The diagnostic potential of MPT63-derived HLA-A*0201-restricted CD8+T-cell epitopes for active pulmonary tuberculosis

Abstract

MPT63 protein is found only in Mycobacterium tuberculosis complex, including M. tuberculosis and M. bovis. Detection of MPT63-specific IFN-γ-secreting T cells could be useful for the diagnosis of tuberculosis (TB) diseases. In the present study, the HLA-A*0201 restriction of ten predicted MPT63-derived CD8+T-cell epitopes was assessed on the basis of T2 cell line and HLA-A*0201 transgenic mice. The diagnostic potential of immunogenic peptides in active pulmonary TB patients was evaluated using an IFN-γ enzyme-linked immunospot assay. It was found that five peptides bound to HLA-A*0201 with high affinity, whereas the remaining peptides exhibited low affinity for HLA-A*0201. Five immunogenic peptides (MPT6318-26, MPT6329-37, MPT6320-28, MPT635-14 and MPT6310-19) elicited large numbers of cytotoxic IFN-γ-secreting T cells in HLA-A*0201 transgenic mice. Each of the five immunogenic peptides was recognized by peripheral blood mononuclear cells from 45% to 73% of 40 HLA-A*0201 positive TB patients. The total diagnostic sensitivity of the five immunogenic peptides was higher than that of a T-SPOT.TB assay (based on ESAT-6 and CFP-10) (93% versus 90%). It is noticeable that the diagnostic sensitivity of the combination of five immunogenic peptides and T-SPOT.TB assay reached 100%. These MPT63-derived HLA-A*0201-restricted CD8+T-cell epitopes would likely contribute to the immunological diagnosis of M. tuberculosis infection and may provide the components for designing an effective TB vaccine.