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

Emerging therapies and recent advances for Tourette syndrome

Tourette syndrome is the most prevalent hyperkinetic movement disorder in children and can be highly disabling. While the pathomechanism of Tourette syndrome remains largely obscure, recent studies have greatly improved our knowledge about this disease, providing a new perspective in our understanding of this condition. Advances in electrophysiology and neuroimaging have elucidated that there is a reduction in frontal cortical volume and reduction of long rage connectivity to the frontal lobe from other parts of the brain. Several genes have also been identified to be associated with Tourette syndrome. Treatment of Tourette syndrome requires a multidisciplinary approach which includes behavioral and pharmacological therapy. In severe cases surgical therapy with deep brain stimulation may be warranted, though the optimal location for stimulation is still being investigated. Studies on alternative therapies including traditional Chinese medicine and neuromodulation, such as transcranial magnetic stimulation have shown promising results, but still are being used in an experimental basis. Several new therapies have also recently been tested in clinical trials. This review provides an overview of the latest findings with regards to genetics and neuroimaging for Tourette syndrome as well as an update on advanced therapeutics.

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.

Transcriptome-wide association study reveals increased neuronal FLT3 expression is associated with Tourette's syndrome

Tourette's Syndrome (TS) is a neurodevelopmental disorder that is characterized by motor and phonic tics. A recent TS genome-wide association study (GWAS) identified a genome-wide significant locus. However, determining the biological mechanism of GWAS signals remains difficult. To characterize effects of expression quantitative trait loci (eQTLs) in TS and understand biological underpinnings of the disease. Here, we conduct a TS transcriptome-wide association study (TWAS) consisting of 4819 cases and 9488 controls. We demonstrate that increased expression of FLT3 in the dorsolateral prefrontal cortex (DLPFC) is associated with TS. We further show that there is global dysregulation of FLT3 across several brain regions and probabilistic causal fine-mapping of the TWAS signal prioritizes FLT3 with a posterior inclusion probability of 0.849. After, we proxy the expression with 100 lymphoblastoid cell lines, and demonstrate that TS cells has a 1.72 increased fold change compared to controls. A phenome-wide association study also points toward FLT3 having links with immune-related pathways such as monocyte count. We further identify several splicing events in MPHOSPH9, CSGALNACT2 and FIP1L1 associated with TS, which are also implicated in immune function. This analysis of expression and splicing begins to explore the biology of TS GWAS signals.

Changes of Cytokines in Children With Tic Disorder

Tic disorder (TD) is a common childhood-onset disease associated with abnormal development of brain networks involved in the motor and sensory processing. The underlying pathophysiological mechanisms in TD are still unclear. An involvement of immune mechanisms in its pathophysiology has been proposed. This study investigates the association between the changes of cytokines and the etiology and development of TD. Different expressions of cytokines in a larger number of samples in our study may provide new insights to the field. The levels of cytokines (IL-2, IL-4, IL-6, IL-10, TNF-α, and IFN-γ) were evaluated in 1,724 patients who were clinically diagnosed with TD from 1 to 17.5 years old and 550 were from 6 months to 14.5 years old in the control group. We assessed the levels of cytokines according to the patient's medication status and the severity of the disease. Of the cytokines we investigated, the serum IL-6 concentration of children with TD was significantly higher than that of the control group, while the levels of other cytokines were lower in TD patients. In the patient group whose YTGSS score ranged from 1 to 9, the IL-4, IL-10, and IFN-γ levels increased in medication group compared to unmedication group. Our data suggested that the cytokines (IL-2, IL-4, IL-6, IL-10, TNF-α, and IFN-γ) may play an important role in the etiology and the severity in TD. Whether drug intervention in the early stage of tic disorder has a better effect on children needs further research.

Cytokine profile of pediatric patients with obsessive-compulsive and/or movement disorder symptoms: A review

Cytokines are an important modulator of the immune system and have been found to be altered significantly in many neurological and psychiatric disorders, like obsessive compulsive disorder (OCD) and movement disorders. Also, in pediatric autoimmune neuropsychiatric disorders associated with group A streptococcal infections (PANDAS), which are characterized by abrupt debut of symptoms of OCD and /or movement disorder symptoms, alterations in the immune system have been suggested. The aim of this paper was to review the current literature on the cytokine profile of pediatric patients with symptoms of OCD and/or movement disorder symptoms. A search of PubMed and Medline was performed with specific keywords to review studies measuring cytokines in pediatric patients with symptoms of OCD and/or movement disorders. Nineteen studies were found, twelve of which included a healthy control group, while four studies had control groups of children with other disorders, primarily neurological or psychiatric. One study compared cytokines measurements to reference intervals, and two studies had a longitudinal design. Many cytokines were found to have significant changes in patients with symptoms of OCD and/or movement disorders compared to both healthy controls and other control groups. Furthermore, differences were found when comparing cytokines in periods of exacerbation with periods of remission of symptoms in study participants. The cytokines that most studies with healthy control groups found to be significantly altered were TNF-α, IL-1β and IL-17. Although the exact role of these cytokines in OCD and movement disorder symptoms remains unclear, the available literature suggests a proinflammatory cytokine profile. This offers interesting perspectives on the pathogenesis of OCD and/or movement disorder symptoms in children, and further research into the implications of cytokines in neuropsychiatric disorders is warranted.

Immunity and Gilles de la Tourette syndrome: A systematic review and meta-analysis of evidence for immune implications in Tourette syndrome

BACKGROUND AND PURPOSE

The neurobiology of Gilles de la Tourette syndrome (GTS) is known to involve corticostriatal loops possibly under genetic control. Less is known about possible environmental triggers of GTS. Specifically, immune-related events following possible environmental inducers have been evoked, but important controversies still exist. In this systematic review and meta-analysis, we looked for evidence in favor of such possibilities.

METHODS

We performed a systematic review and meta-analysis of all immunological data in PubMed.

RESULTS

We found large discrepancies concerning immune dysfunctions in GTS, and meta-analyzing cytokines data did not allow us to conclude there is an involvement of specific cytokines in GTS neurobiology. When looking specifically at pediatric autoimmune neuropsychiatric disorder associated with streptococcus/pediatric acute onset neuropsychiatric syndrome, we found some important evidence of a possible infectious involvement but in a limited number of studies. Our meta-analysis found an increased level of anti-streptolysin O antibodies in GTS patients, but the level of anti-DNase B antibodies was not increased.

CONCLUSIONS

Too many questions still exist to allow us to definitively reach the conclusion that there is an infectious and immunological etiology in GTS. Much work is still needed to elucidate the possible role of immunology in GTS neurobiology and to favor immunological treatment rather than classical treatment.

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.

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.

Immunity in Gilles de la Tourette-Syndrome: Results From a Cerebrospinal Fluid Study

Background: Several lines of evidence support the hypothesis of an autoimmune origin of Gilles de la Tourette-Syndrome (GTS). Accordingly, in a recent study we detected positive oligoclonal bands (OCB) in cerebrospinal fluid (CSF) in >30% of adult patients indicating an intrathecal antibody synthesis. However, until today no corresponding antibodies could be identified. The aims of this study were to replicate our findings of positive OCB in an independent sample and to detect CSF autoantibodies.

Methods: In this prospective study, 20 adult patients with GTS (male: female = 18:2, median age 36.1 years ± 14.34 SD) were included. All patients were thoroughly clinically characterized. Magnetic Resonance Imaging (MRI) and CSF standard measurements were performed. Isoelectric focusing on polyacrylamide gels with silver staining was used to detect OCB. To examine specific and unspecified autoantibodies, we used transfected Human Embryonic Kidney (HEK) cells expressing different surface antigens (NMDA-, CASPR2-, LGI1-, AMPA-, or GABAB1/B), indirect immunofluorescence on different brain tissue sections, and enzyme-linked visualization. Additionally, we differentiated Glioma stem cells SY5Y (human neuroblastoma) using retinoic acid and astrocytes (rat).

Results: CSF analyses showed positive OCB (type 2) in 4/20 patients (20%). Using transfected HEK cells we did not find specific surface-autoantibodies. Immunohistochemistry on tissue-sections, SY5Y Glioma stem-cells, and astrocytes showed no specific binding patterns either.

Conclusions: Our results corroborate previous findings and demonstrate positive OCB in a substantial number of patients with GTS (prevalence in healthy controls: 5%). Although this is the largest study investigating CSF autoantibodies in GTS using several techniques, we failed to detect any specific or unspecified autoantibodies.

Immunoglobulin A Dysgammaglobulinemia Is Associated with Pediatric-Onset Obsessive-Compulsive Disorder

Background: Inflammation and immune dysregulation have been implicated in the pathogenesis of pediatric-onset obsessive-compulsive disorder (OCD) and tic disorders such as Tourette syndrome (TS). Though few replicated studies have identified markers of immune dysfunction in this population, preliminary studies suggest that serum immunoglobulin A (IgA) concentrations may be abnormal in these children with these disorders. Methods: This observational retrospective cohort study, conducted using electronic health records (EHRs), identified 206 children with pediatric-onset OCD and 1024 adults diagnosed with OCD who also had testing for serum levels of IgA. IgA deficiency and serum IgA levels in pediatric OCD were compared with IgA levels from children diagnosed with autism spectrum disorders (ASD; n = 524), tic disorders (n = 157), attention-deficit/hyperactivity disorder (ADHD; n = 534), anxiety disorders (n = 1206), and celiac disease, a condition associated with IgA deficiency (n = 624). Results: Compared with ASD and anxiety disorder cohorts, the pediatric OCD cohort displayed a significantly higher likelihood of IgA deficiency (OR = 1.93; 95% CI = 1.18-3.16, and OR = 1.98; 95% CI = 1.28-3.06, respectively), though no difference was observed between pediatric OCD and TS cohorts. Furthermore, the pediatric OCD cohort displayed similar rates of IgA deficiency and serum IgA levels when compared with the celiac disease cohort. The pediatric OCD cohort also displayed the highest percentage of IgA deficiency (15%,) when compared with TS (14%), celiac disease (14%), ADHD (13%), ASD (8%), and anxiety disorder (8%) cohorts. When segregated by sex, boys with OCD displayed a significantly higher likelihood of IgA deficiency when compared with all comparison cohorts except for celiac disease and tic disorders; no significant difference in IgA deficiency was observed between female cohorts. Pediatric OCD subjects also displayed significantly lower adjusted serum IgA levels than the ASD and anxiety disorder cohorts. Adults with OCD were also significantly less likely than children with OCD to display IgA deficiency (OR = 2.71; 95% CI = 1.71-4.28). When compared with children with celiac disease, no significant difference in IgA levels or rates of IgA deficiency were observed in the pediatric OCD cohort. Conclusions: We provide further evidence of IgA abnormalities in pediatric-onset OCD. These results require further investigation to determine if these abnormalities impact the clinical course of OCD in children.

Cytokine, chemokine and BDNF levels in medication-free pediatric patients with obsessive-compulsive disorder

The aim of this study was to investigate whether the serum levels of IL-12, IL-17, TGFβ, TNF-alpha, sTNFR1, sTNFR2, IL-1β, CCL3, CCL24, CXCL8, and BDNF are associated with obsessive-compulsive disorder (OCD) in medication-free children. A total of 44 (22 boys/22 girls) medication-free children with OCD and 40 (23 boys/17 girls) healthy controls were included in this study. The severity of the OCD symptoms were assessed by the Children's Yale-Brown Obsessive-Compulsive Scale and the Maudsley Obsessive-Compulsive Inventory. The Children's Depression Inventory and the Screen for Child Anxiety-Related Emotional Disorders were applied to the children in order to determine depression and anxiety levels. IL-17, IL-12, TGF β, TNF-alpha, sTNFR1, sTNFR2, IL-1β, CCL3, CCL24, CXCL8, and BDNF levels were measured by enzyme-linked immunosorbent assay. Multivariate analysis of covariance (MANCOVA) revealed a significant main effect on both groups for the levels of serum cytokine, chemokine, and BDNF, an effect that was independent of severities of depression and anxiety [Pillai's Trace V = 0.371, F (11, 70) = 3.756, p < 0.001, hp² = 0.187]. Analysis of covariance (ANCOVA) indicated that serum TNF-alpha levels were significantly higher in the OCD group than in the control group (p < 0.001). In contrast, serum IL-12 levels were significantly lower in the OCD group than in the control group (p = 0.014). These findings suggest that TNF-alpha and IL-12 may play a role in the pathophysiology of OCD in children. The causal relationship between these proinflammatory cytokines and pediatric OCD requires further investigation.

Inflammatory dysregulation of monocytes in pediatric patients with obsessive-compulsive disorder

BACKGROUND

Although the exact etiology of obsessive-compulsive disorder (OCD) is unknown, there is growing evidence of a role for immune dysregulation in the pathophysiology of the disease, especially in the innate immune system including the microglia. To test this hypothesis, we studied inflammatory markers in monocytes from pediatric patients with OCD and from healthy controls.

METHODS

We determined the percentages of total monocytes, CD16+ monocytes, and classical (CD14^highCD16-), intermediate (CD14^highCD16^low), and non-classical (CD14^lowCD16^high) monocyte subsets in 102 patients with early-onset OCD and in 47 healthy controls. Moreover, proinflammatory cytokine production (GM-CSF, IL-1β, IL-6, IL-8, and TNF-α) was measured by multiplex Luminex analysis in isolated monocyte cultures, in basal conditions, after exposure to lipopolysaccharide (LPS) to stimulate immune response or after exposure to LPS and the immunosuppressant dexamethasone.

RESULTS

OCD patients had significantly higher percentages of total monocytes and CD16+ monocytes than healthy controls, mainly due to an increase in the intermediate subset but also in the non-classical monocytes. Monocytes from OCD patients released higher amounts of GM-CSF, IL-1β, IL-6, IL-8, and TNF-α than healthy controls after exposure to LPS. However, there were no significant differences in basal cytokine production or the sensitivity of monocytes to dexamethasone treatment between both groups. Based on monocyte subset distribution and cytokine production after LPS stimulation, patients receiving psychoactive medications seem to have an intermediate inflammatory profile, that is, lower than non-medicated OCD individuals and higher than healthy controls.

CONCLUSIONS

These results strongly support the involvement of an enhanced proinflammatory innate immune response in the etiopathogenesis of early-onset OCD.

A cytokine study of pediatric Tourette's disorder without obsessive compulsive disorder

It has been suggested that post-infectious inflammation in central nervous system is a cause of tic disorder including Tourette's disorder (TD). Since pro-inflammatory cytokines are important mediators inducing inflammation, the cytokine levels are regarded as one of the important indicators of inflammation. Several studies have investigated the relationship of autoimmunity and the pathogenesis of TD by measuring the inflammatory cytokine levels of blood. However, when using human samples, the experimental results can be affected by the factors like size of sample, comorbidity, medication that patients take and the severity of the diseases. Thus, it is important to exclude the possibility that comorbidity and medication affects the level of inflammatory cytokines in the serum of TD patients. In our experiment, we recruited 29 patients without obsessive compulsive disorder (OCD) comorbidity and the majority of these patients did not take medication. The six pro-inflammatory cytokine levels of blood between patient and healthy groups were compared, considering the factors above, to determine more accurate results. Of the cytokines we investigated, the interleukin 12 p70 (IL-12p70) and tumor necrosis factor α (TNFα) levels increased in patient group compared to healthy controls and the patient group which have anti-streptolysin O (ASO) score under the 200 or YTGSS score from 10 to 19 also showed higher IL-12p70 or TNFα levels. In addition, the patients who did not take medication showed higher TNFα levels compared to healthy controls. In conclusion, we suggest that inflammatory pathways that involve IL-12p70 or TNFα are important to the pathogenesis of TD.

Serum cytokines in pediatric neuropsychiatric syndromes: focus on Attention Deficit Hyperactivity Disorder

BACKGROUND

Inflammation may represent a common underlying mechanism in a wide range of diseases, including neuropsychiatric disorders. Cytokine involvement has been investigated in some studies on patients with childhood neuropsychiatric diseases. The aim of this study was to determine whether cytokines are involved in ADHD to provide a rationale for immune-based therapeutic strategies in this disorder.

METHODS

Sixty children were studied: 34 consecutive drug-naïve children with ADHD (30 males and 4 females; mean age of 10.10 years, SD=2.43 age) and 26 healthy control children (22 males and 4 females; mean age of 10.70 years, SD=1.81). All cytokines but IL-2 (IL4-IL6-IL10- IL17-TNFA and IFNG) were studied by ELISAs; IL-2 was instead studied by means of paired anti-cytokine Abs and cytokine standards obtained from PharMingen.

RESULTS

Data reveal higher IL-6 and IL-10 levels in ADHD patients than in the control group (P=0.03). No differences emerged between the two groups for the other cytokines.

CONCLUSIONS

Our study showed an imbalance between pro- and anti-inflammatory cytokines that may play a pivotal role in the pathogenesis of ADHD.

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 usefulness of immunotherapy in pediatric neurodegenerative disorders: A systematic review of literature data

Immunotherapeutic strategies to treat neurodegenerative disorders have inspired the scientific community. The aim of our review is to address the translational aspects of neuroimmunology to describe the efficacy of immunotherapy in the treatment of pediatric neurodegenerative disorders. In the studies we analyzed IVIG were found to be efficient in the treatment of post-streptococcal neurodegenerative disorders, even if in PANDAS, plasma-exchange (PE) showed a higher efficiency. IVIG were also successfully used in ADEM and Guillan-Barré syndrome. In Sydenham Chorea the use of methylprednisolone was found in most cases as efficient as IVIG, while in Tourette's Syndrome, Colecoxib was successfully used in one patient. Pediatric Multiple Sclerosis seems to respond better to immunosuppressant agents (Mitoxantrone, Cyclophosphamide, Natalizumab), as well as Neuromyelitis optica (Rituximab, Mycofenolate). The importance of this review relies in the attempt to draw standardized guidelines for immunotherapy in pediatric neurodegeneratve disorders.

Cytokine correlations in youth with tic disorders

BACKGROUND

Studies have noted immunological disruptions in patients with tic disorders, including increased serum cytokine levels. This study aimed to determine whether or not cytokine levels could be correlated with tic symptom severity in patients with a diagnosed tic disorder.

METHODS

Twenty-one patients, ages 4-17 years (average 10.63±2.34 years, 13 males), with a clinical diagnosis of Tourette's syndrome (TS) or chronic tic disorder (CTD), were selected based on having clinic visits that coincided with a tic symptom exacerbation and a remission. Ratings of tic severity were assessed using the Yale Global Tic Severity Scale (YGTSS) and serum cytokine levels (interleukin [IL]-2, IL-4, IL-5, IL-10, IL-12p70, IL-13, interferon [IFN]-γ, tumor necrosis factor [TNF]-α, and granulocyte macrophage-colony stimulating factor [GM-CSF]) were measured using Luminex xMAP technology.

RESULTS

During tic symptom exacerbation, patients had higher median serum TNF-α levels (z=-1.962, p=0.05), particularly those on antipsychotics (U=9.00, p=0.033). Increased IL-13 was also associated with antipsychotic use during exacerbation (U=4.00, p=0.043) despite being negatively correlated to tic severity scores (ρ=-0.599, p=018), whereas increased IL-5 was associated with antibiotic use (U=6.5, p=0.035). During tic symptom remission, increased serum IL-4 levels were associated with antipsychotic (U=6.00, p=0.047) and antibiotic (U=1.00, p=0.016) use, whereas increased IL-12p70 (U=4.00, p=0.037) was associated with antibiotic use.

CONCLUSIONS

These findings suggest a role for cytokine dysregulation in the pathogenesis of tic disorders. It also points toward the mechanistic involvement and potential diagnostic utility of cytokine monitoring, particularly TNF-α levels. Larger, systematic studies are necessary to further delineate the role of cytokines and medication influences on immunological profiling in tic disorders.

Reduced serum TNF alpha level in chronic schizophrenia patients with or without tardive dyskinesia

BACKGROUND

Mounting evidences have demonstrated the association of altered immune factors with neurodevelopmental and pathological progression of schizophrenia. However, whether immune factors play any role in the pathogenesis of tardive dyskinesia (TD) has been underexplored. To our best knowledge, ours is among the piloting studies examining the association of TNF alpha with extrapyramidal symptoms of schizophrenic patients so far.

OBJECTIVE

The aim of this study was to assess the clinical significance of serum TNF alpha level in chronic schizophrenia, especially its potential association with TD.

METHODS

Serum TNF alpha level was measured in a sandwich enzyme-linked immunosorbent assay (ELISA) from 46 medicated chronic schizophrenia patients with TD, 43 chronic schizophrenia patients without TD, and 43 healthy control subjects. The symptoms of schizophrenia were assessed by the positive and negative syndrome scale (PANSS).

RESULTS

Chronic patients both with TD and without TD had significantly lower serum level of TNF alpha than controls (TD=9.5±2.1pg/ml, non-TD=10.7±1.8pg/ml, control=37.8±3.4pg/ml, p<0.001). Compared to patients without TD, TD patients showed marginally significant reduction in the serum TNF alpha level (p=0.05). The reduced TNF alpha level was not significantly affected by daily dose or duration of antipsychotic drugs (p>0.05). Serum TNF alpha level was negatively correlated with the PANSS total score in the whole schizophrenia patients (p<0.01), but no significant association with TD severity was observed.

CONCLUSIONS

Our results suggested that at chronic stage, serum TNF activity is associated with psychopathology of schizophrenia patients, but whether it can be a biomarker for TD needs further clarification in the future.

Impaired activation of the innate immune response to bacterial challenge in Tourette syndrome

OBJECTIVES

Infections resulting in immune activation have been proposed to play an etiological role in a subgroup of patients with Tourette syndrome (TS).

METHODS

In order to further characterize the interaction between pathogens and the innate immune system the toll-like receptor (TLR) 4 on CD14 + monocytes and soluble CD14 (sCD14) levels were analyzed in the serum of 33 Tourette patients and 31 healthy controls. Moreover, collected blood samples were stimulated with lipopolysaccharide (LPS) mimicking a bacterial infection. TLR4 was analysed by flow cytometry, sCD14 was analysed by enzyme-linked immunosorbent assay.

RESULTS

Patients had a lower receptor expression of TLR4 after stimulation with LPS (P = 0.045) and higher levels of sCD14 (unstimulated P = 0.014, after LPS P = 0.045). The increase in TLR4 expression after stimulation with LPS was significantly higher in the control group (P = 0.041).

CONCLUSIONS

Higher levels of sCD14, lower levels of TLR4 expression after stimulation and a diminished up-regulation of TLR4 expression after LPS stimulation in patients might represent an impaired activation of the innate immune response in TS, especially in regard to bacterial infection. The impaired response to pathogens could eventually lead to a higher susceptibility for infections. Recurring infections and a chronic inflammation could trigger and maintain the symptoms of TS.

Increased levels of serum neopterin in attention deficit/hyperactivity disorder (ADHD)

Attention deficit/hyperactivity disorder (ADHD) is the most frequently occurring neuropsychiatric disorder in childhood with an etiology that is not fully understood. A number of reviews that have addressed the neurobiology of ADHD have focused on imaging and genetics. Relatively little attention has been given to factors/mechanisms involved in the brain dysfunction. We suggest that changes in cellular immunity may be involved. Neopterin is a good indicator of cellular immunity, and we evaluated serum levels of neopterin in patients with ADHD. The study group consisted of 49 patients with ADHD. An age- and gender-matched control group was composed of 31 healthy subjects. Venous blood samples were collected, and the levels of neopterin were measured. The levels of neopterin were significantly higher in ADHD than in the comparison subjects. Cellular immunity may have a role in the etiopathogenesis of ADHD.

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.

Inflammation in children and adolescents with neuropsychiatric disorders: a systematic review

OBJECTIVE

There has been rapid growth in research regarding inflammation in neuropsychiatric disorders as it relates to youth. We therefore set out to systematically review the literature on inflammation and neuropsychiatric disorders in children and adolescents.

METHOD

A systematic review of the literature was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Studies were included if proinflammatory markers (PIMs) in children and/or adolescents with neuropsychiatric disorders were measured.

RESULTS

Sixty-seven studies were included, involving 3,952 youth. Evidence for a proinflammatory state is strongest for autism spectrum disorders (ASD). PIMs are elevated in children and adolescents with major depressive disorder (MDD), bipolar disorder (BD), post-traumatic stress disorder (PTSD), obsessive-compulsive disorder (OCD), Tourette's disorder (TD), attention-deficit/hyperactivity disorder (ADHD), and schizophrenia (SZ). However, the data are inconsistent. Evidence for specific PIMs is equivocal at this stage, although the findings in youth with MDD, BD, and PTSD converge with the extant adult literature in these areas. Definitive conclusions are limited by methodologic factors including cross-sectional and retrospective study design, between-study differences in specific markers and methods of analysis, small sample size, and other sources of heterogeneity.

CONCLUSION

The literature regarding inflammation among children and adolescents with neuropsychiatric disorders represents nearly 4,000 youth. There is preliminary evidence for elevated markers of inflammation in this population. Larger, prospective studies are needed to realize the goal of inflammatory markers informing clinical practice. In the interim, present findings suggest that further examination of this topic is warranted.

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.

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.