[Effects of Th1 cytokine gene on anti-CFP10 antibody production in BALB/c mice induced by Mycobacterium tuberculosis DNA vaccine].

Aim: To investigate the effects of plasmid containing mouse IL-12 and human IL-18 genes on the humoral immune response of mice immunized by CFP10 gene of Mycobacterium tuberculosis (MTB) H(37)R(v) strain.

Methods: Human IL-18 cDNA was amplified from RNA of PBMCs by RT-PCR and cloned into the pGEM-Teasy vector. After sequencing it was subcloned into the the sites of BamH I and EcoR I digestion of pcDNA3.1. BALB/c mice were injected intramuscularly by eukaryotic expression plasmid pcmIL12 and pcIL18, together with MTB CFP10 DNA vaccine, respectively. The same immunization repeated three times at intervals of two weeks. Mouse sera were collected at two weeks after the each injection. The titer of anti-CFP10 antibody was detected by ELISA.

Results: IL-18 cDNA was amplified successfully from RNA of human PBMCs by RT-PCR and the result of sequencing was correct. The IL-18 gene was correctly inserted into the vector pcDNA3.1 by being confirmed with BamH I and EcoR I digestion analysis, positive plasmid was called pcIL18. After being immunized with pcCFP10 three times, the end point titer of anti-CFP10 was 1:4 000, while the titer obtained by being immunized with pcIL18 + pcCFP10 was 1:8 000, but yet, after being immunized with pcmIL12+pcCFP10, the end point titer of anti-CFP10 antibody was only 1:200.

Conclusion: Combination of IL-18 gene with MTB CFP10 DNA vaccine can enhance the humoral immune responses to pcCFP10, whereas the immunization with IL-12 gene plus pcCFP10 made humoral immune response markedly descent. As for whether IL-18 gene plus MTB CFP10 DNA vaccine can induce markedly the cellular mediated immune response to CFP10 or not remains to be further investigated.