Enhancement of human T cell response to a peptide epitope of 38 kDa antigen of Mycobacterium tuberculosis by liposomes.

Diagnosis of tuberculosis a problem, specially in the regions harboring an abundance of both pathogenic and non-pathogenic mycobacteria. This study was undertaken to assess in such a situation the predictive value of proliferative T cell response to a peptide epitope ('38G') of the 38 kDa membrane protein of Mycobacterium tuberculosis. 3[H]-thymidine incorporation assays were done with peripheral blood mononuclear cells of tuberculoid leprosy and pulmonary tuberculosis patients. The donors were also classified as PPD responders (Stimulation Index, SI> 3) or non-responders (SI < or = 3) on the basis of their T cell response to the 'Purified Protein Derivative (PPD)' of M. tuberculosis. 38G peptide was used in either free or liposome-associated form prepared by the technique of 'Dehydration-rehydration Vesicles' (Kirby and Gregoriadis, 1984). While free peptide failed to induce a positive response in study subjects, its liposomal form was T cell stimulatory and distinguished, to certain extent, between PPD responders (corresponding SI > 3 in 54% subjects) and non-responders (SI > 3 in 29% subjects). However, it did not differentiate between leprosy and tuberculosis. The study supports use of liposomes as adjuvant vehicles for antigenic peptides designed to activate human T cells.