Avaliação da frequência de genótipos polimórficos em genes codificadores para FOXP3 e sua associação com as diferentes formas clínicas da Doença de Chagas

Abstract

The identification of the CD4+CD25high FOXP3+ subset and of its role as regulatory T cells (TREG) has been the object of intense studies due to the putative critical role of these cells in maintaining self-tolerance, as well as in defense against infections. The suppressive mechanisms mediated by CD4+CD25high FOXP3+ T regulatory cells are not yet understood. In fact, in vitro studies on the characterization of TREG cells in mice and humans favor the hypothesis that the mechanisms of action these cells depends on cell-cell contact and/or on cytokines. FOXP3 expression by these cells has been described as an important factor for their development and functional activities. Although there are no evidences for a clear function of this cell population in Chagas disease, we have previously demonstrated that the frequency of CD4+CD25high FOXP3+ T cells is augmented in patients with the indeterminate clinical form (IND). Thus, the objective of this study is to investigate the association between FOXP3 gene polymorphisms and the development of severe clinical forms of Chagas disease. In this study, DNA extracted from peripheral blood of patients with the IND and cardiac (CARD) clinical forms of Chagas disease were used to analyze the presence of functional polymorphisms of the FOXP3 gene. Real-time PCR using primers directed to the SNPS -3279 C/T and -3499 G/T, located in the intron-1 of the FOXP3 gene were conducted. In female individuals genotypic and allelic frequencies were associated with different clinical forms of Chagas disease. The study of -3499 G/T polymorphisms showed that heterozygosity of this genotype (GT) was associated with IND patients (p=0,04). Other analyses showed an association between the occurrence of polymorphic allele (T+ -3499 G/T) and the IND clinical form (p=0,016 , OR=0,295), suggesting a protective role for the evaluated polymorphism. This profile is associated with high expression of FOXP3 in TREG. Our results suggest that functional polymorphisms in the FOXP3 gene in TREG cells may have an important role in T. cruzi infection, probably by controlling the exacerbated immune response and consequently controlling morbidity.