In this "Critical Review" we made a historical introduction of drugs assayed against Chagas disease beginning in 1912 with the works of Mayer and Rocha Lima up to the experimental use of nitrofurazone. In the beginning of the 70s, nifurtimox and benznidazole were introduced for clinical treatment, but results showed a great variability and there is still a controversy about their use for chronic cases. After the introduction of these nitroheterocycles only a few compounds were assayed in chagasic patients. The great advances in vector control in the South Cone countries, and the demonstration of parasite in chronic patients indicated the urgency to discuss the etiologic treatment during this phase, reinforcing the need to find drugs with more efficacy and less toxicity. We also review potential targets in the parasite and present a survey about new classes of synthetic and natural compounds studied after 1992/1993, with which we intend to give to the reader a general view about experimental studies in the area of the chemotherapy of Chagas disease, complementing the previous papers of Brener (1979) and De Castro (1993).

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A critical review on Chagas disease chemotherapy.

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(96)04128-1.pdf

Randomised trial of efficacy of benznidazole in treatment of early Trypanosoma cruzi infection

BACKGROUND: A century after its discovery, Chagas disease still represents a major neglected tropical threat. Accurate diagnostics tools as well as surrogate markers of parasitological response to treatment are research priorities in the field. The purpose of this study was to evaluate the performance of PCR methods in detection of Trypanosoma cruzi DNA by an external quality evaluation. METHODOLOGY/FINDINGS: An international collaborative study was launched by expert PCR laboratories from 16 countries. Currently used strategies were challenged against serial dilutions of purified DNA from stocks representing T. cruzi discrete typing units (DTU) I, IV and VI (set A), human blood spiked with parasite cells (set B) and Guanidine Hidrochloride-EDTA blood samples from 32 seropositive and 10 seronegative patients from Southern Cone countries (set C). Forty eight PCR tests were reported for set A and 44 for sets B and C; 28 targeted minicircle DNA (kDNA), 13 satellite DNA (Sat-DNA) and the remainder low copy number sequences. In set A, commercial master mixes and Sat-DNA Real Time PCR showed better specificity, but kDNA-PCR was more sensitive to detect DTU I DNA. In set B, commercial DNA extraction kits presented better specificity than solvent extraction protocols. Sat-DNA PCR tests had higher specificity, with sensitivities of 0.05-0.5 parasites/mL whereas specific kDNA tests detected 5.10(-3) par/mL. Sixteen specific and coherent methods had a Good Performance in both sets A and B (10 fg/µl of DNA from all stocks, 5 par/mL spiked blood). The median values of sensitivities, specificities and accuracies obtained in testing the Set C samples with the 16 tests determined to be good performing by analyzing Sets A and B samples varied considerably. Out of them, four methods depicted the best performing parameters in all three sets of samples, detecting at least 10 fg/µl for each DNA stock, 0.5 par/mL and a sensitivity between 83.3-94.4%, specificity of 85-95%, accuracy of 86.8-89.5% and kappa index of 0.7-0.8 compared to consensus PCR reports of the 16 good performing tests and 63-69%, 100%, 71.4-76.2% and 0.4-0.5, respectively compared to serodiagnosis. Method LbD2 used solvent extraction followed by Sybr-Green based Real time PCR targeted to Sat-DNA; method LbD3 used solvent DNA extraction followed by conventional PCR targeted to Sat-DNA. The third method (LbF1) used glass fiber column based DNA extraction followed by TaqMan Real Time PCR targeted to Sat-DNA (cruzi 1/cruzi 2 and cruzi 3 TaqMan probe) and the fourth method (LbQ) used solvent DNA extraction followed by conventional hot-start PCR targeted to kDNA (primer pairs 121/122). These four methods were further evaluated at the coordinating laboratory in a subset of human blood samples, confirming the performance obtained by the participating laboratories. CONCLUSION/SIGNIFICANCE: This study represents a first crucial step towards international validation of PCR procedures for detection of T. cruzi in human blood samples.

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International study to evaluate PCR methods for detection of Trypanosoma cruzi DNA in blood samples from Chagas disease patients.

Gastrointestinal dysfunction is a major problem for many patients with chronic Chagas' disease, as are cardiac dysrhythmias and cardiomyopathy. The underlying anatomic abnormality in these patients is a denervation of the gastrointestinal tract. This process of nerve destruction usually develops insidiously over many years, and it is highly variable in terms of its extent in individual patients as well as in the segments of the gastrointestinal tract that are most affected. Megaesophagus is the most common manifestation of gastrointestinal Chagas disease, and mechanical dilation of the esophageal sphincter or surgery in advanced cases usually give satisfactory relief of symptoms. Megacolon, particularly of the sigmoid segment, is also common in patients with chronic T. cruzi infections, and its presence can be complicated by fecal impaction or sigmoid volvulus. Patients with advanced megacolon who have resections of the sigmoid colon and most of the rectum generally do well postoperatively.

American Trypanosomiasis (Chagas disease).

Identification of six Trypanosoma cruzi phylogenetic lineages by random amplified polymorphic DNA and multilocus enzyme electrophoresis.

Trypanosoma cruzi specific sequences were amplified by the polymerase chain reaction from total blood of human chagasic patients and normal individuals. A 330 bp fragment originating from kinetoplast DNA was specifically detected in most chagasic individuals. We tested the sensitivity and specificity of this method in normal and affected individuals attending the Evandro Chagas Hospital, Rio de Janeiro. The results of these tests were compared with serological diagnosis performed using standard techniques, and in some cases with xenodiagnosis. We found that none of the serologically negative individuals gave any specific amplification product, whereas 55 out of 61 patients previously serodiagnosed as chagasic were positive using the PCR method (sensitivity: 90%). Xenodiagnosis, which is currently considered to be the most sensitive parasitological technique for Chagas' disease diagnosis, detected only 12 out of 28 serologically positive patients (sensitivity: 43%). The usefulness of the PCR method was further investigated with chagasic patients who had received anti-parasite treatment with benznidazole. It has always been difficult to evaluate the incidence of cure in such cases by serology, since a humoral response against T. cruzi antigens may remain for years even in the absence of the parasite. We observed a positive amplification result in only 9 out of 32 treated patients who remained reactive when tested using classical serology. These observations suggest that PCR is the most sensitive technique available for direct detection of T. cruzi in chagasic patients and that it can be a very useful instrument for the follow-up of patients after specific treatment.

Vanni Cm

Papers

Polymerase chain reaction detection of trypanosoma cruzi in human blood samples as a tool for diagnosis and treatment evaluation