Restoration of mycobacterial antigen-induced proliferation and interferon-γ responses in peripheral blood mononuclear cells of tuberculosis patients upon effective chemotherapy

Peripheral blood mononuclear cells (PBMC) were obtained from culture-proven tuberculosis (TB) patients before and after 2 and 6 months of chemotherapy with a multi-drug regimen. PBMC were tested for cellular responses in antigen-induced proliferation and interferon-gamma (IFN-gamma) assays in response to complex mycobacterial antigens (whole cell Mycobacterium bovis BCG and M. tuberculosis, cell walls and short-term culture filtrate [ST-CF] of M. tuberculosis), fractionated ST-CF antigens (fractions F1-F10) and ESAT-6. The responses in TB patients before anti-TB treatment were low (median stimulation index (SI) = 1-7, median delta IFN-gamma= 0-12 U ml(-1), and percent responders = 13-67%) to all the antigenic preparations. Following the administration of anti-TB chemotherapy for 2 months, there were significant (P < 0.05) improvements in the cellular responses (median SI = 9-76, median delta IFN-gamma = 3-70 U ml-1, and percent responders= 33-100%) to most of the antigenic preparations tested. However, concanavalin A-induced proliferation responses of PBMC from the same patients before and after 2 months of chemotherapy were high and comparable (median SI = 101 and 114, respectively, P > 0.05, 100% responders). A further increase in IFN-gamma responses (median delta IFN-gamma= 14-250 U ml-1 and percent responders = 43-100%) to mycobacterial antigens was observed in patients receiving chemotherapy for 6 months. Among the ST-CF fractions, F1 and F2 containing low molecular mass proteins resulted in the highest responses, whereas ESAT-6 showed responses comparable to these fractions only in a minority of the patients. HLA-DR typing of these patients showed heterogeneity in the expression of molecules encoded by HLA-DRB genes. These results show that effective chemotherapy restores cellular responses of TB patients to a large number of M. tuberculosis antigens, which could be useful in monitoring the efficacy of anti-TB treatment. (C) 2003 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.