Isolation and Immunologic Characterization of the Surface Protein Antigens of Mycobacterium tuberculosis H37Rv

다국어 초록 (Multilingual Abstract)

Mycobacterial antigens can be divided into several groups on the basis of their subcellular Iocalization (cytoplasmic, cell wall associated, or secreated). Compared to the secreted protein antigen, little is known about the surface protein antigens associated with the cell wall of Mycobacterium tuberculosis. This is the first study on the isolation and the cellualr immune responses of Triton X-100 solubilized protein (TSP) antigen which may be preferentially associated with the cell wall of M. tuberculosis. We investigated the immunological responses of peripheral blood mononuclear cells (PBMCs) to the TSP antigen in tuberculosis (TB) patients and healthy individuals, and compared with those induced by the 30 kDa antigen from M. tuberculosis H37Rv culture filtrates, identified as a biologically important secreted protein.
Significant lymphoproliferative responses to the TSP antigen were observed in healthy tuberculin reactive donors, newly diagnosed TB patients and some of the chronic TB patients after a 6-day in vitro stimulation; these being higher than those to the 30 kDa antigen. Furthermore, analysis by flow cytometry indicated an preferential expansion of CD^4+ T lymphocytes by the TSP antigen in healthy tuberculin reactive donors and patients with pulmonary TB.
Treatment of PBMCs of healthy tuberculin reactors with TSP antigen for longer than 48 hrs resulted in progressive augmentation of IFN-γ, IL-2 and TNF-α mRNA measured by RT-PCR, but considerably reduced IL-4 mRNA expression after 5 days. After stimulation with the 30 kDa antigen, the rates of IFN-γ mRNA expression without detectable IL-4 mRNA in healthy controls and TB patients were 13.0% and 4.2%, respectively. Interestingly, those by the TSP antigen were increased to 34.8% and 45.8%. Furthermore, two other immune manifestations to the TSP antigen were observed in the TB patient of treatment-failed cases. The high responders showed a 10-fold-higher lymphoproliferation and induced more IFN-γ, IL-2 and TNF-α mRNA expression upon the TSP antigen stimulation than the low responders. After 2 months, they converted to negative on a direct smear and/or culture, and clinically and radiographically improved.
These results suggest that the TSP antigen of M. tuberculosis may be highly immunogenic, a strong inducer of cytokine mRNA associated with Th1 and/or macrophage activation, such as IFN-γ, IL-2 and TNF-α. IN conclusion, the TSP antigen can be used as a T cell immunogen associated with protective immunity against tuberculosis in humans.