Figure 3
Production of IFN-γ against Rv2626c in whole blood from individuals highly exposed to Mycobacterium tuberculosis. (a,b) Whole blood was incubated with Rv2626c antigen (2.5 μg/mL) for 24 h. Afterwards, plasma samples were collected and IFN-γ production was evaluated by ELISA. The IFN-γ levels are expressed as IU/mL (IUIFN-γ/mL = IUIFN-γ/mL measured in Rv2626c tube – IUIFN-γ/mL measured in Negative control tube). Mean ± SEM for each group of subjects is shown. Each symbol represents an individual. *P < 0.05, ***P < 0.001, ****P < 0.0001. Kruskal-Wallis test and Dunn’s multiple comparisons post-test for unpaired samples. The horizontal dotted line indicates the Rv2626c IGRA cut-off (0.45 IUIFN-γ/mL). (c) ROC (Receiver Operating Characteristic) analysis for the IFN-γ responses to Rv2626c was performed to evaluate its potential use in discriminating LTBI (HW QFT positive) from other Mtb exposed individuals (CC QFT negative and positive and TB). AUC = 0.8258; P < 0.0001; 95% CI: 0.7348–0.9169.
