Serologic Diagnosis of Celiac Disease: New Biomarkers

The Frequently Used Industrial Food Process Additive, Microbial Transglutaminase: Boon or Bane

Microbial transglutaminase (mTG) is a frequently consumed processed food additive, and use of its cross-linked complexes is expanding rapidly. It was designated as a processing aid and was granted the generally recognized as safe (GRAS) classification decades ago, thus avoiding thorough assessment according to current criteria of toxicity and public health safety. In contrast to the manufacturer's declarations and claims, mTG and/or its transamidated complexes are proinflammatory, immunogenic, allergenic, pathogenic, and potentially toxic, hence raising concerns for public health. Being a member of the transglutaminase family and functionally imitating the tissue transglutaminase, mTG was recently identified as a potential inducer of celiac disease. Microbial transglutaminase and its docked complexes have numerous detrimental effects. Those harmful aspects are denied by the manufacturers, who claim the enzyme is deactivated when heated or by gastric acidity, and that its covalently linked isopeptide bonds are safe. The present narrative review describes the potential side effects of mTG, highlighting its thermostability and activity over a broad pH range, thus, challenging the manufacturers' and distributers' safety claims. The national food regulatory authorities and the scientific community are urged to reevaluate mTG's GRAS status, prioritizing public health protection against the possible risks associated with this enzyme and its health-damaging consequences.

Dynamics of Serologic Change to Gluten in Celiac Disease Patients

Serologic measures of tissue transglutaminase (tTG) immunoglobulin A (IgA) and deamidated gliadin peptide (DGP) IgA and immunoglobulin G (IgG) are hallmark tests utilized when diagnosing individuals for celiac disease (CeD) and for monitoring adherence to a gluten-free diet (GFD), currently the only available treatment for CeD. We address two issues in this study: (i) the relapse to seropositivity for CeD patients who resume a gluten containing diet and (ii) the correlation between two different tTG-IgA assays near the upper limit of normal (ULN) designated thresholds. Regarding the first issue, often a suspected CeD individual is put back on a gluten diet to return to their serologic levels. However, we show it requires a substantial amount of gluten for serology to return to a positive level. For example, in one study of 22 patients treated with placebo and taking 84 g of gluten over 6 weeks, only two converted from seronegative to seropositive for tTG-IgA. Regarding the second topic, we compare the relationship for different serologic assays, namely tTG-IgA AB (recombinant, ULN = 4 units/mL) vs. tTG-IgA (non-recombinant, ULN = 20 units). There is a strong correlation between both measurements as evidenced by a Pearson coefficient of R = 0.8584; however, we observed that the cross-correlation in terms of sensitivity and specificity improved substantially by using an ULN value of three instead of four for the tTG-IgA AB (recombinant) assay. This result suggests that assay thresholds used for initial diagnosis in patients who have not yet started a GFD may need to be adjusted for monitoring and in the setting of a diagnostic gluten challenge.

Cross-reactivity and sequence similarity between microbial transglutaminase and human tissue antigens

Microbial transglutaminase (mTG) is a bacterial survival factor, frequently used as a food additive to glue processed nutrients. As a result, new immunogenic epitopes are generated that might drive autoimmunity. Presently, its contribution to autoimmunity through epitope similarity and cross-reactivity was investigated. Emboss Matcher was used to perform sequence alignment between mTG and various antigens implicated in many autoimmune diseases. Monoclonal and polyclonal antibodies made specifically against mTG were applied to 77 different human tissue antigens using ELISA. Six antigens were detected to share significant homology with mTG immunogenic sequences, representing major targets of common autoimmune conditions. Polyclonal antibody to mTG reacted significantly with 17 out of 77 tissue antigens. This reaction was most pronounced with mitochondrial M2, ANA, and extractable nuclear antigens. The results indicate that sequence similarity and cross-reactivity between mTG and various tissue antigens are possible, supporting the relationship between mTG and the development of autoimmune disorders 150W.

Beneficial Role of Microbial Transglutaminase in the Pathogenetic Mechanisms of Coeliac Disease

Coeliac disease (CD) is caused by immunological intolerance to wheat gluten and related proteins of rye and barley. Consequently, gluten-free (GF) products have been developed but technological implementation is required to improve their intrinsic rheological properties. One alternative for increasing the functional properties of GF foodstuff is the incorporation of microbial transglutaminase (mTG), which allows for the cross-linking of proteins that can substitute for the gluten network in the bakery industry. mTG has been, however, suggested to mimic tissue transglutaminase and to be immunogenic in CD patients. Recently, both mTG and gliadin were found to be transported to the endoplasmic reticulum of enterocytes, suggesting cross-presentation and potential interaction with immune cells in CD. Although pathogenetic activity of mTG has not been found to date, these data naturally raise concerns among clinicians and patients about the use of mTG as a food additive. On the contrary, different studies have shown that treatment with mTG was effective in reducing the inflammatory immune response of gluten in CD. In this article, we take advantage of recent advances in gut physiology and CD pathogenesis to revise the literature data on mTG. An updated and unbiased overview of the role of mTG in this pathology allowed us to definitively highlight the beneficial use of this food additive by CD patients.

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.

Celiac Disease in Juvenile Idiopathic Arthritis and Other Pediatric Rheumatic Disorders

Celiac Disease (CD) is an immune-mediated and gluten-related disorder whose prevalence is higher in children affected with other autoimmune disorders, including diabetes mellitus type 1, autoimmune thyroiditis, and others. As regards Juvenile Idiopathic Arthritis (JIA) and other pediatric rheumatic disorders, there is no clear recommendation for CD serological screening. In this review, we analyze all the available clinical studies investigating CD among children with JIA (and other rheumatic diseases), in order to provide objective data to better understand the necessity of CD serological screening during the follow-up. Based on the present literature review and analysis, >2.5% patients with JIA were diagnosed with CD; however, the CD prevalence in JIA patients may be even higher (>3–3.5%) due to several study limitations that could have underestimated CD diagnosis to a variable extent. Therefore, serological screening for CD in children affected with JIA could be recommended due to the increased CD prevalence in these patients (compared to the general pediatric population), and because these JIA patients diagnosed with CD were mostly asymptomatic. However, further research is needed to establish a cost-effective approach in terms of CD screening frequency and modalities during the follow-up for JIA patients. Conversely, at the moment, there is no evidence supporting a periodical CD screening in children affected with other rheumatic diseases (including pediatric systemic lupus erythematosus, juvenile dermatomyositis, and systemic sclerosis).

Reliability of the Multiplex CytoBead CeliAK Immunoassay to Assess Anti-tTG IgA for Celiac Disease Screening

Background and Objective: The diagnosis of Celiac Disease (CD) is first based on the positivity for specific serological markers. The CytoBead CeliAK immunoassay simultaneously measures antibodies (IgA) directed to tissue transglutaminase (tTG), endomysium (EMA), and deamidated gliadin (DG), in addition to providing a control for total IgA levels. The aim of this study is to assess the reliability of this multiplex assay to detect anti-tTG IgA positive patients, compared with a conventional single-parameter enzyme-linked immunosorbent assay (ELISA).

Methods: Serum samples from 149 pediatric patients were assessed by both CytoBead CeliAK immunoassay and ELISA, in order to evaluate their concordance for the measurement of anti-tTG IgA.

Results: The measurement of anti-tTG IgA by CytoBead CeliAK immunoassay basically showed a complete concordance rate with the conventional and single-parameter ELISA, according to the respective cutoff values (3 U/ml and 10 U/ml).

Conclusions: Our comparative analysis demonstrates a substantial equivalency between multiplex CytoBead CeliAK assay and the single-parameter conventional ELISA to assess anti-tTG IgA antibody in the context of the screening for CD in children. Importantly, CytoBead CeliAK assay could present some preanalytic, analytic, and economic advantages.

Microbial Transglutaminase Is a Very Frequently Used Food Additive and Is a Potential Inducer of Autoimmune/Neurodegenerative Diseases

Microbial transglutaminase (mTG) is a heavily used food additive and its industrial transamidated complexes usage is rising rapidly. It was classified as a processing aid and was granted the GRAS (generally recognized as safe) definition, thus escaping full and thorough toxic and safety evaluations. Despite the manufacturers claims, mTG or its cross-linked compounds are immunogenic, pathogenic, proinflammatory, allergenic and toxic, and pose a risk to public health. The enzyme is a member of the transglutaminase family and imitates the posttranslational modification of gluten, by the tissue transglutaminase, which is the autoantigen of celiac disease. The deamidated and transamidated gliadin peptides lose their tolerance and induce the gluten enteropathy. Microbial transglutaminase and its complexes increase intestinal permeability, suppresses enteric protective pathways, enhances microbial growth and gliadin peptide's epithelial uptake and can transcytose intra-enterocytically to face the sub-epithelial immune cells. The present review updates on the potentially detrimental side effects of mTG, aiming to interest the scientific community, induce food regulatory authorities' debates on its safety, and protect the public from the mTG unwanted effects.

Alpha-enolase involvement in intestinal and extraintestinal manifestations of celiac disease

Celiac disease is a life-long intestinal autoimmune disease, characterized by the gluten intolerance and chronic enteric inflammation. Traditionally presented by intestinal manifestations, however, a shift toward extra intestinal presentation is taking place. One of the affected organs is the nervous systems presented by neuropsychiatric manifestations, hence the mechanism and pathways are not clear. The presence of neuronal and alpha-enolases and their corresponding antibodies were noticed in the mucosa and serum of celiac disease patients, as well as in other various autoimmune diseases with psycho-neurological manifestations. The aims of the present review are to screen the literature on different isoforms of enolase, mainly alpha enolase, and their specific antibodies and to suggest their potential pathophysiological mechanisms relaying the enolases to intestinal or extraintestinal celiac disease manifestations. The shared aspects between the enolases and celiac disease and the cross-talks between alpha-enolase and tissue transglutaminase suggest new potential pathophysiological mechanisms that might drive celiac disease evolvement.

Wait-and-See Approach or Gluten-Free Diet Administration-The Rational Management of Potential Coeliac Disease

Potential celiac disease (PCD) is a heterogeneous disease; only some patients develop full celiac disease (CD), characterised by advanced atrophic changes in the small intestine. Few accurate prognostic factors exist for the progression of PCD; therefore, therapeutic decisions should be made on an individual basis in each case. Patients with clinical gastroenterological or parenteral symptoms often benefit from a gluten-free diet, and those left on a diet containing gluten should receive clinical, serological and histopathological supervision.

Deamidated gliadin peptide and tissue transglutaminase antibodies in children with coeliac disease: A correlation study

BACKGROUND AND STUDY AIMS

Serological tests for coeliac disease (CD) are important in the clinical diagnosis and monitoring of response to a gluten free diet (GFD). The tests differ in their sensitivity, specificity, and diagnostic accuracy. In this study, tissue transglutaminase (IgA) (tTG-IgA) antibody was compared with the deamidated gliadin peptide (DGP), of both IgG (DGP-IgG) and IgA (DGP-IgA) types, in patients with CD.

PATIENTS AND METHODS

This cross-sectional study was conducted over a period of 2 years, between 2016 and 2018, at King Abdulaziz University Hospital in children 18 years of age or younger with biopsy-proven CD. Patients' sera were tested for DGP-IgA, DGP-IgG, and tTG-IgA antibodies using enzyme-linked immunosorbent assay (ELISA). A Pearson correlation coefficient and Cohen's kappa coefficient were performed to analyse the serological tests.

RESULTS

The study included 26 patients with CD, with a median age of 15 years (range, 5-18 years). Seventeen patients (65.4%) were males. The median disease duration was 5 years (range, 3-14 years). Fifteen patients (57.7%) reported good adherence to a GFD. The patients' serological tests showed a mean ± SD tTG-IgA titer of 149.8 ± 75 u/ml, a mean DGP-IgG titer of 62.5 ± 36.5, and a mean DGP-IgA of 32 ± 23.3 μ/ml. We found a significant correlation between tTG-IgA and DGP-IgG (r = 0.69, P < 0.001), tTG-IgA and DGP-IgA (r = 0.67, P < 0.001), and DGP-IgG and DGP-IgA (r = 0.83, P < 0.001). Cohen's kappa coefficient (k) showed substantial agreement between tTG-IgA and DGP-IgG (k = 0.71, P < 0.001) and DGP-IgG and DGP-IgA (k = 0.69, P < 0.001), but moderate agreement between tTG-IgA and DGP-IgA (k = 0.45, P = 0.006).

CONCLUSION

We found a good correlation between tTG-IgA and DGP-IgG and tTG-IgA and DGP-IgA, and substantial agreement between tTG-IgA and DGP-IgG, but moderate agreement between tTG-IgA and DGP-IgA. These results indicate that DGP-IgG was comparable to tTG-IgA and may be useful as an alternative to tTG-IgA in the diagnosis and follow-up of patients with CD.

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.

Processed Food Additive Microbial Transglutaminase and Its Cross-Linked Gliadin Complexes Are Potential Public Health Concerns in Celiac Disease

Microbial transglutaminase (mTG) is a survival factor for microbes, but yeasts, fungi, and plants also produce transglutaminase. mTG is a cross-linker that is heavily consumed as a protein glue in multiple processed food industries. According to the manufacturers' claims, microbial transglutaminase and its cross-linked products are safe, i.e., nonallergenic, nonimmunogenic, and nonpathogenic. The regulatory authorities declare it as "generally recognized as safe" for public users. However, scientific observations are accumulating concerning its undesirable effects on human health. Functionally, mTG imitates its family member, tissue transglutaminase, which is the autoantigen of celiac disease. Both these transglutaminases mediate cross-linked complexes, which are immunogenic in celiac patients. The enzyme enhances intestinal permeability, suppresses mechanical (mucus) and immunological (anti phagocytic) enteric protective barriers, stimulates luminal bacterial growth, and augments the uptake of gliadin peptide. mTG and gliadin molecules are cotranscytosed through the enterocytes and deposited subepithelially. Moreover, mucosal dendritic cell surface transglutaminase induces gliadin endocytosis, and the enzyme-treated wheat products are immunoreactive in CD patients. The present review summarizes and updates the potentially detrimental effects of mTG, aiming to stimulate scientific and regulatory debates on its safety, to protect the public from the enzyme's unwanted effects.