An improved, PCR-based strategy for the detection ofTrypanosoma cruziin human blood samples

Use of sera cell free DNA (cfDNA) and exovesicle-DNA for the molecular diagnosis of chronic Chagas disease

Chagas disease, a neglected tropical disease, is now considered a worldwide health concern as a result of migratory movements from Central and South America to other regions that were considered free of the disease, and where the epidemiological risk is limited to transplacental transmission or blood or organ donations from infected persons. Parasite detection in chronically ill patients is restricted to serological tests that only determine infection by previous infection and not the presence of the parasite, especially in patients undergoing treatment evaluation or in newborns. We have evaluated the use of nucleic acids from both circulating exovesicles and cell-free DNA (cfDNA) from 50 samples twice randomly selected from a total of 448 serum samples from immunologically diagnosed patients in whom the presence of the parasite was confirmed by nested PCR on amplicons resulting from amplification with kinetoplastid DNA-specific primers 121F-122R. Six samples were randomly selected to quantify the limit of detection by qPCR in serum exovesicles. When the nucleic acids thus purified were assayed as a template and amplified with kinetoplastid DNA and nuclear satellite DNA primers, a 100% positivity rate was obtained for all positive samples assayed with kDNA-specific primers and 96% when SAT primers were used. However, isolation of cfDNA for Trypanosoma cruzi and amplification with SAT also showed 100% positivity. The results demonstrate that serum exovesicles contain DNA of mitochondrial and nuclear origin, which can be considered a mixed population of exovesicles of parasitic origin. The results obtained with serum samples prove that both cfDNA and Exovesicle DNA can be used to confirm parasitaemia in chronically ill patients or in samples where it is necessary to demonstrate the active presence of the parasite. The results confirm for the first time the existence of exovesicles of mitochondrial origin of the parasite in the serum of those affected by Chagas disease.

Molecular diagnosis of Trypanosoma cruzi

Chagas disease, caused by the kinetoplastid protozoan Trypanosoma cruzi, affects millions of people, most of them neglected populations. The different phases of the disease, the transmission mode and the high genetic variability of the parasite determine that molecular detection methods display different degree of success. Molecular diagnostic tests may be employed during epidemiological surveys of transmission, for early diagnosis of congenital transmission and acute infections due to oral transmission, transfusion or transplantation routes, reactivation due to immunosuppression and monitoring of treatment response in chronically infected patients receiving trypanocidal chemotherapy. This manuscript summarizes the most widely used molecular tools to detect T. cruzi infection in different epidemiological and clinical scenarios.

Commercial enzyme-linked immunosorbent assay versuspolymerase chain reaction for the diagnosis of chronic Chagas disease: a systematic review and meta-analysis

Chronic Chagas disease diagnosis relies on laboratory tests due to its clinical characteristics. The aim of this research was to review commercial enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) diagnostic test performance. Performance of commercial ELISA or PCR for the diagnosis of chronic Chagas disease were systematically searched in PubMed, Scopus, Embase, ISI Web, and LILACS through the bibliography from 1980-2014 and by contact with the manufacturers. The risk of bias was assessed with QUADAS-2. Heterogeneity was estimated with the I2 statistic. Accuracies provided by the manufacturers usually overestimate the accuracy provided by academia. The risk of bias is high in most tests and in most QUADAS dimensions. Heterogeneity is high in either sensitivity, specificity, or both. The evidence regarding commercial ELISA and ELISA-rec sensitivity and specificity indicates that there is overestimation. The current recommendation to use two simultaneous serological tests can be supported by the risk of bias analysis and the amount of heterogeneity but not by the observed accuracies. The usefulness of PCR tests are debatable and health care providers should not order them on a routine basis. PCR may be used in selected cases due to its potential to detect seronegative subjects.

Estudo longitudinal e quimioterapia específica em crianças, com doença de Chagas crônica, residentes em área de baixa endemicidade da República Argentina

Apresenta-se a avaliação clinicoepidemiológica de 95 crianças chagásicas crônicas em idades entre 1 e 14 anos moradoras de Santa Fé, Argentina, não tratadas e tratadas com nifurtimox ou benznidazol, com acompanhamento de até 24 anos. Todas tinham vários antecedentes de risco para transmissão do Trypanosoma cruzi: vetorial, congênito e/ou transfusão sangüínea. O diagnóstico da infecção foi feito através de sorologia convencional. O exame clínico foi complementado por eletrocardiograma, radiografias de tórax e, análise de sangue e urina para avaliação das funções hepáticas. No pós-tratamento, utilizaram-se técnicas idênticas às do diagnóstico, sendo que 33 crianças tiveram, também, avaliação parasitológica. Dentre 24 crianças não tratadas, 14 foram controlados por 8 a 24 anos e mantiveram sorologia positiva e o estado clínico inicial. Das 71 crianças tratadas, 49 tiveram acompanhamento de 4 a 24 anos: 14 mantiveram anticorpos anti-Trypanosoma cruzi; 6 resultados discordantes e 29 negativaram a sorologia. Destas, 9 apresentaram oscilações sorológicas, antes da negativação definitiva. A mediana do tempo de negativação pós-tratamento foi, respectivamente, de 3,5 e 8 anos para crianças de 1 a 6 e 7 a 14 anos. A percentagem de soronegativos diminuiu com a idade em que se medicou, desde 75% em <4 anos até 43% em > 9 anos. A intolerância ao tratamento foi de 3,8%. Nenhuma criança modificou seu estado clínico nesta observação.

Comparison of polymerase chain reaction methods for reliable and easy detection of congenital Trypanosoma cruzi infection

The polymerase chain reaction (PCR) is a potentially interesting diagnostic tool for detecting congenital Trypanosoma cruzi infection at birth. We have compared the sensitivity and capacity of a group of T. cruzi PCR primers in detecting the complete spectrum of known T. cruzi lineages, and to improve and simplify the detection of infection in neonatal blood. We found that the two primers, Tcz1/Tcz2 and Diaz1/Diaz2, which target the 195-basepair satellite repeat, detected all parasitic lineages with the same sensitivity. However, the intensity of the amplicon was somewhat higher with Tcz1/Tcz2. For other tested primers (nuclear DNA primers BP1/BP2, O1/O2, Pon1/Pon2, and Tca1/Tca2 and kinetoplast DNA primers S35'/S36' and 121/122), either the intensity of amplicons varied according to T. cruzi lineages or the PCR assay was less sensitive. The use of the Tcz1/Tcz2 primers, which target a tandem repetitive sequence, requires a careful determination of the appropriate amount of Taq polymerase to avoid the formation of smears and multiple amplicon bands. The Tcz1/Tcz2 primers resulted in an intense 200-basepair amplicon with DNA extracted from blood equivalent to 0.02 parasites per assay when used with a simple DNA extraction method and of a low amount of Taq polymerase from a standard PCR kit. To better assess such PCR protocol, we assayed 311 samples of neonatal blood previously tested by parasitologic methods. The reliability of our PCR test was demonstrated, since all the 18 blood samples from newborns with congenital T. cruzi infection were positive, whereas the remaining samples (30 from control newborns of uninfected mothers and 262 of 263 from babies born to infected mothers) were negative. Since our PCR method is simple, reliable, robust, and inexpensive, it appears suitable for the detection of T. cruzi infection in neonatal blood, even in laboratories that are not equipped for performing the PCR.

[Chronic Chagas' disease: from xenodiagnosis and hemoculture to polymerase chain reaction]

Although there has been an improvement in the diagnosis of chronic Chagas' disease, the low sensitivity of indirect parasitological tests is a drawback to its application in diagnosis and post-therapeutic control. Polymerase chain reaction (PCR) has limited use in routine diagnosis due to the need of specific laboratory facilities, common DNA cross-contamination, and high costs. At the same time, the high variability of PCR results found in different regions of Brazil raises some questions concerning its applicability for diagnosis. PCR's high specificity is indicative that it can be used as a confirmation method in inconclusive serology diagnosis as well as an auxiliary method in pos-therapeutic control of chronic Chagas' disease when comparing to serology and parasitological techniques. It is discussed here the applicability of molecular and indirect parasitological methods in the diagnosis and post-therapeutic control of chronic Chagas' disease based on the literature published from 1954 to 2001.