Experimental chemotherapy against Trypanosoma cruzi infection: essential role of endogenous interferon-gamma in mediating parasitologic cure

Benznidazole, a drug used in Chagas' disease, ameliorates LPS-induced inflammatory response in mice

Benznidazole (BZL) is a drug currently used for treating Chagas' disease. Given our earlier demonstration in which BZL downregulated cytokine and nitric oxide (NO) synthesis by LPS and/or IFN-gamma-stimulated murine macrophages, we have now analysed whether this compound could exert beneficial effects in a model of LPS-induced inflammation in C57BL/6 mice. The lethal model consisted of two LPS intraperitoneal injections, 200 microg each separated by 2 h, with BZL given orally at a dose of 200 mg/kg, 18 and 2 h before the first challenge and 20 and 44 hr following the second one. In this model, BZL treatment led to a significantly decreased mortality in comparison with untreated counterparts. Remaining experiments were carried out in mice given a unique LPS dose, pretreated with BZL or not, since those subjected to the lethal protocol were unsuitable for laboratory handling. Analysis of IL-1beta, IL-6, TNF-alpha, IL-12 and iNOS mRNA expression in liver samples taken at 90 min post-LPS showed a marked reduction of the two latter mRNAs in BZL-treated mice. These animals also displayed significantly decreased peaks levels of serum TNF-alpha and IL-6, accompanied by a diminished number of IL-6-producing peritoneal macrophages. Present effects may broaden the potential usefulness of BZL in situations accompanied by an excessive inflammatory response.

Impaired Production of Proinflammatory Cytokines and Host Resistance to Acute Infection withTrypanosoma cruziin Mice Lacking Functional Myeloid Differentiation Factor 88

Studies performed in vitro suggest that activation of Toll-like receptors (TLRs) by parasite-derived molecules may initiate inflammatory responses and host innate defense mechanisms against Trypanosoma cruzi. Here, we evaluated the impact of TLR2 and myeloid differentiation factor 88 (MyD88) deficiencies in host resistance to infection with T. cruzi. Our results show that macrophages derived from TLR2 (-/-) and MyD88(-/-) mice are less responsive to GPI-mucin derived from T. cruzi trypomastigotes and parasites. In contrast, the same cells from TLR2(-/-) still produce TNF-alpha, IL-12, and reactive nitrogen intermediates (RNI) upon exposure to live T. cruzi trypomastigotes. Consistently, we show that TLR2(-/-) mice mount a robust proinflammatory cytokine response as well as RNI production during the acute phase of infection with T. cruzi parasites. Further, deletion of the functional TLR2 gene had no major impact on parasitemia nor on mortality. In contrast, the MyD88(-/-) mice had a diminished cytokine response and RNI production upon acute infection with T. cruzi. More importantly, we show that MyD88(-/-) mice are more susceptible to infection with T. cruzi as indicated by the higher parasitemia and accelerated mortality, as compared with the wild-type mice. Together, our results indicate that T. cruzi parasites elicit an alternative inflammatory pathway independent of TLR2. This pathway is partially dependent on MyD88 and necessary for mounting optimal inflammatory and RNI responses that control T. cruzi replication during the early stages of infection.

Absence of Interferon-γ–Inducible Gene IGTP Does Not Significantly Alter the Development of Chagasic Cardiomyopathy in Mice Infected with Trypanosoma cruzi (Brazil Strain)

Interferon-gamma (IFN-gamma) contributes to host resistance during acute infection with Trypanosoma cruzi, the causative agent of Chagas' disease. Inducibly expressed guanosine triphosphatase (IGTP), a 48-kDa guanosine triphosphatase (GTPase), is a member of a family of GTPase proteins inducibly expressed by IFN-gamma. The expression pattern of IGTP suggests that it may mediate IFN-gamma-induced responses in a variety of cell types. IGTP has been demonstrated to be important for control of Toxoplasma gondii infection but not for resistance against Listeria monocytogenes. We evaluated the role of IGTP in development of chronic chagasic cardiomyopathy in IGTP null mice and C57X129sv (wild type [WT]) mice infected with the Brazil strain for 6 mo. There was no significant difference in parasitemia or cardiac histopathology between null and WT mice. Right ventricular remodeling was observed in infected IGTP null mice, suggesting that IGTP does not significantly alter the course of T. cruzi infection.