CTL RESPONSE TO MYCOBACTERIUM-TUBERCULOSIS - IDENTIFICATION OF AN IMMUNOGENIC EPITOPE IN THE 19-KDA LIPOPROTEIN

The successful resolution of infection with Mycobacterium tuberculosis (M.tb) is believed to involve the induction of CTLs that are capable of killing cells harboring this pathogen, although little information is known about the MHC restriction or fine specificity of such CTLs, I n this study, we used knowledge of the HLA-A0201-binding motif and an immunofluorescence-based peptide-binding assay to screen for potentia l HLA-A0201-binding epitopes contained in the 19-kDa lipoprotein of M .tb (M.tb19). CD8(+) T cells derived from HLA-A0201(+) patients with active tuberculosis (TB) as well as tuberculin skin test-positive indi viduals who had no history of TB were used as effector cells to determ ine whether these epitopes are recognized by in vivo primed CTLs, An i n vitro vaccination system using HLA-A0201(+) dendritic cells (DCs) a s APCs was used to determine whether these epitopes can sensitize naiv e CD8+ T cells in vitro, leading to the generation of Ag-specific CTLs , The results show that an HLA-A0201-binding peptide comprised of res idues 88 to 97 of M.tb19 (P88-97) is recognized by circulating CD8(+) CTLs from both healthy tuberculin skin test-positive individuals and p atients with active TB but not by tuberculin skin test-negative subjec ts. Moreover, dendritic cells pulsed with this peptide induced class I MHC-restricted CTLs from the T cells of healthy unsensitized persons, Finally, CTL lines that were specific for P88-97 were shown to lyse a utologous monocytes that had been infected acutely with the H37Ra stra in of M.tb. These results demonstrate that M.tb19 elicits HLA class I- restricted CTLs in vitro and in vivo that recognize endogenously proce ssed Ag, Epitopes of the type identified here may prove useful in the design of an M.tb vaccine.