The recombinant protein (50ng) were resolved by SDS-PAGE, transferred to PVDF membrane and probed with anti-human H1N1/HA1 antibody (1:1000). Proteins were visualized using a goat anti-mouse secondary antibody conjugated to HRP and an ECL detection system. Lane 1.: Recombinant human H1N1 protein Lane 2.: Recombinant human H3N2 protein Lane 3.: Recombinant human H5N1 protein