Decreased numbers of regulatory T cells suggest impaired immune tolerance in children with tourette syndrome: a preliminary study

Identification of immune traits associated with neurodevelopmental disorders by two-sample Mendelian randomization analysis

BACKGROUND

One of the main causes of health-related issues in children is neurodevelopmental disorders (NDDs), which include attention-deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), and Tourette syndrome (TS). Nonetheless, there is relatively little prior research looking at the link between immunological inflammation and NDDs. Our work uses a two-sample Mendelian Randomization (MR) approach to provide a thorough evaluation of the causal effects of immune traits on ADHD, ASD, and TS.

METHODS

As exposures, 731 immunological traits' genetic associations were chosen, and the outcomes were genome-wide association data for ADHD, ASD, and TS. The inverse-variance weighted (IVW), weighted median (WM), and MR-Egger methods were used to conduct MR analysis. The results' robustness, heterogeneity, and horizontal pleiotropy were confirmed using extensive sensitivity analysis.

RESULTS

With single-nucleotide polymorphisms serving as instruments and false discovery rate (FDR) correction applied, the study found that significantly higher expression of CD62L on CD62L+ myeloid DC (IVW, OR: 0.926, 95% CI 0.896~0.958, P = 9.42 × 10-6, FDR = 0.007) and suggestively higher absolute cell count (AC) of CD28 + DN (CD4-CD8-) (IVW, OR: 0.852, 95% CI = 0.780 ∼ 0.932, P-value = 4.65 × 10-4, FDR = 0.170) was associated with a lower risk of ADHD. There was no pleiotropy, and the causal relationships were strong according to sensitivity, leave-one-out, and MR-Steiger directionality tests. For ASD and TS, no harmful or protective immune traits were observed.

CONCLUSIONS

The results of the study lend credence to the theory that deficiency in CD62L on CD62L+ myeloid DC and CD28 + DN (CD4-CD8) AC may contribute to the onset of ADHD.

The effects of Shaoma Zhijing granules and its main components on Tourette syndrome

BACKGROUND

Tourette syndrome (TS) represents a neurodevelopmental disorder characterized by an uncertain etiology and influencing factors. Frequently, it co-occurs with conditions such as attention deficit hyperactivity disorder, obsessive-compulsive disorder, and sleep disturbances, which have garnered substantial attention from the research community in recent years. Clinical trials have demonstrated that Shaoma Zhijing Granules (SMZJG, 5-ling granule, also known as TSupport or T92 under U.S. development), a traditional Chinese medicine compound, is an effective treatment for TS.

PURPOSE

To conduct scientometric analysis on developing trends, research countries and institutions, current status, hot spots of TS and discuss the underlying mechanisms of SMZJG and its main components on TS. The aim is to provide valuable reference for ongoing clinical and basic research on TS and SMZJG.

STUDY DESIGN & METHODS

Using Tourette syndrome, SMZJG and its main components along with their synonyms as keywords, we conducted a comprehensive search across major scientific databases including the Web of Science Core Collection, PubMed and China National Knowledge Infrastructure (CNKI) databases. A total of 5952 references and 99 patents were obtained. Among these, 5039 articles and reviews, as well as 54 patents were analyzed by Citespace and VOSviewer software.

RESULTS

The available evidence indicates that the SMZJG's components likely exert their mechanisms in treating TS by regulating the dopaminergic pathway system, neurotransmitter imbalances, reducing neuroinflammation, promoting the repair of nerve damage and improving sleep disorders.

CONCLUSION

This comprehensive analysis lays the foundation for an extensive exploration of the feasibility and clinical applications of SMZJG in TS treatment.

A review of common influencing factors and possible mechanisms associated with allergic diseases complicating tic disorders in children

Over the past few decades, the incidence of childhood allergic diseases has increased globally, and their impact on the affected child extends beyond the allergy itself. There is evidence of an association between childhood allergic diseases and the development of neurological disorders. Several studies have shown a correlation between allergic diseases and tic disorders (TD), and allergic diseases may be an important risk factor for TD. Possible factors influencing the development of these disorders include neurotransmitter imbalance, maternal anxiety or depression, gut microbial disorders, sleep disturbances, maternal allergic status, exposure to tobacco, and environmental factors. Moreover, gut microbial disturbances, altered immunological profiles, and DNA methylation in patients with allergic diseases may be potential mechanisms contributing to the development of TD. An in-depth investigation of the relationship between allergic diseases and TD in children will be important for preventing and treating TD.

Immunological characterization of an Italian PANDAS cohort

This cross-sectional study aimed to contribute to the definition of Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections (PANDAS) pathophysiology. An extensive immunological assessment has been conducted to investigate both immune defects, potentially leading to recurrent Group A β-hemolytic Streptococcus (GABHS) infections, and immune dysregulation responsible for a systemic inflammatory state. Twenty-six PANDAS patients with relapsing-remitting course of disease and 11 controls with recurrent pharyngotonsillitis were enrolled. Each subject underwent a detailed phenotypic and immunological assessment including cytokine profile. A possible correlation of immunological parameters with clinical-anamnestic data was analyzed. No inborn errors of immunity were detected in either group, using first level immunological assessments. However, a trend toward higher TNF-alpha and IL-17 levels, and lower C3 levels, was detected in the PANDAS patients compared to the control group. Maternal autoimmune diseases were described in 53.3% of PANDAS patients and neuropsychiatric symptoms other than OCD and tics were detected in 76.9% patients. ASO titer did not differ significantly between the two groups. A possible correlation between enduring inflammation (elevated serum TNF-α and IL-17) and the persistence of neuropsychiatric symptoms in PANDAS patients beyond infectious episodes needs to be addressed. Further studies with larger cohorts would be pivotal to better define the role of TNF-α and IL-17 in PANDAS pathophysiology.

Efficacy and safety of 5-hydroxytryptamine-3 (5-HT3) receptor antagonists in augmentation with selective serotonin reuptake inhibitors (SSRIs) in the treatment of moderate to severe obsessive-compulsive disorder: a systematic review and meta-analysis of randomized clinical trials

Obsessive-compulsive disorder (OCD) is the fourth most common mental disorder, and selective serotonin reuptake inhibitors (SSRIs) are the cornerstone of its pharmacological treatment. About 40-60% of the cases are treatment-refractory, and this makes searching for second-line treatment necessary. 5-Hydroxytryptamine-3 (5-HT3) antagonists are among the many medications that have been used in augmentation with SSRIs. In this systematic review and meta-analysis, we assessed the efficacy and safety of 5-HT3 receptor antagonists in augmentation with SSRIs in treating moderate to severe OCD. We searched PubMed, Web of Science, Scopus, Cochrane library, and Google Scholar for relevant trials published up to December 2022. The effect size was the mean difference in Yale-Brown obsessive compulsive scale (Y-BOCS) scores before and after receiving 5-HT3 receptor antagonist drugs in augmentation with SSRIs in moderate to severe OCD patients. We included 6 randomized-controlled trails (RCTs) with 334 patients assessing the effect of the augmentation of SSRIs with ondansetron, granisetron, and tropisetron on treating moderate to severe OCD. Our results were in favor of the experimental group in total (Z = 8.37, P < 0.00001), in the compulsion subgroup (Z = 5.22, P < 0.00001), and in the obsession subgroup (Z = 8.33, P < 0.00001). They are well-tolerated, and have mild side effects and do not result in withdrawal. Augmentation of 5-HT3 antagonists with SSRIs can be beneficial in treating moderate to severe OCD. Further multi-center trials under adequate conditions in longer periods are needed to help come up with a comprehensive action plan.

Obsessive-Compulsive Disorder, PANDAS, and Tourette Syndrome: Immuno-inflammatory Disorders

In the last years, much focus has been given to the possible role of inflammatory and immunologic alterations in the pathophysiology of obsessive-compulsive disorder (OCD) and some related conditions, such as pediatric autoimmune neuropsychiatric disorders associated with streptococcal infection (PANDAS) and Tourette syndrome (TS). Although the matter is intriguing, the available data are still controversial and/or limited. Therefore, the aim of this chapter was at reviewing and commenting on the literature on possible dysfunctions of inflammatory and immune system processes in OCD, PANDAS, and TS.This narrative review was carried out through searching PubMed and Google Scholar for English language papers from January 1985 to December 31, 2021.The data gathered up to now would suggest that the mechanisms involved might be heterogeneous according to the age of the patients and the disorder examined. Indeed, PANDAS seem more related to infections triggering autoimmunity not necessarily following group A beta-hemolytic streptococcal (GABHS) infection, as supposed in the past. Autoimmunity seems also important in TS, if coupled with an individual vulnerability that can be genetic and/or environmental. The data in adult OCD, albeit scattered and sometimes obtained in small samples of patients, would indicate that immune system and inflammatory processes are involved in the pathophysiology of the disorder. However, it is still unclear to conclude whether they are primary or secondary phenomena.In conclusion, taken together, the current findings pave that way towards novel and promising domains to explore the pathophysiology of OCD and related disorders, as well towards the development of innovative therapeutic strategy beyond current pharmacological paradigms.

Immunology and microbiome: Implications for motor systems

Immune-inflammatory mechanisms seem to play a relevant role in neurodegenerative disorders affecting motor systems, particularly Parkinson's disease, where activity changes in inflammatory cells and evidence of neuroinflammation in experimental models and patients is available. Amyotrophic lateral sclerosis is also characterized by neuroinflammatory changes that involve primarily glial cells, both microglia and astrocytes, as well as systemic immune dysregulation associated with more rapid progression. Similarly, the exploration of gut dysbiosis in these two prototypical neurodegenerative motor disorders is advancing rapidly. Altered composition of gut microbial constituents and related metabolic and putative functional pathways is supporting a pathophysiological link that is currently explored in preclinical, germ-free animal models. Less compelling, but still intriguing, evidence suggests that motor neurodevelopmental disorders, e.g., Tourette syndrome, are associated with abnormal trajectories of maturation that include also immune system development. Microglia has a key role also in these disorders, and new therapeutic avenues aiming at its modulation are exciting prospects. Preclinical and clinical research on the role of gut dysbiosis in Tourette syndrome and related behavioral disorders is still in its infancy, but early findings support the rationale to delve deeper into its contribution to neural and immune maturation abnormalities in its spectrum.

Profiles of Proinflammatory Cytokines and T Cells in Patients With Tourette Syndrome: A Meta-Analysis

Background

Tic disorder is a neurodevelopmental disorder characterized by motor and phonic tic symptoms. Tourette syndrome (TS) is a subtype of tic disorder that shows more persistent tic symptoms. The etiological mechanism of TS concerning immune dysfunction remains unclear due to limited evidence, especially for pediatric TS patients.

Method

In the present study, a meta-analysis was performed to confirm the identified changes in proinflammatory cytokines and T cells of pediatric TS patients. A total of five databases, including PubMed, Web of Science, PsycINFO, Google Scholar and the China National Knowledge Infrastructure (CNKI), were used for the literature search. The standardized mean difference (SMD) and mean difference (MD) with a 95% confidence interval (CI) were used to present the effect size of each type of proinflammatory cytokine and T cell. Sensitivity analysis, subgroup analysis and meta-regression analysis were used to explore the heterogeneity of the meta-analysis. This meta-analysis was registered in the International Platform of Registered Systematic Review and Meta-analysis Protocols (number: INPLASY2021110079).

Results

In the 25 studies included in this meta-analysis, thirteen studies focused on the levels of T cells, and twelve studies focused on the levels of proinflammatory cytokines. Based on the random-effects model, the pooled MDs are -1.45 (95% CI: -3.44, 0.54) for CD3 cells, -4.44 (95% CI: -6.80, -2.08) for CD4 cells, and 1.94 (95% CI: -0.08, 3.97) for CD8 cells. The pooled SMDs are1.36 for IL-6 (95% CI: 0.00, 2.72) and 2.39 for tumor necrosis factor alpha (TNF-α) (95% CI: 0.93, 3.84).

Conclusion

We provided evidence of immune dysfunction in pediatric TS patients, with elevated levels of particular proinflammatory cytokines and disproportionate changes in T-cell subpopulations. Small to large effect sizes were identified for increased IL-6 levels as well as a reduced number of T helper cells, while a large effect size was identified for increased TNF-α levels. These results indicate a close association between peripheral immune activation and TS. However, the most direct and meaningful interaction between peripheral immune status and microglial activation in the central nervous system in TS patients requires further exploration.

Mycoplasma pneumoniae IgG positivity is associated with tic severity in chronic tic disorders

Infectious pathogens may represent an environmental risk factor for chronic tic disorders (CTD). This cross-sectional study aimed to determine whether Mycoplasma pneumoniae (M. pneumoniae) IgG positivity is associated with the presence or severity of tics. We compared M. pneumoniae IgG positivity across three groups: children and adolescents (3-16 years) with CTD (CTD group; n = 302); siblings (3-10 years) of people with CTD who developed tics within a seven-year follow-up period (tic onset group; n = 51); siblings (4-10 years) who did not develop tics within the study period and were ≥10-years-old at their last assessment (unaffected group; n = 88). The relationship between M. pneumoniae IgG positivity and the presence and severity of tics was analysed using multilevel models controlling for site, family relatedness, sex, age, presence of comorbid obsessive-compulsive and/or attention-deficit/hyperactivity disorder and use of psychotropic medication. M. pneumoniae IgG positivity was not associated with the presence of CTD, or the first onset of tics as compared to siblings who remained unaffected. M. pneumoniae IgG positivity was associated with a higher tic severity score within the CTD group (β = 2.64, s.e. = 1.15, p = 0.02). It is possible that M. pneumoniae infection influences tic severity in CTD or, that having more severe tics, increases the risk of infection. However, it is more likely that the association observed in this study reflects a propensity toward enhanced immune responses in people with CTD and that, rather than a causal relationship, infection and greater tic severity are indirectly linked via shared underlying immune mechanisms.

Effects of Celecoxib Adjunct to Selective Serotonin Reuptake Inhibitors on Obsessive-Compulsive Disorder

Introduction:

Inflammatory processes in the brain play an important role in the etiopathogenesis of Obsessive-Compulsive Disorder (OCD). Cyclooxygenase inhibitors, such as celecoxib reduce the production of proinflammatory cytokines. This double-blind study aimed to investigate the effects of adding celecoxib to Selective Serotonin Reuptake Inhibitors (SSRIs)on treating OCD.

Methods:

Sixty patients who met the diagnosis criteria for OCD based on the Diagnostic and Statistical Manual of Mental Disorders -Fourth Edition- Text Revision (DSM-IV-TR) were recruited in the present study. Two psychiatrists independently confirmed the diagnosis by performing structured interviews. The study participants included 23 patients who received SSRIs and celecoxib (400 mg twice daily) and 22 patients in the control group that received SSRIs and placebo. Moreover, at baseline, in weeks 4, 8, and 12, the explored patients were assessed by a psychiatrist using the Yale-Brown Obsessive-Compulsive Scale (Y-BCOS).

Results:

A significant difference was observed in the change of scores on the Y-BOCS in week 12, compared with the onset of the study between the study groups (t= −8.976, df=38, P=0.001). There was a significant difference between the study groups in obsession (F= 49.19, df= 1, P≤0.001), compulsion (F= 13.78, df= 1, P= 0.001), and OCD (F= 57.25, df= 1, P≤0.001), i.e., higher in the celecoxib group.

Conclusion:

This study showed that adjuvant treatment with celecoxib can further improve the symptoms of OCD in individuals receiving SSRIs.

A Comprehensive Review of Tic Disorders in Children

Tics are characterized by sudden, rapid, recurrent, nonrhythmic movement or vocalization, and are the most common movement disorders in children. Their onset is usually in childhood and tics often will diminish within one year. However, some of the tics can persist and cause various problems such as social embarrassment, physical discomfort, or emotional impairments, which could interfere with daily activities and school performance. Furthermore, tic disorders are frequently associated with comorbid neuropsychiatric symptoms, which can become more problematic than tic symptoms. Unfortunately, misunderstanding and misconceptions of tic disorders still exist among the general population. Understanding tic disorders and their comorbidities is important to deliver appropriate care to patients with tics. Several studies have been conducted to elucidate the clinical course, epidemiology, and pathophysiology of tics, but they are still not well understood. This article aims to provide an overview about tics and tic disorders, and recent findings on tic disorders including history, definition, diagnosis, epidemiology, etiology, diagnostic approach, comorbidities, treatment and management, and differential diagnosis.

Reduced T cell immunity in unmedicated, comorbidity-free obsessive-compulsive disorder: An immunophenotyping study

BACKGROUND

Immune system aberrations have been postulated to play a role in the pathophysiology of Obsessive-compulsive disorder (OCD). This study was aimed to examine the profile of immune cell subsets in peripheral blood of un-medicated OCD patients.

METHOD

Thirteen drug-naïve/free OCD patients and twenty-six age & sex matched healthy controls were recruited. Immunophenotyping was carried out by staining the whole blood specimens with fluorescent monoclonal antibodies against the cell surface markers such as CD45, CD3, CD16, CD56, CD8, CD4, CD28, CD25 and CD127, followed by data acquisition on BD FACSVerse™ flow cytometer. The proportions of CD4 and CD8 T cells; T regulatory (Tregs), Natural Killer (NK) cells and NK-T cells were compared between patients with OCD and healthy control subjects.

RESULTS

Significantly reduced percentage of T regulatory (Treg) cells was observed in individuals with OCD compared to healthy control subjects [1.0 ± 0.7 vs. 1.9 ± 1.4; p = 0.03, r = 0.33].

CONCLUSION

Treg cells play a crucial role in regulating the immune response, especially by suppressing the functional activities of T cells. In this study, decreased population of Treg cells essentially indicates a dysregulated T cell and/or T cell mediated immune activation in drug-naïve OCD patients. This preliminary observation might form the basis of further studies examining the immuno-inflammatory/autoimmune origin of OCD.

Immunological Dysfunction in Tourette Syndrome and Related Disorders

Chronic tic disorder and Tourette syndrome are common childhood-onset neurological diseases. However, the pathophysiology underlying these disorders is unclear, and most studies have focused on the disinhibition of the corticostriatal–thalamocortical circuit. An autoimmune dysfunction has been proposed in the pathogenetic mechanism of Tourette syndrome and related neuropsychiatric disorders such as obsessive–compulsive disorder, autism, and attention-deficit/hyperactivity disorder. This is based on evidence from animal model studies and clinical findings. Herein, we review and give an update on the clinical characteristics, clinical evidence, and genetic studies in vitro as well as animal studies regarding immune dysfunction in Tourette syndrome.

Immune function changes of the IDPN-induced Tourette syndrome rat model

There may be immunologic alternations during Tourette syndrome (TS) development. This study aimed to determine the immune function changes in different aspects (spleen or thymus index, plasma cytokines, and T cell) in an 3,3'-iminodipropionitrile (IDPN)-induced rat model of TS. Male Sprague-Dawley rats were assigned to control and TS groups. The control group received intraperitoneal infections of normal saline (5 ml kg^-1  day^-1 ), and the TS rats were injected with IDPN (150 mg kg^-1  day^-1 ). The spleen and thymus indices were calculated. The expression of anti-inflammatory cytokines and inflammatory cytokines TNF-α, in peripheral blood were measured by ELISA and Western blotting. The proportion of CD3+, CD4+, CD8+, Treg, Th1, and Th2 cells were determined by fluorescence-activated cell sorting analysis. After 1 week of IDPN treatment, TS rats had decreased spleen and thymus weights versus control. The plasma levels of IL-4, IL-10, IL-12, IFN-γ, and TNF-α were significantly increased, while no significant difference in TGF-β was found. Flow cytometry analysis demonstrated that TS rats had significantly reduced CD3+ and CD4+ cells in spleen, without any change in the proportion of CD8+ cells. Furthermore, the ratio of Treg cells (CD4+/CD25+/FoxP3+) was decreased in TS rats; simultaneously, Th1 cells (CD4+/IFN-γ+) and Th2 cells (CD4+/IL4+) were dramatically increased. Together, IDPN can trigger immune dysfunction through impairment of matured Th cells, in particular for the Treg subset.

An examination of the relationship between regulatory T cells and symptom flare-ups in children and adolescents diagnosed with chronic tic disorder and Tourette syndrome

BACKGROUND

Tourette syndrome (TS) is a childhood-onset neurodevelopmental disorder characterized by several motor and phonic tics.

AIMS

In this study, we aimed to compare activated regulatory T cell (Treg) values between patients with TS/chronic tic disorder (CTD) and age- and sex-matched healthy controls (HCs).

MATERIALS AND METHOD

Patients with TS/CTD and age- and sex-matched HCs were included in the study. The severity of the disease was evaluated using the Yale Global Tic Severity Scale. CD4⁺CD25⁺CD127^low Tregs from the patient group and the control group were compared using flow cytometry.

RESULTS

The study included 48 patients diagnosed with TS/CTD (36 males and 12 females, mean age: 11.58 ± 2.61) and 24 HCs (18 males and 6 females, mean age: 11.63 ± 2.60). The TS/CTD group had significantly higher activated regulatory T percentile with respect to the T helper value compared to the HCs (p = 0.010). Lymphocyte count, T lymphocyte count, T lymphocyte percentage, T-helper lymphocyte count, and T-helper lymphocyte percentage were lower in the patient group compared to the control group (p = 0.024, 0.003, 0.007, <0.001, <0.001, respectively). The comparison of three groups (mild, moderate-severe, and HCs) revealed that T lymphocyte number and percentage and the T helper number and percentage were significantly higher in the HC group compared to the moderate-severe group, whereas the activated Treg percentage with respect to the T helper value was significantly higher in the moderate-severe group compared to the HC group (0.002, 0.026, <0.001, <0.001, 0.027, respectively).

CONCLUSION

Our results suggest that Tregs may have a role in the pathogenesis of TS/CTD.

Pediatric Acute-Onset Neuropsychiatric Syndrome: A Data Mining Approach to a Very Specific Constellation of Clinical Variables

Objectives: Pediatric acute onset neuropsychiatric syndrome (PANS) is a clinically heterogeneous disorder presenting with: unusually abrupt onset of obsessive compulsive disorder (OCD) or severe eating restrictions, with at least two concomitant cognitive, behavioral, or affective symptoms such as anxiety, obsessive-compulsive behavior, and irritability/depression. This study describes the clinical and laboratory variables of 39 children (13 female and 26 male) with a mean age at recruitment of 8.6 years (standard deviation 3.1). Methods: Using a mathematical approach based on Artificial Neural Networks, the putative associations between PANS working criteria, as defined at the NIH in July 2010 (Swedo et al. 2012), were explored by the Auto Contractive Map (Auto-CM) system, a mapping method able to compute the multidimensional association of strength of each variable with all other variables in predefined dataset. Results: The PANS symptoms were strictly linked to one another on the semantic connectivity map, shaping a central "diamond" encompassing anxiety, irritability/oppositional defiant disorder symptoms, obsessive-compulsive symptoms, behavioral regression, sensory motor abnormalities, school performance deterioration, sleep disturbances, and emotional lability/depression. The semantic connectivity map also showed the aggregation between PANS symptoms and laboratory and clinical variables. In particular, the emotional lability/depression resulted as a highly connected hub linked to autoimmune disease in pregnancy, allergic and atopic disorders, and low Natural Killer percentage. Also anxiety symptoms were shown to be strongly related with recurrent infectious disease remarking the possible role of infections as a risk factor for PANS. Conclusion: Our data mining approach shows a very specific constellation of symptoms having strong links to laboratory and clinical variables consistent with PANS feature.

What Does Immunology Have to Do With Normal Brain Development and the Pathophysiology Underlying Tourette Syndrome and Related Neuropsychiatric Disorders?

Objective: The goal of this article is to review the past decade's literature and provide a critical commentary on the involvement of immunological mechanisms in normal brain development, as well as its role in the pathophysiology of Tourette syndrome, other Chronic tic disorders (CTD), and related neuropsychiatric disorders including Obsessive-compulsive disorder (OCD) and Attention deficit hyperactivity disorder (ADHD). Methods: We conducted a literature search using the Medline/PubMed and EMBASE electronic databases to locate relevant articles and abstracts published between 2009 and 2020, using a comprehensive list of search terms related to immune mechanisms and the diseases of interest, including both clinical and animal model studies. Results: The cellular and molecular processes that constitute our "immune system" are crucial to normal brain development and the formation and maintenance of neural circuits. It is also increasingly evident that innate and adaptive systemic immune pathways, as well as neuroinflammatory mechanisms, play an important role in the pathobiology of at least a subset of individuals with Tourette syndrome and related neuropsychiatric disorders In the conceptual framework of the holobiont theory, emerging evidence points also to the importance of the "microbiota-gut-brain axis" in the pathobiology of these neurodevelopmental disorders. Conclusions: Neural development is an enormously complex and dynamic process. Immunological pathways are implicated in several early neurodevelopmental processes including the formation and refinement of neural circuits. Hyper-reactivity of systemic immune pathways and neuroinflammation may contribute to the natural fluctuations of the core behavioral features of CTD, OCD, and ADHD. There is still limited knowledge of the efficacy of direct and indirect (i.e., through environmental modifications) immune-modulatory interventions in the treatment of these disorders. Future research also needs to focus on the key molecular pathways through which dysbiosis of different tissue microbiota influence neuroimmune interactions in these disorders, and how microbiota modification could modify their natural history. It is also possible that valid biomarkers will emerge that will guide a more personalized approach to the treatment of these disorders.

Diagnosis in PANDAS: An Update

Background:

The last twenty years have seen major advancements in unraveling the etiology and the identification of biological markers of Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococci (PANDAS). However, this body of evidence has not yet been translated into a clinical setting.

Objective:

We will review the most important studies to date on PANDAS, emphasizing those whose advances could improve the diagnosis of these disorders. We also suggest the need for updated diagnosis criteria integrating the recent findings from the hereby included studies.

Methods:

Consulting the PubMed database, a literature review of the last twenty-one years (between 1998 and 2019) was carried out using the terms “PANDAS” and “pediatric autoimmune neuropsychiatric disorders” in combination with “diagnosis” and “markers”. The search resulted in 175 hits from which we selected clinical cases, original investigations, and clinical reviews.

Results:

This review offers a compilation of the most important studies performed to date regarding the clinical presentation and potential biological markers of PANDAS. Moreover, we suggest the refinement of some aspects in the current diagnosis criteria, such as focusing on specific symptoms and the inclusion of neuroimaging and peripheral markers.

Conclusion:

The identification of specific biological markers in PANDAS is crucial for its diagnosis and opportune treatment. Future research will determine whether PANDAS require separated diagnostic and therapeutic measures or if it should be included in recently proposed categories such as Pediatric Acute Neuropsychiatric Syndrome (PANS) or Childhood Acute Neuropsychiatric Syndrome (CANS).

Altered frequencies of Th17 and Treg cells in children and adolescents with obsessive-compulsive disorder

OBJECTIVE

Obsessive-compulsive disorder (OCD) is a debilitating neuropsychiatric disorder with an etiopathophysiology that seems to include immune alterations. Previous studies have suggested that variations in the levels of circulating T cell subpopulations may be involved in psychiatric diseases. However, the role of these cells in OCD remains unexplored. Hence, the present study aimed to examine the levels of T helper 1 (Th1), Th2, Th17 and regulatory T (Treg) cells in patients with early-onset OCD and healthy controls.

METHODS

The assessment was performed in 99 children and adolescents with OCD and 46 control subjects. The percentages of circulating Th1, Th2, Th17 and Treg cells were evaluated using flow cytometry.

RESULTS

OCD patients had significantly higher levels of Th17 cells and lower percentages of Treg cells than healthy controls (p = 0.001 and p = 0.005, respectively). Furthermore, levels of Th17 cells progressively increased with the duration (p = 0.005) and severity of OCD (p = 0.008), whereas the percentages of Treg cells significantly declined with the duration of the disorder (p = 1.8 × 10^-5).

CONCLUSIONS

These results provide more evidence of the involvement of immune dysregulation, specifically an imbalance in the levels of circulating T helper and regulatory T cells, in the pathophysiology of early-onset OCD.

Antibodies to neuronal surface proteins in Tourette Syndrome: Lack of evidence in a European paediatric cohort

In Tourette Syndrome (TS) a role for autoantibodies directed against neuronal proteins has long been suspected, but so far results are still inconsistent. The aim of this study was to look for antibodies to specific or undefined neuronal proteins that could be involved in the aetiology of the disease. Sera from children with Tourette Syndrome or another chronic tic disorder (TS/TD), collected as part of the longitudinal European Multicenter Tics in Children Study, were investigated. Participants included 30 siblings of patients with TS/TD prior to developing tics (preclinical stage) and the same children after the first tic onset (onset), and 158 patients in the chronic phase undergoing an acute relapse (exacerbation). Presence of antibodies binding to rodent brain tissue was assessed by immunohistology on rat brain sections and by immunofluorescent staining of live hippocampal neurons. Live cell-based assays were used to screen for antibodies to NMDAR, CASPR2, LGI1, AMPAR and GABA_AR. Immunohistology indicated evidence of antibodies reactive with brain tissue, binding mainly to the hippocampus, the basal ganglia or the cerebellum in 26/218 (12%), with 8% of the preclinical or onset sera binding to the dentate gyrus/CA3 region or cerebellum. Only two individuals (one pre-clinical, one chronic) had antibodies binding the NMDAR and the binding was only weakly positive. No other specific antibodies were detected. Despite some immunoreactivity towards neuronal antigens on brain tissue, this was not mirrored by antibodies binding to live neurons, suggesting the presence of non-specific antibodies or those that bind non-pathogenic intracellular epitopes. NMDAR or the other neuronal surface antibodies tested were very infrequent in these patients. The evidence for pathogenic antibodies that could be causative of TS is weak.

The Glutamate and the Immune Systems: New Targets for the Pharmacological Treatment of OCD

BACKGROUND

In the last decades the pharmacological treatment of obsessivecompulsive disorder (OCD) has been significantly promoted by the effectiveness of selective serotonin (5-HT) reuptake inhibitors (SSRIs) and the subsequent development of the 5-HT hypothesis of OCD. However, since a large majority of patients (between 40% and 60 %) do not respond to SSRIs or strategies based on the modulation of the 5-HT system, it is now essential to search for other possible therapeutic targets.

AIMS

The aim of this paper was to review current literature through a PubMed and Google Scholar search of novel hypotheses and related compounds for the treatment of OCD, with a special focus on the glutammate and the immune systems.

DISCUSSION

The literature indicates that glutamate, the main excitatory neurotransmitter, might play an important role in the pathophysiology of OCD. In addition, a series of clinical studies also supports the potential efficacy of drugs modulating the glutamate system. The role of the immune system alterations in OCD in both children and adults needs to be more deeply elucidated. In children, a subtype of OCD has been widely described resulting from infections driven by group A streptococcus β-hemolitic and belonging to the so-called "pediatric autoimmune neuropsychiatric disorders associated with streptococcus" (PANDAS). In adults, available findings are meager and controversial, although interesting.

CONCLUSION

The glutamate and the immune systems represent two intriguing topics of research that hold promise for the development of open novel treatment strategies in OCD.

Sex differences in the genetic architecture of obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is a highly heritable complex phenotype that demonstrates sex differences in age of onset and clinical presentation, suggesting a possible sex difference in underlying genetic architecture. We present the first genome-wide characterization of the sex-specific genetic architecture of OCD, utilizing the largest set of OCD cases and controls available from the Psychiatric Genomics Consortium. We assessed evidence for several mechanisms that may contribute to sex differences including a sex-dependent liability threshold, the presence of individual sex-specific risk variants on the autosomes and the X chromosome, and sex-specific pleiotropic effects. Furthermore, we tested the hypothesis that genetic heterogeneity between the sexes may obscure associations in a sex-combined genome-wide association study. We observed a strong genetic correlation between male and female OCD and no evidence for a sex-dependent liability threshold model, suggesting that sex-combined analysis does not suffer from widespread loss of power because of genetic heterogeneity between the sexes. While we did not detect any significant sex-specific genome-wide single nucleotide polymorphisms (SNP) associations, we did identify two significant gene-based associations in females: GRID2 and GRP135, which showed no association in males. We observed that the SNPs with sexually differentiated effects showed an enrichment of regulatory variants influencing expression of genes in brain and immune tissues. These findings suggest that future studies with larger sample sizes hold great promise for the identification of sex-specific genetic risk factors for OCD.

Immune system and obsessive-compulsive disorder

BACKGROUND

Recently, much attention has been devoted to the possible alterations of the immune system in obsessive-compulsive disorder (OCD). Therefore, the aim of this paper was to review the current literature on the relationships between OCD and immune system.

METHODS

A PubMed and Google Scholar search was performed with specific keywords.

RESULTS

In the childhood, much emphasis has been given to the relationship between group A Streptococcus (GAS) infection and the development of a group of clinical syndromes characterized by neuropsychiatric symptoms known as "pediatric autoimmune neuropsychiatric disorders associated with streptococcus" (PANDAS). However, more recently, PANDAS has been reconsidered and evolved towards pediatric acute-onset neuropsychiatric syndrome (PANS) and/or Childhood Acute Neuropsychiatric Syndrome (CANS) all characterized by the presence of typical of OCD symptoms and tics. In adult OCD patients, different immunological parameters have been described to differ from those of healthy control subjects, although a few numbers of studies were carred out and most of them performed in small samples.

CONCLUSIONS

Although the exact relationships between OCD and immune processes are still unclear, available literature supports their role in the pathophysiology of OCD, while providing a fascinating hint for possible immunotherapeutic treatments in OCD.

Tics and Tourette: a clinical, pathophysiological and etiological review

PURPOSE OF REVIEW

Describe developments in the etiological understanding of Tourette syndrome.

RECENT FINDINGS

Tourette syndrome is a complex heterogenous clinical syndrome, which is not a unitary entity. Pathophysiological models describe gamma-aminobutyric acid-ergic-associated disinhibition of cortico-basal ganglia motor, sensory and limbic loops. MRI studies support basal ganglia volume loss, with additional white matter and cerebellar changes. Tourette syndrome cause likely involves multiple vulnerability genes and environmental factors. Only recently have some vulnerability gene findings been replicated, including histidine decarboxylase and neurexin 1, yet these rare variants only explain a small proportion of patients. Planned large genetic studies will improve genetic understanding. The role of inflammation as a contributor to disease expression is now supported by large epidemiological studies showing an association with maternal autoimmunity and childhood infection. Investigation of blood cytokines, blood mRNA and brain mRNA expression support the role of a persistent immune activation, and there are similarities with the immune literature of autistic spectrum disorder. Current treatment is symptomatic, although there is a better appreciation of factors that influence treatment response.

SUMMARY

At present, therapeutics is focused on symptom-based treatments, yet with improved etiological understanding, we will move toward disease-modifying therapies in the future.

An expert opinion on PANDAS/PANS: highlights and controversies

OBJECTIVES

'Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections' (PANDAS) identified a unique subgroup of patients with abrupt onset of obsessive compulsive disorder (OCD) symptoms clinically related to Streptococcus infection and accompanied by neuropsychological and motor symptoms. After almost 20 years, PANDAS has not been accepted as distinct disorder and new criteria for paediatric acute-onset neuropsychiatric syndrome (PANS) have been replaced it, highlighting the fact that several agents rather than only Streptococcus might be involved.

METHODS

Extensive review of the PANDAS/PANS literature was performed on PubMed.

RESULTS

Although antibiotics have been reported to be effective for acute and prophylactic phases in several uncontrolled studies and non-steroidal anti-inflammatory drugs (NSAID) are used during exacerbations, clinical multicenter trials are still missing. Selective serotonin reuptake inhibitors (SSRIs) and cognitive behavioural therapy (CBT) are still the first line of recommendation for acute onset OCD spectrum. Immunological therapies should be restricted to a few cases.

CONCLUSIONS

While PANDAS has found no confirmation as a distinct syndrome, and it is not presented in DSM-5, patients with acute onset OCD spectrum, neurocognitive and motor symptoms should be evaluated for inflammatory, infective, immunological and metabolic abnormalities with a comprehensive diagnostic algorithm.

Case-control, exploratory study of cerebrospinal fluid chemokines/cytokines and lymphocyte subsets in childhood Tourette syndrome with positive streptococcal markers

A longstanding question is whether neuroinflammation is present in children symptomatic for Tourette syndrome (TS) with positive streptococcal serology and throat cultures. The objective was to directly test for it using modern hypothesis-driven approaches. Profiling studies for 14 immune cell types (flow cytometry), 7 chemokines/cytokines (ELISA), oligoclonal bands, and other immunoglobulins were performed in this IRB-approved study of 5 children with TS and streptococcal markers compared to data from 26 non-inflammatory pediatric neurological controls. Subjects were well-characterized clinically and with standardized scales for tics and obsessions/compulsions. Three subjects with TS (60%) had positive throat cultures for Group A beta-hemolytic strep, five had elevated anti-deoxyribonuclease-B titers (mean=444), and 4 (80%) had elevated anti-streptolysin O titers (981). There were no significant differences between groups in the frequency of CSF B and T cell subsets or NK cells; the proportion of intracellularly-stained T helper type 1 (IFN-γ) or type 2 (IL-4) cells; the concentrations of B cell chemoattractants CXCL13, CXCL10; the B cell proliferation/survival cytokines BAFF and APRIL, or other chemokines (CCL19, CCL21, CCL22). None of the patients had positive CSF oligoclonal bands or an abnormal IgG index/synthesis rate. Parallel blood studies were negative. This novel study found no group CSF lymphocyte phenotypic abnormalities or elevated inflammatory mediators in childhood TS despite positive serology and throat cultures for Group A beta-hemolytic streptococci. It demonstrates feasibility of the methodology, and should serve as the basis for a larger study of putative streptococcal-associated neuroimmunological disorders.

Histamine regulation of microglia: Gene-environment interaction in the regulation of central nervous system inflammation

Microglia mediate neuroinflammation and regulate brain development and homeostasis. Microglial abnormalities are implicated in a range of neuropsychiatric pathology, including Tourette syndrome (TS) and autism. Histamine (HA) is both a neurotransmitter and an immune modulator. HA deficiency has been implicated as a rare cause of TS and may contribute to other neuropsychiatric conditions. In vitro studies suggest that HA can regulate microglia, but this has never been explored in vivo. We used immunohistochemistry to examine the effects of HA deficiency in histidine decarboxylase (Hdc) knockout mice and of HA receptor stimulation in wild-type animals. We find HA to regulate microglia in vivo, via the H4 receptor. Chronic HA deficiency in Hdc knockout mice reduces ramifications of microglia in the striatum and (at trend level) in the hypothalamus, but not elsewhere in the brain. Depletion of histaminergic neurons in the hypothalamus has a similar effect. Microglia expressing IGF-1 are particularly reduced, However, the microglial response to challenge with lipopolysacchariade (LPS) is potentiated in Hdc knockout mice. Genetic abnormalities in histaminergic signaling may produce a vulnerability to inflammatory challenge, setting the state for pathogenically dysregulated neuroimmune responses.

The Use of Deep Brain Stimulation in Tourette Syndrome

Tourette syndrome (TS) is a childhood neurobehavioural disorder, characterised by the presence of motor and vocal tics, typically starting in childhood but persisting in around 20% of patients into adulthood. In those patients who do not respond to pharmacological or behavioural therapy, deep brain stimulation (DBS) may be a suitable option for potential symptom improvement. This manuscript attempts to summarise the outcomes of DBS at different targets, explore the possible mechanisms of action of DBS in TS, as well as the potential of adaptive DBS. There will also be a focus on the future challenges faced in designing optimized trials.

Pediatric Autoimmune Disorders Associated with Streptococcal Infections and Tourette's Syndrome in Preclinical Studies

Accumulating evidence suggests that Tourette's Syndrome (TS) - a multifactorial pediatric disorder characterized by the recurrent exhibition of motor tics and/or vocal utterances - can partly depend on immune dysregulation provoked by early repeated streptococcal infections. The natural and adaptive antibody-mediated reaction to streptococcus has been proposed to potentially turn into a pathological autoimmune response in vulnerable individuals. Specifically, in conditions of increased permeability of the blood brain barrier (BBB), streptococcus-induced antibodies have been proposed to: (i) reach neuronal targets located in brain areas responsible for motion control; and (ii) contribute to the exhibition of symptoms. This theoretical framework is supported by indirect evidence indicating that a subset of TS patients exhibit elevated streptococcal antibody titers upon tic relapses. A systematic evaluation of this hypothesis entails preclinical studies providing a proof of concept of the aforementioned pathological sequelae. These studies shall rest upon individuals characterized by a vulnerable immune system, repeatedly exposed to streptococcus, and carefully screened for phenotypes isomorphic to the pathological signs of TS observed in patients. Preclinical animal models may thus constitute an informative, useful tool upon which conducting targeted, hypothesis-driven experiments. In the present review we discuss the available evidence in preclinical models in support of the link between TS and pediatric autoimmune neuropsychiatric disorders associated with streptococcus infections (PANDAS), and the existing gaps that future research shall bridge. Specifically, we report recent preclinical evidence indicating that the immune responses to repeated streptococcal immunizations relate to the occurrence of behavioral and neurological phenotypes reminiscent of TS. By the same token, we discuss the limitations of these studies: limited evidence of behavioral phenotypes isomorphic to tics and scarce knowledge about the immunological phenomena favoring the transition from natural adaptive immunity to pathological outcomes.

Association of Tic Disorders and Enterovirus Infection: A Nationwide Population-Based Study

There has been growing interest in the association between infectious disease and mental disorders, but an association between enterovirus (EV) infection and tic disorders has not been sufficiently explored. Herein, we aim to investigate the association between EV infection and incidence of tic disorders in a nationwide population-based sample using Taiwan's National Health Insurance Research Database. We identified individuals aged ≤18 years prior to 2005 with an inpatient diagnosis of EV infection and/or history of EV infection. Tic disorder was operationalized using International Classification of Disease, Revision 9, Clinical Modification (ICD-9-CM) codes 307.20-307.23. A total of 47,998 individuals with history of EV infection were compared to 47,998 sex-, age-, and urbanization-matched controls on incidence of tic disorders. The mean ± standard deviation follow-up period for all subjects was 9.7 ± 3.6 years; the mean latency period between initial EV infection and incident diagnosis of tic disorder diagnosis was 5.4 ± 2.8 years. EV infection was significantly associated with greater incidence of tic disorders (hazard ratio [HR] = 1.24, 95% CI: 1.07-1.45). When subgrouped on the basis of central nervous system (CNS) involvement, EV infection with CNS involvement was not significantly associated with greater incidence of tic disorders when compared to controls (HR = 1.25, 95% CI: 0.64-2.43); EV infection without CNS involvement was significantly associated greater incidence of tic disorders when compared to controls (HR = 1.24, 95% CI: 1.07-1.45). In addition, hospitalization for an EV infection did not increase the hazard for greater incidence of tic disorders (HR = 1.32, 95% CI: 1.04-1.67 with hospitalization and 1.22, 95% CI: 1.04-1.44 without hospitalization). EV infection is temporally associated with incidence of tic disorders. Our observations add to the growing body of literature implicating immune-inflammatory system in the pathoetiology of brain disorders in a subpopulation of individuals and serve as a clarion call for surveillance of symptoms suggestive of tic disorders in individuals with history of EV infection.

Transcriptome Analysis of the Human Striatum in Tourette Syndrome

BACKGROUND

Genome-wide association studies have not revealed any risk-conferring common genetic variants in Tourette syndrome (TS), requiring the adoption of alternative approaches to investigate the pathophysiology of this disorder.

METHODS

We obtained the basal ganglia transcriptome by RNA sequencing in the caudate and putamen of nine TS and nine matched normal control subjects.

RESULTS

We found 309 downregulated and 822 upregulated genes in the caudate and putamen (striatum) of TS individuals. Using data-driven gene network analysis, we identified 17 gene coexpression modules associated with TS. The top-scoring downregulated module in TS was enriched in striatal interneuron transcripts, which was confirmed by decreased numbers of cholinergic and gamma-aminobutyric acidergic interneurons by immunohistochemistry in the same regions. The top-scoring upregulated module was enriched in immune-related genes, consistent with activation of microglia in patients' striatum. Genes implicated by copy number variants in TS were enriched in the interneuron module, as well as in a protocadherin module. Module clustering revealed that the interneuron module was correlated with a neuronal metabolism module.

CONCLUSIONS

Convergence of differential expression, network analyses, and module clustering, together with copy number variants implicated in TS, strongly implicates disrupted interneuron signaling in the pathophysiology of severe TS and suggests that metabolic alterations may be linked to their death or dysfunction.

Streptococcal infection and immune response in children with Tourette's syndrome

BACKGROUND

Streptococcal infection and basal ganglia inflammation are hypothesized to be involved in Tourette's syndrome (TS). There is a need for effective therapies for managing TS. We studied streptococcal infection and immunity in TS following immunomodulator (pidotimod) therapy.

METHODS

Blood samples from 58 patients with TS and 128 age-matched healthy controls enabled measurement of antistreptolysin O (ASO), T cells, natural killer (NK) cells, interleukin-6 (IL-6) and interleukin-8 (IL-8), and tumor necrosis factor-α (TNF-α). Forty-four patients with abnormal T cell numbers were divided into two groups and treated with pidotimod granules (pidotimod group, n = 20) or pidotimod plus dopaminergic receptor antagonists (combination group, n = 24). Yale Global Tic Severity Scale (YGTSS) scores and immunologic indices were assessed after treatment.

RESULTS

An ASO >1:200 was found in 22.4% of children with TS, 7.5% of controls, and 38.9% of children with both TS and attention deficit hyperactivity disorder (ADHD) compared to 15.0% of children with TS alone (P < 0.05). Children with TS showed decreased CD3(+) and CD4(+) T cells, CD4(+)/CD8(+) ratio, IL-6 and IL-8, increased NKC and TNF-α (P < 0.05) as compared to controls. ASO-positive children with TS had lower CD4(+) T cells as compared to ASO-negative children with TS, and lower IL-6 and IL-8 levels as compared to controls (P < 0.05). After 8 weeks of pidotimod treatment, IL-8 was increased compared to either tiapride hydrochloride or haloperidol and pidotimod (P < 0.05).

CONCLUSIONS

Streptococcal infection in TS patients is associated with immune and cytokine dysfunction, which can be potentially managed with immunomodulator therapy.

Maternal history of autoimmune disease and later development of tourette syndrome in offspring

OBJECTIVE

In a nationwide prospective cohort study, we examined the possible association between maternal autoimmune disease (AD) and later diagnosis of Tourette syndrome (TS) in offspring.

METHOD

Data from national Danish health registers identified a cohort consisting of all children born in Denmark between 1990 and 2007 (n = 1,116,255), followed prospectively from birth until 2011, date of TS diagnosis, death, or emigration/disappearance, whichever came first. The incidence rate ratio (IRR) of TS, dependent on whether or not the mother had a prior diagnosis of AD, was estimated by Poisson regression with 95% CIs and adjusted for age, calendar time, place of birth, maternal and paternal age, parental psychiatric diagnoses other than TS, and parental TS.

RESULTS

The cohort contributed a total of 13,000,162 person years and 2,442 participants with a diagnosis of TS (414 females and 2,028 males). Prior maternal AD was found in 110 of the 2,442 children with TS, corresponding to an increased risk of TS, with an adjusted IRR of 1.22 (95% CI = 1.01-1.48). Maternal history of a prior AD increased the risk of TS in males, with an adjusted IRR of 1.29 (95% CI = 1.05-1.58), but not in females, with an adjusted IRR of 0.89 (95% CI = 0.52-1.52).

CONCLUSION

Maternal AD was associated with a 29% increased incidence rate of TS in male offspring. This finding supports the hypothesis that neuroimmunological disorders may act as a component in the etiology of a subset of TS.

Post-infectious group A streptococcal autoimmune syndromes and the heart

There is a pressing need to reduce the high global disease burden of rheumatic heart disease (RHD) and its harbinger, acute rheumatic fever (ARF). ARF is a classical example of an autoimmune syndrome and is of particular immunological interest because it follows a known antecedent infection with group A streptococcus (GAS). However, the poorly understood immunopathology of these post-infectious diseases means that, compared to much progress in other immune-mediated diseases, we still lack useful biomarkers, new therapies or an effective vaccine in ARF and RHD. Here, we summarise recent literature on the complex interaction between GAS and the human host that culminates in ARF and the subsequent development of RHD. We contrast ARF with other post-infectious streptococcal immune syndromes - post-streptococcal glomerulonephritis (PSGN) and the still controversial paediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS), in order to highlight the potential significance of variations in the host immune response to GAS. We discuss a model for the pathogenesis of ARF and RHD in terms of current immunological concepts and the potential for application of in depth "omics" technologies to these ancient scourges.

Clinical evaluation of youth with pediatric acute-onset neuropsychiatric syndrome (PANS): recommendations from the 2013 PANS Consensus Conference

On May 23 and 24, 2013, the First PANS Consensus Conference was convened at Stanford University, calling together a geographically diverse group of clinicians and researchers from complementary fields of pediatrics: General and developmental pediatrics, infectious diseases, immunology, rheumatology, neurology, and child psychiatry. Participants were academicians with clinical and research interests in pediatric autoimmune neuropsychiatric disorder associated with streptococcus (PANDAS) in youth, and the larger category of pediatric acute-onset neuropsychiatric syndrome (PANS). The goals were to clarify the diagnostic boundaries of PANS, to develop systematic strategies for evaluation of suspected PANS cases, and to set forth the most urgently needed studies in this field. Presented here is a consensus statement proposing recommendations for the diagnostic evaluation of youth presenting with PANS.

Post-infectious autoimmune disorders: Sydenham's chorea, PANDAS and beyond

Infections, and the resulting immune response to these infections, have recently received increased recognition as pathogenic mechanisms for neuropsychiatric disorders. Sydenham's chorea (SC), a widely recognized post-streptococcal autoimmune disorder, represents a model for this proposed pathogenesis. In SC, a dysregulated immune response to a streptococcal infection is hypothesized to result in inflammation of neuronal networks, particularly the basal ganglia nuclei. The resulting dysfunction in the basal ganglia nuclei are hypothesized to lead to a constellation of adventitious movements and psychiatric symptoms, which investigations have shown are amenable to immunomodulatory therapies. PANDAS (Pediatric Autoimmune Neuropsychiatric Disorder Associated with Streptococcal infections) has been proposed as a variant of SC, and is hypothesized to share a pathogenic mechanism, despite a unique symptom profile of predominantly psychiatric symptoms. In this review, we present the clinical aspects of both disorders, the data for potential shared etiopathogenesis between them, and the evidence for the therapeutic use of immunomodulatory therapies for the symptoms of SC and PANDAS. This article is part of a Special Issue entitled SI: Neuroimmunology in Health And Disease.

The role of immune mechanisms in Tourette syndrome

Tourette syndrome (TS) is a childhood-onset tic disorder associated with abnormal development of brain networks involved in the sensory and motor processing. An involvement of immune mechanisms in its pathophysiology has been proposed. Animal models based on active immunization with bacterial or viral mimics, direct injection of cytokines or patients' serum anti-neuronal antibodies, and transgenic approaches replicated stereotyped behaviors observed in human TS. A crucial role of microglia in the neural-immune crosstalk within TS and related disorders has been proposed by animal models and confirmed by recent post mortem studies. With analogy to autism, genetic and early life environmental factors could foster the involvement of immune mechanisms to the abnormal developmental trajectories postulated in TS, as well as lead to systemic immune dysregulation in this condition. Clinical studies demonstrate an association between TS and immune responses to pathogens like group A Streptococcus (GAS), although their role as risk-modifiers is still undefined. Overactivity of immune responses at a systemic level is suggested by clinical studies exploring cytokine and immunoglobulin levels, immune cell subpopulations, and gene expression profiling of peripheral lymphocytes. The involvement of autoantibodies, on the other hand, remains uncertain and warrants more work using live cell-based approaches. Overall, a body of evidence supports the hypothesis that disease mechanisms in TS, like other neurodevelopmental illnesses (e.g. autism), may involve dysfunctional neural-immune cross-talk, ultimately leading to altered maturation of brain pathways controlling different behavioral domains and, possibly, differences in organising immune and stress responses. This article is part of a Special Issue entitled SI: Neuroimmunology in Health And Disease.

The Modulating Role of Stress in the Onset and Course of Tourette’s Syndrome

Accumulating data indicate a common occurrence of tic exacerbations and periods of psychosocial stress. Patients with Tourette’s syndrome (TS) also exhibit aberrant markers of hypothalamic-pituitary-adrenal (HPA) axis activation. Based on these findings, a functional relationship between stress and tic disorders has been suggested, but the underlying mechanism of how stress may affect tic pathology remains to be elucidated. We suggest that dopaminergic and noradrenergic neurotransmission as well as immunology play a crucial role in mediating this relationship. Two possibilities of causal direction might be assumed: (a) psychosocial stress might lead to an exacerbation of tics via activation of HPA axis and subsequent changes in neurotransmission or immunology and (b) TS-related abnormalities in neurotransmission or immunology result in a higher vulnerability of affected patients to respond to psychosocial stress with a strong activation of the HPA axis. It may also be the case that both assumptions hold true and interact with each other.

Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections (PANDAS): An Evolving Concept

Pediatric autoimmune neuropsychiatric disorders associated with streptococcus infections (PANDAS) originated from the observational work of Swedo and collaborators, who formalized their definition in 1998 in a set of operational criteria. The application of these criteria, which focuses on tics and obsessive-compulsive symptoms as core symptoms, has encountered difficulties, eventually leading to a high rate of misdiagnosis. In particular, the core feature represented by the association between newly diagnosed infections and neuropsychiatric symptom relapses in youths with this diagnosis could not be demonstrated by longitudinal studies. Exploratory studies aiming to identify clinical or cognitive features that could discriminate PANDAS from other pediatric obsessive-compulsive and tic disorders present methodological limitations, and therefore are not conclusive. Other behavioral features, in addition to obsessive-compulsive symptoms and tics, have been included in pediatric acute-onset neuropsychiatric syndromes (PANS) and childhood acute neuropsychiatric syndromes (CANS), two new concepts recently proposed in order to define a much broader clinical spectrum encompassing etiologically diverse entities. Given the uncertainties on the clinical definition of PANDAS, it is not surprising that evidence in support of a post-infectious, immune-mediated pathophysiology is also insufficient. Anti-dopamine receptor antibodies might be relevant to both Sydenham's chorea (SC)-the prototypical post-streptococcal neuropsychiatric disorder-and some rare forms of encephalitis targeting the basal ganglia specifically, but studies exploring their association with children fulfilling Swedo's criteria for PANDAS have been inconclusive. Moreover, we lack evidence in favor of the efficacy of antibiotic prophylaxis or tonsillectomy in patients fulfilling Swedo's criteria for PANDAS, whereas a response to immune-mediated treatments like intravenous immunoglobulins has been documented by one study, but needs replication in larger trials. Overall, the available evidence does not convincingly support the concept that PANDAS are a well-defined, isolated clinical entity subdued by definite pathophysiological mechanisms; larger, prospective studies are necessary to reshape the nosography and disease mechanisms of post-streptococcal acute neuropsychiatric disorders other than SC. Research is also under way to shed further light on a possible relationship between streptococcal infections, other biological and psychosocial stressors, and the complex pathobiology of chronic tic disorders.

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.

Attention deficit hyperactivity disorder, tic disorder, and allergy: is there a link? A nationwide population-based study

BACKGROUND

Attention deficit hyperactivity disorder (ADHD) and tic disorder usually co-occur in the same individuals, but the underlying mechanisms remain unclear. Previous evidence has shown that a frequent coexistence of allergic diseases was noted in patients with ADHD or tic disorder. We attempted to investigate the possible link among ADHD, tic disorder, and various allergic diseases.

METHODS

Utilizing the Taiwan National Health Insurance Research Database from 1996 to 2010, 5,811 patients with ADHD alone, 1,816 patients with tic disorder alone, and 349 patients with dual diagnoses of ADHD and tic disorder were identified and compared with age-/gender-matched controls (1:4) in an investigation of the association among ADHD, tic disorder, and allergic diseases.

RESULTS

Patients with dual diagnoses of ADHD and tic disorder had a significantly higher prevalence of allergic diseases and psychiatric comorbidities, including allergic rhinitis (43% vs. 28.4% vs. 33.6% vs. 19.7%, p < 0.001), asthma (27.5% vs. 17.2% vs. 18.2% vs. 11.9%, p < 0.001), atopic dermatitis (10.6% vs. 8.4% vs. 7.0 vs. 5.9%, p < 0.001), allergic conjunctivitis (55.6% vs. 34.7% vs. 43.5% vs. 26.3%, p < 0.001), obsessive compulsive disorder (4.0% vs. 1.3% vs. 2.0% vs. 0.1%, p < 0.001), and anxiety disorder (22.1% vs. 18.0% vs. 6.0% vs. 0.5%, p < 0.001) than the ADHD alone group, the tic alone group, and the control group. Furthermore, ADHD patients with more allergic diseases (≥ 3 comorbidities: OR: 3.73, 95% CI: 2.65~5.25; 2 comorbidities: OR: 2.52, 95% CI: 1.82~3.47; 1 comorbidity: OR: 1.87, 95% CI: 1.41~2.49) exhibited an increased risk of tic disorder compared with ADHD patients without allergic disease.

CONCLUSION

  A significant association among ADHD, tic disorder, and allergic diseases was noted in our study. The results may inspire further studies to clarify the underlying mechanisms and help us understand more about the complex etiology of ADHD, tic disorder, and their co-occurrence.

Theoretical and practical considerations behind the use of laboratory animals for the study of Tourette syndrome

In the present manuscript we review a substantial body of literature describing several pre-clinical animal models designed and developed with the purpose of investigating the biological determinants of Tourette syndrome (TS). In order to map the animal models onto the theoretical background upon which they have been devised, we first define phenomenological and etiological aspects of TS and then match this information to the available pre-clinical models. Thus, we first describe the characteristic symptoms exhibited by TS patients and then a series of hypotheses attempting to identify the multifactorial causes of TS. With respect to the former, we detail the phenomenology of abnormal repetitive behaviors (tics and stereotypies), obsessive-compulsive behaviors and aberrant sensory-motor gating. With respect to the latter, we describe both potential candidate vulnerability genes and environmental factors (difficult pregnancies, psychosocial stressors and infections). We then discuss how this evidence has been translated in pre-clinical research with respect to both dependent (symptoms) and independent (etiological factors) variables. Thus, while, on the one hand, we detail the methodologies adopted to measure abnormal repetitive and obsessive-compulsive behaviors, and sensory-motor gating, on the other hand, we describe genetic engineering studies and environmental modulations aimed at reproducing the proposed biological determinants in laboratory rodents. A special emphasis is placed upon "programming" events, occurring during critical stages of early development and exerting organizational delayed consequences. In the final section, we outline a heuristic model with the purpose of integrating clinical and pre-clinical evidence in the study of TS.

Immune-mediated animal models of Tourette syndrome

An autoimmune diathesis has been proposed in Tourette syndrome (TS) and related neuropsychiatric disorders such as obsessive-compulsive disorder, attention-deficit/hyperactivity disorder, autism and anorexia nervosa. Environmental triggers including infection and xenobiotics are hypothesized to lead to the production of brain-directed autoantibodies in a subset of genetically susceptible individuals. Although much work has focused on Group A Streptococcus (GAS), the role of this common childhood infection remains controversial. Animal model studies based on immune and autoantibody findings in TS have demonstrated immunoglobulin (Ig) deposits and stereotypic movements and related behavioral disturbances reminiscent of TS following exposure to GAS, other activators of host anti-microbial responses, soluble immune mediators and anti-GAS or anti-neuronal antibodies. Demonstration of the ability to recreate these abnormalities through passive transfer of serum IgG from GAS-immunized mice into naïve mice and abrogation of this activity through depletion of IgG has provided compelling evidence in support of the autoimmune hypothesis. Immunologically-based animal models of TS are a potent tool for dissecting the pathogenesis of this serious neuropsychiatric syndrome.

Autoimmune basal ganglia disorders

The basal ganglia are deep nuclei in the brain that include the caudate, putamen, globus pallidus, and substantia nigra. Pathological processes involving the basal ganglia often result in disorders of movement and behavior. A number of different autoimmune disorders predominantly involve the basal ganglia and can result in movement and psychiatric disorders. The classic basal ganglia autoimmune disorder is Sydenham chorea, a poststreptococcal neuropsychiatric disorder. Resurgence in the interest in Sydenham chorea is the result of the descriptions of other poststreptococcal neuropsychiatric disorders including tics and obsessive-compulsive disorder, broadly termed pediatric autoimmune neuropsychiatric disorders associated with streptococcal infection. Encephalitic processes affecting the basal ganglia are also described including the syndromes basal ganglia encephalitis, encephalitis lethargica, and bilateral striatal necrosis. Last, systemic autoimmune disorders such as systemic lupus erythematosus and antiphospholipid syndrome can result in chorea or parkinsonism. Using paradigms learned from other autoantibody associated disorders, the authors discuss the autoantibody hypothesis and the role of systemic inflammation in autoimmune basal ganglia disorders. Identification of these entities is important as the clinician has an increasing therapeutic repertoire to modulate or suppress the aberrant immune system.

Infectious Agents are Associated with Psychiatric Diseases

There are several infectious agents in the environment that can cause persistent infections in the host. They usually cause their symptoms shortly after first infection and later persist as silent viruses and bacteria within the body. However, these chronic infections may play an important role in the pathogenesis of schizophrenia and Tourette’s syndrome (TS). We investigated the distribution of different neurotrophic infectious agents in TS, schizophrenia and controls. A total of 93 individuals were included (schizophrenic patients, Tourette patients and controls). We evaluated antibodies against cytomegalovirus (CMV), herpes-simplex virus (HSV), Epstein-Barr virus, Toxoplasma, Mycoplasma and Chlamydia trachomatis/pneumoniae. By comparing schizophrenia and TS, we found a higher prevalence of HSV (P=0.017) and CMV (P=0.017) antibodies in schizophrenic patients. Considering the relationship between schizophrenia, TS and healthy controls, we showed that there are associations for Chlamydia trachomatis (P=0.007), HSV (P=0.027) and CMV (P=0.029). When all measured viruses, bacteria and protozoa were combined, schizophrenic patients had a higher rate of antibodies to infectious agents than TS patients (P=0.049). Tourette and schizophrenic patients show a different vulnerability to infectious agents. Schizophrenic patients were found to have a higher susceptibility to viral infections than individuals with TS. This finding might point to a modification in special immune parameters in these diseases.

Altered monocyte activation markers in Tourette's syndrome: a case-control study

BACKGROUND

Infections and immunological processes are likely to be involved in the pathogenesis of Tourette's syndrome (TS). To determine possible common underlying immunological mechanisms, we focused on innate immunity and studied markers of inflammation, monocytes, and monocyte-derived cytokines.

METHODS

In a cross-sectional study, we used current methods to determine the number of monocytes and levels of C-reactive protein (CRP) in 46 children, adolescents, and adult patients suffering from TS and in 43 healthy controls matched for age and sex. Tumor necrosis factor alpha (TNF-alpha), interleukin 6 (IL-6), soluble CD14 (sCD14), IL1-receptor antagonist (IL1-ra), and serum neopterin were detected by immunoassays.

RESULTS

We found that CRP and neopterin levels and the number of monocytes were significantly higher in TS patients than in healthy controls. Serum concentrations of TNF-alpha, sIL1-ra, and sCD14 were significantly lower in TS patients. All measured values were within normal ranges and often close to detection limits.

CONCLUSIONS

The present results point to a monocyte dysregulation in TS. This possible dysbalance in innate immunity could predispose to infections or autoimmune reactions.

Restless legs syndrome--theoretical roles of inflammatory and immune mechanisms

Theories for restless legs syndrome (RLS) pathogenesis include iron deficiency, dopamine dysregulation and peripheral neuropathy. Increased prevalence of small intestinal bacterial overgrowth (SIBO) in controlled studies in RLS and case reports of post-infectious RLS suggest potential roles for inflammation and immunological alterations. A literature search for all conditions associated with RLS was performed. These included secondary RLS disorders and factors that may exacerbate RLS. All of these conditions were reviewed with respect to potential pathogenesis including reports of iron deficiency, neuropathy, SIBO, inflammation and immune changes. A condition was defined as highly-associated if there was a prevalence study that utilized an appropriate control group. Small case reports were recorded but not included as definite RLS-associated conditions. Fifty four diseases, syndromes and conditions have been reported to cause and/or exacerbate RLS. Of these, 38 have been reported to have a higher prevalence than age-matched controls, 9 have adequate sized reports and have general acceptance as RLS-associated conditions and 7 have been reported in case report form. Overall, 42 of the 47 RLS-associated conditions (89%) have also been associated with inflammatory and/or immune changes. In addition, 43% have been associated with peripheral iron deficiency, 40% with peripheral neuropathy and 32% with SIBO. Most of the remaining conditions have yet to be studied for these factors. The fact that 95% of the 38 highly-associated RLS conditions are also associated with inflammatory/immune changes suggests the possibility that RLS may be mediated or affected through these mechanisms. Inflammation can be responsible for iron deficiency and hypothetically could cause central nervous system iron deficiency-induced RLS. Alternatively, an immune reaction to gastrointestinal bacteria or other antigens may hypothetically cause RLS by a direct immunological attack on the central or peripheral nervous system.