Absence of CD4+ T lymphocytes, CD8+ T lymphocytes, or B lymphocytes has different effects on the efficacy of posaconazole and benznidazole in treatment of experimental acute Trypanosoma cruzi infection

Long term follow-up of Trypanosoma cruzi infection and Chagas disease manifestations in mice treated with benznidazole or posaconazole

Chagas' Disease, caused by the protozoan parasite Trypanosoma cruzi, is responsible for up to 41% of the heart failures in endemic areas in South America and is an emerging infection in regions of North America, Europe, and Asia. Treatment is suboptimal due to two factors. First, the lack of an adequate biomarker to predict disease severity and response to therapy; and second, up to 120-days treatment course coupled with a significant incidence of adverse effects from the drug currently used. Because the disease can manifest itself clinically a few years to decades after infection, controversy remains concerning the suitability of current drug treatment (benznidazole), and the efficacy of alternative drugs (e.g. posaconazole). We therefore followed the clinical course, and PCR detection of parasite burden, in a mouse model of infection for a full year following treatment with benznidazole or posaconazole. Efficacy of the two drugs depended on whether the treatment was performed during the acute model or the chronic model of infection. Posaconazole was clearly superior in treatment of acute disease whereas only benznidazole had efficacy in the chronic model. These results have important implications for the design and analysis of human clinical trials, and the use of specific drugs in specific clinical settings.

Chagas disease is a parasitic infection that can be incapacitating, leading to heart failure with risk of sudden death. Currently, only one drug treatment is available, Benznidazole, but it demands a long period of treatment, has variable efficacy and leads to serious side effects that can lead to discontinuation of the treatment. An alternative therapy, the anti-fungal drug, Posaconazole, was repurposed for treatment of Chagas disease, but its use has been controversial with conflicting results in studies from different groups. In our approach, we followed the parasitic infection, disease symptoms and persistence of the pathogen in mice for a full year after treatment with Benznidazole or Posaconazole. Posaconazole treatment was more effective in the early infection (acute disease) whereas only Benznidazole had efficacy in the chronic model. This information can have important implications for the design and analysis of human clinical trials, and the use of specific drugs in specific clinical settings.

Effects of Highly Diluted Drugs on Experimental Infection with Trypanosoma cruzi In Vivo: Systematic Review

Objective: To investigate, through a systematic review, the effects of the use of highly diluted drugs in the treatment of experimental infection with Trypanosoma cruzi. Design: The authors searched for scientific publications in the databases PubMed, Web of Science, SCOPUS, LILACS, and the Google Scholar search system, from 2000 to 2018, following the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) statement. According to the criteria established, a total of 22 studies were included. Settings/Location: The study took place at the State University of Maringá, Maringá, PR, Brazil. Subjects: Male mice (Mus musculus) or rats (Rattus norvegicus). Interventions: Highly diluted drugs. Outcome measures: The parameters evaluated in the studies were parasitological, clinical, immunological, histopathological and hematological. Results: The studies demonstrated that the effects of highly diluted drugs are related to their dynamizations, treatment regimen, and host susceptibility to T. cruzi infection, and depend on the initial information transmitted to the treated organism, making this information the "model" of how the treated organism will react. Regardless of the mechanism of action, these drugs provide a decrease in inflammation, which is one of the central phenomena of the pathogenesis of T. cruzi infection. Conclusions: This systematic review brings out the importance of the T. cruzi infection model as a reliable and valid model for studying different effects produced by highly diluted drugs. Considering the findings and in a broader perspective, this study contributes to considering these drugs as a possible way of dealing with "treatment" in general, presents the need to reexamine the biochemical model and develop a model for the effect of high dilutions in general, as well as for the treatment of parasitic infections.

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.

The effect of benznidazole dose among the efficacy outcome in the murine animal model. A quantitative integration of the literature

Despite more than 100 years since it was firstly described Chagas disease, only two drugs are available to treat Chagas disease: Nifurtimox launched by Bayer in 1965 and benznidazole launched by Roche in 1971. Drug discovery initiatives have been looking for new compounds as an alternative to these old drugs. Although new platforms have been used with the latest technologies, a critical step on that process still relies on the in vivo model. Unfortunately, to date, available animal models have limited predictive value and there is no standardization. With the aim to better understand the role of benznidazole, the current standard of care of Chagas disease, we performed this review. We intend to analyze the influence of the experimental design of the most used animal model, the murine model, in the assessment of the efficacy endpoint.

Could angiotensin-modulating drugs be relevant for the treatment of Trypanosoma cruzi infection? A systematic review of preclinical and clinical evidence

Although leucocytes are targets of renin-angiotensin system (RAS) effector molecules and RAS-modulating drugs exert immunomodulatory effects, their impact onTrypanosoma cruziinfection remains poorly understood. By using the framework of a systematic review, we integrated the preclinical and clinical evidence to investigate the relevance of angiotensin-inhibiting drugs onT. cruziinfections. From a comprehensive and structured search in biomedical databases, only original studies were analysed. In preclinical and clinical studies, captopril, enalapril and losartan were RAS-modulating drugs used. The mainin vitrofindings indicated that these drugs increased parasite uptake per host cells, IL-12 expression by infected dendritic cells and IFN-γby T lymphocytes, in addition to attenuating IL-10 and IL-17 production by CD8 + T cells. In animal models, reduced parasitaemia, tissue parasitism, leucocytes infiltration and mortality were often observed inT. cruzi-infected animals receiving RAS-modulating drugs. In patients with Chagas’ disease, these drugs exerted a controversial impact on cytokine and hormone levels, and a limited effect on cardiovascular function. Considering a detailed evaluation of reporting and methodological quality, the current preclinical and clinical evidence is at high risk of bias, and we hope that our critical analysis will be useful in mitigating the risk of bias in further studies.

Dynamics of T Cells Repertoire During Trypanosoma cruzi Infection and its Post-Treatment Modulation

Chagas disease courses with different clinical phases and has a variable clinical presentation and progression. The acute infection phase mostly exhibits a non-specific symptomatology. In the absence of treatment, the acute phase is followed by a chronic phase, which is initially asymptomatic. This chronic asymptomatic phase of the disease is characterized by a fragile balance between the host's immune response and the parasite replication. The loss of this balance is crucial for the progression of the sickness. The virulence and tropism of the T. cruzi infecting strain together to the inflammation processes in the cardiac tissue are the main factors for the establishment and severity of the cardiomyopathy. The efficacy of treatment in chronic Chagas disease patients is controversial. However, several studies carried out in chronic patients demonstrated that antiparasitic treatment reduces parasite load in the bloodstream and leads to an improvement in the immune response against the Trypanosoma cruzi parasite. The present review is mainly focused on the cellular patterns associated to the clinical status and the evolution of the disease in chronic patients, as well as the effectiveness of the treatment related to T. cruzi infection control. Therefore, an emphasis is placed on the dynamics of specific-antigens T cell subpopulations, their memory and activation phenotypes, their functionality and their contribution to pathogenesis or disease control, as well as their association with risk of congenital transmission of the parasite.

Benznidazole affects expression of Th1, Th17 and Treg cytokines during acute experimental Trypanosoma cruzi infection

Background

The present study evaluated the effect of treatment with benznidazole on mRNA expression of IFN-γ, IL-17, IL-10, TGF-β and FoxP3 in spleen and heart tissue of BALB/c mice in the acute phase of an experimental infection with Trypanosoma cruzi, strains JLP or Y.

Methods

The mRNA expression of cytokines and parasite load were assessed by q-PCR. Dependent groups were compared using Student's paired t-test and independent groups were compared using Student's unpaired t-test.

Results

Infection with the JLP or Y strains increased expression of IFN-γ in the heart and of IL-10 and IL-17 in the spleen and heart compared to uninfected animals. Treatment increased the expression of IFN-γ and decreased the expression of IL-17, IL-10, TGF- β and Foxp3 in spleen and heart tissue compared to untreated infected animals.

Conclusion

Benznidazole can induce Th1 profile in the initial of the acute phase. The treatment decreased the parasite load in both organs, although the number of parasites in Y-strain-infected mice remained high. The data suggest that benznidazole may modulate cytokine expression in infection and can be dependent of the strain. However, treatment was not fully effective in the infection provoked by Y strain, probably due to the characteristics of the strain itself.

Canova medication changes TNF-α and IL-10 serum levels in mice infected with Trypanosoma cruzi Y strain

OBJECTIVE

To identify whether Canova medication changes TNF-α and IL-10 serum levels in mice infected with Trypanosoma cruzi Y strain.

METHODS

Animals were divided into five groups: non-treated infected animals (I); benznidazole-treated infected animals (Bz; 100 mg/kg body weight, single daily dose by gavage); Canova medication (CM) treated infected animals (CM; 0.2 mL/animal, single daily dose by gavage); benznidazole- and Canova medication-treated infected animals with the above-mentioned dose (Bz+CM); and non-infected animals (C). TNF-α and IL-10 levels were determined in serum aliquots after 4, 7, 10, 13, and 29 days of infection. An ELISA technique was employed with R&D System Inc. antibody pairs.

RESULTS

A high increase in TNF-α and IL-10 levels occurred in the infected and CM-treated groups within the treatment employed on the 10th day after infection, coupled with a IL-10 decrease on the 13th day after infection when compared with the other experimental groups.

CONCLUSIONS

CM may change the balance between plasma cytokine levels (TNF-α and IL-10) in mice infected with Y strain T. cruzi, with important consequences leading towards a more severe infection.

Treatment Success in Trypanosoma cruzi Infection Is Predicted by Early Changes in Serially Monitored Parasite-Specific T and B Cell Responses

BACKGROUND

Chagas disease is the highest impact parasitic disease in Latin America. We have proposed that changes in Trypanosoma cruzi-specific immune responses might serve as surrogate indicators of treatment success. Herein, we addressed in a long-term follow-up study whether cure achieved after treatment can be predicted by changes in non-conventional indexes of anti-parasite serological and T cell activities.

METHODOLOGY/PRINCIPAL FINDINGS

T. cruzi-specific T cell responses, as measured by interferon-γ ELISPOT and T. cruzi-specific antibodies assessed by ELISA, hemagglutination and immunofluorescence tests as well as by a multiplex assay incorporating 14 recombinant T. cruzi proteins were measured in 33 patients at 48-150 months post-benznidazole treatment. Cure - as assessed by conventional serological tests - was associated with an early decline in T. cruzi-specific IFN-γ-producing T cells and in antibody titers measured by the multiplex serological assay. Changes in the functional status and potential of T. cruzi-specific T cells, indicative of reduced antigen stimulation, provided further evidence of parasitological cure following benznidazole treatment. Patients showing a significant reduction in T. cruzi-specific antibodies had higher pre-therapy levels of T. cruzi-specific IFN-γ- producing T cells compared to those with unaltered humoral responses post-treatment.

CONCLUSIONS/SIGNIFICANCE

Monitoring of appropriate immunological responses can provide earlier and robust measures of treatment success in T. cruzi infection.

The use of posaconazole against Chagas disease

PURPOSE OF REVIEW

The current therapeutic scenario against Chagas disease has been recently updated with the use of the triazoles in clinical trials and several experimental assays (in-vitro and in-vivo models) which are bringing novel and promising evidence for the treatment of Chagas diseases, mainly in its chronic phase. We pretend to analyze all the evidence extracted from the in-vitro and in-vivo assays, and try to understand the poor outcome of posaconazole (POS) in the clinical experience.

RECENT FINDINGS

POS is the drug with more advanced development in both experimental model and clinical trial. Despite the promising results initially obtained in the animal model, the clinical trial did not meet expectations. Nevertheless, it has documented the activity against Trypanosoma cruzi either in the animal model or in humans. Also new treatment strategies, combination or sequential schemes, have been evaluated in the animal model.

SUMMARY

POS has been tested in humans showing activity against T. cruzi, but not enough to reach cure by itself. Those results represent one of the most important breakthroughs in the treatment of Chagas disease, and open a window to new strategies as combination therapies or even sequential treatments.

Nanomedicines against Chagas disease: an update on therapeutics, prophylaxis and diagnosis

Chagas disease is a neglected parasitic infection caused by the protozoan Trypanosoma cruzi. After a mostly clinically silent acute phase, the disease becomes a lifelong chronic condition that can lead to chronic heart failure and thromboembolic phenomena followed by sudden death. Antichagasic treatment is only effective in the acute phase but fails to eradicate the intracellular form of parasites and causes severe toxicity in adults. Although conventional oral benznidazol is not a safe and efficient drug to cure chronic adult patients, current preclinical data is insufficient to envisage if conventional antichagasic treatment could be realistically improved by a nanomedical approach. This review will discuss how nanomedicines could help to improve the performance of therapeutics, vaccines and diagnosis of Chagas disease.

Antitrypanosomal Treatment with Benznidazole Is Superior to Posaconazole Regimens in Mouse Models of Chagas Disease

Two CYP51 inhibitors, posaconazole and the ravuconazole prodrug E1224, were recently tested in clinical trials for efficacy in indeterminate Chagas disease. The results from these studies show that both drugs cleared parasites from the blood of infected patients at the end of the treatment but that parasitemia rebounded over the following months. In the current study, we sought to identify a dosing regimen of posaconazole that could permanently clear Trypanosoma cruzi from mice with experimental Chagas disease. Infected mice were treated with posaconazole or benznidazole, an established Chagas disease drug, and parasitological cure was defined as an absence of parasitemia recrudescence after immunosuppression. Twenty-day therapy with benznidazole (10 to 100 mg/kg of body weight/day) resulted in a dose-dependent increase in antiparasitic activity, and the 100-mg/kg regimen effected parasitological cure in all treated mice. In contrast, all mice remained infected after a 25-day treatment with posaconazole at all tested doses (10 to 100 mg/kg/day). Further extension of posaconazole therapy to 40 days resulted in only a marginal improvement of treatment outcome. We also observed similar differences in antiparasitic activity between benznidazole and posaconazole in acute T. cruzi heart infections. While benznidazole induced rapid, dose-dependent reductions in heart parasite burdens, the antiparasitic activity of posaconazole plateaued at low doses (3 to 10 mg/kg/day) despite increasing drug exposure in plasma. These observations are in good agreement with the outcomes of recent phase 2 trials with posaconazole and suggest that the efficacy models combined with the pharmacokinetic analysis employed here will be useful in predicting clinical outcomes of new drug candidates.

Modulation of Trypanosoma cruzi-specific T-cell responses after chemotherapy for chronic Chagas disease

The aim of this review is to describe the contributions of the knowledge of T-cell responses to the understanding of the physiopathology and the responsiveness to etiological treatment during the chronic phase of Chagas disease. T-helper (Th)1 and interleukin (IL)-10 Trypanosoma cruzi-specific T-cells have been linked to the asymptomatic phase or to severe clinical forms of the disease, respectively or vice versa, depending on the T. cruzi antigen source, the patient's location and the performed immunological assays. Parasite-specific T-cell responses are modulated after benznidazole (BZ) treatment in chronically T. cruzi-infected subjects in association with a significant decrease in T. cruzi-specific antibodies. Accumulating evidence has indicated that treatment efficacy during experimental infection with T. cruzi results from the combined action of BZ and the activation of appropriate immune responses in the host. However, strong support of this interaction in T. cruzi-infected humans remains lacking. Overall, the quality of T-cell responses might be a key factor in not only disease evolution, but also chemotherapy responsiveness. Immunological parameters are potential indicators of treatment response regardless of achievement of cure. Providing tools to monitor and provide early predictions of treatment success will allow the development of new therapeutic options.

Recent clinical trials for the etiological treatment of chronic chagas disease: advances, challenges and perspectives

Chagas disease, a chronic systemic parasitosis caused by the Kinetoplastid protozoon Trypanosoma cruzi, is the first cause of cardiac morbidity and mortality in poor rural and suburban areas of Latin America and the largest parasitic disease burden in the continent, now spreading worldwide due to international migrations. A recent change in the scientific paradigm on the pathogenesis of chronic Chagas disease has led to a consensus that all T. cruzi-seropositive patients should receive etiological treatment. This important scientific advance has spurred the rigorous evaluation of the safety and efficacy of currently available drugs (benznidazole and nifurtimox) as well as novel anti-T. cruzi drug candidates in chronic patients, who were previously excluded from such treatment. The first results indicate that benznidazole is effective in inducing a marked and sustained reduction in the circulating parasites' level in the majority of these patients, but adverse effects can lead to treatment discontinuation in 10-20% of cases. Ergosterol biosynthesis inhibitors, such as posaconazole and ravuconazole, are better tolerated but their efficacy at the doses and treatment duration used in the initial studies was significantly lower; such results are probably related to suboptimal exposure and/or treatment duration. Combination therapies are a promising perspective but the lack of validated biomarkers of response to etiological treatment and eventual parasitological cures in chronic patients remains a serious challenge.

Toxoplasma gondii HLA-B*0702-restricted GRA7(20-28) peptide with adjuvants and a universal helper T cell epitope elicits CD8(+) T cells producing interferon-γ and reduces parasite burden in HLA-B*0702 mice

The ability of CD8(+) T cells to act as cytolytic effectors and produce interferon-γ (IFN-γ) was demonstrated to mediate resistance to Toxoplasma gondii in murine models because of the recognition of peptides restricted by murine major histocompatibility complex (MHC) class I molecules. However, no T gondii-specific HLA-B07-restricted peptides were proven protective against T gondii. Recently, 2 T gondii-specific HLA-B*0702-restricted T cell epitopes, GRA7(20-28) (LPQFATAAT) and GRA3(27-35) (VPFVVFLVA), displayed high-affinity binding to HLA-B*0702 and elicited IFN-γ from peripheral blood mononuclear cells of seropositive HLA-B*07 persons. Herein, these peptides were evaluated to determine whether they could elicit IFN-γ in splenocytes of HLA-B*0702 transgenic mice when administered with adjuvants and protect against subsequent challenge. Peptide-specific IFN-γ-producing T cells were identified by enzyme-linked immunosorbent spot and proliferation assays utilizing splenic T lymphocytes from human lymphocyte antigen (HLA) transgenic mice. When HLA-B*0702 mice were immunized with one of the identified epitopes, GRA7(20-28) in conjunction with a universal CD4(+) T cell epitope (PADRE) and adjuvants (CD4(+) T cell adjuvant, GLA-SE, and TLR2 stimulatory Pam(2)Cys for CD8(+) T cells), this immunization induced CD8(+) T cells to produce IFN-γ and protected mice against high parasite burden when challenged with T gondii. This work demonstrates the feasibility of bioinformatics followed by an empiric approach based on HLA binding to test this biologic activity for identifying protective HLA-B*0702-restricted T gondii peptides and adjuvants that elicit protective immune responses in HLA-B*0702 mice.

Antimalarial activity of potential inhibitors of Plasmodium falciparum lactate dehydrogenase enzyme selected by docking studies

The Plasmodium falciparum lactate dehydrogenase enzyme (PfLDH) has been considered as a potential molecular target for antimalarials due to this parasite's dependence on glycolysis for energy production. Because the LDH enzymes found in P. vivax, P. malariae and P. ovale (pLDH) all exhibit ∼90% identity to PfLDH, it would be desirable to have new anti-pLDH drugs, particularly ones that are effective against P. falciparum, the most virulent species of human malaria. Our present work used docking studies to select potential inhibitors of pLDH, which were then tested for antimalarial activity against P. falciparum in vitro and P. berghei malaria in mice. A virtual screening in DrugBank for analogs of NADH (an essential cofactor to pLDH) and computational studies were undertaken, and the potential binding of the selected compounds to the PfLDH active site was analyzed using Molegro Virtual Docker software. Fifty compounds were selected based on their similarity to NADH. The compounds with the best binding energies (itraconazole, atorvastatin and posaconazole) were tested against P. falciparum chloroquine-resistant blood parasites. All three compounds proved to be active in two immunoenzymatic assays performed in parallel using monoclonals specific to PfLDH or a histidine rich protein (HRP2). The IC₅₀ values for each drug in both tests were similar, were lowest for posaconazole (<5 µM) and were 40- and 100-fold less active than chloroquine. The compounds reduced P. berghei parasitemia in treated mice, in comparison to untreated controls; itraconazole was the least active compound. The results of these activity trials confirmed that molecular docking studies are an important strategy for discovering new antimalarial drugs. This approach is more practical and less expensive than discovering novel compounds that require studies on human toxicology, since these compounds are already commercially available and thus approved for human use.

The endless race between Trypanosoma cruzi and host immunity: lessons for and beyond Chagas disease

Infection with the protozoan parasite Trypanosoma cruzi, the agent of Chagas disease, is characterised by a variable clinical course - from symptomless cases to severe chronic disease with cardiac and/or gastrointestinal involvement. The variability in disease outcome has been attributed to host responses as well as parasite heterogeneity. In this article, we review studies indicating the importance of immune responses as key determinants of host resistance to T. cruzi infection and the pathogenesis of Chagas disease. Particular attention is given to recent studies defining the role of cognate innate immune receptors and immunodominant CD8+ T cells that recognise parasite components - both crucial for host-parasite interaction and disease outcome. In light of these studies we speculate about parasite strategies that induce a strong and long-lasting T-cell-mediated immunity but at the same time allow persistence of the parasite in the vertebrate host. We also discuss what we have learned from these studies for increasing our understanding of Chagas pathogenesis and for the design of new strategies to prevent the development of Chagas disease. Finally, we highlight recent studies employing a genetically engineered attenuated T. cruzi strain as a vaccine shuttle that elicits potent T cell responses specific to a tumour antigen and protective immunity against a syngeneic melanoma cell line.

Specific chemotherapy of Chagas disease: relevance, current limitations and new approaches

A critical review of the development of specific chemotherapeutic approaches for the management of American Trypanosomiasis or Chagas disease is presented, including controversies on the pathogenesis of the disease, the initial efforts that led to the development of currently available drugs (nifurtimox and benznidazole), limitations of these therapies and novel approaches for the development of anti-Trypanosoma cruzi drugs, based on our growing understanding of the biology of this parasite. Among the later, the most promising approaches are ergosterol biosynthesis inhibitors such as posaconazole and ravuconazole, poised to enter clinical trials for chronic Chagas disease in the short term; inhibitors of cruzipain, the main cysteine protease of T. cruzi, essential for its survival and proliferation in vitro and in vivo; bisphosphonates, metabolic stable pyrophosphate analogs that have trypanocidal activity through the inhibition of the parasite's farnesyl-pyrophosphate synthase or hexokinase; inhibitors of trypanothione synthesis and redox metabolism and inhibitors of hypoxanthine-guanine phosphoribosyl-transferase, an essential enzyme for purine salvage in T. cruzi and related organisms. Finally, the economic and political challenges faced by development of drugs for the treatment of neglected tropical diseases, which afflict almost exclusively poor populations in developing countries, are analyzed and recent potential solutions for this conundrum are discussed.

A comparative study of posaconazole and benznidazole in the prevention of heart damage and promotion of trypanocidal immune response in a murine model of Chagas disease

A comparative study was performed between the trypanocidal efficacy of and associated immune response to benznidazole and posaconazole in a murine model of Chagas disease. Both drugs led to 100% survival, suppression of parasitaemia and reduction of specific anti-Trypanosoma cruzi antibodies following chronic infection. All posaconazole-treated animals had negative haemocultures at 54 days post infection, whilst 50% of those treated with benznidazole had positive results. Although both drugs were effective in reducing parasitism and inflammation in the heart, posaconazole-treated animals had plasma enzymatic levels of cardiac lesion that were indistinguishable from those of uninfected mice, whilst for benznidazole the enzyme levels were significantly higher than those of uninfected controls 31 days after the start of treatment. Posaconazole was more effective than benznidazole in controlling spleen enlargement and unspecific splenocyte proliferation in the early acute phase, but allowed higher levels of activation of CD4(+) and CD8(+) T-cells in the late acute phase when the adaptive immune response takes control of the infection. These results support the notion that posaconazole could be superior to benznidazole for the treatment of T. cruzi infection in humans.

Synthetic Medicinal Chemistry in Chagas' Disease: Compounds at The Final Stage of "Hit-To-Lead" Phase

Chagas' disease, or American trypanosomosiasis, has been the most relevant illness produced by protozoa in Latin America. Synthetic medicinal chemistry efforts have provided an extensive number of chemodiverse hits at the "active-to-hit" stage. However, only a more limited number of these have been studied in vivo in models of Chagas' disease. Herein, we survey some of the cantidates able to surpass the "hit-to-lead" stage discussing their limitations or merit to enter in clinical trials in the short term.

Ergosterol biosynthesis and drug development for Chagas disease

This article presents an overview of the currently available drugs nifurtimox (NFX) and benznidazole (BZN) used against Trypanosoma cruzi, the aetiological agent of Chagas disease; herein we discuss their limitations along with potential alternatives with a focus on ergosterol biosynthesis inhibitors (EBI). These compounds are currently the most advanced candidates for new anti-T. cruzi agents given that they block de novo production of 24-alkyl-sterols, which are essential for parasite survival and cannot be replaced by a host's own cholesterol. Among these compounds, new triazole derivatives that inhibit the parasite's C14alpha sterol demethylase are the most promising, as they have been shown to have curative activity in murine models of acute and chronic Chagas disease and are active against NFX and BZN-resistant T. cruzi strains; among this class of compounds, posaconazole (Schering-Plough Research Institute) and ravuconazole (Eisai Company) are poised for clinical trials in Chagas disease patients in the short term. Other T. cruzi-specific EBI, with in vitro and in vivo potency, include squalene synthase, lanosterol synthase and squalene epoxidase-inhibitors as well as compounds with dual mechanisms of action (ergosterol biosynthesis inhibition and free radical generation), but they are less advanced in their development process. The main putative advantages of EBI over currently available therapies include their higher potency and selectivity in both acute and chronic infections, activity against NFX and BZN-resistant T. cruzi strains, and much better tolerability and safety profiles. Limitations may include complexity and cost of manufacture of the new compounds. As for any new drug, such compounds will require extensive clinical testing before being introduced for clinical use, and the complexity of such studies, particularly in chronic patients, will be compounded by the current limitations in the verification of true parasitological cures for T. cruzi infections.

The role of parasite persistence in pathogenesis of Chagas heart disease

Chagas disease (CD) is caused by the infection with the protozoan haemoflagellate Trypanosoma cruzi. This disease is still a great menace to public health, and is largely neglected as it affects mostly the poorest populations of Latin America. Nonetheless, there are neither effective diagnostic markers nor therapeutic options to accurately detect and efficiently cure this chronic infection. In spite of the great advances in the knowledge of the biology of natural transmission, as well as the immunobiology of the host-parasite interaction, the understanding of the pathogenesis of CD remains largely elusive. In the recent decades, a controversy in the research community has developed about the relevance of parasite persistence or autoimmune phenomena in the development of chronic cardiac pathology. One of the most notable aspects of chronic CD is the progressive deterioration of cardiac function, derived mostly from structural derangement, as a consequence of the intense inflammatory process. Here we review the evidence supporting the multifactorial nature of Chagas heart disease comprising pathogen persistence and altered host immunoregulatory mechanisms.