Serologic assay based on gliadin-related nonapeptides as a highly sensitive and specific diagnostic aid in celiac disease

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

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

Specificity Enhancement of Glutenase Bga1903 toward Celiac Disease-Eliciting Pro-Immunogenic Peptides via Active-Site Modification

Celiac disease is an autoimmune disease triggered by oral ingestion of gluten, with certain gluten residues resistant to digestive tract enzymes. Within the duodenum, the remaining peptides incite immunogenic responses, including the generation of autoantibodies and inflammation, leading to irreversible damage. Our previous exploration unveiled a glutenase called Bga1903 derived from the Gram-negative bacterium Burkholderia gladioli. The cleavage pattern of Bga1903 indicates its moderate ability to mitigate the toxicity of pro-immunogenic peptides. The crystal structure of Bga1903, along with the identification of subsites within its active site, was determined. To improve its substrate specificity toward prevalent motifs like QPQ within gluten peptides, the active site of Bga1903 underwent site-directed mutagenesis according to structural insights and enzymatic kinetics. Among the double-site mutants, E380Q/S387L exhibits an approximately 34-fold increase in its specificity constant toward the QPQ sequence, favoring glutamines at the P1 and P3 positions compared to the wild type. The increased specificity of E380Q/S387L not only enhances its ability to break down pro-immunogenic peptides but also positions this enzyme variant as a promising candidate for oral therapy for celiac disease.

Diagnostic performances of celiac disease serological tests among Saudi patients

BACKGROUND

: The prevalence of celiac disease (CD) is relatively high in Saudi Arabia, and little is known about the accuracy of serological markers in the local population. This study aimed to assess the diagnostic performance of various serological markers for detecting CD in Saudi children and adults.

METHODS

We conducted a retrospective study of 148 CD patients and 512 controls to assess the diagnostic performances of IgA anti-tissue transglutaminase antibodies (TTG), IgG anti-TTG, IgA anti-deamidated gliadin peptide antibodies (anti-DGP), IgG anti-DGP, and endomysium antibodies (EMA).

RESULTS

: Immunoglobulin A (IgA) anti-TTG was the most sensitive test [98.9% (95% confidence interval (CI) 94.1-99.8%)], while EMA was the most specific [100%, 95%CI 98.6-100%]. By applying the criteria of IgA anti-TTG titers ≥10 × upper limit of normal (ULN) and positive EMA, 57.3% of patients could have avoided intestinal biopsy. IgG anti-DGP test had a sensitivity of 85.9% (95% CI = 77.3-91.5%) and a specificity of 93.5% (95% CI = (90.0-95.9%). Titers of IgA anti-TTG, IgA anti-DGP, and IgG anti-DGP were higher in CD patients with the Marsh 3c class than in those with the Marsh 3b and Marsh 3a classes. IgG anti-TTG and IgA anti-DGP had no additional diagnostic value.

CONCLUSIONS

: IgA anti-TTG and EMA are excellent CD markers in children and adults. The use of IgA anti-TTG titers ≥10 × ULN and positive EMA as criteria for CD diagnosis in children and adults might be a good alternative to intestinal biopsy.

The Immunobiology and Pathogenesis of Celiac Disease

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

Immunoanalytic investigation of grain proteins antigenic for celiac disease patients in an einkorn collection

Our study focuses on the complex characterization of a wild and cultivated einkorn collection of the Cereal Gene Bank of Agriculture Research Institute in Hungary, using proteomics, immune analytics and bioinformatics analyses. In a serological ELISA pre-screen of 208 different Triticum monococcum L. ssp. monococcum and Triticum monococcum L. ssp. aegilopoides genotypes with celiac disease samples high diversity was observed in the immune response. Based on the immune analytic results, four genotypes with significantly reduced immune reactivity were selected for detailed proteomics characterization. Our results confirm the benefits of high-throughput/large-scale pre-screening and the use of a complex examination platform to get relevant information about the genetic diversity of celiac disease-relevant proteins in the analyzed einkorn genotypes. These genotypes cannot be incorporated into the daily diet of celiac patients; however, they may represent candidates - especially in combination with enzymatic treatments - to improve the lifestyle of individuals suffering from other clinical conditions like non-celiac wheat sensitivity.

Changes in Non-Deamidated versus Deamidated Epitope Targeting and Disease Prediction during the Antibody Response to Gliadin and Transglutaminase of Infants at Risk for Celiac Disease

Celiac disease (CeD) is a conditional autoimmune disorder with T cell-mediated immune response to gluten coupled with antibody production to gliadin and the self-protein tissue transglutaminase (TG2). TG2 contributes to the CeD pathomechanism by deamidating gliadin, thereby generating more immunogenic peptides. Anti-gliadin antibodies may appear before the autoantibody production. The scope of this study was to dissect these early antibody responses by investigating serum samples collected during the PreventCD prospective double-blind study, where infants with high CeD risk were randomized to 200 mg daily gluten intake or placebo from 4 to 6 months of age, followed by frequent blood testing on regular gluten consumption in both groups. After primary gluten intake, children with or without later CeD produced IgA and IgG antibodies which preferentially recognized non-deamidated gliadin peptides. At CeD development with anti-TG2 seroconversion, there was a significant increase in the antibody reaction toward deamidated gliadin peptides (DGP), with maturation in the binding strength for the PEQPFP gamma-gliadin core peptide. The earliest produced autoantibodies targeted TG2’s celiac epitope 2. Our results reveal a qualitative change in the gliadin-directed humoral immune response at the time when anti-TG2 antibodies appear, but anti-DGP antibodies in the absence of anti-TG2 antibodies are not disease-predictive.

Diagnosing and Monitoring Celiac Patients with Selective IgA Deficiency: Still an Open Issue

Although, the association between celiac disease (CD) and selective immunoglobulin A deficiency (SIgAD) has been known for more than fifty years, the procedures for diagnosing and monitoring patients with both conditions are still far from definitive. When serological markers were introduced as pre-bioptic investigations, it was immediately clear that searching for specific IgA antibodies without checking total serum IgA could lead to a failure in diagnosing IgA-deficient CD patients, while specific IgG antibodies could be useful as additional tests, because they are frequently found in the serum of affected patients. Nonetheless, until recently the diagnosis of CD in IgA-deficient patients was based on the few, fragmentary and often contradictory data available in literature. The introduction of the European Society for Pediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) guidelines in 2012 provided the current criteria for diagnosing CD in IgA-deficient patients, although some issues remained open, such as the selection of patients who should undergo specific IgG antibody testing and the choice of the most reliable IgG-based test for both diagnosis and follow-up. A real-life study recently assessed the impact of the 2012 ESPGHAN guidelines in diagnosing and monitoring CD in SIgAD patients, highlighting several pitfalls that can lead to operational uncertainties and difficulties in patient management. In the present report, the evolution of diagnostic tools and criteria for CD in SIgAD patients has been critically assessed, both strengths and open issues have been highlighted, and future perspectives for improving the current diagnostic protocols have been suggested.

Gamma-gliadin specific celiac disease antibodies recognize p31-43 and p57-68 alpha gliadin peptides in deamidation related manner as a result of cross-reaction

Celiac disease (CeD) is a T-cell-dependent enteropathy with autoimmune features where tissue transglutaminase (TG2)-mediated posttranslational modification of gliadin peptides has a decisive role in the pathomechanism. The humoral immune response is reported to target mainly TG2-deamidated γ-gliadin peptides. However, α-gliadin peptides, like p57-68, playing a crucial role in the T-cell response, and p31-43, a major trigger of innate responses, also contain B-cell gliadin epitopes and γ-gliadin like motifs. We aimed to identify if there are anti-gliadin-specific antibodies in CeD patients targeting the p31-43 and p57-68 peptides and to examine whether deamidation of these peptides could increase their antigenicity. We explored TG2-mediated deamidation of the p31-43 and p57-68 peptides, and investigated serum antibody reactivity toward the native and deamidated α and γ-gliadin peptides in children with confirmed CeD and in prospectively followed infants at increased risk for developing CeD. We affinity-purified antibody populations utilizing different single peptide gliadin antigens and tested their binding preferences for cross-reactivity in real-time interaction assays based on bio-layer interferometry. Our results demonstrate that there is serum reactivity toward p31-43 and p57-68 peptides, which is due to cross-reactive γ-gliadin specific antibodies. These γ-gliadin specific antibodies represent the first appearing antibody population in infancy and they dominate the serum reactivity of CeD patients even later on and without preference for deamidation. However, for the homologous epitope sequences in α-gliadins shorter than the core QPEQPFP heptapeptide, deamidation facilitates antibody recognition. These findings reveal the presence of cross-reactive antibodies in CeD patients recognizing the disease-relevant α-gliadins.

Deamidated Gliadin Antibodies: Do They Add to Tissue Transglutaminase-IgA Assay in Screening for Celiac Disease?

OBJECTIVES

Use of deamidated gliadin peptide (DGP) test kits as adjunctive to tissue-transglutaminase-IgA (TTG-IgA) for the diagnosis of celiac disease (CD) has been a controversial issue. The objectives of our study were to evaluate the diagnostic performance of DGP antibodies compared with TTG-IgA and to evaluate the correlation between DGP-antibody titers and degree of enteropathy.

METHODS

We included children who underwent endoscopy and biopsies because of positivity of any of the serology tests in the "celiac profile" (TTG-IgA, DGP-IgA, and DGP-IgG) from 2012 to 2019. We divided children into clinically suspected cases of CD (group 1) and asymptomatic cases screened as they were from a high-risk group (group 2).

RESULTS

Group 1 constituted 52 children and group 2 included 81 children (76 type-1 diabetes [T1D]). The sensitivity and positive-predictive value (PPV) of DGP-IgG in group 1 (90%, 98%) and group 2 (91%, 85.5%) were comparable with TTG-IgA (98%, 92% in group 1; 100%, 80% in group 2). By adding DGP-IgG to TTG-IgA, the performance of TTG-IgA has improved marginally in group 1 (sensitivity 100%, PPV 92.3%). All cases with DGP-IgG titer 2 times ULN in group 1, and >4 times ULN in group 2 had villous atrophy. All T1D patients with TTG IgA >10 times ULN had villous atrophy.

CONCLUSIONS

DGP-IgG assay did not add to the performance of TTG-IgA. DGP-IgG titer correlated with enteropathy. The diagnosis of CD can be made in asymptomatic T1D child with TTG-IgA titer >10 times ULN and positive endomyseal antibodies.

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

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

Serological Diagnosis of Autoimmune Bullous Skin Diseases

Autoimmune bullous dermatoses (AIBD) encompass a variety of organ-specific autoimmune diseases that manifest with cutaneous and/or mucosal blisters and erosions. They are characterized by autoantibodies targeting structural proteins of the skin, which are responsible for the intercellular contact between epidermal keratinocytes and for adhesion of the basal keratinocytes to the dermis. The autoantibodies disrupt the adhesive functions, leading to splitting and blister formation. In pemphigus diseases, blisters form intraepidermally, whereas in all other disease types they occur subepidermally. Early identification of autoimmune bullous dermatoses is crucial for both treatment and prognosis, particularly as regards tumor-associated disease entities. The diagnosis is based on clinical symptoms, histopathology, direct immunofluorescence to detect antibody/complement deposits, and the determination of circulating autoantibodies. The identification of various target antigens has paved the way for the recent development of numerous specific autoantibody tests. In particular, optimized designer antigens and multiplex test formats for indirect immunofluorescence and ELISA have enhanced and refined the laboratory analysis, enabling highly efficient serodiagnosis and follow-up. This review elaborates on the current standards in the serological diagnostics for autoimmune bullous dermatoses.

Strong Clonal Relatedness between Serum and Gut IgA despite Different Plasma Cell Origins

Mucosal antigens induce generation of lamina propria plasma cells (PCs) that secrete dimeric immunoglobulin A (IgA) destined for transport across the epithelium. In addition, blood contains monomeric IgA. To study the relationship between mucosal and systemic antibody responses, we took advantage of celiac disease patient samples for isolation of gut PCs as well as serum IgA and IgG reactive with a gluten-derived peptide or the autoantigen transglutaminase 2. Proteomic analysis of serum IgA revealed antigen-specific V-gene preferences, which matched those found in gut PCs. Further, gut PC CDR-H3 sequences were abundant in serum IgA but also detectable in serum IgG. Our data indicate that the same B cell clones that give rise to gut PCs also contribute to the serum antibody pool. However, serum IgA antibodies had a molecular composition distinct from that of IgA antibodies secreted in the gut, suggesting that individual B cell clones give rise to different PC populations.

Celiac disease: from etiological factors to evolving diagnostic approaches

Celiac disease has advanced from a medical rarity to a highly prevalent disorder. Patients with the disease show varying degrees of chronic inflammation within the small intestine due to an aberrant immune response to the digestion of gliadin found in wheat. As a result, cytokines and antibodies are produced in celiac patients that can be used as specific biomarkers for developing diagnostic tests. This review paper describes celiac disease in terms of its etiological cause, pathological effects, current diagnostic tests based on mucosal biopsy, and the genetic basis for the disease. In addition, it discusses the use of gliadin-induced cytokines, antibodies and autoantibodies as a diagnostic tool for celiac disease. Despite good initial results in terms of sensitivity and specificity, when these immunological tests were used on a large scale, even in combination with genetic testing, the results showed lower predictive value. This review addresses that issue and ends with an outlook on future work required to develop diagnostic tests with greater accuracy in predicting celiac disease in the general public, thus avoiding the need for endoscopy and mucosal biopsy.

Differential antibody responses to gliadin-derived indigestible peptides in patients with schizophrenia

Gluten consumption has previously been implicated in the development of schizophrenia while an immunological link between gluten and schizophrenia was established by the detection of circulating antibodies against gliadin, a major component of wheat gluten. Several studies have reported an increase in circulating antibodies against native gliadin molecules that are unlikely to survive degradation in the digestive system. In this study, therefore, we measured plasma immunoglobulin G (IgG) and IgA antibodies against indigestible gliadin-derived peptide antigens using an in-house enzyme-linked immunosorbent assay (ELISA) among 169 patients with schizophrenia and 236 control subjects. We also examined the plasma levels of IgG and IgA antibodies against the mixture of native gliadins using commercially available ELISA kits. The results showed that patients with schizophrenia had the increased levels of plasma IgG against the γ-gliadin-derived fragment, namely AAQ6C, but decreased levels of plasma IgG against the α- and γ3-gliadin-derived antigens, as compared with control subjects. This study also demonstrated a uniform decrease in plasma IgA antibodies against gliadin-derived antigens. There was no significant difference in the levels of plasma antibodies against native gliadins between the patient group and the control group. Of eight gliadin-derived antigens tested, four showed a sensitivity of >20% against the specificity of ⩾95% for detection of their corresponding antibodies in plasma. These four tests may thus have a potential to serve as biomarkers for the identification of schizophrenia subgroups that may need an alternative therapy or precision treatment. Further investigation with clinical trials should be carried out to explore this possibility.

Selective IgA Deficiency: Epidemiology, Pathogenesis, Clinical Phenotype, Diagnosis, Prognosis and Management

Selective immunoglobulin A deficiency (SIgAD) is the most common primary antibody deficiency. Although more patients with SIgAD are asymptomatic, selected patients suffer from different clinical complications such as pulmonary infections, allergies, autoimmune diseases, gastrointestinal disorders and malignancy. Pathogenesis of SIgAD is still unknown; however, a defective terminal differentiation of B cells and defect in switching to IgA-producing plasma cells are presumed to be responsible. Furthermore, some cytogenic defects and monogenic mutations are associated with SIgAD. There is no specific treatment for patients with symptomatic IgA deficiency, although prophylactic antibiotic therapy along with circumstantial immunoglobulin replacement with justification and supportive care (using a product that contains minimal IgA) could be helpful for patients with a severe phenotype. The epidemiology, pathogenesis, clinical phenotype, diagnosis, prognosis, management and treatment in patients with SIgAD have been reviewed.

Interpretation of serological tests in the diagnosis of celiac disease: Anti-deamidated gliadin peptide antibodies revisited

Algorithms for celiac disease diagnosis provided by guidelines are based primarily on anti-tissue transglutaminase 2 (TG2) antibodies and/or anti-endomysium antibodies. The place of anti-deamidated gliadin peptide (DGP) antibodies is less well established. This study was designed to assess the clinical relevance of anti-DGP antibodies. Two thousand and twenty-six consecutive unselected patients systematically tested for anti-TG2, endomysium, gliadin, DGP antibodies and IgA dosage were investigated. The serological interpretation was assessed by analyzing the medical records of patients. From the 1984 newly investigated patients suspected of celiac disease, 10% had at least one celiac marker. Anti-TG2, anti-endomysium, anti-gliadin and anti-DGP antibodies were found in 1.1%, 0.6%, 6.8% and 4.1% of cases respectively, with different combinations. The diagnosis of celiac disease was retained in 0.45% of patients. When using the duodenal biopsies as a gold standard, analysis of the anti-DGP diagnosis performance showed that the specificity and the predictive positive value (PPV) were lower than that of the anti-TG2 assay. The combined detection of anti-TG2 and anti-DGP antibodies had a lower PPV than that of anti-TG2 and anti-endomysium antibodies (p = 0.04). When analyzing the contribution of anti-DGP antibodies as an additional marker to both anti-TG2 and anti-endomysium antibodies, the PPV of the three associated antibodies was shown to be significantly lower than the PPV of the both anti-TG2 and anti-endomysium antibodies (p = 0.04). As a conclusion, anti-DGP antibodies may not have the diagnosis value required as an additional screening test to anti-TG2 antibodies for identifying celiac disease patients in medical centers where anti-endomysium detection is available.

Gluten-specific antibodies of celiac disease gut plasma cells recognize long proteolytic fragments that typically harbor T-cell epitopes

This study aimed to identify proteolytic fragments of gluten proteins recognized by recombinant IgG1 monoclonal antibodies generated from single IgA plasma cells of celiac disease lesions. Peptides bound by monoclonal antibodies in complex gut-enzyme digests of gluten treated with the deamidating enzyme transglutaminase 2, were identified by mass spectrometry after antibody pull-down with protein G beads. The antibody bound peptides were long deamidated peptide fragments that contained the substrate recognition sequence of transglutaminase 2. Characteristically, the fragments contained epitopes with the sequence QPEQPFP and variants thereof in multiple copies, and they typically also harbored many different gluten T-cell epitopes. In the pull-down setting where antibodies were immobilized on a solid phase, peptide fragments with multivalent display of epitopes were targeted. This scenario resembles the situation of the B-cell receptor on the surface of B cells. Conceivably, B cells of celiac disease patients select gluten epitopes that are repeated multiple times in long peptide fragments generated by gut digestive enzymes. As the fragments also contain many different T-cell epitopes, this will lead to generation of strong antibody responses by effective presentation of several distinct T-cell epitopes and establishment of T-cell help to B cells.

Serologic assay for diagnosis of celiac disease based on a patient-derived monoclonal antigliadin antibody

BACKGROUND & AIMS

Patients with celiac disease can be identified based on the detection of serum antibodies to deamidated gliadin peptides (DGPs). Recombinant human monoclonal antibodies (hmAb) against gliadin are produced by cloning antibody genes from single IgA-producing plasma cells isolated from lesions of patients with celiac disease. We developed an assay to identify patients with celiac disease based on the ability of antibodies from their serum to inhibit the binding of a gliadin-specific hmAb (1002-1E03) to a specific peptide antigen (inhibition assay).

METHODS

We selected 2 peptides (a 34-mer and a 26-mer) found in ω-gliadins and low-molecular-weight glutenins that had been identified as specific targets of the hmAb 1002-1E03 from a digest of gliadin treated by transglutaminase 2. These peptides contained repeat sequence motifs; their interaction with hmAb 1002-1E03 was assessed in an amplified luminescent proximity homogeneous inhibition assay. We also tested peptides we created that included 3 repeated sequence motifs. Serum samples from untreated patients diagnosed with celiac disease (n = 106) and 2 control groups (198 blood donors, 151 patients with Crohn's disease) were analyzed using the assay, as well as in conventional commercial assays that measure IgA against transglutaminase 2 (TG2) or IgG against DGP.

RESULTS

In our inhibition assays, the 34-mer peptide showed the best results, and identified patients with celiac disease with 86.8% sensitivity and 98.6% specificity. Its diagnostic accuracy was comparable with that of commercial anti-DGP IgG (sensitivity, 87.9%; specificity, 98.0) and anti-TG2 IgA (sensitivity, 81.1%; specificity, 98.9) assays, and it detected most of the patients with anti-TG2 IgA-negative celiac disease without a significant decrease in specificity. Combined use of the anti-ω34 and the anti-TG2 assays produced specificity and sensitivity values of 95.3% and 98.0%, respectively.

CONCLUSIONS

We developed an antigliadin inhibition assay that identifies patients with celiac disease with high levels of specificity and sensitivity. It may prove useful as an adjunct to the current assay for anti-TG2 IgA.

Antibodies to deamidated gliadin peptide in diagnosis of celiac disease in children

OBJECTIVES

Determination of antibodies to synthetic deamidated gliadin peptides (anti-DGPs) may work as an alternative or complement the commonly used test for tissue transglutaminase antibodies (TGA) in the diagnosis of celiac disease (CD). We analyzed the performance of a time-resolved immunofluorometric anti-DGP assay (TR-IFMA) in the diagnosis of CD in children and also retrospectively analyzed the appearance of anti-DGP antibodies before TGA seroconversion.

METHODS

The study included 92 children with biopsy-confirmed CD. Serum samples were taken at the time or just before the clinical diagnosis. The control group comprised 82 TGA-negative children who were positive for human leucocyte antigen-DQ2 or -DQ8.

RESULTS

Based on receiver operating characteristic curves, the optimal cutoff value for immunoglobulin (Ig) A anti-DGP positivity was 153 arbitrary units (AUs) with a sensitivity of 92.4% and specificity of 97.6% and that for IgG anti-DGP 119 AU, with a sensitivity of 97.8% and specificity of 97.6%. All 92 children with CD were either IgA or IgG anti-DGP positive at the time of diagnosis. Sera from 48 children with CD were also analyzed retrospectively before the diagnosis. Anti-DGP antibodies preceded TGA positivity in 35 of the 48 children with CD and appeared a median of 1 year earlier.

CONCLUSIONS

The TR-IFMA assay for detecting anti-DGP antibodies shows high sensitivity and specificity for the diagnosis of CD in children. In a majority of our study population, anti-DGP seropositivity preceded TGA positivity, indicating that earlier detection of CD may be possible by monitoring anti-DGP antibodies frequently in genetically susceptible children.

Assessing of Celiac Disease and Nonceliac Gluten Sensitivity

The publication of papers on the topic of gluten related disorders has substantially increased over the last few years. This has motivated healthcare professionals to pay attention not only to celiac disease and wheat allergy but also to a condition termed nonceliac gluten sensitivity (NCGS). Until now this condition has been diagnosed clinically on the basis of exclusion criteria and clinical response to gluten withdrawal. In addition, recent research in this field has shown that other food components distinct from gluten are implicated in NCGS cases, thereby changing our general understanding of NCGS diagnosis in either individuals on gluten containing diets or those already following a gluten-free diet with no proper diagnostic work-up of celiac disease. With this in mind, the assessment of NCGS will require extensive knowledge of celiac disease manifestations and the laboratory tests commonly performed during diagnosis of celiac disease.

Overview of biomarkers for diagnosis and monitoring of celiac disease

Among the adverse reactions caused by wheat, celiac disease (CD) is the longest studied and best-known pathology. The more recently defined non-celiac gluten sensitivity (NCGS) presents with symptoms which are often indistinguishable from CD. Diagnosis of CD is based on serologic, molecular, and bioptic testing. The IgA anti-transglutaminase (tTG) test is considered highly important, as it shows high sensitivity and specificity and its levels correlate to the degree of intestinal damage. Small bowel biopsy can be avoided in symptomatic patients with IgA anti-tTG levels above 10× the manufacturer's cut-off. Recently, tests of anti-deamidated peptides of gliadin (DGP) have replaced classic anti-native gliadin (AGA) tests. DGP assays have a considerably higher diagnostic accuracy than AGA assays, especially in the IgG class, and can replace anti-tTG tests in patients with selective IgA deficiency. The combination of IgG anti-DGP plus IgA anti-tTG assays show greater sensitivity than a single test, with very high specificity. EMA tests have great diagnostic accuracy but are not recommended by all the latest guidelines because they are observer dependent. Biopsy must still be considered the gold standard for CD diagnosis. HLA-DQ genotyping can be used to screen asymptomatic children and in cases of histology/serology disagreement. About half of NCGS patients are DQ2 positive and have IgG AGA. To diagnose NCGS, first CD and wheat allergy must be excluded; then the wheat dependence of symptoms must be verified by a gluten-free diet and subsequent gluten challenge.

Specific nongluten proteins of wheat are novel target antigens in celiac disease humoral response

While the antigenic specificity and pathogenic relevance of immunologic reactivity to gluten in celiac disease have been extensively researched, the immune response to nongluten proteins of wheat has not been characterized. We aimed to investigate the level and molecular specificity of antibody response to wheat nongluten proteins in celiac disease. Serum samples from patients and controls were screened for IgG and IgA antibody reactivity to a nongluten protein extract from the wheat cultivar Triticum aestivum Butte 86. Antibodies were further analyzed for reactivity to specific nongluten proteins by two-dimensional gel electrophoresis and immunoblotting. Immunoreactive molecules were identified by tandem mass spectrometry. Compared with healthy controls, patients exhibited significantly higher levels of antibody reactivity to nongluten proteins. The main immunoreactive nongluten antibody target proteins were identified as serpins, purinins, α-amylase/protease inhibitors, globulins, and farinins. Assessment of reactivity toward purified recombinant proteins further confirmed the presence of antibody response to specific antigens. The results demonstrate that, in addition to the well-recognized immune reaction to gluten, celiac disease is associated with a robust humoral response directed at a specific subset of the nongluten proteins of wheat.

Early diagnosis of celiac disease in IgA deficient children: contribution of a point-of-care test

Background

The serological diagnosis of celiac disease (CD) often relies on the presence of anti-tissue transglutaminase (tTG) IgA autoantibodies. Patients suffering from selective IgA deficiency (IgAD) are often not aware of their IgA deficiency and are tested as CD negative, delaying considerably the diagnosis. The detection of IgG against deamidated gliadin peptides (DGP) has high specificity and better sensitivity than IgG anti-tTG. A multi-analytic lateral-flow immunochromatographic assay (CD-LFIA) based on the detection of IgA and IgG anti-DGP and total IgA was shown to have a good diagnostic accuracy for CD. The aim of this study was to evaluate the clinical accuracy of its use in children suffering from IgAD.

Methods

45 IgAD children ranging from 1.1 to 17.4 years and suspected of CD or having high CD risk factors were referred from outpatient clinics located in the area of Rhone-Alpes (France) to the Hospices Civils de Lyon, Paediatric Hospital-Gastroenterology-Hepatology- Nutrition Department for further CD investigations. The CD investigations, including the sample collection, were performed within the Paediatric Hospital-Gastroenterology-Hepatology- Nutrition Department, and the serological testing was performed at the Lyon-Sud Hospital-Immunology Laboratory. The diagnosis of CD was based on IgG anti-tTG serology, biopsy results and patient follow-up. The serum samples were retrospectively tested on the CD-LFIA test.

Results

A total of eight (8) patients were diagnosed as new CD. All were correctly identified by the CD-LFIA. The test yielded four (4) false positive results. Two patients with positive IgG anti-tTG were negative on CD-LFIA, but were classified as CD negative based on biopsy results and patient follow-up. The remaining 33 patients were found negative by both methods. The specificity and sensitivity of CD-LFIA was of 89.2% [74.6-97.0] and of 100% [63.1-100] respectively. The negative predictive value (NPV) was of 100% [89.4-100], and the Likelihood Ratio for Negative Test (LR-) was of 0 [0.0-0.91].

Conclusions

CD-LFIA is a useful, non-invasive and rapid tool to rule out CD in primary care paediatric patients having CD-related symptoms and IgAD. Patients having a positive CD-LFIA result could be then readily directed to secondary care setting for further evaluation by standard serology and biopsy.

Restricted VH/VL usage and limited mutations in gluten-specific IgA of coeliac disease lesion plasma cells

Coeliac disease (CD), an enteropathy caused by cereal gluten ingestion, is characterized by CD4(+) T cells recognizing deamidated gluten and by antibodies reactive to gluten or the self-antigen transglutaminase 2 (TG2). TG2-specific immunoglobulin A (IgA) of plasma cells (PCs) from CD lesions have limited somatic hypermutation (SHM). Here we report that gluten-specific IgA of lesion-resident PCs share this feature. Monoclonal antibodies were expression cloned from single PCs of patients either isolated from cultures with reactivity to complex deamidated gluten antigen or by sorting with gluten peptide tetramers. Typically, the antibodies bind gluten peptides related to T-cell epitopes and many have higher reactivity to deamidated peptides. There is restricted VH and VL combination and usage among the antibodies. Limited SHM suggests that a common factor governs the mutation level in PCs producing TG2- and gluten-specific IgA. The antibodies have potential use for diagnosis of CD and for detection of gluten.

Lack of serologic evidence to link IgA nephropathy with celiac disease or immune reactivity to gluten

IgA nephropathy is the most common form of primary glomerulonephritis worldwide. Mucosal infections and food antigens, including wheat gluten, have been proposed as potential contributing environmental factors. Increased immune reactivity to gluten and/or association with celiac disease, an autoimmune disorder triggered by ingestion of gluten, have been reported in IgA nephropathy. However, studies are inconsistent about this association. We aimed to evaluate the proposed link between IgA nephropathy and celiac disease or immune reactivity to gluten by conducting a comprehensive analysis of associated serologic markers in cohorts of well-characterized patients and controls. Study participants included patients with biopsy-proven IgA nephropathy (n = 99), unaffected controls of similar age, gender, and race (n = 96), and patients with biopsy-proven celiac disease (n = 30). All serum specimens were tested for IgG and IgA antibodies to native gliadin and deamidated gliadin, as well as IgA antibody to transglutaminase 2 (TG2). Anti-TG2 antibody-positive nephropathy patients and unaffected controls were subsequently tested for IgA anti-endomysial antibody and genotyped for celiac disease-associated HLA-DQ2 and -DQ8 alleles. In comparison to unaffected controls, there was not a statistically significant increase in IgA or IgG antibody reactivity to gliadin in individuals with IgA nephropathy. In addition, the levels of celiac disease-specific serologic markers, i.e., antibodies to deamidated gliadin and TG2, did not differ between IgA nephropathy patients and unaffected controls. Results of the additional anti-endomysial antibody testing and HLA genotyping were corroborative. The data from this case-control study do not reveal any evidence to suggest a significant role for celiac disease or immune reactivity to gluten in IgA nephropathy.

Persistence of elevated deamidated gliadin peptide antibodies on a gluten-free diet indicates nonresponsive coeliac disease

BACKGROUND

Histologically nonresponsive coeliac disease (NRCD) is a potentially serious condition diagnosed during the follow-up of coeliac disease (CD) when patients have persistent villous atrophy despite following a gluten-free diet (GFD).

AIM

As current assessments of recovery are limited to invasive and costly serial duodenal biopsies, we sought to identify antibody biomarkers for CD patients that do not respond to traditional therapy.

METHODS

Bacterial display peptide libraries were screened by flow cytometry to identify epitopes specifically recognised by antibodies from patients with NRCD, but not by antibodies from responsive CD patients. Deamidated gliadin was confirmed to be the antigen mimicked by library peptides using ELISA with sera from NRCD (n = 15) and responsive CD (n = 45) patients on a strict GFD for at least 1 year.

RESULTS

The dominant consensus epitope sequence identified by unbiased library screening QPxx(A/P)FP(E/D) was highly similar to reported deamidated gliadin peptide (dGP) B-cell epitopes. Measurement of anti-dGP IgG titre by ELISA discriminated between NRCD and responsive CD patients with 87% sensitivity and 89% specificity. Importantly, dGP antibody titre correlated with the severity of mucosal damage indicating that IgG dGP titres may be useful to monitor small intestinal mucosal recovery on a GFD.

CONCLUSIONS

The finding of increased levels of anti-dGP IgG antibodies in CD patients on strict GFDs effectively identifies patients with NRCD. Finally, anti-dGP IgG assays may be useful to monitor mucosal damage and histological improvement in CD patients on a strict GFD.

Prevalence of serum celiac antibody in patients with IBD in Japan

BACKGROUND

Although the incidence of inflammatory bowel diseases (IBD) in Japan has increased, the prevalence of celiac disease is considered very low with the lowest genetic disposition. IBD is reported as the most common comorbidity because of the high positive rate of serological celiac markers. The aim of this study was to examine the current incidence of celiac disease, especially in IBD patients in Japan, where both wheat consumption and incidence of IBD have increased.

METHODS

A total of 172 patients with IBD and 190 controls in Japan were screened for serum antibody of tissue transglutaminase and deaminated gliadin peptide. In sero-positive patients, HLA testing and upper gastrointestinal endoscopy with duodenal biopsy was performed. Some of the sero-positive patients started a gluten-restricted or unrestricted diet, and serological change was determined.

RESULTS

The positivity of both serum antibodies was significantly higher in IBD and correlated with disease activity. However, no biopsy-defined or HLA-defined true celiac disease was found. A decrease in serum antibody titers was observed with a gluten-restricted diet.

CONCLUSIONS

Despite the increased incidence of IBD and high positivity for serum celiac antibody in Japanese IBD patients, no true-positive celiac disease was noted, suggesting the presence of gluten intolerance in these populations.

Cutaneous expressions of interleukin-6 and neutrophil elastase as well as levels of serum IgA antibodies to gliadin nonapeptides, tissue transglutaminase and epidermal transglutaminase: implications for both autoimmunity and autoinflammation involvement in dermatitis herpetiformis

Introduction

Dermatitis herpetiformis (DH) seems to be a chronic immune-mediated inflammatory disease of partially known origin. In light of its known biological functions and its involvement in tissue pathology in other disease states, particularly in nickel-induced allergic contact dermatitis coexisting with DH, it would appear that the central and peripheral response by neutrophils and their mediators (e.g. neutrophil elastase – NE) in DH may be partially mediated by interleukin-6 (IL-6).

The aim of the study was to assess the role of IL -6 in DH lesions by examining the relationships between IL -6/NE cutaneous expression and levels of serum anti-nonapeptides of gliadin (npG) IgA, anti-tissue transglutaminase (tTG) immunoglobulin A (IgA), anti-epidermal transglutaminase (eTG) IgA in DH.

Material and methods

In total, 24 DH patients having IgA cutaneous deposition were studied. Immunohistochemistry on paraffin-embedded sections with quantitative digital morphometry was used to measure the intensity of IL -6 and NE cutaneous expressions. Levels of serum anti-npG IgA, anti-tTG IgA and anti-eTG IgA were evaluated with ELISA.

Results

We found no statistically significant correlation between the NE and IL -6 expression intensities. Our results revealed also a lack of correlations between NE/IL -6 expressions and levels of anti-npG IgA, anti-tTG IgA, anti-eTG IgA in DH. However, the IL -6 expression level was significantly lower than that of NE.

Conclusions

The lack of correlations suggested no substantial interactions between IL -6, NE, IgA/npG, IgA/tTG or IgA/eTG in DH. Presented results might indicate the heterogenetic nature of DH pathogenesis suggesting further that both autoimmune and autoinflammatory phenomena may be involved in DH cutaneous pathology.

Simtomax, a novel point of care test for coeliac disease

INTRODUCTION

Coeliac disease is an autoimmune condition resulting from an abnormal reaction to dietary gluten leading to small bowel villous atrophy. International prevalence studies suggest that coeliac disease affects 1% of the adult population. However, despite its high prevalence, large numbers of patients go undiagnosed. One method of increasing detection rates would be to introduce a quick screening test in the form of a finger-prick blood test.

AREAS COVERED

There are currently four available point-of-care tests (POCTs) available for use by health professionals. This diagnostic evaluation will review the evidence for the use of POCTs in coeliac disease including Simtomax a novel test for deamidated gliadin peptides and total IgA level.

EXPERT OPINION

An accurate POCT has the potential to increase the rates of diagnosis of coeliac disease if used effectively as part of a case finding approach in primary or secondary care. Evidence for the use of Simtomax is currently fairly limited only drawing comparison with laboratory serology rather than the gold standard of histology and it has only been trialled in high-risk populations. However, results to date are encouraging and further research into this area is required.

A novel serogenetic approach determines the community prevalence of celiac disease and informs improved diagnostic pathways

BACKGROUND

Changing perspectives on the natural history of celiac disease (CD), new serology and genetic tests, and amended histological criteria for diagnosis cast doubt on past prevalence estimates for CD. We set out to establish a more accurate prevalence estimate for CD using a novel serogenetic approach.

METHODS

The human leukocyte antigen (HLA)-DQ genotype was determined in 356 patients with 'biopsy-confirmed' CD, and in two age-stratified, randomly selected community cohorts of 1,390 women and 1,158 men. Sera were screened for CD-specific serology.

RESULTS

Only five 'biopsy-confirmed' patients with CD did not possess the susceptibility alleles HLA-DQ2.5, DQ8, or DQ2.2, and four of these were misdiagnoses. HLA-DQ2.5, DQ8, or DQ2.2 was present in 56% of all women and men in the community cohorts. Transglutaminase (TG)-2 IgA and composite TG2/deamidated gliadin peptide (DGP) IgA/IgG were abnormal in 4.6% and 5.6%, respectively, of the community women and 6.9% and 6.9%, respectively, of the community men, but in the screen-positive group, only 71% and 75%, respectively, of women and 65% and 63%, respectively, of men possessed HLA-DQ2.5, DQ8, or DQ2.2. Medical review was possible for 41% of seropositive women and 50% of seropositive men, and led to biopsy-confirmed CD in 10 women (0.7%) and 6 men (0.5%), but based on relative risk for HLA-DQ2.5, DQ8, or DQ2.2 in all TG2 IgA or TG2/DGP IgA/IgG screen-positive subjects, CD affected 1.3% or 1.9%, respectively, of females and 1.3% or 1.2%, respectively, of men. Serogenetic data from these community cohorts indicated that testing screen positives for HLA-DQ, or carrying out HLA-DQ and further serology, could have reduced unnecessary gastroscopies due to false-positive serology by at least 40% and by over 70%, respectively.

CONCLUSIONS

Screening with TG2 IgA serology and requiring biopsy confirmation caused the community prevalence of CD to be substantially underestimated. Testing for HLA-DQ genes and confirmatory serology could reduce the numbers of unnecessary gastroscopies.

Diagnostic accuracy of a new point-of-care screening assay for celiac disease

AIM: To determine the diagnostic accuracy of a new point-of-care assay detecting anti-deamidated gliadin peptides in celiac disease (CD) patients.

METHODS: One-hundred-and-twelve patients (age range: 1.8-79.2 years old) with clinical symptoms suggestive of CD and/or first-degree relatives (FDR) of CD patients (n = 66), and confirmed CD on a gluten-free diet (GFD) (n = 46), were prospectively enrolled in the study at Gastroenterology outpatient clinics for adult patients and from the Gastroenterology Consultation Ward at the Pediatric Department of the University Hospital of Geneva. Written informed consent was obtained from all subjects enrolled. The study received approval from the local ethics committee. The original CD diagnosis had been based on serum-positive IgA anti-tissue transglutaminase enzyme-linked immunosorbent assay (ELISA) (QuantaLite™, Inova Diagnostics, San Diego, CA, United States) and on biopsy results. Serum samples from all study participants were tested by the new CD lateral flow immunochromatographic assay (CD-LFIA) device, Simtomax^® Blood Drop (Augurix SA, BioArk, Monthey, Switzerland) to detect immunoglobulin (Ig)A and IgG antibodies against deamidated gliadin peptides. The diagnostic performance was evaluated using receiver operating characteristic curves with 95%CIs. A cut-off of 2 on the Rann colorimetric scale was used to calculate the device’s sensitivity and specificity.

RESULTS: CD-LFIA was highly accurate in detecting untreated celiac patients. In the group of patients with CD symptoms and/or FDR, eight new cases of CD were detected by ELISA and biopsy. All of these new cases were also correctly identified by CD-LFIA. The test yielded four false positive and four false negative results. The false positive results were all within the groups with clinical symptoms suggestive of CD and/or FDR, whereas the false negative results were all within the GFD group. The test yeld a sensitivity of 78.9% (95%CI: 54.4-93.9) and specificity of 95.7% (95%CI: 89.4-98.8), and the area under the curve reached 0.893 (95%CI: 0.798-0.988). The Kappa coefficient, calculated according to the values obtained by two readers from the same device, was of 0.96 (SE: 0.06). When the GFD patients were excluded from the analysis, the area under the curve reached 0.989 (95%CI: 0.971-1.000) and the Kappa coefficient, calculated according to the values obtained by two readers from the same device, became 0.96 (SE: 0.07). Furthermore, using the Rann scale cut-off of 2 without the GFD patients, sensitivity was 100% and specificity was 93.1% (95%CI: 83.3-98.1).

CONCLUSION: The new CD-LFIA rapid screening test shows good diagnostic accuracy, sensitivity and specificity, and may rule out CD in patients with CD-related symptoms.

Markers of Celiac Disease and Gluten Sensitivity in Children with Autism

OBJECTIVE

Gastrointestinal symptoms are a common feature in children with autism, drawing attention to a potential association with celiac disease or gluten sensitivity. However, studies to date regarding the immune response to gluten in autism and its association with celiac disease have been inconsistent. The aim of this study was to assess immune reactivity to gluten in pediatric patients diagnosed with autism according to strict criteria and to evaluate the potential link between autism and celiac disease.

METHODS

Study participants included children (with or without gastrointestinal symptoms) diagnosed with autism according to both the Autism Diagnostic Observation Schedule (ADOS) and the Autism Diagnostic Interview, Revised (ADI-R) (n = 37), their unaffected siblings (n = 27), and age-matched healthy controls (n = 76). Serum specimens were tested for antibodies to native gliadin, deamidated gliadin, and transglutaminase 2 (TG2). Affected children were genotyped for celiac disease associated HLA-DQ2 and -DQ8 alleles.

RESULTS

Children with autism had significantly higher levels of IgG antibody to gliadin compared with unrelated healthy controls (p<0.01). The IgG levels were also higher compared to the unaffected siblings, but did not reach statistical significance. The IgG anti-gliadin antibody response was significantly greater in the autistic children with gastrointestinal symptoms in comparison to those without them (p<0.01). There was no difference in IgA response to gliadin across groups. The levels of celiac disease-specific serologic markers, i.e., antibodies to deamidated gliadin and TG2, did not differ between patients and controls. An association between increased anti-gliadin antibody and presence of HLA-DQ2 and/or -DQ8 was not observed.

CONCLUSIONS

A subset of children with autism displays increased immune reactivity to gluten, the mechanism of which appears to be distinct from that in celiac disease. The increased anti-gliadin antibody response and its association with GI symptoms points to a potential mechanism involving immunologic and/or intestinal permeability abnormalities in affected children.

Testing for antireticulin antibodies in patients with celiac disease is obsolete: a review of recommendations for serologic screening and the literature

Celiac disease (CD) is an autoimmune disorder that occurs in genetically susceptible individuals of all ages and is triggered by immune response to gluten and related proteins. The disease is characterized by the presence of HLA-DQ2 and/or -DQ8 haplotypes, diverse clinical manifestations, gluten-sensitive enteropathy, and production of several autoantibodies of which endomysial, tissue transglutaminase, and deamidated gliadin peptide antibodies are considered specific. Although antireticulin antibodies (ARA) have historically been used in the evaluation of CD, these assays lack optimal sensitivities and specificities for routine diagnostic use. This minireview highlights the advances in CD-specific serologic testing and the rationale for eliminating ARA from CD evaluation consistent with recommendations for diagnosis.

Intestinal biopsy is not always required to diagnose celiac disease: a retrospective analysis of combined antibody tests

Background

The objective of this study was to compare celiac disease (CD)– specific antibody tests to determine if they could replace jejunal biopsy in patients with a high pretest probability of CD.

Methods

This retrospective study included sera from 149 CD patients and 119 controls, all with intestinal biopsy. All samples were analyzed for IgA and IgG antibodies against native gliadin (ngli) and deamidated gliadin peptides (dpgli), as well as for IgA antibodies against tissue transglutaminase and endomysium.

Results

Tests for dpgli were superior to ngli for IgG antibody determination: 68% vs. 92% specificity and 79% vs. 85% sensitivity for ngli and dpgli, respectively. Positive (76% vs. 93%) and negative (72% vs. 83%) predictive values were also higher for dpgli than for ngli. Regarding IgA gliadin antibody determination, sensitivity improved from 61% to 78% with dpgli, while specificity and positive predictive value remained at 97% (P < 0.00001). A combination of four tests (IgA anti-dpgli, IgG anti-dpgli, IgA anti- tissue transglutaminase, and IgA anti-endomysium) yielded positive and negative predictive values of 99% and 100%, respectively and a likelihood ratio positive of 86 with a likelihood ratio negative of 0.00. Omitting the endomysium antibody determination still yielded positive and negative predictive values of 99% and 98%, respectively and a likelihood ratio positive of 87 with a likelihood ratio negative of 0.01.

Conclusion

Antibody tests for dpgli yielded superior results compared with ngli. A combination of three or four antibody tests including IgA anti-tissue transglutaminase and/or IgA anti- endomysium permitted diagnosis or exclusion of CD without intestinal biopsy in a high proportion of patients (78%). Jejunal biopsy would be necessary in patients with discordant antibody results (22%). With this two-step procedure, only patients with no CD-specific antibodies would be missed.

Performance of anti-deamidated gliadin peptides antibodies in celiac disease diagnosis

OBJECTIVES

To assess the usefulness of anti-deamidated gliadin peptides antibodies (a-DGP), in the diagnostic of celiac disease (CD).

PATIENTS AND METHODS

One hundred and three untreated CD patients (67 children and 36 adults) and 36 celiac patients under gluten-free diet were studied. Two hundred and seventy-four subjects served as controls (114 healthy blood donors, 80 healthy children and 80 patients with primary biliary cirrhosis). a-DGP (IgG and IgA) and anti-tissue transglutaminase antibodies (AtTG) were detected by enzyme-linked immunosorbent assay (Elisa). Anti-endomysium antibodies (AEA) were detected by indirect immunofluorescence on human umbilical cord.

RESULTS

The sensitivitiy of IgG and IgA a-DGP were 94% and 97% respectively, compared to 96% for AEA and AtTG. The specificity of a-DGP was 93.6% for IgG and 92% for IgA. The specificity of AEA and AtTG were 100%. The frequency of IgG and IgA a-DGP was significantly higher in patients with CD than in control group (94% vs. 4.4%, P<10(-7); 97% vs. 8%, P<10(-7)). The frequency of IgG a-DGP was the same in children and adult (94%). The frequency of IgA a-DGP were similar in children and adults (95.5% vs. 100%).

CONCLUSION

Our study shows that a-DGP increases neither the sensitivity nor the specificity of AEA and AtTG.

Evaluation of a point-of-care test based on deamidated gliadin peptides for celiac disease screening in a large pediatric population

OBJECTIVES

Celiac disease (CD) is nowadays known to be a common chronic enteropathy that is becoming a growing public health concern. Yet, it is estimated that more than 90% of patients remain undiagnosed. A point-of-care diagnostic test can be a rapid and cost-effective solution in the first-line screening of CD. The aim of this study is to evaluate the performance of a novel point-of-care screening test in a large pediatric population.

MATERIALS AND METHODS

Serum samples were collected from a cohort of 250 children presenting either an increased risk or a clinical suspicion of CD. All sera were tested using the point-of-care test detecting IgA and IgG antibodies against a combination of three different deamidated gliadin peptides as well as total IgA. The results of the screening test were compared with an enzyme-linked tissue transglutaminase immunosorbent assay and with histology resulting from intestinal biopsies performed in patients with elevated titers of antitissue transglutaminase antibodies.

RESULTS

The point-of-care test showed highly concordant results with the laboratory immunoassay, yielding a sensitivity of 93.1 (78-98.1%) and a specificity of 95% (91.2-97.2%), with a diagnostic accuracy of 94.8% (91.3-96.9%) and a negative predictive value of 99.1% (96.6-99.7%). The screening test identified all patients with celiac-type histology findings on biopsy, as well as all patients with concomitant IgA deficiency.

CONCLUSION

With a high diagnostic accuracy, this novel point-of-care approach is an efficient tool for CD case finding in pediatric populations. It has the potential to improve the management of celiac patients in primary care by providing faster counseling and treatment.

Diagnosis of celiac disease

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

Diagnostic value of anti-deamidated gliadin peptide IgG antibodies for celiac disease in children and IgA-deficient patients

OBJECTIVES

The aim of the study was to analyze the diagnostic performance of anti-deamidated gliadin peptide (dGp) immunoglobulin (Ig) G and IgA regarding the age at celiac disease (CD) diagnosis and the anti-dGp IgG usefulness for diagnosing CD IgA-deficient patients.

METHODS

Anti-dGp IgG and IgA and anti-native gliadin (nGlia) IgA were determined by enzyme fluoroimmunoassay in 100 newly diagnosed anti-tissue transglutaminase (tTG) IgA-positive pediatric and adult patients with CD and in 100 age-matched patients with other digestive pathologies. Anti-dGp IgG was evaluated in 6 CD IgA-deficient patients.

RESULTS

When analyzing all of the patients, the anti-dGp IgG assay showed higher diagnostic accuracy (area under receiver operating characteristic curve), specificity, and positive predictive value than anti-dGp IgA and anti-nGlia IgA. All of the diagnostic parameters corresponding to anti-dGp IgG reached the same values as anti-tTG IgA in children 7 years or younger. In older patients, both anti-dGp isotypes showed an inverse behavior, IgG having a higher specificity and positive predictive value but a lower sensitivity and negative predictive value than IgA. Anti-dGp levels were associated with the severity of intestinal lesions, and an inverse association was found regarding age at diagnosis. Both anti-dGp IgG and IgA were found to be positive in the 9 patients with minimal intestinal changes included in the study. All of the patients with CD with IgA deficiency were positive for anti-dGp IgG.

CONCLUSIONS

The diagnostic performance of anti-dGp depends on the antibody isotype and on the age at CD diagnosis, anti-dGp IgG being a serological marker at least as useful as anti-tTG IgA for detecting CD in children ages 7 years or younger. Our data also indicate that anti-dGp IgG can improve the diagnosis of IgA-deficient patients.

IgA antibodies against deamidated gliadin peptides in patients with chronic liver diseases

BACKGROUND/AIMS

IgA antibodies against tissue-transglutaminase (anti-tTG-IgA) and IgA and IgG antibodies against deamidated gliadin peptides (anti-DGP-IgA and anti-DGP-IgG) are considered specific for celiac disease (CD) whereas, patients with chronic liver disorders have an increased risk of latent CD development. We investigated the prevalence and clinical significance of anti-DGP-IgA, anti-DGP-IgG and anti-tTG-IgA in a large cohort of patients with chronic liver diseases.

METHODS

668 patients without gastrointestinal symptoms (426 viral hepatitis, 94 autoimmune liver diseases, 61 alcoholic disease, 46 non-alcoholic fatty liver disease, 41 with other liver disorders) were investigated by ELISAs (INOVA Diagnostics). Patients positive for at least one autoantibody invited for a small-intestinal biopsy and HLA-DQ typing.

RESULTS

Anti-DGP-IgA were detected in 8.5%, anti-DGP-IgG in only one (0.15%, P<0.001) and anti-tTG-IgA in 5.8% of patients (P=0.05). Fifty-two were anti-DGP-IgA(+)/anti-tTG-IgA(-), 34 anti-DGP-IgA(-)/anti-tTG-IgA(+), and 5 anti-DGP-IgA(+)/anti-tTG-IgA(+). Anti-DGP-IgA positivity was associated with older age (P<0.05), cirrhosis (P<0.05) and increased IgA (P<0.05) whereas, anti-tTG-IgA only with cirrhosis (P<0.05). Histology and HLA-typing compatible with CD was revealed in 4/14 anti-DGP-IgA(+)/anti-tTG-IgA(-), 0/13 anti-DGP-IgA(-)/anti-tTG-IgA(+) and 2/2 anti-DGP-IgA(+)/anti-tTG-IgA(+). All 6 patients diagnosed with CD were anti-DGP-IgA(+) and only 2 anti-tTG-IgA(+).

CONCLUSIONS

Although a significant number of patients had detectable CD-related autoantibodies, anti-DGP-IgA test seems better than anti-tTG-IgA for unmasking occult forms of CD in patients with chronic liver disorders. The known good performance for CD diagnosis of anti-DGP-IgG test was not confirmed in this specific group of patients.

A study of circulating gliadin antibodies in schizophrenia among a Chinese population

The present work measured circulating antibodies against native gliadins, deamidated gliadin-derived epitopes, and transglutaminase 2 (TGM2) in 473 patients with schizophrenia and 478 control subjects among a Chinese population. The results showed that 27.1% of patients with schizophrenia were positive for the IgA antibody against native gliadins compared with 17.8% of control subjects (χ(2) = 11.52, P = .0007, OR = 1.72, 95% CI 1.25-2.35), although this significant difference appeared to be due mainly to low IgA gliadin antibody levels in female controls. A total of 27.6% of female patients were positive for IgA gliadin antibodies compared with 13.9% of female controls (χ(2) = 10.46, P = .0012, OR = 2.36, 95% CI 1.39-4.01), and 26.4% of male patients were positive for IgA antibodies compared with 19.8% of male controls (χ(2) = 3.26, P = .071, OR = 1.46, 95% CI 0.97-2.19). Of 128 patients who were positive for the IgA antibody against native gliadins, 8 were positive for the IgA antibody against deamidated gliadin epitopes and 1 was positive for IgA anti-TGM2 antibody. However, quantitative analysis demonstrated that the mean levels of IgA antibodies against deamidated gliadin epitopes and TGM2 were significantly lower in patients with schizophrenia than the control subjects (P < .001 and P = .008, respectively). The prevalence of IgG antibodies against native gliadins was not significantly different between the patient group and the control group (χ(2) = 2.25, P = .134, OR = 1.32, 95% CI 0.92-1.88). This study suggests that specific gliadin-derived epitopes may be involved in schizophrenia.

Association between levels of IgA antibodies to tissue transglutaminase and gliadin-related nonapeptides in dermatitis herpetiformis

Dermatitis herpetiformis (DH) is an autoimmunity-driven inflammatory blistering dermatosis associated with a gluten-dependent enteropathy. Tissue transglutaminase (tTG) and nonapeptides of gliadin (npG) are considered in its pathomechanism/diagnostics. Here, the diagnostic accuracy of anti-tTG/anti-npG IgA ELISAs in Slavic DH patients with active skin rash was assessed through creating receiver operating characteristic (ROC) curves, determining cutoff values, and calculating correlations between levels of anti-tTG/anti-npG IgA in DH, IgA/neutrophil-mediated non-DH patients and healthy persons. Altogether, sera from 80 Slavic individuals were examined. There were negligible differences between cutoff points obtained by the ELISAs manufacturer and those in this study. There were statistically significant correlations between levels of anti-tTG/anti-npG IgA in both DH group and the group of IgA/neutrophil-mediated non-DH dermatoses. There was no such correlation in healthy controls. It seems that IgA autoantibodies to tTG and npG in the IgA/neutrophil-mediated DH are produced in the coordinated way implying their causal relationship.