Paul J. Ciclitira

HLA types in celiac disease patients not carrying the DQA1*05-DQB1*02 (DQ2) heterodimer: Results from the European genetics cluster on celiac disease

Genetic susceptibility to celiac disease is strongly associated with HLA-DQA1*05-DQB1*02 (DQ2) and HLA-DQA1*03-DQB1*0302 (DQ8). Study of the HLA associations in patients not carrying these heterodimers has been limited by the rarity of such patients. This European collaboration has provided a unique opportunity to study a large series of such patients. From 1008 European coeliacs, 61 were identified who neither carry the DQ2 nor DQ8 heterodimers. Fifty seven of these encoded half of the DQ2 heterodimer. The remaining 4 patients had a variety of clinical presentations. Three of them carried the DQA1*01-DQB*05 haplotype as did 20/61 of those carrying neither DQ2 nor DQ8. This may implicate a role of the DQA1*01-DQB*05 haplotype. None of these four patients carried the DQB1*06 allele that has previously been reported in this sub-group of patients. Of the 16 DQ2 heterodimer negative patients without DRB1*04 or DRB1*07 haplotypes, it was inferred that none encoded the previously implicated DRB4 gene as none had a DRB1*09 haplotype. These results underline the primary importance of HLA-DQ alleles in susceptibility to celiac disease, and the extreme rarity of celiac patients carrying neither the DQ2 or DQ8 heterodimers nor one half of the DQ2 heterodimer alone.

Diagnosis and management of adult coeliac disease: guidelines from the British Society of Gastroenterology

A multidisciplinary panel of 18 physicians and 3 non-physicians from eight countries (Sweden, UK, Argentina, Australia, Italy, Finland, Norway and the USA) reviewed the literature on diagnosis and management of adult coeliac disease (CD). This paper presents the recommendations of the British Society of Gastroenterology. Areas of controversies were explored through phone meetings and web surveys. Nine working groups examined the following areas of CD diagnosis and management: classification of CD; genetics and immunology; diagnostics; serology and endoscopy; follow-up; gluten-free diet; refractory CD and malignancies; quality of life; novel treatments; patient support; and screening for CD.

Wheat peptide challenge in coeliac disease

The exact nature of the cereal moiety that exacerbates coeliac disease is unknown. In-vitro studies have implicated both the N-terminal and far C-terminal domains of one of the wheat prolamins, A-gliadin. Peptides within these regions may act as epitopes that trigger immune events leading to enteropathy. We synthesized three peptides corresponding to amino-acids 3-21, 31-49, and 202-220 of A-gliadin. Four patients with coeliac disease were challenged by intraduodenal infusion of 1 g of gliadin or 200 mg of the synthetic peptides. Jejunal biopsies were taken before and at hourly intervals for 6 h after the infusion. Morphometric variables were measured and intraepithelial lymphocytes counted. Significant histological changes occurred in the small intestinal mucosa after challenge with a synthetic peptide corresponding to amino acids 31-49 of A-gliadin. The N-terminal peptide, residues 3-21 of A-gliadin, did not cause histological changes in any of the patients. In one of the four patients, minor histological changes following challenge with the peptide corresponding to residues 202-220 of A-gliadin were seen. Our results suggest that the oligopeptide corresponding to aminoacids 31-49 of A-gliadin is toxic in vivo, but there is no evidence of toxicity of the far N-terminal peptide, residues 3-21. The C-terminal peptide 202-220 may contain an epitope to which patients with coeliac disease display variable sensitivity. Since the oligopeptide corresponding to amino-acids 31-49 of A-gliadin is recognised by HLA DQ2-restricted T cells, the observed effects may be due to immune activation within the intestinal mucosa.

Analysis and clinical effects of gluten in coeliac disease.

The prolamin working group coordinates research on laboratory gluten analysis in food and on clinical evaluation of patient sensitivity to prolamins. As an observer organization to the Codex Alimentarius Commission, the group summarizes current data on analysis and effects of gluten in coeliac disease. All types of gliadin, the ethanol-soluble fraction of gluten, contain the coeliac-active factor. However, coeliac toxicity and immunogenicity (humoral and cellular) of various prolamins are not identical in coeliac patients. There are no conclusive data on the threshold of gluten sensitivity of coeliac patients. Information as to the long-term risk to coeliac patients exposed to small doses of gliadin is lacking. Therefore, every effort should be made to keep the diet of coeliac patients as gluten-free as possible. The prolamin group is currently evaluating a new enzyme-linked immunosorbent assay (ELISA) protocol for gluten analysis that could serve as a basis for further Codex regulations. The group recommends adherence to a single Codex limit for gluten-free foods. The current limit of 200 ppm gluten is questionable and requires reconsideration based on new information that will be available soon.

Meta and pooled analysis of European coeliac disease data.

Four full genome scans have been carried out by the partners of the European cluster on coeliac disease as well as follow-up studies of candidate regions. No region outside HLA showed significant linkage to the disease in any single study. We first applied a meta-analysis based on a modification of Genome Screen Meta-Analysis to take into account the different linkage statistics, the arbitrariness of bin cutoff points, as well as the sample size of each study. We then performed a pooled linkage analysis of all families and raw genotypes. Besides the HLA region, already known to harbour a risk factor for coeliac disease, both approaches leave very little doubt on the presence of a genetic risk factor in the 5q31–33 region. This region was suggested by several individual studies, but did not reach statistical values high enough to be conclusive when data sets were analysed separately.

Review article: faecal transplantation therapy for gastrointestinal disease.

Aliment Pharmacol Ther 2011; 34: 409–415

A genome-wide family-based linkage study of coeliac disease.

The susceptibility to develop coeliac disease (CD) has a strong genetic component, which is not entirely explained by HLA associations. Two previous genome wide linkage studies have been performed to identify additional loci outside this region. These studies both used a sib‐pair design and produced conflicting results.

Coeliac disease: in vivo toxicity of the putative immunodominant epitope

Background: Peptides from α-gliadins have been used to characterise the immunodominant coeliac toxic epitope. A peptide corresponding to amino acid residues 57–73 of A-gliadin causes peripheral blood mononuclear cells from coeliac patients to secrete interferon γ (IFN-γ); gluten specific small intestinal T cell clones proliferate in response to peptides corresponding to residues 57–68 and 62–75 of α-gliadins. We wished to investigate whether a peptide corresponding to residues 56–75 of α-gliadins exacerbates coeliac disease in vivo. Methods: Four adults with coeliac disease, all of whom were on a gluten free diet, underwent three challenges. Peptic-tryptic gliadin (PTG 1 g) served as a positive control. The test peptide and a negative control peptide were studied on separate occasions. The peptides were instilled into the duodenum and biopsies were taken before the infusion, and two, four, and six hours after commencing the infusions, using a Quinton hydraulic multiple biopsy capsule. Biopsy specimens were assessed blindly for villus height to crypt depth ratio (VH:CD), enterocyte cell height (ECH), and intraepithelial lymphocyte (IEL) count. We used the Mann-Whitney U test, with 95% confidence intervals, for statistical analysis. Results: VH:CD and ECH fell, and IEL increased significantly 4–6 hours after commencing infusions with both PTG and the test peptide in all subjects. The negative control peptide caused no significant changes to villus morphology, enterocyte height, or IEL count in any patient. Conclusion: We have confirmed that the putative immunodominant epitope, a peptide corresponding to residues 56–75 of α-gliadins, exacerbates coeliac disease in vivo.

TAP1 and TAP2 polymorphism in coeliac disease

Coeliac disease is strongly associated with HLA-DQ2, but it is possible that additional major histocompatibility complex genes also confer disease susceptibility. Encoded close to HLA-DQ are two genes, TAP1 and TAP2, whose products are believed to transport antigenic peptides from the cytoplasm into the endoplasmic reticulum. Comparison of 81 coeliac disease patients with caucasoid controls revealed an increased frequency of the alleles TAP1A and TAP2A in the patient population. However, no significant difference was found when patients were compared with HLA-DR and -DQ matched controls, indicating linkage disequilibrium between TAP1A, TAP2A, and HLA-DQ2. The TAP gene products do not have a major influence on susceptibility or resistance to coeliac disease in a Northern European Caucasoid population.

The toxicity of high molecular weight glutenin subunits of wheat to patients with coeliac disease

Objectives The ability of the gliadin fraction of wheat gluten to exacerbate coeliac disease is well documented. We investigated the possible toxicity of high molecular weight glutenin subunits (HMW-GS) in coeliac disease in vitro using gluten-sensitive T cells, and in vivo with challenge studies in patient volunteers. Methods A mixture of four HMW-GS was chemically separated from wheat flour and checked for purity by HPLC, SDS-PAGE and ELISA. T-cell lines, grown up from small intestinal biopsies from coeliac patients (n=17), were tested for their reactivity to HMW-GS. Adults with coeliac disease and who were on a gluten-free diet (n=3) underwent in-vivo challenges with HMW-GS. Duodenal biopsies, taken prior to the challenge and at intervals up to 6 h afterwards, were assessed for morphology, intra-epithelial lymphocyte count, and interleukin 15 (IL-15) expression, by immunohistochemistry. Results T-cell lines from 11 of 17 patients were stimulated by HMW-GS. There was a significant change in small intestinal morphology 4 h after commencing infusions with HMW-GS in all three subjects. For example villus height to crypt depth ratios were reduced in the three patients from 3.0±0.5 to 1.29±0.2, 2.53±0.7 to 0.81±0.6 and 3.0±0.7 to 1.85±0.3, P<0.0001 in all cases. There was increased expression of IL-15 in the small intestine from 2 h after the HMW-GS challenges. Conclusion Mixed HMW-GS stimulate T-cell lines from some coeliac patients and exacerbate coeliac disease in vivo, inducing expression, within 2 h, of IL-15. This suggests an innate immune response to these proteins.