Diagnostic Accuracy of Two Molecular Tools for Diagnosis of Congenital Chagas Disease

Detection of Trypanosoma cruzi in a Reactive Blood Bank Sample in Sonora, Mexico

Chagas disease is a neglected disease caused by the parasite Trypanosoma cruzi, a public health problem in both endemic and non-endemic countries. In Mexico, the southern region is considered endemic, and cases are frequently reported; however, in the northwestern region, only a few cases are confirmed annually. This study describes, for the first time, the Discrete Typing Unit (DTU) of Trypanosoma cruzi in a volunteer blood donor rejected for being reactive in the northwestern region of Mexico. Seroreactivity was confirmed using "in-house" ELISAs which employed three different antigens: total extract from Trypanosoma cruzi isolated from a vector (Triatoma rubida) from Sonora (strain T1), strain H1 and CL-Brener. The molecular characterization of Trypanosoma cruzi was conducted by amplifying satellite DNA by qPCR and posterior sequencing of the mini-exon gene, using Next Generation Sequencing (NGS) to enhance the accuracy of genetic characterization. The results show that the reactive status of this blood donor was confirmed using our in-house ELISAs, and the presence of Trypanosoma cruzi by detecting TcI DTU confirmed the infection status.

Diagnosing Chagas in Pregnancy and Childhood: What's Old and New

Trypanosoma cruzi, the parasite that causes Chagas disease, affects as many as 300,000 individuals in the United States. Screening individuals of childbearing age can prevent congenital transmission, and diagnosing infants and children can prevent long-term sequelae of Chagas disease. Current methods to diagnose Chagas have limations, including relying on identification of at-risk individuals and requiring at least 2 separate tests to confirm infection.

Novel IgM-based lateral flow assay for diagnosis of congenital Chagas disease

BACKGROUND

The diagnosis of congenital Chagas disease in newborns relies on the microhematocrit method which exhibits reduced sensitivity during the early stages of infection and quantitative PCR for Trypanosoma cruzi, which is applied only in specialised centre due to its technical complexity. Consequently, the majority of congenital transmission cases are confirmed after an extended period of serological monitoring, resulting in delayed treatments and reduced cure rates. The need for new, accurate tests for the timely diagnosis of the disease in newborns is evident.

OBJECTIVES

We developed a lateral flow assay based on IgM detection (IgM-LFA) using the novel chimeric antigen CP4, which have demonstrated high performance in IgM-ELISA, as previously reported by our group.

METHODS

The accuracy of IgM-LFA was evaluated comparatively with IgM-ELISA using 28 serum samples from infants up to three months old, congenitally infected (n = 11) or non-infected (n = 17) with T. cruzi. Additionally, it was assessed for its agreement with microhematocrit and quantitative PCR, through estimating the Cohen's Kappa coefficient (k).

RESULTS

The IgM-LFA showed 100% specificity and 81.82% sensitivity and IgM-ELISA gave 100% specificity and sensitivity when evaluated against the standard algorithm diagnosis for congenital Chagas disease. Notably, the IgM-LFA identified two additional cases in relation to microhematocrit and showed a correlation of k = 0.84 with quantitative PCR, corresponding to almost perfect agreement with this molecular test.

CONCLUSION

These results suggest that IgM-LFA has the potential to facilitate decentralised detection of congenital Chagas disease, contributing to the early and enhance detection of infected newborns.

A specific, stable, and accessible LAMP assay targeting the HSP70 gene of Trypanosoma cruzi

Diagnostic delays prevent most Chagas disease patients from receiving timely therapy during the acute phase when treatment is effective. qPCR-based diagnostic methods provide high sensitivity during this phase but require specialized equipment and complex protocols. More simple and cost-effective tools are urgently needed to optimize early Chagas disease diagnosis in low-income endemic regions. Here, we present a loop-mediated isothermal amplification (LAMP) that targets a highly conserved region in the HSP70 gene of Trypanosoma cruzi, the causative agent of Chagas disease. This assay demonstrates species-specific amplification across multiple parasite genetic lineages while maintaining stability after 2 hours of incubation and at least 8 months of storage at -20°C. Moreover, the assay is at least 12 times less expensive than the TaqMan qPCR that is currently routinely used for acute Chagas diagnostics. Population-based validation in 100 infants born to Chagas-positive mothers in Santa Cruz, Bolivia, yielded a specificity of 100% and sensitivity exceeding 77% when compared to a TaqMan qPCR that targets satellite DNA. This cost-effective assay holds promise for large-scale diagnosis of Chagas disease in endemic regions with limited resources.

Congenital Chagas disease: A cohort study to assess molecular diagnostic methods at the Chagas disease national reference center of Argentina

BACKGROUND

Trypanosoma cruzi is a protozoan parasite which causes Chagas disease. Mother-to-child transmission is the main route of transmission in vector-free areas. Congenital Chagas disease refers specifically to cases arising from this route of transmission. This work evaluates the clinical sensitivity of two qPCR techniques for diagnosis of congenital Chagas disease.

METHODS

The study was developed in the National Institute of parasitology (NIP), Argentina, and Pan-American Health Organization/ Word Health Organization Collaborating Center for Chagas Disease. Between July 2014 and May 2018, a prospective cohort study was carried out with 499 children born to seropositive for T. cruzi infection included. The performance of qPCR techniques was compared with the gold standard diagnostic algorithm for Congenital Chagas disease (CCD-GS), which comprises performing more than one parasitological test on children from birth until nine months of age, and serology from ten months of age.

FINDINGS

Of the 961 babies born to women seropositive for Chagas disease who were attended at the NIP laboratory, 462 did not meet the study inclusion criteria; 22 cases were diagnosed with congenital Chagas disease. qPCR showed 100% clinical sensitivity and 98 to 100% clinical specificity for the diagnosis of congenital Chagas disease compared with CCD-GS algorithm.

INTERPRETATION

The results obtained in this study demonstrate the clinical accuracy and effectiveness of qPCR SatDNA and qPCR kDNA for diagnosis of congenital Chagas disease. It could be a powerful tool for chagas test and treat strategies to reduce late complications of the disease.

FUNDING

This work was financed by the INP Dr. Mario Fatala Chaben, ANLIS Dr. Carlos G. Malbran.

A simplified molecular tool for detecting the Chagas etiological agent using a vector feces sample in field conditions

Triatomine bugs are vectors of Trypanosoma cruzi, the etiologic agent of Chagas disease in the American continent. Here, we have tested a loop-mediated isothermal amplification (LAMP) test for a direct detection of T. cruzi in feces of Triatoma infestans, the main vector of this parasite in the Southern Cone of America. The analytical evaluation showed positive results with samples of triatomine feces artificially inoculated with DNA from strains of T. cruzi corresponding to each Discrete Typing Units (I-VI), with a sensitivity of up to one parasite per reaction. Conversely, the reaction yielded negative results when tested with DNA from Trypanosoma rangeli and other phylogenetically related and unrelated organisms. In triatomines captured under real field conditions (from urban households), and defined as positive or negative for T. cruzi using the reference microscopy technique, the LAMP test achieved a concordance of 100 %. Our results demonstrate that this LAMP reaction exhibits excellent analytical specificity and sensitivity without interference from the fecal matrix, since all the reactions were conducted without purification steps. This simple molecular diagnostic technique can be easily used by vector control agencies under field conditions.

Development of a Colorimetric Loop-Mediated Isothermal Amplification Assay for the Detection of Trypanosoma cruzi in Low-Resource Settings

Chagas disease is an inflammatory parasitic infection caused by Trypanosoma cruzi (T. cruzi). Early diagnosis is crucial in guiding treatment and slowing disease progression; however, current diagnostic methods have insufficient detection limits and often require skilled technicians. Molecular tests, especially isothermal nucleic acid assays, are advantageous due to their excellent sensitivity, specificity, speed, and simplicity. Here, we optimized a colorimetric loop-mediated isothermal amplification (LAMP) assay for T. cruzi. We can detect as few as 2 genomic copies/reaction using three different T. cruzi strains. We examined selectivity using other parasitic protozoans and successfully detected T. cruzi DNA extracted from parasites in human whole blood down to 1.2 parasite equivalents/reaction. We also performed a blinded study using canine blood samples and established a 100% sensitivity, specificity, and accuracy for the colorimetric LAMP assay. Finally, we used a heated 3D printer bed and an insulated thermos cup to demonstrate that the LAMP incubation step could be performed with accessible, low-cost materials. Altogether, we have developed a high-performing assay for T. cruzi with a simple colorimetric output that would be ideal for rapid, low-cost screening at the point of use.

In vitro diagnostic methods of Chagas disease in the clinical laboratory: a scoping review

Background

Chagas disease (CD), caused by Trypanosoma cruzi, is a global health concern with expanding geographical reach. Despite improved and accessible test methods, diagnosing CD in its various phases remains complex. The existence of clinical scenarios, including immunosuppressed patients, transplant-related CD reactivation, transfusion-associated cases, and orally transmitted acute infections, adds to the diagnostic challenge. No singular gold standard test exists for all phases, and recommendations from PAHO and the CDC advocate for the use of two serological methods for chronic CD diagnosis, while molecular methods or direct parasite detection are suggested for the acute phase. Given the complexity in the diagnostic landscape of CD, the goal of this scoping review is to characterize available diagnostic tests for CD in the clinical laboratory.

Methods

A literature search in PubMed was conducted on studies related to In vitro diagnosis (IVD) in humans published in English, Spanish, or Portuguese language as of 28 August 2023, and extended backward with no predefined time frame. Studies underwent title and abstract screening, followed by full-text review. Studies included were classified based on the diagnostic method used. Test methods were grouped as serological, molecular, and other methods. Performance, availability, and regulatory status were also characterized.

Results

Out of 85 studies included in the final review, 115 different tests were identified. These tests comprised 89 serological test types, 21 molecular test types, and 5 other test methods. Predominant serological tests included ELISA (38 studies, 44.70%), Rapid tests (19 studies, 22.35%), and chemiluminescence (10 studies, 11.76%). Among molecular tests, Polymerase Chain Reaction (PCR) assays were notable. Twenty-eight tests were approved globally for IVD or donor testing, all being serological methods. Molecular assays lacked approval for IVD in the United States, with only European and Colombian regulatory acceptance.

Discussion and conclusion

Serological tests, specifically ELISAs, remain the most used and commercially available diagnostic methods. This makes sense considering that most Chagas disease diagnoses occur in the chronic phase and that the WHO gold standard relies on 2 serological tests to establish the diagnosis of chronic Chagas. ELISAs are feasible and relatively low-cost, with good performance with sensitivities ranging between 77.4% and 100%, and with specificities ranging between 84.2% and 100%. Molecular methods allow the detection of specific variants but rely on the parasite's presence, which limits their utility to parasitemia levels. Depending on the PCR method and the phase of the disease, the sensitivity ranged from 58.88 to 100% while the mean specificity ranged from 68.8% to 100%. Despite their performance, molecular testing remains mostly unavailable for IVD use. Only 3 molecular tests are approved for IVD, which are available only in Europe. Six commercial serological assays approved by the FDA are available for blood and organ donor screening. Currently, there are no guidelines for testing CD oral outbreaks. Although more evidence is needed on how testing methods should be used in special clinical scenarios, a comprehensive approach of clinical assessment and diagnostics tests, including not IVD methods, is required for an accurate CD diagnosis.

Efficacy of short-course treatment for prevention of congenital transmission of Chagas disease: A retrospective cohort study

BACKGROUND

In regions with controlled vector transmission of T. cruzi, congenital transmission is the most frequent route of infection. Treatment with benznidazole (BZ) or nifurtimox (NF) for 60 days in girls and women of childbearing age showed to be effective in preventing mother to child transmission of this disease. Reports on short-course treatment (≤30 days) are scarce.

METHODS

Retrospective cohort study. Offspring of women with Chagas disease who received short-course treatment (≤30 days) with BZ or NF, attended between 2003 and 2022, were evaluated. Parasitemia (microhaematocrit and/or PCR) was performed at <8 months of age, and serology (ELISA and IHA) at ≥8 months to rule out congenital infection.

RESULTS

A total of 27 women receiving ≤30 days of treatment and their children were included in this study. NF was prescribed in 17/27 (63%) women, and BZ in 10/27 (37%). The mean duration of treatment was 29.2 days. None of the women experienced serious adverse events during treatment, and no laboratory abnormalities were observed. Forty infants born to these 27 treated women were included. All newborns were full term, with appropriate weight for their gestational age. No perinatal infectious diseases or complications were observed.

DISCUSSION

Several studies have shown that treatment of infected girls and women of childbearing age for 60 days is an effective practice to prevent transplacental transmission of T. cruzi. Our study demonstrated that short-duration treatment (≤30 days) is effective and beneficial in preventing transplacental transmission of Chagas disease.

Subunit nanovaccine elicited T cell functional activation controls Trypanosoma cruzi mediated maternal and placental tissue damage and improves pregnancy outcomes in mice

This study investigated a candidate vaccine effect against maternal Trypanosoma cruzi (Tc) infection and improved pregnancy outcomes. For this, TcG2 and TcG4 were cloned in a nanoplasmid optimized for delivery, antigen expression, and regulatory compliance (nano2/4 vaccine). Female C57BL/6 mice were immunized with nano2/4, infected (Tc SylvioX10), and mated 7-days post-infection to enable fetal development during the maternal acute parasitemia phase. Females were euthanized at E12-E17 (gestation) days. Splenic and placental T-cell responses were monitored by flow cytometry. Maternal and placental/fetal tissues were examined for parasites by qPCR and inflammatory infiltrate by histology. Controls included age/immunization-matched non-pregnant females. Nano2/4 exhibited no toxicity and elicited protective IgG2a/IgG1 response in mice. Nano2/4 signaled a splenic expansion of functionally active CD4+ effector/effector memory (Tem) and central memory (Tcm) cells in pregnant mice. Upon challenge infection, nano2/4 increased the splenic CD4+ and CD8+T cells in all mice and increased the proliferation of CD4+Tem, CD4+Tcm, and CD8+Tcm subsets producing IFNγ and cytolytic molecules (PRF1, GZB) in pregnant mice. A balanced serum cytokines/chemokines response and placental immune characteristics indicated that pregnancy prevented the overwhelming damaging immune response in mice. Importantly, pregnancy itself resulted in a significant reduction of parasites in maternal and fetal tissues. Nano2/4 was effective in arresting the Tc-induced tissue inflammatory infiltrate, necrosis, and fibrosis in maternal and placental tissues and improving maternal fertility, placental efficiency, and fetal survival. In conclusion, we show that maternal nano2/4 vaccination is beneficial in controlling the adverse effects of Tc infection on maternal health, fetal survival, and pregnancy outcomes.

Clinical use of molecular methods for Trypanosoma cruzi infection in endemic and non-endemic countries: Benefits, limitations and challenges

Trypanosoma cruzi infection is diagnosed by parasitological, molecular, and serological tests. Molecular methods based on DNA amplification provide a more sensitive alternative to classical parasitological techniques for detecting evidence of T. cruzi parasitemia, and are the preferred tests for congenital and oral transmission cases and parasite reactivation in chronically infected immunosuppressed individuals. In newborns at risk of vertical transmission, simplified diagnostic algorithms that provide timely results can reduce the high follow-up losses observed with current algorithms. Molecular methods have also proved useful for monitoring T. cruzi infection in solid organ transplantation recipients, regardless of host immune status, allowing parasite detection even before symptom manifestation. Furthermore, in the absence of other biomarkers and a practical test of cure, and given the limitations of serological methods, recent clinical guidelines have included polymerase chain reaction (PCR) to detect therapeutic failure after antiparasitic treatment in chronically infected adults. Increasing evidence supports the use of molecular tests in a clinical context, given the improved sensitivity and specificity of current assays - characteristics which largely depend on epidemiological factors and genetic and antigenic variability among T. cruzi strains. Further development and registration of commercial PCR kits will improve the use of molecular tests. We discuss the attributes of PCR and other molecular tests for clinical management in people with T. cruzi infection.

Molecular diagnosis of Chagas disease: a systematic review and meta-analysis

BACKGROUND

The complexity of the Chagas disease and its phases is impossible to have a unique test for both phases and a lot of different epidemiological scenarios. Currently, serology is the reference standard technique; occasionally, results are inconclusive, and a different diagnostic technique is needed. Some guidelines recommend molecular testing. A systematic review and meta-analysis of available molecular tools/techniques for the diagnosis of Chagas disease was performed to measure their heterogeneity and efficacy in detecting Trypanosoma cruzi infection in blood samples.

METHODS

A systematic review was conducted up to July 27, 2022, including studies published in international databases. Inclusion and exclusion criteria were defined to select eligible studies. Data were extracted and presented according to PRISMA 2020 guidelines. Study quality was assessed using Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2). A random-effects model was used to calculate pooled sensitivity, specificity, and diagnostic odds ratio (DOR). Forest plots and a summary of the receiving operating characteristics (SROC) curves displayed the outcomes. Heterogeneity was determined by I2 and Tau2 statistics and P values. Funnel plots and Deek's test were used to assess publication bias. A quantitative meta-analysis of the different outcomes in the two different clinical phases was performed.

RESULTS

We identified 858 records and selected 32 papers. Studies pertained to endemic countries and nonendemic areas with adult and paediatric populations. The sample sizes ranged from 17 to 708 patients. There were no concerns regarding the risk of bias and applicability of all included studies. A positive and nonsignificant correlation coefficient (S = 0.020; P = 0.992) was obtained in the set of studies that evaluated diagnostic tests in the acute phase population (ACD). A positive and significant correlation coefficient (S = 0.597; P < 0.000) was obtained in the case of studies performed in the chronic phase population (CCD). This resulted in high heterogeneity between studies, with the master mix origin and guanidine addition representing significant sources.

INTERPRETATION/CONCLUSIONS AND RELEVANCE

The results described in this meta-analysis (qualitative and quantitative analyses) do not allow the selection of the optimal protocol of molecular method for the study of Trypanosoma cruzi infection in any of its phases, among other reasons due to the complexity of this infection. Continuous analysis and optimization of the different molecular techniques is crucial to implement this efficient diagnosis in endemic areas.

Practical diagnostic algorithms for Chagas disease: a focus on low resource settings

INTRODUCTION

Chagas disease, caused by parasite Trypanosoma cruzi, is the most important neglected tropical disease in the Americas. Two drugs are available for treatment, but access to them is challenging, in part due to complex diagnostic algorithms. These are stage-dependent, involve multiple tests, and are ill-adapted to the reality of vast areas where the disease is endemic. Molecular and serologic tools are used to detect acute and chronic infections, with the performance of the latter showing geographic differences. Breakthroughs in the development of new diagnostic tools include the validation of a loop-mediated isothermal amplification assay for acute infections (T. cruzi-LAMP), and the regional validation of several rapid diagnostic tests (RDTs) for chronic infection, which simplify testing in resource-limited settings. The literature search was carried out in the MEDLINE database until 1 August 2023.

AREAS COVERED

This review outlines existing algorithms, and proposes new ones focused on point-of-care testing.

EXPERT OPINION

Integrating point-of-care testing into existing diagnostic algorithms in certain endemic areas will increase access to timely diagnosis and treatment. However, additional research is needed to validate the use of these techniques across a wider geography, and to better understand the cost-effectiveness of their large-scale implementation.

Laboratory diagnosis of Trypanosoma cruzi infection: a narrative review

Trypanosoma cruzi infection, currently endemic in 21 countries, is a public health problem not only in the Americas but also in countries with Latin American migrants. However, it is estimated that two-thirds of people with Chagas disease currently live in urban areas and that only 10% of them are aware of it. This review summarizes the most important aspects of the diagnosis of human T. cruzi infection by describing the following aspects of clinical laboratory diagnosis: the most widely used tests available in Latin America and those expected to improve access to diagnosis of the affected population with their implementation; the advantages, disadvantages, and sensitivity of the tests in the different phases of infection; and their usefulness in the acute or chronic phases of infection and in the context of immunosuppression. In this way, we hope to contribute to broadening the knowledge about this prevalent infection in the Americas.

Effects of Acute and Chronic Trypanosoma cruzi Infection on Pregnancy Outcomes in Mice: Parasite Transmission, Mortality, Delayed Growth, and Organ Damage in Pups

Chagas disease is caused by Trypanosoma cruzi. This study aimed to determine the effects of T. cruzi infection on fertility rate and health of the newborn pups in pregnant mice. Female mice were challenged with T. cruzi and mated at 21 days (acute parasitemic phase) or 90 days (chronic parasite persistence phase) after infection. Pups were examined for growth up to 20 days after birth; and parasite burden in brain, heart, skeletal muscle, and intestine was measured by real-time quantitative PCR. The inflammatory infiltrate, necrosis, and fibrosis in pups' heart and brain tissues were evaluated by histology. T. cruzi infection in dams delayed the onset of pregnancy, decreased the fertility rate, and led to vertical transmission of parasite to the pups. Furthermore, infected dams delivered pups that exhibited decreased survival rate, decreased birth weight, and decreased growth rate. Significantly increased inflammation, necrosis, and fibrosis of cardiac and brain tissues were noted in pups born to infected dams. Initial challenge with higher parasite dose had more detrimental effects on fertility rate and pups' health in both acutely and chronically infected dams. In conclusion, mice offer a promising model to evaluate the efficacy of new vaccines and therapeutic drugs in controlling the acute and chronic maternal T. cruzi infection and congenital transmission to newborns, and in improving the fertility rate and pups' health outcomes.