Trypanosoma cruzi cysteine protease activity modulates IL-10 production and IL-6 signaling in in vitro-generated Th17 cells

PONCE NE; SANMARCO LM; AOKI MP

Jornada; LXI Reuni¨®n Anual de la Sociedad Argentina de Inmunolog¨ª; 2013

Trypanosoma cruzi cysteine protease activity modulates IL-10 production and IL-6 signaling in in vitro-generated Th17 cellsPonce, Nicol¨¢s Eric; Sanmarco, Liliana Mar¨ªa; Aoki, Mar¨ªa PilarCIBICI-CONICET, Facultad de Ciencias Qu¨ªmicas, Universidad Nacional de C¨®rdoba, C¨®rdoba, Argentina During T. cruzi infection, IL-6 mediates host defense mainly through the activation of the transcription factor STAT3 via gp130, a shared signal-transducing receptor utilized by several IL-6 type cytokines. We have recently reported that cysteine proteases (CP) released by the parasite, abolishes the IL-6/gp130/STAT3 axis in isolated murine cardiac cells. Here, we studied the impact of the inhibition of IL-6 signaling exerted by T. cruzi-secreted CP in splenocytes and in T cells differentiated in vitro into Th17. Murine spleen cells were incubated with conditioned media (CM) obtained from trypomastigote supernatants pre-treated with DTT (CP activator) or with E64 (CP inhibitor) or maintained untreated. We found that CM-DTT completely abrogated IL-6-induced p-STAT3 (p<0.05 vs treated only with IL-6), while untreated CM partially allowed IL-6 signaling. The IL-6/STAT3 pathway inhibition was also observed in spleen cells incubated with native active cruzipain, the major secreted parasitic CP (p<0.01 vs treated only with IL-6), but it was reverted when the enzyme was complexed with its parasite inhibitor. Moreover, when CM-DTT treated cells where subjected to Th17 polarizing conditions (IL-6, TGF-¦Â, anti-IFN-¦Ã and anti-IL-4), we found a significantly reduction in the CD4+IL-17+ cells percentage (p<0.05 vs treated with CM) while untreated CM did not interfere with Th17 cell development. In culture supernatants, the production of IL17 and, strikingly, IL10 raised after cell differentiation toward Th17, but both cytokines decreased under CM-DTT treatment (p <0.05 vs treated with CM). After Th17 cell induction, we did not find IL-10 producing cells compatible with Treg phenotype (CD4+CD25+FOXP3+), but we observed a high rate of CD4+CD25-IL10+ cells. In conclusion, these results suggest a new mechanism of immune evasion exerted by T. cruzi, through which the parasite may modify the Th17 cell development by blocking the IL-6/STAT3 signaling through the modulation of its CP activity.