Enhanced T cell responsiveness to Mycobacterium bovis BCG r32-kDa Ag correlates with successful anti-tuberculosis treatment in humans.

Th1 and Th2 cytokines play key role in protection from and pathogenesis of mycobacterial infection and their dynamic changes may predict clinical outcome of the patient. Patients with tuberculosis (TB) have a poorer cellular immune response to recombinant 32-kDa antigen (Ag) of Mycobacterium bovis (r32-kDa M. bovis) than do healthy volunteers. The basis for this observation was studied by evaluating the Th1 (gamma interferon [IFN-γ]) produced in response to the r32-kDa Ag M. bovis by peripheral blood mononuclear cells (PBMC) from patients with pulmonary TB (n=20), extra-pulmonary TB (n=13) and from healthy volunteers (n=9). Recombinant 32-kDa M. bovis stimulated PBMC from TB patients produced significantly lower levels of IFN-γ at 0 month, and increased at 2-4, and 6 months of treatment and were highly significant (p<0.000) compared to the responses in controls. The ratios of IFN-γ to IL-10 were low in patients newly diagnosed and improved both during and after treatment. The present study concludes that the levels of in vitro response to M. bovis BCG r32-kDa Ag leading to the specific release of IFN-γ increased after anti-tuberculosis treatment and seems to reflect the clinical status of the patient, thus reiterating the utility of this antigen in T cell based assays as a surrogate marker of cell mediated responses.

In vitro levels of interleukin 10 (IL-10) and IL-12 in response to a recombinant 32-kilodalton antigen of Mycobacterium bovis BCG after treatment for tuberculosis.

Cell-mediated immunity plays a major role in conferring protection against tuberculosis (TB) on an individual. It is not known whether the immune status correlates with the bacterial load or whether the immunity improves after treatment. Also, it may be important to monitor treatment by being able to discriminate between active disease and successfully treated TB. The main aim of this study was to investigate the usefulness of a recombinant 32-kDa antigen (r32-kDa Ag) of Mycobacterium bovis BCG (Ag85A-BCG) as a diagnostic marker in patients being treated for TB. Specifically, the in vitro T-cell assays and the release of interleukin-12 (IL-12) (Th1-type cytokine) and IL-10 (Th2-type cytokine) in response to the r32-kDa Ag of BCG were assayed in patients with either pulmonary (sputum positive/negative, n = 74) or extrapulmonary TB (n = 49) and healthy controls. The proliferative responses of stimulated cells at 0, 2 to 4, and 6 months of treatment increased and were highly significant (P < 0.000) compared to the responses in controls. The increase in IL-12 and decrease in IL-10 release suggest that there is cytokine expression modification during different stages of TB, and treatment seems to have an influence on the levels of these cytokines, suggesting an augmentation in the protective responses. The in vitro response to the M. bovis BCG r32-kDa Ag may be useful in monitoring treatment of TB.