Association between intracellular infectious agents and Tourette's syndrome

Molecular Landscape of Tourette's Disorder

Tourette's disorder (TD) is a highly heritable childhood-onset neurodevelopmental disorder and is caused by a complex interplay of multiple genetic and environmental factors. Yet, the molecular mechanisms underlying the disorder remain largely elusive. In this study, we used the available omics data to compile a list of TD candidate genes, and we subsequently conducted tissue/cell type specificity and functional enrichment analyses of this list. Using genomic data, we also investigated genetic sharing between TD and blood and cerebrospinal fluid (CSF) metabolite levels. Lastly, we built a molecular landscape of TD through integrating the results from these analyses with an extensive literature search to identify the interactions between the TD candidate genes/proteins and metabolites. We found evidence for an enriched expression of the TD candidate genes in four brain regions and the pituitary. The functional enrichment analyses implicated two pathways ('cAMP-mediated signaling' and 'Endocannabinoid Neuronal Synapse Pathway') and multiple biological functions related to brain development and synaptic transmission in TD etiology. Furthermore, we found genetic sharing between TD and the blood and CSF levels of 39 metabolites. The landscape of TD not only provides insights into the (altered) molecular processes that underlie the disease but, through the identification of potential drug targets (such as FLT3, NAALAD2, CX3CL1-CX3CR1, OPRM1, and HRH2), it also yields clues for developing novel TD treatments.

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.

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.

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.

Maternal immune activation and neuroinflammation in human neurodevelopmental disorders

Maternal health during pregnancy plays a major role in shaping health and disease risks in the offspring. The maternal immune activation hypothesis proposes that inflammatory perturbations in utero can affect fetal neurodevelopment, and evidence from human epidemiological studies supports an association between maternal inflammation during pregnancy and offspring neurodevelopmental disorders (NDDs). Diverse maternal inflammatory factors, including obesity, asthma, autoimmune disease, infection and psychosocial stress, are associated with an increased risk of NDDs in the offspring. In addition to inflammation, epigenetic factors are increasingly recognized to operate at the gene-environment interface during NDD pathogenesis. For example, integrated brain transcriptome and epigenetic analyses of individuals with NDDs demonstrate convergent dysregulated immune pathways. In this Review, we focus on the emerging human evidence for an association between maternal immune activation and childhood NDDs, including autism spectrum disorder, attention-deficit/hyperactivity disorder and Tourette syndrome. We refer to established pathophysiological concepts in animal models, including immune signalling across the placenta, epigenetic 'priming' of offspring microglia and postnatal immune-brain crosstalk. The increasing incidence of NDDs has created an urgent need to mitigate the risk and severity of these conditions through both preventive strategies in pregnancy and novel postnatal therapies targeting disease mechanisms.

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.

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.

Toxoplasma gondii - obsessive -compulsive disorder relationship: is it different in children?

BACKGROUND AND AIM

Obsessive-compulsive disorder (OCD) is a common neuropsychiatric illness. Although the etiology of OCD is still unknown, recent investigations have associated development of OCD with infectious illness. Toxoplasma gondii (T. gondii) is a neurotropic protozoan parasite that causes infection of the central nervous system. In the last decade, a lot of researches have focused on the possible relationship between exposure to T. gondii and neuropsychiatric disorders such as schizophrenia. Therefore, in this study, it was aimed to investigate a possible association between Toxoplasma infection and OCD in children and adolescents.

METHODS

We selected 55 patients with OCD (aged between 7 and 16 years) and 59 healthy children and adolescents (aged between 7 and 16 years), and investigated the seropositivity rate for anti-Toxoplasma IgG antibodies by enzyme-linked immunosorbent assay.

RESULTS

The seropositivity rate for anti-T. gondii IgG antibodies among OCD patients (21.82%) was found to be higher than the rate in control group (15.25%). However, the difference between the OCD group and the control group was not statistically significant (p > .05).

CONCLUSION

In contrast to studies in adult patients, the results of this study do not support the relationship between T. gondii and OCD children and adolescents.

Seroprevalance Anti-Toxoplasma gondii antibodies in children and adolescents with tourette syndrome/chronic motor or vocal tic disorder: A case-control study

Toxoplasma gondii infection may be associated with psychiatric disorders due to its neurological effects. The purpose of this study was to investigate the relation between tic disorders in children and adolescents and Anti-Toxoplasma IgG. 43 children diagnosed with Tourette's syndrome(TS) and 87 with chronic motor or vocal tic disorder(CMVTD), and 130 healthy volunteers, all aged 7-18, were enrolled. Anti-Toxoplasma IgG antibody levels obtained from blood specimens were investigated. Toxoplasma IgG positivity was determined in 16(37.2%) of the patients with TS, in 27(31%) of those with CMVTD and in 12(9.2%) members of the control group. Anti-Toxoplasma gondii antibody positivity was 5.827-fold higher in subjects with TS and 4.425-fold higher in subjects with CMVTD compared to the control group. Correlation was determined between a diagnosis of TS or CMVTD and Anti-Toxoplasma gondii antibodies. We think that it will be useful for the neuropsychiatric process associated with Anti-Toxoplasma gondii antibodies to be clarified.

Increased Risk of Tics in Children Infected with Enterovirus: A Nationwide Population-Based Study

OBJECTIVE

Both tics and enterovirus (EV) infections are common in children. The association between EV infections and tics has been seldom evaluated. The aim of this study was to evaluate the risk of diagnosed tics after EV infections in children.

METHODS

A nationwide retrospective cohort study was conducted to determine the risk of tics after EV infections by analyzing data from the National Health Insurance Research Database in Taiwan. Children aged < 18 years with EV infection during 2000 to 2007 were enrolled. For comparison, non-EV-infected children were randomly selected and matched with EV-infected children at a 1:1 ratio according to sex, age, urbanization level, parental occupation, and the year of EV infection. All patients were followed up until the diagnosis of tics, death, loss to follow-up, withdrawal from the insurance system, or December 31, 2008.

RESULTS

A total of 282,321 EV-infected and 282,317 non-EV-infected children were included in this study. The mean age was 2.39 years in both cohorts. The overall incidences of tics were 9.12 and 6.21 per 10,000 person-years in the EV-infected and non-EV-infected cohorts, respectively. Children with EV infection were significantly associated with an increased risk of tics compared with those without EV infection (adjusted hazard ratio, 1.38; 95% confidence interval, 1.27-1.5). Multivariable analyses showed that boys, children living in urbanized areas, children whose parents had white-collar jobs, and children with allergic rhinitis or bronchial asthma exhibited a significantly increased risk of tics.

CONCLUSION

This study revealed an increased risk of tics after EV infection in children.

Psychiatric aspects of toxoplasmosis: an Indian perspective

Toxoplasma gondii is one of the well-studied parasites because of its medical and veterinary importance, and its suitability as a model for cell biology and molecular studies. Latent toxoplasmosis in an immunocompetent host was considered benign until recently. The importance of this parasite has been steadily rising in the field of psychiatry and neurology as it has been implicated in numerous neuropsychiatric disorders. Researchers in India have unfortunately restricted themselves to finding the prevalence of toxoplasma antibodies in special populations and animals. On the other hand, there has been increasing research interest worldwide in T. gondii for its effects on human behaviour, manifestations of which range from psychoses and neuroses to Alzheimer's and Parkinson's disease. Toxoplasma infected organisms may be akin to living zombies. From changing the core natural defensive behaviour in mice to changing personality & leading to neuropsychiatric disorders in humans, Toxoplasma brings about subtle but significant & specific changes in its host. Surprisingly there is severe dearth of such studies from India even though prevalence rates of latent Toxoplasma infection are comparable, or in some regions, higher to those found elsewhere in the world. The potential for identifying Toxoplasma induced behavioural alterations is enormous in this part of the world which could have future treatment implications. It's high time that we move beyond researching the obvious and involve ourselves in more rigorous, novel and stimulating studies in the future.

Mental Health Disorders Associated with Foodborne Pathogens

Human infections with foodborne pathogenic organisms are relatively well described in terms of their overt physical symptoms, such as diarrhea, abdominal cramps, vomiting, fever, and associated sequelae. Indeed, some of these are key for diagnosis and treatment, although it should be noted that, for some foodborne pathogens, the physical symptoms might be more diffuse, particularly those associated with some of the foodborne parasites. In contrast, the impact of these pathogens on mental health is less well described, and symptoms such as depression, anxiety, and general malaise are usually ignored when foodborne infections are recorded. Despite this, it is generally accepted that there are several psychiatric disorders of unknown etiology that may be associated with microbial pathogens. Depression, autism, hypochondriasis and anxiety, schizophrenia, and Tourette syndrome probably have multiple contributing causes, among which foodborne pathogens may play a decisive or contributory role, possibly sharing pathophysiological pathways with other environmental triggers. This review focuses on foodborne parasites and bacterial pathogens. Some foodborne parasites, such as metacestodes of Taenia solium and tissue cysts (bradyzoites) of Toxoplasma gondii , may affect mental health by directly infecting the brain. In contrast, bacterial infections and other parasitic infections may contribute to mental illness via the immune system and/or by influencing neurotransmission pathways. Thus, cytokines, for example, have been associated with depression and schizophrenia. However, infectious disease models for psychiatry require a more complete understanding of the relationship between psychiatric disorders and microbial triggers. This article reviews the current state of knowledge on the role of foodborne parasitic and bacterial pathogens in mental illness and identifies some of the gaps that should be addressed to improve diagnosis and treatment of mental health issues that are not solely related to psychiatric factors.

Addressing the Complexity of Tourette's Syndrome through the Use of Animal Models

Tourette's syndrome (TS) is a neurodevelopmental disorder characterized by fluctuating motor and vocal tics, usually preceded by sensory premonitions, called premonitory urges. Besides tics, the vast majority—up to 90%—of TS patients suffer from psychiatric comorbidities, mainly attention deficit/hyperactivity disorder (ADHD) and obsessive-compulsive disorder (OCD). The etiology of TS remains elusive. Genetics is believed to play an important role, but it is clear that other factors contribute to TS, possibly altering brain functioning and architecture during a sensitive phase of neural development. Clinical brain imaging and genetic studies have contributed to elucidate TS pathophysiology and disease mechanisms; however, TS disease etiology still is poorly understood. Findings from genetic studies led to the development of genetic animal models, but they poorly reflect the pathophysiology of TS. Addressing the role of neurotransmission, brain regions, and brain circuits in TS disease pathomechanisms is another focus area for preclinical TS model development. We are now in an interesting moment in time when numerous innovative animal models are continuously brought to the attention of the public. Due to the diverse and largely unknown etiology of TS, there is no single preclinical model featuring all different aspects of TS symptomatology. TS has been dissected into its key symptomst hat have been investigated separately, in line with the Research Domain Criteria concept. The different rationales used to develop the respective animal models are critically reviewed, to discuss the potential of the contribution of animal models to elucidate TS disease mechanisms.

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.

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.

Toxoplasma gondii infection and behaviour - location, location, location?

Parasite location has been proposed as an important factor in the behavioural changes observed in rodents infected with the protozoan Toxoplasma gondii. During the chronic stages of infection, encysted parasites are found in the brain but it remains unclear whether the parasite has tropism for specific brain regions. Parasite tissue cysts are found in all brain areas with some, but not all, prior studies reporting higher numbers located in the amygdala and frontal cortex. A stochastic process of parasite location does not, however, seem to explain the distinct and often subtle changes observed in rodent behaviour. One factor that could contribute to the specific changes is increased dopamine production by T. gondii. Recently, it was found that cells encysted with parasites in the brains of experimentally infected rodents have high levels of dopamine and that the parasite encodes a tyrosine hydroxylase, the rate-limiting enzyme in the synthesis of this neurotransmitter. A mechanism is proposed that could explain the behaviour changes due to parasite regulation of dopamine. This could have important implications for T. gondii infections in humans.

The Relationship between Tourette's Syndrome and Infections

Increasing evidence shows that infections and an activated immune status might be involved in the pathogene-sis of tic disorders. Studies discuss the influence of neurotrophic bacteria and viruses on different psychiatric disorders. In addition, signs of inflammation and immunological abnormalities have been described especially in schizophrenia and Tourette’s syndrome (tic disorder). Neuroimaging studies revealed increased microglial activation in psychiatric diseases; indicating an inflammatory state of the CNS.

However, it still remains unclear what the underlying mechanism is of how infectious agents could contribute to tic symp-toms. One hypothesis is that not only one particular infectious agent causes directly to the disease; instead different (chronic) infections influence the immune balance and are therefore involved in the pathology. In tic disorders, infections with group A streptococci, Borrelia burgdorferi or Mycoplasma pneumoniae seem to be associated with symptoms of the disease. Studies have shown that immunologic treatment improves and prevents the re-occurrence of clinical symptoms in Tourette’s syndrome. Also post-infectious events by cross-reactive antibodies(against M-protein) and an altered dopamine rgic(noradrenergic) neurotransmission as well as inflammatory/immunological dysregulations were considered as possible mechanisms to cause symptoms. Another contributing factor to the pathogenesis of these diseases could be an activation of the tryptophan catabolism through infectious agents. Tryptophan functions as a precursor for neurotransmitters like se-rotonin and becomes degraded to products that can modulate the neurotransmitter balance.

A deeper insight into the precise mechanism of how infectious agents influence immune parameter, tryptophan metabo-lism and the resulting neurotransmitter availability could help finding new therapeutic strategies.

Intracellular monocytic cytokine levels in schizophrenia show an alteration of IL-6

Several studies have shown an involvement of the immune system, in particular the monocytic system, in the pathophysiology of schizophrenia. Beside others, the monocyte-derived cytokines TNF-α, IL-6 and IL-10 were found to be affected. Since cytokines are secreted by several different cell types, the cellular source is only clear if intracellular levels are measured. Thus, in order to study the monocytic system in schizophrenia, the intracellular levels of TNF-α, IL-6 and IL-10 were determined. The intracellular concentration of TNF-α, IL-6 and IL-10 in CD33 positive monocytes was evaluated in schizophrenic patients and controls with monoclonal antibodies against these cytokines. In addition, in vitro stimulation with lipopolysaccharide (LPS) or poly I/C, which mimic a bacterial and viral infection, was performed before immunocytochemistry. At baseline, monocytic IL-6 levels were significantly lower in schizophrenic patients than in controls. After stimulation with LPS, compared with baseline, monocytic intracellular IL-6 production tended to increase more in schizophrenic patients. The present results provide further support for the hypothesis of an involvement of a dysfunction of the monocytic system in the pathophysiology of schizophrenia and indicate that especially the pro-inflammatory immune response seems to be impaired.

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.