Determination of gluten immunogenic peptides for the management of the treatment adherence of celiac disease: A systematic review

BACKGROUND Gluten is a complex mixture of proteins with immunogenic peptide sequences triggering the autoimmune activity in patients with celiac disease(CeD).Gluten immunogenic peptides(GIP)are resistant to gastrointestinal digestion and are then excreted via the stool and urine.Most common detection methods applied in the follow-up visits for CeD patients such as serology tests,dietetic interviews,questionnaires,and duodenal biopsy have been proved to be inefficient,invasive,or inaccurate for evaluating gluten-free diet(GFD)compliance.Determination of excreted GIP in stool and urine has been developed as a non-invasive,direct,and specific test for GFD monitoring.AIM To summarize published literature about the clinical utility of GIP determination in comparison to the tools employed for GFD monitoring.METHODS PubMed and Web of Science searches were performed using the keywords“gluten immunogenic peptides”or“gluten immunogenic peptide”and a combination of the previous terms with“feces”,“stools”,“urine”,“celiac disease”,“gluten-free diet”,and“adherence”to identify relevant clinical studies published in English and Spanish between 2012 to January 2021.Reference lists from the articles were reviewed to identify additional pertinent articles.Published articles and abstracts reporting the clinical use of GIP determination in stool and/or urine for the follow-up of patients with CeD in comparison with other tools in use were included.Case reports,commentaries,reviews,conference papers,letters,and publications that did not focus on the aims of this review were excluded.RESULTS Total of 15 publications were found that involved the use of GIP determination in stool and/or urine to monitor the adherence to the GFD in comparison to other tools.Studies included both children and adults diagnosed with CeD and healthy volunteers.Overall,these preliminary studies indicated that this novel technique was highly sensitive for the detection of GFD transgressions and therefore could facilitate the follow-up of patients with CeD.Tools identified in this work included the CeD-specific serology,dietetic questionnaires,symptomatology,and the duodenal biopsy.Review of the literature revealed that the rates of GFD adherence may vary between 30%-93%using either stool or urine GIP determination,49%-96%by the serology,59%-94%using the dietetic questionnaires,56%-95%by the reported symptoms and 44%-76%with the duodenal biopsy.In addition,the association between the different methods and histological abnormalities(Marsh II-III)was found to be 33%-100%for GIP determination(stool and urine),25%-39%for CeD-specific serology,3%-50%for dietetic questionnaires,and 22%-28%for the symptomatology.CONCLUSION Excreted GIP detection is the precise approach for determining voluntary or involuntary gluten consumption in CeD patients preventing future complications arising from gluten exposure.

Effect of Aspergillus niger prolyl endopeptidase in patients with celiac disease on a long-term gluten-free diet

BACKGROUND The gluten-free diet(GFD)has limitations,and there is intense research in the development of adjuvant therapies.AIM To examine the effects of orally administered Aspergillus niger prolyl endopeptidase protease(AN-PEP)on inadvertent gluten exposure and symptom prevention in adult celiac disease(CeD)patients following their usual GFD.METHODS This was an exploratory,double-blind,randomized,placebo-controlled trial that enrolled CeD patients on a long-term GFD.After a 4-wk run-in period,patients were randomized to 4 wk of two AN-PEP capsules(GliadinX;AVI Research,LLC,United States)at each of three meals per day or placebo.Outcome endpoints were:(1)Average weekly stool gluten immunogenic peptides(GIP)between the run-in and end of treatments and between AN-PEP and placebo;(2)celiac symptom index(CSI);(3)CeD-specific serology;and(4)quality of life.Stool samples were collected for GIP testing by ELISA every Tuesday and Friday during run-ins and treatments.RESULTS Forty patients were randomized for the intention-to-treat analysis,and three were excluded from the per-protocol assessment.Overall,628/640(98.1%)stool samples were collected.GIP was undetectable(<0.08μg/g)in 65.6%of samples,and no differences between treatment arms were detected.Only 0.5%of samples had GIP concentrations sufficiently high(>0.32μg/g)to potentially cause mucosal damage.Median GIP concentration in the AN-PEP arm was 44.7%lower than in the run-in period.One-third of patients exhibiting GIP>0.08μg/g during run-in had lower or undetectable GIP after AN-PEP treatment.Compared with the run-in period,the proportion of symptomatic patients(CSI>38)in the AN-PEP arm was significantly lower(P<0.03).AN-PEP did not result in changes in specific serologies.CONCLUSION This exploratory study conducted in a real-life setting revealed high adherence to the GFD.The AN-PEP treatment did not significantly reduce the overall GIP stool concentration.However,given the observation of a significantly lower prevalence of patients with severe symptoms in the AN-PEP arm,further clinical research is warranted.

Aspergillus niger prolyl endopeptidase in celiac disease

We comment here on the article by Stefanolo et al entitled“Effect of Aspergillus niger prolyl endopeptidase in patients with celiac disease on a long-term gluten-free diet”,published in the World Journal of Gastroenterology.Celiac disease is a well-recognized systemic autoimmune disorder.In genetically susceptible people,the most evident damage is located in the small intestine,and is caused and worsened by the ingestion of gluten.For that reason,celiac patients adopt a gluten-free diet(GFD),but it has some limitations,and it does not prevent re-exposure to gluten.Research aims to develop adjuvant therapies,and one of the most studied alternatives is supplementation with Aspergillus niger prolyl endopeptidase protease(AN-PEP),which is able to degrade gluten in the stomach,reducing its concentration in the small intestine.The study found a high adherence to the GFD,but did not address AN-PEP as a gluten immunogenic peptide reducer,as it was only tested in patients following a GFD and not in gluten-exposing conditions.This study opens up new research perspectives in this area and shows that further study is needed to clarify the points that are still in doubt.

Potential role of the IL-33/ST2 axis in celiac disease

The IL-33/ST2 axis has been implicated in the pathogenesis of several tissue-specific autoimmune diseases. Celiac disease （CD） is the only autoimmune disease in which both the major genetic factors （HLA-DQ2/DQ8） and etiologic ones （dietary gluten） for susceptibility are known. We have measured serum levels and determined intestinal tissue expression of IL-33 and its receptor soluble ST2 in patients with CD to investigate their association with disease activity. Serum and tissue levels of both IL-33 and sST2 were significantly higher in patients with CD compared with those in control patients without CD. We show that toxic peptides extracted from barley and wheat gliadin significantly stimulate the production of IL-33 and ST2 in cultured peripheral blood mononuclear cell from celiac patients, strongly implicating the IL-33/ST2 axis in the pathogenesis of CD. The higher levels of IL-33 and its receptor ST2 in tissue and serum reflect an active inflammatory state and may represent a potential biomarker for disease activity. A better understanding of IL-33/ ST2 release, mode of action, and regulation will be crucial to develop therapeutics that target the IL-33/ST2 pathway to treat CD.