Immunological exhaustion and functional profile of CD8+ T lymphocytes as cellular biomarkers of therapeutic efficacy in chronic Chagas disease patients

The lack of useful tools for detection the impact of treatment during the follow-up of chronic Chagas disease treated patients difficult the adequate care to the affected population. The objective of this study was to evaluate the functional response of CD8(+) T lymphocyte population, critical for the control of Trypanosoma cruzi infection, as a possible cellular biomarker of treated Chagas disease patients. Thus, we analyzed the antigen-specific CD8(+) T-cell response before and after benznidazole treatment in asymptomatic (indeterminate) and cardiac chronic Chagas disease patients. A marked dysfunctional process of the CD8(+) T cell population was found in patients with an advanced pathology. Thus, the cardiac patients have a higher co-expression of inhibitory receptors and a lower antigen-specific multifunctional capacity compared with that of asymptomatic patients. Remarkably, benznidazole treatment partially reverses this functional exhaustion process of CD8(+) T cells in both asymptomatic and cardiac Chagas disease patients. Thus, the co-expression of inhibitory molecules tends to be reduced after benznidazole treatment, mainly in asymptomatic patients, finding a significant drop in the expression of inhibitory receptors such as PD-1 and 2B4. In addition, the multifunctional antigen-specific response of CD8(+) T cells is enhanced after treatment in chronic patients. An increase in the subset of cells with cytotoxic capacity and production of the IFN-gamma cytokine was also observed in both treated asymptomatic and cardiac chronic Chagas disease patients. The results derived from this study show the improvement of the functional capacity of CD8(+) T cells after treatment which could be have a positive effect on parasitic control. In addition, the phenotypic and functional profile of the CD8(+) T cells described could serve as a tool for monitoring the impact of benznidazole treatment.