Molecular basis of celiac disease

New Insights on Genes, Gluten, and Immunopathogenesis of Celiac Disease

Celiac disease (CeD) is a gluten-induced enteropathy that develops in genetically susceptible individuals upon consumption of cereal gluten proteins. It is a unique and complex immune disorder to study as the driving antigen is known and the tissue targeted by the immune reaction can be interrogated. This review integrates findings gained from genetic, biochemical, and immunologic studies, which together have revealed mechanisms of gluten peptide modification and HLA binding, thereby enabling a maladapted anti-gluten immune response. Observations in human samples combined with experimental mouse models have revealed that the gluten-induced immune response involves CD4+ T cells, cytotoxic CD8+ T cells, and B cells; their cross-talks are critical for the tissue-damaging response. The emergence of high-throughput technologies is increasing our understanding of the phenotype, location, and presumably function of the gluten-specific cells, which are all required to identify novel therapeutic targets and strategies for CeD.

Potential therapeutic options for celiac Disease: An update on Current evidence from Gluten-Free diet to cell therapy

Celiac disease (CD) is a chronic autoimmune enteropathy and multifactorial disease caused by inappropriate immune responses to gluten in the small intestine. Weight loss, anemia, osteoporosis, arthritis, and hepatitis are among the extraintestinal manifestations of active CD. Currently, a strict lifelong gluten-free diet (GFD) is the only safe, effective, and available treatment. Despite the social burden, high expenses, and challenges of following a GFD, 2 to 5 percent of patients do not demonstrate clinical or pathophysiological improvement. Therefore, we need novel and alternative therapeutic approaches for patients. Innovative approaches encompass a broad spectrum of strategies, including enzymatic degradation of gluten, inhibition of intestinal permeability, modulation of the immune response, inhibition of the transglutaminase 2 (TG2) enzyme, blocking antigen presentation by HLA-DQ2/8, and induction of tolerance. Hence, this review is focused on comprehensive therapeutic strategies ranging from dietary approaches to novel methods such as antigen-based immunotherapy, cell and gene therapy, and the usage of nanoparticles for CD treatment.

Coeliac disease: the paradox of diagnosing a food hypersensitivity disorder with autoantibodies

Serum antibodies to the autoantigen transglutaminase 2 (TG2) are increasingly harnessed to diagnose coeliac disease. Diagnostic guidelines for children give recommendation for a no-biopsy-based diagnosis through detection of high amounts of IgA anti-TG2 antibodies in serum with confirmation of positivity in a separate blood sample by characteristic autoantibody-staining of tissue. While measurement of IgA anti-TG2 also is important in the diagnostic workup of adults, the adult guidelines still mandate examination of gut biopsies. This requirement might well change in the future, as might the necessity for confirming autoantibody positivity by tissue staining. The key role of autoantibody serology for diagnosis of coeliac disease is paradoxical. Coeliac disease was considered, and still can be considered, a food intolerance disorder where autoantibodies at face value are out of place. The immunological mechanisms underlying the formation of autoantibodies in response to gluten exposure have been dissected. This review presents the current insights demonstrating that the autoantibodies in coeliac disease are intimately integrated in the maladapted immune response to gluten.

Accounting for the health risk of probiotics

Probiotics have long been associated with a myriad of health benefits, so much so that their adverse effects whether mild or severe, are often neglected or overshadowed by the enormous volume of articles describing their beneficial effects in the current literature. Recent evidence has demonstrated several health risks of probiotics that warrant serious reconsideration of their applications and further investigations. This review aims to highlight studies that report on how probiotics might cause opportunistic systemic and local infections, detrimental immunological effects, metabolic disturbance, allergic reactions, and facilitating the spread of antimicrobial resistance. To offer a recent account of the literature, articles within the last five years were prioritized. The narration of these evidence was based on the nature of the studies in the following order of preference: clinical studies or human samples, in vivo or animal models, in situ, in vitro and/or in silico. We hope that this review will inform consumers, food scientists, and medical practitioners, on the health risks, while also encouraging research that will focus on and clarify the adverse effects of probiotics.

A possible unexpected link: Could wheat elimination trigger food protein-induced enterocolitis syndrome in a celiac disease patient?

Cases of association between celiac disease and wheat allergy have been described in the literature. However, to date, no reported cases have linked celiac disease with wheat food protein-induced enterocolitis syndrome (FPIES). We report a case of this association. A child diagnosed with celiac disease at the age of 2 years, following a gluten-free diet, experienced uncontrollable vomiting, and subsequent hypotension within 2 h of accidental ingestion of wheat flour. As a result, the child required hospitalization for fluid therapy. A similar episode occurred when the child turned 5 y, again resulting from accidental gluten ingestion. This time, the symptoms included vomiting, hypotension, and a loss of consciousness, leading to hospitalization for rehydration treatment. After this second episode, on suspicion of FPIES, the patient was referred to the pediatric allergists, who confirmed the diagnosis. To our knowledge, this is the first case of an association between celiac disease and FPIES. It has been hypothesized that exclusion diets in food-allergic children may lead to an increase in specific immunoglobulin E levels for those foods and, consequently, the risk of anaphylaxis. However, FPIES is not an immunoglobulin E-mediated condition. Hence, further investigations are warranted to elucidate the underlying mechanisms linking these 2 disorders.

Total serum IgA levels and HLA-DQB1*02:01 allelic status

Immunoglobulin A Deficiency (IgAD) is the most common primary immunodeficiency and is significantly associated with Celiac Disease (CD), which recognizes a specific background of human leukocyte antigens (HLA) predisposition (including HLA-DQB1*02:01 allele). A number of studies investigated the role of HLA in IgAD etiopathogenesis: HLA-DQB1*02 alleles are included in the main haplotypes linked to this primary immunodeficiency. In this preliminary study, we investigated the potential impact of HLA-DQB1*02:01 allelic status on total serum IgA levels: 108 serum samples from the bone marrow donors' registry were analyzed for total IgA concentration with respect to the HLA-DQB1*02:01 status. Although total serum IgA levels between HLA-DQB1*02:01 carriers and HLA-DQB1*02:01 negative donors were not different, we observed a statistically significant difference (p=0.0118) in total serum IgA levels among donors with low IgA concentration (<80mg/dL) in the sub-analysis between HLA-DQB1*02:01 positive group (including both homozygous and heterozygous carriers) compared to HLA-DQB1*02:01 negative donors. Our results might suggest a role of HLA-DQB1*02:01 allelic variant in the determination of total serum IgA levels, at least in patients affected with IgA deficiency and/or otherwise predisposed to it; however, larger and more standardized studies are needed to confirm this speculation.

Expression of Elafin and CD200 as Immune Checkpoint Molecules Involved in Celiac Disease

We comprehensively evaluated the expression of therapeutically targetable immune checkpoint molecules involved in celiac disease (CD). We have focused on the alteration of the CD200/CD200R pathway and Elafin expression in celiac disease and discussed their roles in regulating the immune response. There are limited data related to the expression or function of these molecules in celiac disease. This finding could significantly contribute to the understanding of the clinical manifestation of CD. CD200, CD200R and Elafin distributions were determined by ELISA and immunohistochemistry analyses in serum and biopsies of CD patients. Analyses of Th1 and Th17 cytokines were determined. PCR amplification of a fragment of the PI3 gene was carried out using genomic DNA isolated from whole blood samples of the study subjects. Different aliquots of the PCR reaction product were subjected to RFLP analysis for SNP genotyping and detection. We characterized the expression and function of the CD200-CD200R axis and PI3 in celiac disease. A significantly higher level of soluble CD200 and CD200R and lower expression of PI3 in serum of CD patients was observed compared to healthy controls. Consistent with our results, CD200 expression is regulated by IFN-gamma. Interaction of CD200/CD200R leads to production of type-Th1 and -Th17 cytokines. Regarding the PI3 genotype, the CT genotype proportion SNP rs1733103 and the GG genotype SNP rs41282752 were predominant in CD patients. SNP rs1733103 showed a significant association between the SNP variables and CD. In celiac disease the immune checkpoint is compromised or dysregulated, which can contribute to inflammation and the autoimmunity process. The study of these checkpoint points will lead to the development of targeted therapies aimed at restoring immunological balance in CD. Specific coding regions of the PI3 gene-splice variants predispose the Elafin protein, both at the transcriptional and post-translational levels, to modify its expression and function, resulting in reduced differential functional protein levels in patients with active celiac disease.

Detoxification of Wheat Gluten by Enzymatic Transamidation under Reducing Condition and Its Application in Typical Food Model

SCOPE

Gluten, the primary network builder of wheat dough, is responsible for celiac disease or wheat allergy. Transamidation of gluten under reduction conditions has been shown to reduce the potential toxicity of celiac disease, but its application in food preparation has not been extensively studied. This work investigates the use of transamidation in food preparation to address this gap in knowledge.

METHODS AND RESULTS

This study investigates the effects of transamidation on the toxicity of commercial wheat flour and the apparent structure, digestive level, and rheological characteristics of resultant dough and steamed bread, as a typical food model. The results show that transamidation starts at the kneading stage, as evaluated by using R5 enzyme-linked immunoassay and rat basophils. The potential toxicity of celiac disease is reduced by about 83% when 1% microbial transglutaminase (mTG), 2% l-lysine, and 1% reduced glutathione (GSH) are added, while retaining the original physical and rheological properties of wheat flour. The additional of reduced GSH also improves the in vitro protein digestibility.

CONCLUSIONS

Although it cannot be a celiac disease treatment directly, this study suggests that transamidation can serve as an alternative method for reducing the gluten toxicity of wheat flour-based food products.

Hydrolysis of Gluten-Derived Celiac Disease-Triggering Peptides across a Broad pH Range by RmuAP1: A Novel Aspartic Peptidase Isolated from Rhodotorula mucilaginosa

An aspartate peptidase with proteolytic activity toward gluten was identified from an isolated red yeast Rhodotorula mucilaginosa strain. This peptidase consists of 425 amino acids, comprising an N-terminal signal peptide, a propeptide, and a C-terminal catalytic domain. The catalytic domain, termed RmuAP1CD, could be secreted by the recombinant oleaginous yeast Yarrowia lipolytica, whose genome contains the expression cassette for RmuAP1CD. RmuAP1CD exhibited optimum activity at pH 2.5 when acting on bovine serum albumin. Moreover, it facilitated the hydrolysis of gluten-derived immunogenic peptides (GIPs), which are responsible for triggering celiac disease symptoms, across a pH range of 3.0-6.0. The preferred cleavage sites are P-Q-Q-↓-P-Q in the 26-mer and P-Q-L-↓-P-Y in the 33-mer GIPs. Conversely, porcine pepsin cannot hydrolyze these two GIPs. The ability of RmuAP1CD to degrade GIPs under acidic conditions of the stomach indicates its potential as a viable oral enzyme therapy for celiac disease.

The Immunobiology and Pathogenesis of Celiac Disease

Among human leukocyte antigen (HLA)-associated disorders, celiac disease has an immunopathogenesis that is particularly well understood. The condition is characterized by hypersensitivity to cereal gluten proteins, and the disease lesion is localized in the gut. Still, the diagnosis can be made by detection of highly disease-specific autoantibodies to transglutaminase 2 in the blood. We now have mechanistic insights into how the disease-predisposing HLA-DQ molecules, via presentation of posttranslationally modified gluten peptides, are connected to the generation of these autoantibodies. This review presents our current understanding of the immunobiology of this common disorder that is positioned in the border zone between food hypersensitivity and autoimmunity.

Peculiar Ca2+ Homeostasis, ER Stress, Autophagy, and TG2 Modulation in Celiac Disease Patient-Derived Cells

Celiac disease (CD) is an inflammatory intestinal disease caused by the ingestion of gluten-containing cereals by genetically predisposed individuals. Constitutive differences between cells from CD patients and control subjects, including levels of protein phosphorylation, alterations of vesicular trafficking, and regulation of type 2 transglutaminase (TG2), have been reported. In the present work, we investigated how skin-derived fibroblasts from CD and control subjects responded to thapsigargin, an endoplasmic reticulum ER stress inducer, in an attempt to contribute to the comprehension of molecular features of the CD cellular phenotype. We analyzed Ca²⁺ levels by single-cell video-imaging and TG2 activity by a microplate assay. Western blots and PCR analyses were employed to monitor TG2 levels and markers of ER stress and autophagy. We found that the cytosolic and ER Ca²⁺ level of CD cells was lower than in control cells. Treatments with thapsigargin differently activated TG2 in control and CD cells, as well as caused slightly different responses regarding the activation of ER stress and the expression of autophagic markers. On the whole, our findings identified further molecular features of the celiac cellular phenotype and highlighted that CD cells appeared less capable of adapting to a stress condition and responding in a physiological way.

Frequency of celiac disease and distribution of HLA-DQ2/DQ8 haplotypes among siblings of children with celiac disease

BACKGROUND

Celiac disease (CD) is a multifactorial disease, but genetic factors play a major role in its etiology. It has been known that human leucocyte antigen (HLA)-DQ2/DQ8 haplotypes are one of the most important predisposing genetic factors. The risk of developing CD in first-degree relatives and especially siblings of celiac patients is quite high because of having the same HLA haplotypes.

AIM

To evaluate the frequency of CD and the distribution of the HLA-DQ2/DQ8 haplotypes in siblings of celiac patients.

METHODS

Patients with biopsy-proven CD and their siblings were included in the study; those who did not have HLA genotyping were excluded from the study. All siblings were on a gluten-containing diet. The HLA genotyping, tissue transglutaminase antibody IgA antibody test, and total IgA test were performed in all participants.

RESULTS

A total of 57 celiac patients and their 112 siblings were included in the study. The mean age of celiac patients and siblings were 10.30 ± 3.87 years and 9.90 ± 6.11 years, respectively. HLA-DQ2/DQ8 alleles were detected in 98.2% of patients with CD and 90.2% of siblings of celiac patients. HLA-DQ genotypes were present in all siblings diagnosed with CD. Tissue transglutaminase antibody IgA test was found to be positive in 16 siblings. CD was diagnosed in 12 siblings (10.7%) by intestinal biopsy.

CONCLUSION

The prevalence of CD was found to be 10.7% in siblings of celiac patients in our study. One-third of the siblings diagnosed with CD were asymptomatic. We detected HLA-DQ alleles in 98.2% of celiac patients and 100% in siblings diagnosed with CD. In addition, 1 of the 2 siblings was diagnosed with CD 1 year later and the other 4 years later. Therefore, we suggest that siblings of celiac patients should be followed up with clinical findings as well as HLA analysis and serological examination. Since the risk of developing CD is much higher in asymptomatic siblings, we recommend that siblings should be screened for CD even if they are asymptomatic.

Type 2 Transglutaminase in Coeliac Disease: A Key Player in Pathogenesis, Diagnosis and Therapy

Type 2 transglutaminase (TG2) is the main autoantigen in coeliac disease (CD), a widespread inflammatory enteropathy caused by the ingestion of gluten-containing cereals in genetically predisposed individuals. As a consequence, serum antibodies to TG2 represent a very useful marker in CD diagnosis. However, TG2 is also an important player in CD pathogenesis, for its ability to deamidate some Gln residues of gluten peptides, which become more immunogenic in CD intestinal mucosa. Given the importance of TG2 enzymatic activities in CD, several studies have sought to discover specific and potent inhibitors that could be employed in new therapeutical approaches for CD, as alternatives to a lifelong gluten-free diet. In this review, we summarise all the aspects regarding TG2 involvement in CD, including its enzymatic reactions in pathogenesis, the role of anti-TG2 antibodies in disease management, and the exploration of recent strategies to reduce deamidation or to use transamidation to detoxify gluten.

Gliadin-reactive vitamin D-sensitive proinflammatory ILCPs are enriched in celiac patients

Celiac disease (CD) is a multisystem disease in which different organs may be affected. We investigate whether circulating innate lymphoid cells (ILCs) contribute to the CD peripheral inflammatory status. We find that the CD cytokine profile is characterized by high concentrations of IL-12p40, IL-18, and IFN-γ, paralleled by an expansion of ILC precursors (ILCPs). In the presence of the gliadin peptides p31-43 and pα-9, ILCPs from CD patients increase transglutaminase 2 (TG2) expression, produce IL-18 and IFN-γ, and stimulate CD4⁺ T lymphocytes. IFN-γ is also produced upon stimulation with IL-12p40 and IL-18 and is inhibited by the addition of vitamin D. Low levels of blood vitamin D correlate with high IFN-γ and ILCP presence and mark the CD population mostly affected by extraintestinal symptoms. Dietary vitamin D supplementation appears to be an interesting therapeutic approach to dampen ILCP-mediated IFN-γ production.

Salivary gland involvement and oral health in patients with coeliac disease

Coeliac disease (CD) is a chronic immune‐mediated enteropathy triggered by ingestion of gluten. The aim of this study was to investigate if the salivary glands as a component of the mucosal immune system are involved in CD, leading to sialadenitis and salivary gland dysfunction and associated oral manifestations. Twenty patients with CD aged 49.2 (SD 15.5 years) and 20 age‐ and gender‐matched healthy controls underwent an interview regarding general and oral health, serological analysis, a clinical oral examination including bitewing radiographs, Candida smear, assessment of salivary mutans streptococci and lactobacilli levels, unstimulated and chewing‐stimulated whole and parotid saliva flow rates, analysis of secretory IgA, and a labial salivary gland biopsy. Xerostomia, mucosal lesions, dry/cracked lips and focal lymphocytic sialadenitis were more prevalent and extensive in patients with CD than in healthy controls. Moreover, the patients had less gingival inflammation and higher whole saliva flow rates than the healthy controls, but did not differ regarding dental health and levels of cariogenic bacteria and Candida. The major salivary gland function appears unaffected, contributing to maintenance of a balanced microbiota and oral health in CD patients. Xerostomia and labial dryness may be related to minor salivary gland inflammation and subsequent impaired mucosal lubrication.

Role of HLA-DQB1 alleles in the risk, signs and symptoms, and severity of celiac disease in a Venezuelan population

INTRODUCTION AND AIMS

Celiac disease (CD) is a complex condition, whose main genetic determinant involves HLA molecules, specifically the HLA-DQ2 and/or HLA-DQ8 heterodimers. Nevertheless, the frequency of the alleles encoding those molecules has not been reported in Venezuelan celiac patients. Therefore, the aim of our study was to evaluate the frequency of the HLA-DQB1 alleles in individuals with symptoms suggestive of CD and define the diagnostic markers of the condition in a Venezuelan population.

MATERIAL AND METHODS

A cross-sectional study included 516 individuals with symptoms suggestive of CD. Molecular typing of the HLA-DQB1 locus was performed using a polymerase chain reaction-sequence-specific oligonucleotide procedure (PCR-SSO).

RESULTS

A total of 58.3% of the individuals with clinical manifestations consistent with CD presented with at least one risk allele (DQB1*0201 and/or DQB1*0302), and the diagnosis was confirmed in 40 of them. The patients with CD had a higher frequency of the DQB1*0201 risk allele (26.25%), followed by the DQB1*0302 (17.5%) allele. There was an association between the presence of risk alleles and the presence of lesions characteristic of CD (P = 0.001), and a correlation was found between the genetic predisposition to develop CD and the presence of anti-tissue transglutaminase antibodies (P = 0.0127).

CONCLUSIONS

The results support the role of the DQB1*02 and DQB1*0302 alleles in CD susceptibility and the histologic alterations of the intestinal mucosa, in a Venezuelan population.

Dissection of the Genetic Architecture for Quantities of Gliadins Fractions in Wheat (Triticum aestivum L.)

Gliadin is a group of grain storage proteins that confers extensibility/viscosity to the dough and are vital to end-use quality in wheat. Moreover, gliadins are one of the important components for nutritional quality because they contain the nutritional unprofitable epitopes that cause chronic immune-mediated intestinal disorder in genetically susceptible individuals designated celiac disease (CD). The main genetic loci encoding the gliadins were revealed by previous studies; however, the genes related to the content of gliadins and their fractions were less elucidated. To illustrate the genetic basis of the content of gliadins and their fractions comprehensively, a recombinant inbred line (RIL) population that consisted of 196 lines was constructed from the two parents, Luozhen No.1 and Zhengyumai 9987. Quantitative trait loci (QTL) controlling the content of total gliadins and their fractions (ω-, α-, and γ-gliadin) were screened genome-widely under four environments across 2 years. Totally, thirty QTL which explained 1.97-12.83% of the phenotypic variation were detected to be distributed on 17 chromosomes and they were gathered into 12 clusters. One hundred and one pairs of epistatic QTL (E-QTL) were revealed, among which five were involved with the total gliadins and its fractions content QTL located on chromosome 1AS, 1DS, 4DS, 1DL, and 6AS. Three Kompetitive Allele-Specific PCR (KASP) markers were developed from three major QTL clusters located on chromosomes 6A, 6D, and 7D, respectively. The present research not only dissects the genetic loci for improving the content of gliadins and their three fractions, but may also contribute to marker-assisted selection of varieties with appropriate gliadin fractions content for end-use quality and health benefit at the early developmental stages and early breeding generations.

Gut tissue-resident memory T cells in coeliac disease

This mini-review describes observations of the 1990ies with culturing of gluten-specific and astrovirus-specific CD4⁺ T cells from duodenal biopsies from subjects who presumably had a long time between the exposure to gluten or astrovirus antigens and the sampling of the biopsy. In these studies, it was also observed that antigen-specific CD4⁺ T cells migrated out of the gut biopsies during overnight culture. The findings are suggestive of memory T cells in tissue which are resident, but which also can be mobilised on antigen stimulation. Of note, these findings were made years before the term tissue-resident memory T cells was invoked. Since that time, many observations have accumulated on these gut T cells, particularly the gluten-specific T cells, and we have insight into the turnover of CD4⁺ T cells in the gut lamina propria. These data make it evident that human antigen-specific CD4⁺ T cells that can be cultured from gut biopsies indeed are bone fide tissue-resident memory T cells.

Intestinal immune compartmentalization: implications of tissue specific determinants in health and disease

The emerging concept of tissue specific immunity has opened the gates to new inquiries into what factors drive immune cell niche adaptation and the implications on immune homeostasis, organ specific immune diseases, and therapeutic efficacy. These issues are particularly complicated at barrier sites, which are directly exposed to an ever-changing environment. In particular, the gastrointestinal (GI) tract faces even further challenges given the profound functional and structural differences along its length, raising the possibility that it may even have to be treated as multiple organs when seeking to answer these questions. In this review, we evaluate what is known about the tissue intrinsic and extrinsic factors shaping immune compartments in the intestine. We then discuss the physiological and pathological consequences of a regionally distinct immune system in a single organ, but also discuss where our insight into the role of the compartment for disease development is still very limited. Finally, we discuss the technological and therapeutic implications this compartmentalization has. While the gut is perhaps one of the most intensely studied systems, many of these aspects apply to understanding tissue specific immunity of other organs, most notably other barrier sites such as skin, lung, and the urogenital tract.

Effective Degradation of Gluten and Its Fragments by Gluten-Specific Peptidases: A Review on Application for the Treatment of Patients with Gluten Sensitivity

To date, there is no effective treatment for celiac disease (CD, gluten enteropathy), an autoimmune disease caused by gluten-containing food. Celiac patients are supported by a strict gluten-free diet (GFD). However, in some cases GFD does not negate gluten-induced symptoms. Many patients with CD, despite following such a diet, retain symptoms of active disease due to high sensitivity even to traces of gluten. In addition, strict adherence to GFD reduces the quality of life of patients, as often it is difficult to maintain in a professional or social environment. Various pharmacological treatments are being developed to complement GFD. One promising treatment is enzyme therapy, involving the intake of peptidases with food to digest immunogenic gluten peptides that are resistant to hydrolysis due to a high prevalence of proline and glutamine amino acids. This narrative review considers the features of the main proline/glutamine-rich proteins of cereals and the conditions that cause the symptoms of CD. In addition, we evaluate information about peptidases from various sources that can effectively break down these proteins and their immunogenic peptides, and analyze data on their activity and preliminary clinical trials. Thus far, the data suggest that enzyme therapy alone is not sufficient for the treatment of CD but can be used as a pharmacological supplement to GFD.

Potential Roles of Exosomal lncRNAs in the Intestinal Mucosal Immune Barrier

The intestinal mucosal immune barrier protects the host from the invasion of foreign pathogenic microorganisms. Immune cells and cytokines in the intestinal mucosa maintain local and systemic homeostasis by participating in natural and adaptive immunity. Deficiency of the intestinal mucosal immune barrier is associated with a variety of intestinal illnesses. Exosomes are phospholipid bilayer nanovesicles that allow cell-cell communication by secreting physiologically active substances including proteins, lipids, transcription factors, mRNAs, micro-RNAs (miRNAs), and long noncoding RNAs (lncRNAs). Exosomal lncRNAs are involved in immune cell differentiation and the modulation of the immune response. This review briefly introduces the potential role of exosomal lncRNAs in the intestinal mucosal immune barrier and discusses their relevance to intestinal illnesses.

Role and function of granin proteins in diabetes mellitus

The granin glycoprotein family consists of nine acidic proteins; chromogranin A (CgA), chromogranin B (CgB), and secretogranin II–VIII. They are produced by a wide range of neuronal, neuroendocrine, and endocrine cells throughout the human body. Their major intracellular function is to sort peptides and proteins into secretory granules, but their cleavage products also take part in the extracellular regulation of diverse biological processes. The contribution of granins to carbohydrate metabolism and diabetes mellitus is a recent research area. CgA is associated with glucose homeostasis and the progression of type 1 diabetes. WE-14, CgA_10-19, and CgA_43-52 are peptide derivates of CgA, and act as CD4⁺ or CD8⁺ autoantigens in type 1 diabetes, whereas pancreastatin (PST) and catestatin have regulatory effects in carbohydrate metabolism. Furthermore, PST is related to gestational and type 2 diabetes. CgB has a crucial role in physiological insulin secretion. Secretogranins II and III have angiogenic activity in diabetic retinopathy (DR), and are novel targets in recent DR studies. Ongoing studies are beginning to investigate the potential use of granin derivatives as drugs to treat diabetes based on the divergent relationships between granins and different types of diabetes.

Circulating CD103+ γδ and CD8+ T cells are clonally shared with tissue-resident intraepithelial lymphocytes in celiac disease

Gut intraepithelial γδ and CD8⁺ αβ T lymphocytes have been connected to celiac disease (CeD) pathogenesis. Based on the previous observation that activated (CD38⁺), gut-homing (CD103⁺) γδ and CD8⁺ αβ T cells increase in blood upon oral gluten challenge, we wanted to shed light on the pathogenic involvement of these T cells by examining the clonal relationship between cells of blood and gut during gluten exposure. Of 20 gluten-challenged CeD patients, 8 and 10 had increase in (CD38⁺CD103⁺) γδ and CD8⁺ αβ T cells, respectively, while 16 had increase in gluten-specific CD4⁺ T cells. We obtained γδ and αβ TCR sequences of >2500 single cells from blood and gut of 5 patients, before and during challenge. We observed extensive sharing between blood and gut γδ and CD8⁺ αβ T-cell clonotypes even prior to gluten challenge. In subjects with challenge-induced surge of γδ and/or CD8⁺ αβ T cells, as larger populations of cells analyzed, we observed more expanded clonotypes and clonal sharing, yet no discernible TCR similarities between expanded and/or shared clonotypes. Thus, CD4⁺ T cells appear to drive expansion of clonally diverse γδ or CD8⁺ αβ T-cell clonotypes that may not be specific for the gluten antigen.

Transamidation Down-Regulates Intestinal Immunity of Recombinant α-Gliadin in HLA-DQ8 Transgenic Mice

Enzymatic transamidation of gliadins by microbial transglutaminase (mTG) inhibits interferon-γ (IFN-γ) secretion by intestinal T cell lines in patients with celiac disease (CD). To gain insight into the cellular mechanisms underlying the down-regulatory effects of transamidation, we tested a single recombinant α-gliadin (r-gliadin) harbouring two immunodominant peptides, p13 (aa. 120–139) and p23 (aa. 220–239), in HLA-DQ8 transgenic mice, a model of gluten sensitivity. Mice were intranasally immunised with r-gliadin or r-gliadin transamidated by mTG (K-r-gliadin) along with cholera toxin, and the response of mesenteric lymph node cells was analysed by cytokine multiplex assay. An in vitro challenge with r-gliadin was characterised by secretion of specific cytokines featuring both innate immunity and the Th1/Th2/Th17 pattern of the adaptive response. Notably, transamidation specifically down-regulated the Th1 response. Structural studies performed on K-r-gliadin confirmed that specific glutamine residues in p13 and p23, previously found to be deamidated by tissue transglutaminase, were also transamidated by mTG. In silico analysis, simulating p13 and p23 peptide binding to HLA-DQ8 showed that these glutamines, in the form of glutamate, could interact by means of salt bridges with peculiar amino acids of the alpha chain of HLA-DQ8, suggesting that their transamidation may influence the HLA-restricted recognition of these peptides. Thus, the structural findings provided a rationale to explain the down-regulation of the r-gliadin-specific Th1 response following transamidation.

Hidden in Plain View: Discovery of Chimeric Diabetogenic CD4 T Cell Neo-Epitopes

The T cell antigens driving autoimmune Type 1 Diabetes (T1D) have been pursued for more than three decades. When diabetogenic CD4 T cell clones and their relevant MHCII antigen presenting alleles were first identified in rodents and humans, the path to discovering the peptide epitopes within pancreatic beta cell proteins seemed straightforward. However, as experimental results accumulated, definitive data were often absent or controversial. Work within the last decade has helped to clear up some of the controversy by demonstrating that a number of the important MHCII presented epitopes are not encoded in the natural beta cell proteins, but in fact are fusions between peptide fragments derived from the same or different proteins. Recently, the mechanism for generating these MHCII diabetogenic chimeric epitopes has been attributed to a form of reverse proteolysis, called transpeptidation, a process that has been well-documented in the production of MHCI presented epitopes. In this mini-review we summarize these data and their implications for T1D and other autoimmune responses.

Highly Efficient Deamidation of Wheat Gluten by Glucose-Citric Acid-Based Natural Deep Eutectic Solvent: A Potential Effective Reaction Media

An efficient technique using citric acid and glucose based natural deep eutectic solvent (G-C-NADES) was developed to obtain ultrahigh deamidated wheat gluten (UDWG) (deamidation degree (DD) > 90%). FTIR and ¹H NMR indicated intensive hydrogen bonds (HBs) in G-C-NADES supermolecules. Quantum chemical calculations and molecular dynamic simulations demonstrated that 10 wt % diluted G-C-NADES still had a myriad of HBs. Physicochemical results showed UDWG had DD up to 92.45% after G-C-NADES deamidation, that is, 22% higher than citric-acid-DWG with a weak degree of hydrolysis (1.75%). Conformational characterization demonstrated the obvious conversion from α-helix to β-sheet via FTIR, the least amount of disulfide bonds by Raman spectra, and more exposure of tryptophan residues by fluorescence measurement for UDWG. It is proven that enhanced accessible conformation of WG reached with HBs of G-C-NADESs could contribute to the improvement on nucleophilic attack of deamidation, declaring that G-C-NADES might be a potential solvent for obtaining an ultrahigh deamidation for WG to successfully guarantee the safety of wheat gluten based cereal food regarding to lowering its allergy.

Efficient Hydrolysis of Gluten-Derived Celiac Disease-Triggering Immunogenic Peptides by a Bacterial Serine Protease from Burkholderia gladioli

Celiac disease is an autoimmune disorder triggered by toxic peptides derived from incompletely digested glutens in the stomach. Peptidases that can digest the toxic peptides may formulate an oral enzyme therapy to improve the patients’ health condition. Bga1903 is a serine endopeptidase secreted by Burkholderia gladioli. The preproprotein of Bga1903 consists of an N-terminal signal peptide, a propeptide region, and an enzymatic domain that belongs to the S8 subfamily. Bga1903 could be secreted into the culture medium when it was expressed in E. coli. The purified Bga1903 is capable of hydrolyzing the gluten-derived toxic peptides, such as the 33- and 26-mer peptides, with the preference for the peptide bonds at the carbonyl site of glutamine (P1 position). The kinetic assay of Bga1903 toward the chromogenic substrate Z-HPQ-pNA at 37 °C, pH 7.0, suggests that the values of Km and k_cat are 0.44 ± 0.1 mM and 17.8 ± 0.4 s⁻¹, respectively. The addition of Bga1903 in the wort during the fermentation step of beer could help in making gluten-free beer. In summary, Bga1903 is usable to reduce the gluten content in processed foods and represents a good candidate for protein engineering/modification aimed to efficiently digest the gluten at the gastric condition.

A Cumulative Effect of Food and Viruses to Trigger Celiac Disease (CD): A Commentary on the Recent Literature

Celiac disease (CD) is a type of inflammatory chronic disease caused by nutrients such as gliadin that induce a TC (T cell)-mediated response in a partially known genetical background in an environment predisposed to inflammation, including viruses and food. Various experimental and clinical observations suggest that multiple agents such as viruses and bacteria have some common, inflammatory pathways predisposing individuals to chronic inflammatory diseases including celiac disease (CD). More recently, a Western diet and lifestyle have been linked to tissue inflammation and increase in chronic inflammatory diseases. In CD, the gliadin protein itself has been shown to be able to induce inflammation. A cooperation between viruses and gliadin is present in vitro and in vivo with common mechanisms to induce inflammation. Nutrients could have also a protective effect on CD, and in fact the anti-inflammatory Mediterranean diet has a protective effect on the development of CD in children. The possible impact of these observations on clinical practice is discussed.

Innate Lymphoid Cells and Celiac Disease: Current Perspective

Celiac disease (CD) is a common autoimmune disorder triggered by the ingestion of gluten in genetically susceptible individuals. Although the mechanisms underlying gliadin-mediated activation of adaptive immunity in CD have been well-characterized, regulation of innate immune responses and the functions of certain immune cell populations within the epithelium and lamina propria are not well-understood at present. Innate lymphoid cells (ILCs) are types of innate immune cells that have lymphoid morphology, lack antigen-specific receptors, and play important roles in tissue homeostasis, inflammation, and protective immune responses against pathogens. Information regarding the diversity and functions of ILCs in lymphoid organs and at mucosal sites has grown over the past decade, and roles of different ILC subsets in the pathogenesis of some inflammatory intestinal diseases have been proposed. However, our understanding of the contribution of ILCs toward the initiation and progression of CD is still limited. In this review, we discuss current pathophysiological aspects of ILCs within the gastrointestinal tract, findings of recent investigations characterizing ILC alterations in CD and refractory CD, and suggest avenues for future research.

Role of the gut microbiota in the pathogenesis of coeliac disease and potential therapeutic implications

PURPOSE

Although genetic predisposition and exposure to dietary gluten are considered necessary triggers for the development of coeliac disease, alterations in the gut microbial composition may also contribute towards the pathogenesis of coeliac disease. This review aims to provide an overview of the available data on the potential mechanisms through which the gut microbiota plays a role in the causation of coeliac disease and to discuss the potential therapeutic strategies that could diminish the consequences of microbial dysbiosis.

METHOD

A search of the literature was performed using the PubMed, Embase, and JSTOR databases; relevant articles were included.

RESULTS

Recent studies in patients with coeliac disease have reported an increase in the relative amounts of gram negative bacterial genera such as Bacteroides, Prevotella, and Escherichia, and reduced amounts of protective anti-inflammatory bacteria such as Bifidobacteria and Lactobacilli. Dysbiotic microbiota may lead to a dysregulated immune response that may contribute to the pathogenesis of coeliac disease. In infancy, antibiotic use and certain infant feeding practices may lead to alterations in the developing gut microbiota to influence the immune maturation process and predispose to coeliac disease.

CONCLUSION

The induction of the intestinal immune system and gluten intolerance may be influenced by the relative abundance of certain microbiota. Factors such as infant feeding practices, diet, antibiotics, and infections, may be involved in the development of coeliac disease due to their influence on gut microbial composition. The efficacy of potential modulators of the gut microbiota such as probiotics, prebiotics, and fecal microbial transplant as adjunctive treatments to gluten-free diet in coeliac disease is unproven and requires further investigation.

The Human Digestive Tract Is Capable of Degrading Gluten from Birth

The human gastrointestinal system has the capacity to metabolize dietary gluten. The capacity to degrade gliadin-derived peptide is present in humans from birth and increases during the first stages of life (up to 6–12 months of age). Fecal samples from 151 new-born and adult non-celiac disease (NCD) volunteers were collected, and glutenase and glianidase activities were evaluated. The capacity of total fecal proteins to metabolize 33-mer, 19-mer, and 13-mer gliadin peptides was also evaluated by high-performance liquid chromatography (HPLC). Feces from new-borns (meconium) showed glutenase and gliadinase activities, and peptidase activity against all three gliadin peptides. Maximal gluten degradative activity was observed in fecal samples from the youngest volunteers (0–12 months old). After the age of nine months, the gluten digestive capacity of gastrointestinal tract decreases and, from ±8 years old, individuals lose the ability to completely degrade toxic peptides. The gastrointestinal proteases involved in gluten digestion: elastase 2A, elastase 3B, and carboxipeptidase A1 are present from earlier stages of life. The human digestive tract contains the proteins capable of metabolizing gluten from birth, even before starting gluten intake. Humans are born with the ability to digest gluten and to completely degrade the potentially toxic gliadin-derived peptides (33-, 19-, and 13-mer).

Gluten Degrading Enzymes for Treatment of Celiac Disease

Celiac disease (CeD) affects about 1% of most world populations. It presents a wide spectrum of clinical manifestations, ranging from minor symptoms to mild or severe malabsorption, and it may be associated with a wide variety of autoimmune diseases. CeD is triggered and maintained by the ingestion of gluten proteins from wheat and related grains. Gluten peptides that resist gastrointestinal digestion are antigenically presented to gluten specific T cells in the intestinal mucosa via HLA-DQ2 or HLA-DQ8, the necessary genetic predisposition for CeD. To date, there is no effective or approved treatment for CeD other than a strict adherence to a gluten-free diet, which is difficult to maintain in professional or social environments. Moreover, many patients with CeD have active disease despite diet adherence due to a high sensitivity to traces of gluten. Therefore, safe pharmacological treatments that complement the gluten-free diet are urgently needed. Oral enzyme therapy, employing gluten-degrading enzymes, is a promising therapeutic approach. A prerequisite is that such enzymes are active under gastro-duodenal conditions, quickly neutralize the T cell activating gluten peptides and are safe for human consumption. Several enzymes including prolyl endopeptidases, cysteine proteases and subtilisins can cleave the human digestion-resistant gluten peptides in vitro and in vivo. Examples are several prolyl endopeptidases from bacterial sources, subtilisins from Rothia bacteria that are natural oral colonizers and synthetic enzymes with optimized gluten-degrading activities. Without exception, these enzymes must cleave the otherwise unusual glutamine and proline-rich domains characteristic of antigenic gluten peptides. Moreover, they should be stable and active in both the acidic environment of the stomach and under near neutral pH in the duodenum. This review focuses on those enzymes that have been characterized and evaluated for the treatment of CeD, discussing their origin and activities, their clinical evaluation and challenges for therapeutic application. Novel developments include strategies like enteric coating and genetic modification to increase enzyme stability in the digestive tract.

Gluten hydrolyzing activity of Bacillus spp isolated from sourdough

BACKGROUND

Celiac disease is an intestinal chronic disorder with multifactorial etiology resulting in small intestinal mucosal injuries and malabsorption. In genetically predisposed individuals with HLA DQ2/DQ8 molecules, the gluten domains rich in glutamine and proline present gluten domains to gluten reactive CD4+ T cells causing injury to the intestine. In the present experimental design, the indigenous bacteria from wheat samples were studied for their gluten hydrolyzing functionality.

RESULTS

Proteolytic activity of Bacillus spp. was confirmed spectrophotometrically and studied extensively on gliadin-derived synthetic enzymatic substrates, natural gliadin mixture, and synthetic highly immunogenic 33-mer peptide. The degradation of 33-mer peptide and the cleavage specificities of the selected isolates were analyzed by tandem mass spectrometry. The gluten content of the sourdough fermented by the chosen bacterial isolates was determined by R5 antibody based competitive ELISA. All the tested isolates efficiently hydrolyzed Z-YPQ-pNA, Z-QQP-pNA, Z-PPF-pNA, and Z-PFP-pNA and also cleaved 33-mer immunogenic peptide extensively. The gluten content of wheat sourdough was found to be below 110 mg/kg.

CONCLUSION

It has been inferred that four Bacillus spp especially GS 188 could be useful in developing gluten-reduced wheat food product for celiac disease prone individuals.

Intestinal Anti-tissue Transglutaminase2 Autoantibodies: Pathogenic and Clinical Implications for Celiac Disease

Celiac disease (CD) is a systemic disease that primarily affects the small intestine. The presence of anti-tissue transglutaminase 2 (anti-TG2) antibodies in the serum, as well as the presence of autoimmune phenomena, account for the inclusion of CD among autoimmune diseases. Anti-TG2 autoantibodies are produced at intestinal level, where they are deposited even before they appear in circulation. The pathogenic events that lead to their production are still not completely defined, but a central role seems to be played by gliadin-specific T cells. Interestingly, limited somatic mutations have been observed in VH and VL genes in TG2-specific plasma cells, another important aspect being the biased use of a heavy chain encoded by the VH5 gene. Conflicting data have been produced over the years on the effect of anti-TG2 antibodies on TG2 function. Although the presence of anti-TG2 antibodies in serum is considered a hallmark of CD and relevant from a clinical viewpoint, the role of these autoantibodies in the development of the celiac lesion remains to be defined. In the years, different technical approaches have been implemented to detect and measure intestinal CD-associated autoantibody production. Two aspects can make intestinal anti-TG2 antibodies relevant: from a clinical viewpoint: the first is their proposed ability in potential coeliac patients to predict the development of a full-blown enteropathy; the second is their possible role in revealing a condition of reactivity to gluten in patients with no circulating CD-associated autoantibodies. In fact, the detection of CD-specific autoantibodies production in the intestine, in the absence of serum positivity for the same antibodies, could be suggestive of a very early condition of gluten reactivity; alternatively, it could be not specific for CD and merely attributable to intestinal inflammation. In conclusion, the role of mucosal anti-TG2 antibodies in pathogenesis of CD is unknown. Their presence, the modalities of their production, their gluten dependence render them a unique model to study autoimmunity.

Genistein antagonizes gliadin-induced CFTR malfunction in models of celiac disease

In celiac disease (CD), an intolerance to dietary gluten/gliadin, antigenic gliadin peptides trigger an HLA-DQ2/DQ8-restricted adaptive Th1 immune response. Epithelial stress, induced by other non-antigenic gliadin peptides, is required for gliadin to become fully immunogenic. We found that cystic-fibrosis-transmembrane-conductance-regulator (CFTR) acts as membrane receptor for gliadin-derived peptide P31-43, as it binds to CFTR and impairs its channel function. P31-43-induced CFTR malfunction generates epithelial stress and intestinal inflammation. Maintaining CFTR in an active open conformation by the CFTR potentiators VX-770 (Ivacaftor) or Vrx-532, prevents P31-43 binding to CFTR and controls gliadin-induced manifestations. Here, we evaluated the possibility that the over-the-counter nutraceutical genistein, known to potentiate CFTR function, would allow to control gliadin-induced alterations. We demonstrated that pre-treatment with genistein prevented P31-43-induced CFTR malfunction and an epithelial stress response in Caco-2 cells. These effects were abrogated when the CFTR gene was knocked out by CRISP/Cas9 technology, indicating that genistein protects intestinal epithelial cells by potentiating CFTR function. Notably, genistein protected gliadin-sensitive mice from intestinal CFTR malfunction and gliadin-induced inflammation as it prevented gliadin-induced IFN-γ production by celiac peripheral-blood-mononuclear-cells (PBMC) cultured ex-vivo in the presence of P31-43-challenged Caco-2 cells. Our results indicate that natural compounds capable to increase CFTR channel gating might be used for the treatment of CD.

Interplay between Type 2 Transglutaminase (TG2), Gliadin Peptide 31-43 and Anti-TG2 Antibodies in Celiac Disease

Celiac disease (CD) is a common intestinal inflammatory disease involving both a genetic background and environmental triggers. The ingestion of gluten, a proteic component of several cereals, represents the main hexogen factor implied in CD onset that involves concomitant innate and adaptive immune responses to gluten. Immunogenicity of some gluten sequences are strongly enhanced as the consequence of the deamidation of specific glutamine residues by type 2 transglutaminase (TG2), a ubiquitous enzyme whose expression is up-regulated in the intestine of CD patients. A short gluten sequence resistant to intestinal proteases, the α-gliadin peptide 31-43, seems to modulate TG2 function in the gut; on the other hand, the enzyme can affect the biological activity of this peptide. In addition, an intense auto-immune response towards TG2 is a hallmark of CD. Auto-antibodies exert a range of biological effects on several cells, effects that in part overlap with those induced by peptide 31-43. In this review, we delineate a scenario in which TG2, anti-TG2 antibodies and peptide 31-43 closely relate to each other, thus synergistically participating in CD starting and progression.

Comparative Analysis of in vitro Digestibility and Immunogenicity of Gliadin Proteins From Durum and Einkorn Wheat

Recent studies suggested that gliadin proteins from the ancient diploid einkorn wheat Triticum monococcum retained a reduced number of immunogenic peptides for celiac disease patients because of a high in vitro digestibility with respect to hexaploid common wheat. In this study, we compared the immunological properties of gliadins from two Triticum monococcum cultivars (Hammurabi and Norberto-ID331) with those of a Triticum durum cultivar (Adamello). Gliadins were digested by mimicking the in vitro gastrointestinal digestion process that includes the brush border membrane peptidases. Competitive ELISA, based on R5 monoclonal antibody, showed that gastrointestinal digestion reduced the immunogenicity of Triticum monococcum gliadins; conversely, the immunogenic potential of Triticum durum gliadins remained almost unchanged by the in vitro digestion. The immune stimulatory activity was also evaluated by detecting the IFN-γ production in gliadin-reactive T-cell lines obtained from the small intestinal mucosa of HLA-DQ2+ celiac disease patients. Interestingly, gastrointestinal digestion markedly reduced the capability of Triticum monococcum gliadins (p <0.05) of both cultivars to activate T cells, while it slightly affected the activity of Triticum durum. In conclusion, our results showed that Triticum durum was almost unaffected by the in vitro gastrointestinal digestion, while Triticum monococcum had a marked sensibility to digestion, thus determining a lower toxicity for celiac disease patients.

Pathogenesis of Celiac Disease and Other Gluten Related Disorders in Wheat and Strategies for Mitigating Them

Wheat is a major cereal crop providing energy and nutrients to the billions of people around the world. Gluten is a structural protein in wheat, that is necessary for its dough making properties, but it is responsible for imparting certain intolerances among some individuals, which are part of this review. Most important among these intolerances is celiac disease, that is gluten triggered T-cell mediated autoimmune enteropathy and results in villous atrophy, inflammation and damage to intestinal lining in genetically liable individuals containing human leukocyte antigen DQ2/DQ8 molecules on antigen presenting cells. Celiac disease occurs due to presence of celiac disease eliciting epitopes in gluten, particularly highly immunogenic alpha-gliadins. Another gluten related disorder is non-celiac gluten-sensitivity in which innate immune-response occurs in patients along with gastrointestinal and non-gastrointestinal symptoms, that disappear upon removal of gluten from the diet. In wheat allergy, either IgE or non-IgE mediated immune response occurs in individuals after inhalation or ingestion of wheat. Following a life-long gluten-free diet by celiac disease and non-celiac gluten-sensitivity patients is very challenging as none of wheat cultivar or related species stands safe for consumption. Hence, different molecular biology, genetic engineering, breeding, microbial, enzymatic, and chemical strategies have been worked upon to reduce the celiac disease epitopes and the gluten content in wheat. Currently, only 8.4% of total population is affected by wheat-related issues, while rest of population remains safe and should not remove wheat from the diet, based on false media coverage.

Therapeutic options for coeliac disease: What else beyond gluten-free diet?

Coeliac disease is a chronic and systemic autoimmune condition triggered by gluten ingestion in genetically predisposed subjects. Currently, the only effective treatment available is a strict, lifelong gluten-free diet. However, patients perceive gluten withdrawal as an unsustainable burden in their life and some of them can exhibit persistent symptoms despite a strict diet. Thus, gluten-free diet represents a challenge, leading scientists to look for alternative or complementary treatments. This review will focus on non-dietary therapies for coeliac disease highlighting six therapeutic strategies: (1) decreasing gluten immunogenic content before it reaches the intestine; (2) sequestering gluten in the gut lumen before absorption; (3) blocking the passage of gluten through a leaky intestinal barrier; (4) preventing the enhancement of immune response against gliadin; (5) dampening the downstream immune activation; (6) inducing immune tolerance to gluten. Most developing therapies are only in the pre-clinical phase with only a few being tested in phase 2b or 3 trials. Although new approaches raise the hope for coeliacs giving them a chance to come back to gluten, for the time being a cautionary appraisal of new therapies suggests that they may have a complementary role to gluten withdrawal, mainly to prevent inadvertent gluten contamination.

A molecular basis for the T cell response in HLA-DQ2.2 mediated celiac disease

The highly homologous human leukocyte antigen (HLA)-DQ2 molecules, HLA-DQ2.5 and HLA-DQ2.2, are implicated in the pathogenesis of celiac disease (CeD) by presenting gluten peptides to CD4⁺ T cells. However, while HLA-DQ2.5 is strongly associated with disease, HLA-DQ2.2 is not, and the molecular basis underpinning this differential disease association is unresolved. We here provide structural evidence for how the single polymorphic residue (HLA-DQ2.5-Tyr22α and HLA-DQ2.2-Phe22α) accounts for HLA-DQ2.2 additionally requiring gluten epitopes possessing a serine at the P3 position of the peptide. In marked contrast to the biased T cell receptor (TCR) usage associated with HLA-DQ2.5-mediated CeD, we demonstrate with extensive single-cell sequencing that a diverse TCR repertoire enables recognition of the immunodominant HLA-DQ2.2-glut-L1 epitope. The crystal structure of two CeD patient-derived TCR in complex with HLA-DQ2.2 and DQ2.2-glut-L1 (PFSEQEQPV) revealed a docking strategy, and associated interatomic contacts, which was notably distinct from the structures of the TCR:HLA-DQ2.5:gliadin epitope complexes. Accordingly, while the molecular surfaces of the antigen-binding clefts of HLA-DQ2.5 and HLA-DQ2.2 are very similar, differences in the nature of the peptides presented translates to differences in responding T cell repertoires and the nature of engagement of the respective antigen-presenting molecules, which ultimately is associated with differing disease penetrance.

Diagnosing coeliac disease: Out with the old and in with the new?

Coeliac disease (CD) is a complex condition resulting from an interplay between genetic and environmental factors. When diagnosing the condition, serological testing and genotyping are useful in excluding CD, although the gold standard of testing is currently histopathological examination of the small intestine. There are drawbacks associated with this form of testing however and because of this, novel forms of testing are currently under investigation. Before we develop completely novel tests though, it is important to ask whether or not we can simply use the data we gather from coeliac patients more effectively and build a more accurate snapshot of CD through statistical analysis of combined metrics. It is clear that not one single test can accurately diagnose CD and it is also clear that CD patients can no longer be defined by discrete classifications, the continuum of patient presentation needs to be recognised and correctly captured to improve diagnostic accuracy. This review will discuss the current diagnostics for CD and then outline novel diagnostics under investigation for the condition. Finally, improvements to current protocols will be discussed with the need for a holistic "snapshot" of CD using a number of metrics simultaneously.

Association between HLA alleles and risk of celiac disease in Iranian patients

Celiac disease (CD) is a common autoimmune disease that is manifested by inflammation of the small intestine and varying extra intestinal symptoms, also considered to be associated with human HLA-DQ genes. In this study, 40 patients of CD and 40 healthy control samples were genotyped for HLA-DQB1 and 14 patients of CD and 14 healthy control samples were genotyped for HLA-DQA1genes using the SSP-PCR technique and a commercial kit.The DQA1*05 allele had the highest frequency among the patient group (42.86%). The frequency of this allele was 28.57% in healthy controls, and there was no statistically significant difference in this case (p= 0.771).The DQB1*02 allele was the most common in patients (33.75%) followed by the DQB1*03 allele (31.25%).The difference in frequency of the HLA-DQB1*02 allele in the patient and control groups was statistically significant (P= 0.0002, OR = 4.72). The remarkable differences in the distribution of HLA-DQ2 in Iranian patients compared to controls and relative risks signified the role of these alleles in the development of CD in Iranian patients and confirmed the likelihood of using HLA-DQ typing in the substantiation of the disease.

Diverse human leukocyte antigen association of type 1 diabetes in north India

BACKGROUND

Type 1 diabetes (T1D) is a complex disease, with involvement of various susceptibility genes. Human leukocyte antigen (HLA) on chromosome 6p21 is major susceptibility region. This study examined genetic association of HLA genes with T1D.

METHODS

The study recruited 259 T1D patients and 706 controls from north India. PCR-SSP and LiPA were used to type HLA Class I and II alleles.

RESULTS

At HLA Class I locus, HLA-A*02, A*26, B*08 and B*50 were significantly increased in patients vs controls (39.8% vs 28.9% [Bonferroni-corrected P {P_c } = 0.032], 24.7% vs 9.6% [P_c  = 4.83 × 10^-8 ], 37.2% vs 15.7% [P_c  = 1.92 × 10^-9 ], and 19.4% vs 5.5% [P_c  = 4.62 × 10^-9 ], respectively). Similarly, in Class II region, DRB1*03 showed a strong positive association with T1D (78.7% vs 17.5% in controls; P = 1.02 × 10^-9 ). Association of DRB1*04 with T1D (28.3% vs 15.5% in controls; P_c  = 3.86 × 10^-4 ) was not independent of DRB1*03. Negative associations were found between T1D and DRB1*07, *11, *13, and *15 (13.8% vs 26.1% in controls [P_c  = 0.00175], 3.9% vs 16.9% in controls [P_c  = 6.55× 10^-6 ], 5.5% vs 21.6% in controls [P_c  = 2.51 × 10^-7 ], and 16.9% vs 43.9% in controls [P_c  = 9.94× 10^-10 ], respectively). Compared with controls, patients had significantly higher haplotype frequencies of A*26-B*08-DRB1*03-DQA1*05-DQB1*02 (10.43% vs 1.96%; P = 7.62 × 10^-11 ), A*02-B*50-DRB1*03-DQA1*05-DQB1*02 (6.1% vs 0.71%; P = 2.19 × 10^-10 ), A*24-B*08-DRB1*03-DQA1*05-DQB1*02 (4.72% vs 0.8%; P = 5.4 × 10^-7 ), A*02-B*08-DRB1*03-DQA1*05-DQB1*02 (2.36% vs 0.18%; P = 3.6 × 10^-5 ), and A*33-B*58-DRB1*03-DQA1*05-DQB1*02 (4.33% vs 1.25%; P = 0.00019).

CONCLUSIONS

In north India, T1D is independently associated only with HLA-DRB1*03 haplotypes, and is negatively associated with DRB1*07, *11, *13, and *15.

Early Probiotic Supplementation and the Risk of Celiac Disease in Children at Genetic Risk

Probiotics are linked to positive regulatory effects on the immune system. The aim of the study was to examine the association between the exposure of probiotics via dietary supplements or via infant formula by the age of 1 year and the development of celiac disease autoimmunity (CDA) and celiac disease among a cohort of 6520 genetically susceptible children. Use of probiotics during the first year of life was reported by 1460 children. Time-to-event analysis was used to examine the associations. Overall exposure of probiotics during the first year of life was not associated with either CDA (n = 1212) (HR 1.15; 95%CI 0.99, 1.35; p = 0.07) or celiac disease (n = 455) (HR 1.11; 95%CI 0.86, 1.43; p = 0.43) when adjusting for known risk factors. Intake of probiotic dietary supplements, however, was associated with a slightly increased risk of CDA (HR 1.18; 95%CI 1.00, 1.40; p = 0.043) compared to children who did not get probiotics. It was concluded that the overall exposure of probiotics during the first year of life was not associated with CDA or celiac disease in children at genetic risk.

Reliability of coeliac serology in monitoring dietary adherence in children with coeliac disease on a gluten-free diet

This study aimed to determine the utility of coeliac serology for monitoring dietary adherence in coeliac disease. Serum anti-tTg IgA and anti-DGP IgG levels of 42 newly diagnosed patients were measured at diagnosis and at intervals of three, six and 12 months after starting a gluten-free diet. Both anti-tTg and anti-DGP antibodies decreased in all patients. The decline in the former was significantly greater at 3–12 months throughout, while in the latter the decline was seen only at three months but not subsequently. Serial measurement of coeliac serology may help in monitoring adherence to a gluten-free diet.

Role of anti-tissue transglutaminase IgA+IgG antibodies in detection of potential celiac disease in patients with type 1 diabetes

Background & objectives:

Celiac disease (CD) can exist in various forms in type 1 diabetes (T1D) patients and can remain undetected, leading to severe complications. This study was aimed to evaluate five commercially available anti-tissue transglutaminase (tTG) ELISA kits with distinct formats for the detection of CD and potential CD in T1D patients. Clinical and demographic profiles of the patients with different disease subsets were also studied.

Methods:

Fifty T1D patients with classical and non-classical symptoms of CD and 100 T1D patients without any symptoms of CD were included in this study. Anti-tTG autoantibody levels were estimated by five ELISA kits followed by histological examination of duodenal biopsy. HLA DQ2-DQ8 and DRB1-DQB1 typing was done, and serum levels for transforming growth factor (TGF)-β1 were also estimated.

Results:

Assay format detecting anti-tTG IgA antibodies against recombinant antigens along with neopeptides of gliadin was most efficient in the detection of CD in symptomatic patients, and assay format detecting IgA+IgG helped in the detection of potential CD in asymptomatic T1D patients. These findings were supported by histological examination and human leucocyte antigen analysis. Patients with potential CD were found to have markedly deranged glycaemic control parameters and also had significantly raised serum levels of TGF-β1, (P<0.05) compared to T1D patients.

Interpretation & conclusions:

Potential CD can be frequently seen in T1D patients. This can be attributed to the dietary patterns prevalent in the subcontinent and the genetic basis of the disease. Anti-tTG IgA+IgG antibodies can be useful in the detection of these potential CD cases in T1D patients. Early intervention with gluten-free diet can be considered in these patients for better disease management.