Protective efficacy of DNA vaccine encoding tubercle MPT64 in mice challenged with M. tuberculosis

    SUN Ping, LUO Xuª²Dong, ZHU Daoª²Yin, TANG Guoª²Jian

    1Department of Surgery, 3417 Hospital, Zunyi 563000, China, 2Department of Microbiology, Chongqing University of Medical Science, Chongqing 400016, China

    ¡¾Abstract¡¿ AIM: To explore the protective efficacy of the DNA vaccine encoding Mycobacterium tuberculosis MPT64 in mice infected with Mtb. METHODS: C57BL/6 mice were intramuscularly immunized with the DNA vaccines or BCG (i.d.). The mice were challenged with 106 CFU H37Rv via lateral tail vein 35 d after the third immunization for DNA vaccine groups and 100 d after for BCG vaccinated group. The mice in the vaccinated groups and control groups were sacrificed 42 d after challenge. The lungs and spleens were removed respectively and the number of CFU in organs and histopathologic changes were determined. The antibody level, IFNª²¦Ã, ILª²4 and the survival time in all of the mice were evaluated. RESULTS: The antibody titer of pcDNA/MPT64 group was higher than that of other groups (P<0.05). Both the level of IFNª²¦Ã produced by spleen lymphocytes and the spleen lymphocyte proliferation from BCG group and pcDNA/MPT64 group were higher than those of other groups (P<0.05), and no ILª²4 was found in all groups. The number of bacterial colonies in the lungs and spleens significantly decreased at 6th week postchallenge in all the vaccinated groups (P<0.05), especially in BCG group (P<0.01). The pulmonary histopathological changes were observed 6 weeks following challenge with M.tuberculosis H37Rv. In PBS and pcDNA3.1 groups, the lesion was characterized by seroplastic inflammatory infiltration and lung tissue necrosis, and in BCG group by granulomas and numerous macrophages, lymphocytes and a few epithelioid cells. The lesion in pcDNA/MPT64 groups was characterized by seroplastic inflammatory infiltration and a few macrophages. The results in spleen were similar to those in lungs. The survival time of BCG vaccinated mice after challenge with M.tuberculosis H37Rv was longer than that of other groups. The survival time of pcDNA/MPT64 group was longer than that of negative control groups. CONCLUSION: The pcDNA/MPT64 can improve the protective efficacy of immunized mice against M.tuberculosis challenge. ......