Immunogenicity of DNA vaccine expressing ESAT6ª²CFP10 fusion protein of Mycobacterium tuberculosis

    ZHANG Hai1, SHI Changª²Hong1, WANG Liª²Mei2, XUE Ying2, BAI Yinª²Lan2, XU Zhiª²Kai2

    1Laboratory Animal Research Center, 2Department of Microbiology, School of Basic Medicine, Fourth Military Medical University, Xi¬ðan 710033, China

    ¡¾Abstract¡¿ AIM: To evaluate the humoral and cellular immune response induced by the DNA vaccine expressing ESAT6ª²CFP10 fusion protein and to test its protective efficacy against Mycobacterium tuberculosis(MTB) challenge. METHODS: BALB/c mice were immunized intramuscularly three times with 100 ¦Ìg recombinant plasmid pcDNAª²e6c10. Two weeks after last immunization, the specific antibody titer and the stimulation index(SI) of spleen lymphocytes from the immunized mice were measured, and the levels of IFNª²¦Ã and ILª²2 and the activity of antigenª²specific CTL were detected. The DNA vaccineª²vaccinated BALB/c mice were infected with 1¡Á105 CFU(colony forming unit) MTB H37Rv through tail vein. Four weeks later, the bacteria load in spleen was determined. RESULTS: The titer of serum specific antibody in BALB/c mice immunized with DNA vaccine was 1¡Ã800. The SI of DNA vaccineª²immunized groups(2.42¡À0.13) was significantly higher than that of salineª²immunized group. The IFNª²¦Ã[(2449¡À12) ng/L]induced by DNA vaccine was not different from that in bacillus calmette guerin(BCG)ª²immunized group, while ILª²2[(198¡À16) ng/L] induced by DNA vaccine had significant difference from that of salineª²immunized group and was lower than that of BCGª²immunized group. The antigenª²specific CTL efficacy was 42%. Compared with the saline immunized mice (bacteria load was 6.51¡À0.13), a dramatic reduction of MTB replication was observed in the spleen (bacteria load was 4.51¡À0.23, P<0.05) of BALB/c mice immunized with DNA vaccine following a subsequent challenge, but the protective efficacy of DNA vaccine was lower than that of BCG vaccine. CONCLUSION: DNA vaccine expressing ESAT6ª²CFP10 fusion protein has a immunotherapeutic effect to prevent tuberculosis. ......