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Background Tuberculosis remains the leading cause of human death.Currently,Bacillus Calmette-Guerin(BCG)isthe only available vaccine against tuberculosis but its efficacy is highly variable.Thus,developing new tuberculosisvaccines becomes an urgent task.In this study,we evaluated in BALB/c mice the humoral and cellular immuneresponses of recombinant BCG expressing the antigen ESAT-6 from Mycobacterium tuberculosis.Methods Escherichia coli-BCG shuttle plasmid named pDE22-esat-6 was constructed by inserting the BamHI/EcoRIdigested esat-6 gene PCR product into the similarly digested parental plasmid pDE22.BCG cells were transformedwith pDE22-esat-6,which was named recombinant BCG(rBCG).BALB/c mice were immunized subcutaneously on theback with 100 121 normal saline containing 106 CFU of BCG or rBCG.They were sacrificed after 4 weeks to detect theirhumoral and cellular responses.Results There was no any significant differences in the growth characteristics between the conventional BCG andrBCG.In immunized mice,the IgG antibody titres of rBCG group were as high as 1:8000,which was significantly higherthan that in BCG group(1:1400,P<0.05).The elicited IFN-γ level of rBCG group was(1993±106)pg/ml,which wasalso significantly higher than that in BCG group((1463±105)pg/ml,P<0.05).The splenocyte proliferation index ofrBCG group reached 4.34±0.31,which was higher than that of BCG group(3.79±0.24,P<0.05).Conclusion rBCG secreted expressing antigen ESAT-6 stimulated stronger humoral and cellular immune responsesthan BCG did,and,therefore may be the better vaccine against mycobacterium tuberculosis.
Background Tuberculosis remains the leading cause of human death.Currently, Bacillus Calmette-Guerin (BCG) is the only available vaccine against tuberculosis but its efficacy is highly variable.Thus, developing new tuberculosisvaccines becomes an urgent task.In this study, we evaluated in BALB / c mice the humoral and cellular immunerespons of recombinant BCG expressing the antigen ESAT-6 from Mycobacterium tuberculosis. Methods Escherichia coli-BCG shuttle plasmid named pDE22-esat-6 was constructed by inserting the BamHI / EcoRI digested esat-6 gene PCR product into the was digested with pC22 cells were transformed with pDE22-esat-6, which was named recombinant BCG (rBCG) .BALB / c mice were immunized subcutaneously on the back with 100 121 normal saline containing 106 CFU of BCG or rBCG.They were sacrificed after 4 weeks to detect their humoral and cellular responses. Results There was no any significant differences in the growth characteristics between the conventional BCG andrB CG. In immunized mice, the IgG antibody titres of rBCG group were as high as 1: 8000, which was significantly higherthan that in BCG group (1: 1400, P <0.05) 1993 ± 106) pg / ml, which wasalso significantly higher than that in BCG group ((1463 ± 105) pg / ml, P <0.05). The splenocyte proliferation index of rBCG group reached 4.34 ± 0.31, which was higher than that of BCG group (3.79 ± 0.24, P <0.05) .Conclusion rBCG secreted expressing antigen ESAT-6 stimulated stronger humoral and cellular immune responsesthan BCG did, and, therefore, may better the vaccine against mycobacterium tuberculosis.