Influenza A Hemagglutinin H9

Hemagglutinin (HA) or haemagglutinin is a homotrimeric glycoproteinfound on the surface of influenza viruses and is integral to its infectivity. Hemagglutinin is a Class I Fusion Protein, having multifunctional activity as both an attachment factor and membrane fusion protein. Therefore, HA is responsible for binding Influenza virus to sialic acid on the surface of target cells, such as cells in the upper respiratory tract or erythrocytes,following which event the virus is internalised.