Cell-mediated immune responses to complex and single mycobacterial antigens in tuberculosis patients with diabetes.

OBJECTIVE: To evaluate cell-mediated immune (CMI) response in diabetic and non-diabetic tuberculosis (TB) patients and healthy subjects in response to complex, fractionated and single antigens of Mycobacteriumtuberculosis. MATERIAL AND METHODS: Peripheral blood mononuclear cells (PBMC) were obtained from patients suffering from pulmonary TB and type II diabetes (n = 7), pulmonary TB without diabetes (n = 10) and healthy subjects without TB and diabetes (n = 10). PBMC were assessed for CMI responses in antigen-induced proliferation assays in response to complex mycobacterial antigens (whole cells, cell walls and culture filtrate of M. tuberculosis), a battery of naturally purified or recombinant produced secreted (ESAT6, MPT59, MPT64 and MTB38) and cytosolic (MTB10, MTB70, ML10, ML28, ML36, ML65 and MB65) mycobacterial antigens and fractionated culture filtrate proteins (fractions F1-F10) of M. tuberculosis. RESULTS: The majority (>70%) of diabetic and non-diabetic TB patients and healthy subjects responded to the complex antigens of M. tuberculosis. However, among the single antigens, ESAT6 was most frequently recognized by TB patients with and without diabetes, but least recognized by healthy subjects. The secreted antigens MPT59 and MPT64 were recognized by all the groups, whereas the cytosolic antigens were recognized best by healthy subjects. When tested with fractionated secreted proteins present in the culture filtrate of M. tuberculosis, the best responses in both diabetic and non-diabetic TB patients were obtained with fractions containing low-molecular-weight proteins. CONCLUSIONS: Diabetic and non-diabetic TB patients respond frequently to secreted low-molecular-weight ESAT6 antigen of M. tuberculosis, indicating that this antigen may be useful in the diagnosis of TB in both the groups.

HLA-DR binding prediction and experimental evaluation of T-cell epitopes of mycolyl transferase 85B (Ag85B), a major secreted antigen of Mycobacterium tuberculosis.

OBJECTIVE: To identify T-cell epitopes of Ag85B by analysis of its sequence for prediction to bind HLA-DR alleles and evaluate the predicted peptides for recognition by T cells in antigen-induced proliferation assays. MATERIALS/SUBJECTS AND METHODS: The complete sequence of Ag85B was analyzed for HLA-DR binding prediction to 51 HLA-DR alleles by using a virtual matrix-based prediction program (ProPred). Synthetic peptides covering the sequence of mature Ag85B were also analyzed for binding to HLA-DR alleles, and evaluated for recognition in antigen-induced proliferation assays with Ag85B-specific T-cell lines established from the peripheral blood mononuclear cells of 10 HLA-DR-heterogeneous tuberculosis patients. RESULTS: The ProPred analysis of the full-length Ag85B (325 aa), signal peptide (40 aa) and the mature protein (285 aa) predicted their binding to 100, 76 and 98% of the 51 HLA-DR alleles, respectively. The analysis of 31 synthetic peptides for binding to HLA-DR alleles showed that 4 of them could bind >50% HLA-DR alleles, and were considered promiscuous. Testing of Ag85B-specific T-cell lines with synthetic peptides showed that all of the T-cell lines responded to one or more peptides of Ag85B, and 9 of the 10 cell lines responded to one or more of the four peptides considered promiscuous for binding to HLA-DR alleles. CONCLUSION: The ProPred program was useful in predicting the HLA-DR alleles binding regions of Ag85B and identifying the promiscuous peptides recognized by T cells.