MAPPING OF V(BETA)11(-CELL EPITOPES ON MYCOBACTERIAL ANTIGEN IN MOUSEPRIMED WITH MYCOBACTERIUM-TUBERCULOSIS() HELPER T)

Antigenic epitopes for Mycobacterium tuberculosis-reactive T cell immu ne responses have been mapped using the purified Mycobacterium protein antigen. Lymph node cells from C57BL/6 mice that had been immunized w ith heat-killed M. tuberculosis were cultured with various Mycobacteri um protein antigens and their reactivity was monitored by proliferativ e response. Usage of the TCR beta chain repertoire was analyzed by flo w cytometry. Stimulation of M. tuberculosis-primed lymph node cells wi th MPT59 (antigen 85B, alpha antigen) induced proliferative response, production of IL-2 and IFN-gamma, and the expansion of V(beta)11(+) CD 4(+) T cells in conjunction with antigen-presenting cells in an I-A(b) -restricted manner, Lymph node cells from non-primed mice failed to pr oliferate in response to MPT59. Using peptides covering the complete m ature 285 amino acids long MPT59 protein as 15-mer molecules overlappi ng by five amino acids, we identified the antigenic epitope for MPT59- specific V(beta)11(+) T cells. The 15-mer peptide, covering amino acid residues 240-254 of MPT59 [peptide-25 (amino acids 240-254)], contain s the motif that is conserved for I-A(b) and requires processing by an tigen-presenting cells to trigger peptide-25-specific V(beta)11(+) CD4 (+) T cells. We conclude from these results that MPT59 and peptide-25 (amino acids 240-254) are not superantigens and require antigen proces sing in order to stimulate V(beta)11(+) T(h)1 cells, This experimental system will provide us with a useful tool for delineating the regulat ion of T cell development in a particular subset of M. tuberculosis in fection and for developing antigenic peptides for T(h)1-dominant immun e responses.