Characterization of cereal toxicity for celiac disease patients based on protein homology in grains

doi:10.1016/S0016-5085(03)01204-6

Gastroenterology

Volume 125, Issue 4, October 2003, Pages 1105-1113

https://doi.org/10.1016/S0016-5085(03)01204-6 Get rights and content

Abstract

$Background & Aims$ : Celiac disease is caused by T-cell responses to wheat gluten-derived peptides. The presence of such peptides in other widely consumed grains, however, has hardly been studied. $Methods$ : We have performed homology searches to identify regions with sequence similarity to T-cell stimulatory gluten peptides in the available gluten sequences: the hordeins of barley, secalins of rye, and avenins of oats. The identified peptides were tested for T-cell stimulatory properties. $Results$ : With 1 exception, no identical matches with T-cell stimulatory gluten peptides were found in the other grains. However, less stringent searches identified 11 homologous sequences in hordeins, secalins, and avenins located in regions similar to those in the original gluten proteins. Seven of these 11 peptides were recognized by gluten-specific T-cell lines and/or clones from patients with celiac disease. Comparison of T-cell stimulatory sequences with homologous but non-T-cell stimulatory sequences indicated key amino acids that on substitution either completely or partially abrogated the T-cell stimulatory activity of the gluten peptides. Finally, we show that single nucleotide substitutions in gluten genes will suffice to induce these effects. $Conclusions$ : These results show that the disease-inducing properties of barley and rye can in part be explained by T-cell cross-reactivity against gluten-, secalin-, and hordein-derived peptides. Moreover, the results provide a first step toward a rational strategy for gluten detoxification via targeted mutagenesis at the genetic level.

Section snippets

Database searches

Databases of gliadins and glutenins (wheat) and hordeins (barley), secalins (rye), and avenins (oats) were composed by combining the proteins listed in the Swiss Prot, Swiss new, Pir, Sptrembl, Remtrembl, Tremblnew, Refseqprotein, Owl, Kabatp, Pdbseq, and Exprot databanks. The program FASTA was used to align protein sequences of each database. For epitope alignments, the minimal sequences needed for T-cell recognition were used.3, 7 Selected hordein, secalin, and avenin sequences were prepared

Matching of gliadin epitopes in gluten

In patients with celiac disease, T-cell reactivity is found against a large panel of epitopes derived from α/β-gliadin, γ-gliadin, and glutenin proteins.2, 3, 4, 5, 6, 7, 22, 23 To define the immunogenicity of the different gliadin molecules, we have performed database searches with gliadin epitopes to locate the epitopes in these proteins.7 We observed that individual gliadin molecules contain a variable number of toxic sequences. In 4 different α/β-gliadin molecules, for example, a variable

Discussion

The presence of a large number of T-cell stimulatory peptides in gluten has been established.2, 3, 4, 5, 6, 7, 22, 23 This raises the question whether a similar repertoire of T-cell stimulatory peptides exists in barley, rye, and/or oats. In the present study, we have searched for such peptides based on the assumption that gluten-specific T cells might cross-react with homologous peptides in barley, rye, and/or oats. We have therefore compared T-cell stimulatory wheat-derived sequences with

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Celiac disease is a T cell-mediated chronic inflammatory condition often characterized by human leukocyte antigen (HLA)-DQ2.5 molecules presenting gluten epitopes derived from wheat, barley, and rye. Although some T cells exhibit cross-reactivity toward distinct gluten epitopes, the structural basis underpinning such cross-reactivity is unclear. Here, we investigated the T-cell receptor specificity and cross-reactivity of two immunodominant wheat gluten epitopes, DQ2.5-glia-α1a (PFPQPELPY) and DQ2.5-glia-ω1 (PFPQPEQPF). We show by surface plasmon resonance that a T-cell receptor alpha variable (TRAV) 4⁺-T-cell receptor beta variable (TRBV) 29-1⁺ TCR bound to HLA-DQ2.5-glia-α1a and HLA-DQ2.5-glia-ω1 with similar affinity, whereas a TRAV4^- (TRAV9-2⁺) TCR recognized HLA-DQ2.5-glia-ω1 only. We further determined the crystal structures of the TRAV4⁺-TRBV29-1⁺ TCR bound to HLA-DQ2.5-glia-α1a and HLA-DQ2.5-glia-ω1, as well as the structure of an epitope-specific TRAV9-2⁺-TRBV7-3⁺ TCR-HLA-DQ2.5-glia-ω1 complex. We found that position 7 (p7) of the DQ2.5-glia-α1a and DQ2.5-glia-ω1 epitopes made very limited contacts with the TRAV4⁺ TCR, thereby explaining the TCR cross-reactivity across these two epitopes. In contrast, within the TRAV9-2⁺ TCR-HLA-DQ2.5-glia-ω1 ternary complex, the p7-Gln was situated in an electrostatic pocket formed by the hypervariable CDR3β loop of the TCR and Arg70β from HLA-DQ2.5, a polar network which would not be supported by the p7-Leu residue of DQ2.5-glia-α1a. In conclusion, we provide additional insights into the molecular determinants of TCR specificity and cross-reactivity to two closely-related epitopes in celiac disease.
Effect of additional water supply during grain filling on protein composition and epitope characteristics of winter oats
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Citation Excerpt :
RP-HPLC analyses have been carried out with three replicate injections from two replicate extracts. The analytical data derived from the RP-HPLC-based separation provides the basis to predict the individual and cumulative amounts of DQ2.5-ave-1a (PYPEQEEPF), DQ2.5-ave-1b (PYPEQEQPF) (Vader et al., 2003; Arentz-Hansen et al., 2004), DQ2.5-ave-1c (PYPEQEQPI) (Hardy et al., 2015), and DQ2.5-ave-2 (PYPEQQPF) epitopes of oat using the procedure of Gell et al. (2021) based on the detailed proteomic data of Tanner et al. (2019). Briefly, Tanner et al. carried out RP-HPLC analysis from an Australian oat variety (cv.
Pure oats in gluten-free diets (GFD) represent important nutritional benefits for people suffering from celiac disease (CD). However, oat cultivars do not contain the typical CD-related wheat gliadin analog polypeptides. Emerging evidence suggests that oat cultivars containing gluten-like epitopes in avenin sequences may pose potential health risks for celiac patients in rare cases, depending on the individual’s susceptibility. Consequently, it is necessary to screen oats in terms of protein and epitope composition, to be able to select safe varieties for gluten-free applications. The overall aim of our study is to investigate the variation of oat protein composition directly related to health-related and techno-functional properties and to examine how the protein compositional parameters change due to irrigation during the grain-filling period as compared to the natural rain-fed grown, in a large winter oat population of different geographic origin.
Elements of an oat sample population representing 164 winter oat varieties from 8 countries and the protein composition of resulting samples have been characterized. Size distribution of the total protein extracts has been analyzed by SE-HPLC, while the 70% ethanol extracted proteins were analyzed by RP-HPLC. Protein extracts are separated into 3 main groups of fractions on the SE-HPLC column; polymeric, avenin, and non-avenin monomeric protein groups, representing 59.17–80.87%, 12.89–31.03%, and 3.40–9.41% of total protein content, respectively. The ratio of polymeric to monomeric proteins varied between 1.71 and 6.07. 91 RP-HPLC-separated peaks have been differentiated from the ethanol extractable proteins of the entire population.
The various parameters identified a lot of variation, confirming the significance of genotypic variation. In addition, it was also established that the additional water supply during grain filling significantly affected the various quantitative parameters of protein content, but not its qualitative structure. This environmental effect, however, was strongly genotype-dependent. Winter oat genotypes with low levels of epitope content were identified and it was proven that these characteristics were independent of the environmental factor of water availability. These genotypes are appropriate for initiating a specific breeding program to yield oat cultivars suitable for CD patients.
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^☆: Supported by grants from the European Community (BHM4-CT98–3087 and QLK1–2000–00657) and the Stimuleringsfonds Voedingsonderzoek LUMC.

¹: The authors thank Drs. R. R. P. de Vries and R. Offringa for critical reading of the manuscript, A. de Ru for mass spectrometric analysis, and W. Benckhuijsen for peptide synthesis.

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Basic-alimentary tractCharacterization of cereal toxicity for celiac disease patients based on protein homology in grains 1 ☆,

Abstract

Section snippets

Database searches

Matching of gliadin epitopes in gluten

Discussion

Gastroenterology

Gastroenterology

Gastroenterology

Lancet

J Pediatr

Gastroenterology

Specificity of tissue transglutaminase explains cereal toxicity in celiac disease

J Exp Med

Small intestinal T cells of celiac disease patients recognize a natural pepsin fragment of gliadin

Proc Natl Acad Sci U S A

Glutenin is involved in the gluten-driven mucosal T cell response

Eur J Immunol

In vivo antigen challenge in celiac disease identifies a single transglutaminase-modified peptide as the dominant A-gliadin T-cell epitope

Nat Med

The intestinal T cell response to alpha-gliadin in adult celiac disease is focused on a single deamidated glutamine targeted by tissue transglutaminase

J Exp Med

Tissue transglutaminase selectively modifies gliadin peptides that are recognized by gut-derived T cells in celiac disease

Nat Med

Basic-alimentary tract
Characterization of cereal toxicity for celiac disease patients based on protein homology in grains ¹ ☆,