Antigliadin antibodies detected by enzyme-linked immunosorbent assay as a marker of childhood celiac disease

Checkpoint Inhibitors and Induction of Celiac Disease-like Condition

Immune checkpoint inhibitors herald a new era in oncological therapy-resistant cancer, thus bringing hope for better outcomes and quality of life for patients. However, as with other medications, they are not without serious side effects over time. Despite this, their advantages outweigh their disadvantages. Understanding the adverse effects will help therapists locate, apprehend, treat, and perhaps diminish them. The major ones are termed immune-related adverse events (irAEs), representing their auto-immunogenic capacity. This narrative review concentrates on the immune checkpoint inhibitors induced celiac disease (CD), highlighting the importance of the costimulatory inhibitors in CD evolvement and suggesting several mechanisms for CD induction. Unraveling those cross-talks and pathways might reveal some new therapeutic strategies.

Candida albicans in celiac disease: A wolf in sheep's clothing

Candida albicans is a commensal fungus with a potential pathogenicity and celiac disease is an autoimmune condition. Both share multiple pathophysiological junctions, including serological markers against cell-wall proteins of Candida, anti-gliadin antibodies are positive in both entities, gluten and a candidal virulence factor share sequence similarity and the autoantigen of celiac disease, the tissue transglutaminase, is pivotal in Candida albicans commensalism and hostile behavior and its covalently cross linked products are stable and resistant to breakdown in the two entities. Those autoimmune/infectious cross roads are the basis for the hypothesis that Candida albicans is an additional environmental factor for celiac disease autoimmunogenesis.

Serologic Diagnosis of Celiac Disease: New Biomarkers

Most patients affected by celiac disease (CD) are asymptomatic or hyposymptomatic and undiagnosed, and are at risk of preventable complications. Therefore, early diagnosis is highly recommended. Multiple diagnostic antibodies are available; the most frequently used is IgA to tissue transglutaminase (IgA-tTg). It may yield false results and, alone, does not address IgA deficiency. Recently, a new generation of anti-neo-epitope tTg check (IgG + IgA) has become available. It is highly sensitive and specific, covers IgA-deficient patients with CD, reflects intestinal damage, and has predictive potential in the diagnosis of CD.

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.

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.

Serum antigliadin antibody levels as a screening criterion before jejunal biopsy indication for celiac disease in a developing country

The objective of the present study was to determine the efficacy of detection of antigliadin immunoglobulins G and A (IgG and IgA) for the diagnosis of celiac disease in a developing country, since other enteropathies might alter the levels of these antibodies. Three groups were studied: 22 patients with celiac disease (mean age: 30.6 months), 61 patients with other enteropathies (mean age: 43.3 months), and 46 patients without enteropathies (mean age: 96.9 months). Antigliadin IgG and IgA ELISA showed sensitivity of 90.9 and 95.5%, respectively. With the hypothetical values of prevalence ranging from 1:500 to 1:2000 liveborns, the positive predictive value varied from 8.5 to 2.3% for IgG and from 4.8 to 1.1% for IgA. Considering the patients without enteropathies, specificity was 97.8 and 95.7% for IgG and IgA, respectively. In patients with other enteropathies, specificity was 82.0 and 84.1%, respectively. When patients with and without other enteropathies were considered as a whole, specificity was 88.8 and 91.6%, respectively. The specificity of positive IgG or IgA was 93.5% in children without enteropathies and 78.7% in the presence of other enteropathies. The negative predictive value for hypothetical prevalences varying from 1:500 to 1:2000 liveborns was 99.9%. Thus, even in developing countries where the prevalence of non-celiac enteropathies is high, the determination of serum antigliadin antibody levels is a useful screening test prior to the jejunal biopsy in the investigation of intestinal malabsorption.

Biochemical tests in diseases of the intestinal tract: their contributions to diagnosis, management, and understanding the pathophysiology of specific disease states

Biochemical testing plays a major role in the complete evaluation of patients with suspected or established intestinal disease. We have classified these tests according to the medium in which they are performed: breath tests, including isotopic and nonisotopic tests, fecal tests, urine tests, serum tests, tissue tests, and other tests. The principles of various tests are outlined, and the role of each test in the evaluation of particular gastrointestinal disorders is discussed.

Reliability of immunologic markers of celiac sprue in the assessment of mucosal recovery after gluten withdrawal

We studied 47 adults (21 men, 26 women), with biopsy-proven celiac sprue and anti-endomysin antibody (EmA) positivity while untreated, to evaluate the usefulness of both serologic markers of celiac sprue [i.e., immunoglobulin A (IgA)-EmA and total Ig-anti-gliadin (AGA) antibodies] and of a detailed dietary inquiry in predicting the mucosal pattern after gluten withdrawal. A second biopsy was repeated 8-30 months after beginning a gluten-free diet, along with EmA and AGA determinations and the dietary inquiry. Both EmA and AGA were appraised by indirect immunofluorescence on monkey esophagus and rat kidney, respectively. Intestinal biopsy was graded according to Cooke's criteria. After gluten withdrawal, intestinal mucosa reverted to normal in only nine patients. Both EmA and AGA showed high positive but low negative predictive values on intestinal histologic outcome. The positive predictive value of admission of dietary lapses was 100%, whereas the negative predictive value was 39.1%. Neither serologic markers nor dietary inquiries are to be regarded as reliable predictors of intestinal outcome after a gluten-free diet. Biopsy remains the best means of ascertaining mucosal recovery.

IgA antiendomysium antibodies have a high positive predictive value for celiac disease in asymptomatic patients

Many attempts have been made to find screening tests for celiac disease to reduce the need for biopsy, or to achieve better selection criteria before intestinal biopsy. We have recently analyzed apparently healthy blood donors for antigliadin antibodies (AGA) to select subjects for further gastrointestinal investigation. A prevalence of gluten enteropathy of at least 1/256 was found in this population. The positive predictive value (+PV), however, was only 20%. In the present study we have analyzed IgA antiendomysium antibodies (IgA-EmA) to estimate the sensitivity and specificity of the test, and determine whether or not the +PV of the assay increases when screening for adult celiac disease in an asymptomatic population. We found that asymptomatic persons with celiac disease may have IgA-EmA. We found a 100% specificity of IgA-EmA in the tested population of blood donors, whereas the sensitivity was about the same as that of IgA-AGA. This result of a +PV of 100% indicates that a positive IgA-EmA could replace biopsy in diagnosing celiac disease. However, further extended studies are needed to determine whether this is applicable in other populations. To screen patients for celiac disease, we recommend the easy and cheap IgA-AGA assay as a preliminary test and the IgA-EmA to verify the diagnosis and avoid unnecessary biopsies.

Immunological diagnosis of childhood coeliac disease: comparison between antigliadin, antireticulin and antiendomysial antibodies

The immunological markers proposed to supplement intestinal biopsy for the diagnosis of coeliac disease are antigliadin, antireticulin and antiendomysial antibodies. These antibodies have been studied separately or compared as pairs, but no prospective comparison of all three antibodies in childhood coeliac disease exists. Thirty-four confirmed coeliacs were compared with nine non-coeliacs with pathological small intestines, and 32 children with a normal intestinal histology. Sera were examined for IgG- and IgA-antigliadin antibodies (AGA) by ELISA, and for IgA-antireticulin antibodies (ARA) and IgA endomysial antibodies (EMA) by indirect immunofluorescence. In active coeliac disease, IgA-EMA was the most sensitive (97%), while IgA-AGA the least sensitive antibody (52%). The specificity of IgA-AGA, IgG-AGA, IgA-ARA, IgA-EMA was 95%, 92%, 100% and 98%, respectively. Positive predicted values of ARA and EMA were comparable (97-100%), while EMA had the highest negative predicted value (98%). Compared with IgG-AGA, IgA-EMA titres better reflected variations in dietary gluten, and correlated best with intestinal pathology. Compared with AGA and ARA sensitivity, specificity and predictive values, EMA is the most reliable serological marker for the diagnosis of coeliac disease. It reflects dietary changes in gluten and correlates best with intestinal histopathology. Therefore, it should be considered the best of the three serological tests available for childhood coeliac disease.

Food allergies in children

Ingested food represents the greatest foreign antigenic load that confronts the human immune system. In most individuals tolerance develops to food antigens that are continually gaining access to the body. When tolerance fails to develop, the immune system may react with a hypersensitivity reaction. Allergies to food affect up to 8% of children less than 3 years of age and 1% to 2% of the general population. Symptoms include the gastrointestinal, cutaneous, and respiratory symptoms, as well as systemic anaphylaxis with shock. Clinical investigations in the past have characterized the food hypersensitivity disorders, but our understanding of the basic immunopathologic mechanism remains incomplete. Current progress in allergen characterization and the rigorous scientific methods now being applied to this field by many investigators provide hope that new information regarding the pathogenesis of these disorders and new forms of therapy will soon become available. For now, practicing physicians must carefully diagnose specific food sensitivities and educate patients and their families in the elimination of the responsible food allergen.

Verification bias in pediatric studies evaluating diagnostic tests

Improperly designed evaluations of diagnostic tests may lead to inaccurate conclusions about a test's accuracy. One problem, verification bias, occurs if subjects are not equally likely to have the diagnosis verified by a gold-standard evaluation and if selection for further evaluation is dependent on the diagnostic test result. To determine whether verification bias is a problem in pediatric studies of diagnostic tests, we conducted a critical appraisal of all studies evaluating diagnostic tests published in three pediatric journals during a 3-year period. Thirty-six percent were subject to verification bias. The most prevalent cause was restriction of the patient sample to those whose diagnosis had been verified by a gold standard evaluation, when the decision to obtain the gold standard was influenced by the diagnostic test result. Verification bias may have serious effects on the estimated sensitivity and specificity of a test. Improved awareness of the potential for verification bias may help physicians improve their selection and interpretation of diagnostic tests and thereby improve the quality and efficiency of patient care.

Co-existence of coeliac disease and insulin-dependent diabetes mellitus in children: screening sera using an ELISA test for gliadin antibody

The prevalence of coeliac disease in children with insulin-dependent diabetes mellitus was investigated using a screening test of serum for antigliadin antibody by ELISA. One hundred and eighty (180) unselected diabetic children were screened for IgA and IgG class antigliadin antibodies (AGA); children with either grossly elevated or slightly elevated AGA had small bowel biopsies. The four children with the highest IgA AGA had total villous atrophy. These four children were considered to have unsuspected coeliac disease. The prevalence of coeliac disease in this group of children was one in 45. Anti-gliadin IgA and IgG tests are suitable for screening children at high risk of having coeliac disease.

Salivary IgA antigliadin antibody as a marker for coeliac disease

In recent years, serum antibodies to gliadin (AGA) have been reported to be useful markers of coeliac disease. IgA AGA have also been found in intestinal secretions and saliva in coeliac disease and may offer a convenient, non-invasive screening test. In order to test this hypothesis, salivary and serum AGA were measured in children with coeliac disease proved by biopsy and compared with several control groups. Measurement of salivary IgA AGA provided excellent discrimination between those children with coeliac disease and the control groups, and our study suggests that it may provide a rapid, non-invasive method of screening for this disease before intestinal biopsy.

Antibodies to gliadin in children with coeliac disease

We have measured antibodies to gliadin (AGA), bovine beta-lactoglobulin, and chicken egg ovalbumin with a four-layer solid phase radioimmunoassay (RIA) in 62 children and adolescents with coeliac disease and in 36 healthy controls. The geometric mean titre of IgG AGA in patients at initial diagnosis was more than 100-fold that of controls (p less than 0.0001). Even patients on gluten-free diet had significantly higher IgG AGA titres than the controls (p = 0.0001), the difference being more than 5-fold. All the 42 patients with active disease (30 at initial diagnosis and 12 after gluten challenge) had their IgG AGA titre above 1,000, as compared with 2 (5.7%) of the 35 controls (p less than 0.0001). Both IgG and IgA AGA were quite sensitive and specific in identifying children with coeliac disease; the sensitivities for IgG and IgA AGA were 100% and 95.2%, the specificities 94.3% and 97.2%, respectively. We conclude that determination of IgG and IgA AGA with RIA is suitable for monitoring dietary compliance in children with coeliac disease, and the method is sensitive and specific for screening for coeliac disease in children.

A reliable screening test for coeliac disease: enzyme-linked immunosorbent assay to detect anti-gliadin antibodies in serum

A simple, rapid, highly reproducible enzyme-linked immunosorbent assay detecting anti-gliadin antibodies in serum to screen for coeliac disease (CD) is described. By combining the results of anti-gliadin IgA and IgG determinations the overall sensitivity of the assay was found to be 100% and the specificity 96% for children and 99% for adults. Significantly elevated antigliadin IgA and IgG antibodies were detected in all 20 children and all 25 adults with untreated CD. False positive results were found in 1/79 histologically normal control and 5/86 disease control children, while for adults false positive rates were 0/74 and 1/34 for the healthy and disease control groups, respectively. Anti-gliadin IgA and IgG was measured in serum samples from 52 coeliac patients (11 children and 41 adults) treated with a gluten-free diet (GFD). Each of the children and 28 of the adults who followed a strict GFD had significantly lower IgA and IgG levels than untreated CD patients. The serum anti-gliadin IgA and IgG levels of the 13 adults not complying with a GFD were similar to those found for untreated CD patients. This assay is recommended as a screening test for CD as well as a tool for follow-up of treated patients.