HA, encoded by segment 4 of the IAV genome, is a glycoprotein of approximate 560 amino acid. The biologically active HA is a homologous trimeric molecule that is attached to the virion membrane through its carboxy terminus [11] . HA plays a critical role in the pathogenesis of IAVs. HA mediates IAVs' binding to the cellular receptor N-acetylneuraminic (sialic) acid as well as the subsequent membrane fusion process [12] . HA also stimulates host protective immunities, specifically the production of neutralizing antibodies. The generation of anti-HA neutralizing antibodies has been the major target for influenza vaccine development [11, 13] . Due to its specificity in immune response, HA is also an important target for IAV subtyping using immunoassays [7, 14] .