Monitoring Anti-tuberculosis Treatment Response Using Analysis of Whole BloodMycobacterium tuberculosisSpecific T Cell Activation and Functional Markers

Background Blood-based biomarkers have been proposed as an alternative to current sputum-based treatment monitoring methods in active tuberculosis (ATB). The aim of this study was to validate previously described phenotypic, activation, and cytokine markers of treatment response in a West African cohort. Methods Whole blood immune responses toMycobacterium tuberculosisESAT-6/CFP-10 (EC) and purified protein derivative (PPD) were measured in twenty adults at baseline and after 2 months of standard TB treatment. Patients were classified as fast or slow responders based on a negative or positive sputum culture result at 2 months, respectively. Cellular expression of activation markers (CD38, HLA-DR), memory markers (CD27), and functional intracellular cytokine and proliferation (IFN-gamma, Ki-67, TNF-alpha) markers were measured using multi-color flow cytometry. Results There was a significant increase in the proportion of CD4(+)CD27(+)cells expressing CD38 and HLA-DR following EC stimulation at 2 months compared to baseline (p= 0.0328 andp= 0.0400, respectively). Following PPD stimulation, slow treatment responders had a significantly higher proportion of CD8(+)CD27(-)IFN-gamma(+)(p= 0.0105) and CD4(+)CD27(+)HLA-DR(+)CD38(+)(p= 0.0077) T cells than fast responders at baseline. Receiver operating curve analysis of these subsets resulted in 80% sensitivity and 70 and 100% specificity, respectively (AUC of 0.82,p= 0.0156 and 0.84,p= 0.0102). Conclusion Our pilot data show reductions in expression of T cell activation markers were seen with treatment, but this was not associated with fast or slow sputum conversion at 2 months. However, baseline proportions of activated T cell subsets are potentially predictive of the subsequent speed of response to treatment.