Expressão de IL-15 durante a infecção por Trypanosoma cruzi

Abstract

Yeast two-hybrid assays provide evidences indicating that interleukin 15 (IL-15) are among the host cell proteins with which Trypanosoma cruzi amastins interact during the parasite intracellular development. A role of IL-15 during T. cruzi and Leishmania spp infection have been also suggested from transcriptome analyses of human fibroblasts and mice macrophages infected with T. cruzi and L. major, respectively, which showed a significant increase in the IL-15 mRNA expression compared to uninfected cells. With the aim to validate the yeast two-hybrid (Y2H) result and to investigate the role of IL-15 during T. cruzi infection, we analysed murine peritoneal macrophages infected with T. cruzi and L. amazonensis as well as L6 myoblasts, LLCMK2 cells and H9C2 cells infected with T. cruzi, using ELISA and immunofluorescence assays. ELISA performed with proteins extracts showed increased levels of intacellular IL-15 in infected cells compared to uninfected fibrobalst and macrophages. With the exception of the infection of H9C2 cells, the secreted form of IL-15 was undetectable. In murine macrophages infected by L. amazonensis, IL-15 showed decreased expression in the early hours of the infection. Imunofluorescence analyses showed an uniformed distribution of IL-15 in the cytoplasm and nuclei of uninfected macrophages whereas, in infected cells, IL-15 is predominantly localized in the cytoplasm. Importantly, not only in infected macrophages but also in L6 cells infected with T. cruzi, an interaction of IL-15 with the membrane of amastigotes was observed. A similar polarization of IL-15 next to parasitophorus vacuoles containing amastigotes was observed in macrophages infected with L. amazonensis. Murine macrophages previously stimulated with IL-15 recombinant have enhanced killing capacity of T. cruzi amastigotes, indicating that the roles of secreted IL-15 and the intracellular form of this cytokine may differ during the T. cruzi infection. When macrophages of mice IL-15-/- were infected by T. cruzi, a reduction in the number of amastigote per infected cells and reduction in the percentage of infected cells was observed when compared to the wild type macrophages, further suggetsing a role of the cytoplasmic IL-15 in the viability of the intracellular stage of the parasite.