The purified recombinant SsTroA proteins were screened for reactivity with antisera by western blotting. Antisera directed against recombinant SsTroA was produced in rabbits according to the standard protocol [58] . Total bacterial protein and purified protein were then resolved by 12% SDS-PAGE and transferred onto a nitrocellulose membrane (GE Healthcare) for the western blot-based detection of protein SsTroA as previously described [17] . Animal experiments were conducted in compliance with the regulations of the Beijing Administration Office of Laboratory Animal.