Analysis and clinical effects of gluten in coeliac disease

Preparation of pepsin trypsin digested gliadin for stimulation experiments

Celiac disease (CD) is a complex immune disorder of the intestine that developes in genetically susceptible individuals. CD develops as an intolerance to ingested gluten proteins (gliadins, secalins, hordeins and avenins), being gliadin one of the most immunogenic. Here we present a protocol for the preparation of digested gliadin for laboratory use, a fundamental axis for in vitro and in vivo stimulation studies related to celiac disease research. The importance of a scrupulous handling of materials, products and laboratory instruments to achieve a lipopolysaccharide free gliadin is explained and emphasized. Therefore, in the present chapter, a step-by-step set-up of the protocol for pepsin trypsin gliadin digestion is explained.

A Comprehensive Review of the Neurological Manifestations of Celiac Disease and Its Treatment

Celiac disease (CD) is a common chronic inflammatory disorder occurring in genetically predisposed individuals secondary to gluten ingestion. CD usually presents with gastrointestinal symptoms such as pain, bloating, flatulence, and constipation or diarrhea. However, individuals can present in a nonclassical manner with only extraintestinal symptoms. The neurological manifestations of CD include ataxia, cognitive impairment, epilepsy, headache, and neuropathy. A lifelong gluten-free diet is the current recommended treatment for CD. This review discusses the relevant neurological manifestations associated with CD and the novel therapeutics. Further research is required to get a better understanding of the underlying pathophysiology of the neurological manifestations associated with CD. Clinicians should keep CD in the differential diagnosis in individuals presenting with neurological dysfunction of unknown cause.

Targeting Induced Local Lesions in the Wheat DEMETER and DRE2 Genes, Responsible for Transcriptional Derepression of Wheat Gluten Proteins in the Developing Endosperm

Wheat is a major source of energy and nutrition worldwide, but it is also a primary cause of frequent diet-induced health issues, specifically celiac disease, for which the only effective therapy so far is strict dietary abstinence from gluten-containing grains. Wheat gluten proteins are grouped into two major categories: high-molecular-weight glutenin subunits (HMWgs), vital for mixing and baking properties, and gliadins plus low-molecular-weight glutenin subunits (LMWgs) that contain the overwhelming majority of celiac-causing epitopes. We put forth a hypothesis that eliminating gliadins and LMWgs while retaining HMWgs might allow the development of reduced-immunogenicity wheat genotypes relevant to most gluten-sensitive individuals. This hypothesis stems from the knowledge that the molecular structures and regulatory mechanisms of the genes encoding the two groups of gluten proteins are quite different, and blocking one group's transcription, without affecting the other's, is possible. The genes for gliadins and LMWgs have to be de-methylated by 5-methylcytosine DNA glycosylase/lyase (DEMETER) and an iron-sulfur (Fe-S) cluster biogenesis enzyme (DRE2) early during endosperm development to permit their transcription. In this study, a TILLING (Targeting Induced Local Lesions IN Genomes) approach was undertaken to identify mutations in the homoeologous DEMETER (DME) and DRE2 genes in common and durum wheat. Lines with mutations in these genes were obtained that displayed reduced content of immunogenic gluten proteins while retaining essential baking properties. Although our data at first glance suggest new possibilities for treating celiac disease and are therefore of medical and agronomical interest, it also shows that inducing mutations in the DME and DRE2 genes analyzed here affected pollen viability and germination. Hence there is a need to develop other approaches in the future to overcome this undesired effect.

Genome-wide identification, characteristics and expression of the prolamin genes in Thinopyrum elongatum

Background

Prolamins, unique to Gramineae (grasses), play a key role in the human diet. Thinopyrum elongatum (syn. Agropyron elongatum or Lophopyrum elongatum), a grass of the Triticeae family with a diploid E genome (2n = 2x = 14), is genetically well-characterized, but little is known about its prolamin genes and the relationships with homologous loci in the Triticeae species.

Results

In this study, a total of 19 α-gliadin, 9 γ-gliadin, 19 ω-gliadin, 2 high-molecular-weight glutenin subunit (HMW-GS), and 5 low-molecular-weight glutenin subunit (LMW-GS) genes were identified in the Th. elongatum genome. Micro-synteny and phylogenetic analysis revealed dynamic changes of prolamin gene regions and genetic affinities among Th. elongatum, Triticum aestivum, T. urartu and Aegilops tauschii. The Th. elongatum genome, like the B subgenome of T. aestivum, only contained celiac disease epitope DQ8-glia-α1/DQ8.5-glia-α1, which provided a theoretical basis for the low gluten toxicity wheat breeding. The transcriptome data of Th. elongatum exhibited differential expression in quantity and pattern in the same subfamily or different subfamilies. Dough rheological properties of T. aestivum-Th. elongatum disomic substitution (DS) line 1E(1D) showed higher peak height values than that of their parents, and DS6E(6D) exhibited fewer α-gliadins, which indicates the potential usage for wheat quality breeding.

Conclusions

Overall, this study provided a comprehensive overview of the prolamin gene family in Th. elongatum, and suggested a promising use of this species in the generation of improved wheat breeds intended for the human diet.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08088-x.

Impact and mechanism of sulphur-deficiency on modern wheat farming nitrogen-related sustainability and gliadin content

Two challenges that the global wheat industry is facing are a lowering nitrogen-use efficiency (NUE) and an increase in the reporting of wheat-protein related health issues. Sulphur deficiencies in soil has also been reported as a global issue. The current study used large-scale field and glasshouse experiments to investigate the sulphur fertilization impacts on sulphur deficient soil. Here we show that sulphur addition increased NUE by more than 20% through regulating glutamine synthetase. Alleviating the soil sulphur deficiency highly significantly reduced the amount of gliadin proteins indicating that soil sulphur levels may be related to the biosynthesis of proteins involved in wheat-induced human pathologies. The sulphur-dependent wheat gluten biosynthesis network was studied using transcriptome analysis and amino acid metabolomic pathway studies. The study concluded that sulphur deficiency in modern farming systems is not only having a profound negative impact on productivity but is also impacting on population health.

Rapid, Effective, and Versatile Extraction of Gluten in Food with Application on Different Immunological Methods

One of the main concerns in gluten analysis is to achieve efficient extraction of gluten proteins. Conventional ethanol-based extraction solutions are inefficient and, because of this, it is necessary to use reducing agents or acids for proper solubilization. The extraction recommended by CODEX Standard 118-1979 (revised 2008) utilizes Cocktail solution (patent WO 02/092633 A1). However, it is harmful with a disgusting odor and is not compatible with some immunological techniques. Here, the versatility and extraction capacity of a new Universal Gluten Extraction Solution (UGES) (patent ES 2 392 412 A1) were evaluated using different methodological conditions, food matrices, and various immunological methods. UGES includes safer compounds for both the user and the environment, and it displayed similar extraction efficiency to that of the extraction method recommended for sandwich enzyme-linked immunosorbent assay (ELISA). The extraction time was significantly reduced from 100 to 40 min, depending on the type of the sample. Furthermore, unlike the currently used solution, UGES is compatible with competitive ELISA.

From Polyclonal Sera to Recombinant Antibodies: A Review of Immunological Detection of Gluten in Foodstuff

Gluten is the ethanol-soluble protein fraction of cereal endosperms like wheat, rye, and barley. It is widely used in the food industry because of the physical-chemical properties it gives to dough. Nevertheless, there are some gluten-related diseases that are presenting increasing prevalences, e.g., celiac disease, for which a strict gluten-free diet is the best treatment. Due to this situation, gluten labeling legislation has been developed in several countries around the world. This article reviews the gluten immune detection systems that have been applied to comply with such regulations. These systems have followed the development of antibody biotechnology, which comprise three major methodologies: polyclonal antibodies, monoclonal antibodies (mAbs) derived from hybridoma cells (some examples are 401.21, R5, G12, and α-20 antibodies), and the most recent methodology of recombinant antibodies. Initially, the main objective was the consecution of new high-affinity antibodies, resulting in low detection and quantification limits that are mainly achieved with the R5 mAb (the gold standard for gluten detection). Increasing knowledge about the causes of gluten-related diseases has increased the complexity of research in this field, with current efforts not only focusing on the development of more specific and sensitive systems for gluten but also the detection of protein motifs related to pathogenicity. New tools based on recombinant antibodies will provide adequate safety and traceability methodologies to meet the increasing market demand for gluten-free products.

Directed-Mutagenesis of Flavobacterium meningosepticum Prolyl-Oligopeptidase and a Glutamine-Specific Endopeptidase From Barley

Wheat gluten proteins are the known cause of celiac disease. The repetitive tracts of proline and glutamine residues in these proteins make them exceptionally resilient to digestion in the gastrointestinal tract. These indigested peptides trigger immune reactions in susceptible individuals, which could be either an allergic reaction or celiac disease. Gluten exclusion diet is the only approved remedy for such disorders. Recently, a combination of a glutamine specific endoprotease from barley (EP-B2), and a prolyl endopeptidase from Flavobacterium meningosepticum (Fm-PEP), when expressed in the wheat endosperm, were shown to reasonably detoxify immunogenic gluten peptides under simulated gastrointestinal conditions. However useful, these "glutenases" are limited in application due to their denaturation at high temperatures, which most of the food processes require. Variants of these enzymes from thermophilic organisms exist, but cannot be applied directly due to their optimum activity at temperatures higher than 37°C. Though, these enzymes can serve as a reference to guide the evolution of peptidases of mesophilic origin toward thermostability. Therefore, a sequence guided site-saturation mutagenesis approach was used here to introduce mutations in the genes encoding Fm-PEP and EP-B2. A thermostable variant of Fm-PEP capable of surviving temperatures up to 90°C and EP-B2 variant with a thermostability of up 60°C were identified using this approach. However, the level of thermostability achieved is not sufficient; the present study has provided evidence that the thermostability of glutenases can be improved. And this pilot study has paved the way for more detailed structural studies in the future to obtain variants of Fm-PEP and EP-B2 that can survive temperatures ~100°C to allow their packing in grains and use of such grains in the food industry.

Evolving Therapy for Celiac Disease

Gluten is known to be the main triggering factor for celiac disease (CeD), an immune-mediated disorder. CeD is therefore managed using a strict and lifelong gluten-free diet (GFD), the only effective treatment available currently. However, the GFD is restrictive. Hence, efforts are being made to explore alternative therapies. Based on their mechanisms of action on various molecular targets involved in the pathogenesis of CeD, these therapies may be classified into one of the following five broad approaches. The first approach focuses on decreasing the immunogenic content of gluten, using strategies like genetically modified wheat, intra-intestinal gluten digestion using glutenases, microwave thermal treatment of hydrated wheat kernels, and gluten pretreatment with either bacterial/ fungal derived endopeptidases or microbial transglutaminase. The second approach involves sequestering gluten in the gut lumen before it is digested into immunogenic peptides and absorbed, using binder drugs like polymer p(HEMA-co-SS), single chain fragment variable (scFv), and anti- gluten antibody AGY. The third approach aims to prevent uptake of digested gluten through intestinal epithelial tight junctions, using a zonulin antagonist. The fourth approach involves tissue transglutaminase (tTG) inhibitors to prevent the enhancement of immunogenicity of digested gluten by the intestinal tTG enzyme. The fifth approach seeks to prevent downstream immune activation after uptake of gluten immunogenic peptides through the intestinal mucosal epithelial layer. Examples include HLA-DQ2 blockers that prevent presentation of gluten derived- antigens by dendritic cells to T cells, immune- tolerizing therapies like the vaccine Nexvax2 and TIMP-Glia, cathepsin inhibitors, immunosuppressants like corticosteroids, azathioprine etc., and anti-cytokine agents targeting TNF-α and interleukin-15. Apart from these approaches, research is being done to evaluate the effectiveness of probiotics/prebiotics, helminth therapy using Necator americanus, low FODMAP diet, and pancreatic enzyme supplementation in CeD symptom control; however, the mechanisms by which they play a beneficial role in CeD are yet to be clearly established. Overall, although many therapies being explored are still in the pre-clinical phase, some like the zonulin antagonist, immune tolerizing therapies and glutenases have reached phase II/III clinical trials. While these potential options appear exciting, currently they may at best be used to supplement rather than supplant the GFD.

Possible Prevention of Diabetes with a Gluten-Free Diet

Gluten seems a potentially important determinant in type 1 diabetes (T1D) and type 2 diabetes (T2D). Intake of gluten, a major component of wheat, rye, and barley, affects the microbiota and increases the intestinal permeability. Moreover, studies have demonstrated that gluten peptides, after crossing the intestinal barrier, lead to a more inflammatory milieu. Gluten peptides enter the pancreas where they affect the morphology and might induce beta-cell stress by enhancing glucose- and palmitate-stimulated insulin secretion. Interestingly, animal studies and a human study have demonstrated that a gluten-free (GF) diet during pregnancy reduces the risk of T1D. Evidence regarding the role of a GF diet in T2D is less clear. Some studies have linked intake of a GF diet to reduced obesity and T2D and suggested a role in reducing leptin- and insulin-resistance and increasing beta-cell volume. The current knowledge indicates that gluten, among many environmental factors, may be an aetiopathogenic factors for development of T1D and T2D. However, human intervention trials are needed to confirm this and the proposed mechanisms.

Development of wheat genotypes expressing a glutamine-specific endoprotease from barley and a prolyl endopeptidase from Flavobacterium meningosepticum or Pyrococcus furiosus as a potential remedy to celiac disease

Ubiquitous nature of prolamin proteins dubbed gluten from wheat and allied cereals imposes a major challenge in the treatment of celiac disease, an autoimmune disorder with no known treatment other than abstinence diet. Administration of hydrolytic glutenases as food supplement is an alternative to deliver the therapeutic agents directly to the small intestine, where sensitization of immune system and downstream reactions take place. The aim of the present research was to evaluate the capacity of wheat grain to express and store hydrolytic enzymes capable of gluten detoxification. For this purpose, wheat scutellar calli were biolistically transformed to generate plants expressing a combination of glutenase genes for prolamin detoxification. Digestion of prolamins with barley endoprotease B2 (EP-HvB2) combined with Flavobacterium meningosepticum prolyl endopeptidase (PE-FmPep) or Pyrococcus furiosus prolyl endopeptidase (PE-PfuPep) significantly reduced (up to 67%) the amount of the indigestible gluten peptides of all prolamin families tested. Seven of the 168 generated lines showed inheritance of transgene to the T₂ generation. Reversed phase high-performance liquid chromatography of gluten extracts under simulated gastrointestinal conditions allowed the identification of five T₂ lines that contained significantly reduced amounts of immunogenic, celiac disease-provoking gliadin peptides. These findings were complemented by the R5 ELISA test results where up to 72% reduction was observed in the content of immunogenic peptides. The developed wheat genotypes open new horizons for treating celiac disease by an intraluminal enzyme therapy without compromising their agronomical performance.

Identification and characterization of proteolytically resistant gluten-derived peptides

The lack of digestibility of certain gluten proteins is essential in the development of celiac disease (CD).

Identification of novel antibody-reactive detection sites for comprehensive gluten monitoring

Certain cereals like wheat, rye or barley contain gluten, a protein mixture that can trigger celiac disease (CD). To make gluten-free diets available for affected individuals the gluten content of foodstuff must be monitored. For this purpose, antibody-based assays exist which rely on the recognition of certain linear gluten sequence motifs. Yet, not all CD-active gluten constituents and fragments formed during food processing/fermentation may be covered by those tests. In this study, we therefore assayed the coverage of reportedly CD-active gluten components by currently available detection antibodies and determined the antibody-inducing capacity of wheat gluten constituents in order to provide novel diagnostic targets for comprehensive gluten quantitation. Immunizations of outbred mice with purified gliadins and glutenins were conducted and the linear target recognition profile of the sera was recorded using synthetic peptide arrays that covered the sequence space of gluten constituents present in those preparations. The resulting murine immunorecognition profile of gluten demonstrated that further linear binding sites beyond those recognized by the monoclonal antibodies α20, R5 and G12 exist and may be exploitable as diagnostic targets. We conclude that the safety of foodstuffs for CD patients can be further improved by complementing current tests with antibodies directed against additional CD-active gluten components. Currently unrepresented linear gluten detection sites in glutenins and α-gliadins suggest sequences QQQYPS, PQQSFP, QPGQGQQG and QQPPFS as novel targets for antibody generation.

Computational Characterisation and Identification of Peptides for in silico Detection of Potentially Celiac-Toxic Proteins

This work reports on in silico analysis of celiac-toxic peptide occurrence in proteins. The toxic properties of celiac disease are linked to the presence of specific amino acid sequences and the properties of their environment. The analysed celiac-toxic peptides were found to be predominated by unordered structures of random coil and β-turns. Proline and glutamine-rich amino acid sequences from hydrophilic β-turns were exposed on the surface of the precursor proteins. The sequence motifs represented by gluten peptide epitopes or tetrapeptides with surroundings seem to represent an immunodominant structure. The application of MS BLAST software enabled identification of a few fragments with high degrees of identity to the toxic peptides in one protein sequence. Rich sources of celiac-disease-potentiating peptides were wheat gliadins, barley hordeins and rye secalins as well as low-molecular weight fractions of glutenin. In addition, amino acid sequences with a high degree of identity to the toxic peptides examined were detected in maize zein, oat avenin, protein of rice, yeast and chicken muscles, as well as β-casein and galanin.

Genome-, Transcriptome- and Proteome-Wide Analyses of the Gliadin Gene Families in Triticum urartu

Gliadins are the major components of storage proteins in wheat grains, and they play an essential role in the dough extensibility and nutritional quality of flour. Because of the large number of the gliadin family members, the high level of sequence identity, and the lack of abundant genomic data for Triticum species, identifying the full complement of gliadin family genes in hexaploid wheat remains challenging. Triticum urartu is a wild diploid wheat species and considered the A-genome donor of polyploid wheat species. The accession PI428198 (G1812) was chosen to determine the complete composition of the gliadin gene families in the wheat A-genome using the available draft genome. Using a PCR-based cloning strategy for genomic DNA and mRNA as well as a bioinformatics analysis of genomic sequence data, 28 gliadin genes were characterized. Of these genes, 23 were α-gliadin genes, three were γ-gliadin genes and two were ω-gliadin genes. An RNA sequencing (RNA-Seq) survey of the dynamic expression patterns of gliadin genes revealed that their synthesis in immature grains began prior to 10 days post-anthesis (DPA), peaked at 15 DPA and gradually decreased at 20 DPA. The accumulation of proteins encoded by 16 of the expressed gliadin genes was further verified and quantified using proteomic methods. The phylogenetic analysis demonstrated that the homologs of these α-gliadin genes were present in tetraploid and hexaploid wheat, which was consistent with T. urartu being the A-genome progenitor species. This study presents a systematic investigation of the gliadin gene families in T. urartu that spans the genome, transcriptome and proteome, and it provides new information to better understand the molecular structure, expression profiles and evolution of the gliadin genes in T. urartu and common wheat.

Quantitative immunohistochemical method for detection of wheat protein in model sausage

Since gluten can induce coeliac symptoms in hypersensitive consumers with coeliac disease, it is necessary to label foodstuffs containing it. In order to label foodstuffs, it is essential to find reliable methods to accurately determine the amount of wheat protein in food. The objective of this study was to compare the quantitative detection of wheat protein in model sausages by ELISA and immunohistochemical methods. Immunohistochemistry was combined with stereology to achieve quantitative results. High correlation between addition of wheat protein and compared methods was confirmed. For ELISA method the determined values were r = 0.98, P < 0.01; for stereologythe determined values were r = 0.94, P < 0.01. Although ELISA is an accredited method, it was not reliable, unlike immunohistochemical methods (stereology SD = 3.1).

Treatment of both native and deamidated gluten peptides with an endo-peptidase from Aspergillus niger prevents stimulation of gut-derived gluten-reactive T cells from either children or adults with celiac disease

Celiac disease (CD) is characterized by an inappropriate immunological reaction against gluten driven by gluten-specific CD4+ T cells. We screened 25 proteases and tested 10 for their potential to degrade gluten in vitro. Five proteases were further tested for their ability to prevent the proliferative response by a gluten-specific CD4+ T cell clone and seven gluten-reactive T cell lines to protease-digested gluten peptides. A proline-specific endo-peptidase from Aspergillus niger (AnP2) was particularly efficient at diminishing proliferation after stimulation with cleaved antigen, and could completely block the response against both native and deamidated gluten peptides. We found that AnP2 was efficient down to a 1:64 protease:substrate ratio (w:w). When AnP2 was tested in assays using seven gluten-reactive T cell lines from individual CD patients (three adults and four children), the response to gluten was diminished in all cases. Our study indicates a therapeutic benefit of AnP2 to CD patients.

Analysis of wheat prolamins, the causative agents of celiac sprue, using reversed phase high performance liquid chromatography (RP-HPLC) and matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS)

Wheat prolamins, commonly known as "gluten", are a complex mixture of 71-78 proteins, which constitute ~80% of the proteins in the wheat grains and supply 50% of the global dietary protein demand. Prolamins are also responsible for numerous gluten-induced disorders and determine the unique visco-elastic properties of the wheat dough. These properties necessitate the reliable determination of the prolamin composition in wheat grains and their derived products. Therefore, this study examined the impact of HPLC conditions, including column type, column temperature, flow rate, and the gradient of polar and non-polar solvents in the mobile phase, to improve the analytical resolution of prolamins. The following conditions were found optimal for analyses: column temperature 60 °C, flow rate 1.0 mL/min and an elution gradient of 20%-60% of 0.1% trifluoroacetic acid + acetonitrile in 60 min. For further improvement of resolution, gliadin and glutenin extracts were analyzed using MALDI-TOF-MS in combination with HPLC fractionation. Two semi-quantitative methods, densitometry of stained polyacrylamide gels and HPLC, were used to determine relative prolamin quantities and the correspondence between the methods was established. The combinatorial gluten analyses approach developed during the present study was used to analyze prolamin profiles of wheat transformants expressing DEMETER silencing artificial microRNA, and the results are discussed.

The molecular diversity of α-gliadin genes in the tribe Triticeae

Many of the unique properties of wheat flour are derived from seed storage proteins such as the α-gliadins. In this study these α-gliadin genes from diploid Triticeae species were systemically characterized, and divided into 3 classes according to the distinct organization of their protein domains. Our analyses indicated that these α-gliadins varied in the number of cysteine residues they contained. Most of the α-gliadin genes were grouped according to their genomic origins within the phylogenetic tree. As expected, sequence alignments suggested that the repetitive domain and the two polyglutamine regions were responsible for length variations of α-gliadins as were the insertion/deletion of structural domains within the three different classes (I, II, and III) of α-gliadins. A screening of celiac disease toxic epitopes indicated that the α-gliadins of the class II, derived from the Ns genome, contain no epitope, and that some other genomes contain much fewer epitopes than the A, S(B) and D genomes of wheat. Our results suggest that the observed genetic differences in α-gliadins of Triticeae might indicate their use as a fertile ground for the breeding of less CD-toxic wheat varieties.

Intentional and inadvertent non-adherence in adult coeliac disease. A cross-sectional survey

Adherence to a gluten-free diet is the mainstay of treatment for coeliac disease. Non-adherence is common as the diet is restrictive and can be difficult to follow. This study aimed to determine the rates of intentional and inadvertent non-adherence in adult coeliac disease and to examine the factors associated with both. A self-completion questionnaire was mailed to adult coeliac patients identified from the computer records of 31 family practices within the North East of England. We received 287 responses after one reminder. Intentional gluten consumption was reported by 115 (40%) of respondents. 155 (54%) had made at least one known mistaken lapse over the same period and 82 (29%) reported neither intentional nor mistaken gluten consumption. Using logistic regression analysis, low self-efficacy, perceptions of tolerance to gluten and intention were found to be independently predictive of intentional gluten consumption. A statistical model predicted 71.8% of cases reporting intentional lapses. Intentional non-adherence to the GFD was found to be common but not as frequent as inadvertent lapses. Distinguishing the factors influencing both intentional and inadvertent non-adherence is useful in understanding dietary self-management in coeliac disease.

Erkrankungen und Therapieformen des unteren Gastrointestinaltrakts

Duodenalatresien sind Hemmungsfehlbildungen und können proximal oder distal der Papilla Vateri entstehen, wobei die präpapillären Obstruktionen selten sind. Grundsätzlich kann zwischen einer Membranatresie und einer Defektatresie unterschieden werden. Die Unterscheidung beruht nicht nur auf embryologischen Gesichtspunkten, sondern hat auch eine klinische Bedeutung: Bei der Membranatresie kann die quergestellte, partiell offene oder geschlossene Membran weit in den distalen Duodenalanteil reichen („Windsackphänomen“), was zu diagnostischen und auch intraoperativen Problemen führen kann. Ein Pancreas anulare findet sich bei etwa 20 % aller Patienten mit Duodenalatresie.

Might gluten traces in wheat substitutes pose a risk in patients with celiac disease? A population-based probabilistic approach to risk estimation

BACKGROUND

In patients with treated celiac disease (CD), the ingestion of gluten traces contained in gluten-free (GF) wheat substitutes (eg, GF bread, flour, and pasta) could cause persisting intestinal mucosal damage.

OBJECTIVE

The objective was to evaluate the proportion of CD patients at risk of mucosal damage due to the consumption of GF products in 4 European countries (Italy, Spain, Germany, and Norway).

DESIGN

A probabilistic modeling approach was used to assess the risk of gluten intake at the population level. The input variables were 1) consumption of GF products, 2) concentration of gluten traces in GF products determined by the sandwich R5 ELISA method, and 3) the gluten threshold for mucosal damage of 10 to 50 mg/d. Different population and product availability scenarios were examined for risk assessment.

RESULTS

The gluten content of 205 commercially available GF products ranged between <5 and 27.8 mg/kg. Overall, 99.5% of the analyzed samples had a gluten concentration <20 mg/kg. Most (94%) had a gluten concentration below the limit of quantification (5 mg/kg). The mean percentage of the CD European population at risk of mucosal damage resulting from consumption of GF products ranged between 0.01 (Germany) and 0.15 (Italy) and remained very low, even in the worst-case scenario (<1%).

CONCLUSIONS

The adoption of a single gluten threshold (20 mg/kg) for gluten contamination is suggested. GF products in Europe constitute a very safe option for patients with CD. The dietary follow-up of CD patients should focus on other potential sources of gluten contamination.

Molecular and immunological characterization of gluten proteins isolated from oat cultivars that differ in toxicity for celiac disease

A strict gluten-free diet (GFD) is the only currently available therapeutic treatment for patients with celiac disease (CD). Traditionally, treatment with a GFD has excluded wheat, barley and rye, while the presence of oats is a subject of debate. The most-recent research indicates that some cultivars of oats can be a safe part of a GFD. In order to elucidate the toxicity of the prolamins from oat varieties with low, medium, and high CD toxicity, the avenin genes of these varieties were cloned and sequenced, and their expression quantified throughout the grain development. At the protein level, we have accomplished an exhaustive characterization and quantification of avenins by RP-HPLC and an analysis of immunogenicity of peptides present in prolamins of different oat cultivars. Avenin sequences were classified into three different groups, which have homology with S-rich prolamins of Triticeae. Avenin proteins presented a lower proline content than that of wheat gliadin; this may contribute to the low toxicity shown by oat avenins. The expression of avenin genes throughout the development stages has shown a pattern similar to that of prolamins of wheat and barley. RP-HPLC chromatograms showed protein peaks in the alcohol-soluble and reduced-soluble fractions. Therefore, oat grains had both monomeric and polymeric avenins, termed in this paper gliadin- and glutenin-like avenins. We found a direct correlation between the immunogenicity of the different oat varieties and the presence of the specific peptides with a higher/lower potential immunotoxicity. The specific peptides from the oat variety with the highest toxicity have shown a higher potential immunotoxicity. These results suggest that there is wide range of variation of potential immunotoxicity of oat cultivars that could be due to differences in the degree of immunogenicity in their sequences.

Detection of gliadin in foods using a quartz crystal microbalance biosensor that incorporates gold nanoparticles

This work develops a label-free gliadin immunosensor that is based on changes in the frequency of a quartz crystal microbalance (QCM) chip. A higher sensitivity was obtained by applying 25 nm gold nanoparticles (AuNPs) to the surface of a bare QCM electrode. Subsequently, chicken anti-gliadin antibodies (IgY) were immobilized directly on the AuNP-modified surface by cross-linking amine groups in IgY with glutaraldehyde. Experimental results revealed that the change in frequency exhibited when 2 ppm gliadin was bound to the AuNP-modified electrode was 35 Hz (48%) greater than that of the bare gold electrode. The linear dynamic range in 60% ethanol was from 1 × 10(1) to 2 × 10(5) ppb gliadin, and the calculated limit of detection (LOD) was 8 ppb. The entire detection process was completed in 40 min and was highly repeatable. Additionally, the AuNP-modified QCM system generated results in the detection of gliadin in 10 commercial food products that were consistent with those obtained using an AOAC-approved gliadin kit. In conclusion, the QCM platform provides a potential alternative means of ensuring that people with wheat allergies and celiac patients have access to gliadin-free food.

Safety for patients with celiac disease of baked goods made of wheat flour hydrolyzed during food processing

BACKGROUND & AIMS

Celiac disease (CD) is characterized by an inflammatory response to wheat gluten, rye, and barley proteins. Fermentation of wheat flour with sourdough lactobacilli and fungal proteases decreases the concentration of gluten. We evaluated the safety of daily administration of baked goods made from this hydrolyzed form of wheat flour to patients with CD.

METHODS

Patients were randomly assigned to consumption of 200 g per day of natural flour baked goods (NFBG) (80,127 ppm gluten; n = 6), extensively hydrolyzed flour baked goods (S1BG) (2480 ppm residual gluten; n = 2), or fully hydrolyzed baked goods (S2BG) (8 ppm residual gluten; n = 5) for 60 days.

RESULTS

Two of the 6 patients who consumed NFBG discontinued the challenge because of symptoms; all had increased levels of anti-tissue transglutaminase (tTG) antibodies and small bowel deterioration. The 2 patients who ate the S1BG goods had no clinical complaints but developed subtotal atrophy. The 5 patients who ate the S2BG had no clinical complaints; their levels of anti-tTG antibodies did not increase, and their Marsh grades of small intestinal mucosa did not change.

CONCLUSIONS

A 60-day diet of baked goods made from hydrolyzed wheat flour, manufactured with sourdough lactobacilli and fungal proteases, was not toxic to patients with CD. A combined analysis of serologic, morphometric, and immunohistochemical parameters is the most accurate method to assess new therapies for this disorder.

Mechanism of degradation of immunogenic gluten epitopes from Triticum turgidum L. var. durum by sourdough lactobacilli and fungal proteases

As shown by R5 antibody-based sandwich and competitive enzyme-linked immunosorbent assay (ELISA), selected sourdough lactobacilli, in combination with fungal proteases, hydrolyzed gluten (72 h at 37 degrees C) of various cultivars of Triticum turgidum L. var. durum to less than 20 ppm. Complementary electrophoretic, chromatography, and mass spectrometry techniques were used to characterize the gluten and epitope hydrolysis. Nine peptidases were partially purified from the pooled cytoplasmic extract of the sourdough lactobacilli and used to hydrolyze the 33-mer epitope, the most immunogenic peptide generated during digestion of Triticum species. At least three peptidases (general aminopeptidase type N [PepN], X-prolyl dipeptidyl aminopeptidase [PepX], and endopeptidase PepO) were necessary to detoxify the 33-mer without generation of related immunogenic epitopes. After 14 h of incubation, the combination of all or at least six different peptidases totally hydrolyzed the 33-mer (200 mM) into free amino acids. The same results were found for other immunogenic epitopes, such as fragments 57-68 of alpha 9-gliadin, 62-75 of A-gliadin, and 134-153 of gamma-gliadin. When peptidases were used for fermentation of durum wheat semolina, they caused the hydrolysis of gluten to ca. 2 ppm. The in vivo digestion was simulated, and proteins/peptides extracted from pepsin-trypsin (PT) digestion of durum wheat semolina fermented with selected sourdough lactobacilli induced the expression of gamma interferon and interleukin 2 at levels comparable to those of the negative control. Durum wheat semolina fermented with sourdough lactobacilli was freeze-dried and used for making Italian-type pasta. The scores for cooking and sensory properties for this pasta were higher that those of conventional gluten-free pasta.

Symposium 1: Joint BAPEN and British Society of Gastroenterology Symposium on ‘Coeliac disease: basics and controversies’ Coeliac disease: optimising the management of patients with persisting symptoms?

The vast majority of patients with coeliac disease will derive benefit from a gluten-free diet. However, some patients will not improve on the gluten-free diet or they will have a relapse of their symptoms. The present review will focus on this group of patients. Definitions for non-responsive coeliac disease and refractory coeliac disease will be provided. The most common reason for recurrent symptoms is continued gluten exposure. Other causes of persisting symptoms are discussed, including alternative causes of villous atrophy or co-existent pathology. Current literature is reviewed, including an initial investigation strategy for patients with persisting symptoms. A pragmatic management plan is described that can be initiated by any clinician. Finally, the current optimal investigational pathway for patients with refractory (or suspected refractory) coeliac disease is discussed and the reported effects of a number of therapeutic options are summarised. The aim of the present article is to provide clinicians with an up-to-date review of the literature in this clinical field and allow them to determine the most appropriate management strategy.

Diagnosis and treatment of celiac disease

The understanding of the pathogenesis of celiac disease has made huge advances in recent years. The disease is caused by an inappropriate immune response to dietary gluten proteins. This immune response is controlled by CD4(+) T cells in the lamina propria that recognize gluten peptides in the context of disease predisposing HLA-DQ2 and HLA-DQ8 molecules.(1, 2) These T cells are specific for proline- and glutamine-rich gluten peptides that are resistant to proteolysis and that have been become deamidated by the enzyme transglutaminase 2 (TG2). Strikingly, celiac disease patients produce antibodies to this same enzyme when exposed to dietary gluten. Here we discuss how the new insight in the pathogenesis has lead to development of new diagnostics and nourished research into novel treatments.

Protein engineering of improved prolyl endopeptidases for celiac sprue therapy

Due to their unique ability to cleave immunotoxic gluten peptides endoproteolytically, prolyl endopeptidases (PEPs) are attractive oral therapeutic candidates for protecting celiac sprue patients from the toxic effects of dietary gluten. Enhancing the activity and stability of PEPs under gastric conditions (low pH, high pepsin concentration) is a challenge for protein engineers. Using a combination of sequence- and structure-based approaches together with machine learning algorithms, we have identified improved variants of the Sphingomonas capsulata PEP, a target of clinical relevance. Through two rounds of iterative mutagenesis and analysis, variants with as much as 20% enhanced specific activity at pH 4.5 and 200-fold greater resistance to pepsin were identified. Our results vividly reinforce the concept that conservative changes in proteins, especially in hydrophobic residues within tightly packed regions, can profoundly influence protein structure and function in ways that are difficult to predict entirely from first principles and must therefore be optimized through iterative design and analytical cycles. Incubation with whole wheat bread under simulated gastric conditions also suggests that some variants have pharmacologically significant improvements in gluten detoxification activity.

Toward the assessment of food toxicity for celiac patients: characterization of monoclonal antibodies to a main immunogenic gluten peptide

BACKGROUND AND AIMS

Celiac disease is a permanent intolerance to gluten prolamins from wheat, barley, rye and, in some patients, oats. Partially digested gluten peptides produced in the digestive tract cause inflammation of the small intestine. High throughput, immune-based assays using monoclonal antibodies specific for these immunotoxic peptides would facilitate their detection in food and enable monitoring of their enzymatic detoxification. Two monoclonal antibodies, G12 and A1, were developed against a highly immunotoxic 33-mer peptide. The potential of each antibody for quantifying food toxicity for celiac patients was studied.

METHODS

Epitope preferences of G12 and A1 antibodies were determined by ELISA with gluten-derived peptide variants of recombinant, synthetic or enzymatic origin.

RESULTS

The recognition sequences of G12 and A1 antibodies were hexameric and heptameric epitopes, respectively. Although G12 affinity for the 33-mer was superior to A1, the sensitivity for gluten detection was higher for A1. This observation correlated to the higher number of A1 epitopes found in prolamins than G12 epitopes. Activation of T cell from gluten digested by glutenases decreased equivalently to the detection of intact peptides by A1 antibody. Peptide recognition of A1 included gliadin peptides involved in the both the adaptive and innate immunological response in celiac disease.

CONCLUSIONS

The sensitivity and epitope preferences of the A1 antibody resulted to be useful to detect gluten relevant peptides to infer the potential toxicity of food for celiac patients as well as to monitor peptide modifications by transglutaminase 2 or glutenases.