Purinergic signaling differentially modulates tissue immune response fate in experimental Chagas disease

EBERHARDT, NATALIA; SANMARCO, LILIANA; THEUMER, MARTÍN; GARCÍA, MÓNICA; PONCE, NICOLÁS; AOKI, MARÍA P.

Congreso; Purines 2018; 2018

Background and Objective: Chagas cardiomyopathy, caused by the intracellular parasite Trypanosoma cruzi, constitutes a major public health problem in Latin America due to its prevalence and mortality. Despite the development of life-long immunity, the immune system fails to completely clear the parasites that persist within host tissues. One potential immunosuppressive system that could regulate anti-parasitic immune functions is CD73 ectoenzyme/adenosine (ADO) pathway. We previously reported that transient pharmacological inhibition of CD73 during the early acute phase of murine T. cruzi infection induced microbicidal mechanisms, a reduction in cardiac parasite load and the consequent improvement in chronic cardiomyopathy outcome (Ponce et al. J Immunol, 2016, 197:3). The aim of this study was to characterize the effect of the genetic abrogation of CD73 on the microbicidal immune response in different T. cruzi-target tissues. Methods and Results: To this aim, immune system modulation and its implications in T. cruzi infection response were comparatively studied in heart, liver and visceral adipose tissue (VAT) from CD73 knockout (KO) and C57BL/6 (WT) infected mice (Tulahuen strain trypomastigotes). The kinetics of cardiac macrophage (Ma) subsets showed a predominant inflammatory/M1 (CD86+ CD206-) (p<0.001) subset throughout the acute infection with higher frequencies of IL-12+ and iNOS+ M1 Ma (p<0.05) and augmented cardiac nitric oxide levels (p<0.001) in KO compared to WT mice. Moreover, KO cardiac tissue exhibited increased IFN-γ+ and CD107a+ CD8 T cells frequency (p<0.05) and consequent lower parasite load (9.26± 0.45 AU) compared to WT (453.2±23.1 AU) (n=6; p<0.05) at 21 days post-infection (dpi). Strikingly, KO mice exhibited higher parasitemia compared to WT mice (n=6; p<0.05). Moreover, VAT parasite load was augmented at 21 and 28 dpi (7.83±1.62; 9.11±2.14 AU) in KO compared to WT (0.077±0.013; 0.051±0.006 AU) (n=8; p<0.01), likely due to an increased basal VAT/body weight ratio (0.97±0.07%) compared to WT mice (0.64±0.05%) (n=12; p<0.001), thus generating an important reservoir for parasite growth. Furthermore, no differences were observed in M1 Ma kinetics in VAT. As for liver, parasite burden was augmented in KO (327.5±54.3 AU) compared to WT mice (122.5±10.0 AU) (n=4; p<0.001) at 21 dpi. These findings could be explained by the purinergic signaling differential impact on T. cruzi-target tissues evidenced by the significantly augmented ATP/ADO ratio in KO heart (15.4±4.12) compared to WT (2.83±1.46) (n=5; p<0.01). Likewise, cardiac ATP/ADO ratio was increased compared with liver (3.23±1.11) and VAT (5.63±0.92) in KO mice (n=5; p<0.05).Conclusion: ATP catabolic machinery inhibition generates a unique tissue purinergic milieu that contributed to the modulation of host immune response which modifies parasite-host interaction and, consequently, T. cruzi persistence. Fundings: SECyT-UNC; ANPCyT-FONCyT; CONICET.