In vitro toxicity of purified gluten peptides tested by organ culture

A catalogue of Triticum monococcum genes encoding toxic and immunogenic peptides for celiac disease patients

The celiac disease (CD) is an inflammatory condition characterized by injury to the lining of the small-intestine on exposure to the gluten of wheat, barley and rye. The involvement of gluten in the CD syndrome has been studied in detail in bread wheat, where a set of “toxic” and “immunogenic” peptides has been defined. For wheat diploid species, information on CD epitopes is poor. In the present paper, we have adopted a genomic approach in order to understand the potential CD danger represented by storage proteins in diploid wheat and sequenced a sufficiently large number of cDNA clones related to storage protein genes of Triticum monococcum. Four bona fide toxic peptides and 13 immunogenic peptides were found. All the classes of storage proteins were shown to contain harmful sequences. The major conclusion is that einkorn has the full potential to induce the CD syndrome, as already evident for polyploid wheats. In addition, a complete overview of the storage protein gene arsenal in T. monococcum is provided, including a full-length HMW x-type sequence and two partial HMW y-type sequences.

Local challenge on oral mucosa with an alpha-gliadin related synthetic peptide in patients with celiac disease

OBJECTIVE

Gluten-derived peptides (e.g., amino-acids 31-49 of alpha-gliadin) have been shown to cause changes typical of celiac disease in the gut. Gluten-derived peptides have mostly been used in in vitro studies. The easiest access to the gastrointestinal system may be the mouth. In the present study we were interested to see whether a synthetic peptide corresponding to amino-acids 31-49 of alpha-gliadin could induce inflammatory changes in the oral mucosa after a local challenge in celiac disease patients.

METHODS

The challenge was made by injecting the peptide solution at a concentration of 10 microg/ml submucosally into the oral mucosa of 10 celiac disease patients after a gluten-free diet (GFD) and 12 healthy control subjects. B and CD45RO+ T cells, mast cells, CD3+, CD4+, CD8+ lymphocytes, and alphabeta and gammadelta T-cell receptor-bearing (TcR alphabeta, TcR gammadelta) lymphocytes were counted and HLA DR expression was determined. The expression of CD25 and Ki-67 antigen was also examined.

RESULTS

The peptide significantly increased the total number of T cells in the lamina propria of the celiac disease patients. The expression of T-cell activation marker CD25 (IL-2 receptor), but not that of cell proliferation marker Ki-67, was also significantly increased in the lamina propria after peptide challenge. Such a reaction was not observed in the controls. The numbers of CD3+ and CD4+ T cells in the lamina propria were also increased in celiac disease patients after the challenge. The count of TcR gammadelta+ cells was very small in the oral mucosa in celiac disease and showed no increase when the oral mucosa was challenged with the peptide. The expression of HLA DR staining was enhanced after the submucosal peptide challenge in celiac disease; however, the difference was not statistically significant.

CONCLUSIONS

The results show that in the celiac disease patients after the peptide challenge the oral mucosal lamina propria responds with a nonproliferative increase of lymphocytes. Thus, submucosal challenge with the peptide 31-49 can be used as an aid in the diagnosis of celiac disease. However, further studies with optimized methodology, including various concentrations of the peptide, adjuvants, other peptides, etc., are warranted, especially because the oral mucosa provides the easiest access to an in vivo peptide challenge in celiac disease.

Human genome search in celiac disease using gliadin cDNA as probe

Celiac disease is a wheat gliadin-promoted disorder that displays a complex genetic susceptibility associated with HLA-DQ2, and one or more unknown factor(s), possibly gliadin-like. The presence of mammalian proteins with partial gliadin similarity was suggested by transglutaminase-independent multi-tissue reactivity of gliadin-immunopurified antibodies from celiac patients. No non-plant sequence, however, was identified in gliadin peptide epitope searches of non-redundant and EST databanks via TBLASTN, BLASTP and FASTA, even at E values as high as 20. Therefore, an alpha-gliadin cDNA screen of human cDNA and genomic libraries was undertaken, an approach in keeping with positive human Northern and Southern analyses with the same probe. Four distinct cDNA clones were obtained, the most stringent of which (3.2 and 5.1 kb) were novel, and featured potential open reading frames with high gliadin domain II and domain IV homologies (BestFit quality scores >/=295 and 322, respectively, versus random value 126-127). Both were also homologous to ESTs. An additional 5' gliadin oligonucleotide screen identified the widely distributed cytoplasmic protein acyl coA hydrolase whose homology was restricted to the oligonucleotide probe (BestFit quality=215 versus 100 for random); and achaete-scute homologous protein, which displays particularly high gliadin domain II homology (BestFit quality 316 versus 111 for random). Genomic screening uncovered 16 positives, one of which was the ALR gene, whose similarity to three of gliadin's five domains (I, II and IV; BestFit quality 322-473 versus 121-154 for random) was remarkable. More extensive was novel genomic clone 2, with fragments hybridizing to cDNA probes approximating gliadin domains I, II+IV, V and the gliadin 5' untranslated region, and mapping by FISH to 19q13.11-13. 12. Two fragments were sequenced; one was exonic, as predicted by four different programs; and test oligonucleotides suggested widespread 4 and/or 2 kb mRNA expression, even at high stringency (t(m)-8.8 deg. C). Taken together, it is apparent that several genes with partial gliadin homology exist in the human genome. Many bear gliadin-like T-cell epitopes, are expressed in intestine and, like transglutaminase, are cytoplasmic. Glutamine to glutamic acid or other mutation within such epitopes followed by injury or infection-related release could explain enhanced disease susceptibility in affected families.

In vitro production of endomysial antibodies in cultured duodenal mucosa from patients with celiac disease

OBJECTIVE

Endomysial antibodies (EMAs) had been found recently after in vitro gluten challenge of duodenal mucosa from treated celiac patients. This was a promising result for diagnosis of potential/latent celiac disease. Therefore, we tested the usefulness of the production of EMAs of in vitro-challenged mucosa for diagnosis of celiac disease and determined the location of EMA production.

METHODS

We investigated EMAs in the serum, in the supernatants of in vitro gliadin-challenged duodenal mucosa specimens in 68 patients, and in homogenized native duodenal and gastric specimens in seven patients. Twenty-one of the 68 patients served as nonceliac controls, 11 as candidates for potential celiac disease, 23 celiac patients were on glutenfree diet, and 13 were newly diagnosed.

RESULTS

EMAs were just found in the supernatants of duodenal biopsies of those celiac patients who had demonstrable EMAs in serum, independent of gliadin challenge. In these patients EMAs were also found in homogenized native duodenal biopsies, but not in gastric biopsies.

CONCLUSIONS

EMAs seem to be produced in the small bowel mucosa of celiac patients, but not in other tissues such as gastric mucosa. The production of EMAs could not be initiated under standard in vitro conditions and therefore, such as in vitro challenge cannot be used for diagnostic purposes.

In vitro hydrolysis of gliadin and casein peptides: secondary defect in coeliac disease shown by organ culture

BACKGROUND

Small-intestinal organ culture was used as an in vitro model of coeliac disease, studying biopsy specimens from patients with coeliac disease, cow's milk allergy, and controls.

METHODS

Organ culture incubations were done using the pure gliadin peptide B3144 (amino acid sequences 3-56 of alpha-type gliadins) and a control peptide from casein (amino acid sequences 152-193 of alpha s1-casein). The importance of using negative controls was stressed by non-specific tissue damage. By reversed-phase high-performance liquid chromatography of organ culture supernatants, 27 specimens were further investigated.

RESULTS

There was good retrieval of peptide calibration peaks after culture. Qualitative and quantitative evaluation of chromatography runs showed degradation of at least 29% of B3144 and 37% of Cas-P. Normal mucosa (controls and coeliac patients on a gluten-free diet) was able to hydrolyse peptide fractions completely, whereas incubation with damaged mucosa (coeliac disease, cow's milk allergy) left initial peptides.

CONCLUSION

It is concluded, using a pure single gliadin peptide, that deficient peptide hydrolysis in coeliac disease was a secondary event.

In vitro toxicity of gluten peptides in coeliac disease assessed by organ culture

BACKGROUND

We have used organ culture to investigate the in vitro toxicity of three oligopeptides corresponding to amino acids 31-49 (peptide A), 202-220 (peptide B), and 3-21 (peptide C) of A-gliadin, Frazer's fraction III (FFIII), and ovalbumin.

METHODS

Eight to 14 jejunal biopsy specimens were obtained from each of 8 treated and 7 untreated coeliac patients and 5 normal controls and cultured for 18 h in organ culture with test peptide (1 mg/ml) or medium alone. Mean enterocyte cell heights (ECH) were compared with paired values for specimens grown in medium alone.

RESULTS

A significant reduction in the mean of the ECH values for each of the patient groups was observed with peptide A and FFIII in both treated (p = 0.01 and 0.02, respectively) and untreated (p = 0.03 and 0.01) coeliac patients when compared with tissue incubated with medium alone. No significant changes in the mean ECH value were noted in any of the patient groups in tissue incubated with peptide B, peptide C, or ovalbumin as compared with those with medium alone.

CONCLUSIONS

These results suggest that peptide A is toxic in vitro to the jejunal mucosa of both treated and untreated coeliac patients, correlating with recent findings that this peptide exacerbates coeliac disease in vivo.