Variation in susceptibility to benznidazole in isolates derived from Trypanosoma cruzi parental strains

Fifteen Years after the Definition of Trypanosoma cruzi DTUs: What Have We Learned?

Trypanosoma cruzi, the protozoan causative of Chagas disease (ChD), exhibits striking genetic and phenotypic intraspecific diversity, along with ecoepidemiological complexity. Human-pathogen interactions lead to distinct clinical presentations of ChD. In 2009, an international consensus classified T. cruzi strains into six discrete typing units (DTUs), TcI to TcVI, later including TcBat, and proposed reproducible genotyping schemes for DTU identification. This article aims to review the impact of classifying T. cruzi strains into DTUs on our understanding of biological, ecoepidemiological, and pathogenic aspects of T. cruzi. We will explore the likely origin of DTUs and the intrinsic characteristics of each group of strains concerning genome organization, genomics, and susceptibility to drugs used in ChD treatment. We will also provide an overview of the association of DTUs with mammalian reservoirs, and summarize the geographic distribution, and the clinical implications, of prevalent specific DTUs in ChD patients. Throughout this review, we will emphasize the crucial roles of both parasite and human genetics in defining ChD pathogenesis and chemotherapy outcome.

Intra-host Trypanosoma cruzi strain dynamics shape disease progression: the missing link in Chagas disease pathogenesis

Chronic Chagasic cardiomyopathy develops years after infection in 20-40% of patients, but disease progression is poorly understood. Here, we assessed Trypanosoma cruzi parasite dynamics and pathogenesis over a 2.5-year period in naturally infected rhesus macaques. Individuals with better control of parasitemia were infected with a greater diversity of parasite strains compared to those with increasing parasitemia over time. Also, the in vivo parasite multiplication rate decreased with increasing parasite diversity, suggesting competition among strains or a stronger immune response in multiple infections. Significant differences in electrocardiographic (ECG) profiles were observed in Chagasic macaques compared to uninfected controls, suggesting early conduction defects, and changes in ECG patterns over time were observed only in macaques with increasing parasitemia and lower parasite diversity. Disease progression was also associated with plasma fibronectin degradation, which may serve as a biomarker. These data provide a novel framework for the understanding of Chagas disease pathogenesis, with parasite diversity shaping disease progression.IMPORTANCEChagas disease progression remains poorly understood, and patients at increased risk of developing severe cardiac disease cannot be distinguished from those who may remain asymptomatic. Monitoring of Trypanosoma cruzi strain dynamics and pathogenesis over 2-3 years in naturally infected macaques shows that increasing parasite diversity in hosts is detrimental to parasite multiplication and Chagasic cardiomyopathy disease progression. This provides a novel framework for the understanding of Chagas disease pathogenesis.

Novel diamides inspired by protein kinase inhibitors as anti-Trypanosoma cruzi agents: in vitro and in vivo evaluations

Background: Chagas disease is a life-threatening illness caused by Trypanosoma cruzi. The involvement of serine-/arginine-rich protein kinase in the T. cruzi life cycle is significant. Aims: To synthesize, characterize and evaluate the trypanocidal activity of diamides inspired by kinase inhibitor, SRPIN340. Material & Methods: Synthesis using a three-step process and characterization by infrared, nuclear magnetic resonance and high-resolution mass spectrometry were conducted. The selectivity index was obtained by the ratio of CC50/IC50 in two in vitro models. The most active compound, 3j, was evaluated using in vitro cytokine assays and assessing in vivo trypanocidal activity. Results: 3j activity in the macrophage J774 lineage showed an anti-inflammatory profile, and mice showed significantly reduced parasitemia and morbidity at low compound dosages. Conclusion: Novel diamide is active against T. cruzi in vitro and in vivo.

Chagas Heart Disease: Beyond a Single Complication, from Asymptomatic Disease to Heart Failure

Chagas cardiomyopathy (CC), caused by the protozoan Trypanosoma cruzi, is an important cause of cardiovascular morbidity and mortality in developing countries. It is estimated that 6 to 7 million people worldwide are infected, and it is predicted that it will be responsible for 200,000 deaths by 2025. The World Health Organization (WHO) considers Chagas disease (CD) as a Neglected Tropical Disease (NTD), which must be acknowledged and detected in time, as it remains a clinical and diagnostic challenge in both endemic and non-endemic regions and at different levels of care. The literature on CC was analyzed by searching different databases (Medline, Cochrane Central, EMBASE, PubMed, Google Scholar, EBSCO) from 1968 until October 2022. Multicenter and bioinformatics trials, systematic and bibliographic reviews, international guidelines, and clinical cases were included. The reference lists of the included papers were checked. No linguistic restrictions or study designs were applied. This review is intended to address the current incidence and prevalence of CD and to identify the main pathogenic mechanisms, clinical presentation, and diagnosis of CC.

Trypanocidal therapy among children infected by Trypanosoma cruzi. Serological and electrocardiographic changes over a mean twenty-five-years follow-up period

This study compared the serological and electrocardiographic evolution among patients with chronic T. cruzi infection treated during childhood or left untreated. A retrospective cohort study was conducted during a mean follow-up period of 25 years in 82 patients: half of them underwent treatment (nifurtimox 8, benznidazole 33) before being 15 years old, whereas the other half remained untreated. During the follow-up, negative seroconversion occurred in 92.7% of the treated children, while all the untreated ones remained positive for conventional serology. At baseline, 2 patients from each group had electrocardiographic abnormalities. During the study period, 4/41 (9.75%) and 9/41 (21.95%) of treated and untreated patients displayed an altered electrocardiogram, respectively. In multivariate analyses, the probability of developing electrocardiographic abnormalities was significantly reduced among treated patients (OR = 0.18, 95% CI = 0.04-0.79; p = 0.023). Electrocardiographic abnormalities attributable to Chagas cardiomyopathy were seen in 3 patients from the untreated group (complete right bundle branch block + left anterior fascicular block, frequent ventricular extrasystole, and left anterior fascicular block). The remarkable seronegativization seen in Benznidazole and Nifurtimox recipients underlines the parasiticidal effect of both compounds. Such demonstration along with the fact that CCC-related alterations were only present in the untreated group, reinforces the view of trypanocidal treatment in chronically T. cruzi-infected children as decreasing the risk for cardiomyopathy development.

Why do few drug delivery systems to combat neglected tropical diseases reach the market? An analysis from the technology's stages

INTRODUCTION

Many drugs used to combat schistosomiasis, Chagas disease, and leishmaniasis (SCL) have clinical limitations such as: high toxicity to the liver, kidneys and spleen; reproductive, gastrointestinal, and heart disorders; teratogenicity. In this sense, drug delivery systems (DDSs) have been described in the literature as a viable option for overcoming the limitations of these drugs. An analysis of the level of development (TRL) of patents can help in determine the steps that must be taken for promising technologies to reach the market.

AREAS COVERED

This study aimed to analyze the stage of development of DDSs for the treatment of SCL described in patents. In addition, we try to understand the main reasons why many DDSs do not reach the market. In this study, we examined DDSs for drugs indicated by WHO and treatment of SCL, by performing a search for patents.

EXPERT OPINION

In this present work we provide arguments that support the hypothesis that there is a lack of integration between academia and industry to finance and continue research, especially the development of clinical studies. We cite the translational research consortia as the potential alternative for developing DDSs to combat NTDs.

Investigation of a combination of amiodarone and itraconazole for treatment of American trypanosomiasis (Chagas disease) in dogs

OBJECTIVE

To evaluate clinical, serologic, parasitological, and histologic outcomes of dogs with naturally occurring Trypanosoma cruzi infection treated for 12 months with amiodarone and itraconazole.

ANIMALS

121 dogs from southern Texas and southern Louisiana.

PROCEDURES

Treatment group dogs (n = 105) received a combination of amiodarone hydrochloride (approx 7.5 mg/kg [3.4 mg/lb], PO, q 24 h, with or without a loading dosage protocol) and itraconazole (approx 10 mg/kg [4.5 mg/lb], PO, q 24 h, adjusted to maintain a plasma concentration of 1 to 2 μg/mL) for 12 months. Control group dogs (n = 16) received no antitrypanosomal medications. Serologic assays for anti-T cruzi antibodies, PCR assays for T cruzi DNA in blood, and physical evaluations were performed 1, 6, 9, 12, and 24 months after study initiation. Adverse events were recorded. Outcomes of interest were recorded and compared between groups.

RESULTS

86 of 105 treatment group dogs and 8 of 16 control group dogs survived and completed the study (5/19 and 6/7 deaths of treatment and control group dogs, respectively, were attributed to T cruzi infection). Mean survival time until death attributed to T cruzi was longer (23.19 vs 15.64 months) for the treatment group. Results of PCR assays were negative for all (n = 92) tested treatment group dogs (except for 1 dog at 1 time point) from 6 to 24 months after study initiation. Clinical improvement in ≥ 1 clinical sign was observed in 53 of 54 and 0 of 10 treatment and control group dogs, respectively; adverse drug events were minor and reversible.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested efficacy of this trypanocidal drug combination for the treatment of T cruzi infection in dogs.

Nanocarriers for effective delivery of benznidazole and nifurtimox in the treatment of chagas disease: A review

Neglected tropical diseases (NTDs) constitute a group of infectious diseases prevalent in countries with tropical and subtropical climate that affect the poorest individuals and produce high chronic disability associated with serious problems for the health system and socioeconomic development. Chagas disease or American trypanosomiasis is included on the NTDs list. However, even though this disease affects more than 10 million people, mostly in Latin America, causing the death of over 10,000 people every year, only two drugs are approved for its treatment, benznidazole and nifurtimox. These antiparasitic agents were developed almost half a century ago and present several biopharmaceutical disadvantages such as low aqueous solubility and permeability limiting their bioavailability. In addition, both therapeutic agents are available only as tablets and a liquid pediatric formulation is still lacking. Therefore, novel pharmaceutical strategies to optimize the pharmacotherapy of Chagas disease are urgently required. In this regard, nanotechnological approaches may be a crucial alternative for the delivery of both drugs ensuring an effective pharmacotherapy although the successful bench-to-bedside translation remains a major challenge. The present work reviews in detail the formulation and in-vitro/in-vivo analysis of different nanoformulations of nifurtimox and benznidazole in order to enhance their solubility, dissolution, bioavailability and trypanocidal activity.

Sexual reproduction in a natural Trypanosoma cruzi population

Background

Sexual reproduction provides an evolutionary advantageous mechanism that combines favorable mutations that have arisen in separate lineages into the same individual. This advantage is especially pronounced in microparasites as allelic reassortment among individuals caused by sexual reproduction promotes allelic diversity at immune evasion genes within individuals which is often essential to evade host immune systems. Despite these advantages, many eukaryotic microparasites exhibit highly-clonal population structures suggesting that genetic exchange through sexual reproduction is rare. Evidence supporting clonality is particularly convincing in the causative agent of Chagas disease, Trypanosoma cruzi, despite equally convincing evidence of the capacity to engage in sexual reproduction.

Methodology/ Principle Findings

In the present study, we investigated two hypotheses that can reconcile the apparent contradiction between the observed clonal population structure and the capacity to engage in sexual reproduction by analyzing the genome sequences of 123 T. cruzi isolates from a natural population in Arequipa, Peru. The distribution of polymorphic markers within and among isolates provides clear evidence of the occurrence of sexual reproduction. Large genetic segments are rearranged among chromosomes due to crossing over during meiosis leading to a decay in the genetic linkage among polymorphic markers compared to the expectations from a purely asexually-reproducing population. Nevertheless, the population structure appears clonal due to a high level of inbreeding during sexual reproduction which increases homozygosity, and thus reduces diversity, within each inbreeding lineage.

Conclusions/ Significance

These results effectively reconcile the apparent contradiction by demonstrating that the clonal population structure is derived not from infrequent sex in natural populations but from high levels of inbreeding. We discuss epidemiological consequences of this reproductive strategy on genome evolution, population structure, and phenotypic diversity of this medically important parasite.

The rearrangement of alleles among individuals in a population during sexual reproduction maintains high allelic diversity within individuals in a population at polymorphic genes. Allelic diversity within individuals can be particularly important for parasites as it enhances their ability to evade host immune systems. Despite the potential benefits of sexual reproduction for parasites, natural populations of the protozoan parasite—and causative agent of human Chagas disease—Trypanosoma cruzi, exhibit clonal population structures indicative of asexual reproduction. This is particularly surprising as T. cruzi has the capacity for sexual reproduction. Here, we resolve this apparent contradiction by sequencing whole genomes of 123 T. cruzi isolates from a natural population in Arequipa, Peru. Evidence of past sexual reproduction and allelic rearrangements are common in this T. cruzi population. However, the majority of sexual reproduction events occur between close relatives resulting in an apparent clonal population structure. Sexual reproduction with distant relatives in areas with greater strain diversity has the potential to affect public health by increasing diversity in immune evasion genes within individuals and enhancing within-host survival, rapidly diversifying antigens that could affect the sensitivity of serological diagnostics, and by generating diversity in pathogenicity or drug resistance.

Benznidazole and Posaconazole in Eliminating Parasites in Asymptomatic T. Cruzi Carriers: The STOP-CHAGAS Trial

BACKGROUND

Benznidazole is recommended for treatment of Chagas infection. Effects of combination therapy with benznidazole and posaconazole have not been tested in Trypanosoma cruzi carriers.

OBJECTIVES

The purpose of this study was to determine whether posaconazole alone or combined with benznidazole were superior to benznidazole monotherapy in eliminating T. cruzi parasites measured by real time polymerase chain reaction (RT-PCR) in asymptomatic Chagas carriers.

METHODS

A prospective, multicenter randomized placebo-controlled study was conducted in 120 subjects from Latin America and Spain who were randomized to 4 groups: posaconazole 400 mg twice a day (b.i.d.); benznidazole 200 mg + placebo b.i.d.; benznidazole 200 mg b.i.d. + posaconazole 400 mg b.i.d.; or placebo 10 mg b.i.d. T. cruzi deoxyribonucleic acid was detected by RT-PCR at 30, 60, 90, 120, 150, 180, and 360 days. The primary efficacy outcome is the proportion of subjects with persistent negative RT-PCR by day 180; the secondary outcome was negative RT-PCR at 360 days.

RESULTS

Only 13.3% of those receiving posaconazole and 10% receiving placebo achieved the primary outcome, compared with 80% receiving benznidazole + posaconazole and 86.7% receiving benznidazole monotherapy (p < 0.0001 vs. posaconazole/placebo). Posaconazole monotherapy or posaconazole combined with benznidazole achieved high RT-PCR conversion rates during treatment (30 days; 93.3% and 88.9% and 60 days; 90%, and 92.3%) that were similar to benznidazole (89.7% and 89.3%); all were superior to placebo or posaconazole (10% and 16.7%, p < 0.0001). This was not observed at 360 days; benznidazole + posaconazole and benznidazole monotherapy (both 96%) versus placebo (17%) and posaconazole (16%, p < 0.0001). Serious adverse events were rare (6 patients) and were observed in the benznidazole-treated patients. Permanent discontinuation was reported in 19 patients (31.7%) receiving either benznidazole monotherapy or combined with posaconazole.

CONCLUSIONS

Posaconazole demonstrated trypanostatic activity during treatment, but it is ineffective long-term in asymptomatic T. cruzi carriers. Benznidazole monotherapy is superior to posaconazole, with high RT-PCR conversion rates sustained at 1 year. Side effects lead to therapy discontinuation in 32%. No advantages were observed with combined therapy versus benznidazole monotherapy. (A Study of the Use of Oral Posaconazole [POS] in the Treatment of Asymptomatic Chronic Chagas Disease [P05267] [STOP CHAGAS]: NCT01377480).

Randomized Trial of Benznidazole for Chronic Chagas' Cardiomyopathy

BACKGROUND

The role of trypanocidal therapy in patients with established Chagas' cardiomyopathy is unproven.

METHODS

We conducted a prospective, multicenter, randomized study involving 2854 patients with Chagas' cardiomyopathy who received benznidazole or placebo for up to 80 days and were followed for a mean of 5.4 years. The primary outcome in the time-to-event analysis was the first event of any of the components of the composite outcome of death, resuscitated cardiac arrest, sustained ventricular tachycardia, insertion of a pacemaker or implantable cardioverter-defibrillator, cardiac transplantation, new heart failure, stroke, or other thromboembolic event.

RESULTS

The primary outcome occurred in 394 patients (27.5%) in the benznidazole group and in 414 (29.1%) in the placebo group (hazard ratio, 0.93; 95% confidence interval [CI], 0.81 to 1.07; P=0.31). At baseline, a polymerase-chain-reaction (PCR) assay was performed on blood samples obtained from 1896 patients; 60.5% had positive results for Trypanosoma cruzi on PCR. The rates of conversion to negative PCR results (PCR conversion) were 66.2% in the benznidazole group and 33.5% in the placebo group at the end of treatment, 55.4% and 35.3%, respectively, at 2 years, and 46.7% and 33.1%, respectively, at 5 years or more (P<0.001 for all comparisons). The effect of treatment on PCR conversion varied according to geographic region: in Brazil, the odds ratio for PCR conversion was 3.03 (95% CI, 2.12 to 4.34) at 2 years and 1.87 (95% CI, 1.33 to 2.63) at 5 or more years; in Colombia and El Salvador, the odds ratio was 1.33 (95% CI, 0.90 to 1.98) at 2 years and 0.96 (95% CI, 0.63 to 1.45) at 5 or more years; and in Argentina and Bolivia, the odds ratio was 2.63 (95% CI, 1.89 to 3.66) at 2 years and 2.79 (95% CI, 1.99 to 3.92) at 5 or more years (P<0.001 for interaction). However, the rates of PCR conversion did not correspond to effects on clinical outcome (P=0.16 for interaction).

CONCLUSIONS

Trypanocidal therapy with benznidazole in patients with established Chagas' cardiomyopathy significantly reduced serum parasite detection but did not significantly reduce cardiac clinical deterioration through 5 years of follow-up. (Funded by the Population Health Research Institute and others; ClinicalTrials.gov number, NCT00123916; Current Controlled Trials number, ISRCTN13967269.).

Comparative pathogenicity in Swiss mice of Trypanosoma cruzi IV from northern Brazil and Trypanosoma cruzi II from southern Brazil

The geographical heterogeneity of Chagas disease (ChD) is mainly caused by genetic variability of the etiological agent Trypanosoma cruzi. Our hypothesis was that the pathogenicity for mice may vary with the genetic lineage (or Discrete Typing Unit - DTU) of the parasite. To test this hypothesis, parasitological and histopathological evaluations were performed in mice inoculated with strains belonging to the DTU T. cruzi IV (TcIV) from the State of Amazonas (northern Brazil), or the DTU T. cruzi II (TcII) from the State of Paraná (southern Brazil). Groups of 10 Swiss mice were inoculated with eight strains of TcIV obtained from acute cases (7) from two outbreaks of orally acquired ChD, and from the triatomine Rhodnius robustus (1) from Amazonas; and three strains of TcII obtained from chronic patients in Paraná. We evaluated the pre-patent period, patent period, maximum peak of parasitemia, day of maximum peak of parasitemia, area under the parasitemia curve, inflammatory process, and tissue parasitism in the acute phase. TcIV was less virulent than TcII, and showed significantly (p < 0.005) lower parasitemia levels. Although the levels of tissue parasitism did not differ statistically, mice infected with TcIV displayed significantly (p < 0.001) fewer inflammatory processes than mice infected with TcII. This supported the working hypothesis, since TcIV from Amazonas was less pathogenic than TcII from Paraná; and agreed with the lower severity of human cases of ChD in the Amazon region.

Nitroheterocyclic compounds are more efficacious than CYP51 inhibitors against Trypanosoma cruzi: implications for Chagas disease drug discovery and development

Advocacy for better drugs and access to treatment has boosted the interest in drug discovery and development for Chagas disease, a chronic infection caused by the genetically heterogeneous parasite, Trypanosoma cruzi. In this work new in vitro assays were used to gain a better understanding of the antitrypanosomal properties of the most advanced antichagasic lead and clinical compounds, the nitroheterocyclics benznidazole, nifurtimox and fexinidazole sulfone, the oxaborole AN4169, and four ergosterol biosynthesis inhibitors--posaconazole, ravuconazole, EPL-BS967 and EPL-BS1246. Two types of assays were developed: one for evaluation of potency and efficacy in dose-response against a panel of T. cruzi stocks representing all current discrete typing units (DTUs), and a time-kill assay. Although less potent, the nitroheterocyclics and the oxaborole showed broad efficacy against all T. cruzi tested and were rapidly trypanocidal, whilst ergosterol biosynthesis inhibitors showed variable activity that was both compound- and strain-specific, and were unable to eradicate intracellular infection even after 7 days of continuous compound exposure at most efficacious concentrations. These findings contest previous reports of variable responses to nitroderivatives among different T. cruzi strains and further challenge the introduction of ergosterol biosynthesis inhibitors as new single chemotherapeutic agents for the treatment of Chagas disease.

Evaluation of the ELISA-F29 test as an early marker of therapeutic efficacy in adults with chronic Chagas disease

This work compared the time at which negative seroconversion was detected by conventional serology (CS) and by the ELISA-F29 test on a cohort of chronic chagasic patients treated with nifurtimox or benznidazole. A retrospective study was performed using preserved serum from 66 asymptomatic chagasic adults under clinical supervision, and bi-annual serological examinations over a mean follow-up of 23 years. Twenty nine patients received trypanocide treatment and 37 remained untreated. The ELISA-F29 test used a recombinant antigen which was obtained by expressing the Trypanosoma cruzi flagellar calcium-binding protein gene in Escherichia coli. Among the untreated patients, 36 maintained CS titers. One patient showed a doubtful serology in some check-ups. ELISA-F29 showed constant reactivity in 35 out of 37 patients and was negative for the patient with fluctuating CS. The treated patients were divided into three groups according to the CS titers: in 13 they became negative; in 12 they decreased and in four they remained unchanged. ELISA-F29 was negative for the first two groups. The time at which negativization was detected was significantly lower for the ELISA-F29 test than for CS, 14.5 ± 5.7 and 22 ± 4.9 years respectively. Negative seroconversion was observed in treated patients only. The results obtained confirm that the ELISA-F29 test is useful as an early indicator of negative seroconversion in treated chronic patients.

In vivo susceptibility to benznidazole of Trypanosoma cruzi strains from the western Brazilian Amazon

OBJECTIVE

To assess the susceptibility of Trypanosoma cruzi strains from Amazon to benznidazole.

METHODS

We studied 23 strains of T. cruzi obtained from humans in the acute phase of Chagas disease, triatomines and marsupials in the state of Amazonas and from chronic patients and triatomines in the state of Paraná, Brazil. The strains were classified as TcI (6), TcII (4) and TcIV (13). For each strain, 20 Swiss mice were inoculated: 10 were treated orally with benznidazole 100 mg/kg/day (TBZ group) for 20 consecutive days and 10 comprised the untreated control group (NT). Fresh blood examination, haemoculture (HC), PCR, and ELISA were used to monitor the cure.

RESULTS

The overall cure rate was 60.5% (109/180 mice) and varied widely among strains. The strains were classified as resistant, partially resistant or susceptible to benznidazole, irrespective of discrete typing units (DTUs), geographical origin or host. However, the TcI strains from Amazonas were significantly (P = 0.028) more sensitive to benznidazole than the TcI strains from Paraná. The number of parasitological, molecular and serological parameters that were significantly reduced by benznidazole treatment also varied among the DTUs; the TBZ group of mice inoculated with TcIV strains showed more reductions (8/9) than those with TcI and TcII strains.

CONCLUSIONS

Benznidazole resistance was observed among natural populations of the parasite in the Amazon, even in those never exposed to the drug.

Myocardial scars correlate with eletrocardiographic changes in chronic Trypanosoma cruzi infection for dogs treated with Benznidazole

OBJECTIVES

The cardiac form of Chagas disease is evidenced by a progressive cardiac inflammation that leads to myocarditis, fibrosis and electrocardiographic (ECG) conduction abnormalities. Considering these characteristics, the aim of this study was to prospectively evaluate the early ECG changes in dogs that were experimentally inoculated with Benznidazole (Bz)-susceptibly (Berenice-78) and Bz-resistant (VL-10, and AAS) Trypanosoma cruzi strains and, later, evaluate the efficacy of Bz treatment for preventing these ECG alterations.

METHODS

Electrocardiographic changes of treated and untreated animals were prospectively evaluated for up to 270 days after infection, at which point collagen (right atrium) quantification was performed.

RESULTS

All infected dogs had a high intensity of heart fibrosis (4616.00 ± 1715.82 collagen/74931 μm(2) in dogs infected with Berenice-78 strain, 5839.2 ± 1423.49 collagen/74931 μm(2) in infected by AAS and 6294.40 ± 896.04 collagen/74931 μm(2) in animals infected with VL-10 strain), while 78.57% of all infected dogs showed ECG alterations. Bz Therapy reduced or prevented fibrosis in Bz-susceptible Berenice-78 (2813.00 ± 607.13 collagen/74931 μm(2) ) and Bz-resistant AAS strains (4024 ± 1272.44 collagen/74931 μm(2) ), coincident with only 10% de ECG alterations at 270 days. However, in those animals infected with a Bz-resistant VL-10 strain, specific treatment did not alter collagen deposition (6749.5 ± 1596.35 collagen/74931 μm(2) ) and there was first atrioventricular block and chamber overload at 120 and 270 days after infection, with 75% abnormal ECG exams.

CONCLUSIONS

These findings indicate that an effective antiparasitic treatment in the early stage of Chagas disease can lead to a significant reduction in the frequency and severity of the parasite-induced cardiac disease, even if parasites are not completely eliminated.

Genetic modulation in Be-78 and Y Trypanosoma cruzi strains after long-term infection in Beagle dogs revealed by molecular markers

The genetic profile of Trypanosoma cruzi was evaluated in parasite populations isolated from Beagle dogs experimentally infected with Be-78 and Y strains that present distinct biological and genetic characteristics. Molecular characterization of the isolates obtained 30days and 2years after infection was carried out. For typing MLEE, sequence polymorphisms of the mitochondrial cytochrome oxidase subunit II gene (COII) and RAPD profiles were used. The profiles of MLEE were the same for the parental Be-78 strains as their respective isolates. However, changes of MLEE profile were observed in two T. cruzi isolates from dogs inoculated with Y strain. Changes in the mitochondrial DNA (COII) and RAPD profiles of the Y strain were also observed. The dendogram constructed by UPGMA with RAPD results indicated two major branches. Global data show that the genetic modulation in polyclonal strains during the long-term infection occurred and was strain-dependent. This study still suggests that each host (here each dog) harbors a determinate T. cruzi population that may change or be modulated throughout long-term infection. This might to hinder the observation of correlation between the genetics of T. cruzi and their biological properties and behavior in different host species due to the complexity of the parasite-host interaction in which probably the genetic background of both should be considered.

Trypanosoma cruzi benznidazole susceptibility in vitro does not predict the therapeutic outcome of human Chagas disease

Therapeutic failure of benznidazole (BZ) is widely documented in Chagas disease and has been primarily associated with variations in the drug susceptibility of Trypanosoma cruzi strains. In humans, therapeutic success has been assessed by the negativation of anti-T. cruzi antibodies, a process that may take up to 10 years. A protocol for early screening of the drug resistance of infective strains would be valuable for orienting physicians towards alternative therapies, with a combination of existing drugs or new anti-T. cruzi agents. We developed a procedure that couples the isolation of parasites by haemoculture with quantification of BZ susceptibility in the resultant epimastigote forms. BZ activity was standardized with reference strains, which showed IC₅₀ to BZ between 7.6-32 µM. The assay was then applied to isolates from seven chronic patients prior to administration of BZ therapy. The IC₅₀ of the strains varied from 15.6 ± 3-51.4 ± 1 µM. Comparison of BZ susceptibility of the pre-treatment isolates of patients considered cured by several criteria and of non-cured patients indicates that the assay does not predict therapeutic outcome. A two-fold increase in BZ resistance in the post-treatment isolates of two patients was verified. Based on the profile of nine microsatellite loci, sub-population selection in non-cured patients was ruled out.

Zanthoxylum chiloperone leaves extract: first sustainable Chagas disease treatment

ETHNOPHARMACOLOGICAL RELEVANCE

Zanthoxylum chiloperone var. angustifolium Engl. (Rutaceae) stem bark is used traditionally in Paraguay for its antiparasitic properties. Canthin-6-one is main compound isolated from Zanthoxylum chiloperone var angustifolium with broad spectrum antifungal, leishmanicidal and trypanocidal activities.

AIM OF THE STUDY

The qualitative and quantitative characterization and the isolation of main alkaloidal components of different organs of Zanthoxylum chiloperone are investigated by HPLC-UV-MS. The in vitro biological activity of each extract against trypomastigote and amastigote forms of Trypanosoma cruzi parasites were evaluated, then comparison the in vivo efficacy of the ethanolic leaves extract of Zanthoxylum chiloperone with reference drug, benznidazole, in acute Trypanosoma cruzi infected mice when administered by oral route. We have also evaluated the mutagenic and cytotoxic activity of the main component of Zanthoxylum chiloperone, i.e. canthin-6-one, by mouse bone marrow micronucleus test.

MATERIALS AND METHODS

The compositions of the ethanol extracts obtained after the maceration process were studied by HPLC-UV-MS methods. The quantitation analysis was performed by external standard method, using a calibration curve constructed utilizing solutions containing different concentrations of the reference samples. The anti-trypomastigote activity was evaluated by the lysis effect on mouse blood trypomastigotes (Y strain Trypanosoma cruzi). The anti-amastigote Trypanosoma cruzi activity was evaluated by a modified colorimetric method with chlorophenol red-β-d-galactopyranoside (CPRG). The cytotoxicity of extracts and compounds was performed on NCTC 929 cells. The in vivo efficacy of the ethanolic leaves extract of Zanthoxylum chiloperone and benznidazole, in acute Trypanosoma cruzi (two different strains) was evaluated in Trypanosoma cruzi infected mice; the drugs were administered by oral route. The mortality rates were recorded and parasitaemias in control and treated mice were determined once weekly for 70 days. The mutagenic and cytotoxic activity of the main component of Zanthoxylum chiloperone, canthin-6-one, by mouse bone marrow micronucleus test.

RESULTS

Canthin-6-one was the main compound of stem and root bark and 5-methoxy-canthin-6-one in leaves and fruits. The ethanolic leaves extract, canthin-6-one and benznidazole presented, approximately, the same level of in vitro activity against trypomastigote and amastigote forms of Trypanosoma cruzi. We have also evaluated the mutagenic and cytotoxic effects of canthin-6-one by micronucleus test in mice. This test showed any mutagenic and cytotoxic damages. The effects of oral or subcutaneous treatments at 10 mg/kg daily for 2 weeks with the ethanolic extract of leaves of Zanthoxylum chiloperone were examined in Balb/c mice infected acutely with Trypanosoma cruzi (CL or Y strain) and compared with benznidazole at 50 mg/kg for 2 weeks. In these experiments, 70 days after infection, parasitaemia and serological response were significantly reduced with the oral ethanolic extract treatment compared with reference drug.

CONCLUSIONS

This study have shown the efficacy of the leaves extract of Zanthoxylum chiloperone in reducing Trypanosoma cruzi parasitaemia in vivo assays and could be welcomed by scientific and rural communities of Paraguay because it could help them towards the use of local resources to treat an endemic infection, Chagas disease, affecting 20% of the population of this country.

Meirelles M, Urbina JA, Garzoni LR. Amiodarone inhibits Trypanosoma cruzi infection and promotes cardiac cell recovery with gap junction and cytoskeleton reassembly in vitro

We present the results of the first detailed study of the antiproliferative and ultrastructural effects of amiodarone on Trypanosoma cruzi, the causative agent of Chagas' disease. Moreover, we report the effects of this compound on the recovery of F-actin fibrils, connexin43, and contractility in T. cruzi-infected cardiac myocytes. Amiodarone is the most prescribed class III antiarrhythmic agent and is frequently used for the symptomatic treatment of Chagas' disease patients with cardiac compromise. In addition, recent studies identified its antifungal and antiprotozoal activities, which take place through Ca(2+) homeostasis disruption and ergosterol biosynthesis blockade. We tested different concentrations of amiodarone (2.5 to 10 μM) on infected primary cultures of heart muscle cells and observed a dose- and time-dependent effect on growth of the clinically relevant intracellular amastigote form of T. cruzi. Ultrastructural analyses revealed that amiodarone had a profound effect on intracellular amastigotes, including mitochondrial swelling and disorganization of reservosomes and the kinetoplast and a blockade of amastigote-trypomastigote differentiation. Amiodarone showed no toxic effects on host cells, which recovered their F-actin fibrillar organization, connexin43 distribution, and spontaneous contractility concomitant with the drug-induced eradication of the intracellular parasites. Amiodarone is, therefore, a promising compound for the development of new drugs against T. cruzi.

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.

Transcriptomic signatures of alterations in a myoblast cell line infected with four distinct strains of Trypanosoma cruzi

We examined the extent to which different Trypanosoma cruzi strains induce transcriptomic changes in cultured L(6)E(9) myoblasts 72 hours after infection with Brazil (TC I), Y (TC II), CL (TC II), and Tulahuen (TC II) strains. Expression of 6,289 distinct, fully annotated unigenes was quantified with 27,000 rat oligonucleotide arrays in each of the four replicas of all control and infected RNA samples. Considering changes greater than 1.5-fold and P values < 0.05, the Tulahuen strain was the most disruptive to host transcriptome (17% significantly altered genes), whereas the Y strain altered only 6% of the genes. The significantly altered genes in the infected cells were largely different among the strains, and only 21 genes were similarly changed by all four strains. However, myoblasts infected with different strains showed proportional overall gene-expression alterations. These results indicate that infection with different parasite strains modulates similar but not identical pathways in the host cells.

Geographical clustering of Trypanosoma cruzi I groups from Colombia revealed by low-stringency single specific primer-PCR of the intergenic regions of spliced-leader genes

A low-stringency single-primer polymerase chain reaction (LSSP-PCR) typing procedure targeted to the intergenic regions of spliced-leader genes (SL) was designed to profile Trypanosoma cruzi I stocks from endemic regions of Colombia. Comparison between SL-LSSP-PCR profiles of parasite DNA from vector faeces and cultures isolated from those faeces showed more conservative signatures than profiles using LSSP-PCR targeted to the minicircle variable regions (kDNA). This was also observed by analysing 15 parasite clones from one stock as well as serial samples of a same stock after in vitro culturing or inoculation into mice. Thus, SL-LSSP-PCR appears more appropriate than kDNA-LSSP-PCR for reliable typing of major T. cruzi I groups from in vitro cultured stocks and triatomine faeces. SL-LSSP-PCR grouped 46 of 47 T. cruzi I Colombian stocks according to their geographical procedences in four clusters: Cluster Cas from Casanare Department, Cluster Mg from Northern Magdalena department, Cluster Mom from Momposina Depression in Southern Magdalena and finally Cluster NW from northwestern Colombia, including Sucre, Chocó, Córdoba and Antioquia departments. Sequence analysis identified punctual mutations among amplicons from each cluster. Within Cluster Mg, sequence polymorphism allowed association with different sylvatic vector species. Novel SL sequences and LSSP-PCR profiles are reported from T. cruzi I infecting Eratyrus cuspidatus, Panstrongylus geniculatus and Rhodnius pallescens vectors.

Trypanosoma cruzi: acute and long-term infection in the vertebrate host can modify the response to benznidazole

We analyzed the influence of Trypanosoma cruzi maintenance in different hosts (dog and mouse) on its susceptibility to benznidazole treatment. Five T. cruzi stocks were isolated from dogs inoculated with Be-62 or Be-78 strain (both sensitive to benznidazole) 2-10 years ago, and the benznidazole sensitivity was then determined using the mouse as experimental model. The different T. cruzi stocks obtained from long-term infected dogs showed 50-90% drug resistance right after isolation. However, maintenance of these T. cruzi stocks in mice, by successive blood passages (2.5 years), led to either a decrease or stability of the drug resistance pattern and an increase in parasite virulence. We also demonstrated the effectiveness of the induction of parasitemia reactivation by cyclophosphamide immunosuppression in the evaluation of the response to the specific drug treatment.

Trypanocidal nitroimidazole derivatives: Relationships among chemical structure and genotoxic activity

Human American trypanosomiasis is resurgent in Latin Americans, and new drugs are urgently required as current medications suffer from a number of drawbacks. Some nitroheterocycles have been demonstrated to exert a potent activity against trypanosomes. However, host toxicity issues halted their development as trypanocides. As part of the efforts to develop new compounds in order to treat parasitic infections, it is important to define their structure-activity relationship. In this study, 5-nitromegazol and two of its analogues, 4-nitromegazol, and 1-methyl-5-nitro-2-imidazolecarboxaldehyde 5-nitroimidazole-thiosemicarbazone, were tested and compared for in vitro induction of DNA damage in human leukocytes by the comet assay, performed at different pHs to better identify the types of damage. Specific oxidatively generated damage to DNA was also measured by using the comet assay with endonucleases. DNA damage was found in 5-nitromegazol-treated cells: oxidative stress appeared as the main source of DNA damage. 4-Nitromegazol did not produce any significant effect, thus confirming that 4-nitroimidazoles isomers have no important biological activity. The 5-nitroimidazole-thiosemicarbazone induced DNA damage with a higher efficiency than 5-nitromegazol. The central role in the reduction process played by the acidic hydrazine proton present in the thiosemicarbazone group but not in the cyclic (thiadiazole) form can contribute to rationalise our results. Given its versatility, thiosemicarbazone moiety could be involved in different reactions with nitrogenous bases (nucleophilic and/or electrophilic attacks).

Trypanocide treatment among adults with chronic Chagas disease living in Santa Fe city (Argentina), over a mean follow-up of 21 years: parasitological, serological and clinical evolution

The efficacy of treatment with nifurtimox and/or benznidazole among adults with chronic Chagas disease with no previous electrocardiographic disturbances was evaluated over a mean follow-up of 21 years, by means of conventional serology, xenodiagnosis, clinical examination, electrocardiograms and chest X-ray. One hundred and eleven patients, between 17 and 46 years old, were studied: 54 underwent treatment (nifurtimox 27, benznidazole 27) and 57 remained untreated (control group). Xenodiagnosis was performed on 65% of them: 36/38 of the treated and 9/34 of the untreated patients had previous positive xenodiagnosis. Post-treatment, 133 xenodiagnoses were performed on 41 patients, all resulting negative. In the control group, 29 xenodiagnoses were performed on 14 patients; 2 resulted positive. Sera stored during the follow-up were simultaneously analyzed through conventional serology tests (IHA; DA-2ME; IIF). The serological evolution in the treated group was: a) 37% underwent negative seroconversion (nifurtimox 11, benznidazole 9); b) 27.8% decreased titers (nifurtimox 9, benznidazole 6), 9 showed inconclusive final serology (nifurtimox 7, benznidazole 2); c) 35.2% remained positive with constant titers (nifurtimox 7; benznidazole 12). The control group conserved the initial antibody levels during the follow-up. In the clinical evolution, 2/54 (3.7%) of the treated and 9/57 (15.8%) of the untreated patients showed electrocardiographic disturbances attributable to Chagas myocardiopathy, with a statistically relevant difference (p<0.05). Treatment caused deparasitation in at least 37% of the chronically infected adults and a protective effect on their clinical evolution.

Trypanosoma cruzi: Chemotherapeutic effects of clomipramine in mice infected with an isolate obtained from an endemic area

The susceptibility of Trypanosoma cruzi strains to nifurtimox and benznidazole has been investigated and resistant strains have been described. Some tricyclic drugs are lethal for trypomastigote and epimastigote forms of T. cruzi (Tulahuen strain) and prevent the disease in mice. We investigated whether clomipramine, a tricyclic antidepressant drug with anti-trypanothione reductase and anti-calmodulin effects, could be effective in treating Albino Swiss mice infected with trypomastigotes of a new T. cruzi isolate from a chronic patient from an endemic area of Argentina in two different treatment schedules. Both treatment schedules were effective in reducing electrocardiographic changes and preventing myocardial structural damage. The cardiac beta-receptors low affinity was compensated for by an increment in their density. This probably maintained cardiac function since 70% of the mice survived for more than 2 years even though anti-cruzipain titers remained high. These results demonstrate that clomipramine, clinically used as a neuroleptic, could be a promising trypanocidal agent for the treatment of Chagas' disease.

Etanidazole in pH-sensitive liposomes: design, characterization and in vitro/in vivo anti-Trypanosoma cruzi activity

In this work, the hydrophilic, low molecular weight and trypanocidal drug etanidazole (ETZ) was loaded in pH-sensitive liposomes (L-ETZ). Liposomes were made of dioleoyl-phosphatidylethanolamine: cholesteryl hemisuccinate (DOPE:CHEMS, 6:4, mol:mol), of 380 nm size at 14% ETZ/total lipid (w/w) ratio. To follow their uptake and intracellular fate by fluorescence microscopy, pH-sensitive liposomes were loaded with the fluorophore/quencher pair HPTS/DPX. A fast and massive delivery of the liposomal aqueous content into the cytosol of murine J774 macrophages was observed. L-ETZ vesicles were phagocytosed by both uninfected and Trypanosoma cruzi-infected macrophages. A 72% of anti-amastigote activity (AA) was demonstrated on L-ETZ-treated J774 cells, whereas the same dose of free ETZ rendered 0% AA. Endovenous administration of L-ETZ at 14 microg/mouse dose provoked significant decrease in parasitemia levels of T. cruzi-infected mice. Conversely, inoculation of a 180-fold higher dose of free ETZ failed in reducing the number of bloodstream trypomastigotes. Hence, these results point to develop systems, such as L-ETZ, designed for selective delivery of drugs to the cytoplasm of phagocytic cells, thus enhancing the efficacy of molecules considered poorly active.

Influence of the long-term Trypanosoma cruzi infection in vertebrate host on the genetic and biological diversity of the parasite

The influence of the long-term Trypanosoma cruzi infection in vertebrate host on the biological and genetic properties of the parasite was evaluated. Four T. cruzi isolates obtained from different chronic chagasic dogs infected with Berenice-78 T. cruzi strain during 2 and 7 years were comparatively analyzed. The long-term T. cruzi infection has led to alterations in parasitemia, virulence and pathogenicity of Be-78 strain for mice. These biological parameters varied from low to high in realation to the parental strain. Randomly amplified polymorphic DNA and isoenzyme profiles detected two distinct genetic groups of parasites. The first group included the parental strain and two T. cruzi isolates, and the second group the two other isolates. Interestingly, the isolates of the second group showed a reversibility of the genetic profile to the parental strain after 25 passages in mice. No correlation between the genetic groups and biological properties of the isolates was observed. Our findings confirmed the population heterogeneity of the Be-78 strain, and showed how differently it responds to the long-term infection in the same vertebrate hosts.

Treatment with benznidazole during the chronic phase of experimental Chagas' disease decreases cardiac alterations

Chagas' disease, caused by Trypanosoma cruzi infection, is one of the main causes of death due to heart failure in Latin American countries. Benznidazole, the chemotherapeutic agent most often used for the treatment of chagasic patients, is highly toxic and has limited efficacy, especially in the chronic phase of the disease. In the present study we used a mouse model of chronic Chagas' disease to investigate the effects of benznidazole treatment during the chronic phase on disease progression. The hearts of benznidazole-treated mice had decreased parasitism and myocarditis compared to the hearts of untreated chagasic mice. Both groups of Trypanosoma cruzi-infected mice had significant alterations in their electrocardiograms compared to those of the healthy mice. However, untreated mice had significantly higher cardiac conduction disturbances than benznidazole-treated mice, including intraventricular conduction disturbances, atrioventricular blocks, and extrasystoles. The levels of antibodies against T. cruzi antigens (epimastigote extract, P2beta, and trans-sialidase) as well as antibodies against peptides of the second extracellular loops of beta1-adrenergic and M2-muscarinic cardiac receptors were also lower in the sera from benznidazole-treated mice than in the sera from untreated mice. These results demonstrate that treatment with benznidazole in the chronic phase of infection prevents the development of severe chronic cardiomyopathy, despite the lack of complete parasite eradication. In addition, our data highlight the role of parasite persistence in the development of chronic Chagas' disease and reinforce the importance of T. cruzi elimination in order to decrease or prevent the development of severe chagasic cardiomyopathy.

Activity of the new triazole derivative albaconazole against Trypanosoma (Schizotrypanum) cruzi in dog hosts

Albaconazole is an experimental triazole derivative with potent and broad-spectrum antifungal activity and a remarkably long half-life in dogs, monkeys, and humans. In the present work, we investigated the in vivo activity of this compound against two strains of the protozoan parasite Trypanosoma (Schizotrypanum) cruzi, the causative agent of Chagas' disease, using dogs as hosts. The T. cruzi strains used in the study were previously characterized (murine model) as susceptible (strain Berenice-78) and partially resistant (strain Y) to the drugs currently in clinical use, nifurtimox and benznidazole. Our results demonstrated that albaconazole is very effective in suppressing the proliferation of the parasite and preventing the death of infected animals. Furthermore, the parasitological, PCR, serological, and proliferative assay results indicated parasitological cure indices of 25 and 100% among animals inoculated with T. cruzi strain Y when they were treated with albaconazole at 1.5 mg/kg of body weight/day for 60 and 90 days, respectively. On the other hand, although albaconazole given at 1.5 mg/kg/day was very effective in suppressing the proliferation of the parasite in animals infected with the Berenice-78 T. cruzi strain, no parasitological cure was observed among them, even when a longer treatment period (150 doses) was used. In conclusion, our results demonstrate that albaconazole has trypanocidal activity in vivo and is capable of inducing radical parasitological cure, although natural resistance to this compound was also indicated. Furthermore, the compound can be used in long-term treatment schemes (60 to 150 days) with minimal toxicity and thus represents a potentially useful candidate for the treatment of human Chagas' disease.

Lack of correlation between in vitro susceptibility to Benznidazole and phylogenetic diversity of Trypanosoma cruzi, the agent of Chagas disease

Chagas disease remains an important health problem in Central and South America. Nitroimidazole derivative drugs like Benznidazole are commonly used to treat Trypanosoma cruzi infection. Natural variation of drug susceptibility between various T. cruzi stocks has been proposed as a possible explanation of treatment failure. Thus, the aim of this work was to determine potential correlations between in vitro Benznidazole susceptibility of different T. cruzi stocks and their genetic diversity. For this purpose, 16 natural stocks representing the overall genetic diversity of the parasite were analysed. Genetic characterisation was assessed by both random amplified polymorphic DNA (RAPD) and multilocus enzyme electrophoresis (MLEE) analyses. Drug activity was determined by two complementary methods, the MTT-PMS micro-method and FACs analysis. The 50% inhibitory concentrations (IC(50)s) were determined. Important variation of IC(50) values (7.3-16.9 microM) among stocks belonging to different discrete typing units (DTUs) was recorded. Further, correlation analysis showed that natural susceptibility to Benznidazole in T. cruzi expressed as IC(50) level was not related with its genetic structure represented by the different DTUs. These results are discussed in relation with the proposed hypothesis establishing a link between genetic diversity and biological behaviour in T. cruzi.

The dog as model for chemotherapy of the Chagas' disease

In the present study, we investigated the role of dogs as experimental models for acute and chronic phases of Chagas' disease, before and after therapeutic treatments. Dogs were infected with Trypanosoma cruzi strains of different susceptibilities to benznidazole (Bz) and treated with the same therapeutic scheme as used for human chagasic. The treatment with Bz was able to prevent death and induced parasitological cure in 62.5% (acute phase) and 38.7% (chronic recent phase) of the tested animals. These results were similar to those reported in clinical trials for treated human patients (cured and uncured) in both phases of the disease. We also showed that parasitologic and serologic tests for monitoring the cure were similar to those obtained for human trials. In addition, Polymerase chain reaction showed the highest sensitivity when compared with hemoculture as an indicator of parasite clearance. In conclusion, the proposed experimental model should be relevant for chemotherapy studies for the control of Chagas' disease.

Follow-up of experimental chronic Chagas' disease in dogs: use of polymerase chain reaction (PCR) compared with parasitological and serological methods

In this study, the polymerase chain reaction (PCR) was compared with parasitological and serological methods to detect the infection in dogs, 5-12 years after experimental infection with Trypanosoma cruzi. The ability of parasitological methods to identify a positive animal was 22 and 11% by hemoculture and xenodiagnosis/xenoculture, respectively. On the other hand, the serological tests, including conventional serology and anti-live trypomastigote antibodies (ALTA) were positive in all infected dogs. Despite its low sensitivity, if considering only one reaction, the PCR analysis showed 100% of positivity, demonstrating the presence of parasite kDNA in all infected dogs. To identify a positive dog required at least two blood samples and up to nine repeated reactions using the same sample. Serial blood sample collection, ranging from 1 to 9, revealed that the percentage of dogs with positive PCR ranged from 67 to 100%. These findings suggested that, although the PCR is useful to detect the parasite in infected hosts, it should not be used isolated for the diagnosis of Chagas' disease and warn for the necessity of serial blood collection and re-tests. Moreover, these data validate once more the dog as a model for Chagas' disease since they demonstrate the permanence of infection by PCR, parasitological and serological methods, reaching relevant requisites for an ideal model to study this disease.