T cells are central to adaptive immune response against T. cruzi infection. In the chronic stage of Chagas disease, circulating parasite-specific memory T cells show reduced functionality and increased expression of inhibitory receptors, possibly as a result of persistent antigenic stimulation. This exhausted phenotype has been linked to progression of cardiac pathology while, contrariwise, the presence of polyfunctional T cells shows association with therapeutic success and more efficient control of infection.Given this, we hypothesized that inhibitory receptors TIGIT, Tim-3 and Lag-3 may be involved in immune modulation of anti-T. cruzi T cell response, and therefore may play a role in the containment or the unleashing of inflammatory phenomena that ultimately lead to tissue damage and pathology. In this preliminary study, we assess the frequency of CD4 + T cells expressing each of these receptors and their relation to cellular activation.Samples from chronic Chagas disease patients with different degrees of cardiac compromise, and non-infected donors were analyzed under different stimulation conditions. Our results show that the frequency of TIGIT + CD4 + T cells is increased in Chagas patients, while Tim-3 + cells are more abundant in patients with signs of cardiac alterations. In addition, the frequency of Lag-3 + cells increases in non-activated CD4 + T cells from Chagas patients without demonstrable cardiopathy upon pathogen-specific in vitro antigenic stimulation.

The cardiomyopathy developed by patients with chronic Chagas disease (CCD), one of the most severe consequences of T. cruzi infection, is mainly associated with an imbalance between an excessive inflammatory reaction and a defective immunomodulatory profile cause by host-parasite interaction. Despite the growing importance of the regulatory function of B-cells in many malignancies, few studies have addressed their immunosuppressive role in chronic Chagas disease. In this work, we tackled this issue by studying the proportion of different B cell subpopulations and their capacity to secrete IL-10 in individuals with distinct clinical forms of CCD. Seven-colour flow cytometry was performed to examine the peripheral blood B cell compartment in chronic Chagas disease (CCD) patients with and without cardiac manifestations (n=10 for each group) and non-infected donors (n=9). Peripheral blood mononuclear cells (PBMC)were incubated for 5h with PMA, ionomicyn and brefeldin A. According to the expression of markers CD24, CD38 and CD27 showed an expansion of total B cell and transitional CD24 high CD38 high B cell subsets in CCD patients and non-infected donors. Furthermore, although no differences were observed in the frequency of total IL-10 producing B cells (B10) among the groups, CCD patients with cardiac involvement showed an increased proportion of transitional and naïve B10 cells compared to non-infected donors. These findings suggest that immature transitional CD24 high CD38 high B cells are greatly expanded in patients with the cardiac form of chronic Chagas disease and these cells retain their ability to secrete IL-10 compared to non-infected donors. Furthermore, the distribution of naïve, transitional and memory B cells inside the B10 cells followed the same pattern in chronic patients without cardiac involvement and non-infected individuals. Our work provides insight into the phenotypic distribution of regulatory B cell in CCD, an important step towards new strategies to prevent cardiomiopathy associated with T. cruzi infection.

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