Abnormalities of neurotransmitter and neuropeptide systems in human neuroepithelioma cells infected by three Toxoplasma strains

Silent Infections are not So Silent: The Emerging Role of Combined Infections, Inflammation, and Vitamin Levels in OCD

Objective

Recent evidence highlights that different agents may trigger immune-mediated processes involved in the pathophysiology of different neuropsychiatric conditions. Given the limited information on obsessive-compulsive disorder (OCD), the present study aimed at assessing current/past infections and plasma levels of vitamin D, vitamin B12, folic acid, homocysteine and common peripheral inflammatory markers in a group of OCD outpatients.

Method

The sample included 217 adult outpatients with an OCD diagnosis according to the DSM-5 criteria. The Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) was used to assess the clinical phenotype and symptom severity. Laboratory blood tests measured levels of vitamin D, vitamin B12, folic acid, homocysteine, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), blood count and antibodies titers for cytomegalovirus (CMV), Epstein Barr virus (EBV), Toxoplasma gondii and antistreptolysin titer.

Results

Sixty-one patients had a previous EBV infection, 46 were seropositive for CMV IgG, 24 showed positive antistreptolysin titer, 14 were seropositive for Toxoplasma gondii IgG, and four for CMV IgM. More than a half of patients showed vitamin D insufficiency. Compared to seronegative patients, patients with a past EBV infection displayed significantly higher scores on the Y-BOCS total score and compulsion subscale, and other symptoms. Vitamin D was negatively correlated with both the Y-BOCS total score and the subscales scores. Folic acid was negatively correlated with the Y-BOCS total and obsessions subscale score.

Conclusions

The findings of our study show an association between Epstein-Barr infection and hypovitaminosis D and the overall severity and specific symptom patterns of OCD. The laboratory measures used in this study are useful, cheap and easy parameters that should be routinely assessed in patients with OCD. Further studies are needed to clarify their role in OCD pathophysiology and outcomes, as well as the potential therapeutic impact of vitamins and antibiotics/immunomodulatory agents in OCD and other psychiatric conditions.

The Relationship of Latent Toxoplasmosis and Cigarette Smoking: Seroprevalence, Risk Factor, and Case-Control Study in Fars Province, Southern Iran

Toxoplasmosis is a parasitic disease with worldwide prevalence. Despite the relatively similar effects of toxoplasmosis and smoking on alteration in neurotransmitters, especially dopamine, little is known about the relation of Toxoplasma gondii infection and addiction to cigarette smoking. Therefore, the main objective of this study was to assess the relationship between latent toxoplasmosis and smoking. Through a case-control study, 216 regular cigarette smokers and 324 nonsmoker age- and gender-matched subjects were evaluated for anti-T.gondii IgG antibodies with enzyme-linked immunosorbent assay (ELISA). During the sampling, a structured questionnaire was used to obtain the demographic information of participants and the risk factors of acquired Toxoplasma. The median ages of case and control groups were 51.04 ± 18.1 (22-97 years) and 51.03 ± 16.5 (21-89 years), respectively (p = 0.99). Anti-T.gondii IgG antibodies were detected in 44 (20.37%) cases and in 135 (41.67%) controls. There was a statistically significant difference for the positivity rate between the smokers and the control group (OR = 0.35; 95%CI: 0.19-0.65; and p = 0.001). The overall prevalence was 33.14%. This study indicated the inverse association between seropositivity to Toxoplasma infection and cigarette smoking. This relationship could be due to the changes that latent toxoplasmosis has on the neurotransmitters, especially dopamine, which needs more research.

Unifying Virulence Evaluation in Toxoplasma gondii: A Timely Task

Toxoplasma gondii, a major zoonotic pathogen, possess a significant genetic and phenotypic diversity that have been proposed to be responsible for the variation in clinical outcomes, mainly related to reproductive failure and ocular and neurological signs. Different T. gondii haplogroups showed strong phenotypic differences in laboratory mouse infections, which provide a suitable model for mimicking acute and chronic infections. In addition, it has been observed that degrees of virulence might be related to the physiological status of the host and its genetic background. Currently, mortality rate (lethality) in outbred laboratory mice is the most significant phenotypic marker, which has been well defined for the three archetypal clonal types (I, II and III) of T. gondii; nevertheless, such a trait seems to be insufficient to discriminate between different degrees of virulence of field isolates. Many other non-lethal parameters, observed both in in vivo and in vitro experimental models, have been suggested as highly informative, yielding promising discriminatory power. Although intra-genotype variations have been observed in phenotypic characteristics, there is no clear picture of the phenotypes circulating worldwide; therefore, a global overview of T. gondii strain mortality in mice is presented here. Molecular characterization has been normalized to some extent, but this is not the case for the phenotypic characterization and definition of virulence. The present paper proposes a baseline (minimum required information) for the phenotypic characterization of T. gondii virulence and intends to highlight the needs for consistent methods when a panel of T. gondii isolates is evaluated for virulence.

Targeted Transcriptomic Analysis of C57BL/6 and BALB/c Mice During Progressive Chronic Toxoplasma gondii Infection Reveals Changes in Host and Parasite Gene Expression Relating to Neuropathology and Resolution

Toxoplasma gondii is a resilient parasite that infects a multitude of warm-blooded hosts and results in a lifelong chronic infection requiring continuous responses by the host. Chronic infection is characterized by a balanced immune response and neuropathology that are driven by changes in gene expression. Previous research pertaining to these processes has been conducted in various mouse models, and much knowledge of infection-induced gene expression changes has been acquired through the use of high throughput sequencing techniques in different mouse strains and post-mortem human studies. However, lack of infection time course data poses a prominent missing link in the understanding of chronic infection, and there is still much that is unknown regarding changes in genes specifically relating to neuropathology and resulting repair mechanisms as infection progresses throughout the different stages of chronicity. In this paper, we present a targeted approach to gene expression analysis during T. gondii infection through the use of NanoString nCounter gene expression assays. Wild type C57BL/6 and BALB/c background mice were infected, and transcriptional changes in the brain were evaluated at 14, 28, and 56 days post infection. Results demonstrate a dramatic shift in both previously demonstrated and novel gene expression relating to neuropathology and resolution in C57BL/6 mice. In addition, comparison between BALB/c and C57BL/6 mice demonstrate initial differences in gene expression that evolve over the course of infection and indicate decreased neuropathology and enhanced repair in BALB/c mice. In conclusion, these studies provide a targeted approach to gene expression analysis in the brain during infection and provide elaboration on previously identified transcriptional changes and also offer insights into further understanding the complexities of chronic T. gondii infection.

Toxoplasma gondii infection damages the perineuronal nets in a murine model

BACKGROUND

Behavioral and neurochemical alterations associated with toxoplasmosis may be influenced by the persistence of tissue cysts and activation of an immune response in the brain of Toxoplasma gondii-infected hosts. The cerebral extracellular matrix is organised as perineuronal nets (PNNs) that are both released and ensheath by some neurons and glial cells. There is evidences to suggest that PNNs impairment is a pathophysiological mechanism associated with neuropsychiatric conditions. However, there is a lack of information regarding the impact of parasitic infections on the PNNs integrity and how this could affect the host’s behavior.

OBJECTIVES

In this context, we aimed to analyse the impact of T. gondii infection on cyst burden, PNNs integrity, and possible effects in the locomotor activity of chronically infected mice.

METHODS

We infected mice with T. gondii ME-49 strain. After thirty days, we assessed locomotor performance of animals using the open field test, followed by evaluation of cysts burden and PNNs integrity in four brain regions (primary and secondary motor cortices, prefrontal and somesthetic cortex) to assess the PNNs integrity using Wisteria floribunda agglutinin (WFA) labeling by immunohistochemical analyses.

FINDINGS AND MAIN CONCLUSIONS

Our findings revealed a random distribution of cysts in the brain, the disruption of PNNs surrounding neurons in four areas of the cerebral cortex and hyperlocomotor behavior in T. gondii-infected mice. These results can contribute to elucidate the link toxoplasmosis with the establishment of neuroinflammatory response in neuropsychiatric disorders and to raise a discussion about the mechanisms related to changes in brain connectivity, with possible behavioral repercussions during chronic T. gondii infection.

Spontaneous T. gondii neuronal encystment induces structural neuritic network impairment associated with changes of tyrosine hydroxilase expression

Two billion people are chronically infected with Toxoplasma gondii worldwide with unknown consequences. Important neurological diseases have been associated to the brain infection, making essential to understand the neurophysiological changes associated with the neuronal encystment. T. gondii may subvert neuronal functions modifying neurotransmitter concentration in chronically infected mice but the molecular mechanisms involved are still unclear. Parasites were observed inside neuronal cells in cultures from 24-192 hs. The rate of infection increased with time. Neurite density decreased affecting network functionality. Neuronal survival was affected and we detected the presence of cysts inside neuronal bodies and dilated portions of neurites in association with a relative increase of TH-positive neuritic area without noticeable changes in DA immunofluorescence pattern. These results advance our knowledge of the interaction between T. gondii and the neuronal network of the host.

Persistent Toxoplasma Infection of the Brain Induced Neurodegeneration Associated with Activation of Complement and Microglia

Toxoplasma gondii, a common neurotropic parasite, is increasingly being linked to neuropsychiatric disorders, including schizophrenia, Alzheimer's disease, and Parkinson's disease. However, the pathogenic mechanisms underlying these associations are not clear. Toxoplasma can reside in the brain for extensive periods in the form of tissue cysts, and this process requires a continuous immune response to prevent the parasite's reactivation. Because neuroinflammation may promote the onset and progression of neurodegenerative diseases, we investigated neurodegeneration-associated pathological changes in a mouse model of chronic Toxoplasma infection. Under conditions of high-grade chronic infection, we documented the presence of neurodegeneration in specific regions of the prefrontal cortex, namely, the anterior cingulate cortex (ACC) and somatomotor cortex (SC). Neurodegeneration occurred in both glutamatergic and GABAergic neurons. Neurons that showed signs of degeneration expressed high levels of CX3CL1, were marked by profoundly upregulated complement proteins (e.g., C1q and C3), and were surrounded by activated microglia. Our findings suggest that chronic Toxoplasma infection leads to cortical neurodegeneration and results in CX3CL1, complement, and microglial interactions, which are known to mediate the phagocytic clearance of degenerating neurons. Our study provides a mechanistic explanation for the link between Toxoplasma infection and psychiatric disorders.

Prevalence of toxoplasmosis and its association with dementia in older adults in Central Africa: a result from the EPIDEMCA programme

OBJECTIVE

We aimed at estimating the seroprevalence of Toxoplasma gondii (T. gondii) infection in older adults living in Central Africa and investigating its association with dementia using data from the Epidemiology of Dementia in Central Africa (EPIDEMCA) programme.

METHODS

A cross-sectional multicentre population-based study was carried out among participants aged 73 (±7) years on average, living in rural and urban areas of the Central African Republic and the Republic of Congo between November 2011 and December 2012. Blood samples were collected from each consenting participant. The detection of anti-T. gondii immunoglobulin G antibodies was performed in 2014 in France using a commercially available ELISA kit. Participants were interviewed using a standardised questionnaire including sociodemographic characteristics. DSM-IV criteria were required for a diagnosis of dementia. Multivariate binary logistic regression models were used to assess the association between toxoplasmosis infection and dementia.

RESULTS

Among 1662 participants, the seroprevalence of toxoplasmosis was 63.0% (95% confidence interval (CI): 60.7-65.3) overall, 66.6% (95%CI: 63.4-69.8) in Central African Republic and 59.4% (95%CI: 56.1-62.7) in the Republic of Congo. In multivariate analyses, toxoplasmosis status was significantly associated with increasing age (P = 0.006), Republic of Congo (P = 0.002), urban area (P = 0.001) and previous occupation (P = 0.002). No associations between dementia and toxoplasmosis status or anti-T. gondii IgG titres were found.

CONCLUSION

Toxoplasma gondii infection was not associated with dementia among older adults in Central Africa. Our findings are consistent with previous studies and add to the knowledge on the relationship between T. gondii infection and neurological disorders.

Chronic Toxoplasma gondii Infection Induces Anti-N-Methyl-d-Aspartate Receptor Autoantibodies and Associated Behavioral Changes and Neuropathology

Anti-NMDA receptor (NMDAR) autoantibodies have been postulated to play a role in the pathogenesis of NMDAR hypofunction, which contributes to the etiology of psychotic symptoms. Toxoplasma gondii is a pathogen implicated in psychiatric disorders and associated with elevation of NMDAR autoantibodies. However, it remains unclear whether parasite infection is the cause of NMDAR autoantibodies. By using mouse models, we found that NMDAR autoantibody generation had a strong temporal association with tissue cyst formation, as determined by MAG1 antibody seroreactivity (r = 0.96; P < 0.0001), which is a serologic marker for the cyst burden. The presence of MAG1 antibody response, but not T. gondii IgG response, was required for NMDAR autoantibody production. The pathogenic relevance of NMDAR autoantibodies to behavioral abnormalities (blunted response to amphetamine-triggered activity and decreased locomotor activity and exploration) and reduced expression of synaptic proteins (the GLUN2B subtype of NMDAR and PSD-95) has been demonstrated in infected mice. Our study suggests that NMDAR autoantibodies are specifically induced by persistent T. gondii infection and are most likely triggered by tissue cysts. NMDAR autoantibody seroreactivity may be a novel pathological hallmark of chronic toxoplasmosis, which raises questions about NMDAR hypofunction and neurodegeneration in the infected brain.

AAH2 gene is not required for dopamine-dependent neurochemical and behavioral abnormalities produced by Toxoplasma infection in mouse

Infection with the protozoan parasite, Toxoplasma gondii (T. gondii), has been associated with the increased risk for several psychiatric disorders. The exact mechanisms of a hypothesized contribution of T. gondii infection are poorly understood. The T. gondii genome contains two aromatic amino acid hydroxylase genes (AAH1 and AAH2) that encode proteins that can produce L-DOPA. One popular hypothesis posits that these encoded enzymes might influence dopamine (DA) production and hence DA synaptic transmission, leading to neurobehavioral abnormalities in the infected host. Prior studies have shown that deletion of these genes does not alter DA levels in the brain or exploratory activity in infected mice. However, possible effects of AAH gene deficiency on infection-induced brain and behavior alterations that are directly linked to DA synaptic transmission have not been evaluated. We found that chronic T. gondii infection of BALB/c mice leads to blunted response to amphetamine or cocaine and decreased expression of Dopamine Transporter (DAT) and Vesicular Monoamine Transporter 2 (VMAT2). Deletion of AAH2 had no effects on these changes in infected mice. Both wild type and Δaah2 strains produced comparable levels of neuroinflammation. Our findings demonstrate that AAH2 is not required for T. gondii infection-produced DA-dependent neurobehavioral abnormalities.

Schizophrenia and Infections: The Eyes Have It

The visual tract is prominently involved in schizophrenia, as evidenced by perceptual distortions and a type of nystagmus found in many individuals affected. Genetic explanations for these abnormalities have been suggested. This study proposes an alternate explanation based on infection. Several infectious agents thought to be associated with some cases of schizophrenia are known to cause both infection of the fetus and abnormalities of the eye. Toxoplasma gondii is examined in detail, and rubella, cytomegalovirus, varicella-zoster virus, and herpes simplex virus more briefly. Careful ophthalmic assessments, including funduscopy and direct examination of tissues for infectious agents, will clarify the role of such agents in ocular aspects of schizophrenia.

The known and missing links between Toxoplasma gondii and schizophrenia

Toxoplasma gondii, an intracellular protozoan parasite, has a striking predilection for infecting the Central Nervous System and has been linked to an increased incidence of a number of psychiatric diseases. Several in vitro and in vivo studies have shown that T. gondii infection can affect the structure, bioenergetics and function of brain cells, and alters several host cell processes, including dopaminergic, tryptophan-kynurenine, GABAergic, AKT1, Jak/STAT, and vasopressinergic pathways. These mechanisms underlying the neuropathology of latent toxoplasmosis seem to operate also in schizophrenia, supporting the link between the two disorders. Better understanding of the intricate parasite-neuroglial communications holds the key to unlocking the mystery of T. gondii-mediated schizophrenia and offers substantial prospects for the development of disease-modifying therapies.

Shared Immune and Repair Markers During Experimental Toxoplasma Chronic Brain Infection and Schizophrenia

Chronic neurologic infection with Toxoplasma gondii is relatively common in humans and is one of the strongest known risk factors for schizophrenia. Nevertheless, the exact neuropathological mechanisms linking T gondii infection and schizophrenia remain unclear. Here we utilize a mouse model of chronic T gondii infection to identify protein biomarkers that are altered in serum and brain samples at 2 time points during chronic infection. Furthermore, we compare the identified biomarkers to those differing between "postmortem" brain samples from 35 schizophrenia patients and 33 healthy controls. Our findings suggest that T gondii infection causes substantial and widespread immune activation indicative of neural damage and reactive tissue repair in the animal model that partly overlaps with changes observed in the brains of schizophrenia patients. The overlapping changes include increases in C-reactive protein (CRP), interleukin-1 beta (IL-1β), interferon gamma (IFNγ), plasminogen activator inhibitor 1 (PAI-1), tissue inhibitor of metalloproteinases 1 (TIMP-1), and vascular cell adhesion molecule 1 (VCAM-1). Potential roles of these factors in the pathogenesis of schizophrenia and toxoplasmosis are discussed. Identifying a defined set of markers shared within the pathophysiological landscape of these diseases could be a key step towards understanding their specific contributions to pathogenesis.

Strain hypothesis of Toxoplasma gondii infection on the outcome of human diseases

The intracellular protozoan Toxoplasma gondii is an exceptionally successful food and waterborne parasite that infects approximately 1 billion people worldwide. Genotyping of T. gondii isolates from all continents revealed a complex population structure. Recent research supports the notion that T. gondii genotype may be associated with disease severity. Here, we (1) discuss molecular and serological approaches for designation of T. gondii strain type, (2) overview the literatures on the association of T. gondii strain type and the outcome of human disease and (3) explore possible mechanisms underlying these strain-specific pathology and severity of human toxoplasmosis. Although no final conclusions can be drawn, it is clear that virulent strains (e.g. strains containing type I or atypical alleles) are significantly more often associated with increased frequency and severity of human toxoplasmosis. The significance of highly virulent strains can cause severe diseases in immunocompetent patients and might implicated in brain disorders such as schizophrenia should led to reconsideration of toxoplasmosis. Further studies that combine parasite strain typing and human factor analysis (e.g. immune status and genetic background) are required for better understanding of human susceptibility or resistance to toxoplasmosis.

The urban risk and migration risk factors for schizophrenia: are cats the answer?

Being born in and/or raised in an urban area is a proven risk factor for developing schizophrenia. Migrating from countries such as Jamaica or Morocco to countries such as England or the Netherlands is also a proven risk factor for developing schizophrenia. The transmission of Toxoplasma gondii oocysts to children is reviewed and proposed as a partial explanation for both of these risk factors.

MicroRNA-132 dysregulation in Toxoplasma gondii infection has implications for dopamine signaling pathway

Congenital toxoplasmosis and toxoplasmic encephalitis can be associated with severe neuropsychiatric symptoms. However, which host cell processes are regulated and how Toxoplasma gondii affects these changes remain unclear. MicroRNAs (miRNAs) are small noncoding RNA sequences critical to neurodevelopment and adult neuronal processes by coordinating the activity of multiple genes within biological networks. We examined the expression of over 1000 miRNAs in human neuroepithelioma cells in response to infection with Toxoplasma. MiR-132, a cyclic AMP-responsive element binding (CREB)-regulated miRNA, was the only miRNA that was substantially upregulated by all three prototype Toxoplasma strains. The increased expression of miR-132 was also documented in mice following infection with Toxoplasma. To identify cellular pathways regulated by miR-132, we performed target prediction followed by pathway enrichment analysis in the transcriptome of Toxoplasma-infected mice. This led us to identify 20 genes and dopamine receptor signaling was their strongest associated pathway. We then examined myriad aspects of the dopamine pathway in the striatum of Toxoplasma-infected mice 5days after infection. Here we report decreased expression of D1-like dopamine receptors (DRD1, DRD5), metabolizing enzyme (MAOA) and intracellular proteins associated with the transduction of dopamine-mediated signaling (DARPP-32 phosphorylation at Thr34 and Ser97). Increased concentrations of dopamine and its metabolites, serotonin (5-HT) and 5-hydroxyindoleacetic acid were documented by HPLC analysis; however, the metabolism of dopamine was decreased and 5-HT metabolism was unchanged. Our data show that miR-132 is upregulated following infection with Toxoplasma and is associated with changes in dopamine receptor signaling. Our findings provide a possible mechanism for how the parasite contributes to the neuropathology of infection.