Mycobacterium tuberculosis reactive T cell clones from naturally converted PPD-positive healthy subjects: recognition of the M. tuberculosis 16-kDa antigen.

Mycobacterium tuberculosis reactive T cell clones were established from naturally converted PPD-positive healthy subjects and screened for proliferative reactivity against defined M. tuberculosis protein antigens of 16, 19, 65 (HSP65), and 71 (HSP70) kDa recombinantly expressed in Escherichia coli. Among the recombinant antigens tested, the M. tuberculosis 16-kDa protein antigen, as expressed from the lambda gt11 phage Y3155, was found to induce T cell proliferation. Crossreactivity studies showed that the epitope recognized was present in M. tuberculosis, M. africanum as well as the vaccine strain M. bovis BCG. The M. tuberculosis 16-kDa reactive T cell clone identified showed the CD4+, CD8- phenotype, secreted interferon-gamma upon antigen stimulation, and displayed major histocompatibility complex class II restricted cytotoxicity against M. tuberculosis pulsed macrophages. The results obtained suggest that the recombinant M. tuberculosis 16-kDa antigen can be recognized by human Th1 cells with potential relevance to protection.