Intrathecal synthesis of autoantibodies against tissue transglutaminase

Celiac Disease and Neurological Manifestations: From Gluten to Neuroinflammation

Celiac disease (CD) is a complex multi-organ disease with a high prevalence of extra-intestinal involvement, including neurological and psychiatric manifestations, such as cerebellar ataxia, peripheral neuropathy, epilepsy, headache, cognitive impairment, and depression. However, the mechanisms behind the neurological involvement in CD remain controversial. Recent evidence shows these can be related to gluten-mediated pathogenesis, including antibody cross-reaction, deposition of immune-complex, direct neurotoxicity, and in severe cases, vitamins or nutrients deficiency. Here, we have summarized new evidence related to gut microbiota and the so-called "gut-liver-brain axis" involved in CD-related neurological manifestations. Additionally, there has yet to be an agreement on whether serological or neurophysiological findings can effectively early diagnose and properly monitor CD-associated neurological involvement; notably, most of them can revert to normal with a rigorous gluten-free diet. Moving from a molecular level to a symptom-based approach, clinical, serological, and neurophysiology data might help to disentangle the many-faceted interactions between the gut and brain in CD. Eventually, the identification of multimodal biomarkers might help diagnose, monitor, and improve the quality of life of patients with "neuroCD".

The Role of Exposomes in the Pathophysiology of Autoimmune Diseases I: Toxic Chemicals and Food

Autoimmune diseases affect 5–9% of the world’s population. It is now known that genetics play a relatively small part in the pathophysiology of autoimmune disorders in general, and that environmental factors have a greater role. In this review, we examine the role of the exposome, an individual’s lifetime exposure to external and internal factors, in the pathophysiology of autoimmune diseases. The most common of these environmental factors are toxic chemicals, food/diet, and infections. Toxic chemicals are in our food, drink, common products, the air, and even the land we walk on. Toxic chemicals can directly damage self-tissue and cause the release of autoantigens, or can bind to human tissue antigens and form neoantigens, which can provoke autoimmune response leading to autoimmunity. Other types of autoimmune responses can also be induced by toxic chemicals through various effects at the cellular and biochemical levels. The food we eat every day commonly has colorants, preservatives, or packaging-related chemical contamination. The food itself may be antigenic for susceptible individuals. The most common mechanism for food-related autoimmunity is molecular mimicry, in which the food’s molecular structure bears a similarity with the structure of one or more self-tissues. The solution is to detect the trigger, remove it from the environment or diet, then repair the damage to the individual’s body and health.

"Let Food Be Thy Medicine": Gluten and Potential Role in Neurodegeneration

Wheat is a most favored staple food worldwide and its major protein is gluten. It is involved in several gluten dependent diseases and lately was suggested to play a role in non-celiac autoimmune diseases. Its involvement in neurodegenerative conditions was recently suggested but no cause-and-effect relationship were established. The present narrative review expands on various aspects of the gluten-gut-brain axes events, mechanisms and pathways that connect wheat and gluten consumption to neurodegenerative disease. Gluten induced dysbiosis, increased intestinal permeabillity, enteric and systemic side effects, cross-reactive antibodies, and the sequence of homologies between brain antigens and gluten are highlighted. This combination may suggest molecular mimicry, alluding to some autoimmune aspects between gluten and neurodegenerative disease. The proverb of Hippocrates coined in 400 BC, "let food be thy medicine," is critically discussed in the frame of gluten and potential neurodegeneration evolvement.

Neuroimmunogastroenterology: At the Interface of Neuroimmunology and Gastroenterology

The central nervous system (CNS) is an important regulator of the gastrointestinal tract, and CNS dysfunction can result in significant and disabling gastrointestinal symptom manifestation. For patients with neuroimmunologic and neuroinflammatory conditions, the recognition of gastrointestinal symptoms is under-appreciated, yet the gastrointestinal manifestations have a dramatic impact on quality of life. The current treatment strategies, often employed independently by the neurologist and gastroenterologist, raise the question of whether such patients are being treated optimally when siloed in one specialty. Neuroimmunogastroenterology lies at the borderlands of medical specialties, and there are few resources to guide neurologists in this area. Here, we provide an overview highlighting the potential mechanisms of crosstalk between immune-mediated neurological disorders and gastrointestinal dysfunction.

IgG dynamics of dietary antigens point to cerebrospinal fluid barrier or flow dysfunction in first-episode schizophrenia

Schizophrenia is a complex brain disorder that may be accompanied by idiopathic inflammation. Classic central nervous system (CNS) inflammatory disorders such as viral encephalitis or multiple sclerosis can be characterized by incongruent serum and cerebrospinal fluid (CSF) IgG due in part to localized intrathecal synthesis of antibodies. The dietary antigens, wheat gluten and bovine milk casein, can induce a humoral immune response in susceptible individuals with schizophrenia, but the correlation between the food-derived serological and intrathecal IgG response is not known. Here, we measured IgG to wheat gluten and bovine milk casein in matched serum and CSF samples from 105 individuals with first-episode schizophrenia (n=75 antipsychotic-naïve), and 61 controls. We found striking correlations in the levels of IgG response to dietary proteins between serum and CSF of schizophrenia patients, but not controls (schizophrenia, R(2)=0.34-0.55, p⩽0.0001; controls R(2)=0.05-0.06, p>0.33). A gauge of blood-CSF barrier permeability and CSF flow rate, the CSF-to-serum albumin ratio, was significantly elevated in cases compared to controls (p⩽0.001-0.003). Indicators of intrathecal IgG production, the CSF IgG index and the specific Antibody Index, were not significantly altered in schizophrenia compared to controls. Thus, the selective diffusion of bovine milk casein and wheat gluten antibodies between serum and CSF in schizophrenia may be the function of a low-level anatomical barrier dysfunction or altered CSF flow rate, which may be transient in nature.

Can head trauma trigger celiac disease? Nation-wide case-control study

Background

TG6, a brain expressed transglutaminase, is implicated in the neurological manifestations of celiac disease (CD). We hypothesized that earlier brain injury due to head trauma may be more common in patients with CD, potentially through trauma-induced TG6 leading to interaction with TG2.

Methods

Through biopsy reports from all 28 pathology departments in Sweden we identified 29,096 individuals with CD (in this study defined as villous atrophy). We then examined the risk of earlier head trauma in CD compared to the risk in 144,522 controls matched for age, sex, county and calendar year. Odds ratios (ORs) were calculated using conditional logistic regression.

Results

981 (3.4%) individuals with CD and 4,449 (3.1%) controls had a record of earlier head trauma. Individuals with head trauma were hence at a 1.10-fold increased risk of future CD (95% CI = 1.02-1.17). ORs were independent of sex or age at CD. The highest risk of future CD was seen during the first year after trauma. There was no association between severity of trauma and risk of developing CD.

Conclusions

This study found a very small excess risk for future CD in individuals with an earlier head trauma.

Increased prevalence of transglutaminase 6 antibodies in sera from schizophrenia patients

Gluten can cause extraintestinal manifestations with or without gastrointestinal symptoms and elevated antitissue transglutaminase 2 (tTG2) autoantibodies. Organ-specific gluten reaction involves immune response toward other transglutaminase (TG) isoforms including tTG3 (expressed in the skin, leading to dermatitis herpetiformis) and tTG6 (expressed in the brain, causing gluten ataxia). This analysis focuses on tTG6 antibodies, which have never been studied before in schizophrenia (SZ) and its relationships to tTG2 and to antigliadin antibodies. We previously showed an increased prevalence of tTG2 antibodies in gluten sensitive SZ patients compared with healthy controls (HC) that was not paralleled by an increased prevalence of antiendomysial antibody. To elucidate this discrepancy, we examined those tTG2 positive SZ patients for the presence of tTG6 antibody. We also searched for tTG6 antibodies in our sample of antigliadin (AGA) positive and AGA and tTG2 negative SZ patients. Seventy-four tTG2 positive SZ patients were compared with 148 age and gender-matched HC. Of the 74 tTG2 positive SZ patients, 16 were positive for tTG6 IgA for a prevalence of 22%. Only 4 HC were positive for tTG6 IgA for a prevalence of 2.7%. Among the AGA positive SZ patients, the prevalence of tTG6 IgA was 21.3% while 13.1% of the AGA and tTG2 negative SZ patients were positive for tTG6 IgA. The HC had a prevalence of 6%. Our results indicate a higher prevalence of tTG6 antibodies in SZ that may represent a biomarker useful to identify SZ patients who would benefit from a gluten-free diet.

Downbeat nystagmus, ataxia and spastic tetraparesis due to coeliac disease

A 25-year-old female presented to a university neurology clinic with a 1-month history of progressive ataxia, downbeat nystagmus and spastic tetraparesis. Personal history revealed polyarthralgias and weight loss. Family history was negative. Following thorough history, laboratory, neurophysiological and MRI investigations, a diagnosis of cerebellar ataxia due to coeliac disease was done. The patient was treated with strict gluten-free diet and intravenous administration of immunoglobulins. Although there are many controversies about neurological manifestations of coeliac disease, this case pointed to strong association between these two disorders. The findings of elevated protein content in the cerebrospinal fluid with positive oligoclonal bands suggested an immune-mediated process, further supported by positive anti-endomysium antibodies and anti-transglutaminase antibodies in the cerebrospinal fluid.

Anti transglutaminase antibodies cause ataxia in mice

Background

Celiac disease (CD) is an autoimmune gastrointestinal disorder characterized by the presence of anti-transglutaminase 2 (TG2) and anti-gliadin antibodies. Amongst the neurological dysfunctions associated with CD, ataxia represents the most common one.

Methods

We analyzed by immunohistochemistry, the anti-neural reactivity of the serum from 20 CD patients. To determine the role of anti-TG2 antibodies in ataxia, two anti-TG2 single chain variable fragments (scFv), isolated from a phage-display IgA antibody library, were characterized by immunohistochemistry and ELISA, and injected in mice to study their effects on motor coordination. We found that 75% of the CD patient population without evidence of neurological involvement, has circulating anti-neural IgA and/or IgG antibodies. Two anti-TG2 scFvs, cloned from one CD patient, stained blood vessels but only one reacted with neurons. This anti-TG2 antibody showed cross reactivity with the transglutaminase isozymes TG3 and TG6. Intraventricular injection of the anti-TG2 or the anti-TG2/3/6 cross-reactive scFv provoked transient, equally intensive ataxia in mice.

Conclusion

The serum from CD patients contains anti-TG2, TG3 and TG6 antibodies that may potentially cause ataxia.

Quantification of antineural antibodies in autoimmune neurological disorders

More than 50 different neurological pathologies have a confirmed or suspected autoimmune etiology affecting an estimated number of 75 million people worldwide. Autoantibodies are a useful diagnostic marker for most autoimmune diseases even though their pathological role is not evident, and several tests for their detection are commercially available. However, for autoimmune diseases involving the nervous system, lack of clear information on the identity of antineural antibody targets and the presence of many rare diseases have hampered the development of specific diagnostic assays. This review focuses on the actual knowledge on confirmed and suspected autoimmune diseases that target the CNS and the diagnostic relevance of corresponding antineural autoantibodies.

Gluten ataxia: passive transfer in a mouse model

Gluten sensitivity is an autoimmune disease that usually causes intestinal atrophy resulting in a malabsorption syndrome known as celiac disease. However, gluten sensitivity may involve several organs and is often associated with extraintestinal manifestations. Typically, patients with celiac disease have circulating anti-tissue transglutaminase and anti-gliadin antibodies. When patients with gluten sensitivity are affected by other autoimmune diseases, other autoantibodies may arise like anti-epidermal transglutaminase in dermatitis herpetiformis, anti-thyroid peroxidase antibodies in thyroiditis, and anti-islet cells antibodies in type 1 diabetes. The most common neurological manifestation of gluten sensitivity is ataxia, the so-called gluten ataxia (GA). In patients with GA we have demonstrated that anti-gliadin and anti-tissue transglutaminase antibodies cross-react with neurons but that additional anti-neural antibodies are present. The aim of the present article is to review the knowledge on animal models of gluten sensitivity, as well as reviewing the role of anti-neural antibodies in GA.

Deamidated Gliadin Peptides as Targets for Celiac Disease‐Specific Antibodies

Celiac disease (CD) is an (auto)immunologically mediated intestinal intolerance against proteins from wheat (gluten) and related cereal proteins. Tissue transglutaminase (tTG) has been identified as the autoantigen in CD. Although ultimate diagnosis is based on histological analysis of small intestinal mucosa obtained via tissue biopsy, assessment of autoantibodies can provide substantial help in the evaluation of CD. Gliadin antibodies are directed against the native disease-provoking cereal proteins. Despite their initial usefulness, these antibodies have lost diagnostic importance due to their poor specificity and sensitivity as CD markers. Recently, it was found, however, that gliadin antibodies from sera of patients with active CD preferentially recognized deamidated gliadin peptides. The use of deamidated gliadin peptides in immunoassays has significantly improved the usefulness of gliadin antibodies in diagnosis of CD to that observed with autoantibody assay methods (endomysium antibodies, antibodies against tTG). The antibody epitopes (B-cell epitopes) reflect substrate specificity of tTG and resemble peptide sequences known to be strongly T-cell stimulatory (T-cell epitopes) in CD. The assay applying deamidated gliadin peptides measures a new species of antibodies, which is different from conventional gliadin antibodies as well as from autoantibodies and will likely provide new information on pathophysiological mechanisms of CD.

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

BACKGROUND

Celiac disease (CD) is induced by wheat gliadins and related cereal proteins. Anti-gliadin antibodies (AGAs) are present in the serum of CD patients, but these antibodies have lower diagnostic specificity and sensitivity than autoantibodies [anti-endomysium antibodies (AEmAs) and anti-tissue transglutaminase antibodies (AtTGAs)]. Recently, AGAs from CD patients were found to recognize deamidated gliadin peptides, probably formed by the action of tissue transglutaminase.

METHODS

We synthesized several gliadin peptides and their glutamine-glutamic acid-substituted counterparts on cellulose membranes and tested their recognition by IgA in sera of 52 AEmA-positive CD patients and 76 AEmA-negative controls in a luminescence assay. For comparison, we assayed IgA concentrations of AGAs, AtTGAs, and AEmAs. For measurement of AtTGAs, we used the human recombinant antigen.

RESULTS

We identified several nonapeptides that were detected with high specificity by IgA in CD patients. Diagnostic accuracy of the peptide antibody assay was highest when peptide PLQPEQPFP was used in combination with peptide PEQLPQFEE within one assay. AGAs were above the cutoff in 14 of the controls, but only 5 of the controls were positive for peptide antibodies. For comparison, 82% and 94% of samples were correctly classified by AGAs and the combination nonapeptide assay, respectively (P = 0.007), and the AtTGAs correctly classified 98%.

CONCLUSION

The peptide antibody assay has higher diagnostic accuracy than AGAs for distinguishing patients with CD from controls, and has diagnostic accuracy similar to that of AtTGAs.