Trypanosoma cruzi persistence in the native heart is associated with high-grade myocarditis, but not with Chagas’ disease reactivation after heart transplantation

Cytokine Networks as Targets for Preventing and Controlling Chagas Heart Disease

Chagas disease, a neglected disease caused by the protozoan Trypanosoma cruzi, is endemic in 21 Latin American countries, affecting 6-8 million people. Increasing numbers of Chagas disease cases have also been reported in non-endemic countries due to migration, contamination via blood transfusions or organ transplantation, characterizing Chagas as an emerging disease in such regions. While most individuals in the chronic phase of Chagas disease remain in an asymptomatic clinical form named indeterminate, approximately 30% of the patients develop a cardiomyopathy that is amongst the deadliest cardiopathies known. The clinical distinctions between the indeterminate and the cardiac clinical forms are associated with different immune responses mediated by innate and adaptive cells. In this review, we present a collection of studies focusing on the human disease, discussing several aspects that demonstrate the association between chemokines, cytokines, and cytotoxic molecules with the distinct clinical outcomes of human infection with Trypanosoma cruzi. In addition, we discuss the role of gene polymorphisms in the transcriptional control of these immunoregulatory molecules. Finally, we discuss the potential application of cytokine expression and gene polymorphisms as markers of susceptibility to developing the severe form of Chagas disease, and as targets for disease control.

Transplantation for chagas' disease: closing the knowledge gap

PURPOSE OF THE REVIEW

This review examines the most recent literature on the epidemiology and treatment of Chagas Disease and the risk of Chagas Disease Reactivation and donor-derived disease in solid organ transplant recipients.

RECENT FINDINGS

Chagas disease is caused by infection with the parasite Trypansoma cruzi . In nonendemic countries the disease is seen primarily in immigrants from Mexico, Central America and South America where the disease is endemic. Benznidazole or nifurtimox can be used for treatment. Posaconazole and fosravuconazole did not provide any additional benefit compared to benznidazole alone or in combination. A phase 2 randomized controlled trial suggests that shorter or reduced dosed regimes of benznidazole could be used. Based on a large randomized controlled trial, benznidazole is unlikely to have a significant preventive effect for established Chagas cardiomyopathy. Transplantation has become the treatment of choice for individuals with refractory Chagas cardiomyopathy. Cohort studies show similar posttransplant outcomes for these patients compared to other indications. Transplant candidates and donors with chronic T. cruzi infection are at risk for Chagas disease reactivation and transmitting infection. Screening them via serology is the first line of prevention. Recipients with chronic infection and those receiving organs from infected donors should undergo sequential monitoring with polymerase chain reaction for early detection of reactivation and preemptive treatment with antitrypanosomal therapy.

SUMMARY

Patients with chronic T. cruzi infection can be safely transplanted and be noncardiac organ donors.

Systemic cytokines, chemokines and growth factors reveal specific and shared immunological characteristics in infectious cardiomyopathies

Heart disease is a major cause of death worldwide. Chronic Chagas cardiomyopathy (CCC) caused by infection with Trypanosoma cruzi leading to high mortality in adults, and rheumatic heart disease (RHD), resulting from infection by Streptococcus pyogenes affecting mainly children and young adults, are amongst the deadliest heart diseases in low-middle income countries. Despite distinct etiology, the pathology associated with both diseases is a consequence of inflammation. Here we compare systemic immune profile in patients with these cardiopathies, to identify particular and common characteristics in these infectious heart diseases. We evaluated the expression of 27 soluble factors, employing single and multivariate analysis combined with machine-learning approaches. We observed that, while RHD and CCC display higher levels of circulating mediators than healthy individuals, CCC is associated with stronger immune activation as compared to RHD. Despite distinct etiologies, univariate analysis showed that expression of TNF, IL-17, IFN-gamma, IL-4, CCL4, CCL3, CXCL8, CCL11, CCL2, PDGF-BB were similar between CCC and RHD, consistent with their inflammatory nature. Network analysis revealed common inflammatory pathways between CCC and RHD, while highlighting the broader reach of the inflammatory response in CCC. The final multivariate model showed a 100% discrimination power for the combination of the cytokines IL-12p70, IL-1Ra, IL-4, and IL-7 between CCC and RHD groups. Thus, while clear immunological distinctions were identified between CCC and RHD, similarities indicate shared inflammatory pathways in these infectious heart diseases. These results contribute to understanding the pathogenesis of CCC and RHD and may impact the design of immune-based therapies for these and other inflammatory cardiopathies that may also share immunological characteristics.

Chagas disease as example of a reemerging parasite

Trypanosoma cruzi, the protozoan that causes Chagas disease, is primarily transmitted by three main Triatomine vectors in endemic areas. However, the infection has become a potential emerging disease because the vector is found in non-endemic areas, there is migration of infected asymptomatic people that can infect the vector, become blood donors, or pass the disease vertically (congenital infections). Lastly, the disease can be acquired through contaminated food (oral transmission). This review will present the different transmission pathways, clinical manifestations, diagnostic modalities and treatment considerations of Chagas disease.

Parasitaemia and parasitic load are limited targets of the aetiological treatment to control the progression of cardiac fibrosis and chronic cardiomyopathy in Trypanosoma cruzi-infected dogs

It is still unclear whether the progression of acute to chronic Chagas cardiomyopathy is predominantly associated with the limited efficacy of aetiological chemotherapy, or with the pharmacological resistance profiles and pathogenicity of specific Trypanosoma cruzi strains. Thus, we tested the hypothesis that parasitic load could be a limited target of aetiological chemotherapy to prevent chronic cardiomyopathy in dogs infected by different T. cruzi strains. Animals were infected with benznidazole-susceptible (Berenice-78) and -resistant (VL-10 and AAS) strains of T. cruzi. A quantitative real-time PCR strategy was developed to comparatively quantify the parasite load of the three different strains using a single standard curve. For dogs infected with the VL-10 strain, benznidazole treatment reduced cardiac parasitism during the acute phase of infection. However, similar parasite load and collagen deposition were detected in the myocardium of treated and untreated animals in the chronic phase of the infection. In animals infected with the AAS strain, benznidazole reduced parasite load, myocarditis and type III collagen deposition in the acute phase. However, increased type III collagen deposition was verified in the chronic phase. Dogs infected with the Berenice-78 strain showed a parasitological cure and no evidence of myocardial fibrosis. Parasitic load and cardiac fibrosis presented no correlation in acute or chronic phases of T. cruzi infection. Our findings in a canine model of Chagas disease suggest that parasite burden is a limited predictor for disease progression after treatment and show that benznidazole, although not inducing parasitological cure, is able to prevent total fibrosis in the early stages of infection, as well as complete prevention of cardiac damage when it eliminates parasites at the onset of infection.

An autopsy-based study of Trypanosoma cruzi persistence in organs of chronic chagasic patients and its relevance for transplantation

BACKGROUND

Chagas' disease (CD) is caused by infection with the protozoan Trypanosoma cruzi. The disease can affect the heart and/or the gastrointestinal (GI) tract, but around 70% of infected individuals remain asymptomatic in the chronic form. Organ transplantation from T. cruzi-infected donors is often avoided because of the risk of disease transmission, previously reported after heart, kidney, or liver transplantation.

METHODS

We investigated by histology, immunohistochemistry, and polymerase chain reaction (PCR) the persistence of T. cruzi in samples of the heart, lung, liver, kidney, pancreas, adrenal gland, esophagus, and GI tract of 21 chronic chagasic patients.

RESULTS

Parasite persistence was detected in 12/21 (57.1%) heart samples, mainly by PCR-based assays. T. cruzi parasites were detected by histology and immunohistochemistry in smooth muscle cells of the central vein from 1/21 (4.8%) adrenal gland samples. No samples of the lung, liver, kidney, pancreas, esophagus, or GI tract were found to have parasites by histology, immunohistochemistry, or PCR.

CONCLUSIONS

We concluded that, aside from the heart, the other solid organs of T. cruzi-infected donors can be used for transplantation with a lot of caution. Such organs are not safe in the view of previous reports of CD transmission, but seem to present a low T. cruzi load compared to the heart.

Biological factors that impinge on Chagas disease drug development

Chagas disease is caused by infection with the insect-transmitted protozoan Trypanosoma cruzi, and is the most important parasitic infection in Latin America. The current drugs, benznidazole and nifurtimox, are characterized by limited efficacy and toxic side-effects, and treatment failures are frequently observed. The urgent need for new therapeutic approaches is being met by a combined effort from the academic and commercial sectors, together with major input from not-for-profit drug development consortia. With the disappointing outcomes of recent clinical trials against chronic Chagas disease, it has become clear that an incomplete understanding of parasite biology and disease pathogenesis is impacting negatively on the development of more effective drugs. In addition, technical issues, including difficulties in establishing parasitological cure in both human patients and animal models, have greatly complicated the assessment of drug efficacy. Here, we outline the major questions that need to be addressed and discuss technical innovations that can be exploited to accelerate the drug development pipeline.

Putting Infection Dynamics at the Heart of Chagas Disease

In chronic Trypanosoma cruzi infections, parasite burden is controlled by effective, but nonsterilising immune responses. Infected cells are difficult to detect because they are scarce and focally distributed in multiple sites. However, advances in detection technologies have established a link between parasite persistence and the pathogenesis of Chagas heart disease. Long-term persistence likely involves episodic reinvasion as well as continuous infection, to an extent that varies between tissues. The primary reservoir sites in humans are not definitively known, but analysis of murine models has identified the gastrointestinal tract. Here, we highlight that quantitative, spatial, and temporal aspects of T. cruzi infection are central to a fuller understanding of the association between persistence, pathogenesis, and immunity, and for optimising treatment.

Pathology of Chronic Chagas Cardiomyopathy in the United States: A Detailed Review of 13 Cardiectomy Cases

OBJECTIVES

The pathologic features of chronic Chagas cardiomyopathy may not be widely appreciated in the United States. We sought to describe the gross, microscopic, immunohistochemical, and molecular pathology features useful to diagnose chronic Chagas cardiomyopathy.

METHODS

The features from a case series of cardiectomy specimens of patients undergoing heart transplantation (12 patients) or mechanical circulatory support device implantation (one patient) for chronic Chagas cardiomyopathy at three institutions in the United States are reported and analyzed.

RESULTS

Gross findings included enlarged and dilated ventricles (100% of cases), mural thrombi (54%), epicardial plaques (42%), and left ventricular aneurysm (36%). Microscopic evaluation revealed myocarditis (100% of cases) characterized by mononuclear cell infiltration, fibrosis (100%), nonnecrotizing granulomas (62%), and giant cells (38%). Two specimens (15%) showed rare intracellular amastigotes. Immunohistochemical assays for Trypanosoma cruzi organisms were negative in all cardiectomy specimens, whereas tissue polymerase chain reaction was positive in six (54%) of 11 cases.

CONCLUSIONS

The gross and microscopic features of chronic Chagas cardiomyopathy in the United States appear similar to those reported in endemic countries. Importantly, tissue polymerase chain reaction may be useful to confirm the diagnosis.

Inhibition of autoimmune Chagas-like heart disease by bone marrow transplantation

BACKGROUND

Infection with the protozoan Trypanosoma cruzi manifests in mammals as Chagas heart disease. The treatment available for chagasic cardiomyopathy is unsatisfactory.

METHODS/PRINCIPAL FINDINGS

To study the disease pathology and its inhibition, we employed a syngeneic chicken model refractory to T. cruzi in which chickens hatched from T. cruzi inoculated eggs retained parasite kDNA (1.4 kb) minicircles. Southern blotting with EcoRI genomic DNA digests revealed main 18 and 20 kb bands by hybridization with a radiolabeled minicircle sequence. Breeding these chickens generated kDNA-mutated F1, F2, and F3 progeny. A targeted-primer TAIL-PCR (tpTAIL-PCR) technique was employed to detect the kDNA integrations. Histocompatible reporter heart grafts were used to detect ongoing inflammatory cardiomyopathy in kDNA-mutated chickens. Fluorochromes were used to label bone marrow CD3+, CD28+, and CD45+ precursors of the thymus-dependent CD8α+ and CD8β+ effector cells that expressed TCRγδ, vβ1 and vβ2 receptors, which infiltrated the adult hearts and the reporter heart grafts.

CONCLUSIONS/SIGNIFICANCE

Genome modifications in kDNA-mutated chickens can be associated with disruption of immune tolerance to compatible heart grafts and with rejection of the adult host's heart and reporter graft, as well as tissue destruction by effector lymphocytes. Autoimmune heart rejection was largely observed in chickens with kDNA mutations in retrotransposons and in coding genes with roles in cell structure, metabolism, growth, and differentiation. Moreover, killing the sick kDNA-mutated bone marrow cells with cytostatic and anti-folate drugs and transplanting healthy marrow cells inhibited heart rejection. We report here for the first time that healthy bone marrow cells inhibited heart pathology in kDNA+ chickens and thus prevented the genetically driven clinical manifestations of the disease.