New insights into Trypanosoma cruzi genetic diversity, and its influence on parasite biology and clinical outcomes

Chagas disease, caused by Trypanosoma cruzi, remains a serious public health problem worldwide. The parasite was subdivided into six distinct genetic groups, called "discrete typing units" (DTUs), from TcI to TcVI. Several studies have indicated that the heterogeneity of T. cruzi species directly affects the diversity of clinical manifestations of Chagas disease, control, diagnosis performance, and susceptibility to treatment. Thus, this review aims to describe how T. cruzi genetic diversity influences the biology of the parasite and/or clinical parameters in humans. Regarding the geographic dispersion of T. cruzi, evident differences were observed in the distribution of DTUs in distinct areas. For example, TcII is the main DTU detected in Brazilian patients from the central and southeastern regions, where there are also registers of TcVI as a secondary T. cruzi DTU. An important aspect observed in previous studies is that the genetic variability of T. cruzi can impact parasite infectivity, reproduction, and differentiation in the vectors. It has been proposed that T. cruzi DTU influences the host immune response and affects disease progression. Genetic aspects of the parasite play an important role in determining which host tissues will be infected, thus heavily influencing Chagas disease's pathogenesis. Several teams have investigated the correlation between T. cruzi DTU and the reactivation of Chagas disease. In agreement with these data, it is reasonable to suppose that the immunological condition of the patient, whether or not associated with the reactivation of the T. cruzi infection and the parasite strain, may have an important role in the pathogenesis of Chagas disease. In this context, understanding the genetics of T. cruzi and its biological and clinical implications will provide new knowledge that may contribute to additional strategies in the diagnosis and clinical outcome follow-up of patients with Chagas disease, in addition to the reactivation of immunocompromised patients infected with T. cruzi.

Chagas disease stroke and associated risk factors: A case-control study

INTRODUCTION

The intricate relationship between Chagas disease and ischemic stroke remains unclear. Limited evidence exists concerning secondary prophylaxis, etiological diagnosis, and stroke-related determinants. This study aims to discern factors linked to stroke in Chagas disease by contrasting patients with and without a history of ischemic stroke.

METHODS

Retrospective data from all outpatient Chagas disease patients from two Brazilian hospitals - one Chagas center and one stroke clinic - were examined. Descriptive analyses were conducted to identify stroke-associated factors. Variables were compared between patients with and without ischemic stroke history.

RESULTS

Among 678 subjects, 72 had experienced stroke. Univariate associations with stroke included male gender, heart failure, prior or ongoing alcoholism, electrocardiographic features (non-sinus rhythm, left bundle branch, right bundle branch block, left anterosuperior fascicular block, atrial fibrillation), as well as echocardiographic findings indicative of reduced left ventricular ejection fraction and segmental abnormalities. After logistic regression (multivariate analysis), congestive heart failure, right bundle branch block, left anterosuperior divisional block, and atrial fibrillation retained independent associations.

CONCLUSION

In this study, cardiac involvement emerged as the predominant factor correlated with stroke in Chagas disease. While atherosclerosis-related risk factors were prevalent, their influence on ischemic stroke in Chagas disease appeared limited.

The economic burden of Chagas disease: A systematic review

BACKGROUND

Chagas disease (CD) is a neglected disease affecting millions worldwide, yet little is known about its economic burden. This systematic review is part of RAISE project, a broader study that aims to estimate the global prevalence, mortality, and health and economic burden attributable to chronic CD and Chronic Chagas cardiomyopathy. The objective of this study was to assess the main costs associated with the treatment of CD in both endemic and non-endemic countries.

METHODS

An electronic search of the Medline, Lilacs, and Embase databases was conducted until 31st, 2022, to identify and select economic studies that evaluated treatment costs of CD. No restrictions on place or language were made. Complete or partial economic analyses were included.

RESULTS

Fifteen studies were included, with two-thirds referring to endemic countries. The most commonly investigated cost components were inpatient care, exams, surgeries, consultation, drugs, and pacemakers. However, significant heterogeneity in the estimation methods and presentation of data was observed, highlighting the absence of standardization in the measurement methods and cost components. The most common component analyzed using the same metric was hospitalization. The mean annual hospital cost per patient ranges from $25.47 purchasing power parity US dollars (PPP-USD) to $18,823.74 PPP-USD, and the median value was $324.44 PPP-USD. The lifetime hospital cost per patient varies from $209,44 PPP-USD for general care to $14,351.68 PPP-USD for patients with heart failure.

DISCUSSION

Despite the limitations of the included studies, this study is the first systematic review of the costs of CD treatment. The findings underscore the importance of standardizing the measurement methods and cost components for estimating the economic burden of CD and improving the comparability of cost components magnitude and cost composition analysis. Finally, assessing the economic burden is essential for public policies designed to eliminate CD, given the continued neglect of this disease.

Parasite Metalo-aminopeptidases as Targets in Human Infectious Diseases

BACKGROUND

Parasitic human infectious diseases are a worldwide health problem due to the increased resistance to conventional drugs. For this reason, the identification of novel molecular targets and the discovery of new chemotherapeutic agents are urgently required. Metalo- aminopeptidases are promising targets in parasitic infections. They participate in crucial processes for parasite growth and pathogenesis.

OBJECTIVE

In this review, we describe the structural, functional and kinetic properties, and inhibitors, of several parasite metalo-aminopeptidases, for their use as targets in parasitic diseases.

CONCLUSION

Plasmodium falciparum M1 and M17 aminopeptidases are essential enzymes for parasite development, and M18 aminopeptidase could be involved in hemoglobin digestion and erythrocyte invasion and egression. Trypanosoma cruzi, T. brucei and Leishmania major acidic M17 aminopeptidases can play a nutritional role. T. brucei basic M17 aminopeptidase down-regulation delays the cytokinesis. The inhibition of Leishmania basic M17 aminopeptidase could affect parasite viability. L. donovani methionyl aminopeptidase inhibition prevents apoptosis but not the parasite death. Decrease in Acanthamoeba castellanii M17 aminopeptidase activity produces cell wall structural modifications and encystation inhibition. Inhibition of Babesia bovis growth is probably related to the inhibition of the parasite M17 aminopeptidase, probably involved in host hemoglobin degradation. Schistosoma mansoni M17 aminopeptidases inhibition may affect parasite development, since they could participate in hemoglobin degradation, surface membrane remodeling and eggs hatching. Toxoplasma gondii M17 aminopeptidase inhibition could attenuate parasite virulence, since it is apparently involved in the hydrolysis of cathepsin Cs- or proteasome-produced dipeptides and/or cell attachment/invasion processes. These data are relevant to validate these enzymes as targets.

New antiparasitic derivatives of the furoquinoline alkaloids kokusaginine and flindersiamine

In this work is reported the synthesis of 16 new compounds obtained from kokusaginine and flindersiamine, the main alkaloids isolated from the bark of Balfourodendron riedelianum . The activity of the compounds against axenic cultures of Trypanosoma cruzi epimastigtotes and trypomastigotes, as well as intracellular amastigotes, is described, together with their cytotoxic activity against three different human cell lines. The synthetic strategy for the preparation of the new compounds was based on the reactivity at the position C-4 of the furoquinoline core towards nucleophiles. The new derivatives were synthesized by a Buchwald-Hartwig reaction, in most cases under green, solvent free conditions. Compounds 1c and 1e displayed better in-vitro activity against trypomastigotes than benznidazole and nifurtimox (positive controls) with IC 50 < 4 µM. In addition, both compounds were not cytotoxic activity against the three human cell lines K562 (erytroleukimia), LM2 (breast cancer) and HaCat (keratinocyte). Interestingly, when evaluated against intracellular amastigotes, compound 1c was able to significantly reduce the number of this parasite form, compared to the negative control.

Differential tissue distribution of discrete typing units after drug combination therapy in experimental Trypanosoma cruzi mixed infection

The aim of the present work was to evaluate the distribution of the different clones of the parasite prevailing after treatment with benznidazole (BZ) and clomipramine (CLO), in mice infected with Trypanosoma cruzi, Casibla isolate which consists of a mixture of two discrete typing units (DTUs). Albino Swiss mice were infected and treated with high and low concentrations of BZ (100 or 6.25 mg/kg), CLO (5 or 1.25 mg/kg), or the combination of both low doses (BZ6.25 + CLO1.25), during the acute phase of experimental infection. Treatment efficacy was evaluated by comparing parasitaemia, survival and tissular parasite presence. For DTUs genotyping, blood, skeletal and cardiac muscle samples were analysed by multiplex quantitative polymerase chain reaction. The combined treatment had similar outcomes to BZ6.25; BZ100 was the most effective treatment, but it failed to reach parasite clearance and produced greater histological alterations. Non-treated mice and the ones treated with monotherapies showed both DTUs while BZ6.25 + CLO1.25 treated mice showed only TcVI parasites in all the tissues studied. These findings suggest that the treatment may modify the distribution of infecting DTUs in host tissues. Coinfection with T. cruzi clones belonging to different DTUs reveals a complex scenario for the treatment of Chagas disease and search for new therapies.

Planning new Trypanosoma cruzi CYP51 inhibitors using QSAR studies

Chagas disease kills over 10,000 people per year, and approximately 8 million people are infected by Trypanosoma cruzi. The reference drug for treatment of the disease, benznidazole, is the same since the 70s. In recent years, many CYP51 inhibitors were tested against this parasite's target. One of them, posaconazole, was even tested in clinical trials that unfortunately were not successful. Nevertheless, there are still many evidences that CYP51 is a great potential target to treat T. cruzi infection. The research for new effective molecules that can cure the chronic phase of the disease is essential. 2D and 3D-quantitative structure activity relationship (QSAR) studies were conducted in this work to create three QSAR models using the chemical structures of 197 published compounds that already went through either in vivo or in vitro tests. After the analysis of the models, new analogues not yet synthesized were suggested here and had their biological activity and synthetic availability assessed.

Targeting L-Proline Uptake as New Strategy for Anti-chagas Drug Development

L-Proline is an important amino acid for the pathogenic protists belonging to Trypanosoma and Leishmania genera. In Trypanosoma cruzi, the etiological agent of Chagas disease, this amino acid is involved in fundamental biological processes such as ATP production, differentiation of the insect and intracellular stages, the host cell infection and the resistance to a variety of stresses. In this study, we explore the L-Proline uptake as a chemotherapeutic target for T. cruzi. Novel inhibitors have been proposed containing the amino acid with a linker and a variable region able to block the transporter. A series of sixteen 1,2,3-triazolyl-proline derivatives have been prepared for in vitro screening against T. cruzi epimastigotes and proline uptake assays. We successfully obtained inhibitors that interfere with the amino acid internalization, which validated our design targeting the metabolite's transport. The presented structures are one of few examples of amino acid transporter inhibitors. The unprecedent application of this strategy on the development of new chemotherapy against Chagas disease, opens a new horizon on antiparasitic drug development against parasitic diseases and other pathologies.

Animal models of Chagas disease and their translational value to drug development

INTRODUCTION

American trypanosomiasis, better known as Chagas disease, is a global public health issue. Current treatments targeting the causative parasite, Trypanosoma cruzi, are limited to two old nitroheterocyclic compounds; new, safer drugs are needed. New tools to identify compounds suitable for parasitological cure in humans have emerged through efforts in drug discovery.

AREAS COVERED

Animal disease models are an integral part of the drug discovery process. There are numerous experimental models of Chagas disease described and in use; rather than going through each of these and their specific features, the authors focus on developments in recent years, in particular the imaging technologies that have dramatically changed the Chagas R&D landscape, and provide a critical view on their value and limitations for moving compounds forward into further development.

EXPERT OPINION

The application of new technological advances to the field of drug development for Chagas disease has led to the implementation of new and robust/standardized in vivo models that contributed to a better understanding of host/parasite interactions. These new models should also build confidence in their translational value for moving compounds forward into clinical development.

Development of a High-Throughput Screening Assay to Identify Inhibitors of the Major M17-Leucyl Aminopeptidase from Trypanosoma cruzi Using RapidFire Mass Spectrometry

Leucyl aminopeptidases (LAPs) are involved in multiple cellular functions, which, in the case of infectious diseases, includes participation in the pathogen-host cell interface and pathogenesis. Thus, LAPs are considered good candidate drug targets, and the major M17-LAP from Trypanosoma cruzi (LAPTc) in particular is a promising target for Chagas disease. To exploit LAPTc as a potential target, it is essential to develop potent and selective inhibitors. To achieve this, we report a high-throughput screening method for LAPTc. Two methods were developed and optimized: a Leu-7-amido-4-methylcoumarin-based fluorogenic assay and a RapidFire mass spectrometry (RapidFire MS)-based assay using the LSTVIVR peptide as substrate. Compared with a fluorescence assay, the major advantages of the RapidFire MS assay are a greater signal-to-noise ratio as well as decreased consumption of enzyme. RapidFire MS was validated with the broad-spectrum LAP inhibitors bestatin (IC₅₀ = 0.35 μM) and arphamenine A (IC₅₀ = 15.75 μM). We suggest that RapidFire MS is highly suitable for screening for specific LAPTc inhibitors.

Efficacy of the Benznidazole+Posaconazole combination therapy in parasitemia reduction: An experimental murine model of acute Chagas

INTRODUCTION:

Benznidazole (BZL) and Nifurtimox (NFX) are the pharmacological treatment for acute phase Chagas Disease (CD); however, therapy resistance and residual mortality development remain important unresolved issues. Posaconazole (POS) has shown a trypanocidal effect in vivo and in vitro. Thus, this study aimed at comparing the T. Cruzi parasitic load-reducing effect of the combination of BZL+POS against that of monotherapy with either, during acute phase CD, in an experimental murine model.

METHODS

Nineteen Wistar rats were randomly allocated to four groups and inoculated with the trypomastigotes of T. cruzi strain´s JChVcl1. The rats were administered anti-parasites from day 20-29 post-infection. The Pizzi and Brener method was used for parasitemia measurement. Longitudinal data analysis for the continuous outcome of repeated measures was performed using parasitemia as the outcome measured at days 20, 22, 24, 27, and 29 post-infection.

RESULTS

All four groups had similar parasitic loads (p=0.143) prior to therapy initiation. Among the three treatment groups, the BZL+POS (n=5) group showed the highest mean parasitic load reduction (p=0.000) compared with the control group. Likewise, the BZL+POS group rats showed an earlier therapeutic effect and were the only ones without parasites in their myocardial samples.

CONCLUSIONS:

Treatment of acute phase CD with BZL+POS was more efficacious at parasitemia and myocardial injury reduction, compared with monotherapy with either.

Usefulness of real-time PCR during follow-up of patients treated with Benznidazole for chronic Chagas disease: Experience in two referral centers in Barcelona

BACKGROUND

Antitrypanosomal treatment with Benznidazole (BZ) or Nifurtimox may be recommended for patients with chronic Chagas disease (CD) to reduce the onset or progression of symptoms. However, such treatment has limited efficacy and high level of toxic effects. In addition, the current cure biomarker (serology conversion) precludes any treatment assessment unless a prolonged follow-up is arranged. PCR is thus the most useful, alternative surrogate marker for evaluating responses to treatment. The aim of this study is to describe the usefulness of real-time PCR in monitoring BZ treatment within a large cohort of chronic CD cases in Barcelona.

METHODOLOGY/PRINCIPAL FINDINGS

A total of 370 chronic CD patients were monitored with real-time PCR post-BZ treatment. The median follow-up was 4 years (IQR 2.2-5.3y), with a median of 3 clinical visits (IQR 2-4). Only 8 patients (2.2%) presented with at least one incident of positive real-time PCR after treatment and were therefore considered as treatment failure. Four of those failure patients had completed full course treatment, whereas the remaining cases had defaulted with a statistical difference between both groups (p = 0.02). Half of the failure patients had undergone less than 4 years of follow-up monitoring all presented with parasitemia before treatment.

CONCLUSIONS/SIGNIFICANCE

BZ treatment failure was highly infrequent in our cohort. BZ discontinuation was a risk factor for positive real-time PCR results during clinical follow-up. Regular testing with real-time PCR during follow-up allows for early detection of treatment failure in patients with chronic CD.

An evaluation of benznidazole as a Chagas disease therapeutic

Introduction: As benznidazole is the first-line treatment for patients with Chagas disease, rational chemotherapy strategies are required based on the critical analysis of the evidence on the relevance and applicability of this drug at different disease stages. Areas covered: The authors discuss the current understanding of benznidazole-based chemotherapy for Chagas disease, focusing specifically on epidemiology, pharmacokinetics, mechanism of action, clinical recommendations, cure criteria, and therapeutic efficacy in different phases of the disease. Expert opinion: Benznidazole shows high bioavailability after oral administration. Benznidazole at 5-8 mg/kg/day and 5-10 mg/kg/day for 30-60 days are consistent clinical recommendations for children and adults, respectively. A high correlation between negative parasitological, serological, and polymerase chain reaction (PCR) assays in long-term post-therapeutic follow-up has been consistently used to evaluate therapeutic efficacy. These methods support the evidence that the success of benznidazole-based chemotherapy is closely correlated with the phase of infection in which the treatment is administered. The greater therapeutic efficacy is obtained in acute infections, gradually worsening as the infection becomes chronic. When therapeutic failure is confirmed by any diagnostic assay, benznidazole treatment does not always ensure better long-term prognosis, and Chagas cardiomyopathy may develop as well as in untreated patients.

Heterobimetallic nickel(II) and palladium(II) complexes derived from S-benzyl-N- (ferrocenyl)methylenedithiocarbazate: Trypanocidal activity and interaction with Trypanosoma cruzi Old Yellow Enzyme (TcOYE)

Reactions of Ni(II) and Pd(II) precursors with S-benzyl-N-(ferrocenyl)methylenedithiocarbazate (HFedtc) led to the formation of heterobimetallic complexes of the type [M^II(Fedtc)₂] (M = Ni and Pd). The characterization of the compounds involved the determination of melting point, FTIR, UV-Vis, ¹H NMR, elemental analysis and electrochemical experiments. Furthermore, the crystalline structures of HFedtc and [Ni^II(Fedtc)₂] were determined by single crystal X-ray diffraction. The compounds were evaluated against the intracellular form of Trypanosoma cruzi (Tulahuen Lac-Z strain) and the cytotoxicity assays were assessed using LLC-MK2 cells. The results showed that the coordination of HFedtc to Ni(II) or Pd(II) decreases the in vitro trypanocidal activity while the cytotoxicity against LLC-MK2 cells does not change significantly. [Pd^II(Fedtc)₂] showed the greater potential between the two complexes studied, showing an SI value of 8.9. However, this value is not better than that of the free ligand with an SI of 40, a similar value to that of the standard drug benznidazole (SI = 48). Additionally, molecular docking simulations were performed with Trypanosoma cruzi Old Yellow Enzyme (TcOYE), which predicted that HFedtc binds to the protein, almost parallel to the flavin mononucleotide (FMN) prosthetic group, while the [Ni^II(Fedtc)₂] complex was docked into the enzyme binding site in a significantly different manner. In order to confirm the hypothetical interaction, in vitro experiments of fluorescence quenching and enzymatic activity were performed which indicated that, although HFedtc was not processed by the enzyme, it was able to act as a competitive inhibitor, blocking the hydride transfer from the FMN prosthetic group of the enzyme to the menadione substrate.

Appraisal of anti-protozoan activity of nitroaromatic benzenesulfonamides inhibiting carbonic anhydrases from Trypanosoma cruzi and Leishmania donovani

Chagas disease and leishmaniasis are neglected tropical disorders caused by the protozoans Trypanosoma cruzi and Leishmania spp. Carbonic anhydrases (CAs, EC 4.2.1.1) from these protozoans (α-TcCA and β-LdcCA) have been validated as promising targets for chemotherapic interventions. Many anti-protozoan agents, such as nitroimidazoles, nifurtimox, and benznidazole possess a nitro aromatic group in their structure which is crucial for their activity. As a continuation of our previous work on N-nitrosulfonamides as anti-protozoan agents, we investigated benzenesulfonamides bearing a nitro aromatic moiety against TcCA and LdcCA, observing selective inhibitions over human off-target CAs. Selected derivatives were assessed in vitro in different developmental stages of T. cruzi and Leishmania spp. A lack of significant growth inhibition has been found, which has been connected to the low permeability of this class of derivatives through cell membranes. Further strategies necessarily need to be designed for targeting Chagas disease and leishmaniasis with nitro-containing CA inhibitors.

N-Nitrosulfonamides as Carbonic Anhydrase Inhibitors: A Promising Chemotype for Targeting Chagas Disease and Leishmaniasis

Trypanosoma cruzi and Leishmania spp. are protozoa of the Trypanosomatidae family, respectively, responsible of the neglected tropical disorders (NTDs) Chagas disease and leishmaniasis. The present pharmacotherapy is often ineffective and exhibits serious side effects. The metalloenzyme carbonic anhydrases (CAs, EC 4.2.1.1) recently identified in these protozoans (α-TcCA and β-LdcCA) are novel promising targets for chemotherapeutic interventions. Herein, we report a series of N-nitrosulfonamides, as a novel chemotype to yield the target CA isoform selective inhibition over ubiquitous human isozymes. Two derivatives selected among the most active and selective ones for TcCA/LdcCA over off-target CAs were progressed as silver salts to in vitro studies with various developmental forms and spp of Trypanosoma cruzi and leishmania. Excellent values of parasites growth inhibition (IC₅₀) were observed, with some selectivity index (over cytotoxicity for macrophages and Vero cells) being comparable or better than reference drugs. These findings make N-nitrosulfonamides and their salts promising lead compounds for a rational optimization of innovative agents for the treatment of Chagas disease and leishmaniasis based on CA inhibition.

The economic value of identifying and treating Chagas disease patients earlier and the impact on Trypanosoma cruzi transmission

BACKGROUND

The World Health Organization's 2020 Goals for Chagas disease include access to antiparasitic treatment and care of all infected/ill patients. Policy makers need to know the economic value of identifying and treating patients earlier. However, the economic value of earlier treatment to cure and prevent the Chagas' spread remains unknown.

METHODS

We expanded our existing Chagas disease transmission model to include identification and treatment of Chagas disease patients. We linked this to a clinical and economic model that translated chronic Chagas disease cases into health and economic outcomes. We evaluated the impact and economic outcomes (costs, cost-effectiveness, cost-benefit) of identifying and treating different percentages of patients in the acute and indeterminate disease states in a 2,000-person village in Yucatan, Mexico.

RESULTS

In the absence of early treatment, 50 acute and 22 new chronic cases occurred over 50 years. Identifying and treating patients in the acute stage averted 0.5-5.4 acute cases, 0.6-5.5 chronic cases, and 0.6-10.8 disability-adjusted life years (DALYs), saving $694-$7,419 and $6,976-$79,950 from the third-party payer and societal perspectives, respectively. Treating in the indeterminate stage averted 2.2-4.9 acute cases, 6.1-12.8 chronic cases, and 11.7-31.1 DALYs, saving $7,666-$21,938 from the third-party payer perspective and $90,530-$243,068 from the societal perspective. Treating patients in both stages averted ≤9 acute cases and ≤15 chronic cases. Identifying and treating patients early was always economically dominant compared to no treatment. Identifying and treating patients earlier resulted in a cumulative cost-benefit of $7,273-$224,981 at the current cost of identification and treatment.

CONCLUSIONS

Even when identifying and treating as little as 5% of cases annually, treating Chagas cases in the acute and indeterminate stages reduces transmission and provides economic and health benefits. This supports the need for improved diagnostics and access to safe and effective treatment.

Relevance of Trypanothione Reductase Inhibitors on Trypanosoma cruzi Infection: A Systematic Review, Meta-Analysis, and In Silico Integrated Approach

Due to the rudimentary antioxidant defenses in Trypanosoma cruzi, disruptors of redox balance are promising candidates for new antitrypanosomal drugs. We developed an integrated model based on systematic review, meta-analyses, and molecular modeling to evaluate the effect of trypanothione reductase (TR) inhibitors in T. cruzi infections. Our findings indicated that the TR inhibitors analyzed were effective in reducing parasitemia and mortality due to Trypanosoma cruzi infection in animal models. The most investigated drugs (clomipramine and thioridazine) showed no beneficial effects on the occurrence of infection-related electrocardiographic abnormalities or the affinity and density of cardiac β-adrenergic receptors. The affinity between the tested ligands and the active site of TR was confirmed by molecular docking. However, the molecular affinity score was unable to explain TR inhibition and T. cruzi death in vitro or the antiparasitic potential of these drugs when tested in preclinical models of T. cruzi infection. The divergence of in silico, in vitro, and in vivo findings indicated that the anti-T. cruzi effects of the analyzed drugs were not restricted to TR inhibition. As in vivo studies on TR inhibitors are still scarce and exhibit methodological limitations, mechanistic and highly controlled studies are required to improve the quality of evidence.

Pathology and Pathogenesis of Chagas Heart Disease

Chagas heart disease is an inflammatory cardiomyopathy that develops in approximately one-third of people infected with the protozoan parasite Trypanosoma cruzi. One way T. cruzi is transmitted to people is through contact with infected kissing bugs, which are found in much of the Western Hemisphere, including in vast areas of the United States. The epidemiology of T. cruzi and Chagas heart disease and the varied mechanisms leading to myocyte destruction, mononuclear cell infiltration, fibrosis, and edema in the heart have been extensively studied by hundreds of scientists for more than 100 years. Despite this wealth of knowledge, it is still impossible to predict what will happen in an individual infected with T. cruzi because of the tremendous variability in clonal parasite virulence and human susceptibility to infection and the lack of definitive molecular predictors of outcome from either side of the host-parasite equation. Further, while several distinct mechanisms of pathogenesis have been studied in isolation, it is certain that multiple coincident mechanisms combine to determine the ultimate outcome. For these reasons, Chagas disease is best considered a collection of related but distinct illnesses. This review highlights the pathology and pathogenesis of the most common adverse sequela of T. cruzi infection-Chagas heart disease-and concludes with a discussion of key unanswered questions and a view to the future.

Experimental models in Chagas disease: a review of the methodologies applied for screening compounds against Trypanosoma cruzi

One of the main problems of Chagas disease (CD), the parasitic infection caused by Trypanosoma cruzi, is the lack of a completely satisfactory treatment, which is currently based on two old nitroheterocyclic drugs (i.e., nifurtimox and benznidazole) that show important limitations for treating patients. In this context, many laboratories look for alternative therapies potentially applicable to the treatment, and therefore, research in CD chemotherapy works in the design of experimental protocols for detecting molecules with activity against T. cruzi. Phenotypic assays are considered the most valuable strategy for screening these antiparasitic compounds. Among them, in vitro experiments are the first step to test potential anti-T. cruzi drugs directly on the different parasite forms (i.e., epimastigotes, trypomastigotes, and amastigotes) and to detect cytotoxicity. Once the putative trypanocidal drug has been identified in vitro, it must be moved to in vivo models of T. cruzi infection, to explore (i) acute toxicity, (ii) efficacy during the acute infection, and (iii) efficacy in the chronic disease. Moreover, in silico approaches for predicting activity have emerged as a supporting tool for drug screening procedures. Accordingly, this work reviews those in vitro, in vivo, and in silico methods that have been routinely applied during the last decades, aiming to discover trypanocidal compounds that contribute to developing more effective CD treatments.

Medicinal fungi: a source of antiparasitic secondary metabolites

Regions with a tropical climate are frequently affected by endemic diseases caused by pathogenic parasites. More than one billion people worldwide are exposed directly to tropical parasites. The literature cites several antiparasitic metabolites obtained from medicinal plants or via synthetic pathways. However, fungi produce a diversity of metabolites that play important biological roles in human well-being. Thus, they are considered a potential source of novel natural agents for exploitation in the pharmaceutical industry. In this brief review article, we will provide an overview of the current situation regarding antiparasitic molecules derived from filamentous fungi, in particular, those which are effective against protozoan parasites, such as Plasmodium, Trypanosoma, and Leishmania, vectors of some neglected tropical diseases. Diseases and parasitic agents are described and classified, and the antiparasitic properties of natural compounds produced by the fungi of the phyla Basidiomycota and Ascomycota are reviewed herein, in order to explore a topic only sparsely addressed in the scientific literature.

Benznidazole treatment safety: the Médecins Sans Frontières experience in a large cohort of Bolivian patients with Chagas' disease

Background

Up to half of patients with Chagas' disease under benznidazole treatment present adverse drug reactions (ADRs) and up to one-third do not complete standard treatment.

Objectives

To verify the incidence and possible factors associated with the suspension of benznidazole treatment in a large cohort of patients.

Methods

We included 2075 patients treated with benznidazole during the projects managed by the medical humanitarian organization Doctors Without Borders (Médecins Sans Frontières) in Bolivia from 2009 to 2013. Benznidazole treatment was provided two or three times per day for ∼60 days at 5-7.5 mg/kg/day. A multiple logistic regression model was developed to evaluate the factors associated with permanent suspension of benznidazole treatment.

Results

Permanent benznidazole treatment suspension occurred in 211 patients (10.2%) and the average time until permanent treatment suspension was 23 days. Multifactorial analysis revealed that female sex (adjusted OR = 1.70), moderate ADRs (adjusted OR = 10.57), mild ADRs (adjusted OR = 1.69) and skin disorders (adjusted OR = 4.18) were significantly associated with the permanent suspension of benznidazole treatment. Women with mild or moderate skin ADRs presented a probability of treatment interruption of 18.6% and 59.0%, respectively.

Conclusions

Benznidazole treatment was safe and a large proportion of patients were able to complete a full course of benznidazole treatment under close treatment surveillance. Female sex, skin disorders and mild and moderate ADRs were independently associated with the permanent suspension of benznidazole treatment. In particular, women with moderate skin ADRs had the highest risk of benznidazole treatment interruption.

Spontaneous dormancy protects Trypanosoma cruzi during extended drug exposure

The ability of the Chagas disease agent Trypanosoma cruzi to resist extended in vivo exposure to highly effective trypanocidal compounds prompted us to explore the potential for dormancy and its contribution to failed drug treatments in this infection. We document the development of non-proliferating intracellular amastigotes in vivo and in vitro in the absence of drug treatment. Non-proliferative amastigotes ultimately converted to trypomastigotes and established infections in new host cells. Most significantly, dormant amastigotes were uniquely resistant to extended drug treatment in vivo and in vitro and could re-establish a flourishing infection after as many as 30 days of drug exposure. These results demonstrate a dormancy state in T. cruzi that accounts for the failure of highly cytotoxic compounds to completely resolve the infection. The ability of T. cruzi to establish dormancy throws into question current methods for identifying curative drugs but also suggests alternative therapeutic approaches.

Chagas disease is one of the most harmful tropical diseases in the Americas. It affects millions of people, predominantly in Latin America. It is usually spread by kissing bugs infected with Trypanosoma cruzi parasites. It is considered a neglected tropical disease because few effective treatments and preventive methods are routinely used.

Several drugs can kill T. cruzi parasites, but they often fail to cure the infection. Many people with Chagas disease go on to have life-long infections and eventually develop heart failure. The reason for the high rate of treatment failure is not known. It does not appear to be the result of the parasites developing resistance to the drugs. One possibility is that the parasites can hide in a dormant state in the body, dodging the toxic drugs and living to reproduce another day.

Now, Sánchez-Valdéz et al. identify a dormant form of the T. cruzi parasite that allows the infection to persist after treatment. In the experiments, a non-reproducing form of the so-called amastigote stage of the T. cruzi parasite inside the host cells was observed in infected mice and human cells. While some of the amastigote parasites continue multiplying, a few stop even without drug treatment – but can resume multiplication at a later time. They may also be able to change into the trypomastigote form of the parasite, which can infect new cells. These non-multiplying amastigotes can survive drug treatment for as long as 30 days, whereas the multiplying amastigotes are killed by such drugs. However, the surviving amastigotes then reestablish active infections after treatment has stopped.

The experiments explain why treatment so often fails to cure Chagas disease. This suggests new treatment strategies are needed, including using existing drugs for a longer time perhaps with less frequent doses. New therapies that kill the dormant amastigotes may also help. Treatments that overcome the parasite’s ability to hide, could stop the progression of the disease and prevent heart-related deaths in those with persistent T. cruzi infections.

Investigation of the binding mode of a novel cruzain inhibitor by docking, molecular dynamics, ab initio and MM/PBSA calculations

Chagas disease remains a major health problem in South America, and throughout the world. The two drugs clinically available for its treatment have limited efficacy and cause serious adverse effects. Cruzain is an established therapeutic target of Trypanosoma cruzi, the protozoan that causes Chagas disease. Our group recently identified a competitive cruzain inhibitor (compound 1) with an IC₅₀ = 15 µM that is also more synthetically accessible than the previously reported lead, compound 2. Prior studies, however, did not propose a binding mode for compound 1, hindering understanding of the structure-activity relationship and optimization. Here, the cruzain binding mode of compound 1 was investigated using docking, molecular dynamics (MD) simulations with ab initio derived parameters, ab initio calculations, and MM/PBSA. Two ligand protonation states and four binding poses were evaluated. A careful ligand parameterization method was employed to derive more physically meaningful parameters than those obtained by automated tools. The poses of unprotonated 1 were unstable in MD, showing large conformational changes and diffusing away from the binding site, whereas the protonated form showed higher stability and interaction with negatively charged residues Asp161 and Cys25. MM/PBSA also suggested that these two residues contribute favorably to binding of compound 1. By combining results from MD, ab initio calculations, and MM/PBSA, a binding mode of 1 is proposed. The results also provide insights for further optimization of 1, an interesting lead compound for the development of new cruzain inhibitors.

Identification of di-substituted ureas that prevent growth of trypanosomes through inhibition of translation initiation

Some 1,3-diarylureas and 1-((1,4-trans)−4-aryloxycyclohexyl)−3-arylureas (cHAUs) activate heme-regulated kinase causing protein synthesis inhibition via phosphorylation of the eukaryotic translation initiation factor 2 (eIF2) in mammalian cancer cells. To evaluate if these agents have potential to inhibit trypanosome multiplication by also affecting the phosphorylation of eIF2 alpha subunit (eIF2α), we tested 25 analogs of 1,3-diarylureas and cHAUs against Trypanosoma cruzi, the agent of Chagas disease. One of them (I-17) presented selectivity close to 10-fold against the insect replicative forms and also inhibited the multiplication of T. cruzi inside mammalian cells with an EC₅₀ of 1–3 µM and a selectivity of 17-fold. I-17 also prevented replication of African trypanosomes (Trypanosoma brucei bloodstream and procyclic forms) at similar doses. It caused changes in the T. cruzi morphology, arrested parasite cell cycle in G1 phase, and promoted phosphorylation of eIF2α with a robust decrease in ribosome association with mRNA. The activity against T. brucei also implicates eIF2α phosphorylation, as replacement of WT-eIF2α with a non-phosphorylatable eIF2α, or knocking down eIF2 protein kinase-3 by RNAi increased resistance to I-17. Therefore, we demonstrate that eIF2α phosphorylation can be engaged to develop trypanosome-static agents in general, and particularly by interfering with activity of eIF2 kinases.

3-pyridyl inhibitors with novel activity against Trypanosoma cruzi reveal in vitro profiles can aid prediction of putative cytochrome P450 inhibition

Using high throughput, high-content imaging, a proprietary library was screened against intracellular Trypanosoma cruzi amastigotes to identify compounds with novel activity against the parasite. Five inhibitors were discovered, which did not clear all of the parasites from 3T3 host cells following 48 hours exposure, and were identified as putative T. cruzi cytochrome P450 (TcCYP51) inhibitors. TcCYP51 inhibitors are not favourable for the drug discovery pipeline for treatment of Chagas Disease infection due to clinical and pre-clinical failures. To determine if there were in vitro inhibitory characteristics of these compounds that could aid the prediction of TcCYP51 inhibition further profiling using imaging and fluorescence based assays was undertaken. It was determined that in vitro profiles, coupled with analysis of chemical structure, could support the early prediction of putative TcCYP51 activity and thus enable early de-prioritisation of these compounds from progression through the drug discovery pipeline.

In Silico Studies Designed to Select Sesquiterpene Lactones with Potential Antichagasic Activity from an In-House Asteraceae Database

Chagas disease is an endemic disease caused by Trypanosoma cruzi, which affects more than eight million people, mostly in the Americas. A search for new treatments is necessary to control and eliminate this disease. Sesquiterpene lactones (SLs) are an interesting group of secondary metabolites characteristic of the Asteraceae family that have presented a wide range of biological activities. From the ChEMBL database, we selected a diverse set of 4452, 1635, and 1322 structures with tested activity against the three T. cruzi parasitic forms: amastigote, trypomastigote, and epimastigote, respectively, to create random forest (RF) models with an accuracy of greater than 74 % for cross-validation and test sets. Afterward, a ligand-based virtual screen of the entire SLs of the Asteraceae database stored in SistematX (1306 structures) was performed. In addition, a structure-based virtual screen was also performed for the same set of SLs using molecular docking. Finally, using an approach combining ligand-based and structure-based virtual screening along with the equations proposed in this study to normalize the probability scores, we verified potentially active compounds and established a possible mechanism of action.

Phenotypic screening approaches for Chagas disease drug discovery

INTRODUCTION

Chagas disease, caused by the parasite Trypanosoma cruzi, is a global public health issue. Current treatments targeting the parasite are limited to two old nitroheterocyclic drugs with serious side effects. The need for new and safer drugs has prompted numerous drug discovery efforts to identify compounds suitable for parasitological cure in the last decade. Areas covered: Target-based drug discovery has been limited by the small number of well-validated targets - the latest example being the failure of azoles, T. cruzi CYP51 inhibitors, in proof-of-concept clinical trials; instead phenotypic-based drug discovery has become the main pillar of Chagas R&D. Rather than focusing on the technical features of these screening assays, the authors describe the different assays developed and available in the field, and provide a critical view on their values and limitations in the screening cascade for Chagas drug development. Expert opinion: The application of technological advances to the field of Chagas disease has led to a variety of phenotypic assays that have not only changed the disease discovery landscape but have also helped us to gain a better understanding of parasite/host interactions. Recent examples of target resolution from phenotypic hits will uncover new opportunities for drug discovery for Chagas disease.

Beneficial immunomodulatory and neuro digestive effect in Trypanosoma cruzi infection after Lycopodium clavatum 13c treatment

Studies show that highly diluted medications demonstrate benefits in treating infections, constituting an alternative for their treatment. The present study evaluated the effects of Lycopodium clavatum, dynamization 13c, in Wistar rats infected with T. cruzi. In this study 42 male rats were intraperitoneally inoculated with T. cruzi - Y strain and allocated into groups: IC (infected control group) and Ly (treated with L. clavatum 13c). The cytokines dosage (IFN-γ, IL-12, IL-10, IL-4), quantification and morphometry of myenteric neurons were evaluated. The treatment with L. clavatum modifies the immune response, with increase of IFN-γ on day 10 a.i. and IL-12 on day 24 a.i., decrease of IL-10 concentration on day 10 a.i. and subsequent increase of this cytokine and IL-4 on day 24 a.i., affording a bigger number of myenteric neurons compared to IC group. Thus, L. clavatum 13c promoted on rats infected with T. cruzi a beneficial immunomodulatory action reducing the pathogenic progression of digestive Chagas disease.

Novel Imidazo[4,5-c][1,2,6]thiadiazine 2,2-dioxides as antiproliferative trypanosoma cruzi drugs: Computational screening from neural network, synthesis and in vivo biological properties

A new family of imidazo[4,5-c][1,2,6]thiadiazine 2,2-dioxide with antiproliferative Trypanosoma cruzi properties was identified from a neural network model published by our group. The synthesis and evaluation of this new class of trypanocidal agents are described. These compounds inhibit the growth of Trypanosoma cruzi, comparable with benznidazole or nifurtimox. In vitro assays were performed to study their effects on the growth of the epimastigote form of the Tulahuen 2 strain, as well as the epimastigote and amastigote forms of CL clone B5 of Trypanosoma cruzi. To verify selectivity towards parasite cells, the non-specific cytotoxicity of the most relevant compounds was studied in mammalian cells, i.e. J774 murine macrophages and NCTC clone 929 fibroblasts. Furthermore, these compounds were assayed regarding the inhibition of cruzipain. In vivo studies revealed that one of the compounds, 19, showed interesting trypanocidal activity, and could be a very promising candidate for the treatment of Chagas disease.

Simple dialkyl pyrazole-3,5-dicarboxylates show in vitro and in vivo activity against disease-causing trypanosomatids

The synthesis and antiprotozoal activity of some simple dialkyl pyrazole-3,5-dicarboxylates (compounds 2-6) and their sodium salts (pyrazolates) (compounds 7-9) against Trypanosoma cruzi, Leishmania infantum and Leishmania braziliensis are reported. In most cases the studied compounds showed, especially against the clinically significant amastigote forms, in vitro activities higher than those of the reference drugs (benznidazole for T. cruzi and glucantime for Leishmania spp.); furthermore, the low non-specific cytotoxicities against Vero cells and macrophages shown by these compounds led to good selectivity indexes, which are 8-72 times higher for T. cruzi amastigotes and 15-113 times higher for Leishmania spp. amastigotes than those of the respective reference drugs. The high efficiency of diethyl ester 3 and its sodium salt 8 against the mentioned protozoa was confirmed by further in vitro assays on infection rates and by an additional in vivo study in a murine model of acute and chronic Chagas disease. The inhibitory capacity of compounds 3 and 8 on the essential iron superoxide dismutase of the aforementioned parasites may be related to the observed anti-trypanosomatid activity. The low acute toxicity of compounds 3 and 8 in mice is also reported in this article.

Mechanistic Insights into the Anti-angiogenic Activity of Trypanosoma cruzi Protein 21 and its Potential Impact on the Onset of Chagasic Cardiomyopathy

Chronic chagasic cardiomyopathy (CCC) is arguably the most important form of the Chagas Disease, caused by the intracellular protozoan Trypanosoma cruzi; it is estimated that 10-30% of chronic patients develop this clinical manifestation. The most common and severe form of CCC can be related to ventricular abnormalities, such as heart failure, arrhythmias, heart blocks, thromboembolic events and sudden death. Therefore, in this study, we proposed to evaluate the anti-angiogenic activity of a recombinant protein from T. cruzi named P21 (rP21) and the potential impact of the native protein on CCC. Our data suggest that the anti-angiogenic activity of rP21 depends on the protein's direct interaction with the CXCR4 receptor. This capacity is likely related to the modulation of the expression of actin and angiogenesis-associated genes. Thus, our results indicate that T. cruzi P21 is an attractive target for the development of innovative therapeutic agents against CCC.

Desing and synthesis of potent anti-Trypanosoma cruzi agents new thiazoles derivatives which induce apoptotic parasite death

Chagas disease, caused by the kinetoplastid protozoan parasite Trypanosoma cruzi, remains a relevant cause of illness and premature death and it is estimated that 6 million to 7 million people are infected worldwide. Although chemotherapy options are limited presenting serious problems, such as low efficacy and high toxicity. T. cruzi is susceptible to thiazoles, making this class of compounds appealing for drug development. Previously, thiazoles resulted in an increase in anti-T. cruzi activity in comparison to thiosemicarbazones. Here, we report the structural planning, synthesis and anti-T. cruzi evaluation of new thiazoles derivatives (3a-m and 4a-m), designed from molecular hybridization associated with non-classical bioisosterism. By varying substituents attached to the phenyl and thiazole rings, substituents were observed to retain, enhance or greatly increase their anti-T. cruzi activity, in comparison to the corresponding thiosemicarbazones. In most cases, electron-withdrawing substituents, such as bromine, 3,4-dichloro and nitro groups, greatly increased antiparasitic activity. Specifically, new thiazoles were identified that inhibit the epimastigote proliferation and were toxic for trypomastigotes without affecting macrophages viability. These compounds were also evaluated against cruzain. However, inhibition of this enzyme was not observed, suggesting that the compounds work through another mechanism. In addition, examination of T. cruzi cell death showed that these molecules induce apoptosis. In conclusion, except for compounds 3h and 3k, all thiazoles derivatives evaluated exhibited higher cytotoxic activity against the trypomastigote forms than the reference medicament benznidazole, without affecting macrophages viability. Compounds 4d and 4k were highlights, CC50 = 1.2 e 1.6 μM, respectively. Mechanistically, these compounds do not inhibit the cruzain, but induce T. cruzi cell death by an apoptotic process, being considered a good starting point for the development of new anti-Chagas drug candidates.

Carbonic anhydrases from Trypanosoma and Leishmania as anti-protozoan drug targets

Trypanosoma cruzi and Leishmania spp. are protozoa of the Trypanosomatidae family, being the etiological agents of two widespread parasitic diseases, Chagas disease and leishmaniasis, respectively. Both parasites are the focus of worldwide research with the aim to find effective and less toxic drugs than the few ones available so far, and for controlling the spread of the diseases. Carbonic anhydrases (CAs, EC 4.2.1.1) belonging to the α- and β-class were recently identified in these protozoans and several studies suggested that they could be new targets for drug development. Sulfonamide, thiol and hydroxamate inhibitors effectively inhibited the α-CA from T. cruzi (TcCA) and the β-CA from L. donovani chagasi (LdccCA) in vitro, and some of them also showed in vivo efficacy in inhibiting the growth of the parasites in animal models of Chagas disease and leishmaniasis. As few therapeutic options are presently available for these orphan diseases, protozoan CA inhibition may represent a novel strategy to address this stringent health problem.

Different treatment schemes and dynamizations of Trypanosoma cruzi biotherapies: what information do they transfer to the organism in infected mice?

BACKGROUND

The use of biotherapies in Trypanosoma cruzi infection can provide an understanding about effects of these highly diluted medications.

OBJECTIVES

To evaluate different treatment schemes and dynamizations of biotherapies prepared from blood trypomastigotes (buffy coat) in mice infected with T. cruzi.

METHODS

Swiss mice infected with Y strain of T. cruzi were divided into two experiments. Experiment 1, all treated groups received biotherapy 7dH (10 μL/mL ad libitum) in different treatment schemes: TB_7dH - treated 3 days before infection; TBA_7dH - treated 3 days before and after infection; TBAe.d._7dH - treated 3 days before infection and every day after infection and IC - infection control. Experiment 2, all treated groups received medication in different dynamizations 3 days before and after infection (10 μL/mL ad libitum): TBA_15dH - treated with biotherapy 15dH; TBA_16dH - treated with biotherapy 16dH; TBA_17dH - treated with biotherapy 17dH; TBA_p.chords - treated with biotherapy 'potency chords' and IC - infection control. We evaluated parasitological and clinical parameters.

RESULTS

Experiment 1 showed that different treatment schemes with biotherapy 7dH produced different effects on infection evolution. TBA_7dH group had the best outcome, with lower parasitemia, higher survival, and better clinical evolution compared to IC. Experiment 2 showed that biotherapy 'potency chords' had effects different from the individual dynamizations that it contained (15dH, 16dH, and 17dH). Animals that had patent parasitemia had delayed emergence of parasites in blood and subsequent increase in parasitemia, but had better clinical evolution compared to IC.

CONCLUSIONS

The effects of T. cruzi biotherapies depend on frequency at which they are administered, dynamization, and host-parasite relationship/individual susceptibility of treated organism. Biotherapy appeared to transfer to infected organism 'antigenic information' related to parasite and 'disease information' related to molecules produced by host's immune response and contained in the buffy coat used to prepare the medication.

Development of a PCR Assay to Detect Low Level Trypanosoma cruzi in Blood Specimens Collected with PAXgene Blood DNA Tubes for Clinical Trials Treating Chagas Disease

Chagas disease is caused by the parasitic infection of Trypanosoma cruzi (T. cruzi). The STOP CHAGAS clinical trial was initiated in 2011 to evaluate posaconazole in treating Chagas disease, with treatment success defined as negative qualitative PCR results of detecting the parasites in blood specimens collected post-treatment. PAXgene Blood DNA tubes were utilized as a simple procedure to collect and process blood specimens. However, the PAXgene blood specimens challenged published T. cruzi PCR methods, resulting in poor sensitivity and reproducibility. To accurately evaluate the treatment efficacy of the clinical study, we developed and validated a robust PCR assay for detecting low level T. cruzi in PAXgene blood specimens. The assay combines a new DNA extraction method with a custom designed qPCR assay, resulting in limit of detection of 0.005 and 0.01 fg/μl for K98 and CL Brener, two representative strains of two of T. cruzi’s discrete typing units. Reliable qPCR standard curves were established for both strains to measure parasite loads, with amplification efficiency ≥ 90% and the lower limit of linearity ≥ 0.05 fg/μl. The assay successfully analyzed the samples collected from the STOP CHAGAS study and may prove useful for future global clinical trials evaluating new therapies for asymptomatic chronic Chagas disease.

Chagas disease is caused by the infection of the protozoan parasite Trypanosoma cruzi (T. cruzi) and carries a significant tropical disease burden in the Western Hemisphere. The STOP CHAGAS study was a global clinical trial evaluating therapies for Chagas disease. PAXgene blood DNA tubes used by the study simplified and standardized the sample collection and processing procedures, but challenged published PCR assays that detect circulating T. cruzi. In this study, we report our effort of developing and validating a robust, sensitive and specific PCR assay for detecting T. cruzi in PAXgene blood specimens. The efficacy outcome results of the STOP CHAGAS study that utilized our assay further support the use of the PCR assay as a marker of therapeutic response for patients with Chagas disease.

Nitroheterocyclic drugs cure experimental Trypanosoma cruzi infections more effectively in the chronic stage than in the acute stage

The insect-transmitted protozoan parasite Trypanosoma cruzi is the causative agent of Chagas disease, and infects 5-8 million people in Latin America. Chagas disease is characterised by an acute phase, which is partially resolved by the immune system, but then develops as a chronic life-long infection. There is a consensus that the front-line drugs benznidazole and nifurtimox are more effective against the acute stage in both clinical and experimental settings. However, confirmative studies have been restricted by difficulties in demonstrating sterile parasitological cure. Here, we describe a systematic study of nitroheterocyclic drug efficacy using highly sensitive bioluminescence imaging of murine infections. Unexpectedly, we find both drugs are more effective at curing chronic infections, judged by treatment duration and therapeutic dose. This was not associated with factors that differentially influence plasma drug concentrations in the two disease stages. We also observed that fexinidazole and fexinidazole sulfone are more effective than benznidazole and nifurtimox as curative treatments, particularly for acute stage infections, most likely as a result of the higher and more prolonged exposure of the sulfone derivative. If these findings are translatable to human patients, they will have important implications for treatment strategies.

Combination Chemotherapy with Suboptimal Doses of Benznidazole and Pentoxifylline Sustains Partial Reversion of Experimental Chagas' Heart Disease

Chronic chagasic cardiomyopathy (CCC) progresses with parasite persistence, fibrosis, and electrical alterations associated with an unbalanced immune response such as high plasma levels of tumor necrosis factor (TNF) and nitric oxide (NO). Presently, the available treatments only mitigate the symptoms of CCC. To improve CCC prognosis, we interfered with the parasite load and unbalanced immune response using the trypanocidal drug benznidazole (Bz) and the immunoregulator pentoxifylline (PTX). C57BL/6 mice chronically infected with the Colombian strain of Trypanosoma cruzi and with signs of CCC were treated for 30 days with a suboptimal dose of Bz (25 mg/kg of body weight), PTX (20 mg/kg), or their combination (Bz plus PTX) and analyzed for electrocardiographic, histopathological, and immunological changes. Bz (76%) and Bz-plus-PTX (79%) therapies decreased parasite loads. Although the three therapies reduced myocarditis and fibrosis and ameliorated electrical alterations, only Bz plus PTX restored normal heart rate-corrected QT (QTc) intervals. Bz-plus-PTX-treated mice presented complementary effects of Bz and PTX, which reduced TNF expression (37%) in heart tissue and restored normal TNF receptor 1 expression on CD8⁺ T cells, respectively. Bz (85%) and PTX (70%) therapies reduced the expression of inducible nitric oxide synthase (iNOS/NOS2) in heart tissue, but only Bz (58%) reduced NO levels in serum. These effects were more pronounced after Bz-plus-PTX therapy. Moreover, 30 to 50 days after treatment cessation, reductions of the prolonged QTc and QRS intervals were sustained in Bz-plus-PTX-treated mice. Our findings support the importance of interfering with the etiological agent and immunological abnormalities to improve CCC prognosis, opening an opportunity for a better quality of life for Chagas' disease (CD) patients.

Serological based monitoring of a cohort of patients with chronic Chagas disease treated with benznidazole in a highly endemic area of northern Argentina

This study aimed to evaluate well-documented diagnostic antigens, named B13, 1F8 and JL7 recombinant proteins, as potential markers of seroconversion in treated chagasic patients. Prospective study, involving 203 patients treated with benznidazole, was conducted from endemic areas of northern Argentina. Follow-up was possible in 107 out of them and blood samples were taken for serology and PCR assays before and 2, 3, 6, 12, 24 and 36 months after treatment initiation. Reactivity against Trypanosoma cruzi lysate and recombinant antigens was measured by ELISA. The rate of decrease of antibody titers showed nonlinear kinetics with an abrupt drop within the first three months after initiation of treatment for all studied antigens, followed by a plateau displaying a low decay until the end of follow-up. At this point, anti-B13, anti-1F8 and anti-JL7 titers were relatively close to the cut-off line, while anti-T. cruzi antibodies still remained positive. At baseline, 60.8% (45/74) of analysed patients tested positive for parasite DNA by PCR and during the follow-up period in 34 out of 45 positive samples (75.5%) could not be detected T. cruzi DNA. Our results suggest that these antigens might be useful as early markers for monitoring antiparasitic treatment in chronic Chagas disease.

Electrocardiographic Abnormalities and Treatment with Benznidazole among Children with Chronic Infection by Trypanosoma cruzi: A Retrospective Cohort Study

Background

Chronic infection by Trypanosoma cruzi could cause heart conduction disturbances. We sought to analyze electrocardiographic abnormalities among children with chronic T. cruzi infection with and without trypanocidal treatment with benznidazole.

Methodology/Principal Findings

We studied 111 children 6–16 years of age with asymptomatic chronic T. cruzi infection who were recruited in 1991–1992 in Salta, Argentina. Most children were randomly assigned to benznidazole 5 mg/Kg/day (n = 47) or matching placebo (n = 48) for 60 days. Remaining children (n = 16) received treatment with benznidazole 5 mg/Kg/day open-label. Electrocardiograms were obtained at baseline and in 1995–1996, 1998, 2000 and 2005, and were analyzed using the Buenos Aires method. Among the 94 children with an electrocardiogram at baseline, 8 (8.5%) had electrocardiographic abnormalities, including 4 (4.7%) children with right bundle branch block. Proportion of abnormal electrocardiograms in the full population (n = 111) remained constant over time (media follow-up 8.6 years). Multivariable adjusted prevalence ratios (95% confidence interval [95%CI]) for electrocardiographic abnormalities in 1995–1996, 1998, 2000 and 2005 comparing children treated with benznidazole versus those not treated were 2.76 (0.66, 11.60), 2.33 (0.44, 12.31), 3.06 (0.48, 19.56), and 1.94 (0.33, 11.25), respectively. Among the 86 children with a normal electrocardiogram at baseline, 16 (18.6%) developed electrocardiographic abnormalities during follow-up. The multivariable adjusted hazard ratio for incident electrocardiographic abnormalities comparing children treated with benznidazole versus those not treated was 0.68 (95%CI: 0.25, 1.88).

Conclusions/Significance

Electrocardiographic abnormalities are frequent among children with chronic T. cruzi infection. Treatment with benznidazole for 60 days may not be associated with less electrocardiographic abnormalities.

There are few data available on the natural history of electrocardiographic abnormalities among children with chronic Trypanosoma cruzi infection. Also, few studies analyzed the effect of benznidazole to prevent electrocardiographic abnormalities in this population. In the current study, electrocardiographic abnormalities were frequent among children with chronic T. cruzi infection. Results from the current study also suggest that treatment with benznidazole may not be associated with less electrocardiographic abnormalities. The current study highlights the need of further research to prevent cardiovascular manifestations associated with chronic T. cruzi infection.

Inflammation Enhances the Risks of Stroke and Death in Chronic Chagas Disease Patients

Ischemic strokes have been implicated as a cause of death in Chagas disease patients. Inflammation has been recognized as a key component in all ischemic processes, including the intravascular events triggered by vessel interruption, brain damage and repair. In this study, we evaluated the association between inflammatory markers and the death risk (DR) and stroke risk (SR) of patients with different clinical forms of chronic Chagas disease. The mRNA expression levels of cytokines, transcription factors expressed in the adaptive immune response (Th1, Th2, Th9, Th17, Th22 and regulatory T cell), and iNOS were analyzed by real-time PCR in peripheral blood mononuclear cells of chagasic patients who exhibited the indeterminate, cardiac, digestive and cardiodigestive clinical forms of the disease, and the levels of these transcripts were correlated with the DR and SR. Cardiac patients exhibited lower mRNA expression levels of GATA-3, FoxP3, AHR, IL-4, IL-9, IL-10 and IL-22 but exhibited higher expression of IFN-γ and TNF-α compared with indeterminate patients. Digestive patients showed similar levels of GATA-3, IL-4 and IL-10 than indeterminate patients. Cardiodigestive patients exhibited higher levels of TNF-α compared with indeterminate and digestive patients. Furthermore, we demonstrated that patients with high DR and SR exhibited lower GATA-3, FoxP3, and IL-10 expression and higher IFN-γ, TNF-α and iNOS mRNA expression than patients with low DR and SR. A negative correlation was observed between Foxp3 and IL-10 mRNA expression and the DR and SR. Moreover, TNF-α and iNOS expression was positively correlated with DR and SR. Our data suggest that an inflammatory imbalance in chronic Chagas disease patients is associated with a high DR and SR. This study provides a better understanding of the stroke pathobiology in the general population and might aid the development of therapeutic strategies for controlling the morbidity and mortality of Chagas disease.

Antichagasic and trichomonacidal activity of 1-substituted 2-benzyl-5-nitroindazolin-3-ones and 3-alkoxy-2-benzyl-5-nitro-2H-indazoles

Two series of new 5-nitroindazole derivatives, 1-substituted 2-benzylindazolin-3-ones (6-29, series A) and 3-alkoxy-2-benzyl-2H-indazoles (30-37, series B), containing differently functionalized chains at position 1 and 3, respectively, have been synthesized starting from 2-benzyl-5-nitroindazolin-3-one 5, and evaluated against the protozoan parasites Trypanosoma cruzi and Trichomonas vaginalis, etiological agents of Chagas disease and trichomonosis, respectively. Many indazolinones of series A were efficient against different morphological forms of T. cruzi CL Brener strain (compounds 6, 7, 9, 10 and 19-21: IC50 = 1.58-4.19 μM for epimastigotes; compounds 6, 19-21 and 24: IC50 = 0.22-0.54 μM for amastigotes) being as potent as the reference drug benznidazole. SAR analysis suggests that electron-donating groups at position 1 of indazolinone ring are associated with an improved antichagasic activity. Moreover, compounds of series A displayed low unspecific toxicities against an in vitro model of mammalian cells (fibroblasts), which were reflected in high values of the selectivity indexes (SI). Compound 20 was also very efficient against amastigotes from Tulahuen and Y strains of T. cruzi (IC50 = 0.81 and 0.60 μM, respectively), showing low toxicity towards cardiac cells (LC50 > 100 μM). In what concerns compounds of series B, some of them displayed moderate activity against trophozoites of a metronidazole-sensitive isolate of T. vaginalis (35 and 36: IC50 = 9.82 and 7.25 μM, respectively), with low unspecific toxicity towards Vero cells. Compound 36 was also active against a metronidazole-resistant isolate (IC50 = 9.11 μM) and can thus be considered a good prototype for the development of drugs directed to T. vaginalis resistant to 5-nitroimidazoles.