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

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.

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.

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.

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.