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Antigen‐specific T cells are central to the adaptive immune response against T. cruzi infection and underpin the efficacy of on‐going vaccine strategies. In this context, the present study focuses on T‐cell assays that define the parasite‐specificity on the basis of upregulation of TCR stimulation‐induced surface markers. For this purpose, we tested different dual marker combinations (OX40, CD25, CD40L, CD137, CD69, PD‐L1, CD11a, CD49d, HLA‐DR, CD38) to reliably identify activated CD4+ and CD8+ T‐cell populations from PBMCs of chronic Chagas disease (CCD) patients after 12 or 24 h of stimulation with T. cruzi lysate. Results demonstrated that activation‐induced markers (AIM) assays combining the expression of OX40, CD25, CD40L, CD137, CD69 and/or PD‐L1 surface markers are efficient at detecting T. cruzi‐specific CD4+ T cells in CCD patients, in comparison to non‐infected donors, after both stimulation times. For CD8+ T cells, only PD‐L1/OX40 after 24 h of antigen exposure resulted to be useful to track a parasite‐specific response. We also demonstrated that the agnostic activation is mediated by different T. cruzi strains, such as Dm28c, CL Brener or Sylvio. Additionally, we successfully used this approach to identify the phenotype of activated T lymphocytes based on the expression of CD45RA and CCR7. Overall, our results show that different combinations of AIM markers represent an effective and simple tool for the detection of T. cruzi‐specific CD4+ and CD8+ T cells. [ABSTRACT FROM AUTHOR]

Summary: Trypanosoma cruzi, the aetiological agent of Chagas disease, has a highly efficient detoxification system to deal with the oxidative burst imposed by its host. One of the antioxidant enzymes involved is the cytosolic tryparedoxin peroxidase (c‐TXNPx), which catalyses the reduction to hydrogen peroxide, small‐chain organic hydroperoxides and peroxynitrite. This enzyme is present in all parasite stages, and its overexpression renders parasites more resistant to the oxidative defences of macrophages, favouring parasite survival. This work addressed the study of the specific humoral and cellular immune response triggered by c‐TXNPx in human natural infection. Thus, sera and peripheral blood mononuclear cells (PBMC) were collected from chronically infected asymptomatic and cardiac patients, and non‐infected individuals. Results showed that levels of IgG antibodies against c‐TXNPx were low in sera from individuals across all groups. B‐cell epitope prediction limited immunogenicity to a few, small regions on the c‐TXNPx sequence. At a cellular level, PBMC from asymptomatic and cardiac patients proliferated and secreted interferon‐γ after c‐TXNPx stimulation, compared with mock control. However, only proliferation was higher in asymptomatic patients compared with cardiac and non‐infected individuals. Furthermore, asymptomatic patients showed an enhanced frequency of CD19+CD69+ cells upon exposure to c‐TXNPx. Overall, our results show that c‐TXNPx fails to induce a strong immune response in natural infection, being measurable only in those patients without any clinical symptoms. The low impact of c‐TXNPx in the human immune response could be strategic for parasite survival, as it keeps this crucial antioxidant enzyme activity safe from the mechanisms of adaptive immune response. c‐TXNPx induces proliferation and interferon‐γ secretion of peripheral blood mononuclear cells from asymptomatic and cardiac patients with chronic Chagas disease, with only proliferation being significantly higher in patients with no clinical symptoms. Furthermore, asymptomatic patients show an increment of CD19+ CD69+ cells upon exposure to c‐TXNPx. At a humoral level, c‐TXNPx fails to induce a strong IgG response in patients with chronic Chagas disease. [ABSTRACT FROM AUTHOR]

Numerous abnormalities of the peripheral blood T cell compartment have been reported in human chronic Trypanosoma cruzi infection and related to prolonged antigenic stimulation by persisting parasites. Herein, we measured circulating lymphocytes of various phenotypes based on the differential expression of CD19, CD4, CD27, CD10, IgD, IgM, IgG and CD138 in a total of 48 T. cruzi-infected individuals and 24 healthy controls. Infected individuals had decreased frequencies of CD19+CD27+ cells, which positively correlated with the frequencies of CD4+CD27+ cells. The contraction of CD19+CD27+ cells was comprised of IgG+IgD-, IgM+IgD- and isotype switched IgM-IgD- memory B cells, CD19+CD10+CD27+ B cell precursors and terminally differentiated CD19+CD27+CD138+ plasma cells. Conversely, infected individuals had increased proportions of CD19+IgG+CD27-IgD- memory and CD19+IgM+CD27-IgD+ transitional/naïve B cells. These observations prompted us to assess soluble CD27, a molecule generated by the cleavage of membrane-bound CD27 and used to monitor systemic immune activation. Elevated levels of serum soluble CD27 were observed in infected individuals with Chagas cardiomyopathy, indicating its potentiality as an immunological marker for disease progression in endemic areas. In conclusion, our results demonstrate that chronic T. cruzi infection alters the distribution of various peripheral blood B cell subsets, probably related to the CD4+ T cell deregulation process provoked by the parasite in humans. [ABSTRACT FROM AUTHOR]

Numerous abnormalities of the peripheral blood T cell compartment have been reported in human chronic Trypanosoma cruzi infection and related to prolonged antigenic stimulation by persisting parasites. Herein, we measured circulating lymphocytes of various phenotypes based on the differential expression of CD19, CD4, CD27, CD10, IgD, IgM, IgG and CD138 in a total of 48 T. cruzi-infected individuals and 24 healthy controls. Infected individuals had decreased frequencies of CD19+CD27+ cells, which positively correlated with the frequencies of CD4+CD27+ cells. The contraction of CD19+CD27+ cells was comprised of IgG+IgD-, IgM+IgD- and isotype switched IgM-IgD- memory B cells, CD19+CD10+CD27+ B cell precursors and terminally differentiated CD19+CD27+CD138+ plasma cells. Conversely, infected individuals had increased proportions of CD19+IgG+CD27-IgD- memory and CD19+IgM+CD27-IgD+ transitional/naïve B cells. These observations prompted us to assess soluble CD27, a molecule generated by the cleavage of membrane-bound CD27 and used to monitor systemic immune activation. Elevated levels of serum soluble CD27 were observed in infected individuals with Chagas cardiomyopathy, indicating its potentiality as an immunological marker for disease progression in endemic areas. In conclusion, our results demonstrate that chronic T. cruzi infection alters the distribution of various peripheral blood B cell subsets, probably related to the CD4+ T cell deregulation process provoked by the parasite in humans. [ABSTRACT FROM AUTHOR]