Evidence for a primary association of celiac disease to a particular HLA-DQ alpha/beta heterodimer

Clinical spectrum of food allergies: a comprehensive review

Food allergy is defined as an adverse immune response towards food proteins or as a form of a food intolerance associated with a hypersensitive immune response. It should also be reproducible by a double-blind placebo-controlled food challenge. Many reported that food reactions are not allergic but are intolerances. Food allergy often presents to clinicians as a symptom complex. This review focuses on the clinical spectrum and manifestations of various forms of food allergies. According to clinical presentations and allergy testing, there are three types of food allergy: IgE mediated, mixed (IgE/Non-IgE), and non-IgE mediated (cellular, delayed type hypersensitivity). Recent advances in food allergy in early childhood have highlighted increasing recognition of a spectrum of delayed-onset non-IgE-mediated manifestation of food allergy. Common presentations of food allergy in infancy including atopic eczema, infantile colic, and gastroesophageal reflux. These clinical observations are frequently associated with food hypersensitivity and respond to dietary elimination. Non-IgE-mediated food allergy includes a wide range of diseases, from atopic dermatitis to food protein-induced enterocolitis and from eosinophilic esophagitis to celiac disease. The most common food allergies in children include milk, egg, soy, wheat, peanut, treenut, fish, and shellfish. Milk and egg allergies are usually outgrown, but peanut and treenut allergy tends to persist. The prevalence of food allergy in infancy is increasing and may affect up to 15-20 % of infants. The alarming rate of increase calls for a public health approach in the prevention and treatment of food allergy in children.

Cell-surface MHC density profiling reveals instability of autoimmunity-associated HLA

Polymorphisms within HLA gene loci are strongly associated with susceptibility to autoimmune disorders; however, it is not clear how genetic variations in these loci confer a disease risk. Here, we devised a cell-surface MHC expression assay to detect allelic differences in the intrinsic stability of HLA-DQ proteins. We found extreme variation in cell-surface MHC density among HLA-DQ alleles, indicating a dynamic allelic hierarchy in the intrinsic stability of HLA-DQ proteins. Using the case-control data for type 1 diabetes (T1D) for the Swedish and Japanese populations, we determined that T1D risk-associated HLA-DQ haplotypes, which also increase risk for autoimmune endocrinopathies and other autoimmune disorders, encode unstable proteins, whereas the T1D-protective haplotypes encode the most stable HLA-DQ proteins. Among the amino acid variants of HLA-DQ, alterations in 47α, the residue that is located on the outside of the peptide-binding groove and acts as a key stability regulator, showed strong association with T1D. Evolutionary analysis suggested that 47α variants have been the target of positive diversifying selection. Our study demonstrates a steep allelic hierarchy in the intrinsic stability of HLA-DQ that is associated with T1D risk and protection, suggesting that HLA instability mediates the development of autoimmune disorders.

Expression analysis in intestinal mucosa reveals complex relations among genes under the association peaks in celiac disease

Celiac disease is a chronic immune-mediated disorder with an important genetic component. To date, there are 57 independent association signals from 39 non-HLA loci, and a total of 66 candidate genes have been proposed. We aimed to scrutinize the functional implication of 45 of those genes by analyzing their expression in the disease tissue of celiac patients (at diagnosis/treatment) compared with non-celiac controls. Moreover, we investigated the SNP genotype effect in gene expression and performed coexpression analyses. Several genes showed differential expression among disease groups, most of them related to immune response. Multiple trans-eQTLs but only four cis-eQTLs were found, and surprisingly the genotype effect seems to be stimulus dependent as it differs among groups. Coexpression levels vary from higher to lower levels in active patients at diagnosis, treated patients and non-celiac controls respectively. A subset of 18 genes tightly correlated in both groups of patients but not in controls was identified. Interestingly, this subset of genes was influenced by the genotype of three SNPs. One of the SNPs, rs1018326 on chromosome two is on top of a known lincRNA whose function is not yet described, and whose expression seems to be upregulated in active disease when comparing biopsy pairs from the same individuals. Our results strongly suggest that the effects of disease-associated SNPs go far beyond the oversimplistic idea of transcriptional control at a nearby locus. Further investigations are needed to determine how each variant disrupts fine-tuning mechanisms in the genome that eventually lead to disease.

Diagnosing coeliac disease and the potential for serological markers

The diagnosis of coeliac disease has advanced in the past decade owing to increased clinical awareness and improved tests. Coeliac disease is now regarded as a common disease presenting at any age with a broad spectrum of symptoms. Previous guidelines on diagnosis relied on the histological analysis of duodenal biopsy samples. However, contemporary antibody analysis is a diagnostic tool with a comparatively high accuracy that has reduced reliance on performing biopsies. Furthermore, determination of HLA-based genetic susceptibility to coeliac disease has become routine. European and North American guidelines utilize symptoms, coeliac antibodies (primarily tissue transglutaminase 2 IgA and endomysial IgA antibodies), HLA determination and histological analysis of biopsy tissue for diagnosis. Some guidelines conclude that the diagnostic accuracy of tissue transglutaminase 2 IgA antibodies is sufficient to omit duodenal biopsies in selected children with very high antibody levels, in the presence of clear symptom response as well as a positive endomysial antibody test and confirmation of genetic susceptibility. This Review discusses if such a strategy is appropriate for children and adults in all populations. The performance characteristics of antibody tests (particularly of the tissue transglutaminase 2 IgA test) including quality control and characterisation of the population in whom testing is performed are also discussed.

Potential blood-based markers of celiac disease

Background

Blood-based diagnostics has the potential to simplify the process of diagnosing celiac disease (CD). Although high levels of autoantibodies against tissue transglutaminase (anti-TG2) are strongly indicative of active CD, several other scenarios involve a need for additional blood-based CD markers.

Methods

We investigated the levels of messenger RNA (mRNA) in whole blood (n = 49) and protein in plasma (n = 22) from cases with active CD (n = 20), with confirmed CD and normalized histology (n = 15), and without a CD diagnosis (n = 14). Group differences were analyzed using Kruskal-Wallis one-way analysis of variance by ranks. We also investigated correlations between levels of potential markers, histopathology according to the modified Marsh scale, and CD risk gradient based on HLA type, using Spearman rank correlation. The relation between HLA-DQ2 gene dose effect and the expression levels of selected blood-based markers was investigated using the Mann–Whitney U test. Finally, the diagnostic performance of anti-TG2, potential blood-based CD markers, and logistic regression models of combined markers was evaluated using receiver operating characteristic (ROC) curve analysis.

Results

CXCL11 protein levels and TNFRSF9 and TNFSF13B mRNA levels were identified as potential CD markers. These are all affected by or involved in the regulation of the NF-κB complex. CXCL11 protein levels and IL21 and IL15 mRNA levels were correlated with histopathology according to the modified Marsh scale, as were the established CD markers. HLA genotype risk and HLA-DQ2 gene dose effect did not show any significant relations with either the potential CD markers or the established CD markers. ROC curve analysis revealed a slight, non-significant increase in the area under the curve for the combined use of anti-TG2 and different constellations of potential blood-based CD markers compared to anti-TG2 alone.

Conclusions

The CD markers identified in this study further emphasize the significance of components related to NF-κB regulation in relation to CD. However, the relevance of CXCL11, TNFSF13B, TNFRSF9, and other NF-κB interacting proteins recognized by pathway analysis, needs to be further investigated in relation to diagnosis and monitoring of CD.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-230X-14-176) contains supplementary material, which is available to authorized users.

Randomized feeding intervention in infants at high risk for celiac disease

BACKGROUND

A window of opportunity has been suggested for reducing the risk of celiac disease by introducing gluten to infants at 4 to 6 months of age.

METHODS

We performed a multicenter, randomized, double-blind, placebo-controlled dietary-intervention study involving 944 children who were positive for HLA-DQ2 or HLA-DQ8 and had at least one first-degree relative with celiac disease. From 16 to 24 weeks of age, 475 participants received 100 mg of immunologically active gluten daily, and 469 received placebo. Anti-transglutaminase type 2 and antigliadin antibodies were periodically measured. The primary outcome was the frequency of biopsy-confirmed celiac disease at 3 years of age.

RESULTS

Celiac disease was confirmed by means of biopsies in 77 children. To avoid underestimation of the frequency of celiac disease, 3 additional children who received a diagnosis of celiac disease according to the 2012 European Society for Pediatric Gastroenterology, Hepatology, and Nutrition diagnostic criteria (without having undergone biopsies) were included in the analyses (80 children; median age, 2.8 years; 59% were girls). The cumulative incidence of celiac disease among patients 3 years of age was 5.2% (95% confidence interval [CI], 3.6 to 6.8), with similar rates in the gluten group and the placebo group (5.9% [95% CI, 3.7 to 8.1] and 4.5% [95% CI, 2.5 to 6.5], respectively; hazard ratio in the gluten group, 1.23; 95% CI, 0.79 to 1.91). Rates of elevated levels of anti-transglutaminase type 2 and antigliadin antibodies were also similar in the two study groups (7.0% [95% CI, 4.7 to 9.4] in the gluten group and 5.7% [95% CI, 3.5 to 7.9] in the placebo group; hazard ratio, 1.14; 95% CI, 0.76 to 1.73). Breast-feeding, regardless of whether it was exclusive or whether it was ongoing during gluten introduction, did not significantly influence the development of celiac disease or the effect of the intervention.

CONCLUSIONS

As compared with placebo, the introduction of small quantities of gluten at 16 to 24 weeks of age did not reduce the risk of celiac disease by 3 years of age in this group of high-risk children. (Funded by the European Commission and others; PreventCD Current Controlled Trials number, ISRCTN74582487.).

Dyspepsia and celiac disease: Prevalence, diagnostic tools and therapy

The prevalence of dyspepsia is up to 40% in population-based study. Functional dyspepsia is an exclusion diagnosis and it is classified as a chronic abdominal pain-related functional disorder, characterized by the presence of persistent or recurrent pain or discomfort centered in the upper abdomen, neither relief by defecation, nor association with the onset of a change in stool frequency or form. Celiac disease (CD) is a common autoimmune enteropathy, with a prevalence around 1% in the general population. Its diagnosis includes a serological screening and an upper gastrointestinal endoscopy with multiple biopsies. Gluten-free diet is the only effective treatment. CD diagnosis is often delayed in asymptomatic patients or in individuals with less clinical gastrointestinal symptoms. Several studies performed coeliac disease screening in patients with symptoms suggestive of dyspepsia, showing a biopsy-proved prevalence that ranged from 0.5% to 2%. The typical endoscopic markers of villous atrophy are not sufficiently sensitive, so some endoscopic techniques, such as “water immersion” and confocal endomicroscopy were proposed to improve the diagnostic sensitivity and target biopsies. A recent meta-analysis estimated that the prevalence of CD was higher in patients with dyspepsia, but not in a statistically significant way. However this assumption should be confirmed further larger studies.

The neurologic significance of celiac disease biomarkers

OBJECTIVE

To report neurologic phenotypes and their etiologies determined among 68 patients with either (1) celiac disease (CD) or (2) no CD, but gliadin antibody positivity (2002-2012).

METHODS

Neurologic patients included both those with the CD-prerequisite major histocompatibility complex class II human leukocyte antigen (HLA)-DQ2/DQ8 haplotype, and those without. The 3 groups were as follows: group 1 (n = 44), CD or transglutaminase (Tg)-2/deamidated gliadin immunoglobulin (Ig)A/IgG detected; group 2 (n = 15), HLA-DQ2/DQ8 noncarriers, and gliadin IgA/IgG detected; and group 3 (n = 9), HLA-DQ2/DQ8 carriers, and gliadin IgA/IgG detected. Neurologic patients and 21 nonneurologic CD patients were evaluated for neural and Tg6 antibodies.

RESULTS

In group 1, 42 of 44 patients had CD. Neurologic phenotypes (cerebellar ataxia, 13; neuropathy, 11; dementia, 8; myeloneuropathy, 5; other, 7) and causes (autoimmune, 9; deficiencies of vitamin E, folate, or copper, 6; genetic, 6; toxic or metabolic, 4; unknown, 19) were diverse. In groups 2 and 3, 21 of 24 patients had cerebellar ataxia; none had CD. Causes of neurologic disorders in groups 2 and 3 were diverse (autoimmune, 4; degenerative, 4; toxic, 3; nutritional deficiency, 1; other, 2; unknown, 10). One or more neural-reactive autoantibodies were detected in 10 of 68 patients, all with autoimmune neurologic diagnoses (glutamic acid decarboxylase 65 IgG, 4; voltage-gated potassium channel complex IgG, 3; others, 5). Tg6-IgA/IgG was detected in 7 of 68 patients (cerebellar ataxia, 3; myelopathy, 2; ataxia and parkinsonism, 1; neuropathy, 1); the 2 patients with myelopathy had neurologic disorders explained by malabsorption of copper, vitamin E, and folate rather than by neurologic autoimmunity.

CONCLUSIONS

Our data support causes alternative to gluten exposure for neurologic dysfunction among most gliadin antibody-positive patients without CD. Nutritional deficiency and coexisting autoimmunity may cause neurologic dysfunction in CD.

Systematic review: the association between eosinophilic oesophagitis and coeliac disease

BACKGROUND

The relationship between eosinophilic oesophagitis (EoE) and coeliac disease (CD) remains controversial, with studies yielding varied results.

AIM

To systematically review the evidence of a possible association between both diseases.

METHODS

Electronic searches were performed with keywords relating to EoE and CD in the MEDLINE, EMBASE and SCOPUS databases. Summary estimates were calculated. A random-effects model was used depending on heterogeneity (I(2) ). Publication bias was assessed with the aid of funnel plot analysis, along with the Begg-Mazumdar, Harbord and Egger tests.

RESULTS

The search yielded 197 references; 30 were included in the quantitative summary, with most of these presenting methodological inconsistencies. Significant publication bias in favour of short studies reporting positive associations between both diseases was documented. The prevalence of EoE in CD ranged from 0% to 10.7% (I(2)  = 78.9%). Prevalence of CD in EoE varied between 0.16% and 57.1% (I(2)  = 89%). One high-quality, prospective, randomly selected, population-based study documented a 1.1% prevalence of CD, with no patients presenting EoE. Clinical and methodological heterogeneity hindered the performance of quantitative summaries for prevalence data. A gluten-free diet was effective in achieving histological remission of EoE in 32.1% of coeliac patients (95% confidence interval, 14.9-52.2%; I(2)  = 52.2%), which was similar to that expected for wheat elimination in EoE patients.

CONCLUSIONS

While a lack of valid studies prevents us from completely ruling out a true association between EoE and CD, currently available evidence does not support this hypothesis. Indeed, the only epidemiological study with sufficient validity points to the independence of both diseases.

Clinical utility of celiac disease-associated HLA testing

BACKGROUND

Negative predictive value (NPV) of celiac disease (CD)-related human leukocyte antigens (HLA) DQ2 and DQ8 approaches 100 % in individual patients. However, studies evaluating its exclusionary utility in patient groups are lacking.

AIM

We aim to assess the performance of HLA testing when applied to patient groups with varying characteristics and propose evidence-based recommendations for its clinical use.

METHODS

Demographic and clinical information was recorded in patients undergoing HLA testing. Using predetermined criteria, patients were classified as CD, non-CD, or indeterminate. Diagnostic yield of HLA testing was defined as the percentage of patients in whom CD could be excluded based on negative HLA test.

RESULTS

Two hundred and fifty-six patients underwent testing for CD-related HLA DQ2 and DQ8. 102 (100 non-CD, 2 CD) patients tested HLA negative for a 98 % NPV and 39 % diagnostic yield. Diagnostic yield was highest (60 %) in patients with intraepithelial lymphocytosis plus normal IgA tissue transglutaminase antibody (IgA-tTG) and lowest in patients with positive IgA-tTG plus villous atrophy (0 %). CD was diagnosed in two HLA-negative patients, who carried half of DQ2.5 trans genotype.

CONCLUSIONS

Diagnostic yield of CD-related HLA testing varies widely depending on clinical indication. HLA testing is a practical and valuable test for most patients in whom initial evaluation for CD is inconclusive. A negative HLA result usually obviates the need for further celiac testing including endoscopy and gluten challenge. Rarely, in patients reported as HLA negative, half of HLA DQ2.5 (cis or trans) is sufficient for development of CD.

Serum autoantibodies directed against transglutaminase-2 have a low avidity compared with alloantibodies against gliadin in coeliac disease

Coeliac disease is characterized by intolerance to gliadin and related gluten components present in wheat, barley and rye. Coeliac disease patients harbour antibodies directed against alloantigens such as gliadin, but also against the autoantigen transglutaminase-2 (TG2). The type and quality of antibody responses provides insight into the underlying immune activation processes. Therefore, in this study we have analysed the avidity of the antibody response directed against the autoantigen TG2 and compared this with antibody responses against the alloantigens gliadin and Escherichia coli. We observed that the immunoglobulin (Ig)A autoantibody response directed against TG2 is of low avidity compared with the IgA response against the alloantigens gliadin and E. coli in the same patients; the same was true for IgG, both in IgA-deficient and in -sufficient coeliac patients. The observed avidities appear not to be related to disease stage, antibody levels, age or duration of exposure to gluten. In conclusion, in coeliac disease there is a clear difference in avidity of the antibody responses directed against the auto- and alloantigens, indicating different regulation or site of initiation of these responses.

Diversity in the preimmune immunoglobulin repertoire of SHR lines susceptible and resistant to end-organ injury

We used next-generation sequencing to identify IGH genetic variation in two closely related hypertensive rat lines that differ in susceptibility to end-organ disease (SHR-A3 and SHR-B2). The two SHR lines differ extensively at the IGH locus from the rat reference genome sequence (RRGS) and from each other, creating 306 sequence unique IGH genes. Compared to IGH genes mapped in the RRGS, 98 are null gene alleles (31 are null in both SHR lines, 45 are null in SHR-A3 only, and 23 are null in SHR-B2 only). Of the 306 divergent gene sequences, 126 result in amino acid substitution and, among these, SHR-A3 and SHR-B2 differ from one another at the amino acid level in 96 segments. Twelve pseudogenes in the RRGS had changes displacing the stop codon and creating probable functional genes in either or both SHR-A3 and SHR-B2. A further 5 alleles that encoded functional RRGS genes or open reading frames were converted to pseudogenes in either or both SHR-A3 and SHR-B2. These studies reveal that the pre-immune immunoglobulin repertoire is highly divergent among SHR lines differing in end organ injury susceptibility and this may modify immune mechanisms in hypertensive renal injury.

Risk of pediatric celiac disease according to HLA haplotype and country

BACKGROUND

The presence of HLA haplotype DR3-DQ2 or DR4-DQ8 is associated with an increased risk of celiac disease. In addition, nearly all children with celiac disease have serum antibodies against tissue transglutaminase (tTG).

METHODS

We studied 6403 children with HLA haplotype DR3-DQ2 or DR4-DQ8 prospectively from birth in the United States, Finland, Germany, and Sweden. The primary end point was the development of celiac disease autoimmunity, which was defined as the presence of tTG antibodies on two consecutive tests at least 3 months apart. The secondary end point was the development of celiac disease, which was defined for the purpose of this study as either a diagnosis on biopsy or persistently high levels of tTG antibodies.

RESULTS

The median follow-up was 60 months (interquartile range, 46 to 77). Celiac disease autoimmunity developed in 786 children (12%). Of the 350 children who underwent biopsy, 291 had confirmed celiac disease; an additional 21 children who did not undergo biopsy had persistently high levels of tTG antibodies. The risks of celiac disease autoimmunity and celiac disease by the age of 5 years were 11% and 3%, respectively, among children with a single DR3-DQ2 haplotype, and 26% and 11%, respectively, among those with two copies (DR3-DQ2 homozygosity). In the adjusted model, the hazard ratios for celiac disease autoimmunity were 2.09 (95% confidence interval [CI], 1.70 to 2.56) among heterozygotes and 5.70 (95% CI, 4.66 to 6.97) among homozygotes, as compared with children who had the lowest-risk genotypes (DR4-DQ8 heterozygotes or homozygotes). Residence in Sweden was also independently associated with an increased risk of celiac disease autoimmunity (hazard ratio, 1.90; 95% CI, 1.61 to 2.25).

CONCLUSIONS

Children with the HLA haplotype DR3-DQ2, especially homozygotes, were found to be at high risk for celiac disease autoimmunity and celiac disease early in childhood. The higher risk in Sweden than in other countries highlights the importance of studying environmental factors associated with celiac disease. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases and others.).

Risk of congenital malformations among offspring of mothers and fathers with celiac disease: a nationwide cohort study

BACKGROUND & AIMS

Many patients with celiac disease experience malabsorption, weight loss, and anemia; undiagnosed celiac disease during pregnancy has been linked with adverse outcomes. Studies of celiac disease and congenital malformations in offspring have been underpowered. We investigated the risk of congenital malformations among the offspring of parents with celiac disease.

METHODS

We performed a nationwide cohort study of data from linked health care registers in Sweden from 1973 through 2009. We collected histopathology data from 28 pathology departments in Sweden to identify individuals with celiac disease (based on the presence of villous atrophy). We estimated the risks of malformations in the offspring of mothers and fathers with and without celiac disease. Logistic regression was used to estimate adjusted prevalence odds ratios (aPORs) with 95% confidence intervals (CIs).

RESULTS

Among 11,382 offspring of mothers with celiac disease, there were 672 cases (5.9%) of malformation compared with 2098 cases (5.1%) among 40,922 offspring of mothers without celiac disease. Similarly, 352 (5.9%) of 6002 offspring of fathers with celiac disease and 1009 (5.1%) of 19,600 offspring of fathers without celiac disease had a malformation. In adjusted analyses, the offspring of mothers or fathers with celiac disease had a slightly increased risk of having children with malformations (for those with mothers with celiac disease: aPOR, 1.15; 95% CI, 1.05-1.26; for those with fathers with celiac disease: aPOR, 1.14; 95% CI, 1.00-1.29). However, these excess risks decreased or vanished entirely when we restricted our data to births since 2000 (for those with mothers with celiac disease: aPOR, 1.11; and 95% CI, 0.79-1.56; for those with fathers with celiac disease: aPOR, 1.01; 95% CI, 0.81-1.26).

CONCLUSIONS

In a nationwide study, we found an increased risk for malformation among the offspring of mothers or fathers with celiac disease. However, the excess risk is small; the upper limits of the CIs for malformation indicate a 29% maximum relative increase.

Pathophysiology of celiac disease

Celiac disease (CD) is strongly associated with HLA-DQ2 and HLA-DQ8, HLA-class II molecules that present antigen-derived peptides to CD4 T cells. Indeed, proinflammatory CD4 T cells specific for gluten-derived peptides bound to HLA-DQ2 or HLA-DQ8 are present in the lamina propria of patients, and not found in nonceliac controls. While gluten peptides bind poorly to HLA-DQ2/8, modification by tissue tranglutaminase converts the neutral amino acid glutamine into glutamic acid, introducing a negative charge that allows high affinity binding. Thus, the association between CD and HLA-DQ2/8 is well understood. What is less clear is why only a small minority of HLA-DQ2/8 positive individuals develops CD, why disease can develop at any stage in life and present with highly variable symptoms. I discuss this in the framework of the multiple hit model: next to genetic predisposition, multiple other factors-some extrinsic, some intrinsic-can favour or protect from disease development.

HLA-DRB1*07:01 is associated with a higher risk of asparaginase allergies

Asparaginase is a therapeutic enzyme used to treat leukemia and lymphoma, with immune responses resulting in suboptimal drug exposure and a greater risk of relapse. To elucidate whether there is a genetic component to the mechanism of asparaginase-induced immune responses, we imputed human leukocyte antigen (HLA) alleles in patients of European ancestry enrolled on leukemia trials at St. Jude Children's Research Hospital (n = 541) and the Children's Oncology Group (n = 1329). We identified a higher incidence of hypersensitivity and anti-asparaginase antibodies in patients with HLA-DRB1*07:01 alleles (P = 7.5 × 10(-5), odds ratio [OR] = 1.64; P = 1.4 × 10(-5), OR = 2.92, respectively). Structural analysis revealed that high-risk amino acids were located within the binding pocket of the HLA protein, possibly affecting the interaction between asparaginase epitopes and the HLA-DRB1 protein. Using a sequence-based consensus approach, we predicted the binding affinity of HLA-DRB1 alleles for asparaginase epitopes, and patients whose HLA genetics predicted high-affinity binding had more allergy (P = 3.3 × 10(-4), OR = 1.38). Our results suggest a mechanism of allergy whereby HLA-DRB1 alleles that confer high-affinity binding to asparaginase epitopes lead to a higher frequency of reactions. These trials were registered at www.clinicaltrials.gov as NCT00137111, NCT00549848, NCT00005603, and NCT00075725.

Impact on parents of HLA-DQ2/DQ8 genotyping in healthy children from coeliac families

Due to the association of coeliac disease and HLA-specificities DQ2 and DQ8, HLA-typing can be used for risk determination of the disease. This study was designed to evaluate the knowledge of parents from coeliac families regarding HLA-typing and the impact of HLA-typing on the perception of the health of their children. A structured questionnaire was sent to the Dutch, Spanish and German parents participating with their child in the European PreventCD study on disease prevention in high-risk families, addressing parents' understanding of and attitude towards HLA-typing, distress related to HLA-typing and perceived health and health-related quality of life of their children. Sixty-eight percent of parents of 515 children returned the questionnaires, with 85% of children being DQ2/DQ8 positive. The majority of all parents answered the questions on knowledge correctly. Forty-eight percent of parents of DQ2/DQ8-negative children thought their child could develop coeliac disease. More distress was reported by parents of DQ2/DQ8-positive children (P<0.001). All parents showed few regrets and would repeat HLA-typing in future children. Perceived health and health-related quality of life were similar. In conclusion, we can say that misinterpretation of DQ2/DQ8-negative results by parents is frequent. DQ2/DQ8-positive results do not affect perceived health and health-related quality of life of children but may cause temporary negative feelings among parents. Parents of coeliac families seem to support HLA-typing.

Gliadin activates arginase pathway in RAW264.7 cells and in human monocytes

Celiac disease (CD) is an autoimmune enteropathy triggered in susceptible individuals by the ingestion of gliadin-containing grains. Recent studies have demonstrated that macrophages play a key role in the pathogenesis of CD through the release of inflammatory mediators such as cytokines and nitric oxide (NO). Since arginine is the obliged substrate of iNOS (inducible nitric oxide synthase), the enzyme that produces large amount of NO, the aim of this work is to investigate arginine metabolic pathways in RAW264.7 murine macrophages after treatment with PT-gliadin (PTG) in the absence and in the presence of IFNγ. Our results demonstrate that, besides strengthening the IFNγ-dependent activation of iNOS, gliadin is also an inducer of arginase, the enzyme that transforms arginine into ornithine and urea. Gliadin treatment increases, indeed, the expression and the activity of arginase, leading to the production of polyamines through the subsequent induction of ornithine decarboxylase. This effect is strengthened by IFNγ. The activation of these pathways takes advantage of the increased availability of arginine due to a decreased system y(+)l-mediated efflux, likely ascribable to a reduced expression of Slc7a6 transporter. A significant induction of arginase expression is also observed in human monocytes from healthy subject upon treatment with gliadin, thus demonstrating that gluten components trigger changes in arginine metabolism in monocyte/macrophage cells.

[Genetic and epigenetic aspects of celiac disease]

Genetic background of coeliac disease has been subjects to intensive research since decades. However, only results of HLA phenotyping have been taken over to routine clinical practice. Meanwhile, data on the role of epigenetical factors in the manifestation of diseases have been emerging. In coeliac disease, there are several questions both in the fields of genetics and epigenetics yet to be answered. In this review, a cross section of current knowledge on these issues is presented with special interest regarding the future clinical applications.

The tip of the "celiac iceberg" in China: a systematic review and meta-analysis

Objective

Until recently, celiac disease was considered to be rare in China. We aimed to estimate its true status.

Methods

By searching the MEDLINE database and four Chinese full-text databases (CNKI, CBM, VIP and WANFANG) (up to August 2012), as well as two HLA allele frequency net databases and the Chinese Statistics Yearbook databases, we systematically reviewed the literature on definite and suspected cases of celiac disease, the predisposing HLA allele frequencies, and on gluten exposure in China. Meta-analysis was performed by analyzing DQ2, DQ8 and DQB1*0201 gene frequencies and heterogeneity in populations from different geographic regions and ethnicities in China.

Results

At present, the number of reported celiac disease cases is extremely low in China. The frequencies of the HLA-DQ2.5 and HLA-DQ8 haplotypes were 3.4% (95% confidence interval 1.3–5.5%) and 2.1% (0.1–4.1%), respectively. HLA-DQ2 and HLA-DQ8 antigen frequencies were 18.4% (15.0–21.7%) and 8.0% (4.5–11.4%), respectively. The frequency of the DQB1*0201 allele was 10.5% (9.3–11.6%) and it was more common in the northern Chinese than in the southern Chinese populations. The chance of being exposed to gluten is rapidly increasing all over China nowadays.

Conclusion

The data on HLA haplotyping, in conjunction with increasing wheat consumption, strongly suggests that the occurrence of celiac disease is more common in China than currently reported. Coordinated measures by the Chinese government, medical and agricultural research institutions, and food industries, would be justified to create more awareness about celiac disease and to prevent it becoming a medical and societal burden.

Ethnicity differences in genetic susceptibility to ulcerative colitis: a comparison of Indian asians and white northern Europeans

BACKGROUND

Studies in Caucasian populations have identified a number of genetic associations with ulcerative colitis (UC), but reports from other ethnic groups have been limited. Recent studies from India have reported an association with UC and a single polymorphism (SNP) in CARD15/NOD2 (SNP5, rs2066842), which has not been reported in Caucasian UC cohorts. In addition, strong genetic associations with SNPs in the HLA region have been reported in Indian UC populations. However, there have been no reports on the frequency of HLA class II alleles in Indian populations with inflammatory bowel disease to examine whether the associations differ from other ethnic populations.

METHODS

Genotyping was performed for 137 Indian UC patients for HLA class II alleles (HLA-DRB1*1502 & HLA-DRB1*0103), IL23R (rs11209026), and CARD15/NOD2 (rs2066842). The genetic data were compared with 204 healthy Indian controls and 50 white European UC patients.

RESULTS

The HLA-DRB1*0103 allele was absent in all Indian UC patients and controls in contrast to white European UC patients (9/50: 18%). The HLA-DRB1*1502 allele was significantly more frequent in the Indian UC cohort (29.2%) than controls (17.6%) (P = 0.04) and the allele was absent in the white European cohort. There were no significant differences in the frequency of the CARD15/NOD2 (rs2066842) variant or IL23R (rs11209026) between the different ethnic groups.

CONCLUSIONS

The HLA-DRB1*0103 allele is rare or absent in the Indian Asian population but HLA-DRB1*1502 is positively associated with UC. Further genetic studies in this population could provide valuable information and may help distinguish the degree of influence of genetic and environmental pathogenic factors.

Association between copy number variations of HLA-DQA1 and ankylosing spondylitis in the Chinese Han population

Ankylosing spondylitis (AS) is a chronic inflammatory disease with complex genetic traits. Multiple sequence variations have been associated with AS, but explained only a proportion of heritability. The studies herein aimed to explore potential associations between genomic copy number variation (CNV) and AS of Han Chinese. Five AS patients were examined with the high-density comparative genomic hybridization (CGH) microarrays in the first screen test for AS associated CNVs. A total of 533 AS patients and 792 unrelated controls were examined in confirmation studies with the AccuCopy assays. A significant association was observed between the CNV of the HLA-DQA1 and AS. Comparing with controls, AS patients showed an aberrant copy number (CN), and significantly increased number of patients had more than 2 copies of the HLA-DQA1. Therefore, CNV of the HLA-DQA1 may play an important role in susceptibility to AS in Han Chinese population.

Increased risk of IgA nephropathy among individuals with celiac disease

GOAL

To determine the risk of future biopsy-verified IgA nephropathy (IgAN) among individuals with biopsy-verified celiac disease (CD).

BACKGROUND

Individuals with CD suffer increased risk of end-stage renal disease. An association between CD and IgAN has been suggested; however, results have been inconclusive and no previous study has considered the risk of IgAN in biopsy-verified CD.

STUDY

We performed a population-based prospective cohort study. We identified 27,160 individuals with CD (Marsh stage III) and no previous renal disease through small-intestinal biopsy reports obtained between July 1969 and February 2008 in all (n=28) Swedish pathology departments. Individuals with IgAN were identified by biopsy reports acquired at the 4 Swedish pathology departments specialized in renal pathology. Cox regression analysis was used to determine the risk of future IgAN among individuals with CD compared with 133,949 age-matched and sex-matched reference individuals.

RESULTS

Seven (0.026%) individuals with CD and 11 (0.008%) reference individuals developed IgAN. We found an increased risk of biopsy-verified IgAN among individuals with CD [hazard ratio, 3.03; 95% confidence interval, 1.22-7.56]. The risk increase remained statistically significant after adjustment for prior liver disease and country of birth.

CONCLUSIONS

Individuals with CD suffer a 3-fold increased risk of future IgAN. Our findings warrant awareness of renal function in individuals with CD.

A possible mechanism behind autoimmune disorders discovered by genome-wide linkage and association analysis in celiac disease

Celiac disease is a common autoimmune disorder characterized by an intestinal inflammation triggered by gluten, a storage protein found in wheat, rye and barley. Similar to other autoimmune diseases such as type 1 diabetes, psoriasis and rheumatoid arthritis, celiac disease is the result of an immune response to self-antigens leading to tissue destruction and production of autoantibodies. Common diseases like celiac disease have a complex pattern of inheritance with inputs from both environmental as well as additive and non-additive genetic factors. In the past few years, Genome Wide Association Studies (GWAS) have been successful in finding genetic risk variants behind many common diseases and traits. To complement and add to the previous findings, we performed a GWAS including 206 trios from 97 nuclear Swedish and Norwegian families affected with celiac disease. By stratifying for HLA-DQ, we identified a new genome-wide significant risk locus covering the DUSP10 gene. To further investigate the associations from the GWAS we performed pathway analyses and two-locus interaction analyses. These analyses showed an over-representation of genes involved in type 2 diabetes and identified a set of candidate mechanisms and genes of which some were selected for mRNA expression analysis using small intestinal biopsies from 98 patients. Several genes were expressed differently in the small intestinal mucosa from patients with celiac autoimmunity compared to intestinal mucosa from control patients. From top-scoring regions we identified susceptibility genes in several categories: 1) polarity and epithelial cell functionality; 2) intestinal smooth muscle; 3) growth and energy homeostasis, including proline and glutamine metabolism; and finally 4) innate and adaptive immune system. These genes and pathways, including specific functions of DUSP10, together reveal a new potential biological mechanism that could influence the genesis of celiac disease, and possibly also other chronic disorders with an inflammatory component.

Celiac disease and autoimmune-associated conditions

Celiac disease (CD) is frequently accompanied by a variety of extradigestive manifestations, thus making it a systemic disease rather than a disease limited to the gastrointestinal tract. This is primarily explained by the fact that CD belongs to the group of autoimmune diseases. The only one with a known etiology is related to a permanent intolerance to gluten. Remarkable breakthroughs have been achieved in the last decades, due to a greater interest in the diagnosis of atypical and asymptomatic patients, which are more frequent in adults. The known presence of several associated diseases provides guidance in the search of oligosymptomatic cases as well as studies performed in relatives of patients with CD. The causes for the onset and manifestation of associated diseases are diverse; some share a similar genetic base, like type 1 diabetes mellitus (T1D); others share pathogenic mechanisms, and yet, others are of unknown nature. General practitioners and other specialists must remember that CD may debut with extraintestinal manifestations, and associated illnesses may appear both at the time of diagnosis and throughout the evolution of the disease. The implementation of a gluten-free diet (GFD) improves the overall clinical course and influences the evolution of the associated diseases. In some cases, such as iron deficiency anemia, the GFD contributes to its disappearance. In other disorders, like T1D, this allows a better control of the disease. In several other complications and/or associated diseases, an adequate adherence to a GFD may slow down their evolution, especially if implemented during an early stage.

A combined biochemical, biophysical and immunological approach towards the identification of celiac disease-specific wheat antigens

Celiac disease (CD) is an inflammatory affliction of the small bowel caused by an immunological hypersensitivity to ingested wheat antigens affecting almost 1 % of the population. The gliadin fraction of wheat has been shown to contain the pathogenic antigens which react with antibodies and T cells. However, there is only limited knowledge regarding the precise nature of the wheat antigens recognized by IgA antibodies from CD patients and diagnostic tests based on the gliadin fraction have been demonstrated to give frequently false positive results. The aim of this study was the characterization of wheat antigens specifically recognized by IgA antibodies of CD patients. We developed a combined biochemical, biophysical, and immunological approach for the identification of celiac disease-specific wheat antigens. It is based on sub-fractionation of the wheat gliadin fraction using two ion exchange chromatography steps, the localization of CD-specific antigens by immunoblotting with IgA antibodies from CD patients, subsequent digestion followed by electro spray ionization-liquid chromatography/mass spectrometry (LC-ESI-MS/MS) and N-terminal sequencing by Edman degradation. Through the sub-fractionation procedure it was possible to separate CD-specific IgA-reactive wheat antigens from other wheat antigens which were also recognized by IgA antibodies of individuals without CD or by CD patients on gluten-free diet. Analysis by LC-ESI-MS/MS and N-terminal sequencing of the sub-fractions and the proteins specifically recognized by CD patients identified certain γ-gliadins with molecular mass of 37,000 and 45,000 as CD-specific wheat antigens. The CD-specific γ-gliadins with the molecular mass of 37,000 and 45,000 should be useful to study pathomechanisms of the disease and to improve the specificity of diagnostic tests for CD.

The association between celiac disease and eosinophilic esophagitis in children and adults

Background

An association between eosinophilic esophagitis (EoE) and celiac disease (CD) has been suggested in the literature. Our aim was to confirm and quantify the association between these two diseases.

Methods

All patients in a large Canadian city diagnosed with EoE or CD over a five-year period were identified. Standardized incidence ratios (SIRs) with 95% confidence intervals (CIs) were calculated.

Results

Over the five-year study EoE was diagnosed in 421 patients and CD was diagnosed in 763 patients. The incidence of EoE ranged from 2.1 to 10.7 cases per 100,000 population. The incidence of CD ranged from 10.4 to 15.7 cases per 100,000 population. Among the EoE cohort, 83 (20%) cases of EoE and 245 (32%) cases of CD were diagnosed in pediatric patients. The incidence of EoE in the pediatric subpopulation ranged from 3.7 to 6.9 cases per 100,000 population. The incidence of CD in the pediatric subpopulation ranged from 9.5 to 22.7 cases per 100,000 population. The concomitant diagnosis of both EoE and CD was made in three patients, all of whom were pediatric males. The SIR for EoE in the CD cohort was 48.4 (95% CI = 9.73, 141.41) with a SIR for CD within the paediatric EoE cohort of 75.05 (95% CI = 15.08, 219.28).

Conclusions

This study confirms the association between EoE and CD. However, this association may be limited to pediatrics where the risk of each condition is increased 50 to 75-fold in patients diagnosed with the alternative condition. The concomitant diagnosis of these conditions should be considered in pediatric patients with upper gastrointestinal symptoms.

ACG clinical guidelines: diagnosis and management of celiac disease

This guideline presents recommendations for the diagnosis and management of patients with celiac disease. Celiac disease is an immune-based reaction to dietary gluten (storage protein for wheat, barley, and rye) that primarily affects the small intestine in those with a genetic predisposition and resolves with exclusion of gluten from the diet. There has been a substantial increase in the prevalence of celiac disease over the last 50 years and an increase in the rate of diagnosis in the last 10 years. Celiac disease can present with many symptoms, including typical gastrointestinal symptoms (e.g., diarrhea, steatorrhea, weight loss, bloating, flatulence, abdominal pain) and also non-gastrointestinal abnormalities (e.g., abnormal liver function tests, iron deficiency anemia, bone disease, skin disorders, and many other protean manifestations). Indeed, many individuals with celiac disease may have no symptoms at all. Celiac disease is usually detected by serologic testing of celiac-specific antibodies. The diagnosis is confirmed by duodenal mucosal biopsies. Both serology and biopsy should be performed on a gluten-containing diet. The treatment for celiac disease is primarily a gluten-free diet (GFD), which requires significant patient education, motivation, and follow-up. Non-responsive celiac disease occurs frequently, particularly in those diagnosed in adulthood. Persistent or recurring symptoms should lead to a review of the patient's original diagnosis to exclude alternative diagnoses, a review of the GFD to ensure there is no obvious gluten contamination, and serologic testing to confirm adherence with the GFD. In addition, evaluation for disorders associated with celiac disease that could cause persistent symptoms, such as microscopic colitis, pancreatic exocrine dysfunction, and complications of celiac disease, such as enteropathy-associated lymphoma or refractory celiac disease, should be entertained. Newer therapeutic modalities are being studied in clinical trials, but are not yet approved for use in practice. Given the incomplete response of many patients to a GFD-free diet as well as the difficulty of adherence to the GFD over the long term, development of new effective therapies for symptom control and reversal of inflammation and organ damage are needed. The prevalence of celiac disease is increasing worldwide and many patients with celiac disease remain undiagnosed, highlighting the need for improved strategies in the future for the optimal detection of patients.

Human leukocyte antigen DQ2.2 and celiac disease

Patients with celiac disease (CD) lacking both human leukocyte antigen (HLA)-DQ2.5 in cis (DQA1*05:01, DQB1*02:01) or trans (DQA1*05:05, DQB1*02:02) configuration and HLA-DQ8 (DQA1*03:01, DQB1*03:02) are considered to be rare. Therefore, absence of these genotypes is commonly used to exclude the diagnosis of CD. To investigate whether this approach is justified, the HLA-distribution in 155 children with CD was studied. A total of 139 (89.7%) patients carried HLA-DQ2.5. Of the remaining patients, 7 (4.5%) carried HLA-DQ8. Interestingly, the 9 (5.8%) patients lacking HLA-DQ2.5 and HLA-DQ8 carried HLA-DQA1*02:01 and -DQB1*02:02 (HLA-DQ2.2). Therefore, HLA-DQ2.2 should be included as an important HLA-type related to CD.

Molecular diagnosis of celiac disease: are we there yet?

BACKGROUND

Celiac disease (CD) is a complex genetic disorder of the small intestine resulting from aberrant cellular responses to gluten peptides. It may affect as much as 1% of the Western population and the only treatment is a lifelong gluten-free diet. Allelic variants of the HLA-DQ locus, coding for the HLA-DQ2 and HLA-DQ8 molecules, contribute to ∼ 40% of CD etiology, whereas other genes, such as MYO9B, CTLA4, IL2, IL21, PARD3 and MAGI2, have only a modest effect. Most of these genes have shown varied association among different populations and an overlap with other autoimmune or inflammatory disorders, indicating that such disorders may share common pathways.

OBJECTIVES

In this review, a molecular approach into diagnostics of celiac disease is shown.

CONCLUSIONS

Genome-wide association studies will allow more genes to be identified, and knowing how risk variants combine will help to predict better the risk for the individual. HLA typing can already be used to identify high-risk individuals.

Vaccine against autoimmune disease: antigen-specific immunotherapy

Recent interest in testing whether the success of antigen-specific immunotherapy (ASIT) for autoimmune diseases in mice can be translated to humans has highlighted the need for better tools to study and understand human autoimmunity. Clinical development of ASIT for allergy has been instructive, but limited understanding of CD4 T cell epitope/determinant hierarchies hampers the rational design and monitoring of ASIT. Definitive identification of pathogenic T cell epitopes as is now known in celiac disease and recent initiatives to optimize immune monitoring will facilitate rational design, monitoring and mechanistic understanding of ASIT for human autoimmune diseases.

Structural basis for self-recognition by autoimmune T-cell receptors

T-cell receptors (TCRs) recognize peptides presented by major histocompatibility complex molecules (pMHC) to discriminate between foreign and self-antigens. Whereas T-cell recognition of foreign peptides is essential for protection against microbial pathogens, recognition of self-peptides by T cells that have escaped negative selection in the thymus can lead to autoimmune disease. Structural studies of autoimmune TCR-pMHC complexes have provided insights into the mechanisms underlying self-recognition and escape from thymic deletion. Two broad categories of self-reactive TCRs can be clearly distinguished: (i) TCRs with altered binding topologies to self-pMHC and (ii) TCRs that bind self-pMHC in the canonical diagonal orientation, but where there are structural defects or suboptimal anchors in the self-ligand. For both categories, however, the overall stability of the autoimmune TCR-pMHC complex is markedly reduced compared to anti-microbial complexes, allowing the autoreactive T cells to evade negative selection, yet retain the ability to be activated by self-antigens in target organs. Additionally, the structures provide insights into TCR cross-reactivity, which can contribute to autoimmunity by increasing the likelihood of self-pMHC recognition. Efforts are now underway to understand the impact of structural alterations in autoimmune TCR-pMHC complexes on higher order assemblies involved in TCR signaling, as well as on immunological synapse formation.

Structure-based prediction of Major Histocompatibility Complex (MHC) epitopes

Because of the enormous diversity of both MHC proteins and peptide epitopes, computational epitope prediction methods are needed in order to supplement limited experimental data. These prediction methods are useful for guiding experiments and have many potential biomedical applications. Unlike popular sequence-based methods, structure-based epitope prediction methods can predict epitopes for multiple MHC types with highly distinct peptide binding propensities. In this chapter, we describe in detail our previously developed structure-based epitope prediction methods for both class I and class II MHC proteins. We also discuss the relative advantages and disadvantages of sequence-based versus structure-based methods and how to evaluate prediction performance.

Biased T cell receptor usage directed against human leukocyte antigen DQ8-restricted gliadin peptides is associated with celiac disease

Celiac disease is a human leukocyte antigen (HLA)-DQ2- and/or DQ8-associated T cell-mediated disorder that is induced by dietary gluten. Although it is established how gluten peptides bind HLA-DQ8 and HLA-DQ2, it is unclear how such peptide-HLA complexes are engaged by the T cell receptor (TCR), a recognition event that triggers disease pathology. We show that biased TCR usage (TRBV9(∗)01) underpins the recognition of HLA-DQ8-α-I-gliadin. The structure of a prototypical TRBV9(∗)01-TCR-HLA-DQ8-α-I-gliadin complex shows that the TCR docks centrally above HLA-DQ8-α-I-gliadin, in which all complementarity-determining region-β (CDRβ) loops interact with the gliadin peptide. Mutagenesis at the TRBV9(∗)01-TCR-HLA-DQ8-α-I-gliadin interface provides an energetic basis for the Vβ bias. Moreover, CDR3 diversity accounts for TRBV9(∗)01(+) TCRs exhibiting differing reactivities toward the gliadin epitopes at various deamidation states. Accordingly, biased TCR usage is an important factor in the pathogenesis of DQ8-mediated celiac disease.

The irritable bowel syndrome-celiac disease connection

Irritable bowel syndrome (IBS) is a prevalent functional gastrointestinal disorder that has a significant impact on quality of life and health care resources. Celiac disease (CD), a gluten-sensitive enteropathy, can be mistaken for IBS. This article discusses the connection between IBS and CD and the new concept of nonceliac gluten sensitivity (NCGS). NCGS may occur in the presence of a normal or near-normal small bowel biopsy. Some patients with IBS without CD may derive symptomatic benefit from a gluten-free diet. Future research could facilitate a significant impact on the quality of life in this potential subgroup of patients.

Diagnosis of celiac disease

This article reviews issues related to identifying the appropriate patient to test for celiac disease, the performance characteristics of serologic testing, the role of gene testing for human leukocyte antigen DQ2 and DQ8 haplotypes, and issues related to the performance of small intestinal biopsy. The article concludes with a review of special diagnostic considerations in pediatric patients.

Celiac disease: an immunological jigsaw

Celiac disease (CD) is a chronic enteropathy induced by dietary gluten in genetically predisposed people. The keystone of CD pathogenesis is an adaptive immune response orchestrated by the interplay between gluten and MHC class II HLA-DQ2 and DQ8 molecules. Yet, other factors that impair immunoregulatory mechanisms and/or activate the large population of intestinal intraepithelial lymphocytes (IEL) are indispensable for driving tissue damage. Herein, we summarize our current understanding of the mechanisms and consequences of the undesirable immune response initiated by gluten peptides. We show that CD is a model disease to decipher the role of MHC class II molecules in human immunopathology, to analyze the mechanisms that link tolerance to food proteins and autoimmunity, and to investigate how chronic activation of IEL can lead to T cell lymphomagenesis.

Significant differences in coeliac immunotoxicity of barley varieties

SCOPE

The only treatment available for coeliac disease (CD) is a strict diet in which the intake of wheat, barley, rye, or oats is avoided. Barley is a major cereal crop, grown mainly for its use in brewing, and it has high nutritional value. The identification of varieties with a reduced toxicity profile may contribute to improve the diet, the quality of life and health of CD patients.

METHODS AND RESULTS

Searching for harmless barleys, we investigated accessions of malting and wild barley, used for developing new cultivated cereals. The CD toxicity profile of barleys was screened using G12 antibody and cell proliferation and IFN-γ release from peripheral blood mononuclear cells and intestinal biopsies from CD patients. We found a direct correlation between the reactivity with G12 and the immunogenicity of the different barleys.

CONCLUSION

The malting barleys were less immunogenic, with reduced levels of toxic gluten, and were possibly less harmful to CD patients. Our findings could raise the prospect of breeding barley species with low levels of harmful gluten, and the attractive goal of developing nontoxic barley cultivars, always taking into account the Codex standard for foods for special dietary use for persons intolerant to gluten.

Severe spruelike enteropathy associated with olmesartan

OBJECTIVE

To report the response to discontinuation of olmesartan, an angiotensin II receptor antagonist commonly prescribed for treatment of hypertension, in patients with unexplained severe spruelike enteropathy.

PATIENTS AND METHODS

All 22 patients included in this report were seen at Mayo Clinic in Rochester, Minnesota, between August 1, 2008, and August 1, 2011, for evaluation of unexplained chronic diarrhea and enteropathy while taking olmesartan. Celiac disease was ruled out in all cases. To be included in the study, the patients also had to have clinical improvement after suspension of olmesartan.

RESULTS

The 22 patients (13 women) had a median age of 69.5 years (range, 47-81 years). Most patients were taking 40 mg/d of olmesartan (range, 10-40 mg/d). The clinical presentation was of chronic diarrhea and weight loss (median, 18 kg; range, 2.5-57 kg), which required hospitalization in 14 patients (64%). Intestinal biopsies showed both villous atrophy and variable degrees of mucosal inflammation in 15 patients, and marked subepithelial collagen deposition (collagenous sprue) in 7. Tissue transglutaminase antibodies were not detected. A gluten-free diet was not helpful. Collagenous or lymphocytic gastritis was documented in 7 patients, and microscopic colitis was documented in 5 patients. Clinical response, with a mean weight gain of 12.2 kg, was demonstrated in all cases. Histologic recovery or improvement of the duodenum after discontinuation of olmesartan was confirmed in all 18 patients who underwent follow-up biopsies.

CONCLUSION

Olmesartan may be associated with a severe form of spruelike enteropathy. Clinical response and histologic recovery are expected after suspension of the drug.

Refractory celiac disease: from bench to bedside

Refractory celiac disease is defined by the persistence of symptoms of malnutrition and intestinal villous atrophy for more than 6-12 months despite strict gluten-free diet in celiac patients. Diagnosis of this rare condition is made after excluding other causes of chronic small intestinal inflammation and villous atrophy and inadvertent intake of gluten. Over the past 15 years, multidisciplinary approaches have been developed to assess the mechanism of resistance to the diet, and two distinct entities have been delineated. Type II refractory celiac disease (RCD) can be defined as a low-grade intraepithelial lymphoma. RCD II is characterised by a massive accumulation of abnormal IEL that display an aberrant hybrid NK/T cell phenotype, contain clonal T cell rearrangement(s) and can mediate a cytolytic attack of the gut epithelium. This condition has a severe prognosis, largely due to the frequent transformation of RCDII IEL into overt aggressive enteropathy-type-associated T cell lymphoma. In contrast, in type I RCD, intestinal lymphocytes have a normal phenotype, and this generally milder condition remains often difficult to differentiate from uncomplicated CD except for the resistance to gluten-free diet (GFD). Several mechanisms may underlie resistance to gluten. Herein, we review the distinctive characteristics of RCD I and RCD II, the mechanisms underlying the onset of resistance to GFD, the risk of developing high grade lymphoma and possible clues to improve their treatment.

On the perils of poor editing: regulation of peptide loading by HLA-DQ and H2-A molecules associated with celiac disease and type 1 diabetes

This review discusses mechanisms that link allelic variants of major histocompatibility complex (MHC) class II molecules (MHCII) to immune pathology. We focus on HLA (human leukocyte antigen)-DQ (DQ) alleles associated with celiac disease (CD) and type 1 diabetes (T1D) and the role of the murine DQ-like allele, H2-Ag7 (I-Ag7 or Ag7), in murine T1D. MHCII molecules bind peptides, and alleles vary in their peptide-binding specificity. Disease-associated alleles permit binding of disease-inducing peptides, such as gluten-derived, Glu-/Pro-rich gliadin peptides in CD and peptides from islet autoantigens, including insulin, in T1D. In addition, the CD-associated DQ2.5 and DQ8 alleles are unusual in their interactions with factors that regulate their peptide loading, invariant chain (Ii) and HLA-DM (DM). The same alleles, as well as other T1D DQ risk alleles (and Ag7), share nonpolar residues in place of Asp at β57 and prefer peptides that place acidic side chains in a pocket in the MHCII groove (P9). Antigen-presenting cells from T1D-susceptible mice and humans retain CLIP because of poor DM editing, although underlying mechanisms differ between species. We propose that these effects on peptide presentation make key contributions to CD and T1D pathogenesis.