Contribution of the Enteric Nervous System to Autoimmune Diseases and Irritable Bowel Syndrome

Anti-neuronal autoantibodies can lead to subacute gastrointestinal dysmotility, presenting with various symptoms typical of intestinal pseudoobstruction, achalasia, gastroparesis, or slow intestinal transit, among others. Such autoantibodies may be produced in response to a remote tumor and accelerate the diagnosis of malignancy, but in other cases they appear without an identifiable underlying cause. One example is the type I anti-neuronal nuclear antibody (ANNA-1 otherwise known as anti-Hu), which is usually linked to small cell-lung carcinoma. Anti-Hu can directly activate enteric neurons and visceral sensory nerve fibers and has a cytotoxic effect. Various other anti-neuronal antibodies have been described, targeting different ion channels or receptors on nerve cells of the central or the enteric nervous system. Autoimmune processes targeting enteric neurons may also play a role in more common disorders such as esophageal achalasia, celiac disease, or multiple sclerosis. Furthermore, anti-enteric neuronal antibodies have been found more abundant in the common functional gastrointestinal disorder, irritable bowel syndrome (IBS), than in controls. The pathogenesis of IBS is very complex, involving the release of various mediators from immune cells in the gut wall. Products of mast cells, such as histamine and tryptase, excite visceral afferents and enteric neurons, which may contribute to symptoms like abdominal pain and disturbed motility. Elevated serine- and cysteine-protease activity in stool of IBS-D and IBS-C patients, respectively, can be a factor leading to leaky gut and visceral hypersensitivity. More knowledge on these mediators in IBS may facilitate the development of novel diagnostic methods or therapies.

Tourette syndrome or PANDAS-a case report

Tourette syndrome (TS), a relatively common disorder, has been gaining more attention during the past two decades because of an increased number of reports. Nevertheless, it is still not completely understood. Furthermore, a clinical entity called "pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections" (PANDAS) has been introduced, which describes a tic disorder, accompanied by psychiatric disorders such as obsessive compulsive disorder (OCD), after a streptococcal infection in childhood. We present a case report of a 19-year-old adolescent Ukrainian female, with a history of anxiety disorder and OCD, who, despite TS remission during childhood, presented with new-onset motor and phonic tics after 1 month of severe tonsillitis. Blood and cerebrospinal cultures showed Streptococcus pyogenes, with magnetic resonance imaging revealing hypo-intense changes in the caudate nucleus on both sides. Treatment with clonazepam and fluoxetine, along with behavioral therapy, have improved the severity of her condition. This report presents a case of TS reemergence against the background of immunological reaction or PANDAS with a late adolescent onset.

Presence of anti-neuronal antibodies in children with neurological disorders beyond encephalitis

BACKGROUND

Anti-neuronal autoantibodies have been reported as the cause of several neurologic disorders other than encephalitis. Unfortunately, data are mostly based on serum analysis. Predictions about pathogenicity are thus limited. To determine the presence of so far unidentified autoantibody-derived neuroreactivity we analyzed cerebrospinal fluid (CSF) of children with neurological disorders other than encephalitis.

PATIENTS AND METHODS

We did a retrospective analysis of CSF from 254 children with various neurologic diseases other than encephalitis and searched for reactivity against neuronal surface antigens by immunofluorescence on unfixed murine brain sections (tissue-based assay, TBA) and by commercial cell-based assays (CBA). A semi-quantitative fluorescence score classified our results and we described the clinical course of all positive patients with strong neuroreactivity.

RESULTS

Strong anti-neuronal IgG immunoreactivity of unknown antigen specificity was detected in CSF samples of 10 pediatric patients (4%, n = 10/254) with unsolved neurological disorders. CSF inflammatory markers were elevated. Most patients did not or only partly recover. Five screening-positive patients presented with a combination of headache and visual impairment due to optic nerve atrophy. Our data suggest to consider inflammatory, autoantibody-related etiologies, especially in cases without definite diagnoses.

CONCLUSIONS

We present an overview of CSF neuroreactivity in children with neurological disorders other than encephalitis, indicating the presence of unidentified anti-neuronal autoantibodies. As TBA enables screening for unknown autoantibodies, we suggest this method as a second step if commercial CBAs do not yield a result. Further studies are necessary to characterize such antibodies, evaluate pathogenicity, and answer the question whether positive CSF neuroreactivity should prompt an immunotherapeutic approach.

Conventional autoantibodies against brain antigens are not routinely detectable in serum and CSF of narcolepsy type 1 and 2 patients

Narcolepsy with cataplexy (NT1) is a chronic hypothalamic disorder with a presumed immune-mediated etiology leading to a loss of hypocretin neurons. Previous studies reported conflicting results in terms of presence of auto-antibodies involved in narcolepsy pathophysiology. A total of 86 patients with primary/idiopathic narcolepsy (74 NT1, 12 NT2) and 23 control patients with excessive daytime sleepiness due to other causes were tested for the presence of a wide range of anti-neuronal antibodies in both serum and cerebrospinal fluid (CSF). Anti-neuronal antibodies were rarely found in patients with narcolepsy (n = 2) and in controls (n = 1). Our results are in line with previous reports. We can therefore support the current evidence, that conventional anti-neuronal antibodies are not routinely detected during the workup of NT1 and other CDH patients.

Predictors of damage accrual in systemic lupus erythematosus: a longitudinal observational study with focus on neuropsychological factors and anti-neuronal antibodies

OBJECTIVE

Central nervous system disease occurs in over 20% of patients with systemic lupus erythematosus (SLE) resulting in major morbidity and damage. Cognitive dysfunction is common in SLE, but the cause remains uncertain and treatment options are limited. This study explores the influence of clinical, neuropsychological factors and anti-neuronal antibodies on lupus damage accrual.

METHOD

A prospective cohort with 99 SLE patients recruited between 2008 and 2013 and followed up in 2016 was established. Baseline evaluations were depression (MINI-Plus), cognitive function evaluating attention, visuospatial memory and executive functions, and anti-neuronal antibodies. Activity index (SLEDAI-2K) and SLICC/ACR Damage Index (SDI) were assessed at baseline and last follow-up.

RESULTS

At baseline, median (interquartile range) age was 36.0 years (27.0-45.0), disease duration 3.7 years (0.4-12.4), SLEDAI-2K 6.0 (3.0-12.0), and SDI score 1.0 (0-1.0). Major depression was present in 23%, cognitive deficit in 18%, and received immunomodulators in 36%. Anti-dsDNA/N-methyl-D-aspartate receptor antibodies were present in 19%, anti-ribosomal P in 12%, and anti-neuronal surface P antigen (NSPA) in 5%. After a median follow-up of 55 months (interquartile range 39-78), 11% had damage accrual. In a multivariate analysis, baseline SDI, SLEDAI-2K, and immunomodulators use were associated with final damage, whereas SLEDAI-2K and immunomodulator use were also associated with accrual damage. Models including anti-NSPA showed impact on final and accrual damage. Cognitive deficit, depression, and other autoantibodies were not predictors.

CONCLUSIONS

Disease activity and immunomodulator use associate with lupus damage. Of the anti-neuronal antibodies examined, anti-NSPA emerged as a potential poor prognostic factor, probably related to severe SLE onset requiring elevated corticosteroid doses. Key Points • Anti-NSPA may be a worse prognostic factor in SLE. • Other neuropsychological factors do not influence damage.

The significance of anti-neuronal antibodies for acute psychiatric disorders: a retrospective case-controlled study

Background

The clinical significance of anti-neuronal antibodies in patients with psychiatric disorders, but without encephalitis, remains unknown. In patients admitted to acute psychiatric inpatient care we aimed to identify clinical features distinguishing anti-neuronal antibody positive patients from matched controls.

Results

Patients who were serum-positive to N-methyl d-aspartate receptor (NMDAR) (n = 21), contactin-associated protein 2 (CASPR2) (n = 14) and/or glutamic acid decarboxylase 65 (GAD65) (n = 9) antibodies (cases) were age and sex matched (1:2) with serum-negative patients from the same cohort (controls). The prevalence and severity of psychiatric symptoms frequently encountered in NMDAR, CASPR2 and GAD65 antibody associated disorders were compared in cases and controls. NMDAR, CASPR2 and GAD65 antibody positive patients did not differ in their clinical presentation from matched serum negative controls.

Conclusion

In this cohort, patients with and without NMDAR, CASPR2 and GAD65 antibodies admitted to acute psychiatric inpatient care had similar psychiatric phenotypes. This does not exclude their clinical relevance in subgroups of patients, and studies further investigating the clinical significance of anti-neuronal antibodies in patients with psychiatric symptomatology are needed.

Electronic supplementary material

The online version of this article (10.1186/s12868-018-0471-7) contains supplementary material, which is available to authorized users.

Anti-neuronal anti-bodies in patients with early psychosis

It may be challenging to distinguish autoimmune encephalitis associated with anti-neuronal autoantibodies from primary psychiatric disorders. Here, serum was drawn from patients with a first-episode psychosis (n=70) or a clinical high-risk for psychosis (n=6) and controls (n=34). We investigated the serum prevalence of 24 anti-neuronal autoantibodies: IgG antibodies for anti-N-methyl-d-aspartate-type glutamate receptor (anti-NMDAR), glutamate and γ-aminobutyric acid alpha and beta receptors (GABA-a, GABA-b), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA), glycine receptor (GlyR), metabotropic glutamate receptor 1 and 5 (mGluR1, mGluR5), anti-Tr/Delta/notch-like epidermal growth factor-related receptor (DNER), contactin-associated protein-like 2 (CASPR2), myelin oligodendrocyte glycoprotein (MOG), glutamic acid decarboxylase-65 (GAD65), collapsin response mediator protein 5/crossveinless-2 (CV2), aquaporin-4 (AQP4), anti-dipeptidyl-peptidase-like protein-6 (DPPX), type 1 anti-neuronal nuclear antibody (ANNA-1, Hu), Ri, Yo, IgLON5, Ma2, zinc finger protein 4 (ZIC4), Rho GTPase-activating protein 26, amphiphysin, and recoverin, as well as IgA and IgM for dopamine-2-receptor (DRD2). Anti-NMDA IgG antibodies were positive with serum titer 1:320 in one patient with a clinical high risk for psychosis. He did not receive a diagnosis of encephalitis after comprehensive neurological evaluation. All other antineuronal autoantibodies were negative and there were no additional findings with immunohistochemistry of brain issues.

What is the significance of onconeural antibodies for psychiatric symptomatology? A systematic review

BACKGROUND

Patients with intracellular onconeural antibodies may present with neuro-psychiatric syndromes. We aimed to evaluate the evidence for an association between well-characterized onconeural antibodies and psychiatric symptoms in patients with and without paraneoplastic central nervous system syndromes.

METHODS

Eligible studies were selected from 1980 until February 2017 according to standardized review criteria and evaluated using Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2). We included studies describing the psychiatric symptomatology of onconeural antibody positive patients and the prevalence of onconeural antibodies in patients with psychiatric disorders.

RESULTS

Twenty-seven studies met the inclusion criteria. Six studies reported on the prevalence of well-characterized onconeural antibodies in patients with different psychiatric disorders, ranging from 0% to 4.9%. Antibody prevalence in controls was available from three studies, ranging from 0% to 2.8%. Data heterogeneity precluded a meta-analysis. Two cerebrospinal fluid studies found well-characterized onconeural antibodies in 3.5% and 0% of patients with psychotic and depressive syndromes, respectively.

CONCLUSIONS

The available evidence suggests that the prevalence of well-characterized onconeural antibodies in patients with psychiatric disorders is generally low. However, the question whether onconeural antibodies are important in select patients with a purely psychiatric phenotype needs to be addressed by appropriately designed studies in the future.

Anti-streptococcal, tubulin, and dopamine receptor 2 antibodies in children with PANDAS and Tourette syndrome: single-point and longitudinal assessments

Single-point-in-time ELISA optical densities for three putative antibodies identified in Sydenham's chorea, the streptococcal group A carbohydrate antigen, N-acetyl-beta-d-glucosamine, tubulin, and the dopamine 2 receptor, showed no differences in children with PANDAS (n=44) or Tourette syndrome (n=40) as compared to controls (n=24). Anti-tubulin and D2 receptor antibodies assessed in serial samples from 12 PANDAS subjects obtained prior to a documented exacerbation, during the exacerbation (with or without a temporally associated streptococcal infection), and following the exacerbation, showed no evidence of antibody levels correlating with a clinical exacerbation. These data do not support hypotheses suggesting an autoimmune hypothesis in either TS or PANDAS.