Use of Schistosoma mansoni soluble egg antigen (SEA) for antibody detection and diagnosis of schistosomiasis: The need for improved accuracy evaluations of diagnostic tools

Deep humoral profiling coupled to interpretable machine learning unveils diagnostic markers and pathophysiology of schistosomiasis

Schistosomiasis, a highly prevalent parasitic disease, affects more than 200 million people worldwide. Current diagnostics based on parasite egg detection in stool detect infection only at a late stage, and current antibody-based tests cannot distinguish past from current infection. Here, we developed and used a multiplexed antibody profiling platform to obtain a comprehensive repertoire of antihelminth humoral profiles including isotype, subclass, Fc receptor (FcR) binding, and glycosylation profiles of antigen-specific antibodies. Using Essential Regression (ER) and SLIDE, interpretable machine learning methods, we identified latent factors (context-specific groups) that move beyond biomarkers and provide insights into the pathophysiology of different stages of schistosome infection. By comparing profiles of infected and healthy individuals, we identified modules with unique humoral signatures of active disease, including hallmark signatures of parasitic infection such as elevated immunoglobulin G4 (IgG4). However, we also captured previously uncharacterized humoral responses including elevated FcR binding and specific antibody glycoforms in patients with active infection, helping distinguish them from those without active infection but with equivalent antibody titers. This signature was validated in an independent cohort. Our approach also uncovered two distinct endotypes, nonpatent infection and prior infection, in those who were not actively infected. Higher amounts of IgG1 and FcR1/FcR3A binding were also found to be likely protective of the transition from nonpatent to active infection. Overall, we unveiled markers for antibody-based diagnostics and latent factors underlying the pathogenesis of schistosome infection. Our results suggest that selective antigen targeting could be useful in early detection, thus controlling infection severity.

Accuracy of commercial ELISA and ICT for screening schistosomiasis infections at a low endemicity area in Brazil

BACKGROUND

Control interventions recommended by the World Health Organization have successfully resulted in low-intensity schistosomiasis transmission areas. To achieve elimination of transmission, new diagnostic screening tools are needed to overcome less than adequate sensitivity of the currently used Kato-Katz faecal thick smear method. Ideally, in-house serological tests should be avoided due to not having a continuous supply of kits as would be necessary for large population studies. Quality assurance provided by manufacturers and proper performance evaluations are also needed. We evaluated the accuracy of two commercially available serology tests as screening methods for detecting light schistosomiasis infections.

METHODS

Serum samples were collected in 2015 from individuals living in a low-endemicity locality in northeastern Brazil and deposited in a biorepository. We evaluated immunoglobulin G (IgG) and IgM enzyme-linked immunosorbent assays (ELISAs) and an immunochromatographic test (ICT). The Helmintex method was used to define true-positive samples.

RESULTS

Overall sensitivity was close to 90% for both the IgG ELISA and ICT, yet specificity was 28% and 18%, respectively. For the IgM ELISA, the values were estimated to be 55% and 43%, respectively.

CONCLUSIONS

Poor specificity and positive predictive values prevent these tests from being recommended for screening populations in low-intensity schistosomiasis-endemic areas.

Descriptive study on risk of increased morbidity of schistosomiasis and graft loss after liver transplantation

Solid-organ transplantation procedures have witnessed a surge in frequency. Consequently, increased attention to associated infections and their impact on graft success is warranted. The liver is the principal target for infection by the flatworm Schistosoma mansoni. Hence, rigorous screening protocols for this parasite should be implemented for liver transplantation donors and recipients. This study investigated the risks posed by schistosomiasis-infected liver tissues for successful liver transplantation (LT), considering donors and recipients, by analyzing reported cases. Among the 43 patients undergoing LT (donors = 19; recipients = 24), 32 were infected with S. mansoni, five were infected with other Schistosoma species, and no identification was made in four patients. Reported follow-up periods ranged from 1 to 132 months, and all patients achieved successful recovery. As these helminths do not replicate in their vertebrate hosts, immunosuppressive treatment is not expected to promote increased morbidity or reactivation. Moreover, suspected or confirmed schistosomiasis infections often have a benign course, and generally, should not prevent LT. The available literature was reviewed and a provisional screening protocol has been proposed.

Diagnostic tests for human Schistosoma mansoni and Schistosoma haematobium infection: a systematic review and meta-analysis

BACKGROUND

Accurate diagnosis is pivotal for implementing strategies for surveillance, control, and elimination of schistosomiasis. Despite their low sensitivity in low-endemicity areas, microscopy-based urine filtration and the Kato-Katz technique are considered as reference diagnostic tests for Schistosoma haematobium and Schistosoma mansoni infections, respectively. We aimed to collate all available evidence on the accuracy of other proposed diagnostic techniques.

METHODS

In this systematic review and meta-analysis, we searched PubMed, Embase, the Cochrane Library, and LILACS for studies published from database inception to Dec 31, 2022, investigating the sensitivity and specificity of diagnostic tests for S haematobium and S mansoni infections against Kato-Katz thick smears or urine microscopy (reference tests) involving adults (aged ≥18 years), school-aged children (aged 7 to 18 years), or preschool-aged children (aged 1 month to 7 years). We extracted raw data on true positives, true negatives, false positives, and false negatives for the diagnostic tests and data on the number of participants, study authors, publication year, journal, study design, participants' age and sex, prevalence of Schistosoma infection, and treatment status. To account for imperfect reference tests, we used a hierarchical Bayesian latent class meta-analysis to model test accuracy.

FINDINGS

Overall, we included 121 studies, assessing 28 different diagnostic techniques. Most studies (103 [85%] of 121) were done in Africa, 14 (12%) in South America, one (1%) in Asia, and one (1%) in an unknown country. Compared with the reference test, Kato-Katz thick smears, circulating cathodic antigen urine cassette assay version 1 (CCA1, 36 test comparisons) had excellent sensitivity (95% [95% credible interval 88-99]) and reasonable specificity (74% [63-83]) for S mansoni. ELISA-based tests had a performance comparable to circulating cathodic antigen, but there were few available test comparisons. For S haematobium, proteinuria (42 test comparisons, sensitivity 73% [62-82]; specificity 94% [89-98]) and haematuria (75 test comparisons, sensitivity 85% [80-90]; specificity 96% [92-99]) reagent strips showed high specificity, with haematuria reagent strips having better sensitivity. Despite limited data, nucleic acid amplification tests (NAATs; eg, PCR or loop-mediated isothermal amplification [LAMP]) showed promising results with sensitivity estimates above 90%. We found an unclear risk of bias of about 70% in the use of the reference or index tests and of 50% in patient selection. All analyses showed substantial heterogeneity (I2>80%).

INTERPRETATION

Although NAATs and immunological diagnostics show promise, the limited information available precludes drawing definitive conclusions. Additional research on diagnostic accuracy and cost-effectiveness is needed before the replacement of conventional tests can be considered.

FUNDING

WHO and Luxembourg Institute of Health.

Current and upcoming point-of-care diagnostics for schistosomiasis

Point-of-care (POC) diagnostics are simple and effective portable tools that can be used for fast mapping of helminthic diseases and monitoring control programs. Most POC tests (POCTs) available for schistosomiasis diagnosis are lateral flow immunoassays (LFIAs). The emergence of simple and rapid DNA isolation methods, along with isothermal nucleic acid amplification strategies - for example, loop-mediated isothermal amplification (LAMP) and recombinase polymerase amplification (RPA) - and recent clustered regularly interspaced short palindromic repeats (CRISPR)-based diagnostic methods facilitate the development of molecular-based POC diagnostics for schistosomiasis. Furthermore, smartphone-based techniques increase real-time connectivity and readout accuracy of POCTs. This review discusses the recent advances in immunological-, molecular-based POCTs and mobile phone microscopes for the diagnosis/screening of schistosomiasis.

A Mini-Review on Elisa-Based Diagnosis of Schistosomiasis

BACKGROUND

Schistosomiasis is a neglected tropical parasitic disease caused by trematode worms of the genus schistosoma, which affects approximately 240 million people worldwide. the diagnosis of the disease can be performed by parasitological, molecular, and/or immunological methods, however, the development of new diagnostic methods still essential to guide policy decisions, monitor disease trends and assess the effectiveness of interventions.

OBJECTIVE

in this sense, the current work summarizes the findings of a systematic review regarding antigens applied in the enzyme-linked immunosorbent assay test, which were patented and published over the last ten years.

METHODS

the literature search strategy used medical subject heading (mesh) terms to define as descriptors. "schistosoma mansoni" was used in arrangement with the descriptors "immunoassay", "enzyme-linked immunosorbent assay", "elisa", and "antigens", using the "and" connector. the patent search was done using keywords, including diagnosis and schistosoma or schistosomiasis or schistosome. several databases were employed for the patent search, such as intellectual property national institute; european patent office; the united states patent and trademark office; patent scope, and google patents.

RESULTS

forty-one articles were retrieved, of which only five met the eligibility criteria. seventeen patents were taken from the databases, and a brief description of the most relevant inventions is given here.

CONCLUSION

schistosomiasis is considered the most important helminthic disease in worldwide. therefore, it is important to of searching for and develops diagnostic methods based on serology to reduce morbidity and mortality caused by the disease.

A Miniature Biomedical Sensor for Rapid Detection of Schistosoma japonicum Antibodies

Schistosomiasis, typically characterized by chronic infection in endemic regions, has the potential to affect liver tissue and pose a serious threat to human health. Detecting and screening for this disease early on is crucial for its prevention and control. However, existing methods encounter challenges such as low sensitivity, time-consuming processes, and complex sample handling. To address these challenges, we report a soluble egg antigen (SEA)-based functionalized gridless and meander-type AlGaN/GaN high electron mobility transistors (HEMT) sensor for the highly sensitive detection of antibodies to Schistosoma japonicum. Immobilization of the self-assembled membrane on the gate surface was verified using a semiconductor parameter analyzer, scanning electron microscope (SEM), and atomic force microscopy (AFM). The developed biosensor demonstrates remarkable performance in detecting anti-SEA, exhibiting a linear concentration range of 10 ng/mL to 100 μg/mL and a sensitivity of 0.058 mA/log (ng/mL). It also exhibits similar excellent performance in serum systems. With advantages such as rapid detection, high sensitivity, miniaturization, and label-free operation, this biosensor can fulfill the requirements for blood defense.

Emerging biomedical tools for biomarkers detection and diagnostics in schistosomiasis

Schistosomiasis is a neglected disease that strikes many people from tropical and subtropical countries where there are not satisfactory sanitation and wide access to clean water. Schistosoma spp., the causative agents of schistosomiasis, exhibit a quite complex life cycle that involves two hosts (humans and snails, respectively, the definitive and the intermediate), and five evolutive forms: cercariae (human infective form), schistosomula, adult worms, eggs, and miracidia. The techniques to diagnose schistosomiasis still have various limitations, mainly regarding low-intensity infections. Although various mechanisms associated with schistosomiasis have already been evidenced, there is still a need to fulfill the comprehension of this disease, especially to prospect for novel biomarkers to improve its diagnosis. Developing methods with more sensitivity and portability to detect the infection is valuable to reach schistosomiasis control. In this context, this review has gathered information not only on schistosomiasis biomarkers but also on emerging optical and electrochemical tools proposed in selected studies from about the last ten years. Aspects of the assays regarding the sensibility, specificity, and time needed for detecting diverse biomarkers are described. We hope this review can guide future developments in the field of schistosomiasis, contributing to improving its diagnosis and eradication.

A review of serological tests available in Brazil for intestinal schistosomiasis diagnosis

The World Health Organization (WHO) roadmap and recommendations for elimination of schistosomiasis were recently updated. With significant reductions in the prevalence and intensity of schistosomiasis infections worldwide, there is a need for more sensitive diagnostic methods. There are a few remaining transmission hotspots in Brazil, although low endemicity settings comprise most of the endemic localities. For the latter, serology may represent a tool for population screening which could help eliminate transmission of schistosomiasis. Here, we review serology tests currently available in Brazil from both public health and private laboratories: immunofluorescent antibody tests (IFATs) on adult worm sections and enzyme-linked immunosorbent assays (ELISAs) with soluble egg and adult worm antigens. Both in-house and commercially available tests have received less than adequate performance evaluations. Our review of immediate basic and operational research goals may help identify local adjustments that can be made to improve control interventions aimed at elimination of schistosomiasis as a public health problem.

Diagnostic performances of Schistosoma haematobium and Schistosoma mansoni recombinant proteins, peptides and chimeric proteins antibody based tests. Systematic scoping review

BACKGROUND

Traditional diagnostic tests for schistosome infections are suboptimal, particularly when the parasite burden is low. In the present review we sought to identify recombinant proteins, peptides, and chimeric proteins with potential to be used as sensitive and specific diagnostic tools for schistosomiasis.

METHODS

The review was guided by PRISMA-ScR guidelines, Arksey and O'Malley's framework, and guidelines from the Joanna Briggs Institute. Five databases were searched: Cochrane library, PubMed, EMBASE, PsycInfo and CINAHL, alongside preprints. Identified literature were assessed by two reviewers for inclusion. A narrative summary was used to interpret the tabulated results.

RESULTS

Diagnostic performances were reported as specificities, sensitivities, and AUC. The AUC for S. haematobium recombinant antigens ranged from 0.65 to 0.98, and 0.69 to 0.96 for urine IgG ELISA. S. mansoni recombinant antigens had sensitivities ranging from 65.3% to 100% and specificities ranging from 57.4% to 100%. Except for 4 peptides which had poor diagnostic performances, most peptides had sensitivities ranging from 67.71% to 96.15% and specificities ranging from 69.23% to 100%. S. mansoni chimeric protein was reported to have a sensitivity of 86.8% and a specificity of 94.2%.

CONCLUSION

The tetraspanin CD63 antigen had the best diagnostic performance for S. haematobium. The tetraspanin CD63 antigen Serum IgG POC-ICTs had a sensitivity of 89% and a specificity of 100%. Peptide Smp_150390.1 (216-230) serum based IgG ELISA had the best diagnostic performance for S. mansoni with a sensitivity of 96.15% and a specificity of 100%. Peptides were reported to demonstrate good to excellent diagnostic performances. S. mansoni multi-peptide chimeric protein further improved the diagnostic accuracy of synthetic peptides. Together with the advantages associated with urine sampling technique, we recommend development of multi-peptide chimeric proteins urine based point of care tools.

Evaluation of schistosomula crude antigen (SCA) as a diagnostic tool for Schistosoma mansoni in low endemic human population

The study aimed to determine the potential of schistosomula crude antigen (SCA) as a diagnostic target for anti-S. mansoni antibody detection. Cercariae were transformed into schistosomula, homogenized through sonication, and then centrifuged to obtain the SCA. SCA was evaluated using ELISA and dot blots immunoassays on 30 S. mansoni infected sera samples obtained from chronic patients and 30 non-infected humans’ sera samples. Either Kato-Katz or saline gradient method or both were employed as the diagnostic reference. Dot blots immunoassay was further performed on protein eluted from 10 to 12 kDa immunoreactive band identified by Western blot analysis. The area under the ROC curve was 0.95 (AUC 0.95, CI 0.88–1.01, p < 0.0001). The sensitivity and specificity of SCA-ELISA and dot blots assays were 96.67% and 86.67% respectively. The human IgG-specific response against SCA was significantly higher in S. mansoni infected individuals (OD = 0.678 ± 0.249) compared to the non-infected population (OD = 0.235 ± 0.136) (p < 0.0001). Our study showed that SCA and its 10–12 kDa component could be useful as diagnostic tools for chronic schistosomiasis.