Human Cellular Immune Responses to the Aqueous Fraction of the TSP Antigen of Mycobacterium tuberculosis H37Rv

ABSTRACT

Phase-partitioning with Triton X-114 (TX114) was applied to the TSP antigen, which may be preferentially associated with the cell wall of M. tuberculosis. The hydrophilic protein components of the TSP antigen were successfully separated from integral hydrophobic macromolecules. To further characterize and examine the cellular immune response of the aqueous fraction of the TSP antigen (TSPa), the in vitro properties of the antigen were measured by lymphoproliferation; surface expression of IL-2 Ra on T lymphocytes was analyzed by flow cytometry; and the cytokine mRNA expression pattern was determined by RT-PCR. Significant lymphoproliferative responses to the TSPa antigen were observed in healthy tuberculin reactive donors after a 5 day in vitro stimulation. TSPa treatment of PBMCs from healthy tuberculin positive subjects for 5 days resulted in progressive augmentation of IFN-r, II 2, and IL-2Ra mRNA expression, as measured by RT-PCR, but considerably reduced IL-4 mRNA expression. In addition, the TSPa antigen stimulated more IL-12 p40 mRNA production than did the PPD antigen, and graduaBy suppressed IL- 10 mRNA expression. Moreover, the CD3' T cells of tuberculin positive subjects displayed a profound increase in their expression of the II 2Ru protein (39.0%) in response to the TSPa antigen. Proliferation was correlated with IL-2 and IL-2Ra mRNAs, but not correlated with distinct IFN-r or IL-12 p40 mRNA production. These findings strongly suggest that the TSPa antigen preferentially evokes the generation of a Thl-like immune response in healthy tuberculin reactors.