Added value of long-term cytokine release assays to detect Mycobacterium tuberculosis infection in HIV-infected subjects in Uganda

OBJECTIVE(S): To investigate whether mycobacterial antigen-induced cytokine secretions are helpful in detecting Mycobacterium tuberculosis (Mtb) infection in a cohort of HIV-infected patients living in a country with a high burden of Mtb and HIV infections, and to determine their predictive value for the development of tuberculosis (TB)-associated immune reconstitution inflammatory syndrome (IRIS). DESIGN: 352 HIV-infected patients (186 with active TB) were prospectively enrolled when initiating antiretroviral therapy (ART). Sequential blood samples were collected during the first 6 months of ART. 83 HIV-uninfected subjects (39 with active TB) were enrolled as controls. METHODS: The concentrations of 13 cytokines were measured in supernatants from blood mononuclear cells in vitro stimulated with purified protein derivative (PPD), heparin-binding haemagglutinin (HBHA) or early-secreted antigen 6 (ESAT-6) and culture filtrate protein-10 (CFP-10), and results were compared to those of tuberculin skin tests (TST). RESULTS: The best detection of Mtb infection was achieved by ESAT-6/CFP-10-induced IFN-gamma concentrations but results were often negative for patients with CD4 T-cell counts <50/mm. Patients with active TB were identified by high ESAT-6/CFP-10-induced IL-6. Conversions of interferon-gamma-release assays (IGRA) and TST occurred under ART, and combined TB- and antiretroviral treatments of co-infected patients resulted in a decrease of ESAT-6/CFP-10- and an increase of HBHA-induced IFN-gamma responses. No Mtb antigen-induced cytokines allowed us to predict TB-IRIS or ART-associated TB. CONCLUSIONS: In Uganda, ESAT-6/CFP-10-IGRA is better in detecting Mtb infection than TST and, when combined with a HBHA-IGRA, could help to evaluate anti-TB treatment success.