Identification of mycobacterial recombinant antigens recognized by human T cells

The identification of mycobacterial antigens recognized by human T cells is important for the development of new vaccines and diagnostic reagents, and in understanding the mechanisms involved in the pathogenesis of mycobacterial diseases. In this study, Escherichia coli cell lysates, containing mycobacterial recombinant antigens previously identified using antibodies, were tested with peripheral blood mononuclear cells (PBMC), T cell lines and T cell clones to identify the antigens recognized by human T cells. Although the PBMC responded to natural mycobacterial antigens by proliferation, they did not show any specific response to recombinant antigens containing lysates above the background level of proliferation induced by control lysates of E. coli. With T cell lines raised against whole mycobacteria, the problem of background proliferation was reduced but the specific responses to the lysates containing recombinant antigens were weak. The proliferative response to specific antigens improved by enriching the T cell lines with E. coli lysates containing homologous recombinant antigens. The best response to recombinant antigens was obtained with mycobacterial antigen-specific T cell clones. However, T cell clones did not respond to some of the antigens which induced proliferation of the enriched T cell lines from the same individuals. This could be because of the inherent bias in the cloning procedures which may lead to the expansion of selected T cell populations. Our results suggest that enriched T cell lines are best to determine the T cell reactivity of recombinant antigens, but T cell clones are required to demonstrate the existence of species-specific epitopes.