In-depth immunophenotyping with mass cytometry during TB treatment reveals non-canonical T-cell subsets associated with sputum culture conversion

Tuberculosis (TB) is a difficult-to-treat infection because of multidrug regimen requirements based on drug susceptibility profiles and treatment observance issues. TB cure is defined by mycobacterial sterilization, technically complex to systematically assess. We hypothesized that microbiological outcome was associated with stage-specific immune changes in peripheral whole blood during TB treatment. The T-cell phenotypes of treated TB patients were prospectively characterized in a blinded fashion using mass cytometry after Mycobacterium tuberculosis ( Mtb ) antigen stimulation, and then correlated to sputum culture status. At two months of treatment, cytotoxic and terminally differentiated CD8 + T-cells were under-represented and naïve CD4 + T-cells were over-represented in positive- versus negative-sputum culture patients, regardless of Mtb drug susceptibility. At treatment completion, an antigen-driven T-cell immune shift towards differentiated subpopulations was associated with TB cure. Overall, we identified specific T-cell profiles associated with slow sputum converters, which brings new insights in TB prognostic biomarker research designed for clinical application. Summary In patients treated for pulmonary TB, high-dimensional immune profiling with mass cytometry revealed that Mycobacterium tuberculosis culture conversion is associated with newly characterized peripheral CD8 + T-cell phenotypes. This paves the way for new immune biomarkers associated with mycobacterial sterilization.