Early microbial markers of celiac disease

Coincidence of antibodies against Hwp1 and ASCA, two distinct molecular targets of Candida albicans, reinforces the link between this fungal species and coeliac disease

Candida albicans is an immunogen for anti-Saccharomyces cerevisiae antibodies (ASCA), a serological marker of Crohn's disease. ASCA has also been reported in other autoimmune diseases, including coeliac disease (CeD). A strong antibody response against Hwp1, a protein associated with invasive hyphal form of C. albicans which presents peptide sequence homologies with gliadin, has also been described in CeD. This observation supports the hypothesis that C. albicans hyphal transition in C. albicans may trigger CeD onset through a mechanism of molecular/antigenic mimicry. In this study, we assessed whether the anti-C. albicans oligomannose and anti-Hwp1 protein responses may be linked despite their different pathophysiological significance. The measurement of ASCA levels in a cohort of patients involved in our previous Hwp1 study showed a significant correlation between the two biomarkers. This new observation further reinforces the link between C. albicans and CeD.

Non-Host Factors Influencing Onset and Severity of Celiac Disease

Celiac disease (CeD) is a chronic autoimmune condition driven by gluten ingestion in genetically predisposed individuals, resulting in inflammatory lesions in the proximal small intestine. Although the presence of specific HLA-linked haplotypes and gluten consumption are necessary for disease development, they alone do not account for the variable onset of CeD in susceptible individuals. This review explores the multifaceted role of non-host factors in CeD development, including dietary and microbial influences. We discuss clinical associations and observations highlighting the impact of these factors on disease onset and severity. Furthermore, we discuss studies in CeD-relevant animal models that offer mechanistic insights into how diet, the microbiome, and enteric infections modulate CeD pathogenesis. Finally, we address the clinical implications and therapeutic potential of understanding these cofactors offering a promising avenue for preventive and therapeutic interventions in CeD management.

From ASCA breakthrough in Crohn's disease and Candida albicans research to thirty years of investigations about their meaning in human health

Anti-Saccharomyces cerevisiae antibodies (ASCA) are human antibodies that can be detected using an enzyme-linked immunosorbent assay involving a mannose polymer (mannan) extracted from the cell wall of the yeast S. cerevisiae. The ASCA test was developed in 1993 with the aim of differentiating the serological response in two forms of inflammatory bowel disease (IBD), Crohn's disease and ulcerative colitis. The test, which is based on the detection of anti-oligomannosidic antibodies, has been extensively performed worldwide and there have been hundreds of publications on ASCA. The earlier studies concerned the initial diagnostic indications of ASCA and investigations then extended to many human diseases, generally in association with studies on intestinal microorganisms and the interaction of the micro-mycobiome with the immune system. The more information accumulates, the more the mystery of the meaning of ASCA deepens. Many fundamental questions remain unanswered. These questions concern the heterogeneity of ASCA, the mechanisms of their generation and persistence, the existence of self-antigens, and the relationship between ASCA and inflammation and autoimmunity. This review aims to discuss the gray areas concerning the origin of ASCA from an analysis of the literature. Structured around glycobiology and the mannosylated antigens of S. cerevisiae and Candida albicans, this review will address these questions and will try to clarify some lines of thought. The importance of the questions relating to the pathophysiological significance of ASCA goes far beyond IBD, even though these diseases remain the preferred models for their understanding.

Structural bases of T cell antigen receptor recognition in celiac disease

Celiac disease (CeD) is a human leukocyte antigen (HLA)-linked autoimmune-like disorder that is triggered by the ingestion of gluten or related storage proteins. The majority of CeD patients are HLA-DQ2.5⁺, with the remainder being either HLA-DQ8⁺ or HLA-DQ2.2⁺. Structural studies have shown how deamidation of gluten epitopes engenders binding to HLA-DQ2.5/8, which then triggers an aberrant CD4⁺ T cell response. HLA tetramer studies, combined with structural investigations, have demonstrated that repeated patterns of TCR usage underpins the immune response to some HLADQ2.5/8 restricted gluten epitopes, with distinct TCR motifs representing common landing pads atop the HLA-gluten complexes. Structural studies have provided insight into TCR specificity and cross-reactivity towards gluten epitopes, as well as cross-reactivity to bacterial homologues of gluten epitopes, suggesting that environmental factors may directly play a role in CeD pathogenesis. Collectively, structural immunology-based studies in the CeD axis may lead to new therapeutics/diagnostics to treat CeD, and also serve as an exemplar for other T cell mediated autoimmune diseases.

The double-edged sword of gut bacteria in celiac disease and implications for therapeutic potential

Celiac disease (CeD) is an immune-mediated disease, triggered by gluten ingestion, in genetically susceptible individuals. The gluten-free diet (GFD) is the only current treatment for CeD, but is difficult to follow, has high non-adherence rates, and does not always lead to symptomatic or mucosal remission. Microbially-mediated mechanisms have been proposed to contribute to disease pathogenesis, and clinical studies support an association, but mechanistic insight has been difficult to obtain. Recent advances using translational approaches have provided clues to the mechanisms through which bacteria could contribute to CeD pathogenesis. In this review we discuss these bacterially mediated mechanisms, which include the modulation of pathogenic or protective pathways. Targeting these pathways through microbial therapeutics could provide adjuvant therapies to the GFD.

The Possible Role of Pathogenic and Non-Pathogenic Bacteria in Initiation and Exacerbation of Celiac Disease; A Comprehensive Review

Celiac Disease (CD) is an immune-mediated enteropathy, generally of the proximal intestine, that occurs in genetically susceptible individuals triggered by the ingestion of gluten. The incidence and frequency of CD are increasing, and it is predicted that CD affects approximately 1% of the people worldwide. The common clinical manifestations of CD are divided in two sections, including classic and non-classic symptoms that can be created in childhood and adulthood. The relationship between pathogenic and non-pathogenic bacteria with CD is complex and multidirectional. In previous published studies, results demonstrated the triggering impact of bacteria, viruses, and parasites on initiation and development of Inflammatory Bowel Disease (IBD) and Irritable Bowel Syndrome (IBS). Different studies revealed the inducing effect of pathogenic and non-pathogenic bacteria on CD. However, increasing evidence proposes that some of these microorganisms can also play several positive roles in CD process. Although information of the pathogenesis of the CD is quickly expanding, the possible role of bacteria needs further examination. In conclusion, with respect to the possible correlation between different bacteria in CD, the current review-based study aims to discuss the possible relationship between CD and pathogenic and non-pathogenic bacteria and to show various and significant aspects of mechanisms involved in the CD process.

First-degree Relatives of Celiac Disease Patients Have Increased Seroreactivity to Serum Microbial Markers

Risk of celiac disease (CD) is increased in relatives of CD patients due to genetic and possible environmental factors. We recently reported increased seropositivity to anti-Saccharomyces cerevisiae (ASCA), Pseudomonas fluorescens-associated sequence (anti-I2) and Bacteroides caccae TonB-linked outer membrane protein (anti-OmpW) antibodies in CD. We hypothesized these markers also to be overrepresented in relatives. Seropositivity and levels of ASCA, anti-I2 and anti-OmpW were compared between 463 first-degree relatives, 58 untreated and 55 treated CD patients, and 80 controls. CD-associated human leukocyte antigen (HLA)-haplotypes and transglutaminase (tTGab) and endomysium (EmA) antibodies were determined. One or more of the microbial antibodies was present in 75% of relatives, 97% of untreated and 87% of treated CD patients and 44% of the controls. The relatives had higher median ASCA IgA (9.13 vs. 4.50 U/mL, p < 0.001), ASCA IgG (8.91 vs. 5.75 U/mL, p < 0.001) and anti-I2 (absorbance 0.74 vs. 0.32, p < 0.001) levels than controls. There was a weak, positive correlation between tTGab and ASCA (r = 0.31, p < 0.001). Seropositivity was not significantly associated with HLA. To conclude, seropositivity to microbial markers was more common and ASCA and anti-I2 levels higher in relatives of CD patients than controls. These findings were not associated with HLA, suggesting the role of other genetic and environmental factors.

T cell receptor cross-reactivity between gliadin and bacterial peptides in celiac disease

The human leukocyte antigen (HLA) locus is strongly associated with T cell-mediated autoimmune disorders. HLA-DQ2.5-mediated celiac disease (CeD) is triggered by the ingestion of gluten, although the relative roles of genetic and environmental risk factors in CeD is unclear. Here we identify microbially derived mimics of gliadin epitopes and a parental bacterial protein that is naturally processed by antigen-presenting cells and activated gliadin reactive HLA-DQ2.5-restricted T cells derived from CeD patients. Crystal structures of T cell receptors in complex with HLA-DQ2.5 bound to two distinct bacterial peptides demonstrate that molecular mimicry underpins cross-reactivity toward the gliadin epitopes. Accordingly, gliadin reactive T cells involved in CeD pathogenesis cross-react with ubiquitous bacterial peptides, thereby suggesting microbial exposure as a potential environmental factor in CeD.

Microbial Biomarkers in Patients with Nonresponsive Celiac Disease

BACKGROUND AND AIMS

In nonresponsive celiac disease (NRCD), the symptoms and duodenal damage persist despite a gluten-free diet. Celiac disease patients with persistent symptoms are found to have a dysbiotic microbiota. We thus hypothesized that increased seroreactivity to the serum gluten-sensitive microbial antibodies Saccharomyces cerevisiae (ASCA), Pseudomonas fluorescens-associated sequence (I2), and Bacteroides caccae TonB-linked outer membrane protein (OmpW) is associated with NRCD.

METHODS

ASCA, I2 and OmpW were measured in 20 seronegative CD patients with persistent villous damage despite strict dietary treatment (NRCD group). Fifty-eight responsive patients served as CD controls (55 on gluten-free treatment) and 80 blood donors as non-CD controls.

RESULTS

At least one microbial marker was positive in 80% of NRCD patients, in 97% of untreated CD and 87% of treated CD patients, and in 44% of controls. NRCD patients had the highest frequency of ASCA positivity (65% vs 52, 20, and 0%, respectively) and also significantly higher ASCA IgA (median 14.5 U/ml) and IgG (32.5 U/ml) titers than treated CD patients (7.0 U/ml, 13.0 U/ml) and non-CD controls (4.5 U/ml, 5.8 U/ml). The frequencies of I2 and OmpW were lower in NRCD than in untreated CD (65% and 45% vs 86% and 59%, respectively), and I2 titers were higher in NRCD (median absorbance 0.76) and untreated (1.0) and treated (0.83) CD than controls (0.32). OmpW was elevated in untreated (1.1) and treated (0.94) CD patients compared with controls (0.79).

CONCLUSIONS

Seropositivity and high titers of ASCA are associated with NRCD and might serve as an additional follow-up tool in CD.

Analysis of microbiota in first episode psychosis identifies preliminary associations with symptom severity and treatment response

The effects of gut microbiota on the central nervous system, along its possible role in mental disorders, have received increasing attention. Here we investigated differences in fecal microbiota between 28 patients with first-episode psychosis (FEP) and 16 healthy matched controls and explored whether such differences were associated with response after up to 12months of treatment. Numbers of Lactobacillus group bacteria were elevated in FEP-patients and significantly correlated with severity along different symptom domains. A subgroup of FEP patients with the strongest microbiota differences also showed poorer response after up to 12months of treatment. The present findings support the involvement of microbiota alterations in psychotic illness and may provide the basis for exploring the benefit of their modulation on treatment response and remission.

A Case of Chronic Cough in a Winemaker

BACKGROUND

Fungi have been known to cause a variety of respiratory conditions, ranging from mold- associated asthma to allergic bronchopulmonary mycosis and invasive disease. More recently some fungal species have been implicated in a non-asthmatic chronic cough syndrome.

CASE PRESENTATION

A 59-year-old male presented to the pulmonary clinic with chronic nonproductive cough. Workup included pulmonary function tests with methacholine challenge, sputum cultures, CT scans of the chest and therapeutic trial with proton pump inhibitors. Sputum cultures repeatedly showed Saccharomyces cerevisiae and patient had elevated specific IgA and IgG. Bronchoscopy was unremarkable, except for tracheal mucosa biopsies revealing acute and chronic inflammation. A one-month course of steroids provided temporary relief of chronic cough, but symptoms returned once steroids were discontinued. He also experienced temporary relief away from home. Upon further evaluation, the patient described his hobby of wine making which was believed to be the source of Saccharomyces cerevisiae. Once he stopped wine making at home and cleared his cellar, his symptoms stopped and have not returned since.

CONCLUSION

We describe a rare presentation of non-asthmatic chronic cough associated with exposure to Saccharomyces cerevisiae. This is the first report of fungi associated chronic cough without asthmatic features outside of Japan and the first one associated with Saccharomyces cerevisiae. This report provides further evidence linking fungi with chronic cough syndrome without the features of asthma or allergic bronchopulmonary mycosis.

Shotgun Metagenomics of 250 Adult Twins Reveals Genetic and Environmental Impacts on the Gut Microbiome

The gut microbiota has been typically viewed as an environmental factor for human health. Twins are well suited for investigating the concordance of their gut microbiomes and decomposing genetic and environmental influences. However, existing twin studies utilizing metagenomic shotgun sequencing have included only a few samples. Here, we sequenced fecal samples from 250 adult twins in the TwinsUK registry and constructed a comprehensive gut microbial reference gene catalog. We demonstrate heritability of many microbial taxa and functional modules in the gut microbiome, including those associated with diseases. Moreover, we identified 8 million SNPs in the gut microbiome and observe a high similarity in microbiome SNPs between twins that slowly decreases after decades of living apart. The results shed new light on the genetic and environmental influences on the composition and function of the gut microbiome that could relate to risk of complex diseases.

Patients with mild enteropathy have apoptotic injury of enterocytes similar to that in advanced enteropathy in celiac disease

BACKGROUND

Severity of villous atrophy in celiac disease (CeD) is the cumulative effect of enterocyte loss and cell regeneration. Gluten-free diet has been shown to benefit even in patients having a positive anti-tissue transglutaminase (tTG) antibody titre and mild enteropathy.

AIM

We explored the balance between mucosal apoptotic enterocyte loss and cell regeneration in mild and advanced enteropathies.

METHODS

Duodenal biopsies from patients with mild enteropathy (Marsh grade 0 and 1) (n=26), advanced enteropathy (Marsh grade ≥2) (n=41) and control biopsies (n=12) were subjected to immunohistochemical staining for end-apoptotic markers (M30, H2AX); markers of cell death (perforin, annexin V); and cell proliferation (Ki67). Composite H-scores based on the intensity and distribution of markers were compared.

RESULTS

End-apoptotic markers and marker of cell death (perforin) were significantly up-regulated in both mild and advanced enteropathies, in comparison to controls; without any difference between mild and advanced enteropathies. Ki67 labelling index was significantly higher in crypts of mild enteropathy, in comparison to controls, suggesting maintained regenerative activity in the former.

CONCLUSIONS

Even in patients with mild enteropathy, the rate of apoptosis is similar to those with advanced enteropathy. These findings suggest the necessity of reviewing the existing practice of not treating patients with mild enteropathy.

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

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

Elevated Total Iron-Binding Capacity Is Associated with an Increased Risk of Celiac Disease

BACKGROUND

Several lines of evidence suggest that abnormal iron homeostasis may itself play an important role in the development of celiac disease.

AIM

We sought to determine whether abnormalities in iron status could be detected prior to the diagnosis of celiac disease, and to understand the relationship between altered iron indices and the natural history of celiac disease.

METHODS

We conducted a case-control study at two major tertiary referral hospitals. Cases were comprised of patients with celiac disease in whom iron status was assessed prior to the diagnosis. Each case was matched to five controls without known gastrointestinal disease according to age and sex. Information on potential covariates and laboratory values within 1, 1-3, and 3-5 years prior to diagnosis was collected. We used conditional logistic regression to evaluate the effect of iron indices on risk of celiac disease.

RESULTS

We identified 157 celiac cases and 695 matched controls. Compared to participants with normal TIBC, the age-adjusted risk of celiac disease was significantly elevated among patients with elevated TIBC. For each 10 μg/dL increase in TIBC, the risk of celiac disease increased by 4.6, 3.8, and 7.9% within 1, 1-3, and 3-5 years prior to diagnosis, respectively. Patients with elevated pre-diagnosis TIBC were more likely to have abnormal liver enzymes and osteoporosis.

CONCLUSIONS

Elevated TIBC is associated with an increased risk of celiac disease. Further investigation into the potential role of altered iron homeostasis may uncover important environmental factors that contribute to the development of celiac disease.

Diagnostic and Prognostic Microbial Biomarkers in Inflammatory Bowel Diseases

The microbiome plays multifaceted roles in the pathogenesis of inflammatory bowel diseases (IBD). Accordingly, the clinical challenge of patient heterogeneity in disease phenotype and response to treatment should in part be addressed by biomarkers that detect the host response to microbiota, and the levels of microbial taxa and products eliciting the host response in susceptible individuals. Molecular analysis has revealed much evidence for microbial taxonomic membership and microbial products in association with IBD, but their utility as clinical biomarkers is still in its infancy. A rich area of progress has been the development and validation of host serologic microbial biomarkers, which have achieved a distinctive position in the diagnosis and prognosis in IBD, and as a template for defining other categories of microbial biomarkers in disease state and phenotype.

Possible association between celiac disease and bacterial transglutaminase in food processing: a hypothesis

The incidence of celiac disease is increasing worldwide, and human tissue transglutaminase has long been considered the autoantigen of celiac disease. Concomitantly, the food industry has introduced ingredients such as microbial transglutaminase, which acts as a food glue, thereby revolutionizing food qualities. Several observations have led to the hypothesis that microbial transglutaminase is a new environmental enhancer of celiac disease. First, microbial transglutaminase deamidates/transamidates glutens such as the endogenous human tissue transglutaminase. It is capable of crosslinking proteins and other macromolecules, thereby changing their antigenicity and resulting in an increased antigenic load presented to the immune system. Second, it increases the stability of protein against proteinases, thus diminishing foreign protein elimination. Infections and the crosslinked nutritional constituent gluten and microbial transglutaminase increase the permeability of the intestine, where microbial transglutaminases are necessary for bacterial survival. The resulting intestinal leakage allows more immunogenic foreign molecules to induce celiac disease. The increased use of microbial transglutaminase in food processing may promote celiac pathogenesis ex vivo, where deamidation/transamidation starts, possibly explaining the surge in incidence of celiac disease. If future research substantiates this hypothesis, the findings will affect food product labeling, food additive policies of the food industry, and consumer health education.

Humoral immunity links Candida albicans infection and celiac disease

Objective

The protein Hwp1, expressed on the pathogenic phase of Candida albicans, presents sequence analogy with the gluten protein gliadin and is also a substrate for transglutaminase. This had led to the suggestion that C. albicans infection (CI) may be a triggering factor for Celiac disease (CeD) onset. We investigated cross-immune reactivity between CeD and CI.

Methods

Serum IgG levels against recombinant Hwp1 and serological markers of CeD were measured in 87 CeD patients, 41 CI patients, and 98 healthy controls (HC). IgA and IgG were also measured in 20 individuals from each of these groups using microchips sensitized with 38 peptides designed from the N-terminal of Hwp1.

Results

CI and CeD patients had higher levels of anti-Hwp1 (p=0.0005 and p=0.004) and anti-gliadin (p=0.002 and p=0.0009) antibodies than HC but there was no significant difference between CeD and CI patients. CeD and CI patients had higher levels of anti-transglutaminase IgA than HC (p=0.0001 and p=0.0039). During CI, the increase in anti-Hwp1 paralleled the increase in anti-gliadin antibodies. Microchip analysis showed that CeD patients were more reactive against some Hwp1 peptides than CI patients, and that some deamidated peptides were more reactive than their native analogs. Binding of IgG from CeD patients to Hwp1 peptides was inhibited by γIII gliadin peptides.

Conclusions

Humoral cross-reactivity between Hwp1 and gliadin was observed during CeD and CI. Increased reactivity to Hwp1 deamidated peptide suggests that transglutaminase is involved in this interplay. These results support the hypothesis that CI may trigger CeD onset in genetically-susceptible individuals.

Clinical and diagnostic aspects of gluten related disorders

Gluten is one of the most abundant and widely distributed components of food in many areas. It can be included in wheat, barley, rye, and grains such as oats, barley, spelt, kamut, and triticale. Gluten-containing grains are widely consumed; in particular, wheat is one of the world’s primary sources of food, providing up to 50% of the caloric intake in both industrialized and developing countries. Until two decades ago, celiac disease (CD) and other gluten-related disorders were believed to be exceedingly rare outside of Europe and were relatively ignored by health professionals and the global media. In recent years, however, the discovery of important diagnostic and pathogenic milestones led CD from obscurity to global prominence. In addition, interestingly, people feeding themselves with gluten-free products greatly outnumber patients affected by CD, fuelling a global consumption of gluten-free foods with approximately $2.5 billion in United States sales each year. The acknowledgment of other medical conditions related to gluten that has arisen as health problems, providing a wide spectrum of gluten-related disorders. In February 2011, a new nomenclature for gluten-related disorders was created at a consensus conference in London. In this review, we analyse innovations in the field of research that emerged after the creation of the new classification, with particular attention to the new European Society for Paediatric Gastroenterology, Hepatology and Nutrition guidelines for CD and the most recent research about non-celiac gluten sensitivity.