Interferon-gamma released by gluten-stimulated celiac disease-specific intestinal T cells enhances the transepithelial flux of gluten peptides

Review article: therapeutic targets for the pharmacologic management of coeliac disease-the future beyond a gluten-free diet

BACKGROUND

Coeliac disease (CeD) is an immune-mediated small bowel enteropathy resulting from dietary gluten exposure. Presently, the only effective treatment is adoption of a gluten-free diet (GFD), although strict adherence is challenging to maintain, and inadvertent gluten exposures are inevitable for most patients. Hence, there is substantial interest in drug development in CeD and multiple novel therapies are under investigation.

AIMS

To review existing and upcoming clinical trial programmes for pharmacologic agents for CeD.

METHODS

A narrative review was performed, informed by a search of MEDLINE, Embase, the Cochrane CENTRAL Library and clinicaltrials.gov.

RESULTS

We summarise the pathophysiology of CeD and the specific steps that are potentially amenable to pharmacologic treatment. We evaluate the evidence supporting existing and future drug targets, including trials of peptidases, gluten sequestrants, tight junction regulators, anti-transglutaminase 2 therapies, immune tolerizing agents, advanced biologics and small molecules, and microbiome-targeted strategies. We highlight unique considerations for conducting CeD trials, including identifying appropriate study populations, assessing results in the context of a gluten challenge, and interpreting CeD-specific clinical and histologic outcomes. Understanding these factors is crucial for accurately appraising the evidence. Finally, we outline what the future of CeD therapy may hold with the introduction of pharmacotherapies.

CONCLUSIONS

There is a need for pharmacologic options for CeD, either used adjunctively with a GFD for accidental or intentional gluten exposures or for refractory disease. Multiple promising agents are in development, and these trials are likely to lead to approvals for the first generation of pharmacologic agents for CeD within the next 5 years.

Human Leukocyte Antigen (HLA) Haplotype Does Not Influence the Inflammatory Pattern of Duodenal Lymphocytosis Linked to Irritable Bowel Syndrome

Background and objectives: Duodenal lymphocytosis (DL) is a condition characterized by enhanced infiltration of intraepithelial lymphocytes (IELs) in the duodenal mucosa, and it can be linked to both gluten- and non-gluten-related diseases, such as irritable bowel syndrome (IBS). Materials and methods: We retrospectively selected patients with DL linked to IBS. Formalin-embedded biopsy samples of the duodenum were collected. CD3 lymphocyte immunohistochemistry was used for IELs. The real-time polymerase chain reaction was used to quantify the amount of mRNA coding for tissue transglutaminase 2 (tTG2), interferon-gamma (IFNγ), toll-like receptor 2 (TLR2), and myeloid differentiation primary response 88 (MyD88). All subjects underwent DQ2-8 haplotype analysis. Controls were represented by subjects with IBS without DL. Results: Thirty-two patients with IBS-DL were retrospectively recruited. Fourteen subjects (43.8%) had a DQ2-8 haplotype. DQ2-8 positive subjects had similar levels compared to negative ones for tTG2, IFNγ, TLR2, and MyD88. Cigarette smoke did not influence molecular expression in our study. Smokers had a statistically higher IELs count than non-smokers (54.2 ± 7.7 vs. 36.0 ± 8.8, p < 0.001). A significant, direct correlation between IELs and duodenal expression of IFNγ was found (r = 0.36, p = 0.04). Conclusions: IBS with DL showed higher expression of inflammatory markers than controls, but DQ2-8 haplotype did not seem to affect their expression. Smoking might increase IELs infiltration.

CX3CL1-CX3CR1 Axis: A New Player in Coeliac Disease Pathogenesis

Background: The CX3CL1–CX3CR1 axis has been related to numerous diseases. The aim of our study was to investigate its involvement in coeliac disease (CD) pathogenesis, particularly in the early phase of the disease. Methods: We collected peripheral blood from CD patients and controls, enrolled in a 3-day gluten challenge, to study soluble CX3CL1, I-TAC and MIG by Luminex, CX3CL1 and CX3CR1 gene expression by qPCR, and CX3CR1 protein expression in monocytes and CD8⁺, CD4⁺ and γδ⁺ T cells, by flow cytometry. We also analysed the expression of the CX3CL1 and CX3CR1 mRNA and protein in the duodenal biopsies of CD patients with active and treated disease, and in non-CD control individuals, by qPCR and immunohistochemistry. Results: After the gluten challenge, increased levels of CX3CL1, I-TAC and MIG proteins were observed in the peripheral blood of CD patients, with no changes in CX3CL1 mRNA, or CX3CR1 mRNA and protein. Regarding duodenal tissue, CX3CL1 was absent or barely present in the superficial and basal epithelium of CD patients, contrasting with the moderate to high levels present in controls. Conclusions: CX3CL1 seems to be involved in the appearance and progression of CD, and it appears to be a potential diagnostic biomarker. Its use as an alternative therapeutic target in CD deserves further research.

Lipid profile, atherogenic indices, and their relationship with epicardial fat thickness and carotid intima-media thickness in celiac disease

OBJECTIVE:

In this study, we aimed to investigate the presence of subclinical atherosclerosis by measuring epicardial fat thickness (EFT) and carotid intima–media thickness (cIMT), evaluate low-level inflammation with high-sensitivity C-reactive protein (hsCRP), and evaluate whether there is a relationship among lipid profile, atherogenic indices, and hsCRP with these subclinical atherosclerosis markers in patients with celiac disease (CD).

METHODS:

After exclusion and inclusion criteria were applied, 31 patients with CD (24 female, mean age: 39.4±12.3 years) and 32 healthy controls (21 female, mean age: 39.5±4.4 years), totally 63 cases, were recruited. Subclinical atherosclerosis was evaluated with EFT by transthoracic echocardiography and cIMT by ultrasonography. Inflammatory markers including erythrocyte sedimentation rate (ESR), hsCRP, and lipid profile were recorded. Also, atherogenic indices were calculated: Castelli risk index I and II (TG/HDL-c and LDL-c/HDL-c, respectively), atherogenic index of plasma (AIP; logarithm TG/HDL-c), non-HDL-c (TG-HDL-c), and atherogenic coefficient (AC; non-HDL-c/HDL-c).

RESULTS:

EFT was significantly higher in the CD group (0.49±0.10 vs. 0.49±0.09; p-value: 0.02). Although cIMT was higher in the patient group, it did not reach statistical significance (0.51±0.08, 0.47±0.08; p-value: 0.10). HDL cholesterol level was found to be significantly lower (42.0±8.8 vs. 50.0±13.7; p-value: 0.01), and the plasma atherogenic index was found to be significantly higher in the patient group (0.98±0.50 vs. 0.62±0.64; p-value: 0.02). hsCRP (3.51±3.18 vs. 1.92±1.40; p-value: 0.02) and ESR (17.2±12.8 with 9.7±3.1; p-value: 0.01) were found to be significantly higher in the CD group. Although there was a significant positive correlation between EFT and hsCRP (r: 0.453; p-value: 0.01), there was a significant negative correlation between cIMT and HDL-cholesterol (−0.339; p-value: 0.05), and a significant positive correlation with the other components of the atherogenic index was found.

CONCLUSION:

The risk of atherosclerosis has been increased in patients with CD. Chronic inflammation may be responsible for this increase along with atherogenic indices.

Nondietary Therapies for Celiac Disease

Celiac disease (CD) is an autoimmune enteropathy triggered by gluten. Gluten-free diets can be challenging because of their restrictive nature, inadvertent cross-contaminations, and the high cost of gluten-free food. Novel nondietary therapies are at the preclinical stage, clinical trial phase, or have already been developed for other indications and are now being applied to CD. These therapies include enzymatic gluten degradation, binding and sequestration of gluten, restoration of epithelial tight junction barrier function, inhibition of tissue transglutaminase-mediated potentiation of gliadin oligopeptide immunogenicity or of human leukocyte antigen-mediated gliadin presentation, induction of tolerance to gluten, and antiinflammatory interventions.

Variable Immunogenic Potential of Wheat: Prospective for Selection of Innocuous Varieties for Celiac Disease Patients via in vitro Approach

Celiac Disease (CD) is a multifactorial, autoimmune enteropathy activated by cereal proteins in genetically predisposed individuals carrying HLA DQ2/8 genes. A heterogenous gene combination of the cereal prolamins is documented in different wheat genotypes, which is suggestive of their variable immunogenic potential. In the current study, four wheat varieties (C591, C273, 9D, and K78) identified via in silico analysis were analyzed for immunogenicity by measuring T-cell proliferation rate and levels of inflammatory cytokines (Interferon-γ and Tumor Necrosis Factor-α). Peripheral Blood Mononuclear Cells and biopsy derived T-cell lines isolated from four CD patients in complete remission and two controls were stimulated and cultured in the presence of tissue transglutaminase activated pepsin-trypsin (PT) digest of total gliadin extract from test varieties. The immunogenicity was compared with PBW 621, one of the widely cultivated wheat varieties. Phytohaemagglutinin-p was taken as positive control, along with unstimulated cells as negative control. Rate of cell proliferation (0.318, 0.482; 0.369, 0.337), concentration of IFN- γ (107.4, 99.2; 117.9, 99.7 pg/ml), and TNF- α (453.8, 514.2; 463.8, 514.2 pg/ml) was minimum in cultures supplemented with wheat antigen from C273, when compared with other test varieties and unstimulated cells. Significant difference in toxicity levels among different wheat genotypes to stimulate celiac mucosal T-cells and PBMC's was observed; where C273 manifested least immunogenic response amongst the test varieties analyzed.

Translational Chemistry Meets Gluten-Related Disorders

Gluten‐related disorders are a complex group of diseases that involve the activation of the immune system triggered by the ingestion of gluten. Among these, celiac disease, with a prevalence of 1 %, is the most investigated, but recently, a new pathology, named nonceliac gluten sensitivity, was reported with a general prevalence of 7 %. Finally, there other less‐prevalent gluten‐related diseases such as wheat allergy, gluten ataxia, and dermatitis herpetiformis (with an overall prevalence of less than 0.1 %). As mentioned, the common molecular trigger is gluten, a complex mixture of storage proteins present in wheat, barley, and a variety of oats that are not fully degraded by humans. The most‐studied protein related to disease is gliadin, present in wheat, which possesses in its sequence many pathological fragments. Despite a lot of effort to treat these disorders, the only effective method is a long‐life gluten‐free diet. This Review summarizes the actual knowledge of gluten‐related disorders from a translational chemistry point of view. We discuss what is currently known from the literature about the interaction of gluten with the gut and the critical host responses it evokes and, finally, connect them to our current and novel molecular understanding of the supramolecular organization of gliadin and the 33‐mer gliadin peptide fragment under physiological conditions.

Selected Probiotic Lactobacilli Have the Capacity To Hydrolyze Gluten Peptides during Simulated Gastrointestinal Digestion

The aim of this study was to demonstrate the capacity of probiotic lactobacilli to hydrolyze immunogenic gluten peptides. Eighteen commercial strains of probiotic lactobacilli with highly variable peptidase activity (i.e., aminopeptidase N, iminopeptidase, prolyl endopeptidyl peptidase, tripeptidase, prolidase, prolinase, and dipeptidase), including toward Pro-rich peptides, were tested in this study. Ten probiotic strains were selected on the basis of their specific enzyme activity. When pooled, these 10 strains provided the peptidase portfolio that is required to completely degrade the immunogenic gluten peptides involved in celiac disease (CD). The selected probiotic mixture was able to completely hydrolyze well-known immunogenic epitopes, including the gliadin 33-mer peptide, the peptide spanning residues 57 to 68 of the α9-gliadin (α9-gliadin peptide 57-68), A-gliadin peptide 62-75, and γ-gliadin peptide 62-75. During digestion under simulated gastrointestinal conditions, the pool of 10 selected probiotic lactobacilli strongly hydrolyzed the wheat bread gluten (ca. 18,000 ppm) to less than 10 ppm after 360 min of treatment. As determined by multidimensional chromatography (MDLC) coupled to nanoelectrospray ionization (nano-ESI)-tandem mass spectrometry (MS/MS), no known immunogenic peptides were detected in wheat bread that was digested in the presence of the probiotics. Accordingly, the level of cytokines (interleukin 2 [IL-2], IL-10, and interferon gamma [IFN-γ]) produced by duodenal biopsy specimens from CD patients who consumed wheat bread digested by probiotics was similar to the baseline value (negative control). Probiotics that specifically hydrolyze gluten polypeptides could also be used to hydrolyze immunogenic peptides that contaminate gluten-free products. This could provide a new and safe adjunctive therapy alternative to the gluten-free diet (GFD).IMPORTANCE This study confirmed that probiotic Lactobacillus strains have different enzymatic abilities for hydrolyzing polypeptides, including the Pro-rich epitopes involved in the pathology of CD. Ten lactobacilli with complementary peptidase activities that hydrolyze gluten peptides during simulated gastrointestinal digestion were selected and tested. The results collected showed the potential of probiotic formulas as novel dietary treatments for CD patients.

Sarcoidosis in celiac disease: A page written by genetic variants in IL-18 miRNAs target site?

Sarcoidosis is a chronic idiopathic granulomatous disease. Interleukin-18 (IL-18) has been strongly implicated in the pathogenesis of sarcoidosis. Sarcoidosis shows characteristic microRNAs (miRNAs) profiles. MiRNAs have recently emerged as a new class of modulators of gene expression. MiRNAs are involved in susceptibility to a number of autoimmune diseases promoting and inhibiting the gene expression of different Th1 pro-inflammatory cytokines including IL18. Sarcoidosis has been connected with a variety of autoimmune disorders including celiac disease (CD). CD is a chronic, immune-mediated condition of the small intestine caused by permanent intolerance to dietary gluten. IL-18 has been reported to play an important role in inducing and maintaining inflammation after gluten exposure. MiRNAs expression is significantly altered in CD patients. We hypothesize that sarcoidosis and CD may be the result of common genetic variants in IL-18 miRNA target site.

Coeliac Disease - New Pathophysiological Findings and Their Implications for Therapy

Coeliac disease (CD) is one of the most common diseases worldwide, resulting from a combination of environmental (gluten) and genetic (human leucocyte antigen (HLA) and non-HLA genes) factors. Depending on the geographical location, the prevalence of CD has been estimated to approximate 0.5-1%. The only treatment currently available for CD is a gluten-free diet (GFD) excluding gluten-containing cereals such as wheat, rye, and barley, and other foodstuffs with natural or added gluten. However, adherence rates and patient acceptance are often poor. Moreover, even in fully adherent patients, the diet may fail to induce clinical or histological improvement. Hence, it is unsurprising that studies show CD patients to be highly interested in non-dietary alternatives. The following review focuses on current pathophysiological concepts of CD, spotlighting those pathways which may serve as new possible, non-dietary therapeutic targets in the treatment of CD.

Mucosal molecular pattern of tissue transglutaminase and interferon gamma in suspected seronegative celiac disease at marsh 1 and 0 stages

BACKGROUND/AIM

In celiac disease (CD), there is increased mRNA coding for tissue transglutaminase (tTG) and interferon gamma (IFNα). In seronegative celiac patients, the mucosal immune complexes anti-tTG IgA/tTG are found. We assayed tTG- and IFNα-mRNA in the mucosa of patients with a clinical suspicion of seronegative CD and correlated the values with intraepithelial CD3 lymphocytes (IELs).

MATERIALS AND METHODS

Distal duodenum specimens from 67 patients were retrieved and re-evaluated for immunohistochemically proven CD3 IELs. Five 10 μm sections were used for the extraction and assay of tTG and IFNα coding mRNA levels using reverse transcriptase real-time polymerase chain reaction (RT-PCR). Samples from 15 seropositive CD patients and 15 healthy subjects were used as positive and negative controls. Results were expressed as fold-change.

RESULTS

Our series was divided into three groups based on IEL count: >25 (14 patients: group A), 15-25 (26 patients: group B), and 0-15 (27 patients: Group C). tTG-mRNA levels were (mean ± SD): CD = 9.8 ± 2.6; group A = 10.04 ± 4.7; group B = 4.99 ± 2.3; group C = 2.26 ± 0.8, controls = 1.04 ± 0.2 (CD = group A > group B > group C = controls). IFNα-mRNA levels were: CD = 13.4 ± 3.6; group A = 7.28 ± 3.6; group B = 4.45 ± 2.9; group C = 2.06 ± 1.21, controls = 1.04 ± 0.4.

CONCLUSIONS

Our results suggest that tTG- and IFNγmRNA levels are increased in both seropositive and potential seronegative patients with CD, showing a strong correlation with the CD3 IEL count at stage Marsh 1. An increase in both molecules is found even when IELs are in the range 15-25 (Marsh 0), suggesting the possibility of a "gray zone" inhabited by patients which should be closely followed up in gluten-related disorders.

Current and emerging therapy for celiac disease

At present, strict and lifelong gluten-free diet is the only effective treatment for celiac disease. Even small amounts of gluten (50 mg/day) can be immunogenic; therefore all food and food items and drugs that contain gluten and its derivatives must be eliminated completely from the diet. While prescribing gluten-free diet is easy; the key to the success is the dietary counseling by a nutrition specialist and maintenance of adherence to GFD by the patient. In recent times, a number of targets to halt the process of immunological injury have been explored to find out alternative treatment for celiac disease. These targets include exploration of ancient wheat if they are less immunogenic, intra-luminal digestion of gluten using prolylendopeptidases, pretreatment of whole gluten with bacterial-derived peptidase before ingestion; prevention of passage of immunogenic peptides through the tight junctions such as zonulin antagonists, Blocking of HLA-DQ2 to prevent binding of immunogenic peptides, inhibition of transglutaminase 2, immune-modulation, and induction of tolerance to gluten using gluten tolerizing vaccines, use of gluten-sequestering polymers, use of anti-inflammatory drugs (glucocorticoids, budesonides) and anti-cytokines such as anti TNF-α, and anti-interleukin-15. While many of these targets are still in the pre-clinical phase, some of them including zonulin antagonist and endopeptidases have already reached phase II and phase III clinical trials. Furthermore, while these targets appear very exciting; they at best are likely to be used as adjunctive therapy rather than a complete replacement for gluten-free diet.

Structural analysis and Caco-2 cell permeability of the celiac-toxic A-gliadin peptide 31-55

Celiac disease is a chronic enteropathy caused by the ingestion of wheat gliadin and other cereal prolamines. The synthetic peptides 31-43 (P31-43) and 31-49 (P31-49) from A-gliadin are considered to be model peptides for studying innate immunity in celiac disease. Our previous study demonstrated that P31-43 and P31-49 are encrypted within peptide 31-55 (P31-55), which is naturally released from gastropancreatic digestion and is not susceptible to hydrolysis by brush border membrane enzymes. Here, we analyzed the permeability of P31-55 through the epithelial cell layer of confluent Caco-2 cells using high-performance liquid chromatography, mass spectrometry, and fluorescence-activated cell sorting. Twenty-three percent of the P31-55 added to the apical chamber was transported to the basolateral chamber after 4 h of incubation without being degraded by hydrolysis. Treatment of Caco-2 cells with whole gliadin digests extracted from a common wheat cultivar increased the epithelial P31-55 translocation by approximately 35%. Moreover, we observed an atypical chromatographic profile consisting of a double peak. Chromatography using different column temperatures and circular dichroism highlighted the presence of more conformational structures around the amide bond of the two adjacent prolines 38 and 39. These findings confirm that P31-55 is gastrointestinally resistant and is permeable across a Caco-2 monolayer. Moreover, we hypothesize that the various conformations of P31-55 may play a role in the activation of innate immunity.

Review article: coeliac disease, new approaches to therapy

BACKGROUND

Coeliac disease is managed by life-long gluten withdrawal from the diet. However, strict adherence to a gluten-free diet is difficult and is not always effective. Novel therapeutic approaches are needed to supplement or even replace the dietary treatment.

AIM

To review recent advances in new therapeutic options for coeliac disease.

METHODS

A literature search was performed on MEDLINE, EMBASE, Web of Science, Scopus, DDW.org and ClinicalTrials.gov for English articles and abstracts. The search terms used included, but not limited to, 'Celiac disease', 'new', 'novel', 'Advances', 'alternatives' and 'Drug therapy'. The cited articles were selected based on the relevancy to the review objective.

RESULTS

Several new therapeutic approaches for coeliac disease are currently under development by targeting its underlying pathogenesis. Alternative therapies range from reproduction of harmless wheat strains to immunomodulatory approaches. Some of these therapies such as enzymatic cleavage of gluten and permeability inhibitors have shown promise in clinical studies.

CONCLUSIONS

Gluten-free diet is still the only practical treatment for patients with coeliac disease. Novel strategies provide promise of alternative adjunctive approaches to diet restriction alone for patients with this disorder.

Role of transglutaminase 2 in celiac disease pathogenesis

A number of lines of evidence suggest that transglutaminase 2 (TG2) may be one of the earliest disease-relevant proteins to encounter immunotoxic gluten in the celiac gut. These and other investigations also suggest that the reaction catalyzed by TG2 on dietary gluten peptides is essential for the pathogenesis of celiac disease. If so, several questions are of critical significance. How is TG2 activated in the celiac gut? What are the disease-specific and general consequences of activating TG2? Can local inhibition of TG2 in the celiac intestine suppress gluten induced pathogenesis in a dose-responsive manner? And what are the long-term consequences of suppressing TG2 activity in the small intestinal mucosa? Answers to these questions will depend upon the development of judicious models and chemical tools. They also have the potential of yielding powerful next-generation drug candidates for treating this widespread but overlooked chronic disease.

In vitro models for gluten toxicity: relevance for celiac disease pathogenesis and development of novel treatment options

In genetically predisposed individuals, dietary gluten in wheat, rye and barley triggers celiac disease, a systemic autoimmune disorder hallmarked by an extensive small-bowel mucosal immune response. The current conception of celiac disease pathogenesis is that it involves components of both innate and adaptive immunity whose activation typically leads to small-bowel villous atrophy with crypt hyperplasia. Currently, the only effective treatment for celiac disease is a strict lifelong gluten-free diet excluding all wheat-, rye- and barley-containing food products. During the diet, the clinical symptoms improve and the small-bowel mucosal damage recovers, while re-introduction of gluten into the diet leads to re-appearance of the symptoms and deterioration of the small-bowel mucosal architecture. In view of the restricted nature of the diet, alternative treatment is warranted. Improved understanding of the molecular basis of celiac disease has enabled researchers to suggest other therapeutic approaches. Although there is no animal model reproducing all features of celiac disease, the use of in vitro approaches including a variety of cell lines and the celiac patient small-bowel mucosal biopsy organ culture has generated knowledge about pathogenesis of celiac disease. In these culture systems, gluten induces different effects that can be quantified, thus also enabling studies concerning the efficacy of candidate therapeutic compounds for celiac disease. This review describes the intestinal epithelial cell models, celiac patient T-cell lines and clones, as well as the small-bowel mucosal organ culture methods widely used in studies of celiac disease, and summarizes the major findings obtained with these systems.

Interferon-γ activates transglutaminase 2 via a phosphatidylinositol-3-kinase-dependent pathway: implications for celiac sprue therapy

The mechanism for activation of extracellular transglutaminase 2 (TG2) in the small intestine remains a fundamental mystery in our understanding of celiac sprue pathogenesis. Using the T84 human enterocytic cell line, we show that interferon-γ (IFN-γ), the predominant cytokine secreted by gluten-reactive T cells in the celiac intestine, activates extracellular TG2 in a dose-dependent manner. IFN-γ mediated activation of TG2 requires phosphatidylinositol-3-kinase (PI3K) activity, but is uninfluenced by a number of other kinases reported to be active in T84 cells. Pharmacological inhibition of PI3K in the presence of IFN-γ prevents TG2 activation as well as the previously characterized increase in transepithelial permeability. Our findings therefore establish PI3K as an attractive target for celiac sprue therapy, a possibility that is underscored by the encouraging safety profiles of several PI3K inhibitors undergoing human clinical trials.

New and developing therapies for celiac disease

The treatment for celiac disease, a removal of gluten in the diet, is safe and effective for the vast majority of patients. There is a large body of evidence that the diagnosis and treatment of those with celiac disease ensures considerable health benefits. Although a gluten-free diet is the principal treatment for celiac disease, it is relatively expensive, inconvenient and difficult to adhere to. For these reasons, there is interest in developing alternative therapies. Emerging research for the treatment of celiac disease has focused on three areas: to decrease gluten exposure, to modify intestinal permeability and to modulate immune activation. Therapies developed thus far consist of enzymes designed to digest gluten and the use of inhibitors of paracellular permeability to decrease the migration of gluten peptides into the lamina propria. Other potential therapeutic maneuvers include the binding of gluten by polymers, the use of tissue transglutaminase (TTG) inhibitors and DQ2 or DQ8 blockers, or modulation of cytokine production. While all represent new and exciting therapies, an ideal therapy should have virtually no side effects similar to a gluten-free diet. A pharmaceutical agent may be used on an intermittent basis, such as following occasional gluten exposure or on a chronic basis to mitigate the effects of potential inadvertent ingestion of gluten.

Epithelial transport and deamidation of gliadin peptides: a role for coeliac disease patient immunoglobulin A

In coeliac disease, the intake of dietary gluten induces small-bowel mucosal damage and the production of immunoglobulin (Ig)A class autoantibodies against transglutaminase 2 (TG2). We examined the effect of coeliac patient IgA on the apical-to-basal passage of gluten-derived gliadin peptides p31-43 and p57-68 in intestinal epithelial cells. We demonstrate that coeliac IgA enhances the passage of gliadin peptides, which could be abolished by inhibition of TG2 enzymatic activity. Moreover, we also found that both the apical and the basal cell culture media containing the immunogenic gliadin peptides were able to induce the proliferation of deamidation-dependent coeliac patient-derived T cells even in the absence of exogenous TG2. Our results suggest that coeliac patient IgA could play a role in the transepithelial passage of gliadin peptides, a process during which they might be deamidated.

Visualization of transepithelial passage of the immunogenic 33-residue peptide from alpha-2 gliadin in gluten-sensitive macaques

Background

Based on clinical, histopathological and serological similarities to human celiac disease (CD), we recently established the rhesus macaque model of gluten sensitivity. In this study, we further characterized this condition based on presence of anti-tissue transglutaminase 2 (TG2) antibodies, increased intestinal permeability and transepithelial transport of a proteolytically resistant, immunotoxic, 33-residue peptide from α₂-gliadin in the distal duodenum of gluten-sensitive macaques.

Methodology/Principal Findings

Six rhesus macaques were selected for study from a pool of 500, including two healthy controls and four gluten-sensitive animals with elevated anti-gliadin or anti-TG2 antibodies as well as history of non-infectious chronic diarrhea. Pediatric endoscope-guided pinch biopsies were collected from each animal's distal duodenum following administration of a gluten-containing diet (GD) and again after remission by gluten-free diet (GFD). Control biopsies always showed normal villous architecture, whereas gluten-sensitive animals on GD exhibited histopathology ranging from mild lymphocytic infiltration to villous atrophy, typical of human CD. Immunofluorescent microscopic analysis of biopsies revealed IgG+ and IgA+ plasma-like cells producing antibodies that colocalized with TG2 in gluten-sensitive macaques only. Following instillation in vivo, the Cy-3-labeled 33-residue gluten peptide colocalized with the brush border protein villin in all animals. In a substantially enteropathic macaque with “leaky” duodenum, the peptide penetrated beneath the epithelium into the lamina propria.

Conclusions/Significance

The rhesus macaque model of gluten sensitivity not only resembles the histopathology of CD but it also may provide a model for studying intestinal permeability in states of epithelial integrity and disrepair.

Noninflammatory gluten peptide analogs as biomarkers for celiac sprue

New tools are needed for managing celiac sprue, a lifelong immune disease of the small intestine. Ongoing drug trials are also prompting a search for noninvasive biomarkers of gluten-induced intestinal change. We have synthesized and characterized noninflammatory gluten peptide analogs in which key Gln residues are replaced by Asn or His. Like their proinflammatory counterparts, these biomarkers are resistant to gastrointestinal proteases, susceptible to glutenases, and permeable across enterocyte barriers. Unlike gluten peptides, however, they are not appreciably recognized by transglutaminase, HLA-DQ2, or disease-specific T cells. In vitro and animal studies show that the biomarkers can detect intestinal permeability changes as well as glutenase-catalyzed gastric detoxification of gluten. Accordingly, controlled clinical studies are warranted to evaluate the use of these peptides as probes for abnormal intestinal permeability in celiac patients and for glutenase efficacy in clinical trials and practice.