Potential Utility of Systemic Plasma Biomarkers for Evaluation of Pediatric Schistosomiasis in Western Kenya

Associations of poor water, sanitation, and hygiene and parasite burden with markers of environmental enteric dysfunction in preschool-age children infected with Schistosoma mansoni in Uganda

BACKGROUND

Environmental enteric dysfunction (EED) is an acquired subclinical condition of the small intestine with lasting health implications for nutritional status, linear growth and development among children. EED is characterised by structural and functional changes to the gut barrier. There are no standardised diagnostic criteria, however, a number of biomarkers have been evaluated to capture EED domains. While the causes of EED are not fully understood, risk factors include poor water, sanitation and hygiene conditions and exposure to enteric pathogens. Very few studies have evaluated the impact of schistosomiasis on EED despite repeated intestinal damage from parasite eggs passing across the gut barrier.

METHODS

In a cohort of 354 preschool-aged children aged 12-47 months with Schistosoma mansoni infection recruited from the Lake Albert region of Uganda, we assessed exposure to water, sanitation and hygiene conditions and measured markers from each EED domain: intestinal inflammation (faecal calprotectin), epithelial damage (serum intestinal fatty-acid binding-protein), increased permeability (urine lactulose to mannitol ratio and faecal alpha-1 antitrypsin) and microbial translocation (serum endotoxin core antibody).

RESULTS

In multivariable linear regression models, we found that children whose drinking water was sourced from Lake Albert had higher concentrations of intestinal fatty-acid binding-protein (β = 0.48, 95% CI 0.20-0.76, p < 0.001), and lack of toilet/latrine access was associated with higher concentrations of calprotectin (β = 0.48, 95% CI 0.18-0.78, p < 0.01). Higher schistosomiasis intensity (eggs per gram of stool) was associated with higher calprotectin (β = 0.10, 95% CI 0.02-0.17, p = 0.01), but not with other EED markers.

CONCLUSIONS

Few studies have investigated schistosomiasis-related morbidities in very young children infected with schistosomiasis. Our findings from Uganda show that poor water, sanitation and hygiene conditions and heavier schistosomiasis burden are associated with intestinal inflammation and damage, contributing to EED. Improved treatment coverage for preschool-aged children infected with schistosomiasis may reduce the burden from EED and associated long-term morbidities.

A comprehensive exploration of schistosomiasis: Global impact, molecular characterization, drug discovery, artificial intelligence and future prospects

Schistosomiasis, one of the neglected tropical diseases which affects both humans and animals, is caused by trematode worms of the genus Schistosoma. The disease is caused by several species of Schistosoma which affect several organs such as urethra, liver, bladder, intestines, skin and bile ducts. The life cycle of the disease involves an intermediate host (snail) and a mammalian host. It affects people who are in close proximity to water bodies where the intermediate host is abundant. Common clinical manifestations of the disease at various stages include fever, chills, headache, cough, dysuria, hyperplasia and hydronephrosis. To date, most of the control strategies are dependent on effective diagnosis, chemotherapy and public health education on the biology of the vectors and parasites. Microscopy (Kato-Katz) is considered the golden standard for the detection of the parasite, while praziquantel is the drug of choice for the mass treatment of the disease since no vaccines have yet been developed. Most of the previous reviews on schistosomiasis have concentrated on epidemiology, life cycle, diagnosis, control and treatment. Thus, a comprehensive review that is in tune with modern developments is needed. Here, we extend this domain to cover historical perspectives, global impact, symptoms and detection, biochemical and molecular characterization, gene therapy, current drugs and vaccine status. We also discuss the prospects of using plants as potential and alternative sources of novel anti-schistosomal agents. Furthermore, we highlight advanced molecular techniques, imaging and artificial intelligence that may be useful in the future detection and treatment of the disease. Overall, the proper detection of schistosomiasis using state-of-the-art tools and techniques, as well as development of vaccines or new anti-schistosomal drugs may aid in the elimination of the disease.

Variants of IL6, IL10, FCN2, RNASE3, IL12B and IL17B loci are associated with Schistosoma mansoni worm burden in the Albert Nile region of Uganda

BACKGROUND

Individuals genetically susceptible to high schistosomiasis worm burden may contribute disproportionately to transmission and could be prioritized for control. Identifying genes involved may guide development of therapy.

METHODOLOGY/PRINCIPAL FINDINGS

A cohort of 606 children aged 10-15 years were recruited in the Albert Nile region of Uganda and assessed for Schistosoma mansoni worm burden using the Up-Converting Particle Lateral Flow (UCP-LF) test detecting circulating anodic antigen (CAA), point-of-care Circulating Cathodic Antigen (POC-CCA) and Kato-Katz tests. Whole genome genotyping was conducted on 326 children comprising the top and bottom 25% of worm burden. Linear models were fitted to identify variants associated with worm burden in preselected candidate genes. Expression quantitative trait locus (eQTL) analysis was conducted for candidate genes with UCP-LF worm burden included as a covariate. Single Nucleotide Polymorphism loci associated with UCP-LF CAA included IL6 rs2066992 (OR = 0.43, p = 0.0006) and rs7793163 (OR = 2.0, p = 0.0007); IL21 SNP kgp513476 (OR 1.79, p = 0.0025) and IL17B SNP kgp708159 (OR = 0.35, p = 0.0028). A haplotype in the IL10 locus was associated with lower worm burden (OR = 0.53, p = 0.015) and overlapped SNPs rs1800896, rs1800871 and rs1800872. Significant haplotypes (p<0.05, overlapping significant SNP) associated with worm burden were observed in IL6 and the Th17 pathway IL12B and IL17B genes. There were significant eQTL in the IL6, IL5, IL21, IL25 and IFNG regions.

CONCLUSIONS

Variants associated with S. mansoni worm burden were in IL6, FCN2, RNASE3, IL10, IL12B and IL17B gene loci. However only eQTL associations remained significant after Bonferroni correction. In summary, immune balance, pathogen recognition and Th17 pathways may play a role in modulating Schistosoma worm burden. Individuals carrying risk variants may be targeted first in allocation of control efforts to reduce the burden of schistosomiasis in the community.

CD193 ( CCR3 ) expression by B cells correlates with reduced IgE production in paediatric schistosomiasis

We demonstrate that CD193, the eotaxin receptor, is highly expressed on circulating B cells in paediatric schistosomiasis mansoni. CD193 plays a role in directing granulocytes into sites of allergic-like inflammation in the mucosa, but little is known about its functional significance on human B cells. We sought to characterize CD193 expression and its relationship with S. mansoni infection. We found that CD193+ B cells increased with the intensity of schistosome infection. In addition, a significant negative association was observed between CD193 expression by B cells and IgE production. Decreased IgE levels are generally associated with susceptibility to re-infection. B cell stimulation with eotaxin-1 increased CD193 levels whereas IL-4 led to a reduction. This was supported by plasma levels of eotaxin-1 correlating with CD193 levels on B cells and other cells. In contrast, CD193 expression was induced on naive B cells with a combination of IL-10 and schistosome antigens. Whereas T cells had a modest increase in CD193 expression, only B cell CD193 appeared functionally chemotactic to eotaxin-1. Thus, CD193+ B cells, which co-express CXCR5, may be enroute to sites with allergic-like inflammation, such as gastrointestinal follicles, or even to Th2 granulomas, which develop around parasite eggs. Overall, our results suggest that schistosome infection may promote CD193 expression and suppress IgE via IL-10 and other undefined mechanisms related to B cell trafficking. This study adds to our understanding of why young children may have poor immunity. Nonetheless, praziquantel treatment was shown to reduce percentages of circulating CD193+ B cells lending hope for future vaccine efforts.

The role of environmental enteric dysfunction in the pathogenesis of Schistosoma mansoni-associated morbidity in school-aged children

Background

Studies have implicated schistosomiasis as a cause of intestinal barrier disruption, a salient feature of environmental enteric dysfunction (EED), as eggs translocate from the sterile bloodstream through the gut wall. We examined the longitudinal impact of praziquantel (PZQ) treatment on a) EED biomarkers and b) Insulin growth factor I (IGF-1), a key driver of childhood linear growth, since EED has been implicated in linear growth stunting.

Methodology

290 children infected with S. mansoni in Brazil were treated with PZQ at baseline. EED biomarkers lipopolysaccharide (LPS) and intestinal fatty acid binding-protein (I-FABP) were measured, as well as IGF-1 at baseline, 6 and 12-months. Multivariate regression analysis was applied to assess associations between S. mansoni intensity and plasma biomarkers (LPS, I-FABP, and IGF-1), controlling for potential confounding variables.

Principal findings

At baseline, S. mansoni infection intensities were 27.2% light, 46.9% moderate, and 25.9% heavy. LPS concentrations were significantly reduced at the 12-month visit compared to baseline (p = 0.0002). No longitudinal changes were observed for I-FABP or IGF-1 in the 6- or 12-month periods following baseline treatment. After 6-months, I-FABP concentration was significantly higher in high vs low intensity (p = 0.0017). IGF-1 concentrations were significantly lower among children with high and moderate vs low intensity infections at each study visit.

Conclusions/significance

We report that S. mansoni infection impacts LPS, I-FABP and IGF-1. These findings suggest a mechanistic role for EED in schistosomiasis-related morbidities, particularly linear growth.

Schistosoma mansoni is a tropical parasitic infection that causes intestinal schistosomiasis. In infected humans, the parasite worms shed eggs that migrate across the gut barrier, which damages intestinal structure and function. In children, intestinal schistosomiasis leads to anemia, undernutrition, and linear growth stunting. The mechanistic pathways between schistosomiasis and stunting are not fully understood, but this research explores the role of environmental enteric dysfunction (EED) in schistosomiasis-related morbidity. EED is an intestinal condition that affects children living in areas of poor water, sanitation, and hygiene and also leads to impaired growth and stunting. In a longitudinal cohort of Brazilian children infected with S. mansoni, we measured blood biomarkers of EED and linear growth at three time points over 12 months. All of the children were treated for schistosomiasis at baseline, and after 12 months, we observed a significant decrease in a marker of EED, suggesting improvement in gut integrity. We also found that children who had higher parasite egg burden at the baseline visit had lower levels of insulin-like growth factor-1, a hormone that drives growth in children. Our findings suggest that EED may play a role in schistosomiasis-related stunting and furthers our understanding for S. mansoni pathogenesis in children.