Antibodies in celiac disease: implications beyond diagnostics

Bacteria: Potential Make-or-Break Determinants of Celiac Disease

Celiac disease is an autoimmune disease triggered by dietary gluten in genetically susceptible individuals that primarily affects the small intestinal mucosa. The sole treatment is a gluten-free diet that places a social and economic burden on patients and fails, in some, to lead to symptomatic or mucosal healing. Thus, an alternative treatment has long been sought after. Clinical studies on celiac disease have shown an association between the presence of certain microbes and disease outcomes. However, the mechanisms that underlie the effects of microbes in celiac disease remain unclear. Recent studies have employed disease models that have provided insights into disease mechanisms possibly mediated by bacteria in celiac disease. Here, we have reviewed the bacteria and related mechanisms identified so far that might protect from or incite the development of celiac disease. Evidence indicates bacteria play a role in celiac disease and it is worth continuing to explore this, particularly since few studies, to the best of our knowledge, have focused on establishing a mechanistic link between bacteria and celiac disease. Uncovering host-microbe interactions and their influence on host responses to gluten may enable the discovery of pathogenic targets and development of new therapeutic or preventive approaches.

The war on hTG2: warhead optimization in small molecule human tissue transglutaminase inhibitors

Human tissue transglutaminase (hTG2) is a multifunctional enzyme with protein cross-linking and G-protein activity, both of which have been implicated in the progression of diseases such as fibrosis and cancer stem cell propagation when dysregulated, prompting the development of small molecule targeted covalent inhibitors (TCIs) possessing a crucial electrophilic 'warhead'. In recent years there have been significant advances in the library of warheads available for the design of TCIs; however, the exploration of warhead functionality in hTG2 inhibitors has remained relatively stagnant. Herein, we describe a structure-activity relationship study entailing rational design and synthesis for systematic variation of the warhead on a previously reported small molecule inhibitor scaffold, and rigorous kinetic evaluation of inhibitory efficiency, selectivity, and pharmacokinetic stability. This study reveals a strong influence on the kinetic parameters k inact and K I with even subtle variation in warhead structure, suggesting that the warhead plays a significant role in not only reactivity, but also binding affinity, which consequently extends to isozyme selectivity. Warhead structure also influences in vivo stability, which we model by measuring intrinsic reactivity with glutathione, as well as stability in hepatocytes and in whole blood, giving insight into degradation pathways and relative therapeutic potential of different functional groups. This work provides fundamental structural and reactivity information highlighting the importance of strategic warhead design for the development of potent hTG2 inhibitors.

Autoantibodies - enemies, and/or potential allies?

Autoantibodies are well known as potentially highly harmful antibodies which attack the host via binding to self-antigens, thus causing severe associated diseases and symptoms (e.g. autoimmune diseases). However, detection of autoantibodies to a range of disease-associated antigens has enabled their successful usage as important tools in disease diagnosis, prognosis and treatment. There are several advantages of using such autoantibodies. These include the capacity to measure their presence very early in disease development, their stability, which is often much better than their related antigen, and the capacity to use an array of such autoantibodies for enhanced diagnostics and to better predict prognosis. They may also possess capacity for utilization in therapy, in vivo. In this review both the positive and negative aspects of autoantibodies are critically assessed, including their role in autoimmune diseases, cancers and the global pandemic caused by COVID-19. Important issues related to their detection are also highlighted.

Advancements in Gastrointestinal System Biomarkers

The requirement for diagnostic surgical operations of gastrointestinal system diseases significantly decreases with the help of proper diagnostic tools. These modalities are also beneficial for identifying postoperative complications, allowing us to diagnose them in earlier stages, and increasing the postoperative survival rates. Biomarkers are considered an integral part of diagnostic examinations. Developments of biomarkers used for diagnosing and treating abdominal diseases are essential for improving our capabilities in non-invasive monitoring. In this chapter, we review both the novel and the routine biomarkers in the diagnosis and follow-up of gastrointestinal system diseases.

Mean platelet volume can indicate dietary adherence and disease severity of celiac disease

Objective:

At present, there is no reliable indicator for dietary compliance and disease severity in patients with celiac disease (CD). The aim of this study is to evaluate mean platelet volume (MPV) level as a biomarker for detection of disease activation, dietary adherence, and assessment of disease severity.

Methods:

Eighty-one patients with CD and 50 healthy subjects were enrolled in this study. The diagnosis of CD was established by both positive antibodies against endomysium or gliadin and histopathological criteria (lymphocytic infiltration and total villous atrophy in duodenal biopsies).

Results:

MPV was observed to be significantly higher among CD patients when compared to healthy controls (8.14±0.26 fL vs. 7.82±0.29 fL and p=0.001). Overall dietary adherence rate was 72.8% (58/81 CD patients). After induction of a gluten-free diet, the MPV was significantly lower in the dietary adherent group than non-adherent patients (7.86±0.17 fL vs. 8.07±0.30 fL and p=0.001). The increase of MPV was correlated with Marsh classification (Marsh 3 active CD vs. Marsh 2 active CD vs. Marsh 1 active CD; 8.32±0.27 fL vs. 8.12±0.19 fL vs. 7.98±0.19 fL; p=0.004 and p=0.009).

Conclusion:

Based on these data, we believe that increased MPV can provide additional benefit to screening in patients with CD. It can indicate the activation of the disease and adherence to the diet.

Gluten-free diet exposure prohibits pathobiont expansion and gluten sensitive enteropathy in B cell deficient JH-/- mice

In humans, celiac disease (CeD) is a T-cell-driven gluten-sensitive enteropathy (GSE) localized to the small bowel (duodenum). The presence of antibodies specific for gluten- and self-antigens are commonly used diagnostic biomarkers of CeD and are considered to play a role in GSE pathogenesis. Previously, we have described an apparent T-cell-mediated GSE in CD19-/- mice, which develop weak and abnormal B cell responses. Here, we expand on this observation and use a mouse model of complete B cell deficiency (JH-/- mice), to show that absence of a humoral immune response also promotes development of a GSE. Furthermore, 16S analysis of microbial communities in the small intestine demonstrates that a gluten-free diet suppresses the expansion of anaerobic bacteria in the small intestine and colonization of the small intestine by a specific pathobiont. Finally, we also observe that SI enteropathy in mice fed a gluten-rich diet is positively correlated with the abundance of several microbial peptidase genes, which supports that bacterial metabolism of gluten may be an important driver of GSE in our model. Collectively, results from our experiments indicate that JH-/- mice will be a useful resource to investigators seeking to empirically delineate the contribution of humoral immunity on GSE pathogenesis, and support the hypothesis that humoral immunity promotes tolerance to gluten.

Single-cell approaches to dissect adaptive immune responses involved in autoimmunity: the case of celiac disease

Single-cell analysis is a powerful technology that has found widespread use in recent years. For diseases with involvement of adaptive immunity, single-cell analysis of antigen-specific T cells and B cells is particularly informative. In autoimmune diseases, the adaptive immune system is obviously at play, yet the ability to identify the culprit T and B cells recognizing disease-relevant antigen can be difficult. Celiac disease, a widespread disorder with autoimmune components, is unique in that disease-relevant antigens for both T cells and B cells are well defined. Furthermore, the celiac disease gut lesion is readily accessible allowing for sampling of tissue-resident cells. Thus, disease-relevant T cells and B cells from the gut and blood can be studied at the level of single cells. Here we review single-cell studies providing information on such adaptive immune cells and outline some future perspectives in the area of single-cell analysis in autoimmune diseases.

Citrullination of a phage-displayed human peptidome library reveals the fine specificities of rheumatoid arthritis-associated autoantibodies

Background

Post-translational modifications (PTMs) on proteins can be targeted by antibodies associated with autoimmunity. Despite a growing appreciation for their intrinsic role in disease, there is a lack of highly multiplexed serological assays to characterize the fine specificities of PTM-directed autoantibodies.

Methods

In this study, we used the programmable phage display technology, Phage ImmunoPrecipitation Sequencing (PhIP-Seq), to profile rheumatoid arthritis (RA) associated anti-citrullinated protein antibody (ACPA) reactivities.

Findings

Using both unmodified and peptidylarginine deiminase (PAD)-modified phage display libraries consisting of ~250,000 overlapping 90 amino acid peptide tiles spanning the human proteome, PTM PhIP-Seq robustly identified antibodies to citrulline-dependent epitopes.

Interpretation

PTM PhIP-Seq was used to quantify key differences among RA patients, including PAD isoform specific ACPA profiles, and thus represents a powerful tool for proteome-scale antibody-binding analyses.

Funding

This research is based upon work supported in part by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA). The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of ODNI, IARPA, or the US Government. The US Government is authorized to reproduce and distribute reprints for governmental purposes notwithstanding any copyright annotation therein. This study was made possible by a National Institute of General Medical Sciences (NIGMS) grant R01 GM136724 (HBL). MFK was supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) grant T32AR048522. ED was supported by the Rheumatology Research Foundation.

Small intestinal biopsy findings consistent with celiac disease in patients with idiopathic inflammatory myopathy: Review of existing literature

BACKGROUND

Case reports have described patients with idiopathic inflammatory myopathies (IIM) and a concurrent diagnosis of celiac disease (CeD) for whom the muscle inflammation (myositis) component of IIM improves after the patients start standard treatment with gluten-free diet (GFD). A connection between IIM and CeD is not commonly recognized.

AIM

In this first systematic review of the topic, we aimed to explore all peer-reviewed publications of IIM cases and concomitant small intestinal biopsy findings consistent with CeD, published after 1975.

METHODS

Systematic literature searches were performed in MEDLINE, PubMed, and EMBASE, supplemented by screening of references and non-systematic searches via Google and Google Scholar.

RESULTS

Altogether 30 cases published between 1976 and 2017 were uncovered. Information about gastrointestinal symptoms prior to CeD diagnosis was available for 19 patients, with 6/19 (32%) reporting no GI symptoms. CeD-related serological data were available in 23/30 patients. Endomysial antibodies were present in 10/18 (56%), while only 2/9 (22%) had antibodies against tissue transglutaminase. Serum antibodies to native gliadin were present in 16/18 (89%). Clinical effects of a GFD on the IIM were reported for 24 patients, with signs of improvement in 14/24 (58%), including three patients with otherwise therapy-resistant inclusion body myositis. Longitudinal follow-up data available from the published studies indicated that 7/24 (29%) remained in clinical IIM remission with GFD as the sole therapeutic intervention.

CONCLUSION

In the IIM cases presented here, duodenal biopsy findings consistent with celiac disease was sometimes present without classical CeD symptoms or positive traditional CeD serology, and in the majority of cases, the IIM improved after introduction of a gluten-free diet. While extra vigilance towards CeD in IIM patients seems warranted, there is need for more research to clarify if GFD has effects on organ systems other than the small intestine in patients with IIM and small intestinal biopsy findings consistent with CeD.

Influence of Age and Type 1 Diabetes Mellitus on Serological Test for Celiac Disease in Children

PURPOSE

Serological tests of tissue transglutaminase (TTG) and deamidated gliadin (DGP) antibodies for celiac disease diagnosis show conflicting correlation with histology in young children and in type 1 diabetes mellitus (T1DM). Tests' ability to predict histology and cutoff values based on age and T1DM was evaluated.

METHODS

A retrospective study of children who had celiac serological tests between 6/1/2002 and 12/31/2014 at a pediatric hospital.

RESULTS

TTG IgA displayed similar results in predicting histology between <4.0 and ≥4.0 years age groups with sensitivity 98% and 93%, and specificity 88% and 86%, respectively. In children <4.0 years old, sensitivity for DGP antibodies was 100% and specificity 94%; in ≥4.0 years age groups, sensitivity was 60%, 88% for DGP IgA and IgG and specificity 95%, 96%, respectively. TTG IgA had low specificity in patients with T1DM compared with non-T1DM, 42% vs. 91%. Positive TTG IgA with normal histology was associated with higher T1DM prevalence at 36% compared with negative tests at 4%. Finally, the TTG IgA cutoff value was higher in T1DM at 36 vs. 16.3 units in non-T1DM. DGP IgG cutoff showed similar values between age groups; TTG IgA and DGP IgA cutoffs were lower in <4.0 years at 8.3 and 11.9 units than ≥4.0 years at 23.4 and 19.9, respectively.

CONCLUSION

TTG IgA is sufficient for the <4.0 years age group and DGP antibodies had no advantage over TTG IgA in older children. The cutoff value to determine a positive TTG IgA should be higher for children with T1DM.

Seroprevalence of Antitransglutaminase and Antiendomysium Antibodies in Adult Colombian Blood Bank Donors

Celiac disease (CD) is an autoimmune enteropathy induced by the ingestion of gluten from wheat, barley, and rye in genetically susceptible individuals. The global prevalence of CD is 1.4%. However, most of the prevalence studies have been conducted in Caucasian populations; few studies have been performed in Latin America. The aim of this study is to determine the seroprevalence of auto-antibodies used as markers for CD in a Colombian cohort. In this cross-sectional study, the serum samples from Colombian donors of the National Red Cross Blood Bank were collected between June and September 2017 in Bogotá, Colombia. All sera were tested for IgA antitissue transglutaminase (TTG) by enzyme-linked immunosorbent assay. Seropositive sera were tested for IgA antiendomysium (EMA) using indirect immunofluorescence assay. The ancestral genetic composition was determined in donor samples with antibody assay reactivity. Those with two seroreactive assays were typed for HLA class II DQ2 and DQ8. In total, 228 blood donors participated in the study. Among them, 113 were females (49.56%) with an average age of 31.63 years (SD ± 12.99); males had an average of 34.71 years (SD ± 13.01). Only 3 (1.31%) donors reported chronic diarrhea and nonintentional weight loss; 11 (4.82%) had a family history of CD. For the serological assays, 11 donors (4.82%) were seroreactive to IgA anti-TTG: 3 had high reactivity and 8 had low reactivity. Of those seroreactive to IgA anti-TTG, 3 (1.32%) were also seroreactive to anti-EMA, and they were typed as HLA-DQ8 or HLA-DQ2. The baseline ancestral percentage of the seroreactive donors was higher for European and Native American than for African genes. The seroprevalence for anti-TTG and anti-EMA with the presence of HLA-DQ8 and HLA-DQ2 was 1.32%. Additionally, 4.82% donor participants were reactive only for anti-TTG. Compared with other studies, our findings suggest that Colombia has a high prevalence of CD markers.

The Relevance of Selenium Status in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune and inflammatory disease that can cause joint damage. Among the environmental risk factors, diet plays an important role because it can aggravate or attenuate inflammation. Selenium (Se) is considered an essential trace element since it is a structural component of antioxidant enzymes; however, its concentration can be affected by diet, drugs and genetic polymorphisms. Studies have reported that RA patients have a deficient diet in some food groups that is associated with parameters of disease activity. Furthermore, it has been shown that there is an alteration in serum Se levels in this population. Although some clinical trials have been conducted in the past to analyze the effect of Se supplementation in RA, no significant results were obtained. Contrastingly, experimental studies that have evaluated the effect of novel Se nanoparticles in RA-induced models have shown promising results on the restoration of antioxidant enzyme levels. In particular, glutathione peroxidase (GPx) is an important selenoprotein that could have a modulating effect on inflammation in RA. Considering that RA patients present an inflammatory and oxidative state, the aim of this review is to give an overview of the current knowledge about the relevance of Se status in RA.

Mechanism and biomarkers in aortitis--a review

Aortitis can be the manifestation of an underlying infectious or noninfectious disease process. An autoimmune cause is suggested in a large proportion of noninfectious causes. Similar to other autoimmune diseases, the pathophysiology of aortitis has been investigated in detail, but the etiology remains unknown. Most cases of aortitis often go undetected for a long time and are often identified at late stages of the disease. Recent advances in imaging techniques have significantly improved the diagnosis of aortitis. However, significant challenges associated with the imaging techniques limit their use. Several routine inflammation-based markers, such as erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and inflammatory cytokines, are nonspecific and, therefore, have limited use in the diagnosis of aortitis. The search for more specific serum biomarkers, which can facilitate detection and progression is under progress. Several autoantibodies have been identified, but assigning their role in the pathogenesis as well as their specificity remains a challenge. The current review addresses some of these issues in detail. KEY MESSAGES: • Noninfectious aortitis is an autoimmune disease. • Several biomarkers, including cytokines and autoantibodies, are increased in aortitis. • Imaging techniques, commonly used to detect aortitis, are associated with the high cost and technical challenges. • There is a need to develop low-cost biomarker-based detection tools. • The knowledge of biomarkers in aortitis detection is discussed.

Diagnostic accuracy of a fully automated multiplex celiac disease antibody panel for serum and plasma

Background

An automated multiplex platform using capillary blood can promote greater throughput and more comprehensive studies in celiac disease (CD). Diagnostic accuracy should be improved using likelihood ratios for the post-test probability of ruling-in disease.

Methods

The Ig_plex™ Celiac Disease Panel on the sqidlite™ automated platform measured IgA and IgG antibodies to tTG and DGP in n = 224 CD serum or plasma samples. Diagnostic accuracy metrics were applied to the combined multiplex test results for several CD populations and compared to conventional single antibody ELISA tests.

Results

With multiple positive antibody results, the post-test probability for ruling-in untreated and treated CD increased to over 90%. The number of samples positive for more than one antibody also increased in untreated CD to ≥90%. Measurement of all four CD antibodies generate cut-off dependent accuracy profiles that can monitor response to treatment with the gluten-free diet (GFD). Higher positive tTG and DGP antibodies are seen more frequently in confirmed CD without (81%–94%) than with GFD treatment (44%–64%). In CD lacking biopsy confirmation, overall agreement of plasma to serum was ≥98% for all antibodies, and 100% for venous to capillary plasma.

Conclusions

The Ig_plex Celiac Disease Panel increases the likelihood of confirming CD based on the post-test probability of disease results for multi-reactive markers. Specific positivity profiles and cut-off intervals can be used to monitor GFD treatment and likely disease progression. Using serum, venous and capillary plasma yield comparable and accurate results.

Celiac-Related Autoantibodies and IL-17A in Bulgarian Patients with Dermatitis Herpetiformis: A Cross-Sectional Study

Background and objectives: Dermatitis herpetiformis (DH) is a blistering dermatosis, which shares common immunologic features with celiac disease (CD). The aim of the present study was to explore the performance of a panel of CD-related antibodies and IL-17A in Bulgarian patients with DH. Materials and Methods: Serum samples from 26 DH patients at mean age 53 ± 15 years and 20 healthy controls were assessed for anti-tissue transglutaminase (anti-tTG), anti-deamidated gliadin peptides (anti-DGP), anti-actin antibodies (AAA), and IL-17A by enzyme linked immuno-sorbent assay (ELISA), as well as anti-tTG, anti-gliadin (AGA), and anti-Saccharomyces cerevisiae antibodies (ASCA) using immunoblot. Results: The average serum levels of anti-tTG, anti-DGP, AGA, AAA, and the cytokine IL-17A were at significantly higher levels in patients with DH compared to the average levels in healthy persons which stayed below the cut-off value (p < 0.05). Anti-DGP and anti-tTG antibodies showed the highest diagnostic sensitivity and specificity, as well as acceptable positive and negative predictive value. None of the healthy individuals was found positive for the tested antibodies, as well as for ASCA within the DH group. All tests showed good to excellent correlations (r = 0.5 ÷ 0.9, p < 0.01). Conclusions: Although the diagnosis of DH relies on skin biopsy for histology and DIF, serologic testing of a panel of celiac-related antibodies could be employed with advantages in the diagnosing process of DH patients. Furthermore, DH patients who are positive for the investigated serologic parameters could have routine monitoring for gastrointestinal complications typical for the gluten-sensitive enteropathy.

Screening for autoimmune thyroiditis and celiac disease in minority children with type 1 diabetes

BACKGROUND

Hashimoto's thyroiditis (HT) and celiac disease (CD) are commonly associated with type 1 diabetes (T1DM). There is no consensus on screening, however, the American Diabetes Association (ADA) and the International Society for Pediatric and Adolescent Diabetes (ISPAD) recommend testing for thyroid function (TFT), thyroid antibodies and anti-tissue transglutaminase antibodies (TTG) IgA soon after diagnosis. TFT should be repeated every 1-2 years while TTG IgA should be tested for within 2 and 5 years. We hypothesize that the rate of HT and CD in our T1DM children is lower, so screening may need to be revised to reflect their underlying risk.

METHODS

An Institutional Review Board (IRB)-approved retrospective chart review was conducted on children with T1DM in the past 10 years. Age, sex, race, A1C, TFT, thyroid and celiac antibodies were obtained. t-Tests, the Wilcoxon-Mann-Whitney test and stepwise regression were performed.

RESULTS

Of 222 children with T1DM, with a mean age of 15.8±5.53 years, followed for 6.1±4.0 years, 53% female, mean A1C 11.1±1.9% and 87% African American (AA). Three had Graves' disease (1.3%), three had HT (1.3%) and 97% were euthyroid. TFT were assessed on average every 1.3 years and thyroid antibodies every 2.5 years. Positive thyroid antibody was found in 11%, negative in 57% and unknown in 32%. The positive antibody group had higher mean A1C and TSH. No biopsy confirmed cases of CD (0%) were found when screened every 2.3 years.

CONCLUSIONS

The number of individuals who screened positive for hypothyroid HT and CD was lower than expected in our population. Further studies are needed to assess the optimal screening frequency for HT and CD in minority children with T1DM.

Autoantibodies in the Extraintestinal Manifestations of Celiac Disease

Increased antibody reactivity towards self-antigens is often indicative of a disruption of homeostatic immune pathways in the body. In celiac disease, an autoimmune enteropathy triggered by the ingestion of gluten from wheat and related cereals in genetically predisposed individuals, autoantibody reactivity to transglutaminase 2 is reflective of the pathogenic role of the enzyme in driving the associated inflammatory immune response. Autoantibody reactivity to transglutaminase 2 closely corresponds with the gluten intake and clinical presentation in affected patients, serving as a highly useful biomarker in the diagnosis of celiac disease. In addition to gastrointestinal symptoms, celiac disease is associated with a number of extraintestinal manifestations, including those affecting skin, bones, and the nervous system. Investigations of these manifestations in celiac disease have identified a number of associated immune abnormalities, including B cell reactivity towards various autoantigens, such as transglutaminase 3, transglutaminase 6, synapsin I, gangliosides, and collagen. Clinical relevance, pathogenic potential, mechanism of development, and diagnostic and prognostic value of the various identified autoantibody reactivities continue to be subjects of investigation and will be reviewed here.

Design of a glutamine substrate tag enabling protein labelling mediated by Bacillus subtilis transglutaminase

Transglutaminases (TGases) are enzymes that catalyse protein cross-linking through a transamidation reaction between the side chain of a glutamine residue on one protein and the side chain of a lysine residue on another. Generally, TGases show low substrate specificity with respect to their amine substrate, such that a wide variety of primary amines can participate in the modification of specific glutamine residue. Although a number of different TGases have been used to mediate these bioconjugation reactions, the TGase from Bacillus subtilis (bTG) may be particularly suited to this application. It is smaller than most TGases, can be expressed in a soluble active form, and lacks the calcium dependence of its mammalian counterparts. However, little is known regarding this enzyme and its glutamine substrate specificity, limiting the scope of its application. In this work, we designed a FRET-based ligation assay to monitor the bTG-mediated conjugation of the fluorescent proteins Clover and mRuby2. This assay allowed us to screen a library of random heptapeptide glutamine sequences for their reactivity with recombinant bTG in bacterial cells, using fluorescence assisted cell sorting. From this library, several reactive sequences were identified and kinetically characterized, with the most reactive sequence (YAHQAHY) having a kcat/KM value of 19 ± 3 μM-1 min-1. This sequence was then genetically appended onto a test protein as a reactive 'Q-tag' and fluorescently labelled with dansyl-cadaverine, in the first demonstration of protein labelling mediated by bTG.

Allelic frequencies of the hs1.2 enhancer within the immunoglobulin heavy chain region in Dayton, Ohio patients screened for celiac disease with duodenal biopsy

BACKGROUND

Genetic and environmental factors contribute to the development of celiac disease (CD), but specific genetic predisposing factors remain poorly understood. One candidate is allele 2 of the hs1.2 enhancer within the immunoglobulin heavy chain region. In humans, there are four possible alleles and a previous study of an Italian cohort demonstrated a significantly increased frequency of allele 2 in patients with CD.

AIMS

The purpose of the current study was to determine if a similar association between allele 2 and CD exists in an American population from Dayton, OH.

METHODS

Subjects were screened for CD via esophagogastroduodenoscopy with duodenal biopsy. All biopsies were microscopically scored using a modified Marsh-Oberhuber classification. DNA was isolated from patients' buccal cells for hs1.2 genotype analysis using PCR.

RESULTS

Unlike the Italian cohort, allele 2 frequency was not significantly different in patients with histopathologic evidence of CD compared to patients without such evidence. However, our patient population as a whole demonstrated a significantly increased allele 2 frequency when compared to that previously reported within diverse ethnic populations.

CONCLUSIONS

Since our comparative control patients do not necessarily reflect a healthy control population, an overall increase in allele 2 may reflect an association between allele 2 of the hs1.2 enhancer and a spectrum of gastrointestinal disorders.

Development of autoantibodies precedes clinical manifestations of autoimmune diseases: A comprehensive review

The etiology of autoimmune diseases is due to a combination of genetic predisposition and environmental factors that alter the expression of immune regulatory genes through various mechanisms including epigenetics. Both humoral and cellular elements of the adaptive immune system play a role in the pathogenesis of autoimmune diseases and the presence of autoantibodies have been detected in most but not all autoimmune diseases before the appearance of clinical symptoms. In some cases, the presence or levels of these autoantibodies portends not only the risk of developing a corresponding autoimmune disease, but occasionally the severity as well. This observation is intriguing because it suggests that we can, to some degree, predict who may or may not develop autoimmune diseases. However, the role of autoantibodies in the pathogenesis of autoimmune diseases, whether they actually affect disease progression or are merely an epiphenomenon is still not completely clear in many autoimmune diseases. Because of these gaps in our knowledge, the ability to accurately predict a future autoimmune disease can only be considered a relative risk factor. Importantly, it raises the critical question of defining other events that may drive a patient from a preclinical to a clinical phase of disease.

Serological screening for Celiac Disease in 382 pre-schoolers with Autism Spectrum Disorder

Background

Recent investigations suggest a possible common genetic background between Autism Spectrum Disorders (ASD) and Celiac Disease (CD). However, studies regarding this association are scarce and often limited by the small sample sizes and/or large heterogeneity among ASD groups in terms of demographic and clinical features. The present study aims to investigate the overall CD prevalence (biopsy proven-CD patients plus screening detected tTG and EMA positive cases) in a large population of pre-schoolers with ASD referred to a tertiary care University Hospital.

Methods

We retrospectively collected data about 382 children (mean age: 46.97 ± 13.55 months; age-range: 18-72 months) consecutively diagnosed as ASD (according to the Diagnostic and Statistical Manual of Mental Disorders 4th edition criteria) over the period 2010–2013, and who performed a serological CD screening.

Results

The overall CD prevalence was 2.62%, which is statistically significant higher to that reported in the Italian paediatric population (p = 0.0246). Half of these children had no symptoms or risk factors related to CD when they performed the serological screening.

Conclusions

If replicated, these data suggest the importance of regular screening for CD in young patients with ASD, and are of relevance for clinical and public health.

The industrial food additive, microbial transglutaminase, mimics tissue transglutaminase and is immunogenic in celiac disease patients

Microbial transglutaminase (mTg) is capable of cross-linking numerous molecules. It is a family member of human tissue transglutaminase (tTg), and is involved in CD. Despite declarations of the safety of mTg for industrial use, direct evidence for immunogenicity of the enzyme is lacking. The serological activity of mTg, tTg, gliadin complexed mTg (mTg neo-epitope) and gliadin complexed tTg (tTg neo-epitope) were studied in 95 pediatric celiac patients (CD), 99 normal children (NC), 79 normal adults (NA) and 45 children with nonspecific abdominal pain (AP). Sera were tested by ELISAs, detecting IgA, IgG or both IgA and IgG (check): AESKULISA® tTg (tTg), AESKULISA® tTg New Generation (tTg neo-epitope (tTg-neo)), microbial transglutaminase (mTg) and mTg neo-epitope (mTg-neo). Marsh criteria were used for the degree of intestinal injury. Parallel, mTg and tTg neo-epitopes were purified by asymmetric field flow fractionation, confirmed by multi-light-scattering and SDS-PAGE, and analyzed in adult CD and control groups by competition ELISAs. No sequence homology but active site similarity were detected on alignment of the 2 Tgs. Comparing pediatric CD patients with the 2 normal groups: mTg-neo IgA, IgG and IgA+IgG antibody activities exceed the comparable mTg ones (p<0.0001). All mTg-neo and tTg-neo levels were higher (p<0.001). tTg IgA and IgG+IgA were higher than mTg IgA and IgA+IgG (p<0.0001). The levels of tTg-neo IgA/IgG were higher than tTg IgA/IgG (p<0.0001). The sequential antibody activities best reflecting the increased intestinal damage were tTg-neo check>tTg-neo IgA≥mTg-neo IgG>tTg-neo IgG>mTg-neo check>mTg-neo IgA. Taken together, tTg-neo check, tTg-neo IgA and mTg-neo IgG correlated best with intestinal pathology (r²=0.6454, r²=0.6165, r²=0.5633; p<0.0001, p<0.0001, p<0.0001, respectively). Purified mTg-neo IgG and IgA showed an increased immunoreactivity compared to single mTg and gliadin (p<0.001) but similar immunoreactivity to the tTg-neo IgG and IgA ELISA. Using competition ELISA, the mTg neo-epitopes and tTg neo-epitopes have identical outcomes in CD sera both showing a decrease in optical density of 55±6% (p<0.0002). mTg is immunogenic in children with CD and, by complexing to gliadin, its immunogenicity is enhanced. Anti-mTg-neo-epitope IgG antibodies correlate with intestinal damage to a comparable degree as anti-tTg-neo IgA. mTg and tTg display a comparable immunopotent epitope. mTg-neo IgG is a new marker for CD. Further studies are needed to explore the pathogenic potential of anti-mTg antibodies in CD.

Celiac anti-type 2 transglutaminase antibodies induce differential effects in fibroblasts from celiac disease patients and from healthy subjects

Type 2 transglutaminase (TG2) has an important pathogenic role in celiac disease (CD), an inflammatory intestinal disease that is caused by the ingestion of gluten-containing cereals. Indeed, TG2 deamidates specific gliadin peptides, thus enhancing their immunogenicity. Moreover, the transamidating activity seems to provoke an autoimmune response, where TG2 is the main autoantigen. Many studies have highlighted a possible pathogenetic role of anti-TG2 antibodies, because they modulate TG2 enzymatic activity and they can interact with cell-surface TG2, triggering a wide range of intracellular responses. Autoantibodies also alter the uptake of the alpha-gliadin peptide 31-43 (p31-43), responsible of the innate immune response in CD, thus partially protecting cells from p31-43 damaging effects in an intestinal cell line. Here, we investigated whether anti-TG2 antibodies protect cells from p31-43-induced damage in a CD model consisting of primary dermal fibroblasts. We found that the antibodies specifically reduced the uptake of p31-43 by fibroblasts derived from healthy subjects but not in those derived from CD patients. Analyses of TG2 expression and enzymatic activity did not reveal any significant difference between fibroblasts from healthy and celiac subjects, suggesting that other features related to TG2 may be responsible of such different behaviors, e.g., trafficking or subcellular distribution. Our findings are in line with the concept that a "celiac cellular phenotype" exists and that TG2 may contribute to this phenotype. Moreover, they suggest that the autoimmune response to TG2, which alone may damage the celiac mucosa, also fails in its protective role in celiac cells.

Transglutaminase 2-specific coeliac disease autoantibodies induce morphological changes and signs of inflammation in the small-bowel mucosa of mice

Coeliac disease is hallmarked by an abnormal immune reaction against ingested wheat-, rye- and barley-derived gluten and the presence of transglutaminase 2 (TG2)-targeted autoantibodies. The small-bowel mucosal damage characteristic of the disorder develops gradually from normal villus morphology to inflammation and finally to villus atrophy with crypt hyperplasia. Patients with early-stage coeliac disease have TG2-autoantibodies present in serum and small-intestinal mucosa and they may already suffer from abdominal symptoms before the development of villus atrophy. Previously, we have shown that intraperitoneal injections of coeliac patient-derived sera or purified immunoglobulin fraction into mice induce a condition mimicking early-stage coeliac disease. In the current study, we sought to establish whether recombinantly produced patient-derived TG2-targeted autoantibodies are by themselves sufficient for the development of such an experimentally induced condition in immune-compromised mice. Interestingly, mice injected with coeliac patient TG2-antibodies had altered small-intestinal mucosal morphology, increased lamina propria cellular infiltration and disease-specific autoantibodies deposited in the small bowel, but did not evince clinical features of the disease. Thus, coeliac patient-derived TG2-specific autoantibodies seem to be sufficient for the induction of subtle small-bowel mucosal alterations in mice, but the development of clinical features probably requires additional factors such as other antibody populations relevant in coeliac disease.

Extension of the celiac intestinal antibody (CIA) pattern through eight antibody assessments in fecal supernatants from patients with celiac disease

BACKGROUND

Detection of anti-transglutaminase, anti-endomysium and anti-gliadin antibodies is commonly used to screen celiac disease patients. Besides that in serum, these antibodies are detectable in culture supernatants of oral, duodenal and colonic biopsy samples, saliva, gut lavage fluid samples, and fecal supernatants. Our aim was to extend the intestinal antibody pattern in fecal supernatants from patients with celiac disease.

METHODS

The fecal supernatants obtained from 25 celiac disease patients and 12 healthy volunteers were used to determine IgA and IgG1 anti-endomysium by immunofluorescence analysis, IgA and IgG anti-transglutaminase, IgA and IgG anti-deamidated gliadin peptides, IgA/IgG anti-transglutaminase/deamidated gliadin peptides and IgA anti-actin by enzyme-linked immunosorbent assay.

RESULTS

IgA anti-endomysium were found in 11 of 25 (44.0%) celiac disease patients and in none of healthy volunteers (p=0.0066). The levels of IgA anti-transglutaminase, IgA anti-deamidated gliadin peptides, IgA/IgG anti-transglutaminase/deamidated gliadin peptides and IgA anti-actin determined in celiac disease patients were significantly higher (p=0.0005, p=0.0018, p=0.0061 and p=0.0477, respectively) than those measured in healthy volunteers. The ROC curve analysis showed a diagnostic significance in IgA anti-transglutaminase (AUC=0.862, p<0.0001), IgA anti-deamidated gliadin peptides (AUC=0.822, p<0.0001) and IgA/IgG anti-transglutaminase/deamidated gliadin peptides (AUC=0.783, p=0.0003) fecal tests.

CONCLUSIONS

Our data extend the intestinal antibody pattern detectable in fecal supernatants, thus increasing the knowledge in the humoral immunity of celiac disease. Further studies are needed to better evaluate the role of fecal antibody tests in identifying celiac disease patients.

Thyroid-associated orbitopathy is linked to gastrointestinal autoimmunity

Common autoimmune disorders tend to co-exist in the same subjects and cluster in families. The objective of this study was to determine the prevalence of autoimmune co-morbidity in patients with autoimmune thyroid disease (AITD) with and without thyroid-associated orbitopathy (TAO). This was a cross-sectional study conducted at an academic tertiary referral centre. Of 1310 patients with AITD [n = 777 or 59% with Graves' disease (GD) and n = 533, 41% with Hashimoto's thyroiditis (HT)] followed at a specialized joint thyroid-eye out-patient clinic, 176 (13·4%) had an adult type of the autoimmune polyglandular syndrome, 129 (9·8%) type 1 diabetes, 111 (8·5%) coeliac disease, 60 (4·6%) type A autoimmune gastritis, 57 (4·4%) vitiligo and 25 (1·9%) Addison's disease. Coeliac disease and autoimmune gastritis were associated positively with GD [odds ratio (OR) = 2·18; P = 0·002 and OR = 6·52; P < 0·001], whereas type 1 diabetes, Addison's disease, autoimmune primary hypogonadism, alopecia areata, rheumatoid arthritis and Sjögren's syndrome were 'protective' for GD and thus linked to HT, OR = 0·49 (P < 0·001), 0·06 (P < 0·001), 0·25 (P < 0·001), 0·50 (P = 0·090) and 0·32 (P = 0·003), respectively. Of 610 (46·6%) AITD patients with TAO, 584 (95·7%) and 26 (4·3%) had GD and HT, respectively (P < 0·001). TAO was most prevalent in GD patients with coeliac disease (94%, OR = 1·87, P < 0·001). Multivariate analysis showed high OR for coeliac disease and autoimmune gastritis (3·4 and 4·03, both P < 0·001) pertaining to the association with TAO while type 1 diabetes, Addison's disease and alopecia areata were protective for TAO. In patients with TAO, coeliac disease is the most prevalent co-morbid autoimmune condition and rates are increased compared to GD patients without TAO.

Celiac anti-type 2 transglutaminase antibodies induce phosphoproteome modification in intestinal epithelial Caco-2 cells

BACKGROUND

Celiac disease is an inflammatory condition of the small intestine that affects genetically predisposed individuals after dietary wheat gliadin ingestion. Type 2-transglutaminase (TG2) activity seems to be responsible for a strong autoimmune response in celiac disease, TG2 being the main autoantigen. Several studies support the concept that celiac anti-TG2 antibodies may contribute to disease pathogenesis. Our recent findings on the ability of anti-TG2 antibodies to induce a rapid intracellular mobilization of calcium ions, as well as extracellular signal-regulated kinase phosphorylation, suggest that they potentially act as signaling molecules. In line with this concept, we have investigated whether anti-TG2 antibodies can induce phosphoproteome modification in an intestinal epithelial cell line.

METHODS AND PRINCIPAL FINDINGS

We studied phosphoproteome modification in Caco-2 cells treated with recombinant celiac anti-TG2 antibodies. We performed a two-dimensional electrophoresis followed by specific staining of phosphoproteins and mass spectrometry analysis of differentially phosphorylated proteins. Of 14 identified proteins (excluding two uncharacterized proteins), three were hypophosphorylated and nine were hyperphosphorylated. Bioinformatics analyses confirmed the presence of phosphorylation sites in all the identified proteins and highlighted their involvement in several fundamental biological processes, such as cell cycle progression, cell stress response, cytoskeletal organization and apoptosis.

CONCLUSIONS

Identification of differentially phosphorylated proteins downstream of TG2-antibody stimulation suggests that in Caco-2 cells these antibodies perturb cell homeostasis by behaving as signaling molecules. We hypothesize that anti-TG2 autoantibodies may destabilize the integrity of the intestinal mucosa in celiac individuals, thus contributing to celiac disease establishment and progression. Since several proteins here identified in this study were already known as TG2 substrates, we can also suppose that transamidating activity and differential phosphorylation of the same targets may represent a novel regulatory mechanism whose relevance in celiac disease pathogenesis is still unexplored.

Maize prolamins could induce a gluten-like cellular immune response in some celiac disease patients

Celiac disease (CD) is an autoimmune-mediated enteropathy triggered by dietary gluten in genetically prone individuals. The current treatment for CD is a strict lifelong gluten-free diet. However, in some CD patients following a strict gluten-free diet, the symptoms do not remit. These cases may be refractory CD or due to gluten contamination; however, the lack of response could be related to other dietary ingredients, such as maize, which is one of the most common alternatives to wheat used in the gluten-free diet. In some CD patients, as a rare event, peptides from maize prolamins could induce a celiac-like immune response by similar or alternative pathogenic mechanisms to those used by wheat gluten peptides. This is supported by several shared features between wheat and maize prolamins and by some experimental results. Given that gluten peptides induce an immune response of the intestinal mucosa both in vivo and in vitro, peptides from maize prolamins could also be tested to determine whether they also induce a cellular immune response. Hypothetically, maize prolamins could be harmful for a very limited subgroup of CD patients, especially those that are non-responsive, and if it is confirmed, they should follow, in addition to a gluten-free, a maize-free diet.

Usefulness of the organ culture system when villous height/crypt depth ratio, intraepithelial lymphocyte count, or serum antibody tests are not diagnostic for celiac disease

The existence of mild forms of celiac disease (CD) can make the histology-based diagnosis difficult to reach. Since anti-endomysium (EMA) and anti-tissue transglutaminase (anti-tTG) are detectable in culture supernatants of duodenal biopsies from CD patients, our aim was to assess if this system can support the histology in the diagnostic work-up. A total of 559 suspected CD patients underwent serum EMA/anti-tTG detection, upper endoscopy with duodenal biopsy sampling, histologic analysis, and organ culture to detect EMA/anti-tTG in supernatants. A subgroup of 30 patients with organ culture positive results were put on a gluten-free diet (GFD). Their gluten-dependency was evaluated by the psychological general well-being and beck depression inventory indexes. Statistical analysis was performed by Cohen k inter-test, Friedman test, and Dunn multiple comparison. Two hundred forty-one out of 559 (43.1%) patients showed intestinal villous atrophy, whereas serum and organ culture EMA/anti-tTG were positive in 293/559 (52.4%) and 334/559 (59.7%) patients, respectively. The strength of agreement resulted good for serology vs histology (k = 0.730), good for organ culture vs histology (k = 0.662), and very good for serology vs organ culture (k = 0.852). After 12 months of GFD, psychological general well-being index significantly increased, and beck depression inventory index significantly decreased (P < 0.001 for each one). Data highlight the organ culture system as a useful tool to assist the histology in diagnosing CD, mainly in cases without villous atrophy or in seronegative patients. The marked improvement in quality of life after a GFD further supports the reliability of this system in diagnosing CD.

Antibody repertoire profiling using bacterial display identifies reactivity signatures of celiac disease

A general strategy to identify serum antibody specificities associated with a given disease state and peptide reagents for their detection was developed using bacterial display peptide libraries and multiparameter flow cytometry (MPFC). Using sera from patients with celiac disease (CD) (n = 45) or healthy subjects (n = 40), bacterial display libraries were screened for peptides that react specifically with antibodies from CD patients and not with those from healthy patients. The libraries were screened for peptides that simultaneously cross-react with CD patient antibodies present in two separate patient groups labeled with spectrally distinct fluorophores but do not react with unlabeled non-CD antibodies, thus affording a quantitative separation. A panel of six unique peptide sequences yielded 85% sensitivity and 91% specificity (AUC = 0.91) on a set of 60 samples not used for discovery, using leave-one-out cross-validation. Individual peptides were dissimilar with known CD-specific antigens tissue transglutaminase (tTG) and deamidated gliadin, and the classifier accuracy was independent of anti-tTG antibody titer. These results demonstrate that bacterial display/MPFC provides a highly effective tool for the unbiased discovery of disease-associated antibody specificities and peptide reagents for their detection that may have broad utility for diagnostic development.

Concomitant autoantibodies in newly diagnosed diabetic children with transient celiac serology or proven celiac disease

BACKGROUND

We previously demonstrated that children with Type 1 Diabetes Mellitus (T1DM) may have transiently elevated tissue transglutaminase antibodies (TTG) on a gluten-containing diet. This study aimed to examine if the presence of autoantibodies in newly diagnosed T1DM differs between patients with celiac disease and those with transient celiac serology.

METHODS

Forty children were identified who had been diagnosed with T1DM between 2003 and 2009 and who had elevated serum IgA-TTG antibody levels at diagnosis. Blood samples were collected for measurement of insulin (IA-2A) antibodies, islet cell antigen (ICA) antibodies, glutamic acid decarboxylase (GAD) antibodies, thyroglobulin (TgAb) antibodies, and thyroid peroxidase (TPO) antibodies. Children diagnosed with celiac disease (CD; group 1, n=23) and children in whom TTG antibody levels spontaneously normalized over time (group 2, n=17) were compared.

RESULTS

No significant differences in positivity rates between groups 1 and 2 were found for any of the autoantibodies tested. The respective findings were as follows: IA-2A 50% and 47.1% (p=0.855); ICA 77.3% and 76.5% (p=0.953); GAD 27.3% and 52.9% (p=0.102). Thyroid antibodies were found positive in a limited number of patients: TgAb 4.5% and 11.8%; TPO 4.5% and 11.8%. In addition, antibody titer levels did not differ significantly for all autoantibodies. Difference in occurrence of clinical or subclinical thyroid disease did not reach significance (4.3% vs. 29.4%; p=0.07). Age was positively correlated with the presence of thyroglobulin and thyroid peroxidase antibodies, and negatively correlated with the presence of insulin antibody.

CONCLUSION

Neither the number of concomitant autoantibodies nor their titers in newly diagnosed T1DM differed between patients with proven CD and those with transient TTG serology.

Prenatal and Postnatal Epigenetic Programming: Implications for GI, Immune, and Neuronal Function in Autism

Although autism is first and foremost a disorder of the central nervous system, comorbid dysfunction of the gastrointestinal (GI) and immune systems is common, suggesting that all three systems may be affected by common molecular mechanisms. Substantial systemic deficits in the antioxidant glutathione and its precursor, cysteine, have been documented in autism in association with oxidative stress and impaired methylation. DNA and histone methylation provide epigenetic regulation of gene expression during prenatal and postnatal development. Prenatal epigenetic programming (PrEP) can be affected by the maternal metabolic and nutritional environment, whereas postnatal epigenetic programming (PEP) importantly depends upon nutritional support provided through the GI tract. Cysteine absorption from the GI tract is a crucial determinant of antioxidant capacity, and systemic deficits of glutathione and cysteine in autism are likely to reflect impaired cysteine absorption. Excitatory amino acid transporter 3 (EAAT3) provides cysteine uptake for GI epithelial, neuronal, and immune cells, and its activity is decreased during oxidative stress. Based upon these observations, we propose that neurodevelopmental, GI, and immune aspects of autism each reflect manifestations of inadequate antioxidant capacity, secondary to impaired cysteine uptake by the GI tract. Genetic and environmental factors that adversely affect antioxidant capacity can disrupt PrEP and/or PEP, increasing vulnerability to autism.

Kinetic and functional characterisation of the heparin-binding peptides from human transglutaminase 2

Transglutaminase 2 (TG2) is an autoantigen in celiac disease (CD) and it has multiple biologic functions including involvement in cell adhesion through interactions with integrins, fibronectin (FN), and heparan sulfate proteoglycans. We aimed to delineate the heparin-binding regions of human TG2 by studying binding kinetics of the predicted heparin-binding peptides using surface plasmon resonance method. In addition, we characterized immunogenicity of the TG2 peptides and their effect on cell adhesion. The high-affinity binding of human TG2 to the immobilized heparin was observed, and two TG2 peptides, P1 (amino acids 202-215) and P2 (261-274), were found to bind heparin. The amino acid sequences corresponding to the heparin-binding peptides were located close to each other on the surface of the TG2 molecule as part of the α-helical structures. The heparin-binding peptides displayed increased immunoreactivity against serum IgA of CD patients compared with other TG2 peptides. The cell adhesion reducing effect of the peptide P2 was revealed in Caco-2 intestinal epithelial cell attachment to the FN and FN-TG2 coated surfaces. We propose that TG2 amino acid sequences 202-215 and 261-274 could be involved in binding of TG2 to cell surface heparan sulfates. High immunoreactivity of the corresponding heparin-binding peptides of TG2 with CD patient's IgA supports the previously described role of anti-TG2 autoantibodies interfering with this interaction.

Role of transglutaminase 2 in celiac disease pathogenesis

A number of lines of evidence suggest that transglutaminase 2 (TG2) may be one of the earliest disease-relevant proteins to encounter immunotoxic gluten in the celiac gut. These and other investigations also suggest that the reaction catalyzed by TG2 on dietary gluten peptides is essential for the pathogenesis of celiac disease. If so, several questions are of critical significance. How is TG2 activated in the celiac gut? What are the disease-specific and general consequences of activating TG2? Can local inhibition of TG2 in the celiac intestine suppress gluten induced pathogenesis in a dose-responsive manner? And what are the long-term consequences of suppressing TG2 activity in the small intestinal mucosa? Answers to these questions will depend upon the development of judicious models and chemical tools. They also have the potential of yielding powerful next-generation drug candidates for treating this widespread but overlooked chronic disease.

Maize prolamins resistant to peptic-tryptic digestion maintain immune-recognition by IgA from some celiac disease patients

Maize is used as an alternative to wheat to elaborate food stuffs for celiac patients in a gluten-free diet.However, some maize prolamins (zeins) contain amino acid sequences that resemble the wheat gluten immunodominant peptides and their integrity after gastrointestinal proteolysisis unknown. In this study, the celiac IgA-immunoreactivity to zeins from raw or nixtamalized grains, before and after peptic/tryptic digestion was evaluated and their possible immunogenicity was investigated by in silico methods.IgA from some celiac patients with HLA-DQ2 or DQ8 haplotypes recognized two alpha-zeins even after peptic/ tryptic proteolysis. However, digestion affected zeins after denaturation, reduction, and alkylation, used for identification of prolamins as alpha-zein A20 and A30 by MS/MS sequencing. An in silico analysis indicated that other zeins contain similar sequences, or sequences that may bind even better to the HLA-DQ2/DQ8 molecules compared to the already identified ones. Results concur to indicate that relative abundance of these zeins, along with factors affecting their resistance to proteolysis, may be of paramount clinical relevance, and the use of maize in the formulation and preparation of gluten-free foods must be reevaluated in some cases of celiac disease.

New understanding of gluten sensitivity

Among gluten-related disorders, gluten sensitivity is an emerging entity that is characterized by a wide array of manifestations. In particular, patients complain of IBS-like symptoms and extraintestinal manifestations that occur shortly after the ingestion of gluten. Symptoms improve or disappear when gluten is withdrawn from the diet, and recur if gluten is reintroduced. Laboratory tests are usually unhelpful for diagnosis, although ~50% of patients are positive for IgG antigliadin antibodies. The natural history of gluten sensitivity is unknown; in particular, it is still to be clarified whether this disorder is permanent or transient and whether it is linked to autoimmunity. The pathogenesis of gluten sensitivity is unclear; data so far demonstrate a predominant activation of innate immune responses. Further research is necessary to establish the main clinicopathological features of gluten sensitivity, thus enabling physicians to improve their management of the increasing number of patients who are sensitive to dietary gluten.

Sensory neuronopathy and autoimmune diseases

Sensory neuronopathies (SNs) are a specific subgroup of peripheral nervous system diseases characterized by primary degeneration of dorsal root ganglia and their projections. Multifocal sensory symptoms often associated to ataxia are the classical features of SN. Several different etiologies have been described for SNs, but immune-mediated damage plays a key role in most cases. SN may herald the onset of some systemic autoimmune diseases, which further emphasizes how important the recognition of SN is in clinical practice. We have thus reviewed available clinical, neurophysiological, and therapeutic data on autoimmune disease-related SN, namely, in patients with Sjögren's syndrome, autoimmune hepatitis, and celiac disease.

Anti-tissue transglutaminase antibodies activate intracellular tissue transglutaminase by modulating cytosolic Ca2+ homeostasis

Anti-tissue transglutaminase (tTG) antibodies are specifically produced in the small-intestinal mucosa of celiac disease (CD) patients. It is now recognized that these antibodies, acting on cell-surface tTG, may play an active role in CD pathogenesis triggering an intracellular response via the activation of different signal transduction pathways. In this study, we report that anti-tTG antibodies, both commercial and from a CD patient, induce a rapid Ca(2+) mobilization from intracellular stores in Caco-2 cells. We characterized the mechanism of Ca(2+) release using thapsigargin and carbonylcyanide-p-trifluoromethoxyphenylhydrazone, which are able to deplete specifically endoplasmic reticulum and mitochondria of Ca(2+), respectively. Our data highlight that both pathways of calcium release were involved, thus indicating that the spectrum of cellular responses downstream can be very wide. In addition, we demonstrate that the increased Ca(2+) level in the cells evoked by anti-tTG antibodies was sufficient to activate tTG, which is normally present as a latent protein due to the presence of low Ca(2+) and to the inhibitory effect of GTP/GDP. Herein, we discuss the importance of intracellular tTG activation as central in the context of CD pathogenesis.

Transglutaminase 6: a protein associated with central nervous system development and motor function

Transglutaminases (TG) form a family of enzymes that catalyse various post-translational modifications of glutamine residues in proteins and peptides including intra- and intermolecular isopeptide bond formation, esterification and deamidation. We have characterized a novel member of the mammalian TG family, TG6, which is expressed in a human carcinoma cell line with neuronal characteristics and in mouse brain. Besides full-length protein, alternative splicing results in a short variant lacking the second β-barrel domain in man and a variant with truncated β-sandwich domain in mouse. Biochemical data show that TG6 is allosterically regulated by Ca²⁺ and guanine nucleotides. Molecular modelling indicates that TG6 could have Ca²⁺ and GDP-binding sites related to those of TG3 and TG2, respectively. Localization of mRNA and protein in the mouse identified abundant expression of TG6 in the central nervous system. Analysis of its temporal and spatial pattern of induction in mouse development indicates an association with neurogenesis. Neuronal expression of TG6 was confirmed by double-labelling of mouse forebrain cells with cell type-specific markers. Induction of differentiation in mouse Neuro 2a cells with NGF or dibutyryl cAMP is associated with an upregulation of TG6 expression. Familial ataxia has recently been linked to mutations in the TGM6 gene. Autoantibodies to TG6 were identified in immune-mediated ataxia in patients with gluten sensitivity. These findings suggest a critical role for TG6 in cortical and cerebellar neurons.

Mean platelet volume could be a promising biomarker to monitor dietary compliance in celiac disease

BACKGROUND

Celiac disease (CD) is an autoimmune disease that develops in patients with a genetic predisposition, incurring a susceptibility to gluten-containing foods such as barley, wheat, and rye. The elimination of gluten from the diet is the main therapeutic approach and usually leads to clinical and laboratory improvement. There are no ideal markers that objectively assess dietary compliance in CD patients.

MATERIALS AND METHODS

Sixty newly diagnosed CD patients (male/female: 43/17) and 40 healthy subjects (male/female: 23/17) were enrolled in this study. The diagnosis of CD was established by both histological findings of duodenum biopsy (total villous atrophy and lymphocytic infiltration) and positive antibodies against endomysium or gliadin.

RESULTS

A significantly higher mean platelet volume (MPV) was observed in the CD group compared with healthy subjects (8.45 ± 0.96 fL versus 7.93 ± 0.63 fL; p = 0.004). After introduction of a gluten-free diet, the MPV of CD patients in the dietary adherent group was significantly lower than that of the non-adherent group (8.09 ± 0.6 fL versus 8.9 ± 1.08 fL; p = 0.001). Overall dietary adherence rate was 71.6% (43/60 CD patients). In the dietary compliant group, initiation of gluten-free diet was associated with a significant decrease in MPV from base-line values (8.56 fL versus 8.25 fL; p = 0.008). In the non-adherent group, MPV on 3-month follow-up was higher than at base-line (8.05 fL versus 8.91 fL; p = 0.001).

CONCLUSION

MPV could be a promising and easily available biomarker for monitoring of dietary adherence in CD patients at a low cost in comparison with other modalities.