Protective immunization of hamsters against Opisthorchis viverrini infection is associated with the reduction of TGF-β expression

► We immunized the hamsters against Opisthorchis viverrini and got better protection than ever. ► The parasite could stimulate the TGF-β production which may lead to worm survival. ► The protection was found to associate with significant reduction of TGF-β levels.