Epitopes of a foot-and-mouth disease virus (FMDV) capsid protein VP1 complex and a chimera of 6xHis-tagged cholera toxin B subunit (hCTB) were expressed in Hansenula polymorpha and used together as a mucosal vaccine. Antibody and cytokine responses to VP1-hCTB vaccine and protection against FMDV were evaluated by ELISA and a virus challenge test in mice, respectively. VP1-hCTB directly enhanced the expression of interleukin-5 (IL-5) both in serum and supernatants of cultured spleen cells. After challenging suckling mice with 10(5) FMDV (=50% lethal dosage per mouse) a greater protection was seen after intraperitoneal and intranasal vaccinations than after oral vaccination. In swine immunized with VP1-hCTB, immune responses were achieved after three administrations, and the vaccine protected swine (80%) when challenged with 10(6.5) FMDV (=50% infectious dosage per swine). These results demonstrated the possibility of using CTB as a mucosal adjuvant to elicit protective immune responses against FMDV.