Identification of HLA-DR4-restricted T-cell epitope on MPT51 protein, a major secreted protein derived from Mycobacterium tuberculosis using MPT51 overlapping peptides screening and DNA vaccination.

We identified a novel HLA-DR4-restricted CD4+ T-cell epitope on a secreted antigen of Mycobacterium tuberculosis, MPT51, in 004149-MM HLA-DR4-transgenic mice which express HLA-DRB1*0401, but not murine MHC class II molecules. The mice were immunized with plasmid DNA encoding MPT51 using gene gun and interferon (IFN)-gamma production from the immune splenocytes was analyzed. In response to overlapping synthetic peptides covering the mature MPT51 sequence, only one peptide, p191-210, stimulated the splenocytes to produce IFN-gamma. Further analysis using flow cytometry and computer-assisted algorithm, ProPred, narrowed down the region of CD4+ T-cell epitope to p191-202. The CD4+ T-cell epitope would be feasible for vaccine design against tuberculosis as well as for analysis of MPT51-specific T-cells in M. tuberculosis infection.