Combined detection of IFNγ, TGFα and IL-6 cаn discriminate between active TB disease and latent infection
Interferon gamma release assays are used for diagnosing Mycobacterium tuberculosis (M.tb.) infection. However these tests fail to differentiate active TB from latent TB infection (LTBI).
Aim: Selection of informative biomarkers for the diagnosing M.tb. infection and for discriminating between latent TB infection (LTBI) and active TB disease.
Materials and methods: We recruited 54 TB patients, 47 TB contacts and 43 healthy donors and performed the "QuantiFERON-TB Gold In-Tube" ("Cellestis", Аustralia). Using XMap technology levels of 10 cytokines (EGF, MIP-1β, VEGF, IL-2, IL-4, IL-6, IL-1α, IFN-α2, TGFα, TNFα) as well as sIL-2Rα and sCD40L were evaluated in unstimulated (NIL) and Mycobacterium tuberculosis specific antigen (AG) stimulated plasma. We also determined levels of IP-10 in 48 patients by ELISA.
Results: Six out of 13 biomarkers distinguished active TB from LTBI. As a result of making "decision tree" in JMP 9.0 software, we choose three the most informative cytokines. The combination between IFNγ, TGFα and IL-6 may possible to distinguish active TB from latent infection with sensitivity 96,3 % and specifity 80,7 % (AUC=0,9). We also observed very high levels of IP-10 and IL-2, which correlated with IFNγ levels (r=0,71 and 0,79 respectively).
Conclusion: IL-2 or IP-10 as well as IFNγ, detection could be used in a first step to diagnose (M.tb.) infection. A second step of the test could be performed if positive IL-2 / IP-10 / IFNγ results are obtained to measure three-marker combination of IFNγ, TGFα and IL-6 to differentiate individuals with active TB from LTBI.