Abstract: Objective To study the immunogenicity and protective efficacy of M.tuberculosis MPT64 plasmid DNA.Methods The mice were immunized with the saline (A),plasmid vector (B), M.bovis BCG (C),and MPT64 plasmid DNA (D),and were then infected by intraperitoneal injection M.tuberculosis strain H₃₇R_v.MPT64 specific antibodies were determined by ELISA.Their lungs,livers and spleens were taken and observed their pathological changes,weighted and performed mycobacterial cultures 4 or 9 weeks after infection.Spleen cells were tested for proliferative responses.Results MPT64 specific antibodies increased in 4 of 10 group D mice.The stimulation rates of spleen cells increased significantly in group D mice compared to those in the other three group mice at 4 weeks after infection.The weights of lungs,livers and spleens in group A,B and D mice were higher than those in group C mice.The spleens CFUs in group A were more than those in the other three groups.The CFUs of lungs and livers had no significant difference among these four groups.The serious lesions could be observed in lungs of group A and B,while not in group C.Group D were different individually.The stimulation rates of spleen cells decreased significantly in group A and B mice,and increased significantly in group D mice compared to those in group C mice at 9 weeks after infection.The weights of lungs,livers and spleens had no significant difference among these four groups.The livers CFUs in group C mice were lower than those in the other three groups mice.Some lesions could be observed in lungs,but not in liver and spleen of each group mice.Conclusions M.tuberculosis MPT64 DNA vaccine,which was immunized mice by intramuscle injection,could induce specific humoral and cellular immune response and provide some degree of protection against Mycobacterium tuberculosis challenge.

Key words: Antigen, MPT64 protein DNA vaccine, Immunization, Mycobacterium,tuberculosis