The interferon gamma gene in celiac disease: augmented expression correlates with tissue damage but no evidence for genetic susceptibility

Transcriptomic analysis of intestine following administration of a transglutaminase 2 inhibitor to prevent gluten-induced intestinal damage in celiac disease

Transglutaminase 2 (TG2) plays a pivotal role in the pathogenesis of celiac disease (CeD) by deamidating dietary gluten peptides, which facilitates antigenic presentation and a strong anti-gluten T cell response. Here, we elucidate the molecular mechanisms underlying the efficacy of the TG2 inhibitor ZED1227 by performing transcriptional analysis of duodenal biopsies from individuals with CeD on a long-term gluten-free diet before and after a 6-week gluten challenge combined with 100 mg per day ZED1227 or placebo. At the transcriptome level, orally administered ZED1227 effectively prevented gluten-induced intestinal damage and inflammation, providing molecular-level evidence that TG2 inhibition is an effective strategy for treating CeD. ZED1227 treatment preserved transcriptome signatures associated with mucosal morphology, inflammation, cell differentiation and nutrient absorption to the level of the gluten-free diet group. Nearly half of the gluten-induced gene expression changes in CeD were associated with the epithelial interferon-γ response. Moreover, data suggest that deamidated gluten-induced adaptive immunity is a sufficient step to set the stage for CeD pathogenesis. Our results, with the limited sample size, also suggest that individuals with CeD might benefit from an HLA-DQ2/HLA-DQ8 stratification based on gene doses to maximally eliminate the interferon-γ-induced mucosal damage triggered by gluten.

IFNγ induces epithelial reprogramming driving CXCL11-mediated T cell migration

The cytokine interferon-gamma (IFNγ) plays a multifaceted role in intestinal immune responses ranging from anti-to pro-inflammatory depending on the setting. Here, using a 3D co-culture system based on human intestinal epithelial organoids, we explore the capacity of IFNγ-exposure to reprogram intestinal epithelia and thereby directly modulate lymphocyte responses. IFNγ treatment of organoids led to transcriptional reprogramming, marked by a switch to a pro-inflammatory gene expression profile, including transcriptional upregulation of the chemokines CXCL9, CXCL10, and CXCL11. Proteomic analysis of organoid-conditioned medium post-treatment confirmed chemokine secretion. Furthermore, IFNγ-treatment of organoids led to enhanced T cell migration in a CXCL11-dependent manner without affecting T cell activation status. Taken together, our results suggest a specific role for CXCL11 in T cell recruitment that can be targeted to prevent T cell trafficking to the inflamed intestine.

Evaluating the Effects of Chronic Oral Exposure to the Food Additive Silicon Dioxide on Oral Tolerance Induction and Food Sensitivities in Mice

BACKGROUND

The increasing prevalence of food sensitivities has been attributed to changes in gut microenvironment; however, ubiquitous environmental triggers such as inorganic nanoparticles (NPs) used as food additives have not been thoroughly investigated.

OBJECTIVES

We explored the impact of the NP-structured food-grade silicon dioxide (f g - SiO 2 ) on intestinal immune response involved in oral tolerance (OT) induction and evaluated the consequences of oral chronic exposure to this food-additive using a mouse model of OT to ovalbumin (OVA) and on gluten immunopathology in mice expressing the celiac disease risk gene, HLA-DQ8.

METHODS

Viability, proliferation, and cytokine production of mesenteric lymph node (MLN) cells were evaluated after exposure to f g - SiO 2 . C57BL/6J mice and a mouse model of OT to OVA were orally exposed to f g - SiO 2 or vehicle for 60 d. Fecal lipocalin-2 (Lcn-2), anti-OVA IgG, cytokine production, and immune cell populations were analyzed. Nonobese diabetic (NOD) mice expressing HLA-DQ8 (NOD/DQ8), exposed to f g - SiO 2 or vehicle, were immunized with gluten and immunopathology was investigated.

RESULTS

MLN cells exposed to f g - SiO 2 presented less proliferative T cells and lower secretion of interleukin 10 (IL-10) and transforming growth factor beta (TGF- β ) by T regulatory and CD 45 + CD 11 b + CD 103 + cells compared to control, two factors mediating OT. Mice given f g - SiO 2 exhibited intestinal Lcn-2 level and interferon gamma (IFN- γ ) secretion, showing inflammation and less production of IL-10 and TGF- β . These effects were also observed in OVA-tolerized mice exposed to f g - SiO 2 , in addition to a breakdown of OT and a lower intestinal frequency of T cells. In NOD/DQ8 mice immunized with gluten, the villus-to-crypt ratio was decreased while the CD 3 + intraepithelial lymphocyte counts and the Th1 inflammatory response were aggravated after f g - SiO 2 treatment.

DISCUSSION

Our results suggest that chronic oral exposure to f g - SiO 2 blocked oral tolerance induction to OVA, and worsened gluten-induced immunopathology in NOD/DQ8 mice. The results should prompt investigation on the link between SiO 2 exposure and food sensitivities in humans. https://doi.org/10.1289/EHP12758.

HK3 stimulates immune cell infiltration to promote glioma deterioration

BACKGROUND

Glioma is the most common and lethal type of brain tumor, and it is characterized by unfavorable prognosis and high recurrence rates. The reprogramming of energy metabolism and an immunosuppressive tumor microenvironment (TME) are two hallmarks of tumors. Complex and dynamic interactions between neoplastic cells and the surrounding microenvironment can generate an immunosuppressive TME, which can accelerate the malignant progression of glioma. Therefore, it is crucial to explore associations between energy metabolism and the immunosuppressive TME and to identify new biomarkers for glioma prognosis.

METHODS

In our work, we analyzed the co-expression relationship between glycolytic genes and immune checkpoints based on the transcriptomic data from The Cancer Genome Atlas (TCGA) and Chinese Glioma Genome Atlas (CGGA) and found the correlation between HK3 expression and glioma tumor immune status. To investigate the biological role of HK3 in glioma, we performed bioinformatics analysis and established a mouse glioblastoma (GBM) xenograft model.

RESULTS

Our study showed that HK3 significantly stimulated immune cell infiltration into the glioma TME. Tissue samples with higher HK3 expressive level showed increasing levels of immune cells infiltration, including M2 macrophages, neutrophils, and various subtypes of activated memory CD4+ T cells. Furthermore, HK3 expression was significantly increasing along with the elevated tumor grade, had a higher level in the mesenchymal subtype compared with those in other subtypes of GBM and could independently predict poor outcomes of GBM patients.

CONCLUSION

The present work mainly concentrated on the biological role of HK3 in glioma and offered a novel insight of HK3 regulating the activation of immune cells in the glioma microenvironment. These findings could provide a new theoretical evidence for understanding the metabolic molecular within the glioma microenvironment and identifying new therapeutic targets.

RNA-Sequencing Reveals Gene Expression and Pathway Signatures in Umbilical Cord Blood Affected by Birth Delivery Mode

Cesarean section (CS) confers increased risk of type I diabetes, asthma, inflammatory bowel disease, celiac disease, overweight and obesity, etc., in the offspring. However, the underlying mechanism remains unknown. To investigate the influence of CS on gene expression in cord blood, we have performed RNA-sequencing followed by single-gene analysis, gene set enrichment analysis, gene co-expression network analysis, and interacting genes/proteins analysis in eight full-term infants born by elective CS and eight matched vaginally delivered (VD) infants. Crucial genes identified above were further validated in another 20 CS and 20 VD infants. We found for the first time that mRNA expression of genes involved in immune response (IL12A, INFG, IL1B, TNF, MIF, IL4, CA1, IFI27, HLA-DOB and EPHB1) and metabolism (DLK1, CYP2A6 and GATM) were significantly influenced by CS. Notably, serum TNF-α and IFN-γ were remarkably up-regulated in the CS infants (p = 5.0 × 10-4 and 3.0 × 10-3, respectively) compared to the VD infants. It is biologically plausible that CS may exert adverse impacts on offspring health through influencing expression of genes in the above processes. These findings will help understand the potential underlying mechanisms of the adverse health impacts of CS and identify biomarkers for future health of offspring born with different delivery modes.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43657-022-00086-7.

Gene Expression Profiling in Coeliac Disease Confirmed the Key Role of the Immune System and Revealed a Molecular Overlap with Non-Celiac Gluten Sensitivity

Coeliac disease (CeD) is an immune-mediated disorder triggered by the ingestion of gluten and an as yet unidentified environmental factor in genetically predisposed individuals. The disease involves a major autoimmune component that primarily damages the intestinal mucosa; although, it also has systemic involvement. The Th1 inflammatory response is one of the main events leading to mucosal damage; although, enterocytes and the innate immune response also participate in the pathological mechanism. In this study, we performed an analysis of the gene expression profile of the intestinal mucosa of patients with active disease and compared it with that of patients who do not suffer from gluten-related disorders but report dyspeptic symptoms. This analysis identified 1781 differentially expressed (DE) genes, of which 872 were downregulated and 909 upregulated. Gene Ontology and pathway analysis indicated that the innate and adaptive immune response, in particular the Th1 pathway, are important pathogenetic mechanisms of CeD, while the key cytokines are IL27, IL21, IL2, IL1b, TNF, CSF2 and IL7, as well as type I (IFNA1, IFNA2) and type II (IFNG) interferons. Finally, the comparison between the DE genes identified in this study and those identified in our previous study in the intestinal mucosa of patients with non-celiac gluten sensitivity (NCGS) revealed a high degree of molecular overlap. About 30% of the genes dysregulated in NCGS, most of which are long non-coding RNAs, are also altered in CeD suggesting that these diseases may have a common root (dysregulated long non-coding RNAs) from which they develop towards an inflammatory phenotype of variable degree in the case of CeD and NCGS respectively.

Single cell transcriptomic analysis of the immune cell compartment in the human small intestine and in Celiac disease

Celiac disease is an autoimmune disorder in which ingestion of dietary gluten triggers an immune reaction in the small intestine leading to destruction of the lining epithelium. Current treatment focusses on lifelong adherence to a gluten-free diet. Gluten-specific CD4⁺ T cells and cytotoxic intraepithelial CD8⁺ T cells have been proposed to be central in disease pathogenesis. Here we use unbiased single-cell RNA-sequencing and explore the heterogeneity of CD45⁺ immune cells in the human small intestine. We show altered myeloid cell transcriptomes present in active celiac lesions. CD4⁺ and CD8⁺ T cells transcriptomes show extensive changes and we define a natural intraepithelial lymphocyte population that is reduced in celiac disease. We show that the immune landscape in Celiac patients on a gluten-free diet is only partially restored compared to control samples. Altogether, we provide a single cell transcriptomic resource that can inform the immune landscape of the small intestine during Celiac disease.

Celiac disease is linked to responsiveness to dietary gluten, which manifests itself as immune cell activation and the immunopathology including destruction of the epithelium of the small intestine. Here the authors apply single cell transcriptomics to characterise the immune cell compartment of the human small intestine during active Celiac disease.

Pathophysiology and immunogenetics of celiac disease

Celiac disease (CD) is a chronic inflammatory enteropathy caused by gluten (protein from wheat, rye and, barley) in genetically predisposed individuals carrying the HLA-DQ2/HLA-DQ8 genotype. This pathology has a multifactorial etiology in which HLA genes, the microbiome, gluten and, other environmental factors are involved in the development of the disease. Its pathogenesis involves both innate and adaptive immunity as well as upregulation of IL-15. The objective of this review is to examine the results of current studies on genetic and environmental variables to better understand the pathogenesis of this enteropathy. The complex etiology of celiac disease makes our understanding of the pathogenesis of the disease incomplete, and a better knowledge of the many genetic and environmental components would help us better understand the pathophysiology of celiac disease.

Deciphering the Transcriptomic Heterogeneity of Duodenal Coeliac Disease Biopsies

Coeliac disease (CD) is a clinically heterogeneous autoimmune disease with variable presentation and progression triggered by gluten intake. Molecular or genetic factors contribute to disease heterogeneity, but the reasons for different outcomes are poorly understood. Transcriptome studies of tissue biopsies from CD patients are scarce. Here, we present a high-resolution analysis of the transcriptomes extracted from duodenal biopsies of 24 children and adolescents with active CD and 21 individuals without CD but with intestinal afflictions as controls. The transcriptomes of CD patients divide into three groups-a mixed group presenting the control cases, and CD-low and CD-high groups referring to lower and higher levels of CD severity. Persistence of symptoms was weakly associated with subgroup, but the highest marsh stages were present in subgroup CD-high, together with the highest cell cycle rates as an indicator of virtually complete villous atrophy. Considerable variation in inflammation-level between subgroups was further deciphered into immune cell types using cell type de-convolution. Self-organizing maps portrayal was applied to provide high-resolution landscapes of the CD-transcriptome. We find asymmetric patterns of miRNA and long non-coding RNA and discuss the effect of epigenetic regulation. Expression of genes involved in interferon gamma signaling represent suitable markers to distinguish CD from non-CD cases. Multiple pathways overlay in CD biopsies in different ways, giving rise to heterogeneous transcriptional patterns, which potentially provide information about etiology and the course of the disease.

Systematic Prioritization of Candidate Genes in Disease Loci Identifies TRAFD1 as a Master Regulator of IFNγ Signaling in Celiac Disease

Celiac disease (CeD) is a complex T cell-mediated enteropathy induced by gluten. Although genome-wide association studies have identified numerous genomic regions associated with CeD, it is difficult to accurately pinpoint which genes in these loci are most likely to cause CeD. We used four different in silico approaches-Mendelian randomization inverse variance weighting, COLOC, LD overlap, and DEPICT-to integrate information gathered from a large transcriptomics dataset. This identified 118 prioritized genes across 50 CeD-associated regions. Co-expression and pathway analysis of these genes indicated an association with adaptive and innate cytokine signaling and T cell activation pathways. Fifty-one of these genes are targets of known drug compounds or likely druggable genes, suggesting that our methods can be used to pinpoint potential therapeutic targets. In addition, we detected 172 gene combinations that were affected by our CeD-prioritized genes in trans. Notably, 41 of these trans-mediated genes appear to be under control of one master regulator, TRAF-type zinc finger domain containing 1 (TRAFD1), and were found to be involved in interferon (IFN)γ signaling and MHC I antigen processing/presentation. Finally, we performed in vitro experiments in a human monocytic cell line that validated the role of TRAFD1 as an immune regulator acting in trans. Our strategy confirmed the role of adaptive immunity in CeD and revealed a genetic link between CeD and IFNγ signaling as well as with MHC I antigen processing, both major players of immune activation and CeD pathogenesis.

Oxidative stress, DNA stability and evoked inflammatory signaling in young celiac patients consuming a gluten-free diet

PURPOSE

Celiac disease (CD) is a multifactorial, autoimmune, gluten-sensitive inflammatory disorder of the small intestine. Taking into account the pathogenesis of CD, a strict gluten-free diet (GFD) is the only treatment able to restore epithelium integrity and eliminate complications. The current study was designed to assess whether the use of a GFD is sufficient for maintaining a correct oxidative/antioxidant balance and ameliorating the evoked inflammatory signaling in young patients with CD.

METHODS

The study covered 80 children, aged between 7 and 18 years, attending the Gastroenterology Service of the Gastroenterology, Hepatology and Child Nutrition Service from the Virgen de las Nieves Hospital in Granada. Children with CD diagnosed were included in the celiac group who followed a strict GFD for 2 years (n = 40) and the control group (n = 40) included healthy children, with negative serological screening. Soluble superoxide dismutase 1 and 2, total antioxidant status, 8-hydroxy-2'-deoxyguanosine, cortisol, melatonin and inflammatory parameters in plasma, 15-F2t-isoprostanes in urine, and DNA breaks in peripheral blood lymphocytes were analysed.

RESULTS

No differences were found in oxidative stress between CD patients and controls; however, IFN-γ, IL-1α, IP-10 and TNF-β were higher in the CD patients. VEGF was also higher than in the control group.

CONCLUSION

The GFD in the CD patients is enough to reduce the oxidative stress; however, in the case of the inflammatory signaling, the initial exposure to gluten prior to stablish the GFD is strong enough to induce an inflammatory state which is maintained (even when consuming the GFD); meanwhile the increase in VEGF recorded in the CD group could be a compensatory mechanism to restore the damaged mucosa and duodenal villous atrophy, due to its role in endothelial activation and generation of new functional and stable vascular networks.

IL-10 signaling prevents gluten-dependent intraepithelial CD4+ cytotoxic T lymphocyte infiltration and epithelial damage in the small intestine

Breach of tolerance to gluten leads to the chronic small intestinal enteropathy celiac disease. A key event in celiac disease development is gluten-dependent infiltration of activated cytotoxic intraepithelial lymphocytes (IELs), which cytolyze epithelial cells causing crypt hyperplasia and villous atrophy. The mechanisms leading to gluten-dependent small intestinal IEL infiltration and activation remain elusive. We have demonstrated that under homeostatic conditions in mice, gluten drives the differentiation of anti-inflammatory T cells producing large amounts of the immunosuppressive cytokine interleukin-10 (IL-10). Here we addressed whether this dominant IL-10 axis prevents gluten-dependent infiltration of activated cytotoxic IEL and subsequent small intestinal enteropathy. We demonstrate that IL-10 regulation prevents gluten-induced cytotoxic inflammatory IEL infiltration. In particular, IL-10 suppresses gluten-induced accumulation of a specialized population of cytotoxic CD4⁺CD8αα⁺ IEL (CD4⁺ CTL) expressing Tbx21, Ifng, and Il21, and a disparate non-cytolytic CD4⁺CD8α^- IEL population expressing Il17a, Il21, and Il10. Concomitantly, IL-10 suppresses gluten-dependent small intestinal epithelial hyperproliferation and upregulation of stress-induced molecules on epithelial cells. Remarkably, frequencies of granzyme B⁺CD4⁺CD8α⁺ IEL are increased in pediatric celiac disease patient biopsies. These findings demonstrate that IL-10 is pivotal to prevent gluten-induced small intestinal inflammation and epithelial damage, and imply that CD4⁺ CTL are potential new players into these processes.

Celiac disease biomarkers identified by transcriptome analysis of small intestinal biopsies

Establishing a celiac disease (CD) diagnosis can be difficult, such as when CD-specific antibody levels are just above cutoff or when small intestinal biopsies show low-grade injuries. To investigate the biological pathways involved in CD and select potential biomarkers to aid in CD diagnosis, RNA sequencing of duodenal biopsies from subjects with either confirmed Active CD (n = 20) or without any signs of CD (n = 20) was performed. Gene enrichment and pathway analysis highlighted contexts, such as immune response, microbial infection, phagocytosis, intestinal barrier function, metabolism, and transportation. Twenty-nine potential CD biomarkers were selected based on differential expression and biological context. The biomarkers were validated by real-time polymerase chain reaction of eight RNA sequencing study subjects, and further investigated using an independent study group (n = 43) consisting of subjects not affected by CD, with a clear diagnosis of CD on either a gluten-containing or a gluten-free diet, or with low-grade intestinal injury. Selected biomarkers were able to classify subjects with clear CD/non-CD status, and a subset of the biomarkers (CXCL10, GBP5, IFI27, IFNG, and UBD) showed differential expression in biopsies from subjects with no or low-grade intestinal injury that received a CD diagnosis based on biopsies taken at a later time point. A large number of pathways are involved in CD pathogenesis, and gene expression is affected in CD mucosa already in low-grade intestinal injuries. RNA sequencing of low-grade intestinal injuries might discover pathways and biomarkers involved in early stages of CD pathogenesis.

Altered transcription of inflammation-related genes in dental pulp of coeliac children

BACKGROUND

Coeliac disease is a chronic small intestinal immune-mediated enteropathy precipitated by exposure to dietary gluten, and possible relationships between coeliac disease and dental pathogenic conditions during childhood have been poorly investigated.

AIM

The dental pulp plays a pivotal role in the immune defence against possible entry of pathogens from teeth, and the aim of this work was to investigate quantitative transcription levels of selected genes (IL-9, IL-11, IL-15, IL-18, IL-21, IL-27, MICA, IFN-γ) coding for pro-inflammatory immune innate activities in the pulp of primary teeth from healthy children and children with coeliac disease.

DESIGN

The pulp from primary teeth of 10 healthy children and 10 children with coeliac disease was used to extract RNA and prepare cDNA for quantitative PCR transcription analysis employing commercial nucleotide probes for selected genes.

RESULTS

In children with coeliac disease, the genes coding for pro-inflammatory cytokines IFN-γ, IL-11, IL-18, and IL-21 were significantly overexpressed, suggesting the possible importance of these cytokines in the relationships between coeliac disease and dental disorders.

CONCLUSION

For the first time, we reported in dental pulp of children possible relationships between coeliac disease and modulation in transcription of cytokine-dependent inflammatory activities.

Transcriptome Analysis of CD4+ T Cells in Coeliac Disease Reveals Imprint of BACH2 and IFNγ Regulation

Genetic studies have to date identified 43 genome wide significant coeliac disease susceptibility (CD) loci comprising over 70 candidate genes. However, how altered regulation of such disease associated genes contributes to CD pathogenesis remains to be elucidated. Recently there has been considerable emphasis on characterising cell type specific and stimulus dependent genetic variants. Therefore in this study we used RNA sequencing to profile over 70 transcriptomes of CD4+ T cells, a cell type crucial for CD pathogenesis, in both stimulated and resting samples from individuals with CD and unaffected controls. We identified extensive transcriptional changes across all conditions, with the previously established CD gene IFNy the most strongly up-regulated gene (log2 fold change 4.6; P_adjusted = 2.40x10^-11) in CD4+ T cells from CD patients compared to controls. We show a significant correlation of differentially expressed genes with genetic studies of the disease to date (P_adjusted = 0.002), and 21 CD candidate susceptibility genes are differentially expressed under one or more of the conditions used in this study. Pathway analysis revealed significant enrichment of immune related processes. Co-expression network analysis identified several modules of coordinately expressed CD genes. Two modules were particularly highly enriched for differentially expressed genes (P<2.2x10^-16) and highlighted IFNy and the genetically associated transcription factor BACH2 which showed significantly reduced expression in coeliac samples (log2FC -1.75; P_adjusted = 3.6x10^-3) as key regulatory genes in CD. Genes regulated by BACH2 were very significantly over-represented among our differentially expressed genes (P<2.2x10^-16) indicating that reduced expression of this master regulator of T cell differentiation promotes a pro-inflammatory response and strongly corroborates genetic evidence that BACH2 plays an important role in CD pathogenesis.

Systematic annotation of celiac disease loci refines pathological pathways and suggests a genetic explanation for increased interferon-gamma levels

Although genome-wide association studies and fine mapping have identified 39 non-HLA loci associated with celiac disease (CD), it is difficult to pinpoint the functional variants and susceptibility genes in these loci. We applied integrative approaches to annotate and prioritize functional single nucleotide polymorphisms (SNPs), genes and pathways affected in CD. CD-associated SNPs were intersected with regulatory elements categorized by the ENCODE project to prioritize functional variants, while results from cis-expression quantitative trait loci (eQTL) mapping in 1469 blood samples were combined with co-expression analyses to prioritize causative genes. To identify the key cell types involved in CD, we performed pathway analysis on RNA-sequencing data from different immune cell populations and on publicly available expression data on non-immune tissues. We discovered that CD SNPs are significantly enriched in B-cell-specific enhancer regions, suggesting that, besides T-cell processes, B-cell responses play a major role in CD. By combining eQTL and co-expression analyses, we prioritized 43 susceptibility genes in 36 loci. Pathway and tissue-specific expression analyses on these genes suggested enrichment of CD genes in the Th1, Th2 and Th17 pathways, but also predicted a role for four genes in the intestinal barrier function. We also discovered an intricate transcriptional connectivity between CD susceptibility genes and interferon-γ, a key effector in CD, despite the absence of CD-associated SNPs in the IFNG locus. Using systems biology, we prioritized the CD-associated functional SNPs and genes. By highlighting a role for B cells in CD, which classically has been described as a T-cell-driven disease, we offer new insights into the mechanisms and pathways underlying CD.

Molecular mechanisms of the adaptive, innate and regulatory immune responses in the intestinal mucosa of celiac disease patients

Celiac disease is a complex genetic disorder that affects the small intestine of genetically predisposed individuals when they ingest gluten, a dietary protein. Although several genome screens have been successful in identifying susceptibility loci in celiac disease, the only genetic contributors identified so far are the human leukocyte antigen (HLA)-DQ2/DQ8 molecules. One of the most important aspects in the pathogenesis of celiac disease is the activation of a T-helper 1 immune response, when the antigen-presenting cells that express HLA-DQ2/DQ8 molecules present the toxic gluten peptides to reactive CD4(+) T-cells. Recently, new insights into the activation of an innate immune response have also been described. It is generally accepted that the immune response triggers destruction of the mucosa in the small intestine of celiac disease patients. Hence, the activation of a detrimental immune response in the intestine of celiac disease patients appears to be key in the initiation and progression of the disease. This review summarizes the immunologic pathways that have been studied in celiac disease thus far, and will point to new potential candidate genes and pathways involved in the etiopathogenesis of celiac disease, which should lead to novel alternatives for diagnosis and treatment.

Mucosal cytokine response after short-term gluten challenge in celiac disease and non-celiac gluten sensitivity

OBJECTIVES

In celiac disease (CD), gluten induces both adaptive and innate immune responses. Non-celiac gluten sensitivity (NCGS) is another form of gluten intolerance where the immune response is less characterized. The aim of our study was to explore and compare the early mucosal immunological events in CD and NCGS.

METHODS

We challenged 30 HLA-DQ2(+) NCGS and 15 CD patients, all on a gluten-free diet, with four slices of gluten-containing bread daily for 3 days. Duodenal biopsy specimens were collected before and after challenge. The specimens were examined for cytokine mRNA by quantitative reverse transcriptase-PCR and for MxA-expression and CD3(+) intraepithelial lymphocytes (IELs) by immunohistochemistry and compared with specimens from untreated CD patients and disease controls.

RESULTS

In CD patients, tumor necrosis factor alpha (P=0.02) and interleukin 8 (P=0.002) mRNA increased after in vivo gluten challenge. The interferon gamma (IFN-γ) level of treated CD patients was high both before and after challenge and did not increase significantly (P=0.06). Four IFN-γ-related genes increased significantly. Treated and untreated CD patients had comparable levels of IFN-γ. Increased expression of MxA in treated CD patients after challenge suggested that IFN-α was activated on gluten challenge. In NCGS patients only IFN-γ increased significantly (P=0.03). mRNA for heat shock protein (Hsp) 27 or Hsp70 did not change in any of the groups. Importantly, we found that the density of IELs was higher in NCGS patients compared with disease controls, independent of challenge, although lower than the level for treated CD patients.

CONCLUSIONS

CD patients mounted a concomitant innate and adaptive immune response to gluten challenge. NCGS patients had increased density of intraepithelial CD3(+) T cells before challenge compared with disease controls and increased IFN-γ mRNA after challenge. Our results warrant further search for the pathogenic mechanisms for NCGS.

Differential IL-13 production by small intestinal leukocytes in active coeliac disease versus refractory coeliac disease

A small fraction of coeliac disease (CD) patients have persistent villous atrophy despite strict adherence to a gluten-free diet. Some of these refractory CD (RCD) patients develop a clonal expansion of lymphocytes with an aberrant phenotype, referred to as RCD type II (RCDII). Pathogenesis of active CD (ACD) has been shown to be related to gluten-specific immunity whereas the disease is no longer gluten driven in RCD. We therefore hypothesized that the immune response is differentially regulated by cytokines in ACD versus RCDII and investigated mucosal cytokine release after polyclonal stimulation of isolated mucosal lymphocytes. Secretion of the T_H2 cytokine IL-13 was significantly higher in lamina propria leukocytes (LPLs) isolated from RCDII patients as compared to LPL from ACD patients (P = 0.05). In patients successfully treated with a gluten-free diet LPL-derived IL-13 production was also higher as compared to ACD patients (P = 0.02). IL-13 secretion correlated with other T_H2 as well as T_H1 cytokines but not with IL-10 secretion. Overall, the cytokine production pattern of LPL in RCDII showed more similarities with LPL isolated from GFD patients than from ACD patients. Our data suggest that different immunological processes are involved in RCDII and ACD with a potential role for IL-13.

The effect of gluten-free diet on Th1-Th2-Th3-associated intestinal immune responses in celiac disease

OBJECTIVE

To study T-helper (Th)1-Th2-Th3 gene activation profile in the small intestine and peripheral blood of children with celiac disease (CD) with special interest in the response to the gluten-free diet (GFD) treatment in order to elucidate an immune dysregulation not triggered by gluten.

MATERIAL AND METHODS

Small intestinal biopsies and venous blood were taken from seven children with CD (mean age: 8 years, four girls) at presentation and after 1 year of strict GFD. The Th1-Th2-Th3 gene expression profile was examined by real-time PCR arrays. The findings were compared with the corresponding expressions in peripheral blood and small intestinal biopsies from six reference children without CD (mean age: 6 years, four girls).

RESULTS

The Th1 gene expression profile including interferon (IFN)-γ, signal transducer and activator of transcription (STAT) 1 and interferon regulatory factor (IRF) 1 together with reduced interleukin (IL)-2 expression was pronounced in small intestinal biopsies from children with untreated CD. A downregulation of IFN-γ transcripts was seen after 1 year of GFD, but there was still increased expression of STAT1 and IRF1 in association with low IL-2 expression in spite of eliminated exposure to wheat gluten. By contrast, the decreased intestinal expression of Th2 gene markers observed at presentation was normalized with GFD. The alterations in the mucosal gene expression profile were not reflected in peripheral blood.

CONCLUSION

The GFD did not correct the increased activation of the IFN-γ signaling pathway related markers and reduced IL-2 expression, suggesting that they represent an immune dysregulation not dependent on gluten exposure.

HLA-G 14 bp deletion/insertion polymorphism in celiac disease

OBJECTIVES

Nonclassical major histocompatibility class I HLA-G antigen is a tolerogenic molecule that inhibits lytic activity of natural killer (NK) cells and cytotoxic T lymphocytes. Because of its immunomodulatory and tolerogenic properties, HLA-G molecules may have a role in celiac disease (CD). We analyzed the HLA-G 14 bp deletion/insertion polymorphism, known to have a functional effect on mRNA stability, in a group of 522 CD patients, stratified for the presence of HLA-DQ2 genotype, and 400 healthy individuals to evaluate the possible effect of the polymorphism on the risk to develop the disease.

METHODS

HLA-G 14 bp deletion/insertion polymorphism (rs1704) was detected by polymerase chain reaction and double-checked by direct sequencing.

RESULTS

The 14 bp inserted (I) allele and the homozygous I/I genotype were significantly more frequent in CD patients than in healthy controls. The presence of I allele was associated with an increased risk of CD (OR 1.35) and the effect of I allele was consistent with a recessive genetic model (P<0.001).

CONCLUSIONS

Our results also indicate that the effect of the HLA-G D/I polymorphism is restricted for HLA-DQ2, and not simply due to the presence of linkage disequilibrium with the major known risk factor; moreover we found that the presence of the I allele confers an increased risk of CD in addition to the risk conferred by HLA-DQ2 alone and that subjects that carry both DQ2 and HLA-G I alleles have an increased risk of CD than subjects that carry DQ2 but not the I allele.

Functional microorganisms for functional food quality

Functional microorganisms and health benefits represent a binomial with great potential for fermented functional foods. The health benefits of fermented functional foods are expressed either directly through the interactions of ingested live microorganisms with the host (probiotic effect) or indirectly as the result of the ingestion of microbial metabolites synthesized during fermentation (biogenic effect). Since the importance of high viability for probiotic effect, two major options are currently pursued for improving it--to enhance bacterial stress response and to use alternative products for incorporating probiotics (e.g., ice cream, cheeses, cereals, fruit juices, vegetables, and soy beans). Further, it seems that quorum sensing signal molecules released by probiotics may interact with human epithelial cells from intestine thus modulating several physiological functions. Under optimal processing conditions, functional microorganisms contribute to food functionality through their enzyme portfolio and the release of metabolites. Overproduction of free amino acids and vitamins are two classical examples. Besides, bioactive compounds (e.g., peptides, γ-amino butyric acid, and conjugated linoleic acid) may be released during food processing above the physiological threshold and they may exert various in vivo health benefits. Functional microorganisms are even more used in novel strategies for decreasing phenomenon of food intolerance (e.g., gluten intolerance) and allergy. By a critical approach, this review will aim at showing the potential of functional microorganisms for the quality of functional foods.

Serum cytokine elevations in celiac disease: association with disease presentation

Celiac disease (CD) is an autoimmune disorder that is triggered by an immune response to gluten in genetically predisposed individuals. Although considered a primary gastrointestinal disease, CD is now known to have widespread systemic manifestations. We attempted to define the nature and role of systemic cytokine levels in the pathophysiology of CD. Multiplex cytokine assays were performed on four different groups of adult patients; patients with active CD (ACD), patients on a gluten-free diet (GFD) with positive TTG IgA antibodies, patients on a GFD with negative antibodies, and those with refractory CD (RCD). The results were compared with values in healthy adult controls. Patients with active CD and those on GFD with positive antibodies had significantly higher levels of proinflammatory cytokines, such as interferon-gamma, interleukin (IL)-1beta, tumor necrosis factor-alpha, IL-6 and IL-8, and also T(h)-2 cytokines such as IL-4 and IL-10, compared with normal controls and patients on GFD without antibodies. Interestingly patients on GFD for less than 1 year had significantly higher levels of both proinflammatory cytokines and T(h)2 cytokines compared with the patients on GFD for more than 1 year. In addition, a statistically significant correlation between levels of TTG IgA titers and serum levels of T(h)-2 cytokines IL-4 (p < 0.001), IL-10 (p < 0.001) and inflammatory cytokines such as IL-1alpha (p < 0.001), IL-1beta (p < 0.005), and IL-8 (p < 0.05) was observed.

Noninflammatory gluten peptide analogs as biomarkers for celiac sprue

New tools are needed for managing celiac sprue, a lifelong immune disease of the small intestine. Ongoing drug trials are also prompting a search for noninvasive biomarkers of gluten-induced intestinal change. We have synthesized and characterized noninflammatory gluten peptide analogs in which key Gln residues are replaced by Asn or His. Like their proinflammatory counterparts, these biomarkers are resistant to gastrointestinal proteases, susceptible to glutenases, and permeable across enterocyte barriers. Unlike gluten peptides, however, they are not appreciably recognized by transglutaminase, HLA-DQ2, or disease-specific T cells. In vitro and animal studies show that the biomarkers can detect intestinal permeability changes as well as glutenase-catalyzed gastric detoxification of gluten. Accordingly, controlled clinical studies are warranted to evaluate the use of these peptides as probes for abnormal intestinal permeability in celiac patients and for glutenase efficacy in clinical trials and practice.

Mechanism of degradation of immunogenic gluten epitopes from Triticum turgidum L. var. durum by sourdough lactobacilli and fungal proteases

As shown by R5 antibody-based sandwich and competitive enzyme-linked immunosorbent assay (ELISA), selected sourdough lactobacilli, in combination with fungal proteases, hydrolyzed gluten (72 h at 37 degrees C) of various cultivars of Triticum turgidum L. var. durum to less than 20 ppm. Complementary electrophoretic, chromatography, and mass spectrometry techniques were used to characterize the gluten and epitope hydrolysis. Nine peptidases were partially purified from the pooled cytoplasmic extract of the sourdough lactobacilli and used to hydrolyze the 33-mer epitope, the most immunogenic peptide generated during digestion of Triticum species. At least three peptidases (general aminopeptidase type N [PepN], X-prolyl dipeptidyl aminopeptidase [PepX], and endopeptidase PepO) were necessary to detoxify the 33-mer without generation of related immunogenic epitopes. After 14 h of incubation, the combination of all or at least six different peptidases totally hydrolyzed the 33-mer (200 mM) into free amino acids. The same results were found for other immunogenic epitopes, such as fragments 57-68 of alpha 9-gliadin, 62-75 of A-gliadin, and 134-153 of gamma-gliadin. When peptidases were used for fermentation of durum wheat semolina, they caused the hydrolysis of gluten to ca. 2 ppm. The in vivo digestion was simulated, and proteins/peptides extracted from pepsin-trypsin (PT) digestion of durum wheat semolina fermented with selected sourdough lactobacilli induced the expression of gamma interferon and interleukin 2 at levels comparable to those of the negative control. Durum wheat semolina fermented with sourdough lactobacilli was freeze-dried and used for making Italian-type pasta. The scores for cooking and sensory properties for this pasta were higher that those of conventional gluten-free pasta.

Interferon-gamma released by gluten-stimulated celiac disease-specific intestinal T cells enhances the transepithelial flux of gluten peptides

Celiac sprue is a T-cell-mediated enteropathy elicited in genetically susceptible individuals by dietary gluten proteins. To initiate and propagate inflammation, proteolytically resistant gluten peptides must be translocated across the small intestinal epithelium and presented to DQ2-restricted T cells, but the effectors enabling this translocation under normal and inflammatory conditions are not well understood. We demonstrate that a fluorescently labeled antigenic 33-mer gluten peptide is translocated intact across a T84 cultured epithelial cell monolayer and that preincubation of the monolayer with media from gluten-stimulated, celiac patient-derived intestinal T cells enhances the apical-to-basolateral flux of this peptide in a dose-dependent, saturable manner. The permeability-enhancing activity of activated T-cell media is inhibited by blocking antibodies against either interferon-gamma or its receptor and is recapitulated using recombinant interferon-gamma. At saturating levels of interferon-gamma, activated T-cell media does not further increase transepithelial peptide flux, indicating the primacy of interferon-gamma as an effector of increased epithelial permeability during inflammation. Reducing the assay temperature to 4 degrees C reverses the effect of interferon-gamma but does not reduce basal peptide flux occurring in the absence of interferon-gamma, suggesting active transcellular transport of intact peptides is increased during inflammation. A panel of disease-relevant gluten peptides exhibited an inverse correlation between size and transepithelial flux but no apparent sequence constraints. Anti-interferon-gamma therapy may mitigate the vicious cycle of gluten-induced interferon-gamma secretion and interferon-gamma-mediated enhancement of gluten peptide flux but is unlikely to prevent translocation of gluten peptides in the absence of inflammatory conditions.

Correlating blood immune parameters and a CCT7 genetic variant with the shedding of Salmonella enterica serovar Typhimurium in swine

The porcine response to Salmonella infection is critical for control of Salmonella fecal shedding and the establishment of Salmonella carrier status. In this study, 40 crossbred pigs were intranasally inoculated with Salmonella enterica serovar Typhimurium (Salmonella Typhimurium) and monitored for Salmonella fecal shedding and blood immune parameters at 2, 7, 14 and 20 days post-inoculation (dpi). Using a multivariate permutation test, a positive correlation was observed between Salmonella Typhimurium shedding levels at 2 and 7dpi and serum interferon-gamma (IFNgamma) levels at 2dpi (p<0.05), with Salmonella being shed in greater numbers from animals with higher IFNgamma levels. A positive correlation was also observed between IFNgamma levels and the number of banded neutrophils (2dpi), circulating neutrophils (7 and 14dpi), monocytes (7dpi), and white blood cells (WBCs) (7, 14 and 20dpi). We have further performed association studies on these immune response parameters as well as shedding status of the Salmonella-infected pigs with a single nucleotide polymorphism (SNP) in the porcine gene CCT7, previously shown by our group to be transcriptionally up-regulated in swine experimentally inoculated with Salmonella Typhimurium. Our analyses with the 40 pigs suggest a positive association (p=0.0012) of SNP genotype A/G at position AK240296.c1153G>A of the CCT7 gene with Salmonella shedding at 7dpi compared to the G/G homozygote genotype. Linking specific genes and genetic polymorphisms with the porcine immune response to Salmonella infection and shedding may identify potential markers for carrier pigs as well as targets for disease diagnosis, intervention and prevention.

Combined functional and positional gene information for the identification of susceptibility variants in celiac disease

BACKGROUND & AIMS

Celiac disease is a complex, immune-mediated disorder of the intestinal mucosa with a strong genetic component. HLA-DQ2 is the major determinant of risk, but other minor genes, still to be identified, also are involved.

METHODS

We designed a strategy that combines gene expression profiling of intestinal biopsy specimens, linkage region information, and different bioinformatics tools for the selection of potentially regulatory single-nucleotide polymorphisms (SNPs) involved in the disease. We selected 361 SNPs from 71 genes that fulfilled stringent functional (changes in expression level) and positional criteria (located in regions that have been linked to the disease, other than HLA). These polymorphisms were genotyped in 262 celiac patients and 214 controls.

RESULTS

We detected strong evidence of association with several SNPs (the most significant were rs6747096, P = 2.38 x 10(-5); rs7040561, P = 6.55 x 10(-5); and rs458046, P = 1.35 x 10(-4)) that pinpoint novel candidate determinants of predisposition to the disease in previously identified linkage regions (eg, SERPINE2 in 2q33, and PBX3 or PPP6C in 9q34).

CONCLUSIONS

Our study shows that the combination of function and position is a valid strategy for the genetic dissection of complex traits.

Searching for genes influencing a complex disease: the case of coeliac disease

Recently, a few genes have been reported to be causative in inflammatory diseases. Still, we are waiting for the vast majority to be discovered. New tools for genotyping and statistical analysis have been developed and emphasis has been put on study design. Coeliac disease (CD) is a disorder, where prolamins in dietary wheat gluten and related proteins from rye or barley are not tolerated. It is one of the most common chronic diseases in humans exceeding a population prevalence of 1%. In this article, we will summarise what is currently known about the genetics influencing CD with the emphasis on the non-HLA genetic component. We will discuss some difficulties when searching for susceptibility genes in disorders with complex inheritance patterns.

Highly efficient gluten degradation by lactobacilli and fungal proteases during food processing: new perspectives for celiac disease

Presently, the only effective treatment for celiac disease is a life-long gluten-free diet. In this work, we used a new mixture of selected sourdough lactobacilli and fungal proteases to eliminate the toxicity of wheat flour during long-time fermentation. Immunological (R5 antibody-based sandwich and competitive enzyme-linked immunosorbent assay [ELISA] and R5 antibody-based Western blot), two-dimensional electrophoresis, and mass spectrometry (matrix-assisted laser desorption ionization-time of flight, strong-cation-exchange-liquid chromatography/capillary liquid chromatography-electrospray ionization-quadrupole-time of flight [SCX-LC/CapLC-ESI-Q-TOF], and high-pressure liquid chromatography-electrospray ionization-ion trap mass spectrometry) analyses were used to determine the gluten concentration. Assays based on the proliferation of peripheral blood mononuclear cells (PBMCs) and gamma interferon production by PBMCs and intestinal T-cell lines (iTCLs) from 12 celiac disease patients were used to determine the protein toxicity of the pepsin-trypsin digests from fermented wheat dough (sourdough). As determined by R5-based sandwich and competitive ELISAs, the residual concentration of gluten in sourdough was 12 ppm. Albumins, globulins, and gliadins were completely hydrolyzed, while ca. 20% of glutenins persisted. Low-molecular-weight epitopes were not detectable by SCX-LC/CapLC-ESI-Q-TOF mass spectrometry and R5-based Western blot analyses. The kinetics of the hydrolysis of the 33-mer by lactobacilli were highly efficient. All proteins extracted from sourdough activated PBMCs and induced gamma interferon production at levels comparable to the negative control. None of the iTCLs demonstrated immunoreactivity towards pepsin-trypsin digests. Bread making was standardized to show the suitability of the detoxified wheat flour. Food processing by selected sourdough lactobacilli and fungal proteases may be considered an efficient approach to eliminate gluten toxicity.

The SPINK gene family and celiac disease susceptibility

The gene family of serine protease inhibitors of the Kazal type (SPINK) are functional and positional candidate genes for celiac disease (CD). Our aim was to assess the gut mucosal gene expression and genetic association of SPINK1, -2, -4, and -5 in the Dutch CD population. Gene expression was determined for all four SPINK genes by quantitative reverse-transcription polymerase chain reaction in duodenal biopsy samples from untreated (n=15) and diet-treated patients (n=31) and controls (n=16). Genetic association of the four SPINK genes was tested within a total of 18 haplotype tagging SNPs, one coding SNP, 310 patients, and 180 controls. The SPINK4 study cohort was further expanded to include 479 CD cases and 540 controls. SPINK4 DNA sequence analysis was performed on six members of a multigeneration CD family to detect possible point mutations or deletions. SPINK4 showed differential gene expression, which was at its highest in untreated patients and dropped sharply upon commencement of a gluten-free diet. Genetic association tests for all four SPINK genes were negative, including SPINK4 in the extended case/control cohort. No SPINK4 mutations or deletions were observed in the multigeneration CD family with linkage to chromosome 9p21-13 nor was the coding SNP disease-specific. SPINK4 exhibits CD pathology-related differential gene expression, likely derived from altered goblet cell activity. All of the four SPINK genes tested do not contribute to the genetic risk for CD in the Dutch population.

Neutrophil recruitment and barrier impairment in celiac disease: a genomic study

BACKGROUND & AIMS

Celiac disease is an enteropathy featuring villous atrophy, crypt hyperplasia, and lymphocytosis. Tissue remodeling is driven by an inflammatory reaction to gluten in genetically susceptible individuals. The adaptive pathway is considered the major immune response but recent evidence has indicated the involvement of innate immunity as well. To assess the contribution of either immune response we performed global gene expression profiling of the regenerating mucosa.

METHODS

Microarray hybridizations were performed with biopsy samples from 13 untreated patients, 31 patients on a gluten-free diet in various stages of remission, and 21 controls. Additional data were generated using low-density array and conventional quantitative reverse-transcription polymerase chain reaction, and immunohistochemistry.

RESULTS

A total of 108 differentially expressed immune-related genes were identified (50 innate, 43 adaptive, 9 both innate/adaptive, and 6 immunoregulatory). Expression levels showed a gradual change as opposed to the discrete histological transitions. In addition to details provided on the adaptive and innate immune pathways used, we observed a chronic recruitment of activated neutrophils. Neutrophil involvement was unabated in otherwise completely normalized remission patients.

CONCLUSIONS

We observed a contribution of both the innate and adaptive immune response in celiac disease pathogenesis. The discrepancy between the histological classification and the observed incremental change in immune-gene expression may have consequences for current diagnostic inclusion criteria. Enhanced neutrophil infiltration in both active and remission patients points to a genetic impairment of the intestinal barrier that may contribute to the cause rather than the consequence of celiac disease.

Human intestinal alphabeta IEL clones in celiac disease show reduced IL-10 synthesis and enhanced IL-2 production

Celiac disease is a gluten-induced T-cell mediated autoimmune process that results in the destruction of the intestinal mucosa and is associated with an expansion of CD8(+) CD103(+) TCRalphabeta intraepithelial lymphocytes (IELs) in the damaged epithelium. The role of this IEL population in the pathology is unknown. The aim of this work was to compare the cytokine profile and the cytotoxicity pattern from CD8(+) IEL clones isolated from celiac (CD) and non-celiac (NCD) biopsies. We report that the number of IL-10 producing CD clones was significantly lower (26%) than that obtained from the NCD sample (62%). Instead, IL-2 was produced by more CD (44%) than NCD clones (26%). Cytotoxicity patterns against intestinal epithelial cell lines suggest different functional subsets of CD8(+) IELs. CD clones capable of high cytotoxicity produced IL-2 whereas most cytotoxic NCD IELs produced IL-10. This clonal analysis indicates that an impaired immune regulation in celiac mucosa may be partially attributed to the low generation of regulatory CD8(+) IELs that produce IL-10.

The downstream modulator of interferon-γ, STAT1 is not genetically associated to the Dutch coeliac disease population

Coeliac disease (CD) is a complex genetic disorder. Its etiology is owing to multiple genes and environmental factors, such as gluten. The first event in the pathogenesis of CD after the ingestion of gluten is the activation of a Th1 immune response that leads to villous atrophy. Although this immune response seems crucial to the disease's development, only the HLA-DQ2/DQ8 genes have been identified as causative immune genes related to CD. Recently, the activation of the transcription factor STAT1 and changes in its expression levels have confirmed the participation of the Janus kinase-signal transducer and activator of transcription pathway in CD. Furthermore, as the STAT-1 gene is a positional candidate located in the CELIAC3 locus on chromosome 2, we speculate that alterations in this gene could be primarily responsible for the aberrant immune response that characterizes CD. Based on this functional and genetic evidence, we investigated the primary contribution of STAT-1 to CD. We performed a comprehensive genetic association study using five tag SNPs fully covering the STAT-1 gene in a Dutch cohort of 355 independent CD cases and 360 healthy controls. Neither the alleles, nor the genotypes in the case-control genetic association studies, nor the haplotype analysis showed any association to the STAT-1 gene in the Dutch CD population. Our results do not point to a primary involvement of the STAT-1 gene in the Dutch CD population.

Genetic and functional analysis of pyroglutamyl-peptidase I in coeliac disease

Coeliac disease (CD) is an enteropathy caused by an immune reaction towards wheat gluten and similar proteins from barley and rye. It was shown that some gluten peptides spontaneously form N-terminal L-pyroglutamate. This modification could potentially make gluten more resistant to proteolytic degradation within the intestine. Pyroglutamyl-peptidase I (PGPEPI) is an enzyme that hydrolytically removes the L-pyroglutamyl residues that render the modified proteins and peptides more sensitive to degradation by other proteases. Interestingly, we found that the PGPEP1 gene is located in a CD susceptibility locus. As an impaired enzyme function caused by genetic alterations might increase the amount of immunogenic gluten peptides, we conducted a comprehensive functional genomics analysis of PGPEP1, including DNA sequencing, genetic association testing, and quantifying RNA expression. We also determined the enzymatic activity of PGPEPI in duodenal biopsies. Our results uniformly indicate that PGPEP1 is not involved in the aetiology and pathology of CD.

Celiac disease--sandwiched between innate and adaptive immunity

Celiac disease (CD) patients are intolerant to gluten, proteins in wheat, and related cereals. Virtually all patients are human leukocyte antigen (HLA)-DQ2 or HLA-DQ8 positive and several studies have demonstrated that CD4 T cells specific for (modified) gluten peptides bound to these HLA-DQ molecules are found in patients but not in control subjects. These T cell responses are therefore thought to be responsible for disease development. Many immunogenic gluten peptides which may relate to the disease-inducing properties of gluten have now been identified. In addition, gluten can stimulate IL-15 production that ultimately leads to NKG2D-mediated epithelial cell killing. However, CD develops in only a minority of HLA-DQ2 and HLA-DQ8 individuals. This may be attributed to the default setting of the intestinal immune system: induction and maintenance of tolerance to dietary components and commensal flora. Although at present it is unknown why tolerance in CD is not established or broken, both environmental and genetic factors have been implicated. There is strong evidence for the existence of genes or gene variants on chromosomes 5, 6, and 19 that predispose to CD. In addition, type I interferons have been implicated in development of several autoimmune disorders, including CD. Thus, viral infection and/or tissue damage in the intestine may cause inflammation and induce protective Th1-mediated immunity leading to loss of tolerance for gluten. Once tolerance is broken, a broad gluten-reactive T cell repertoire may develop through determinant spreading. This may be a critical step toward full-blown disease.

"Coelionomics": towards understanding the molecular pathology of coeliac disease

Coeliac disease (CD) is an inflammatory disorder of the small intestine characterised by a permanent intolerance to gluten-derived peptides. When gluten-derived peptides reach the lamina propria in CD patients, they provoke specific changes in the mucosa of their small intestine. Although the susceptibility to CD is strongly determined by environmental gluten, it is clearly a common genetic disorder. Important genetic factors for CD are the HLA-DQ genes located in the MHC region on chromosome 6 [HLA-DQ2 (95%) or HLA-DQ8 ( approximately 5%) heterodimers]. So far, the only treatment for CD consists of a life-long gluten-free diet. A key question in CD is why the gluten-derived peptides are resistant to further breakdown by endogenous proteases and how, in turn, they can activate a harmful immune response in the lamina propria of genetically predisposed individuals. Four mechanisms, namely apoptosis, oxidative stress, matrix metalloproteinases and dysregulation of proliferation and differentiation, are thought to play a role in the pathophysiology of CD. Whether the genes involved in these four mechanisms play a causative role in the development of the villous atrophy or are, in fact, a consequence of the disease process is unknown. In this review we summarise these mechanisms and discuss their validity in the context of current insights derived from genetic, genomic and molecular studies. We also discuss future directions for research and the therapeutic implications for patients.

TNFalpha, IFNgamma and IL-10 gene polymorphisms in a sample of Sicilian patients with coeliac disease

BACKGROUND

Coeliac disease is associated with DQ2 and DQ8 alleles, but other genes also confer an additional genetic risk.

AIMS

Defining whether the genetic profiles of interleukin-10, tumour necrosis factor alpha and interferon gamma are associated with an increased coeliac disease risk.

PATIENTS AND METHODS

The functionally gene polymorphisms of tumour necrosis factor alpha (-308G/A), interferon gamma (+874T/A) and interleukin-10 (-1082G/A) were typed using sequence specific primer-polymerase chain reaction in 110 Sicilian coeliac disease patients and in 220 Sicilian healthy controls.

RESULTS

No differences in genotype frequencies of interleukin-10 polymorphisms were found between coeliac disease patients and healthy controls. A significant increase of -308A (p<0.033; OR: 1.72; CI: 1.27-2.33) and of +874T (p: 0.0045; OR: 3.02; CI: 1.47-6.21) allele frequencies, both in hetero- and homozygosis, was observed in coeliac patients in comparison with healthy controls. In addition, simultaneous significant higher percentages of -308A and +874T alleles (p: 0.0066; OR: 2.33; CI: 1.42-3.82) as well as simultaneous significant lower percentages of -308A and +874T alleles (p: 0.003; OR: 0.23; CI: 0.10-0.60) were observed in coeliac patients compared with healthy controls.

CONCLUSIONS

Genetically determined higher frequencies of -308A tumour necrosis factor alpha and +874T interferon gamma alleles, both in hetero and in homozygosis and mostly whether simultaneous, may play a role in predisposing to gluten intolerance. Subjects positive for -308A tumour necrosis factor alpha and +874T interferon gamma alleles have an increased risk for coeliac disease.

No genetic association of the human prolyl endopeptidase gene in the Dutch celiac disease population

Celiac disease (CD) is a complex genetic disorder of the small intestine. The DQ2/DQ8 human leucocyte antigen (HLA) genes explain approximately 40% of the genetic component of the disease, but the remaining non-HLA genes have not yet been identified. The key environmental factor known to be involved in the disease is gluten, a major protein present in wheat, barley, and rye. Integrating microarray data and linkage data from chromosome 6q21-22 revealed the prolyl endopeptidase (PREP) gene as a potential CD candidate in the Dutch population. Interestingly, this gene encodes for the only enzyme that is able to cleave the proline-rich gluten peptides. To investigate the role of the human PREP gene as a primary genetic factor in CD, we conducted gene expression, sequence analysis, and genetic association studies of the PREP gene and determined PREP enzyme activity in biopsies from CD patients and controls. Sequence analysis of the coding region of the PREP gene revealed two novel polymorphisms. Genetic association studies using two novel polymorphisms and three known PREP variants excluded a genetic association between PREP and CD. Determination of PREP activity revealed weak but significant differences between treated and untreated CD biopsies (P < 0.05). Our results from the association study indicate that PREP is not a causative gene for CD in the Dutch population. These are further supported by the activity determinations in which we observed no differences in PREP activity between CD patients and controls.

Genetics in coeliac disease

Coeliac disease has a strong genetic component, higher than for many other common complex diseases. Possession of the HLA-DQ2 variant is required for presentation of disease causing dietary antigens to T cells, although this is also common in the healthy population. Non-HLA genetic factors account for the majority of heritable risk. Linkage studies have identified promising regions on chromosomes 5 and 19, with multiple other loci awaiting definitive confirmation in independent studies. Inherited variants in the tightly clustered chromosome 2q CD28-CTLA4-ICOS region are associated with disease, although of weak effect size. Larger sample sizes are necessary in coeliac disease genetic studies to detect small effects, alternatively meta-analysis offers promise. Newer methods including gene expression analysis and genome wide association studies will advance understanding of genetic susceptibility. Identification of coeliac disease genes may improve diagnostic/prognostic markers, basic understanding of disease aetiology, permit development of novel therapeutics and provide insight into other autoimmune disorders.

Advances in celiac disease

PURPOSE OF REVIEW

This article aims to summarize recent critical research in celiac disease.

RECENT FINDINGS

The crucial epitopes that confer toxicity to gliadin and related prolamins continue to be defined, as do methods of assessing their toxicity. New approaches to making the gluten-free diet more palatable are being studied.

SUMMARY

The position of proline residues is critical to the toxicity of cereal proteins to patients with celiac disease. Other genetic factors, apart from HLA status, remain elusive. Exciting advances in altering the toxicity of cereal proteins are being made.