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

A Review of Immunological and Neuropsychobehavioral Effects of Latent Toxoplasmosis on Humans

Toxoplasmosis as a zoonotic disease has a worldwide distribution and can infect a wide range of animal hosts, as well as at least one third of the world's human population. The disease is usually mild or asymptomatic in immunocompetent individuals, but dormant tissue cysts survive especially in the brain for the host lifespan, known as latent toxoplasmosis (LT). Recent studies suggest that LT can have certain neurological, immunological psychological and behavioural effects on human including schizophrenia, bipolar disorder, Alzheimer's disease, depression, suicide anxiety and sleeping disorders. LT effects are controversial, and their exact mechanisms of action is not yet fully understood. This review aims to provide an overview of the potential effects, their basic mechanisms including alteration of neurotransmitter levels, immune activation in the central nervous system and induction of oxidative stress. Additionally, beneficial effects of LT, and an explanation of the effects within the framework of manipulation hypothesis, and finally, the challenges and limitations of the current research are discussed.

Toxoplasmosis in Treatment-Resistant Obsessive-Compulsive Disorder Patients

BACKGROUND AND OBJECTIVES

The current study was done to evaluate the relationship between T. gondii and obsessive-compulsive disorder (OCD) as well as prevalence rate of toxoplasmosis in treatment-resistant patients with OCD in comparison with treatment-sensitive patients with OCD.

METHODS

A total of 180 subjects were selected, including 90 patients with OCD and 90 control participants. Immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies against T. gondii were measured by the enzyme-linked immunosorbent assay (ELISA) technique. Detection of acute and chronic toxoplasmosis was carried out using the ELISA IgG avidity. In addition, the presence of this parasite in blood was detected using the nested-polymerase chain reaction (PCR) method.

RESULTS

Regarding T. gondii IgG antibodies 42 (46.7%) and 17 (18.9%) cases were detected in the patients and controls, respectively (P = 0.000). Also, 16 (17.8%) and 5 (5.6%) cases were positive for B1 gene in patients and controls, respectively (P = 0.018). The antibodies were found to be related to risk of OCD [OR (95% CI) = 3.71 (1.88-7.30); P < 0.001]. Moreover, out of 90 patients, 35 and 55 cases were resistant and sensitive to treatment, respectively, so that 24 (68.6%) out of 35 and 18 (32.7%) out of 55 were positive for the antibodies (P = 0.01) as well as 11 (31.4%) out of 35 and 5 (9.1%) out of 55 were positive for B1 gene (P = 0.010). The antibodies were also associated with risk of resistance to treatment in patients with OCD [OR (95% CI) = 3.81 (1.42-10.17); P = 0.008].

CONCLUSION

Our findings showed that toxoplasmosis was more frequent in patients with OCD than the control group. In addition, prevalence rate of toxoplasmosis in treatment-resistant patients with OCD was significantly more than that in treatment-sensitive patients with OCD.

Neurological and Neurobehavioral Disorders Associated with Toxoplasma gondii Infection in Humans

The intracellular parasite Toxoplasma gondii is estimated to infect up to 30% of the world population, leading to lifelong chronic infection of the brain and muscle tissue. Although most latent T. gondii infections in humans have traditionally been considered asymptomatic, studies in rodents suggest phenotypic neurological changes are possible. Consequently, several studies have examined the link between T. gondii infection and diseases such as schizophrenia, epilepsy, depression, bipolar disorder, dysphoria, Alzheimer's disease, Parkinson's disease, and obsessive-compulsive disorder (OCD). To date, there is varying evidence of the relationship of T. gondii to these human neurological or neurobehavioral disorders. A thorough review of T. gondii literature was conducted to highlight and summarize current findings. We found that schizophrenia was most frequently linked to T. gondii infection, while sleep disruption showed no linkage to T. gondii infection, and other conditions having mixed support for a link to T. gondii. However, infection as a cause of human neurobehavioral disease has yet to be firmly established.

Searching for host immune-microbiome mechanisms in obsessive-compulsive disorder: A narrative literature review and future directions

Obsessive-compulsive disorder (OCD) is disabling and often treatment-refractory. Host immunity and gut microbiota have bidirectional communication with each other and with the brain. Perturbations to this axis have been implicated in neuropsychiatric disorders, but immune-microbiome signaling in OCD is relatively underexplored. We review support for further pursuing such investigations in OCD, including: 1) gut microbiota has been associated with OCD, but causal pathogenic mechanisms remain unclear; 2) early environmental risk factors for OCD overlap with critical periods of immune-microbiome development; 3) OCD is associated with increased risk of immune-mediated disorders and changes in immune parameters, which are separately associated with the microbiome; and 4) gut microbiome manipulations in animal models are associated with changes in immunity and some obsessive-compulsive symptoms. Theoretical pathogenic mechanisms could include microbiota programming of cytokine production, promotion of expansion and trafficking of peripheral immune cells to the CNS, and regulation of microglial function. Immune-microbiome signaling in OCD requires further exploration, and may offer novel insights into pathogenic mechanisms and potential treatment targets for this disabling disorder.

Effects of Toxoplasma gondii infection and schizophrenia comorbidity on serum lipid profile: A population retrospective study from Eastern China

INTRODUCTION

Toxoplasma gondii (T. gondii), a parasitic protozoa that is associated with various psychiatric disorders. Both T. gondii infection and disturbed host's lipid profile are common in schizophrenia patients. However, the underlying pathophysiological mechanisms remain speculative. Also, the characteristics of serum lipid levels in schizophrenia patients comorbid with T. gondii infection are not clear. Therefore, it is necessary to explore the influence of chronic T. gondii infection on the characteristic physiological indexes of schizophrenia patients so as to provide some insights into finding target therapeutic drugs.

METHODS

In this study, the effect of chronic T. gondii infection on serum lipid profile was retrospectively analysed in 1719 schizophrenic patients and 1552 healthy subjects from Eastern China.

RESULTS

The overall prevalence of Immunoglobulin G (IgG) antibodies against T. gondii (17.98%) in schizophrenia patients was significantly higher than healthy controls (7.35%, χ2 = 81.831, P = 0.000). Compared to T. gondii IgG-seronegative schizophrenia patients, IgG-seropositive group had higher high-density lipoprotein (HDL) (P = 0.000) and triglycerides (TG) (P = 0.000) levels, while total cholesterol (TC) (P = 0.000) levels showed an opposite tendency in IgG-seropositive cases. We also found significant correlation between T. gondii seropositivity and increased TG (P = 0.000) and TC levels (P = 0.000) in schizophrenia patients. Binary regression analysis also showed that decreased TC level was more common among schizophrenia patients with T. gondii seropositivity compared to seronegative subjects (OR = 0.617, 95%CI = 0.509-0.749, P = 0.000).

CONCLUSION

Patients with chronic T. gondii infection and comorbid schizophrenia had higher HDL and TG levels, while cholesterol levels showed an opposite trend. To the best of our knowledge, this is the first report focus on the host's lipid profile of chronic T. gondii infection and comorbid schizophrenia patients.

Relationship between Toxoplasma gondii seropositivity and depression in children and adolescents

Identification of the structural causes of depression is important for the treatment process, and toxoplasmosis may be related to psychiatric disorders. The aim of this study was to evaluate the relationship between Toxoplasma gondii (T. gondii) seropositivity and depression in children and adolescents. This case-control study included 37 children and adolescents aged 11-18 years diagnosed with depression who were followed by the Manisa Celal Bayar University Child and Adolescent Mental Health Service and 36 children and adolescents aged 11-18 years with no history of depressive episodes or psychiatric disorder treated by the Pediatric Outpatient Department. The T. gondii serology of these two groups was evaluated and compared. There were no statistically significant age or sex differences between the 37 participants with depression and the 36 healthy controls. Eight patients and two controls were seropositive for T. gondii, a statistically significant difference (p = 0.046). Seropositivity was significantly higher in patients with suicidal ideation (p = 0.005) than in those without suicidal ideation. The seropositivity of seven of the nine participants who attempted suicide was significantly higher (p < 0.001) than that of participants who did not. Thus, T. gondii infection may affect the predisposition for and severity of depression.