for fusion. Monitoring efficacy against this target often involves measuring stem-specific antibody titers or neutralization assays against diverse Group 1 subtypes.

Other names

Group 1 HAInfluenza A virus hemagglutinin group 1H1-cluster HAH5-cluster HAH9-cluster HA

Neutralization of viral infectivity by blocking sialic acid binding or preventing the pH-induced conformational change required for membrane fusion (Skehel & Wiley, 2000; Throsby et al., 2008).