Increased CD4+/CD8+ Double-Positive T Cells in Chronic Chagasic Patients

Abstract

Background

CD4+/CD8+ double positive (DP) T cells have been described in healthy individuals as well as in patients with autoimmune and chronic infectious diseases. In chronic viral infections, this cell subset has effector memory phenotype and displays antigen specificity. No previous studies of double positive T cells in parasite infections have been carried out.

Methodology/Principal Findings

Seventeen chronic chagasic patients (7 asymptomatic and 10 symptomatic) and 24 non-infected donors, including 12 healthy and 12 with non-chagasic cardiomyopathy donors were analyzed. Peripheral blood was stained for CD3, CD4, CD8, HLA-DR and CD38, and lymphocytes for intracellular perforin. Antigen specificity was assessed using HLA*A2 tetramers loaded with T. cruzi K1 or influenza virus epitopes. Surface expression of CD107 and intracellular IFN-γ production were determined in K1-specific DP T cells from 11 chagasic donors. Heart tissue from a chronic chagasic patient was stained for both CD8 and CD4 by immunochemistry. Chagasic patients showed higher frequencies of DP T cells (2.1%±0.9) compared with healthy (1.1%±0.5) and non-chagasic cardiomyopathy (1.2%±0.4) donors. DP T cells from Chagasic patients also expressed more HLA-DR, CD38 and perforin and had higher frequencies of T. cruzi K1-specific cells. IFN-γ production in K1-specific cells was higher in asymptomatic patients after polyclonal stimulation, while these cells tended to degranulate more in symptomatic donors. Immunochemistry revealed that double positive T cells infiltrate the cardiac tissue of a chagasic donor.

Conclusions

Chagasic patients have higher percentages of circulating double positive T cells expressing activation markers, potential effector molecules and greater class I antigenic specificity against T. cruzi. Although K1 tetramer positive DP T cell produced little IFN-γ, they displayed degranulation activity that was increased in symptomatic patients. Moreover, K1-specific DP T cells can migrate to the heart tissue.

Author Summary

Chagas disease, produced by the blood parasite Trypanosoma cruzi, is considered a public health problem in Central and South America. Non sterile immunity can be achieved after acute infection. Parasite persistence can induce tissue damage in nearly 20% to 30% of chronically infected individuals. Indeed, chagasic cardiomyopathy is one of the consequences of the chronic infection. Antigen persistence and dysfunctional cellular immune response have been implicated in T. cruzi pathogenesis. Here, a higher frequency of circulating CD4+/CD8+ double positive T cells in chronic chagasic patients is reported as compared with non infected donors, including those with a non-chagasic cardiomyopathy. This cell subset also expressed more activation markers and stored more intracellular perforin. We have previously reported that CD8+ T cells from T. cruzi infected donors recognized the HLA-A*0201 restricted K1-peptide derived from the KMP-11 protein. Here, double positive T cells displayed higher percentages of recognition for the K1 peptide than single CD8+ T cells. These cells produce little IFN-γ, but display degranulation activity that was increased in the symptomatic group. Finally, double positive T cells can be localized in the heart tissue from a chronic chagasic donor.