Trypanocidal treatment of Chagas disease

Chagas disease is a neglected parasitosis caused by the protozoan parasite Trypanosoma cruzi. This infection is present in most Latin American countries, although, due to migratory movements, it is a growing cause for concern in non-endemic countries. The only two drugs currently available for its treatment-benznidazole and nifurtimox-were marketed 50 years ago. While they are very effective for acute and recent infection, and for the prevention of maternofoetal transmission, their efficacy declines in people who have chronic infection, especially those older than 18 years of age. In the presence of visceral involvement, parasiticidal treatment is of little or no value. The safety profile of both drugs is far from ideal, with frequent adverse events and high rates of drug discontinuation, mainly in adults. So far, new drugs and new strategies have not been shown to improve the results of the current nitroimidazoles, although the results are promising. In this review, we focus on the aspects that allow clinicians to make the best use of currently available drugs. In addition, we discuss new therapeutic options and ongoing research in the field.

Trypanocidal treatment of Chagas disease

Chagas disease is a neglected parasitosis caused by the protozoan parasite Trypanosoma cruzi. This infection is present in most Latin American countries, although, due to migratory movements, it is a growing cause for concern in non-endemic countries. The only two drugs currently available for its treatment-benznidazole and nifurtimox-were marketed 50 years ago. While they are very effective for acute and recent infection, and for the prevention of maternofoetal transmission, their efficacy declines in people who have chronic infection, especially those older than 18 years of age. In the presence of visceral involvement, parasiticidal treatment is of little or no value. The safety profile of both drugs is far from ideal, with frequent adverse events and high rates of drug discontinuation, mainly in adults. So far, new drugs and new strategies have not been shown to improve the results of the current nitroimidazoles, although the results are promising. In this review, we focus on the aspects that allow clinicians to make the best use of currently available drugs. In addition, we discuss new therapeutic options and ongoing research in the field.

Gamma-glutamylcysteine synthetase and tryparedoxin 1 exert high control on the antioxidant system in Trypanosoma cruzi contributing to drug resistance and infectivity

Trypanothione (T(SH)₂) is the main antioxidant metabolite for peroxide reduction in Trypanosoma cruzi; therefore, its metabolism has attracted attention for therapeutic intervention against Chagas disease. To validate drug targets within the T(SH)₂ metabolism, the strategies and methods of Metabolic Control Analysis and kinetic modeling of the metabolic pathway were used here, to identify the steps that mainly control the pathway fluxes and which could be appropriate sites for therapeutic intervention. For that purpose, gamma-glutamylcysteine synthetase (γECS), trypanothione synthetase (TryS), trypanothione reductase (TryR) and the tryparedoxin cytosolic isoform 1 (TXN1) were separately overexpressed to different levels in T. cruzi epimastigotes and their degrees of control on the pathway flux as well as their effect on drug resistance and infectivity determined. Both experimental in vivo as well as in silico analyses indicated that γECS and TryS control T(SH)₂ synthesis by 60–74% and 15–31%, respectively. γECS overexpression prompted up to a 3.5-fold increase in T(SH)₂ concentration, whereas TryS overexpression did not render an increase in T(SH)₂ levels as a consequence of high T(SH)₂ degradation. The peroxide reduction flux was controlled for 64–73% by TXN1, 17–20% by TXNPx and 11–16% by TryR. TXN1 and TryR overexpression increased H₂O₂ resistance, whereas TXN1 overexpression increased resistance to the benznidazole plus buthionine sulfoximine combination. γECS overexpression led to an increase in infectivity capacity whereas that of TXN increased trypomastigote bursting. The present data suggested that inhibition of high controlling enzymes such as γECS and TXN1 in the T(SH)₂ antioxidant pathway may compromise the parasite's viability and infectivity.

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The trypanothione synthesis flux is primarily but not exclusively controlled by γECS.

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Tryparedoxin exerts high control on the peroxide reduction flux.

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Kinetic metabolic modeling may reliably predict the in vivo pathway behavior.

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TXN1 overexpression provides benznidazole resistance.

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γECS and TXN contribute to parasite infectivity.

Designing structural features of novel benznidazole-loaded cationic nanoparticles for inducing slow drug release and improvement of biological efficacy

Several polymers have been investigated for producing cationic nanocarriers due to their ability to cross biological barriers. Polycations such as copolymers of polymethylmethacrylate are highlighted due to their biocompatibility and low toxicity. The purpose of this study was to produce small and narrow-sized cationic nanoparticles able to overcome cell membranes and improve the biological activity of benznidazole (BNZ) in normal and cancer cells. The effect of composition and procedure parameters of the used emulsification-solvent evaporation method were controlled for this purpose. The experimental approach included particle size, polydispersity index, zeta potential, atomic force microscopy (AFM), attenuated total reflectance Fourier transforms infrared spectroscopy (ATR- FTIR), drug loading efficiency, and physical stability assays. Spherical and stable (over six weeks) sub 150nm cationic nanoparticles were optimized, with the encapsulation efficiency >80%. The used drug/copolymer ratio modulated the slow drug release, which was adjusted by the parabolic diffusion mathematical model. In addition, the ability of the cationic nanoparticles improve the BNZ uptake in the normal kidney cells (HEK 293) and the human colorectal cancer cells (HT 29) demonstrate that this novel BNZ-loaded cationic has great potential as a chemotherapeutic application of benznidazole.

Current drug therapy and pharmaceutical challenges for Chagas disease

One of the most significant health problems in the American continent in terms of human health, and socioeconomic impact is Chagas disease, caused by the protozoan parasite Trypanosoma cruzi. Infection was originally transmitted by reduviid insects, congenitally from mother to fetus, and by oral ingestion in sylvatic/rural environments, but blood transfusions, organ transplants, laboratory accidents, and sharing of contaminated syringes also contribute to modern day transmission. Likewise, Chagas disease used to be endemic from Northern Mexico to Argentina, but migrations have earned it global. The parasite has a complex life cycle, infecting different species, and invading a variety of cells - including muscle and nerve cells of the heart and gastrointestinal tract - in the mammalian host. Human infection outcome is a potentially fatal cardiomyopathy, and gastrointestinal tract lesions. In absence of a vaccine, vector control and treatment of patients are the only tools to control the disease. Unfortunately, the only drugs now available for Chagas' disease, Nifurtimox and Benznidazole, are relatively toxic for adult patients, and require prolonged administration. Benznidazole is the first choice for Chagas disease treatment due to its lower side effects than Nifurtimox. However, different strategies are being sought to overcome Benznidazole's toxicity including shorter or intermittent administration schedules-either alone or in combination with other drugs. In addition, a long list of compounds has shown trypanocidal activity, ranging from natural products to specially designed molecules, re-purposing drugs commercialized to treat other maladies, and homeopathy. In the present review, we will briefly summarize the upturns of current treatment of Chagas disease, discuss the increment on research and scientific publications about this topic, and give an overview of the state-of-the-art research aiming to produce an alternative medication to treat T. cruzi infection.

[Paediatric Chagas in a non-endemic area]

INTRODUCTION

Immigration has introduced new diseases into Spanish society, one of which is Chagas disease. Young women of childbearing age and children infected with Trypanosoma cruzi from endemic areas are at risk of developing the disease years later, and pregnant women can transmit the infection through the placenta.

METHODS

Serological screening for anti-T.cruzi antibodies was performed on all immigrant children coming from a Chagas endemic area and seen in our Pathology Unit between 2003 and 2008, as well as on newborns of T.cruzi positive infected pregnant women coming from Latin America. Two ELISA tests were used (bioelisa Chagas Biokit® with recombinant antigens, and an 'in house' ELISA with crude antigen). Patients with sufficient sample were also screened by nested PCR (TCZ3/Z4).

RESULTS

A total of 202 children, aged 1 day to 14 years old were included in the study, of whom 22 (10.8%) were diagnosed with asymptomatic infection, 5 of which were congenital as they were born in this country. All infected patients received treatment with benznidazole, with three of them currently with a serologically negative result after treatment.

CONCLUSION

Chagas disease is a new imported paediatric disease that can affect children from endemic countries, but can also be acquired in our country by vertical transmission. Therefore, we believe that it is essential to perform serological screening on all children and pregnant women in the prenatal care from endemic areas, and provide specific treatment for those infected patients, given the good results observed in the paediatric population.