Monitoring the efficacy of specific treatment in chronic Chagas disease by polymerase chain reaction and flow cytometry analysis

Detection and Quantification of Viable and Nonviable Trypanosoma cruzi Parasites by a Propidium Monoazide Real-Time Polymerase Chain Reaction Assay

Molecular techniques based on real-time polymerase chain reaction (qPCR) allow the detection and quantification of DNA but are unable to distinguish between signals from dead or live cells. Because of the lack of simple techniques to differentiate between viable and nonviable cells, the aim of this study was to optimize and evaluate a straightforward test based on propidium monoazide (PMA) dye action combined with a qPCR assay (PMA-qPCR) for the selective quantification of viable/nonviable epimastigotes of Trypanosoma cruzi PMA has the ability to penetrate the plasma membrane of dead cells and covalently cross-link to the DNA during exposure to bright visible light, thereby inhibiting PCR amplification. Different concentrations of PMA (50-200 μM) and epimastigotes of the Maracay strain of T. cruzi (1 × 10(5)-10 parasites/mL) were assayed; viable and nonviable parasites were tested and quantified by qPCR with a TaqMan probe specific for T. cruzi. In the PMA-qPCR assay optimized at 100 μM PMA, a significant qPCR signal reduction was observed in the nonviable versus viable epimastigotes treated with PMA, with a mean signal reduction of 2.5 logarithm units and a percentage of signal reduction > 98%, in all concentrations of parasites assayed. This signal reduction was also observed when PMA-qPCR was applied to a mixture of live/dead parasites, which allowed the detection of live cells, except when the concentration of live parasites was low (10 parasites/mL). The PMA-qPCR developed allows differentiation between viable and nonviable epimastigotes of T. cruzi and could thus be a potential method of parasite viability assessment and quantification.

Follow-up of an asymptomatic Chagas disease population of children after treatment with nifurtimox (Lampit) in a sylvatic endemic transmission area of Colombia

Background

Chagas disease is an anthropozoonosis caused by Trypanosoma cruzi. Two drugs are currently used for the etiological treatment of the disease: Nifurtimox (Lampit) and Benznidazole. This study presents a quasi-experimental trial (non-control group) of sixty-two patients who were treated for Chagas disease with Nifurtimox (Lampit), and were then followed for 30 months post-treatment. The safety of Nifurtimox (Lampit) for Chagas disease in this group of children primarily between 4 and 19 years old was also evaluated.

Materials and methods

The 62 patients included in the study were selected when resulted seropositive for two out of three fundamentally different serological tests. All children were treated during two months according to protocols established by WHO. Monitoring was performed every twenty days to evaluate treatment safety. In 43 patients, two different serological tests: ELISA and IFAT; and two parasitological tests: blood culture, and real time PCR, (qPCR) were performed to assess therapeutic response, defined as post-treatment serological negativization.

Principal findings

All patients completed the treatment successfully, and six patients abandoned the post-treatment follow-up. Adverse effects occurred in 74% of patients, but only 4.8% of cases required temporary suspension to achieve 100% adherence to the 60-day treatment, and all symptoms reverted after treatment completion. Both parasite load (measured through qPCR) and antibodies (ELISA absorbance) evidenced a significant median reduction 6 months after treatment from 6.2 to 0.2 parasite equivalents/mL, and from 0.6 to 0.2 absorbance units respectively (p<0.001). Serological negativization by ELISA was evident since 6 months post-treatment, whereas by IFAT only after 18 months. Serological negativization by the two tests (ELISA and IFAT) was 41.9% (95%CI: 26.5–57.3) after 30 months post-treatment. qPCR was positive in 88.3% of patients pre-treatment and only in 12.1% of patients after 30 months. Survival analysis indicated that only 26.3% (95%CI: 15.5–44.8) persisted with negative qPCR during the whole follow-up period.

Conclusions

Nifurtimox was very well tolerated and successfully reduced parasite load and antibody titers. Re-infection, lysed parasites or a lack of anti-parasitic activity could explain these persistently positive qPCR cases.

Chagas disease is currently treated with two drugs, Benznidazole (BNZ) and Nifurtimox (NFX). The need to find the ideal diagnostic technique for post treatment evaluation still exists, due to the known flaws of the currently used techniques. We performed an evaluation of the safety and effectiveness of Nifurtimox treatment in a population of 62 children infected with Trypanosoma cruzi in an endemic Colombian area. The effectiveness was evaluated with two serological tests (IFAT and ELISA), and with two parasitological tests (blood culture and qPCR). We suggest the use of qPCR as a marker of response in all future treatment evaluations for Chagas disease, due to its potential to detect early treatment failure and/or reinfection. In order to have more conclusive results, it is important to perform this kind of study in a controlled environment, wherein the risk of reinfection is not considered.

Biological markers for evaluating therapeutic efficacy in Chagas disease, a systematic review

The most neglected aspects of Chagas disease (CD) have been patient care and treatment. Despite recent progress in the development of potentially improved drugs, there is no consensus among different research groups on the lack of therapeutic response markers to evaluate efficacy of newly proposed drugs early after treatment. A systematic review of current evidence regarding molecules which are potential biomarkers for therapeutic response has been conducted using quality assessment and target responses as primary criteria. The review provides a panorama of the cumulative evidence and specific needs for development of a battery of complementary biomarkers which together fulfill ideal or acceptable criteria to evaluate early responses to treatment for chronic CD. There are several marker candidates which together may fulfill acceptable criteria to indicate the efficacy of a trypanocidal treatment. Data from ongoing studies are considered essential to improve assessment of existing markers and to identify those for early follow-up of treated patients.

The Trypanosoma cruzi satellite DNA OligoC-TesT and Trypanosoma cruzi kinetoplast DNA OligoC-TesT for diagnosis of Chagas disease: a multi-cohort comparative evaluation study

BACKGROUND

The Trypanosoma cruzi satellite DNA (satDNA) OligoC-TesT is a standardised PCR format for diagnosis of Chagas disease. The sensitivity of the test is lower for discrete typing unit (DTU) TcI than for TcII-VI and the test has not been evaluated in chronic Chagas disease patients.

METHODOLOGY/PRINCIPAL FINDINGS

We developed a new prototype of the OligoC-TesT based on kinetoplast DNA (kDNA) detection. We evaluated the satDNA and kDNA OligoC-TesTs in a multi-cohort study with 187 chronic Chagas patients and 88 healthy endemic controls recruited in Argentina, Chile and Spain and 26 diseased non-endemic controls from D.R. Congo and Sudan. All specimens were tested in duplicate. The overall specificity in the controls was 99.1% (95% CI 95.2%-99.8%) for the satDNA OligoC-TesT and 97.4% (95% CI 92.6%-99.1%) for the kDNA OligoC-TesT. The overall sensitivity in the patients was 67.9% (95% CI 60.9%-74.2%) for the satDNA OligoC-TesT and 79.1% (95% CI 72.8%-84.4%) for the kDNA OligoC-Test.

CONCLUSIONS/SIGNIFICANCE

Specificities of the two T. cruzi OligoC-TesT prototypes are high on non-endemic and endemic controls. Sensitivities are moderate but significantly (p = 0.0004) higher for the kDNA OligoC-TesT compared to the satDNA OligoC-TesT.

Therapy of chagas disease: implications for levels of prevention

This paper reviews the evidence supporting the use of etiological treatment for Chagas disease that has changed the standard of care for patients with Trypanosoma cruzi infection in the last decades. Implications of this evidence on different levels of prevention as well as gaps in current knowledge are also discussed. In this regard, etiological treatment has shown to be beneficial as an intervention for secondary prevention to successfully cure the infection or to delay, reduce, or prevent the progression to disease, and as primary disease prevention by breaking the chain of transmission. Timely diagnosis during initial stages would allow for the prescription of appropriate therapies mainly in the primary health care system thus improving chances for a better quality of life. Based on current evidence, etiological treatment has to be considered as an essential public health strategy useful to reduce disease burden and to eliminate Chagas disease altogether.

Therapy, diagnosis and prognosis of chronic Chagas disease: insight gained in Argentina

The purpose of this review is to describe research findings regarding chronic Chagas disease in Argentina that have changed the standards of care for patients with Trypanosoma cruzi infection. Indirect techniques (serological tests) are still the main tools for the primary diagnosis of infection in the chronic phase, but polymerase chain reaction has been shown to be promising. The prognosis of patients with heart failure or advanced stages of chagasic cardiomyopathy is poor, but a timely diagnosis during the initial stages of the disease would allow for prescription of appropriate therapies to offer a better quality of life. Treatment of T. cruzi infection is beneficial as secondary prevention to successfully cure the infection or to delay, reduce or prevent the progression to disease and as primary disease prevention by breaking the chain of transmission. Current recommendations have placed the bulk of the diagnostic and treatment responsibility on the Primary Health Care System. Overall, the current research priorities with respect to Chagas disease should be targeted towards (i) the production of new drugs that would provide a shorter treatment course with fewer side effects; (ii) the development of new tools to confirm cure after a full course of treatment during the chronic phase and (iii) biomarkers to identify patients with a high risk of developing diseases.

Diagnosis of Chagas disease: what has been achieved? What remains to be done with regard to diagnosis and follow up studies?

In the acute phase and in the chronic forms of Chagas disease, the etiological diagnosis may be performed by detection of the parasite using direct or indirect parasitological methods and by the presence of antibodies in the serum by way of serological tests. Several techniques are easily available, ranging from the simplest wet smear preparation to immuno-enzymatic assays with recombinant antigens that will meet most diagnostic needs. Other tests under evaluation include a molecular test using polymerase chain reaction, which has shown promising results and may be used as a confirmatory test both in the acute and chronic phases of the disease. Better rapid tests are needed for diagnosis, some of which are already under evaluation. Additionally, there is a need for tools that can identify patients cured shortly after specific treatment. Other needs include a marker for prognosis and early diagnosis of congenital transmission.

T. cruzi OligoC-TesT: a simplified and standardized polymerase chain reaction format for diagnosis of Chagas disease

BACKGROUND

PCR has evolved into one of the most promising tools for T. cruzi detection in the diagnosis and control of Chagas disease. However, general use of the technique is hampered by its complexity and the lack of standardization.

METHODOLOGY

We here present the development and phase I evaluation of the T. cruzi OligoC-TesT, a simple and standardized dipstick format for detection of PCR amplified T. cruzi DNA. The specificity and sensitivity of the assay were evaluated on blood samples from 60 Chagas non-endemic and 48 endemic control persons and on biological samples from 33 patients, 7 reservoir animals, and 14 vectors collected in Chile.

PRINCIPAL FINDINGS

The lower detection limits of the T. cruzi OligoC-TesT were 1 pg and 1 to 10 fg of DNA from T. cruzi lineage I and II, respectively. The test showed a specificity of 100% (95% confidence interval [CI]: 96.6%-100%) on the control samples and a sensitivity of 93.9% (95% CI: 80.4%-98.3%), 100% (95% CI: 64.6%-100%), and 100% (95% CI: 78.5%-100%) on the human, rodent, and vector samples, respectively.

CONCLUSIONS

The T. cruzi OligoC-TesT showed high sensitivity and specificity on a diverse panel of biological samples. The new tool is an important step towards simplified and standardized molecular diagnosis of Chagas disease.

Chagasic encephalitis in HIV patients: common presentation of an evolving epidemiological and clinical association

We present a case of chagasic meningoencephalitis reactivation in an HIV-infected woman with advanced immunosuppression. Prolonged survival was attained with antiparasitic therapy and secondary prophylaxis, in conjunction with the use of highly-active antiretroviral therapy. The geographic expansion of the HIV epidemic around the world coupled with global migration and international travel have created a favourable situation for Trypanosoma cruzi and HIV coinfection. The clinical manifestations of Chagas disease in HIV-positive people usually represent reactivation and not acute infection with T cruzi (coinfection). Symptomatic reactivation of chronic latent T cruzi infection can be triggered by severe immunosuppression associated with HIV infection. In this setting, Chagas disease reactivation often presents as meningoencephalitis resembling toxoplasma encephalitis. We review, in this Grand Round, the clinical manifestations, diagnostic approach, pathogenesis, natural history, treatment, prognosis, and prevention of Chagas disease reactivation among HIV-infected people with an emphasis on CNS manifestations.

An update on the management of Chagas cardiomyopathy

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, infects nearly 18 million people in Latin America and mainly affects the heart, causing heart failure, arrhythmias, heart block, thromboembolism, stroke and death. In this review, the clinical diagnosis and management of Chagas cardiomyopathy are discussed. Particular emphasis is placed on the clinical staging of patients and the use of various diagnostic tests that may be useful in individualizing treatment of the two most relevant clinical syndromes, that is, heart failure and arrhythmias. The relevance of specific treatments are discussed, stressing the important role of parasite persistence in disease pathogenesis. We also discuss new therapy modalities that may have a role in the treatment of Chagas cardiomyopathy.

Development of a real-time PCR assay for Trypanosoma cruzi detection in blood samples

The aim of this study was to develop a real-time PCR technique to detect Trypanosoma cruzi DNA in blood of chagasic patients. Analytical sensitivity of the real-time PCR was assessed by two-fold serial dilutions of T. cruzi epimastigotes in seronegative blood (7.8 down to 0.06 epimastigotes/mL). Clinical sensitivity was tested in 38 blood samples from adult chronic chagasic patients and 1 blood sample from a child with an acute congenital infection. Specificity was assessed with 100 seronegative subjects from endemic areas, 24 seronegative subjects from non-endemic area and 20 patients with Leishmania infantum-visceral leishmaniosis. Real-time PCR was designed to amplify a fragment of 166 bp in the satellite DNA of T. cruzi. As internal control of amplification human RNase P gene was coamplified, and uracil-N-glycosylase (UNG) was added to the reaction to avoid false positives due to PCR contamination. Samples were also analysed by a previously described nested PCR (N-PCR) that amplifies the same DNA region as the real-time PCR. Sensitivity of the real-time PCR was 0.8 parasites/mL (50% positive hit rate) and 2 parasites/mL (95% positive hit rate). None of the seronegative samples was positive by real-time PCR, resulting in 100% specificity. Sixteen out of 39 patients were positive by real-time PCR (41%). Concordance of results with the N-PCR was 90%. In conclusion, real-time PCR provides an optimal alternative to N-PCR, with similar sensitivity and higher throughput, and could help determine ongoing parasitaemia in chagasic patients.