Repeated Immunization with BCG Vaccine Induced Cutaneous Thermal Hypersensitivity in Normal Mice

A significant alleviation in inflammatory visceral pain has been reported after vaccinated against bacillus Calmette-Guerin (BCG) in mice. Accordingly, we investigated whether immunization via repeated vaccination with BCG may effect on the thermal somatic pain threshold in mice Materials and Methods: Mice (n=5) were immunized by subcutaneously administration of human BCG vaccine (0.1, 1 and 10 mg/mice) once per week for 9 weeks. At the end of each week, somatic pain threshold of mice was investigated using an acute pain model based on the warm water tail withdrawal test. Results: Mice immunized with BCG vaccine showed significant gradual hyperanalgesic response tothermal painful stimulation of the tail during 9th week of treatment, in comparison with before treatment period.The hyperalgesic response was reversed by naloxone pretreatment. Conclusion: The immunotherapy with BCG vaccine induces a secondary adaptive immune response against vaccine antigens that caused a change in somatic thermal pain threshold in mice. It seemsthat the hyperanalgesic response is related to change in endogenous opioid system function in mice.