In vitro studies and preclinical evaluation of benznidazole microparticles in the acute Trypanosoma cruzi murine model.

Chagas disease is a serious parasitic infection caused by Trypanosoma cruzi. Unfortunately, the current chemotherapeutic tools are not enough to combat the infection. The aim of this study was to evaluate the trypanocidal activity of benznidazole-loaded microparticles during the acute phase of Chagas infection in an experimental murine model. Microparticles were prepared by spray-drying using copolymers derived from esters of acrylic and methacrylic acids as carriers. Dissolution efficiency of the formulations was up to 3.80-fold greater than that of raw benznidazole. Stability assay showed no significant difference (P > 0.05) in the loading capacity of microparticles for 3 years. Cell cultures showed no visible morphological changes or destabilization of the cell membrane nor haemolysis was observed in defibrinated human blood after microparticles treatment. Mice with acute lethal infection survived 100% after 30 days of treatment with benznidazole microparticles (50 mg kg-1 day-1). Furthermore, no detectable parasite load measured by quantitative polymerase chain reaction and lower levels of T. cruzi-specific antibodies by enzyme-linked immunosorbent assay were found in those mice. A significant decrease in the inflammation of heart tissue after treatment with these microparticles was observed, in comparison with the inflammatory damage observed in both infected mice treated with raw benznidazole and untreated infected mice. Therefore, these polymeric formulations are an attractive approach to treat Chagas disease.

Tamoxifen acts on Trypanosoma cruzi sphingolipid pathway triggering an apoptotic death process.

This study shows the effects of tamoxifen, a known estrogen receptor antagonist used in the treatment of breast cancer, on the sphingolipid pathway of Trypanosoma cruzi, searching for potential chemotherapeutic targets. A dose-dependent epimastigote growth inhibition at increasing concentration of tamoxifen was determined. In blood trypomastigotes, treatment with 10 µM showed 90% lysis, while 86% inhibition of intracellular amastigote development was obtained using 50 µM. Lipid extracts from treated and non-treated metabolically labelled epimastigotes evidenced by thin layer chromatography different levels of sphingolipids and MALDI-TOF mass spectrometry analysis assured the identity of the labelled species. Comparison by HPLC-ESI mass spectrometry of lipids, notably exhibited a dramatic increase in the level of ceramide in tamoxifen-treated parasites and a restrained increase of ceramide-1P and sphingosine, indicating that the drug is acting on the enzymes involved in the final breakdown of ceramide. The ultrastructural analysis of treated parasites revealed characteristic morphology of cells undergoing an apoptotic-like death process. Flow cytometry confirmed cell death by an apoptotic-like machinery indicating that tamoxifen triggers this process by acting on the parasitic sphingolipid pathway.

Involvement of sulfates from cruzipain, a major antigen of Trypanosoma cruzi, in the interaction with immunomodulatory molecule Siglec-E.

In order to investigate the involvement of sulfated groups in the Trypanosoma cruzi host-parasite relationship, we studied the interaction between the major cysteine proteinase of T. cruzi, cruzipain (Cz), a sulfate-containing sialylated molecule and the sialic acid-binding immunoglobulin like lectin-E (Siglec-E). To this aim, ELISA, indirect immunofluorescence assays and flow cytometry, using mouse Siglec-E-Fc fusion molecules and glycoproteins of parasites, were performed. Competition assays verified that the lectins, Maackia amurensis II (Mal II) and Siglec-E-Fc, compete for the same binding sites. Taking into account that Mal II binding remains unaltered by sulfation, we established this lectin as sialylation degree control. Proteins of an enriched microsomal fraction showed the highest binding to Siglec-E as compared with those from the other parasite subcellular fractions. ELISA assays and the affinity purification of Cz by a Siglec-E column confirmed the interaction between both molecules. The significant decrease in binding of Siglec-E-Fc to Cz and to its C-terminal domain (C-T) after desulfation of these molecules suggests that sulfates contribute to the interaction between Siglec-E-Fc and these glycoproteins. Competitive ELISA assays confirmed the involvement of sulfated epitopes in the affinity between Siglec-E and Cz, probably modified by natural protein environment. Interestingly, data from flow cytometry of untreated and chlorate-treated parasites suggested that sulfates are not primary receptors, but enhance the binding of Siglec-E to trypomastigotic forms. Altogether, our findings support the notion that sulfate-containing sialylated glycoproteins interact with Siglec-E, an ortholog protein of human Siglec-9, and might modulate the immune response of the host, favoring parasitemia and persistence of the parasite.

Solanesyl diphosphate synthase, an enzyme of the ubiquinone synthetic pathway, is required throughout the life cycle of Trypanosoma brucei.

Ubiquinone 9 (UQ9), the expected product of the long-chain solanesyl diphosphate synthase of Trypanosoma brucei (TbSPPS), has a central role in reoxidation of reducing equivalents in the mitochondrion of T. brucei. The ablation of TbSPPS gene expression by RNA interference increased the generation of reactive oxygen species and reduced cell growth and oxygen consumption. The addition of glycerol to the culture medium exacerbated the phenotype by blocking its endogenous generation and excretion. The participation of TbSPPS in UQ synthesis was further confirmed by growth rescue using UQ with 10 isoprenyl subunits (UQ10). Furthermore, the survival of infected mice was prolonged upon the downregulation of TbSPPS and/or the addition of glycerol to drinking water. TbSPPS is inhibited by 1-[(n-oct-1-ylamino)ethyl] 1,1-bisphosphonic acid, and treatment with this compound was lethal for the cells. The findings that both UQ9 and ATP pools were severely depleted by the drug and that exogenous UQ10 was able to fully rescue growth of the inhibited parasites strongly suggest that TbSPPS and UQ synthesis are the main targets of the drug. These two strategies highlight the importance of TbSPPS for T. brucei, justifying further efforts to validate it as a new drug target.

Cruzipain Sulfotopes-Specific Antibodies Generate Cardiac Tissue Abnormalities and Favor Trypanosoma cruzi Infection in the BALB/c Mice Model of Experimental Chagas Disease.

Trypanosoma cruzi cruzipain (Cz) bears a C-terminal domain (C-T) that contains sulfated epitopes "sulfotopes" (GlcNAc6S) on its unique N-glycosylation site. The effects of in vivo exposure to GlcNAc6S on heart tissue ultrastructure, immune responses, and along the outcome of infection by T. cruzi, were evaluated in a murine experimental model, BALB/c, using three independent strategies. First, mice were pre-exposed to C-T by immunization. C-T-immunized mice (C-TIM) showed IgG2a/IgG1 <1, induced the production of cytokines from Th2, Th17, and Th1 profiles with respect to those of dC-TIM, which only induced IL-10 respect to the control mice. Surprisingly, after sublethal challenge, both C-TIM and dC-TIM showed significantly higher parasitemia and mortality than the control group. Second, mice exposed to BSA-GlcNAc6S as immunogen (BSA-GlcNAc6SIM) showed: severe ultrastructural cardiac alterations while BSA-GlcNAcIM conserved the regular tissue architecture with slight myofibril changes; a strong highly specific humoral-immune-response reproducing the IgG-isotype-profile obtained with C-TIM; and a significant memory-T-cell-response demonstrating sulfotope-immunodominance with respect to BSA-GlcNAcIM. After sublethal challenge, BSA-GlcNAc6SIM showed exacerbated parasitemias, despite elevated IFN-γ levels were registered. In both cases, the abrogation of ultrastructural alterations when using desulfated immunogens supported the direct involvement of sulfotopes and/or indirect effect through their specific antibodies, in the induction of tissue damage. Finally, a third strategy using a passive transference of sulfotope-specific antibodies (IgG-GlcNAc6S) showed the detrimental activity of IgG-GlcNAc6S on mice cardiac tissue, and mice treated with IgG-GlcNAc6S after a sublethal dose of T. cruzi, surprisingly reached higher parasitemias than control groups. These findings confirmed the indirect role of the sulfotopes, via their IgG-GlcNAc6S, both in the immunopathogenicity as well as favoring T. cruzi infection.

Elucidating the impact of low doses of nano-formulated benznidazole in acute experimental Chagas disease.

BACKGROUND: Chagas disease is a neglected parasitic infection caused by the protozoan Trypanosoma cruzi (T. cruzi) that affects more than 6 million people, mainly in Latin America. Benznidazole is still the drug of choice in many countries to treat it in spite of its dosage regimen and adverse side effects such as such as allergic dermatitis, peripheral neuropathy and anorexia. Thus, novel, safer, and more efficacious treatments for such neglected infection are urgently required. METHODOLOGY: In this study, the efficacy of orally administered low doses of benznidazole (BNZ) nanoparticles was evaluated during the acute phase in mice infected with T. cruzi Nicaragua (TcN) that were immunosuppressed during the chronic stage of the disease. Moreover, the production of T. cruzi-specific antibodies, cardiac tissue inflammation and reactive oxygen species generation by Vero cells treated with both BNZ nanoparticles (BNZ-nps) and raw BNZ (R-BNZ) were also evaluated. PRINCIPAL FINDINGS: T. cruzi infected mice treated with 10, 25 or 50 mg/kg/day of BNZ-nps survived until euthanasia (92 days post infection (dpi)), while only 15% of infected untreated mice survived until the end of the experiment. PCR analysis of blood samples taken after induction of immunosuppression showed that a dosage of 25 mg/kg/day rendered 40% of the mice PCR-negative. The histological analysis of heart tissue showed a significant decrease in inflammation after treatments with 25 and 50 mg/kg/day, while a similar inflammatory damage was observed in both infected mice treated with R-BNZ (50 mg/kg/day) and untreated mice. In addition, only BNZ-nps treated mice led to lower levels of T. cruzi-specific antibodies to 50-100%. Finally, mammalian Vero cells treated with BNZ-nps or R-BNZ lead to a significant increase in ROS production. CONCLUSIONS: Based on these findings, this research highlights the in-vitro/in-vivo efficacy of nanoformulated BNZ against T. cruzi acute infections in immunosuppressed and non-immunosuppressed mice and provides further evidence for the optimization of dosage regimens to treat Chagas disease.

Promising Efficacy of Benznidazole Nanoparticles in Acute Trypanosoma cruzi Murine Model: In-Vitro and In-Vivo Studies.

The aim of this study was to evaluate the effectiveness of benznidazole nanoparticles (BNZ-nps) on trypomastigote forms and on intracellular infection in mammalian cells and primary cardiac myocyte cells. Its effectiveness was also evaluated on acute Trypanosoma cruzi Nicaragua mice infection. Trypomastigotes from culture were treated with different concentrations of BNZ-nps to determine the drug concentration that lyses 50% of trypomastigotes (LC50). Infected mammalian cells were incubated with different concentrations of BNZ-nps to determine the percentage of amastigote inhibition. C3H/HeN mice with lethal acute infection were treated with 10, 25, and 50 mg/kg/day of BNZ-nps for 30 and 15 days to control the survival rate of animals. BNZ-nps having a mean particle size of 63.3 nm, a size distribution of 3.35, and a zeta potential of -18.30 were successfully prepared using poloxamer 188 as a stabilizer. BNZ-nps 25 and 50 µg/mL showed no significant differences in the percentage of inhibition of infected mammalian cells. Infected mice treated with BNZ-nps (50, 25, and 10 mg/kg/day) for 30 days and with BNZ-nps (50 and 25 mg/kg/day) for 15 days presented a 100% survival, whereas the animals treated with 10 mg/kg/day for 15 days of BNZ-nps showed a 70% survival rate. The results obtained demonstrate, for the first time, that benznidazole nanoparticles are a useful and attractive approach to treat Chagas disease in infected mice.

Benzophenone-based farnesyltransferase inhibitors with high activity against Trypanosoma cruzi.

Less toxic drugs are needed to combat the human parasite Trypanosoma cruzi (Chagas's disease). One novel target for antitrypanosomal drug design is farnesyltransferase. Several farnesyltransferase inhibitors based on the benzophenone scaffold were assayed in vitro and in vivo with the parasite. The common structural feature of all inhibitors is an amino function which can be protonated. Best in vitro activity (LC50 values 1 and 10 nM, respectively) was recorded for the R-phenylalanine derivative 4a and for the N-propylpiperazinyl derivative 2f. These inhibitors showed no cytotoxicity to cells. When tested in vivo, the survival rates of infected animals receiving the inhibitors at 7 mg/kg body weight/day were 80 and 60% at day 115 postinfection, respectively.

Effects of chlorate on the sulfation process of Trypanosoma cruzi glycoconjugates. Implication of parasite sulfates in cellular invasion.

Sulfation, a post-translational modification which plays a key role in various biological processes, is inhibited by competition with chlorate. In Trypanosoma cruzi, the agent of Chagas' disease, sulfated structures have been described as part of glycolipids and we have reported sulfated high-mannose type oligosaccharides in the C-T domain of the cruzipain (Cz) glycoprotein. However, sulfation pathways have not been described yet in this parasite. Herein, we studied the effect of chlorate treatment on T. cruzi with the aim to gain some knowledge about sulfation metabolism and the role of sulfated molecules in this parasite. In chlorate-treated epimastigotes, immunoblotting with anti-sulfates enriched Cz IgGs (AS-enriched IgGs) showed Cz undersulfation. Accordingly, a Cz mobility shift toward higher isoelectric points was observed in 2D-PAGE probed with anti-Cz antibodies. Ultrastructural membrane abnormalities and a significant decrease of dark lipid reservosomes were shown by electron microscopy and a significant decrease in sulfatide levels was confirmed by TLC/UV-MALDI-TOF-MS analysis. Altogether, these results suggest T. cruzi sulfation occurs via PAPS. Sulfated epitopes in trypomastigote and amastigote forms were evidenced using AS-enriched IgGs by immunoblotting. Their presence on trypomastigotes surface was demonstrated by flow cytometry and IF with Cz/dCz specific antibodies. Interestingly, the percentage of infected cardiac HL-1 cells decreased 40% when using chlorate-treated trypomastigotes, suggesting sulfates are involved in the invasion process. The same effect was observed when cells were pre-incubated with dCz, dC-T or an anti-high mannose receptor (HMR) antibody, suggesting Cz sulfates and HMR are also involved in the infection process by T. cruzi.

Predictive role of polymerase chain reaction in the early diagnosis of congenital Trypanosoma cruzi infection.

The efficacy of specific chemotherapy in congenital Chagas disease before the first year of life ranges between 90 and 100%. Between this age and 15 years of age, the efficacy decreases to around 60%. Therefore, early infection detection is a priority in vertical transmission. The aim of this work was to assess whether polymerase chain reaction (PCR) plays a predictive role in the diagnosis of congenital Chagas disease as compared to conventional parasitological and serological methods. To this end, we studied a total of 468 children born to Trypanosoma cruzi seroreactive mothers came from Argentina, Bolivia and Paraguay, who lived in the city of Buenos Aires and suburban areas (Argentina), a non-endemic area of this country. These children were assessed by PCR from 2004 to 2009 with the specific primers Tcz1 and Tcz2, and 121 and 122. PCR allowed detecting 49 T. cruzi-positive children. Eight of these 49 children were excluded from the analysis: six because they did not complete follow-up and two because the first control was performed after 12 months of age. Parasitological methods allowed detecting 25 positive children, 7 of whom had been earlier diagnosed by PCR (1.53±2.00 vs. 6.71±1.46 months; p=0.0002). Serological methods allowed detecting 16 positive children, 12 of whom had been earlier diagnosed by PCR (1.46±1.48 vs. 11.77±4.40 months; p<0.0001). None of the children negative by PCR was positive by serological or parasitological methods. This study shows that PCR allows early diagnosis in congenital Chagas disease. At present, an early positive PCR is not indicative for treatment. However, a positive PCR would alert the health system to search only those infected infants diagnosed by early PCR and thus generate greater efficiency in the diagnosis and treatment of congenital T. cruzi infection.

Polyfunctional T cell responses in children in early stages of chronic Trypanosoma cruzi infection contrast with monofunctional responses of long-term infected adults.

BACKGROUND: Adults with chronic Trypanosoma cruzi exhibit a poorly functional T cell compartment, characterized by monofunctional (IFN-γ-only secreting) parasite-specific T cells and increased levels of terminally differentiated T cells. It is possible that persistent infection and/or sustained exposure to parasites antigens may lead to a progressive loss of function of the immune T cells. METHODOLOGY/PRINCIPAL FINDINGS: To test this hypothesis, the quality and magnitude of T. cruzi-specific T cell responses were evaluated in T. cruzi-infected children and compared with long-term T. cruzi-infected adults with no evidence of heart failure. The phenotype of CD4(+) T cells was also assessed in T. cruzi-infected children and uninfected controls. Simultaneous secretion of IFN-γ and IL-2 measured by ELISPOT assays in response to T. cruzi antigens was prevalent among T. cruzi-infected children. Flow cytometric analysis of co-expression profiles of CD4(+) T cells with the ability to produce IFN-γ, TNF-α, or to express the co-stimulatory molecule CD154 in response to T. cruzi showed polyfunctional T cell responses in most T. cruzi-infected children. Monofunctional T cell responses and an absence of CD4(+)TNF-α(+)-secreting T cells were observed in T. cruzi-infected adults. A relatively high degree of activation and differentiation of CD4(+) T cells was evident in T. cruzi-infected children. CONCLUSIONS/SIGNIFICANCE: Our observations are compatible with our initial hypothesis that persistent T. cruzi infection promotes eventual exhaustion of immune system, which might contribute to disease progression in long-term infected subjects.

An anionic synthetic sugar containing 6-SO3 -NAcGlc mimics the sulfated cruzipain epitope that plays a central role in immune recognition.

Cruzipain (Cz), the major cysteine proteinase of Trypanosoma cruzi, is a glycoprotein that contains sulfated high-mannose-type oligosaccharides. We have previously determined that these sulfate groups are targets of specific immune responses. In order to evaluate the structural requirements for antibody recognition of Cz, a systematic structure-activity study of the chemical characteristics needed for antibody binding to the Cz sulfated epitope was performed by immunoassays. With this aim, different synthesized molecules were coupled to the proteins BSA and aprotinin and confronted with (a) mouse sera specific for Cz and its carboxy-terminal (C-T) domain, (b) antibodies raised in rabbits immunized with Cz and its C-terminal domain and (c) IgGs purified from human Chagas disease sera. Our results indicate that a glucosamine containing an esterifying sulfate group in position O-6 and an N-acetyl group was the preferred epitope for the immune recognition of sera specific for Cz and its C-T domain. Although to a minor extent, other anionic compounds bearing sulfate groups in different positions and number as well as different anionic charged groups including carboxylated or phosphorylated monosaccharides, disaccharides and oligosaccharides were recognized. In conclusion, we found that synthetic anionic sugar conjugates containing N-acetyl d-glucosamine-6-sulfate sodium salt (GlcNAc6S) competitively inhibit the binding of affinity purified rabbit anti-C-T IgG to the C-T extension of Cz. Extending these findings to the context of natural infection, immune assays performed with Chagas disease serum confirmed that the structure of synthetic GlcNAc6S mimics the N-glycan-linked sulfated epitope displayed in the C-T domain of Cz.

Trypanosoma cruzi: in vitro and in vivo antiproliferative effects of epigallocatechin gallate (EGCg).

The trypanocidal activity of catechins on Trypanosoma cruzi bloodstream trypomastigotes has been previously reported. Herein, we present the effect of epigallocatechin gallate (EGCg) on parasitemia and survival in a murine model of acute Chagas' disease as well as on the epimastigote form of the parasite. Upon intraperitoneal administration of daily doses of 0.8 mg/kg/day of EGCg for 45 days, mice survival rates increased from 11% to 60%, while parasitemia diminished to 50%. No side effects were observed in EGCg-treated animals. Fifty percent inhibition of epimastigotes growth was achieved with 311 microM EGCg 120 h after drug addition. No lysis, total culture growth inhibition or morphological changes were observed upon addition of 1-3mM EGCg at 24 h. This treatment also produced oligosomal fragmentation of epimastigotes DNA, suggesting a programmed cell death (PCD)-like process. All these findings point out EGCg as a potential new lead compound for chemotherapy of Chagas' disease.

Anti-Trypanosoma cruzi activity of green tea (Camellia sinensis) catechins.

The trypanocidal action of green tea catechins against two different developmental stages of Trypanosoma cruzi is reported for the first time. This activity was assayed with the nonproliferative bloodstream trypomastigote and with the intracellular replicative amastigote parasite forms. An ethyl acetate fraction from Camellia sinensis green tea leaves, which contains most of the polyphenolic compounds and the maximal trypanocidal activity, was obtained by fractionation of the aqueous extract with organic solvents. The active compounds present in this extract were further purified by LH-20 column chromatography and were identified by high-performance liquid chromatography analysis with a photo diode array detector and gas chromatography coupled to mass spectroscopy. The following flavan-3-ols derivatives, known as catechins, were identified: catechin, epicatechin, gallocatechin, epigallocatechin, catechin gallate, epicatechin gallate, gallocatechin gallate, and epigallocatechin gallate. The purified compounds lysed more than 50% of the parasites present in the blood of infected BALB/c mice at concentrations as low as 0.12 to 85 pM. The most active compounds were gallocatechin gallate and epigallocatechin gallate, with minimal bactericidal concentrations that inhibited 50% of isolates tested of 0.12 and 0.53 pM, respectively. The number of amastigotes in infected Vero cells decreased by 50% in the presence of each of these compounds at 100 nM. The effects of the catechins on the recombinant T. cruzi arginine kinase, a key enzyme in the energy metabolism of the parasite, were assayed. The activity of this enzyme was inhibited by about 50% by nanomolar concentrations of catechin gallate or gallocatechin gallate, whereas the other members of the group were less effective. On the basis of these results, we suggest that these compounds could be used to sterilize blood and, eventually, as therapeutic agents for Chagas' disease.

Trypanocidal effect of SKF525A, proadifen, on different developmental forms of Trypanosoma cruzi

SKF525A, an inhibitor and inducer of cytochrome P450, was tested on different developmental stages of Trypanosoma cruzi. Growth, motility and structure of epimastigotes, motility and infectivity of trypomastigotes, and infectivity of trypomastigotes to Vero cells in culture were abolished by the drug at 10-100 muM concentration. When blood from infected mice was treated with the drug, and used to infect 8 day-old-mice, no parasites were observed at 0.6-1 mM, and all animals survived. Blood cell morphology was well preserved, and the sleeping time of pentobarbital-treated mice inoculated with the same amount of drug was not increased. The present results suggest that SKF525A or other related inhibitors of cytochrome P450 coned be tested as an additive for blood sterilization in blood banks.

Bases moleculares e inmunológicas para el desarrollo de una vacuna contra la enfermedad de Chagas / Molecular and immunological bases for the development of a vaccine against Chagas'disease

Diferentes fracciones subcelulares de epimastigotes de T.cruzi fueron ensayadas en su capacidad de inducir protección o agresión en animales experimentales. La fracción flagelar (F) tuvo las mejores propiedades protectoras, sin efectos agresivos sobre los tejidos. Se prepararon varios anticuerpos monoclonales contra esta fracción. Dos de ellos, FCH-F8-1 y 4, mostraron capacidad de neutralizar la infectividad de tripomastigotes sanguíneos, de producir la lisis mediada por complemento de tripomastigotes de cultivo y de reconocer antígenos de la superfície de ambas formas epi y tripomastigotes. El anticuerpo FCH-F8-1, reconoce por inmunoprecipitación, una proteína de 85 kDa en tripomastigotes, mientras que en "blotting" reaccionó con una molécula de 43 kDa, en ambas formas del parásito. El otro anticuerpo, FCH-F8-4 reaccionó por esta última técnica, con varias proteínas de peso molecular entre 50 y 150 kDa, en epimastigotes y sólo con dos (15 y 48 kDa) en tripomastigotes. Ratones inmunizados con antígenos purificados por cromatografia de afinidad usando FCH-F8-4, fueron protegidos contra el desafio de formas infectantes. En una biblioteca de ADNc de epimastigotes de T. cruzi construída en el vector I gt11 se detectaron varios clones, tres con FCH-F8-4 y dos con FCH-F8-1. Dos clones, uno de cada grupo fueron estudiados, y (FCH-F8-1) 1 y (FCH-F8-4) 1. El tamaño de los insertos para ambos fue de 150 pares de bases y utilizados como sondas detectaron ARNm de epimastigotes de 3,5 y 5,0...