Hemagglutinin protein of influenza A and B (HA)

Hemagglutinin is a trimeric glycoprotein expressed on the surface of influenza A and B viruses and is essential for viral infectivity. Each monomer consists of two subunits (HA1 and HA2) generated by proteolytic cleavage from a precursor HA0. HA mediates viral entry by binding to sialic acid-containing receptors on the surface of host cells and facilitating fusion of the viral envelope with the host membrane in a low pH-dependent manner. Hemagglutinin is the main target of neutralizing antibodies, explains the major antigenic properties of the virus, and is a primary focus of seasonal and pandemic influenza vaccines. Due to its high variability, hemagglutinin underlies both antigenic drift (mutation) and antigenic shift (reassortment), contributing to influenza epidemics and pandemics[1][2][3].

Other names

Influenza hemagglutininViral hemagglutininHA protein

Neutralizing antibodies prevent receptor binding and membrane fusion by targeting HA. HA inhibitors (experimental) block conformational changes and/or sialic acid interaction. Vaccine-induced immunity promotes antibody responses against HA to prevent infection.