Evaluation of cytokine levels using QuantiFERON-TB Gold Plus in patients with active tuberculosis

Abstract Objectives A recently released new QuantiFERON (QFT) product, QFT TB Gold plus (QFT-plus), is optimized for both CD4 and CD8 responses and reported to have higher sensitivity compared to the former QFT-3G. Previously, using supernatants of QFT-3G, we and others have demonstrated that cytokines other than IFN-γ may be useful in diagnosing tuberculosis. The present study aimed to identify cytokines that are useful for accurately diagnosing active tuberculosis by using QFT-plus and compared the data to those with QFT-3G. Methods Eighty-three active tuberculosis patients and 70 healthy control subjects who were examined by QFT at Tokyo National Hospital from June 2017 to July 2018 were enrolled. QFT-3G and QFT-plus were performed according to the manufacturer's instructions. At the same time, blood cell culture supernatants were collected and assayed for their cytokine levels using R&D Systems Luminex Assay and MAGPIX System. The levels of cytokines were compared between different antigen-containing tubes (3G Ag, TB1 and TB2 tubes), as well as between the patients and the control subjects. ROC curves were drawn, and the AUCs were calculated. Results Five cytokines, i.e., IL-2, IL-6, IL-8, IP-10 and MIP-1β, produced by human blood cells in three independent tubes containing different tuberculosis antigens were higher in the 3G Ag tube compared to both the TB1 and TB2 tubes. Further, when the TB1 and TB2 tubes were compared, TB2 showed greater production of only PDGF-BB, and less production of IL-6 and TNF-α. For diagnosing active tuberculosis, the levels of IP-10 were superior to the level of IFN-γ based on showing a larger AUC for ROC curves in our present study setting. Finally, the levels of IFN-γ, IL-1RA, IL-2, IP-10, MCP-1 and MIP-1β were distinctly different between the active tuberculosis patients and healthy controls. Conclusions In summary, there was no cytokine that was higher in the tubes of QFT-plus compared to the tube of QFT-3G, suggesting inferiority of QFT-plus antigens to 3G Ag in terms of elicitation of cytokine production. Our results also suggest the usefulness of cytokines that showed a significant difference between the active tuberculosis patients and the healthy controls—namely, IFN-γ, IL-1RA, IL-2, IP-10, MCP-1 and MIP-1β—for diagnosing tuberculosis, but the roles of these cytokines in the pathogenesis of tuberculosis need to be elucidated (UMIN000035253).