cruzi-specific responses enriched in single IFN-+T cells with absence of TNF-+-producing T cells. IL-2 measured by ELISPOT assays in response toT. cruziantigens was prevalent amongT. cruzi-infected children. Flow cytometric analysis of co-expression profiles of CD4+T cells with the ability to produce IFN-, TNF-, or to express the co-stimulatory molecule CD154 in response toT. cruzishowed polyfunctional T cell responses in mostT. cruzi-infected children. Monofunctional T cell responses and an absence of CD4+TNF-+-secreting T cells were observed inT. cruzi-infected adults. A relatively high degree of activation and differentiation of CD4+T cells was evident inT. cruzi-infected children. == Conclusions/Significance == Our observations are compatible with our initial hypothesis that persistentT. cruziinfection promotes eventual exhaustion of immune system, which might contribute to disease progression in long-term infected subjects. == Author Summary == Chagas disease is a neglected tropical disease affecting approximately 10 million people in the world. As BAY-598 a consequence of migration flows, the disease has also become established in non-endemic countries. Previous studies have demonstrated thatTrypanosoma cruzi-specific T cells inversely correlates with the severity of cardiac disease in the chronic phase of the infection, suggesting that the immune system becomes exhausted overtime. To test this hypothesis, the quality and magnitude ofT. cruzi-specific T cell responses were measured inT. cruzi-infected children who are presumed to have shorter-term infections – and compared with long-termT. cruzi-infected adults. The activation status of total T cells inT. cruzi-infected children was also evaluated.T. cruzi-infected children exhibit a more robust, and more highly functional parasite specific T cell responses compared toT. cruzi-infected adults. In spite of a more functional immune profile,T. cruzi-infected children have a heightened state of immune activation. These observations are compatible with the initial hypothesis that T cell responses specific forT. cruzibecome exhausted overtime. The impairment in T cell responses might contribute to disease progression in long-term infected subjects. == Introduction == Chagas disease, a neglected tropical disease affecting approximately 10 million people from south of the United States to Mexico and Central and South America[1], is caused by the protozoan parasiteTrypanosoma cruzi. As a consequence of migration flows, the disease has been also become established in non-endemic countries[2]. T. cruzifrequently results in the development of cardiomyopathy, generally many years after the initial infection. Three factors are likely associated with the development of severe disease: parasite burden; the effectiveness of the host immune response in controlling parasites in specific tissues, and the effectiveness of the host immune response in limiting peripheral damage[3],[4]. Chronic infections in general are Bmp3 associated with a progressive loss of pathogen-specific T cell function known as immune exhaustion[5],[6]. We have previously shown that adults with chronicT. cruzi-infections exhibit a prevailing profile of parasite-specific Interferon (IFN)- only secreting T cells[7], associated with long-term antigen persistence and exhausted T cells[5]. The frequencies ofT. cruzi-specific T cells were also found to inversely correlate with the severity of chronic Chagas disease[7],[8]. Although,T. cruzi-infected children are likely to have shorter-term infections than most adults, the overall CD8 T cell compartment in children in the early phase of chronicT. cruziinfection exhibits decreased levels of nave T cells and increased levels of terminally differentiated antigen-experienced T cells[9]. Other studies have suggested thatT. cruzi-infected children have a mixed T cell profile with the production of IFN- and IL-4[10],[11]. However, a comprehensive analysis of the ability ofT. cruzispecific T cells to co-express multiple functions has not been performed. In order to examine the progression of immune exhaustion in chronicT. cruziinfection, we have assessed the quantitative and qualitative attributes BAY-598 ofT. cruzi-specific T cell responses in early stages of Chagas disease in children in comparison toT. cruzi-infected adults. The degree of activation, differentiation and antigen exposure of total CD4+T cells was also evaluated inT. cruzi-infected children. The primary finding is thatT. cruzi-infected children have a higher frequency of polyfunctional and more robust T cell responses specific forT. cruzicompared toT. cruzi-infected adults, and a heightened state of immune activation of CD4+T cells. == Materials and Methods == == Ethics statement BAY-598 == This protocol was approved by the Institutional Review Boards of the Hospital Interzonal General de Agudos Eva Pern, and the Centro Nacional de Gentica, Buenos Aires, Argentina. Informed written consent was obtained from adult subjects and the parents of all children included in this study. == Study subjects == Five to 16-year old children and 29 to 63 year-old adults were enrolled at the Instituto Nacional de Parasitologa Dr. Mario Fatala Chaben and BAY-598 at the Hospital Interzonal General de Agudos Eva Pern, (Buenos Aires, BAY-598 Argentina).T. cruziinfection was determined by indirect immunofluorescence, haemagglutination and ELISA assays[12]. Subjects positive on at least two of these tests were considered to be infected. All infected children were in the early chronic phase ofT. cruziinfection. Age- and sex-matched children with negative serological findings were recruited as uninfected controls.T. cruzi-infected subjects were.