Functions and specificity of T cells following nucleic acid vaccination of mice against Mycobacterium tuberculosis infection.

The 38-kDa glycolipoprotein of Mycobacterium tuberculosis has been known to evoke prominent T cell and Ab responses in patients with active tuberculosis. In this study, we investigated its protective capacity using plasmid DNA immunization in a mouse experimental model. Prior knowledge of several antigenic determinants has been beneficial for analyzing the phenotype and specificity of T cells, which determine the efficacy of this vaccination procedure. C57BL/6 mice responded to the 38-kDa gene-pcDNA3 plasmid with strong CD4+ Th1 and CD8+ cytotoxic T cell responses of the IFN-gamma-producing Tc1 phenotype. After challenge with virulent tubercle bacilli, the bacterial load in the spleens and lungs of vaccinated mice was reduced to a level similar to that imparted by Mycobacterium bovis Bacille Calmette-Guérin vaccination. Notably, the specificity of CD4+ and CD8+ T cells from DNA-vaccinated and tubercle-infected mice was found to be strikingly different in respect of several peptide epitopes. The identified peptides recognized by T cells from protected mice are of further interest for the development of subunit-based vaccines against tuberculosis.