Influenza hemagglutinin subunit HA1 (HA1)

Influenza hemagglutinin subunit HA1 is the distal, globular head domain of the hemagglutinin (HA) glycoprotein found on the surface of influenza viruses. Its primary biological function is to mediate viral attachment by binding to sialic acid receptors on host respiratory epithelial cells, a critical first step in the viral life cycle (Skehel & Wiley, 2000). As a major B-cell and T-cell antigen, HA1 is the principal component of seasonal influenza vaccines, designed to elicit neutralizing antibodies that target the receptor-binding site to prevent infection (Gerhard, 2001; CDC, 2023). However, the HA1 domain is highly susceptible to antigenic drift, where point mutations in the antibody-binding sites allow the virus to escape host immunity, necessitating frequent updates to vaccine compositions (Carrat & Flahault, 2007). Beyond its role in active immunization, HA1 serves as a target for therapeutic monoclonal antibodies, such as Diridavumab, which provide passive immunity by blocking viral entry (Throsby et al., 2008). Understanding the structural epitopes of HA1 is vital for the development of next-generation vaccines aimed at providing broader protection against diverse influenza strains (UniProt P03437).

Other names

Hemagglutinin subunit 1HA globular headHA1 domainInfluenza HA1 antigen

Induction of neutralizing antibodies that block the viral receptor-binding site, preventing attachment to host sialic acid receptors and subsequent viral entry.