Interleukin-6 and Mycobacterium tuberculosis dormancy antigens improve diagnosis of tuberculosis

Objectives: IFN gamma-release assays (IGRAs) used for diagnosis of Mycobacterium (M.) tuberculosis infection have limited sensitivity. Alternative cytokines and M. tuberculosis latency-associated antigens may improve immune-based tests. Methods: Multiplex cytokine analyses was done in culture supernatants after 6-day in vitro restimulation with M. tuberculosis IGRA and latency-associated antigens (i.e. Rv2628, Rv1733) in tuberculosis patients (n = 22) and asymptomatic contacts (AC)s (n = 20) from Ghana. Results: Four cytokines (i.e. IFN gamma, IP-10, IL-22 and IL-6) were significantly increased after IGRA-antigen specific restimulation. IFN gamma, IP-10, and IL-22 correlated positively and showed no differences between the study groups whereas IGRA-antigen induced IL-6 was significantly higher in tuberculosis patients. Using adjusted IGRA criteria, IL-6 showed the highest sensitivity for detection of tuberculosis patients (91%) and ACs (85%) as compared to IFN gamma, IP-10, and IL-22. Rv2628 and Rv1733 restimulation induced significantly higher IFN gamma, IP-10, and IL-22 concentrations in ACs. Combined antigen/cytokine analyses identified study group specific patterns and a combination of Rv2628/Rv1733 induced IFN gamma with IGRA-antigen induced IL-6 was optimal for classification of tuberculosis patients and ACs (AUC: 0.92, p<0.0001). Conclusions: We demonstrate the potency of alternative cytokines, especially IL-6, and latency-associated antigens Rv1733/Rv2628 to improve detection of M. tuberculosis infection and to classify tuberculosis patients and healthy contacts. (C) 2020 The British Infection Association. Published by Elsevier Ltd. All rights reserved.

Automated summary

IL-6 showed the highest sensitivity for detecting tuberculosis patients and asymptomatic contacts. Latency-associated antigens Rv2628 and Rv1733 increased concentrations of IFN gamma, IP-10, and IL-22 in asymptomatic contacts. The combination of IFN gamma induced by Rv2628/Rv1733 and IL-6 induced by IGRA-antigen was optimal for classifying tuberculosis patients and asymptomatic contacts.