Role of tissue transglutaminase in celiac disease

Respiratory syncytial virus infection induces the release of transglutaminase 2 from human airway epithelial cells

Respiratory syncytial virus (RSV) is an important human pathogen that causes severe lower respiratory tract infections in young children, the elderly, and the immunocompromised, yet no effective treatments or vaccines are available. The precise mechanism underlying RSV-induced acute airway disease and associated sequelae are not fully understood; however, early lung inflammatory and immune events are thought to play a major role in the outcome of the disease. Moreover, oxidative stress responses in the airways play a key role in the pathogenesis of RSV. Oxidative stress has been shown to elevate cytosolic calcium (Ca²⁺) levels, which in turn activate Ca²⁺-dependent enzymes, including transglutaminase 2 (TG2). Transglutaminase 2 is a multifunctional cross-linking enzyme implicated in various physiological and pathological conditions; however, its involvement in respiratory virus-induced airway inflammation is largely unknown. In this study, we demonstrated that RSV-induced oxidative stress promotes enhanced activation and release of TG2 from human lung epithelial cells as a result of its translocation from the cytoplasm and subsequent release into the extracellular space, which was mediated by Toll-like receptor (TLR)-4 and NF-κB pathways. Antioxidant treatment significantly inhibited RSV-induced TG2 extracellular release and activation via blocking viral replication. Also, treatment of RSV-infected lung epithelial cells with TG2 inhibitor significantly reduced RSV-induced matrix metalloprotease activities. These results suggested that RSV-induced oxidative stress activates innate immune receptors in the airways, such as TLRs, that can activate TG2 via the NF-κB pathway to promote cross-linking of extracellular matrix proteins, resulting in enhanced inflammation.

Diagnosing coeliac disease: A literature review

Coeliac disease (CD) is an autoimmune gastroenteropathy triggered by gliadin and gliadin-tissue transglutaminase (tTG) complexes. CD is one of the few autoimmune diseases with an accurate, non-invasive serological test. Anti-endomysial, anti-tTG and anti-deaminated gliadin peptides (DGP) antibodies are currently used for serological tests with tTG ELISAs being the superior test. Duodenal biopsy, although invasive, is the gold standard for CD diagnosis. HLA genotyping and flow cytometry can also be used as supplementary tests. The incidence of CD is rising globally although the reasons for this remain unclear. In addition, the true incidence of coeliac disease in African populations remains unknown although recent work suggests that South African populations express the alleles associated with this disease. This review examines the pathogenesis and diagnosis of coeliac disease and considers novel and innovative biomarkers in its diagnosis specifically in an African population.

Gliadin Sequestration as a Novel Therapy for Celiac Disease: A Prospective Application for Polyphenols

Celiac disease is an autoimmune disorder characterized by a heightened immune response to gluten proteins in the diet, leading to gastrointestinal symptoms and mucosal damage localized to the small intestine. Despite its prevalence, the only treatment currently available for celiac disease is complete avoidance of gluten proteins in the diet. Ongoing clinical trials have focused on targeting the immune response or gluten proteins through methods such as immunosuppression, enhanced protein degradation and protein sequestration. Recent studies suggest that polyphenols may elicit protective effects within the celiac disease milieu by disrupting the enzymatic hydrolysis of gluten proteins, sequestering gluten proteins from recognition by critical receptors in pathogenesis and exerting anti-inflammatory effects on the system as a whole. This review highlights mechanisms by which polyphenols can protect against celiac disease, takes a critical look at recent works and outlines future applications for this potential treatment method.

Physiopathology and Management of Gluten-Induced Celiac Disease

Proline- and glutamine-rich gluten proteins are one of the major constituents of cereal dietary proteins, which are largely resistant to complete cleavage by the human gastrointestinal (GI) digestive enzymes. Partial digestion of gluten generates approximately 35 amino acids (aa) immunomodulatory peptides which activate T-cell-mediated immune system, followed by immunological inflammation of mucosa leading to the onset of celiac disease (CD). CD is an autoimmune disease associated with HLA-DQ2/DQ8 polymorphism and dysbiosis of gut microbiota. CD is either diagnosed using duodenal mucosal biopsis or serological testing for transglutaminase 2 (TG2) specific antibodies (IgA and IgG). Current therapy for CD management is gluten-free diet, while other therapies like glutenase, probiotics, immunomodulation, jamming of HLA-DQ2, inhibition of TG2, and gluten tolerance aided by gluten tolerizing vaccines are being developed.

Identification of DNAJA1 as a novel interacting partner and a substrate of human transglutaminase 2

Transglutaminase 2 (TG2) is a ubiquitously expressed multifunctional member of the transglutaminase enzyme family. It has been implicated to have roles in many physiological and pathological processes such as differentiation, apoptosis, signal transduction, adhesion and migration, wound healing and inflammation. Previous studies revealed that TG2 has various intra- and extra-cellular interacting partners, which contribute to these processes. In the present study, we identified a molecular co-chaperone, DNAJA1, as a novel interacting partner of human TG2 using a GST pull-down assay and subsequent mass spectrometry analysis, and further confirmed this interaction via ELISA and surface plasmon resonance measurements. Interaction studies were also performed with domain variants of TG2 and results suggest that the catalytic core domain of TG2 is essential for the TG2-DNAJA1 interaction. Cross-linking activity was not essential for the interaction since DNAJA1 was also found to interact with the catalytically inactive form of TG2. Furthermore, we have showed that DNAJA1 interacts with the open form of TG2 and regulates its transamidation activity under both in vitro and in situ conditions. We also found that DNAJA1 is a glutamine donor substrate of TG2. Since DNAJA1 and TG2 are reported to regulate common pathological conditions such as neurodegenerative disorders and cancer, the findings in the present paper open up possibilities to explore molecular mechanisms behind TG2-regulated functions.

Serological prevalence of celiac disease in Brazilian population of multiple sclerosis, neuromyelitis optica and myelitis

PURPOSE

Comorbidity of celiac disease with demyelinating diseases of the central nervous system has been reported since the 1960s. The objective of this study was to determine the serological prevalence of celiac disease in the largest series of patients diagnosed with multiple sclerosis, neuromyelitis optica, or myelitis.

METHODS

A prevalence study was conducted with patients evaluated at Sarah Network of Rehabilitation Hospitals between March 2012 and September 2013. They were previously diagnosed with multiple sclerosis, neuromyelitis optica, or idiopathic myelitis. The serum levels of antibodies against tissue transglutaminase and endomysium were assessed.

RESULTS

Of the 379 patients evaluated, 249 (65.70%) were diagnosed with multiple sclerosis, 37 (9.56%) with neuromyelitis optica, and 96 (24.54%) with idiopathic myelitis. Two patients (0.53%), one with multiple sclerosis and other with myelitis, tested positive for both antibodies.

CONCLUSION

Our study do not confirm the relationship between celiac serological antibodies with multiple sclerosis, neuromyelitis optica and inflammatory myelitis of an unknown etiology.

Consensus Paper: Neuroimmune Mechanisms of Cerebellar Ataxias

In the last few years, a lot of publications suggested that disabling cerebellar ataxias may develop through immune-mediated mechanisms. In this consensus paper, we discuss the clinical features of the main described immune-mediated cerebellar ataxias and address their presumed pathogenesis. Immune-mediated cerebellar ataxias include cerebellar ataxia associated with anti-GAD antibodies, the cerebellar type of Hashimoto's encephalopathy, primary autoimmune cerebellar ataxia, gluten ataxia, Miller Fisher syndrome, ataxia associated with systemic lupus erythematosus, and paraneoplastic cerebellar degeneration. Humoral mechanisms, cell-mediated immunity, inflammation, and vascular injuries contribute to the cerebellar deficits in immune-mediated cerebellar ataxias.

Celiac disease 2015 update: new therapies

Celiac disease (CD) is a chronic, small intestinal, immune-mediated enteropathy triggered by exposure to dietary gluten in genetically susceptible individuals. Currently, lifelong adherence to a gluten-free diet (GFD) is the only available treatment. However, GFD alone is not sufficient to relieve symptoms, control small intestinal inflammation and prevent long-term complications in many patients. The GFD has its challenges including issues related to adherence, lifestyle restrictions and cost. As a result, there is growing interest in and a need for non-dietary therapies to manage this condition. In recent years, different targets in the immune-mediated cascade of CD have been identified in clinical and pre-clinical trials for potential therapies. This review will discuss the latest non-dietary therapies in CD, including endopeptidases, modulators of enterocyte tight junctions and agents involved in gluten tolerization and immunomodulation. We will also discuss the potential implications of approved therapeutics on CD clinical practice.

Gluten-related disorders: gluten ataxia

The term gluten-related disorders (GRD) refers to a spectrum of diverse clinical manifestations triggered by the ingestion of gluten in genetically susceptible individuals. They include both intestinal and extraintestinal manifestations. Gluten ataxia (GA) is one of the commonest neurological manifestations of GRD. It was originally defined as otherwise idiopathic sporadic ataxia in the presence of circulating antigliadin antibodies of IgA and/or IgG type. Newer more specific serological markers have been identified but are not as yet readily available. GA has a prevalence of 15% amongst all ataxias and 40% of all idiopathic sporadic ataxias. It usually presents with gait and lower limb ataxia. It is of insidious onset with a mean age at onset of 53 years. Up to 40% of patients have evidence of enteropathy on duodenal biopsy. Gastrointestinal symptoms are seldom prominent and are not a reliable indicator for the presence of enteropathy. Furthermore, the presence of enteropathy does not influence the response to a gluten-free diet. Most patients will stabilise or improve with strict adherence to gluten-free diet depending on the duration of the ataxia prior to the treatment. Up to 60% of patients with GA have evidence of cerebellar atrophy on MR imaging, but all patients have spectroscopic abnormalities primarily affecting the vermis. Recent evidence suggests that patients with newly diagnosed coeliac disease presenting to the gastroenterologists have abnormal MR spectroscopy at presentation associated with clinical evidence of subtle cerebellar dysfunction. The advantage of early diagnosis and treatment (mean age 42 years in patients presenting with gastrointestinal symptoms vs. 53 years in patients presenting with ataxia) may protect the first group from the development and/or progression of neurological dysfunction.

Genetic deletion of transglutaminase 2 does not rescue the phenotypic deficits observed in R6/2 and zQ175 mouse models of Huntington's disease

Huntington's disease (HD) is an autosomal dominant, progressive neurodegenerative disorder caused by expansion of CAG repeats in the huntingtin gene. Tissue transglutaminase 2 (TG2), a multi-functional enzyme, was found to be increased both in HD patients and in mouse models of the disease. Furthermore, beneficial effects have been reported from the genetic ablation of TG2 in R6/2 and R6/1 mouse lines. To further evaluate the validity of this target for the treatment of HD, we examined the effects of TG2 deletion in two genetic mouse models of HD: R6/2 CAG 240 and zQ175 knock in (KI). Contrary to previous reports, under rigorous experimental conditions we found that TG2 ablation had no effect on either motor or cognitive deficits, or on the weight loss. In addition, under optimal husbandry conditions, TG2 ablation did not extend R6/2 lifespan. Moreover, TG2 deletion did not change the huntingtin aggregate load in cortex or striatum and did not decrease the brain atrophy observed in either mouse line. Finally, no amelioration of the dysregulation of striatal and cortical gene markers was detected. We conclude that TG2 is not a valid therapeutic target for the treatment of HD.

The involvement of the HLA-DQB1 alleles in the risk and the severity of Iranian coeliac disease patients

Coeliac disease (CD) is a highly prevalent autoimmune disorder that is triggered by the ingestion of wheat gluten and related proteins in genetically susceptible individuals. The CD is associated with human leucocyte antigen (HLA) genes particularly with HLA-DQ alleles encoding HLA-DQ2 and DQ8 proteins. To define risk and severity alleles for CD, a total of 120 definite CD patients and 100 healthy controls were genotyped for HLA-DQB1 gene. HLA-DQB1 genotyping was performed in all patients and controls using PCR-SSP technique, and to evaluate the clinical relevance of testing for HLA-DQB1 and determining absolute risk of disease, prevalence-corrected positive predictive value and prevalence-corrected negative predictive value (PcPPV and PcNPV) were calculated. Our results for a first time show that DQB1*02:00 and DQB1*03:02 alleles and DQB1*02:01/03:02 genotype very significantly associated with increased risk of patients with CD, and DQB1*03:01,4 allele provides protection against CD in Iranian patients. Furthermore, the PcPPV for DQB*02:01 and 03:02 alleles in CD were 0.014 and 0.012, respectively, and the highest absolute risk presented by DQB*0201/0302 genotype (PcPPV = 0.079) and 98% of patients with CD carried DQB1*02:01/x or DQB1*03:02/x genotype. The results also clearly demonstrated that the DQB1*02:01 allele significantly associated with severity of CD, while DQB1*03:02 allele associated with mild form of CD. These results suggest that clinically suspected individuals for CD and first-degree relatives of patients with CD to be screened for HLA-DQB*0201 and DQB*0302 alleles for possible early diagnosis and treatments.

Autoantibodies against MHC class I polypeptide-related sequence A are associated with increased risk of concomitant autoimmune diseases in celiac patients

BACKGROUND

Overexpression of autologous proteins can lead to the formation of autoantibodies and autoimmune diseases. MHC class I polypeptide-related sequence A (MICA) is highly expressed in the enterocytes of patients with celiac disease, which arises in response to gluten. The aim of this study was to investigate anti-MICA antibody formation in patients with celiac disease and its association with other autoimmune processes.

METHODS

We tested serum samples from 383 patients with celiac disease, obtained before they took up a gluten-free diet, 428 patients with diverse autoimmune diseases, and 200 controls for anti-MICA antibodies. All samples were also tested for anti-endomysium and anti-transglutaminase antibodies.

RESULTS

Antibodies against MICA were detected in samples from 41.7% of patients with celiac disease but in only 3.5% of those from controls (P <0.0001) and 8.2% from patients with autoimmune disease (P <0.0001). These antibodies disappeared after the instauration of a gluten-free diet. Anti-MICA antibodies were significantly prevalent in younger patients (P <0.01). Fifty-eight patients with celiac disease (15.1%) presented a concomitant autoimmune disease. Anti-MICA-positive patients had a higher risk of autoimmune disease than MICA antibody-negative patients (P <0.0001; odds ratio = 6.11). The risk was even higher when we also controlled for age (odds ratio = 11.69). Finally, we found that the associated risk of developing additional autoimmune diseases was 16 and 10 times as high in pediatric patients and adults with anti-MICA, respectively, as in those without.

CONCLUSIONS

The development of anti-MICA antibodies could be related to a gluten-containing diet, and seems to be involved in the development of autoimmune diseases in patients with celiac disease, especially younger ones.

Uses of phage display in agriculture: a review of food-related protein-protein interactions discovered by biopanning over diverse baits

This review highlights discoveries made using phage display that impact the use of agricultural products. The contribution phage display made to our fundamental understanding of how various protective molecules serve to safeguard plants and seeds from herbivores and microbes is discussed. The utility of phage display for directed evolution of enzymes with enhanced capacities to degrade the complex polymers of the cell wall into molecules useful for biofuel production is surveyed. Food allergies are often directed against components of seeds; this review emphasizes how phage display has been employed to determine the seed component(s) contributing most to the allergenic reaction and how it has played a central role in novel approaches to mitigate patient response. Finally, an overview of the use of phage display in identifying the mature seed proteome protection and repair mechanisms is provided. The identification of specific classes of proteins preferentially bound by such protection and repair proteins leads to hypotheses concerning the importance of safeguarding the translational apparatus from damage during seed quiescence and environmental perturbations during germination. These examples, it is hoped, will spur the use of phage display in future plant science examining protein-ligand interactions.

SAR Development of Lysine-Based Irreversible Inhibitors of Transglutaminase 2 for Huntington's Disease

We report a series of irreversible transglutaminase 2 inhibitors starting from a known lysine dipeptide bearing an acrylamide warhead. We established new SARs resulting in compounds demonstrating improved potency and better physical and calculated properties. Transglutaminase selectivity profiling and in vitro ADME properties of selected compounds are also reported.

Irreversible 4-Aminopiperidine Transglutaminase 2 Inhibitors for Huntington's Disease

A new series of potent TG2 inhibitors are reported that employ a 4-aminopiperidine core bearing an acrylamide warhead. We establish the structure-activity relationship of this new series and report on the transglutaminase selectivity and in vitro ADME properties of selected compounds. We demonstrate that the compounds do not conjugate glutathione in an in vitro setting and have superior plasma stability over our previous series.

State of knowledge on amaranth grain: a comprehensive review

Amaranth grain is a highly nutritional pseudocereal with a superior amount of proteins when compared to true cereals. It is a reasonably well-balanced food with functional properties that have been shown to provide medicinal benefits. The health benefits attributed include decreasing plasma cholesterol levels, stimulating the immune system, exerting an antitumor activity, reducing blood glucose levels and improving conditions of hypertension and anemia. In addition, it has been reported to possess anti-allergic and antioxidant activities. The present article provides a comprehensive overview of amaranth grain that focuses on recent research reporting its use in the clinical practice and its possible benefits to human health.

Discovery and structure-activity relationship of potent and selective covalent inhibitors of transglutaminase 2 for Huntington's disease

Tissue transglutaminase 2 (TG2) is a multifunctional protein primarily known for its calcium-dependent enzymatic protein cross-linking activity via isopeptide bond formation between glutamine and lysine residues. TG2 overexpression and activity have been found to be associated with Huntington's disease (HD); specifically, TG2 is up-regulated in the brains of HD patients and in animal models of the disease. Interestingly, genetic deletion of TG2 in two different HD mouse models, R6/1 and R6/2, results in improved phenotypes including a reduction in neuronal death and prolonged survival. Starting with phenylacrylamide screening hit 7d, we describe the SAR of this series leading to potent and selective TG2 inhibitors. The suitability of the compounds as in vitro tools to elucidate the biology of TG2 was demonstrated through mode of inhibition studies, characterization of druglike properties, and inhibition profiles in a cell lysate assay.

Prevalence of celiac disease in multiple sclerosis

BACKGROUND

Celiac disease (CD) is a common systemic disease related to a permanent intolerance to gluten and is often associated with different autoimmune and neurological diseases. Its mean prevalence in the general population is 1-2% worldwide. Our aim was to study the prevalence of celiac disease in a prospective series of Multiple Sclerosis (MS) patients and their first-degree relatives.

METHODS

We analyzed the prevalence of serological, histological and genetic CD markers in a series of 72 MS patients and in their 126 first-degree relatives, compared to 123 healthy controls.

RESULTS

Tissue IgA-anti-transglutaminase-2 antibodies were positive in 7 MS patients (10%), compared to 3 healthy controls (2.4%) (p < 0.05). OR: 5.33 (CI-95%: 1.074-26.425). No differences were found in HLA-DQ2 markers between MS patients (29%) and controls (26%) (NS).We detected mild or moderate villous atrophy (Marsh III type) in duodenal biopsies, in 8 MS patients (11.1%). We also found a high proportion of CD among first-degree relatives: 23/126 (32%). Several associated diseases were detected, mainly dermatitis 41 (57%) and iron deficiency anemia in 28 (39%) MS patients. We also found in them, an increased frequency of circulating auto-antibodies such as anti-TPO in 19 (26%), ANA in 11 (15%) and AMA in 2 (3%).

CONCLUSIONS

We have found an increased prevalence of CD in 8 of the 72 MS patients (11.1%) and also in their first-degree relatives (23/126 [32%]). Therefore, increased efforts aimed at the early detection and dietary treatment of CD, among antibody-positive MS patients, are advisable.

Single-chain recombinant HLA-DQ2.5/peptide molecules block α2-gliadin-specific pathogenic CD4+ T-cell proliferation and attenuate production of inflammatory cytokines: a potential therapy for celiac disease

Celiac disease (CD) is a disorder of the small intestine caused by intolerance to wheat gluten and related proteins in barley and rye. CD4(+) T cells have a central role in CD, recognizing and binding complexes of HLA-DQ2.5 bearing gluten peptides that have survived digestion and that are deamidated by tissue transglutaminase (TG2), propagating a cascade of inflammatory processes that damage and eventually destroy the villous tissue structures of the small intestine. In this study, we present data showing that recombinant DQ2.5-derived molecules bearing covalently tethered α2-gliadin-61-71 peptide have a remarkable ability to block antigen-specific T-cell proliferation and inhibited proinflammatory cytokine secretion in human DQ2.5-restricted α2-gliadin-specific T-cell clones obtained from patients with CD. The results from our in vitro studies suggest that HLA-DQ2.5-derived molecules could significantly inhibit and perhaps reverse the intestinal pathology caused by T-cell-mediated inflammation and the associated production of proinflammatory cytokines.

Enzymatic strategies to detoxify gluten: implications for celiac disease

Celiac disease is a permanent intolerance to the gliadin fraction of wheat gluten and to similar barley and rye proteins that occurs in genetically susceptible subjects. After ingestion, degraded gluten proteins reach the small intestine and trigger an inappropriate T cell-mediated immune response, which can result in intestinal mucosal inflammation and extraintestinal manifestations. To date, no pharmacological treatment is available to gluten-intolerant patients, and a strict, life-long gluten-free diet is the only safe and efficient treatment available. Inevitably, this may produce considerable psychological, emotional, and economic stress. Therefore, the scientific community is very interested in establishing alternative or adjunctive treatments. Attractive and novel forms of therapy include strategies to eliminate detrimental gluten peptides from the celiac diet so that the immunogenic effect of the gluten epitopes can be neutralized, as well as strategies to block the gluten-induced inflammatory response. In the present paper, we review recent developments in the use of enzymes as additives or as processing aids in the food biotechnology industry to detoxify gluten.

Crystal structure of human transglutaminase 2 in complex with adenosine triphosphate

Transglutaminase 2 (TG2) is a calcium-dependent multifunctional protein associated with various human diseases. We determined the crystal structure of human TG2 in complex with adenosine triphosphate (ATP). The ATP molecule binds to the previously identified guanosine diphosphate (GDP) binding pocket but has different hydrogen bonds and ion interaction with protein. The four residues Arg476, Arg478, Val479 and Tyr583, all of which are involved in both ATP and GDP binding by hydrogen bonds, might play important roles in the stabilization of TG2 by ATP or GDP. However, Ser482 and Arg580, which are involved in GDP binding, do not form hydrogen bond with ATP. Additionally, we newly discovered an intramolecular disulfide bond between Cys230 and Cys370, which formation might regulate the enzymatic activity of TG2.

A profiling platform for the characterization of transglutaminase 2 (TG2) inhibitors

Huntington's disease (HD) is associated with increased expression levels and activity of tissue transglutaminase (TG2), an enzyme primarily known for its cross-linking of proteins. To validate TG2 as a therapeutic target for HD in transgenic models and for eventual clinical development, a selective and brain-permeable inhibitor is required. Here, a comprehensive profiling platform of biochemical and cellular assays is presented which has been established to evaluate the potency, cellular efficacy, subtype selectivity and the mechanism-of-action of known and novel TG2 inhibitors. Several classes of inhibitors have been characterized including: the commonly used pseudo-substrate inhibitors, cystamine and putrescine (which are generally nonspecific for TG2 and therefore not practical for drug development), the various peptidic inhibitors that target the active site cysteine residue (which display excellent selectivity but in general have poor cellular activity), and the allosteric reversible small-molecule hydrazides (which show poor selectivity and a lack of cellular activity and could not be improved despite considerable medicinal chemistry efforts). In addition, a set of inhibitors identified from a collection of pharmacologically active compounds was found to be unselective for TG2. Moreover, inhibition at the guanosine triphosphate binding site has been examined, but apart from guanine nucleotides, no such inhibitors have been identified. In addition, the promising pharmacological profile of a TG2 inhibitor is presented which is currently in lead optimization to be developed as a tool compound.

Biochemical and Immuno-pathological Aspects of Tissue Transglutaminase in Coeliac Disease

Tissue transglutaminase (tTg) has been identified as the major autoantigen in coeliac disease (CD). ELISA methods have been developed for measuring the autoantibody. There are divergent reports on the effects of calcium on the antibody binding to tTg. Furthermore, zinc is a potent inhibitor of tTg. To better understand the role of transglutaminase in CD, we have studied the stability of commercial tTG, the effect of CD serum on tTg-activity and the effects of calcium and zinc on the antibody binding. The inclusion of calcium during the coating of the ELISA plates significantly increases the binding of the antibody, while zinc at physiological concentrations inhibits the binding. Moreover, our results show that commercial guinea pig liver Tg treated with calcium contains at least four major antigenic molecules and is a labile enzyme, which is degraded rapidly by contaminating proteases. Human serum contains anti-proteases that protect the enzyme. Probably, the labile character of commercial tTG explains the divergent reports on the effects of calcium on antibody binding. Finally, antibodies in serum from a CD patient do not seem to inhibit tTg activity. Hypothetically, low, intestinal Zn2+ -levels facilitate Ca2+-activation of tTg, which deamidates gliadin. A complex between tTg and modified gliadin forms the antigen and triggers the immune reaction leading to manifest CD. Hypozincaemia secondary to villous atrophy aggravates the induced disease.

Clinical and biological significance of tissue transglutaminase in ovarian carcinoma

Tissue type transglutaminase (TG2) is a unique multifunctional protein that plays a role in many steps in the cancer metastatic cascade. Here, we examined the clinical (n = 93 epithelial ovarian cancers) and biological (in vitro adhesion, invasion, and survival and in vivo therapeutic targeting) significance of TG2 in ovarian cancer. The overexpression of TG2 was associated with significantly worse overall patient survival in both univariate and multivariate analyses. Transfection of TG2 into SKOV3ip1 cells promoted attachment and spreading on fibronectin-coated surfaces and increased the in vitro invasive potential of these cells. Conversely, TG2 silencing with small interfering RNA (siRNA) of HeyA8 cells significantly decreased the invasive potential of the cells and also increased docetaxel-induced cell death. In vivo therapy experiments using chemotherapy-sensitive (HeyA8) and chemotherapy-resistant (HeyA8-MDR and RMG2) models showed significant antitumor activity both with TG2 siRNA-1,2-dioleoyl-sn-glycero-3-phosphatidylcholine alone and in combination with docetaxel chemotherapy. This antitumor activity was related to decreased proliferation and angiogenesis and increased tumor cell apoptosis in vivo. Taken together, these findings indicate that TG2 overexpression is an adverse prognostic factor in ovarian carcinoma and TG2 targeting may be an attractive therapeutic approach.

Tissue transglutaminase in celiac disease: role of autoantibodies

In celiac disease (CD), gluten, the disease-inducing toxic component in wheat, induces the secretion of IgA-class autoantibodies which target tissue transglutaminase (tTG). These autoantibodies are produced in the small-intestinal mucosa, and, during gluten consumption, they can also be detected in patients' serum but disappear slowly from the circulation on a gluten-free diet. Interestingly, after adoption of a gluten-free diet the serum autoantibodies disappear from the circulation more rapidly than the small-intestinal mucosal autoantibody deposits. The finding of IgA deposits on extracellular tTG in the liver, kidney, lymph nodes and muscles of patients with CD indicates that tTG is accessible to the gut-derived autoantibodies. Although the specific autoantibody response directed against tTG is very characteristic in celiac patients, their role in the immunopathology of the celiac mucosal lesion is a matter of debate. Here we report a brief summary of anti-tTG antibody effects demonstrating that these antibodies are functional and not mere bystanders in the disease pathogenesis. In fact, they inhibit intestinal epithelial cell differentiation, induce intestinal epithelial cell proliferation, increase epithelial permeability and activate monocytes and disturb angiogenesis.

Extracellular transglutaminase 2 is catalytically inactive, but is transiently activated upon tissue injury

Transglutaminase 2 (TG2) is a multifunctional mammalian protein with transamidase and signaling properties. Using selective TG2 inhibitors and tagged nucleophilic amine substrates, we show that the majority of extracellular TG2 is inactive under normal physiological conditions in cell culture and in vivo. However, abundant TG2 activity was detected around the wound in a standard cultured fibroblast scratch assay. To demonstrate wounding-induced activation of TG2 in vivo, the toll-like receptor 3 ligand, polyinosinic-polycytidylic acid (poly(I:C)), was injected in mice to trigger small intestinal injury. Although no TG2 activity was detected in vehicle-treated mice, acute poly(I:C) injury resulted in rapid TG2 activation in the small intestinal mucosa. Our findings provide a new basis for understanding the role of TG2 in physiology and disease.

Determining IgA and IgG antigliadin, IgA antitransglutaminase, and antiendomysial antibodies in monkey esophagus and in umbilical cord for diagnosis of celiac disease in developing countries

OBJECTIVES

To assess the efficiency of determining IgA and IgG antigliadin antibodies (IgA- and IgG-AGA, respectively), antitransglutaminase (TgA), and anti-endomysial antibodies (AEA) in human umbilical cord (CO) and monkey esophagus for diagnosis of celiac disease; to determine the correlation between serological markers and celiac disease.

PATIENTS AND METHODS

A total of 400 patients were divided in 3 groups: group 1 with 37 patients with celiac disease, group 2 with 208 patients with no enteropathies, and group 3 with 155 patients with other enteropathies. IgA-AGA, IgG-AGA, and TgA were assessed using enzyme-linked immunosorbent assay, whereas AEA was evaluated by indirect immunofluorescence.

RESULTS

Sensitivity and specificity of IgA-AGA were 81.1% and 95.2%, of IgG-AGA 89.2% and 95.2%, of TgA 83.9% and 96.8%, of AEA-CO 87.9% and 100%, and of AEA of monkey esophagus 88.6% and 100%, respectively. Positive predictive values were 75.0%, 76.7%, 83.9%, and 100%. Negative predictive values were 96.6%, 98.0%, 96.8%, and 97.7% for IgA-AGA, IgG-AGA, TgA, and AEA, respectively. Multivariate analysis showed a strong association between AEA-CO and celiac disease and a good correlation with other markers (TgA, IgA-AGA, and IgG-AGA).

CONCLUSIONS

TgA has been recommended for screening patients with celiac disease. Considering the similar sensitivity and specificity of IgA-AGA and TgA and their correlations in the multivariate analysis, both are applicable for this purpose. However, because TgA tests are highly costly and celiac disease is associated with IgA deficiency, the determination of IgA-AGA and IgG-AGA, followed by AEA-CO, is suitable for screening in developing countries, provided a cutoff point for these examinations is established. The results of antiendomysial antibodies in umbilical cord overlapped those in monkey esophagus. Therefore, umbilical cord should be used as a substrate instead of specimens from endangered species.

Transglutaminase 2 inhibitors and their therapeutic role in disease states

Transglutaminase 2 (TG2) is a multi-domain, multi-functional enzyme that post-translationally modifies proteins by catalyzing the formation of intermolecular isopeptide bonds between glutamine and lysine side-chains. It plays a role in diverse biological functions, including extracellular matrix formation, integrin-mediated signaling, and signal transduction involving 7-transmembrane receptors. While some of the roles of TG2 under normal physiological conditions remain obscure, the protein is believed to participate in the pathogenesis of several unrelated diseases, including celiac sprue, neurodegenerative diseases, and certain types of cancer. A variety of small molecule and peptidomimetic inhibitors of the TG2 active site have been identified. Here, we summarize the biochemistry, biology, pharmacology and medicinal chemistry of human TG2.

Overactivity of the intestinal endocannabinoid system in celiac disease and in methotrexate-treated rats

The endocannabinoid system is upregulated in both human inflammatory bowel diseases and experimental models of colitis. In this study, we investigated whether this upregulation is a marker also of celiac disease-induced atrophy. The levels of the cannabinoid CB(1) receptor, of the endocannabinoids, anandamide, and 2-arachidonoyl-glycerol (2-AG), and of the anti-inflammatory mediator palmitoylethanolamide (PEA) were analyzed in bioptic samples from the duodenal mucosa of celiac patients at first diagnosis assessed by the determination of antiendomysial antibodies and histological examination. Samples were analyzed during the active phase of atrophy and after remission and compared to control samples from non-celiac patients. The levels of anandamide and PEA were significantly elevated (approx. 2- and 1.8-fold, respectively) in active celiac patients and so were those of CB(1) receptors. Anandamide levels returned to normal after remission with a gluten-free diet. We also analyzed endocannabinoid and PEA levels in the jejunum of rats 2, 3, and 7 days after treatment with methotrexate, which causes inflammatory features (assessed by histopathological analyses and myeloperoxidase activity) similar to those of celiac patients. In both muscle/serosa and mucosa layers, the levels of anandamide, 2-AG, and PEA peaked 3 days after treatment and returned to basal levels at remission, 7 days after treatment. Thus, intestinal endocannabinoid levels peak with atrophy and regress with remission in both celiac patients and methotrexate-treated rats. The latter might be used as a model to study the role of the endocannabinoid system in celiac disease.

Celiac disease

Celiac disease (CD) is a common autoimmune disorder, induced by the intake of gluten proteins present in wheat, barley and rye. Contrary to common belief, this disorder is a protean systemic disease, rather than merely a pure digestive alteration. CD is closely associated with genes that code HLA-II antigens, mainly of DQ2 and DQ8 classes. Previously, it was considered to be a rare childhood disorder, but is actually considered a frequent condition, present at any age, which may have multiple complications. Tissue transglutaminase-2 (tTG), appears to be an important component of this disease, both, in its pathogenesis and diagnosis. Active CD is characterized by intestinal and/or extra-intestinal symptoms, villous atrophy and crypt hyperplasia, and strongly positive tTG auto-antibodies. The duodenal biopsy is considered to be the "gold standard" for diagnosis, but its practice has significant limitations in its interpretation, especially in adults. Occasionally, it results in a false-negative because of patchy mucosal changes and the presence of mucosal villous atrophy is often more severe in the proximal jejunum, usually not reached by endoscopic biopsies. CD is associated with increased rates of several diseases, such as iron deficiency anemia, osteoporosis, dermatitis herpetiformis, several neurologic and endocrine diseases, persistent chronic hypertransami-nasemia of unknown origin, various types of cancer and other autoimmune disorders. Treatment of CD dictates a strict, life-long gluten-free diet, which results in remission for most individuals, although its effect on some associated extraintestinal manifestations remains to be established.

Prevalence and demographic characteristics of celiac disease among blood donors in Ribeirão Preto, State of São Paulo, Brazil

Celiac disease (CD) is an underdiagnosed disease occurring in different clinical forms. This study aimed to determine the prevalence of CD among blood donors from Ribeirão Preto, Brazil, and to study some demographic characteristics of celiac patients. Blood samples from 3000 blood donors were tested for the presence of tissue transglutaminase antibody and positive samples were tested for endomysial antibody. Donors positive to both tests were referred for clinical evaluation and for a jejunal biopsy. Twenty-four samples were moderately/strongly positive for transglutaminase, with 9 of them being endomysial negative and 15 positive. Of the 13 biopsies obtained from 12 females and 1 male, 1 was classified as Marsh grade IV, 4 as grade III, 2 as grade II, 4 as grade I, and 2 as grade 0. Estimated prevalence was therefore 1:273 (0.33%; 95% CI, 0.127 to 0.539). The 1:273 estimated prevalence of CD detected indicates that the disease is not rare in Brazil. The frequency was higher among females and among individuals of European descent, with a significantly higher frequency for a family history of digestive tract cancer or epilepsy.

Gliadin, zonulin and gut permeability: Effects on celiac and non-celiac intestinal mucosa and intestinal cell lines

OBJECTIVE

Little is known about the interaction of gliadin with intestinal epithelial cells and the mechanism(s) through which gliadin crosses the intestinal epithelial barrier. We investigated whether gliadin has any immediate effect on zonulin release and signaling.

MATERIAL AND METHODS

Both ex vivo human small intestines and intestinal cell monolayers were exposed to gliadin, and zonulin release and changes in paracellular permeability were monitored in the presence and absence of zonulin antagonism. Zonulin binding, cytoskeletal rearrangement, and zonula occludens-1 (ZO-1) redistribution were evaluated by immunofluorescence microscopy. Tight junction occludin and ZO-1 gene expression was evaluated by real-time polymerase chain reaction (PCR).

RESULTS

When exposed to gliadin, zonulin receptor-positive IEC6 and Caco2 cells released zonulin in the cell medium with subsequent zonulin binding to the cell surface, rearrangement of the cell cytoskeleton, loss of occludin-ZO1 protein-protein interaction, and increased monolayer permeability. Pretreatment with the zonulin antagonist FZI/0 blocked these changes without affecting zonulin release. When exposed to luminal gliadin, intestinal biopsies from celiac patients in remission expressed a sustained luminal zonulin release and increase in intestinal permeability that was blocked by FZI/0 pretreatment. Conversely, biopsies from non-celiac patients demonstrated a limited, transient zonulin release which was paralleled by an increase in intestinal permeability that never reached the level of permeability seen in celiac disease (CD) tissues. Chronic gliadin exposure caused down-regulation of both ZO-1 and occludin gene expression.

CONCLUSIONS

Based on our results, we concluded that gliadin activates zonulin signaling irrespective of the genetic expression of autoimmunity, leading to increased intestinal permeability to macromolecules.

Complement factor B allotypes in the susceptibility and severity of coeliac disease in patients and relatives

The alternative pathway of complement plays an important role in the pathogenesis of coeliac disease (CD), where factor B (BF) is central to its activation. CD is a gluten-sensitive enteropathy that results from a complex interplay between genetic, immunologic, and environmental factors. In this study we evaluated the association of BF allotypes with the susceptibility and severity of CD, and with the presence of autoantibodies. Seventy-six non-related patients (56 female; 20 male; 2-77 years) and 150 first-degree relatives (87 female, 63 male; 2-75 years) were investigated. As controls, 97 healthy individuals were included (67 female;, 30 male; 1-71 years). The BF allotypes were determined by high-voltage agarose gel electrophoresis, followed by specific immunofixation. Disease severity was evaluated by anti-endomisial antibody (IgA-EmA) titres and histological findings of intestinal mucosa, which showed a high correlation (r = 0.8; P < 0.00001) in samples collected simultaneously. IgA-EmA was detected in all CD patients ingesting gluten, and in 13.3% of the relatives. The IgA-EmA, smooth muscle, mitochondrial, liver-kidney microsomal, nuclear, gastric parietal cells, and thyroid microsome antibodies were tested by indirect immunofluorescence. A significant decrease in BF S (P = 0.026) and an increasing tendency in BF SF allotype (P = 0.06) were observed in CD patients when compared to their relatives. On the other hand, BF S frequency was increased (P = 0.001 RR = 2.32) and BF SF (P = 0.002) decreased in the relatives when compared to the controls. No differences were observed in the distribution of BF phenotypes amongst the CD patients and the control group, and no association was found with CD severity or with the presence of autoantibodies. These results suggest BF SF as a CD susceptibility marker, and BF S as a protection marker of the disease amongst CD families in the Brazilian population.

Coeliac disease, autoimmune diseases and gluten exposure

OBJECTIVE

Gluten-free diet treatment has been proposed to prevent the development of autoimmune diseases in coeliac subjects. The aim here was to investigate the occurrence of autoimmune disorders in relation to gluten intake in coeliac patients in a well-defined area.

MATERIAL AND METHODS

The frequency of autoimmune disorders was evaluated in 703 adults and children with coeliac disease and in 299 controls with normal duodenal histology. Incidence figures were given per 10,000 person-years. In logistic regression analysis, where the prevalence of autoimmune disorders was a dependent variable, the effect of age at end of follow-up, age at diagnosis of coeliac disease, actual gluten exposure time, gender and diagnostic delay were assessed.

RESULTS

The prevalence of autoimmune diseases was significantly higher in coeliac subjects than in controls. In logistic regression analysis, age at end of follow-up, age at diagnosis of coeliac disease and female gender increased the risk of autoimmune disorders, whereas actual gluten exposure time reduced the risk; diagnostic delay had no effect. A similar, though not statistically significant, trend was seen in childhood coeliac disease to that in the whole study group.

CONCLUSIONS

Despite that fact that patients with coeliac disease are at increased risk of various autoimmune conditions, the duration of gluten exposure seems not to be of crucial importance in the development of autoimmune diseases.

[Genetics and immunopathogenics aspects of the celiac disease: a recent vision]

BACKGROUND

Celiac disease, or gluten-sensitive enteropathy, is a strongly inherited condition. Although the genetic association of CD with the DQ2 and DQ8 HLA haplotypes has been known for long, others HLA and non-HLA genes are also important in the development of the disease. Celiac disease results of the combined effect of different normally functioning genes' products. The tissue damage in celiac disease is immunologically mediated and several effector mechanisms are responsible for the disease expression. The interplay between genetic, immunological and environmental factors explains the large spectrum of clinical, histological and serological alterations observed in the different stages of the disease development, pointing out to the polygenic nature of celiac disease.

CONCLUSION

The recent advances in the understanding of the immunopathogenesis, genetics and diagnoses of celiac disease have allowed the revision of strict concepts and previous criteria and their adequation to the new evidences, aiming a better diagnostic and orientation to celiac patients and relatives.

Comparative analysis of conventional training and a computer-based interactive training program for celiac disease patients

Gluten-free diet (GFD) protects against the complications of celiac disease (CD). However, training in the dietetic field is rare in Germany. Thus, CD patients are likely to benefit from a computer-based interactive training program (CBITP) combined with interactive exercises. We compared a CBITP and a conventional training for CD patients regarding increased knowledge, transferability and sustainability. In that context we analyzed whether CD patients are more able to judge the risk of a food or a situation after practicing with the interactive training software. Sixty-four CD patients were included and randomized in two groups. While the first group used the CBITP, the control group received written instructions. Before and after taking part in the training program and 3 weeks later, the participants filled in a questionnaire for celiac knowledge. The results show that both intervention and control groups increased knowledge about CD. However, the intervention group showed significantly better outcome. A CBITP significantly increases knowledge and sustainability as compared to a conventional training for CD patients. CBITPs can enhance patients' training and treatment.

A role for bacteria in celiac disease?

The finding of rod-shaped bacteria attached to the small intestinal epithelium of some untreated and treated celiac-disease patients, but not to the epithelium of healthy controls, ignites the notion that bacteria may be involved in the pathogenesis of celiac disease. This editorial discusses this possibility in relation to the current understanding of the molecular basis of this disorder.

Proteomics identification of acyl-acceptor and acyl-donor substrates for transglutaminase in a human intestinal epithelial cell line. Implications for celiac disease

Transglutaminase (TG)-catalyzed cross-linking of both intracellular and extracellular proteins is an important biochemical event. However, increased concentrations of cross-linked proteins have been observed in many disorders. Moreover, TG-catalyzed modification of proteins might generate new self-antigens responsible for the autoimmune response, as in celiac disease. The identification of available substrates may offer an understanding of how the TG-catalyzed post-translational modification has an impact on physiology and disease. We used a proteomic approach to identify TG-modified protein targets in human intestinal epithelial cells to determine the extent to which transglutaminase specifically contributes to celiac disease. Two probes were used for endogenous TG activity: 5-(biotinamido)pentylamine, which represents the acyl-acceptor, and a biotinylated glutamine-containing peptide, which represents the acyl-donor. This approach identified >25 proteins, which range from 30,000 to 300,000 Daltons and can serve as acyl-acceptor and/or acyl-donor for transglutaminase. Some of them were known transglutaminase substrates, whereas others had not been previously identified. These targets include proteins involved in cytoskeletal network organization, folding of proteins, transport processes, and miscellaneous metabolic functions.

Expression and enzymatic activity of small intestinal tissue transglutaminase in celiac disease

OBJECTIVES

The molecular and functional properties of small intestinal tissue transglutaminase are largely unknown despite growing interest because of its role in celiac disease (CD). In this study, we aimed to evaluate tissue transglutaminase expression and enzymatic activity in bioptic fragments obtained from the duodenum of untreated individuals with CD and from control subjects.

METHODS

Analysis of tissue transglutaminase mRNA expression was performed by reverse transcription-polymerase chain reaction (RT-PCR). The presence of the enzyme in bioptic fragments as well as in homogenates from CD patients and controls was revealed by immunohistochemistry and Western blot, respectively, using the antitissue transglutaminase CUB 7402 clone. To evaluate in situ transglutaminase activity, sections of bioptic fragments were incubated in the presence of 5 mmol/L CaCl(2) with 5-(biotinamido)pentylamine or, alternatively, with a biotinylated glutamine-containing hexapeptide (TVQQEL) and the biotinylated 31-43 A-gliadin-derived peptide.

RESULTS

Tissue transglutaminase mRNA levels were 1.0-fold higher (p < 0.05) in CD patients than in controls. Immunohistochemistry and in situ demonstration of enzymatic activity in celiac mucosa clearly showed an increased expression of active tissue transglutaminase in the extracellular matrix of the subepithelial region and in the enterocytes. Staining of the biotinylated 31-43 A-gliadin peptide in the same area of tissue transglutaminase suggested the presence of lysine-donor substrates in intestinal mucosa.

CONCLUSIONS

Tissue transglutaminase is more expressed and active in defined areas of the small intestinal mucosa from patients with CD. The presence in the celiac mucosa of proteins able to act as amine-donor substrates suggests that tissue transglutaminase-mediated post-translational modification of proteins cross-linked with gliadin peptides may represent a pathogenic mechanism of CD.

Immunohistochemical study of the apoptotic mechanisms in the intestinal mucosa during children's coeliac disease

Mechanisms leading to morphological changes of the small intestine during coeliac disease (CD) are not yet completely recognized; however, two main processes have been suggested recently: remodeling of mucosa by matrix metalloproteinases, and mucosal atrophy by apoptosis. The aim of this study was analysis of the expression of proteins regulating apoptosis in the small intestine of children with active CD (ACD) and potential CD (PCD). Jejunal biopsies of 43 children with PCD and untreated ACD and 21 control samples were analyzed by means of standard indirect immunohistochemical technique for Fas, Fas ligand (Fas-L), tissue transglutaminase (tTG), Bcl-2, and glutathione S-transferase (GST) expression. We found significantly lower numbers of Fas-expressing enterocytes in the ACD patients than in PCD patients and controls. Similarly, the number of Fas-positive mucosal lymphocytes was decreased in ACD when compared with PCD. The number of Fas-L- and tTG-expressing enterocytes and mucosal lymphocytes was higher in both PCD and ACD. On the other hand, the number of Bcl-2-positive mucosal lymphocytes in PCD as well as ACD was significantly lower. The expression of tTG in extracellular matrix was significantly higher in PCD and ACD when compared with controls. Our results showed that Fas and/or Fas-L, Bcl-2, and tTG may be involved in apoptotic pathways leading to mucosal atrophy in children with CD. tTG changes are in agreement with the presumed role of this protein in the pathogenesis of CD.

Characterization of a subgroup of patients with dermatitis herpetiformis with nonclassical histologic features

Dermatitis herpetiformis (DH) is an autoimmune disease mediated by IgA antibodies. The diagnosis of DH is based on clinical presentation, biopsy for hematoxylin and eosin, and direct immunofluorescence. The chief hematoxylin and eosin finding is a subepithelial blister with neutrophils in dermal papillae. The direct immunofluorescence findings are deposition of IgA and sometimes C3 at the basement membrane with accentuation in dermal papillae. Immunofluorescence is thought to be a sensitive and specific assay in DH, and there are no other known diseases with this pattern of immunofluorescence. The aim of this project was to determine the prevalence of nonclassical histologic findings in DH. We studied 24 cases of DH received at our institution. All cases had clinical findings of DH as well as positive direct immunofluorescence with IgA. We found that 9 of 24 cases (37.5%) had nonspecific H&E findings of a lymphocytic infiltrate only with fibrosis in the dermal papillae and ectatic capillaries. The remaining 15 cases had classic findings of multilocular neutrophilic microabscesses in the dermal papillae. These findings were reproduced on step sectioning. These findings suggest that routine histology may be quite nonspecific in DH and direct immunofluorescence or other more specific immunologic assay is an essential adjunct to diagnosis.

Coeliac disease--all questions answered?

Gliadin specific T cells in the small intestines of coeliac disease patients use the disease associated human leukocyte antigen-DQ2 molecules in their antigen recognition. In an exciting interplay with tissue transglutaminase, the immune system recognises modified gliadin peptides and mounts a phlogistic response. Moreover, the role for autoimmune phenomena and the mechanism of breaking of immunological tolerance remain elusive.

Tissue transglutaminase and coeliac disease pathogenesis: potential molecular mechanisms for other human diseases

Coeliac disease (CD) is one of the most common food intolerances described in the western population. The main food agent that provokes the strong and diffuse clinical symptoms has been known for several years to be gliadin, a protein present in a very large number of human foods derived from vegetables. Only recently, some biochemical and immunological aspects of this very common disease have been clarified, and tissue transglutaminase, a multifunctional and ubiquitous enzyme, has been identified as one of the major factors. This enzyme, through its catalytic activities, produces the main biochemical and immunological effects observed in patients affected by this disease. The aim of this review is to summarize the most recent findings concerning the relationships between the biochemical properties of tissue transglutaminase and the basic molecular mechanisms responsible for CD. In addition, we present some frequent clinical associations of CD with other human diseases, with particular reference to neuropsychiatric disorders. Possible molecular links between CD, neuropsychiatric disorders and biochemical activities of transglutaminase enzymes are discussed.

The tissue transglutaminase gene is not a primary factor predisposing to celiac disease

OBJECTIVES

The aim of this study was to determine whether the tissue transglutaminase (tTG) gene is a causal factor in the pathogenesis of celiac disease (CD).

METHODS

A total of 147 Dutch families with at least one patient with biopsy-proven CD were available for this study. In all patients, CD was diagnosed according to the revised European Society for Pediatric Gastroenterology and Nutrition criteria. A microsatellite marker in a noncoding region of the tTG gene was investigated for both linkage and association. Linkage was tested by determining the amount of allele sharing between affected brothers and sisters (affected sibling [sib] pair analysis). Association was determined by comparing transmission of certain tTG alleles from parents to CD patients to the nontransmitted alleles by the transmission/disequilibrium test.

RESULTS

Linkage analysis did not show cosegregation of the tTG gene with celiac disease in our families, and there was no association between certain tTG alleles and celiac disease. Furthermore, the tTG gene could be excluded as a CD susceptibility gene.

CONCLUSION

Our results indicate that the tTG gene can be excluded as a major primary genetic factor in CD pathogenesis.

Increased levels of IgA antibodies against desmin in children with coeliac disease

BACKGROUND

In addition to IgA anti-endomysial antibodies, IgA anti-smooth muscle antibodies have been observed in a number of patients with coeliac disease (CoD), but only limited data exist on the frequency and antigen specificity of IgA against cytoskeletal proteins in CoD.

METHODS

We evaluated the sera of 42 untreated CoD patients, follow-up sera of 26 CoD patients after treatment, and 116 control sera for IgA reactivity to cytoskeletal proteins from the human umbilical cord (HUC) by immunoblotting, and compared the results with anti-tissue transglutaminase IgA (anti-tTG IgA) ELISA and immunofluorescence results.

RESULTS

Serum IgA from CoD patients most frequently recognized a 57-kD antigen in HUC cytoskeletal extract, identified as desmin using mass spectrometry and internal peptide sequencing. Increased IgA reactivity to the human desmin band was detected in 22 children with untreated CoD (52.4%), in 4 treated CoD patients (15.4%), and in 12 control subjects (10.3%) (p < 0.01); similar results were obtained with anti-chicken desmin IgA ELISA. Anti-tTG IgA levels (increased in 71.4% of untreated CoD patients) correlated significantly with anti-desmin IgA levels in untreated CoD, and both autoantibody reactivities decreased in response to a gluten-free diet. Pre-adsorption experiments and affinity purification of anti-desmin IgA antibodies further confirmed that desmin is an IgA autoantigen in CoD and is recognized by antibodies which are not cross-reactive with tTG.

CONCLUSIONS

Anti-desmin IgA antibodies are frequently occurring if not the predominant cytoskeletal antibodies in children with untreated CoD and could be related to the disease process in the small intestine.