Immunol Effects And Protect Efficiency Elicited By DNA Vaccine Contained Th1 Epitopes Of Tuberculosis ESAT-6 Antigen And Flt-3 Ligand

Tuberculosis (TB) is a world wide re-emerging disease that remains one of the leading causes of morbidity and mortality in humans. According to the latest report of WHO, over one third of the whole world's population (about 2 billion) are infected with TB, and this morbidity will be higher among patients infected with HIV. China is one of the world's 22 countries with high burden of tuberculosis. At present, the only available TB vaccine is the attenuated strain of Mycobacterium bovis Bacillus Calmette-Guérin (BCG). Although effective in preventing M.tb infection in newborns and toddlers, BCG provides poor protection in adult pulmonary tuberculosis with varying protective efficacy ranging from 0 to 80%. Thus, a novel and more effective vaccination strategy against TB is urgently needed.We have constructed a multi-epitope DNA vaccine of Mycobacterium tuberculosis (M. tb) which encoding the Th1 epitopes of early secreted antigenic target (ESAT-6) and fms-like tyrosine kinase 3 ligand (FL) in earlier study (pIRES-TH-FL). This reseach is aimed to evaluate the immunol effects and protect efficiency elicited by this DNA vaccine. Our work is based on this: Part I: Immune response triggered by recombinant DNA vaccine contained Th1 epitopes of tuberculosis ESAT-6 antigen and Flt-3 ligand with prime-boost strategyObjective: To study the immune response triggered by M. tb ESAT-6 Th1 epitopes and FL recombinant DNA vaccine by prime-boost strategy. Methods: C57BL/6 mice were inoculated with DNA vaccine intramuscular immunization, and for the prime-boost group, a DNA intramuscularly prime-soluble Ags intranasal boost strategy was employed. The spleen cell proliferation responses, the Th1/Th2 cytokines levels (IFN-γ,IL-12,IL-4,IL-10), the titer of ESAT-6 specific IgG antibody, the IFN-γ+T cell ELISPOT assay and the specific in vivo CTL assay were examined. Results: The M. tb ESAT-6 Th1 epitopes and FL recombinant DNA vaccine elicited remarkably higher levels of Th1 cytokines (IFN-γand IL-12) and CTL activity. Significantly enhanced levels of ESAT-6-specific antibody were also noted. The prime-boost immunization elicited stronger Th1 immune responses.Conclusion: This new M.tb vaccine can effectively elevate the cellular immunity of C57BL/6 mice. Part II: Protect efficiency elicited by recombinant DNA vaccine contained Th1 epitopes of tuberculosis ESAT-6 antigen and Flt-3 ligand with prime-boost strategyObjective: To evaluate the protect efficiency elicited by M. tb ESAT-6 Th1 epitopes and FL recombinant DNA vaccine. Methods: C57BL/6 mice were inoculated with the DNA vaccine intramuscular immunization, and for the prime-boost group, a DNA intramuscularly prime-soluble Ags intranasal boost strategy was employed. After the final immunization mice were challenged by intratracheal instillation with M. tb H37Rv, the bacterial burdens in the lungs and spleens as well as the pathologic pulmonary injury were examined. Results: After immunization with the M. tb ESAT-6 Th1 epitopes and FL recombinant DNA vaccine in C57BL/6 mice, reduced bacterial loads in lung and spleen were noted. Profound attenuation of lung inflammation and injury was showed by H&E stain and immunohistochemistry. Conclusion: A better protection against M. tb challenge was achieved after immunization with recombinant DNA vaccine contained Th1 epitopes of M. tb ESAT-6 antigen and FL. The prime-boost strategy could enhance this protect efficiency.