Gene related to anergy in lymphocytes (GRAIL) contributes to T cell hyporesponsiveness during the acute phase of Trypanosoma cruzi infection

STEMPIN, CC; ROJAS M, JD; CERBÁN, FM

Mar del Plata

Congreso; LIX Reunión Científica Anual de la Sociedad Argentina de Investigación Clínica, LXII Reunión Científica Anual de la Sociedad Argentina de Inmunología; 2014

Protein ubiquitination mediated by E3 ubiquitin Ligases (E3-Ubi-Lig) has emerged as a crucial mechanism involved in T cell differentiation and induction of immune tolerance. GRAIL, an E3-Ubi-Lig, has been implicated in T cell hyporesponsiveness during infections. Previously we have shown that increased GRAIL mRNA and protein levels in spleen mononuclear cells from T. cruzi infected mice correlated with reduced proliferative response during the acute phase of infection. The aim of this study was to investigate the mechanism involved in GRAIL regulation in T cells during T. cruzi infection. For this purpose, BALB/c mice were infected i.p. with 500 trypomastigotes. Suspensions of spleen CD4 cells were prepared at 15, 21, 28, 36 and 43 dpi and compared to uninfected CD4 cells. GRAIL expression was confirmed by Western blot analysis in CD4 cells with a peak at 21 dpi while is down regulated at 43 dpi. It is known that GRAIL is regulated by otubain 1 (Otub1). CD28 costimulation, IL-2 signaling, and mTOR pathway may regulate Otub1 and GRAIL expression, controlling proliferation in naive CD4 cells. We found that down regulation of GRAIL in CD4 cells from T. cruzi infected mice was related to Otub1 expression and mTOR activation measured by phosphorylation of 4EBP1. In addition, we evaluated IL2 and INF levels in response to unspecific stimulation in CD4 cells from 15 and 43 dpi infected mice. We found that IL2 and INF levels were reduced at the earlier time point compared to stimulated control cells (IL2 P<0.05, INF P<0.001) while cytokine production was restored at 43 dpi. Besides, it has been demonstrated that GRAIL mediates CD3 degradation. We observed reduced CD3 MFI in CD4 T. cruzi infected cells being intensely affected at 21 dpi however it reached comparable levels to control cells at 43 dpi. Therefore, expression of GRAIL during T. cruzi infection may contribute with other mechanisms, to promote the immunosuppression seen during the acute stage of Chagas disease.