Latent toxoplasmosis and psychiatric symptoms - A role of tryptophan metabolism?

Seroprevalence and sociodemographic characteristics of Toxoplasma gondii infection in patients with psychiatric disorders in Malaysia

Toxoplasma gondii is a neurotropic protozoan parasite that affects neuronal processing in the brain. This study aimed to investigate the prevalence of T. gondii infection in psychiatric disorder patients. We also investigated the potential association between sociodemographic, clinical manifestation, and behavior of Toxoplasma-seropositive patients with psychiatric disorders. Commercial ELISAs (IgG, IgM, and IgG avidity) using serum and PCR using buffy coat were performed on samples from 54 individuals in each of the following groups: patients diagnosed with depressive disorder, bipolar disorder, and schizophrenia, as well as psychiatrically healthy subjects (control group). They were recruited from the Hospital Universiti Sains Malaysia in Kelantan, Malaysia. Of 54 patients with depressive disorder, 24/54 (44.4 %) were seropositive for IgG, and four (16.7 %) were IgG+/IgM+. Among the latter, a high avidity index indicating a past infection was observed in half of the samples (50.0 %), and the other half (50.0 %) showed a low avidity index, indicating a possible recent infection. Meanwhile, 30/54 (55.6 %) patients with bipolar disorder were seropositive for IgG+, five (16.7 %) were IgG+/IgM+, and four of them had a high avidity index, and one had a low avidity index. Patients with schizophrenia showed 29/54 (53.7 %) seropositive for IgG, two of them (6.9 %) were IgG+/IgM+; one of latter had a high avidity index, and one had a low avidity index. Of 54 people in the control group, 37.0 % (20/54) were seropositive for T. gondii IgG antibodies. However, no significant difference was observed in seroprevalence between the control group and each patient group. No PCR-positive results were documented. A Chi-Square and multiple logistic regression showed that age (p = 0.031), close contact with cats/pets (p = 0.033) and contact with soil (p = 0.012) were significantly associated with Toxoplasma seropositivity in patients with psychiatric disorders. Additional research is needed to elucidate the causal relationships and underlying mechanisms.

Associations between Toxoplasma gondii seropositivity and psychopathological manifestations in schizophrenic patients: A single-center study from Ecuador

BACKGROUND

Schizophrenia, a complex neuropsychiatric disorder, is believed to be influenced by various factors including environmental exposures. A potential environmental factor is the infection by the obligate intracellular parasitic protozoan, Toxoplasma gondii which affects neurotransmitter levels, which could potentially exacerbate, trigger symptoms of schizophrenia or make them worst.

OBJECTIVE

To investigate the association between Toxoplasma gondii seropositivity and psychopathological presentation in persons with schizophrenia in Ecuador.

METHODS

This study was conducted at the Neuroscience Institute of Guayaquil, Ecuador. Among 368 inpatients, 104 were selected based on specific inclusion and exclusion criteria. Descriptive statistics captured patient characteristics and mental health outcomes. Logistic regression models estimated the effect of toxoplasmosis on various mental health outcomes, controlling for demographic and health-related variables.

RESULTS

86.5% of participants were seropositive for toxoplasmosis. Toxoplasma-seropositive schizophrenic patients had a lower risk of depression but a significantly higher risk of disorientation. The most prevalent mental health outcomes were Language Impairments (70.2%) and Bizarre Behavior (76.0%).

CONCLUSION

Our findings suggest that Toxoplasma gondii seropositivity may have specific effects on mental functions in schizophrenic patients, particularly reducing the risk of depression but increasing the risk of disorientation. Further studies are required to clarify these associations and the potential underlying mechanisms.

Chronic infection by atypical Toxoplasma gondii strain induces disturbance in microglia population and altered behaviour in mice

Toxoplasma gondii chronic infection is characterized by the establishment of tissue cysts in the brain and increased levels of IFN-γ, which can lead to brain circuitry interference and consequently abnormal behaviour in mice. In this sense, the study presented here sought to investigate the impact of chronic infection by two T. gondii strains in the brain of infection-resistant mice, as a model for studying the involvement of chronic neuroinflammation with the development of behavioural alterations. For that, male BALB/c mice were divided into three groups: non-infected (Ni), infected with T. gondii ME49 clonal strain (ME49), and infected with TgCkBrRN2 atypical strain (CK2). Mice were monitored for 60 days to establish the chronic infection and then submitted to behavioural assessment. The enzyme-linked immunosorbent assay was used for measurement of specific IgG in the blood and levels of inflammatory cytokines and neurotrophic factors in the brain, and the cell's immunophenotype was determined by multiparametric flow cytometry. Mice infected with ME49 clonal strain displayed hyperlocomotor activity and memory deficit, although no signs of depressive- and/or anxiety-like behaviour were detected; on the other hand, chronic infection with CK2 atypical strain induced anxiety- and depressive-like behaviour. During chronic infection by CK2 atypical strain, mice displayed a higher number of T. gondii brain tissue cysts and inflammatory infiltrate, composed mainly of CD3⁺ T lymphocytes and Ly6C^hi inflammatory monocytes, compared to mice infected with the ME49 clonal strain. Infected mice presented a marked decrease of microglia population compared to non-infected group. Chronic infection with CK2 strain produced elevated levels of IFN-γ and TNF-ɑ in the brain, decreased NGF levels in the prefrontal cortex and striatum, and altered levels of fractalkine (CX3CL1) in the prefrontal cortex and hippocampus. The persistent inflammation and the disturbance in the cerebral homeostasis may contribute to altered behaviour in mice, as the levels of IFN-γ were shown to be correlated with the behavioural parameters assessed here. Considering the high incidence and life-long persistence of T. gondii infection, this approach can be considered a suitable model for studying the impact of chronic infections in the brain and how it impacts in behavioural responses.

Are bipolar disorder, major depression, and suicidality linked with Toxoplasma gondii? A seromolecular case-control study

OBJECTIVE

The existence of predisposing effects of latent Toxoplasma gondii (T. gondii) infection in bipolar disorder (BD), major depression (MD), and even suicide attempt (SA) has long been debatable. This conjecture remains unclear because there is a lack of evidence regarding how T. gondii manipulates the brain and behavior.

METHODS

We investigated the influence of T. gondii infection on BD and MD patients with or without SA compared to age-, sex-, and province-matched healthy controls (HCs) concurrently with serology and molecular-based evaluations. We prospectively assessed 147 volunteers with BD, 161 with MD, and 310 HCs.

RESULTS

T. gondii seropositivity rates were 57.1% for BD, 29.2% for MD, 64.8% for SA, and 21.3% for HC. Binary logistic regression analyses revealed that T. gondii positive Immunoglobulin G (IgG) status may be a prominent tendentious agent for BD (OR = 3.52; 95% CI [2.19-5.80]; p < 0.001) and SA (OR = 17.17; 95% CI [8.12-36.28]; p < 0.001), but not for MD (OR = 1.21; 95% CI [0.74-1.99]; p = 0.45). Nevertheless, the T. gondii DNA ratios determined by polymerase chain reaction (PCR) were linked to BD and MD.

CONCLUSION

Our findings strongly support the burgeoning interest in the possibility that latent T. gondii infection may be relevant to the etiology of BD and SA, although this connection remains ambiguous.

Metabolomics study of cat small intestine during the early stage of Toxoplasma gondii oocyst formation identifies potential biomarkers

Toxoplasma gondii (T. gondii) is a zoonotic intracellular protozoan parasite that can invade, replicate and survive in almost all cells of warm-blooded animals. T. gondii infection threatens the life of the fetus or can cause morbidity in the infant. As the only definitive host of T. gondii, felids spread the pathogen mainly by forming oocysts in the small intestines and discharging the oocysts into the ambient environment, consequently polluting water, vegetables, and meat products. In this study, we used untargeted metabolomics technology to study the changes in metabolites that occurred during the early stage of oocyst formation in the cat small intestine following T. gondii infection and attempted to identify metabolic biomarkers that could potentially be used as diagnostic molecular markers in the future. Domestic cats (Felis catus) were infected with T. gondii Pru tissue cysts, and samples of their small intestinal epithelium were collected at 2 and 4 days post-infection (DPI) for metabolic analysis. LC-MS/MS and multivariate statistical analysis were employed to detect metabolomic signatures that discriminated between the infected and control groups. A total of 1673 ions and 1201 ions were obtained in the positive and negative modes, respectively. Of these ions, 175 were up-regulated and 127 were down-regulated in the positive ion mode; whereas, 123 were up-regulated and 81 were down-regulated in the negative ion mode. Three commonly altered ions (0.74_313.0414 m/z, 8.82_615.2621 m/z and 8.16_325.2362 m/z) were determined to have potential research value. Seventy common metabolic pathways were enriched at two time points, with arginine biosynthesis, pyrimidine metabolism, pantothenate and CoA biosynthesis being the three most significant pathways related to T. gondii. The area under the curve (AUC) of differential metabolites combined with relevant literature analysis showed that N-Methylpelletierine and 3,3-Difluoro-17-methyl-5alpha-androstan-17beta-ol have higher predictability and better potential application value than other metabolites. Our analysis of metabolic markers during the early stage of T. gondii oocyst formation in the small intestine of the definitive host (cat) provided novel insight for understanding oocyst development and a theoretical basis for the application of potential biomarkers.

Comprehensive Overview of Toxoplasma gondii-Induced and Associated Diseases

Toxoplasma gondii (T. gondii) is a prevalent protozoan parasite of medical and veterinary significance. It is the etiologic agent of toxoplasmosis, a neglected disease in which incidence and symptoms differ between patients and regions. In immunocompetent patients, toxoplasmosis manifests as acute and chronic forms. Acute toxoplasmosis presents as mild or asymptomatic disease that evolves, under the host immune response, into a persistent chronic disease in healthy individuals. Chronic toxoplasmosis establishes as latent tissue cysts in the brain and skeletal muscles. In immunocompromised patients, chronic toxoplasmosis may reactivate, leading to a potentially life-threatening condition. Recently, the association between toxoplasmosis and various diseases has been shown. These span primary neuropathies, behavioral and psychiatric disorders, and different types of cancer. Currently, a direct pre-clinical or clinical molecular connotation between toxoplasmosis and most of its associated diseases remains poorly understood. In this review, we provide a comprehensive overview on Toxoplasma-induced and associated diseases with a focus on available knowledge of the molecular players dictating these associations. We will also abridge the existing therapeutic options of toxoplasmosis and highlight the current gaps to explore the implications of toxoplasmosis on its associated diseases to advance treatment modalities.

New role of sertraline against Toxoplasma gondii-induced depression-like behaviours in mice

Toxoplasma gondii (T. gondii) is a neurotropic protozoan parasite, which can cause mental and behavioural disorders. The present study aimed to elucidate the effects and underlying molecular mechanisms of sertraline (SERT) on T. gondii-induced depression-like behaviours. In the present study, a mouse model and a microglial cell line (BV2 cells) model were established by infecting with the T. gondii RH strain. In in vivo and in vitro experiments, the underlying molecular mechanisms of SERT in inhibiting depression-like behaviours and cellular perturbations caused by T. gondii infection were investigated in the mouse brain and BV2 cells. The administration of SERT significantly ameliorated depression-like behaviours in T. gondii-infected mice. Furthermore, SERT inhibited T. gondii proliferation. Treatment with SERT significantly inhibited the activation of microglia and decreased levels of pro-inflammatory cytokines such as tumour necrosis factor-alpha, and interferon-gamma, by down-regulating tumour necrosis factor receptor 1/nuclear factor-kappa B signalling pathway, thereby ameliorating the depression-like behaviours induced by T. gondii infection. Our study provides insight into the underlying molecular mechanisms of the newly discovered role of SERT against T. gondii-induced depression-like behaviours.

Toxoplasma gondii seropositivity in patients with depressive and anxiety disorders

Introduction

Toxoplasma gondii (T. gondii) is an obligate intracellular parasite that is estimated to be carried by one-third of the world population. Latent T. gondii infection has been linked to several neuropsychiatric mood disorders and behaviors. The aim of the present study was to examine whether T. gondii seropositivity is associated with affective disorders, as well as with aggression reactivity and suicidal thoughts.

Methods

In the Netherlands Study of Depression and Anxiety (NESDA), T. gondii antibodies were assessed in patients with current depressive (n ​= ​133), anxiety (n ​= ​188), comorbid depressive and anxiety (n ​= ​148), and remitted disorders (n ​= ​889), as well as in healthy controls (n ​= ​373) based on DSM-IV criteria. Seropositivity was analyzed in relation to disorder status, aggression reactivity and suicidal thoughts using multivariate analyses of covariance and regression analyses.

Results

Participants were on average 51.2 years (SD ​= ​13.2), and 64.4% were female. Seropositivity was found in 673 participants (38.9%). A strong positive association between T. gondii seropositivity and age was observed. No significant associations were found between T. gondii seropositivity and disorder status, aggression reactivity and suicidal thoughts. The adjusted odds ratio (OR) for any remitted disorder versus controls was 1.13 (95% CI: 0.87-1.49), and for any current disorder versus controls was 0.94 (95% CI: 0.69-1.28).

Conclusions

No evidence was found for a relationship between affective disorders and T. gondii infection in the current sample.

Can Toxoplasma gondii Pave the Road for Dementia?

Dementia is an ominous neurological disease. Scientists proposed a link between its occurrence and the presence of Toxoplasma gondii (T. gondii). The long-term sequels of anti-Toxoplasma premunition, chiefly dominated by TNF-α, on the neurons and their receptors as the insulin-like growth factor-1 receptor (IGF-1R), which is tangled in cognition and synaptic plasticity, are still not clear. IGF-1R mediates its action via IGF-1, and its depletion is incorporated in the pathogenesis of dementia. The activated TNF-α signaling pathway induces NF-κβ that may induce or inhibit neurogenesis. This study speculates the potential impact of anti-Toxoplasma immune response on the expression of IGF-1R in chronic cerebral toxoplasmosis. The distributive pattern of T. gondii cysts was studied in association with TNF-α serum levels, the in situ expression of NF-κβ, and IGF-1R in mice using the low virulent ME-49 T. gondii strain. There was an elevation of the TNF-α serum level (p value ≤ 0.004) and significant upsurge in NF-κβ whereas IGF-1R was of low abundance (p value < 0.05) compared to the controls. TNF-α had a strong positive correlation with the intracerebral expression of NF-κβ (r value ≈ 0.943, p value ≈ 0.005) and a strong negative correlation to IGF-1R (r value -0.584 and -0.725 for area% and O.D., respectively). This activated TNF-α/NF-κβ keeps T. gondii under control at the expense of IGF-1R expression, depriving neurons of the effect of IGF-1, the receptor's ligand. We therefore deduce that T. gondii immunopathological reaction may be a road paver for developing dementia.

Infection with Toxoplasma gondii increases the risk of psychiatric disorders in Taiwan: a nationwide population-based cohort study

This study aimed to evaluate associations between toxoplasmosis and psychiatric disorders in Taiwan based on the National Health Insurance Research Database, Taiwan (1997-2013). Patients newly diagnosed with toxoplasmosis formed the case group (n = 259), and the control group included propensity-score matched patients without toxoplasmosis (n = 1036). The primary outcome was incidence of psychiatric disorders. Cox proportional hazards regression and stratified analyses were performed to examine risk of developing specific psychiatric disorders between patients with and without toxoplasmosis. Patients with toxoplasmosis had significantly higher incidence of psychiatric disorders than those without toxoplasmosis (P = 0.016). A significant difference was found in numbers of psychiatric disorders between the two groups during 14 years of follow-up (log-rank P < 0.001). Those with toxoplasmosis had significantly higher risk of bipolar disorder [adjusted hazard ratio (aHR = 3.60, 95% confidence interval (CI) = 2.07, 7.26), depression (aHR = 4.94, 95% CI = 2.15, 11.80) and anxiety (aHR = 5.36, 95% CI = 2.98, 25.88), but no significant between-group differences were found for schizophrenia and other psychiatric disorders. In conclusion, the present nationwide population-based analysis revealed that Toxoplasma gondii infection in Taiwan significantly increases the risk for developing bipolar disorder, depression and anxiety, but not for schizophrenia and other psychiatric disorders.

Catastrophic consequences: can the feline parasite Toxoplasma gondii prompt the purrfect neuroinflammatory storm following traumatic brain injury?

Traumatic brain injury (TBI) is one of the leading causes of morbidity and mortality worldwide; however, treatment development is hindered by the heterogenous nature of TBI presentation and pathophysiology. In particular, the degree of neuroinflammation after TBI varies between individuals and may be modified by other factors such as infection. Toxoplasma gondii, a parasite that infects approximately one-third of the world’s population, has a tropism for brain tissue and can persist as a life-long infection. Importantly, there is notable overlap in the pathophysiology between TBI and T. gondii infection, including neuroinflammation. This paper will review current understandings of the clinical problems, pathophysiological mechanisms, and functional outcomes of TBI and T. gondii, before considering the potential synergy between the two conditions. In particular, the discussion will focus on neuroinflammatory processes such as microglial activation, inflammatory cytokines, and peripheral immune cell recruitment that occur during T. gondii infection and after TBI. We will present the notion that these overlapping pathologies in TBI individuals with a chronic T. gondii infection have the strong potential to exacerbate neuroinflammation and related brain damage, leading to amplified functional deficits. The impact of chronic T. gondii infection on TBI should therefore be investigated in both preclinical and clinical studies as the possible interplay could influence treatment strategies.

Antimalarial Agents as Therapeutic Tools Against Toxoplasmosis-A Short Bridge between Two Distant Illnesses

Toxoplasmosis is an infectious disease with paramount impact worldwide, affecting many vulnerable populations and representing a significant matter of concern. Current therapies used against toxoplasmosis are based essentially on old chemotypes, which fail in providing a definitive cure for the disease, placing the most sensitive populations at risk for irreversible damage in vital organs, culminating in death in the most serious cases. Antimalarial drugs have been shown to possess key features for drug repurposing, finding application in the treatment of other parasite-borne illnesses, including toxoplasmosis. Antimalarials provide the most effective therapeutic solutions against toxoplasmosis and make up for the majority of currently available antitoxoplasmic drugs. Additionally, other antiplasmodial drugs have been scrutinized and many promising candidates have emanated in recent developments. Available data demonstrate that it is worthwhile to explore the activity of classical and most recent antimalarial chemotypes, such as quinolines, endoperoxides, pyrazolo[1,5-a]pyrimidines, and nature-derived peptide-based parasiticidal agents, in the context of toxoplasmosis chemotherapy, in the quest for encountering more effective and safer tools for toxoplasmosis control or eradication.

Monitoring of kynurenine pathway metabolites, neurotransmitters and their metabolites in blood plasma and brain tissue of individuals with latent toxoplasmosis

The aim of the presented work was to develop a highly sensitive, accurate and rapid analytical method for the determination of concentration levels of tryptophan and its metabolites of kynurenine catabolic pathway, as well as neurotransmitters and their metabolites in complex biological matrices (brain tissue and blood plasma). The developed analytical method consists of analytes separation from the biological matrices by protein precipitation (blood plasma) or solvent extraction (brain tissue), derivatization of the analytes and their detection by high-performance liquid chromatography combined with mass spectrometry. Individual steps of the whole process were optimized and the method was validated in the terms of selectivity, linearity (R²≥0.980), precision (RSD ≤ 13.3%), recovery (≥82.0%), limit of detection (1.8 ng/mL of blood plasma, 2.2 pg/mg of brain tissue) and limit of quantification (2.5 ng/mL of blood plasma, 2.8 pg/mg of brain tissue). The method was subsequently verified by an animal study, where the concentration levels of the analytes in biological matrices (blood plasma and brain tissue) of T. gondii - infected rats and control animals were compared. All the data obtained from the animal study were statistically evaluated. Increased concentration levels of kynurenine catabolic pathway metabolites (e.g. kynurenine, 3-hydroxykynurenine, quinolinic acid) were observed in the case of T. gondii - infected rats in contrast to the control group. The opposite effect was determined in the case of serotonin and its metabolite 5-hydroxyindoleacetic acid, where higher concentration levels were found in blood plasma of healthy subjects. Finally, Principal Component Analysis (PCA) was utilized for a score plot formation. PCA score plots have demonstrated the similarities of individuals within each group and the differences among the groups.

Latent toxoplasmosis aggravates anxiety- and depressive-like behaviour and suggest a role of gene-environment interactions in the behavioural response to the parasite

Toxoplasma gondii (TOX) is an intracellular parasite which infects warm-blooded animals including humans. An increasing number of clinical studies now hypothesize that latent toxoplasmosis may be a risk factor for the development of psychiatric disease. For depression, the results have been varied and we speculate that genetic background is important for the response to latent toxoplasmosis. The main objective of this study was to elucidate gene - environment interactions in the behavioural response to TOX infection by use of genetically vulnerable animals (Flinders sensitive line, FSL) compared to control animals (Flinders resistant line, FRL). Our results show that all infected animals displayed increased anxiety-like behaviour whereas only genetically vulnerable animals (FSL rats) showed depressive-like behaviour as a consequence of the TOX infection. Furthermore, peripheral cytokine expression was increased following the infection, primarily independent of strain. In the given study 14 cytokines, chemokines, metabolic hormones, and growth factors were quantified with the bead-based Luminex200 system, however, only IL-1α expression was affected differently in FSL animals compared to FRL rats. These results suggest that latent TOX infection can induce anxiety-like behaviour independent of genetic background. Intriguingly, we also report that for depressive-like behaviour only the vulnerable rat strain is affected. This could explain the discrepancy in the literature as to whether TOX infection is a risk factor for depressive symptomatology. We propose that the low grade inflammation caused by the chronic infection is related to the development of behavioural symptoms.