Hepatitis C Virus Affects Tuberculosis-Specific T Cells in HIV-Negative Patients

The occurrence of tuberculosis (TB) and hepatitis C virus (HCV) infections in the same patient presents a unique clinical challenge. The impact of HCV infection on the immune response to TB remains poorly investigated in TB+/HCV+ patients. This study was conducted to evaluate the impact of HCV on the T-cell-mediated immune response to TB in coinfected patients. Sixty-four patients with active TB infections were screened for coinfection with HCV. The expression of immune activation markers IFN-gamma, CD38, and HLA-DR on TB-specific CD4(+) T cells was evaluated by flow cytometry in TB-monoinfected patients, TB/HCV-coinfected patients, and healthy controls. IL-2, IL-4, IFN-gamma, TNF-alpha, and IL-10 levels were measured using ELISA. The end-of-treatment response to anti-TB therapy was recorded for both patient groups. Significantly lower levels of CD4(+)IFN-gamma(+)CD38(+) and CD4(+)IFN-gamma(+)HLA-DR+ T cells were detected in TB/HCV-coinfected patients compared to TB monoinfected patients and controls. TB+/HCV+-coinfected patients showed higher serum levels of IL-10. The baseline frequencies of TB-specific activated T-cell subsets did not predict the response to antituberculous therapy in TB+/HCV+ patients. We concluded that different subsets of TB-specific CD4(+) T cells in TB/HCV-infected individuals are partially impaired in early-stage HCV infection. This was combined with increased serum IL-10 level. Such immune modulations may represent a powerful risk factor for disease progression in patients with HCV/TB coinfection.