The impact of anti-tuberculous antibiotics and corticosteroids on cytokine production in QuantiFERON-TB Gold In Tube assays

Introduction: The ability to monitor and confirm adequate treatment of latent TB infection (LTBI) would be a major advance. The potential immunomodulatory effects of anti-tuberculous drugs and steroids need to be considered in assessing the utility of cytokine-based assays for this purpose. Methods: We determined whether anti-tuberculous antibiotics or dexamethasone affect the production of IFN-gamma and other potential cytokine biomarkers (TNF-alpha, IL-1ra, IL-2, IL-10, IL-13, IP-10, MIP-1 beta) in the QuantiFERON-TB Gold In-Tube (QFT-IT) assay. Blood from ten adults with LTBI was added to one standard set of QFT-IT tubes and five further sets containing therapeutic concentrations of either isoniazid, rifampicin, isoniazid and rifampicin, ciprofloxacin or dexamethasone. Resulting supernatants were analysed by ELISA (QFT-IT assay IFN-gamma) and xMAP-Luminex assays (all cytokines). Results: Anti-tuberculous antibiotics had only a limited effect on categorical QFT-IT assay results and the production of cytokines. In contrast, dexamethasone resulted in a change in categorical results from positive to negative in four of ten patients, and caused a marked reduction in IL-13 and IL-1ra responses. Conclusion: Substantial changes in TB-antigen-induced IFN-gamma and other cytokine responses during treatment likely primarily reflect host immunological changes rather than immunomodulatory effects of anti-tuberculous antibiotics. Results from cytokine-based assays in patients on corticosteroids should be interpreted with caution. Crown Copyright (C) 2015 Published by Elsevier Ltd. All rights reserved.