T cell hyporesponsiveness during Trypanosoma cruzi infection: Gene Related to Anergy in Lymphocytes (GRAIL) a new player.

Congreso; REUNIÓN DE LA SOCIEDAD ARGENTINA DE INMUNOLOGÍA; 2015

Induction of T cell anergy involves E3-ubiquitin-ligases (E3-Ubi-Lig) that degrade signaling mediators. T. cruzi infection induces anergic T cells, however the molecular mechanism is poor understood. We demonstrated GRAIL expression, an E3-Ubi-Lig, in acute stage of infection and a reduced expression of its regulator Otubain 1 (Otub1). CD28 costimulation, IL-2 signaling, and mTOR pathway may regulate Otub1 and GRAIL expression. Therefore, the aim of this study was to deepen the mechanism that regulates GRAIL expression during T. cruzi infection. To do this, BALB/c mice were infected i.p. 500 trypomastigotes and CD4+ cells were purified from spleen of uninfected or infected mice at different times (21 and 42 dpi). First, we measured proliferative response, through CFSE labeling in response to anti-CD3 plus anti-CD28 activation. CD4+ T cells from 21 dpi animals showed lower proliferative response compared to control animals, whereas proliferation in CD4+ cells from 42 dpi tends to be restored. Later, we observed an increase in the percentage of CD4+ cells expressing PD-1 and CTLA-4, but not TIM-3, at 21 dpi. In addition, we found an increase of GRAIL expression in naïve CD4+ cells at 17 dpi. Besides, we found that increased GRAIL expression could be reduced by IL2 addition in CD4+ cells from 17 dpi animals and this match with increased mTOR and Otub1 expression. The results demonstrate that increased inhibitory molecules in acute infection could lead to an anergic state with low IL2 production, maintaining mTOR inactive, not allowing Otub1 traslation, then GRAIL remains expressed and proliferation reduced.