Hemagglutinin (HA) of H3N2 variant influenza virus (HA)

Hemagglutinin (HA) is the primary surface glycoprotein of the H3N2 variant (H3N2v) influenza virus, a swine-origin virus that occasionally infects humans (CDC, 2023). It serves two primary roles: recognizing and binding to sialic acid receptors on the host cell surface and facilitating the fusion of the viral and endosomal membranes to release the viral genome into the cytoplasm (UniProt, 2024). The H3N2v HA is antigenically distinct from seasonal H3N2 viruses, which increases the risk of infection in populations with low pre-existing immunity, particularly children (PubMed, 2012). As the principal antigen of the influenza virus, HA is the primary target for vaccine-induced neutralizing antibodies and is the focus of development for broad-spectrum monoclonal antibodies like CR9114 (Science, 2012). Small molecule inhibitors such as umifenovir also target the HA protein by preventing the pH-dependent conformational changes required for membrane fusion (PubMed, 2019). Monitoring mutations in the HA gene is vital for assessing the pandemic potential of H3N2v and ensuring the efficacy of candidate vaccine viruses (WHO, 2024).

Other names

H3 HemagglutininH3N2v HAInfluenza A virus H3N2v hemagglutininHemagglutinin protein

Neutralization of viral entry by blocking the binding of the hemagglutinin globular head to host sialic acid receptors or by inhibiting the conformational change required for membrane fusion (PubMed, 2019).