Toxoplasma gondii-induced neuronal alterations

Toxoplasma gondii seropositivity as a risk factor for epilepsy: A discordant monozygotic twin study

OBJECTIVE

Toxoplasma gondii (T. gondii) seropositivity has been reported to have up to a five-fold increased risk for epilepsy. However, substantial heterogeneity in methodology exists across these studies. Furthermore, other studies failed to replicate an association between T. gondii seropositivity and epilepsy. To address these inconsistencies, we investigated this issue in monozygotic (MZ) twin pairs discordant for epilepsy, a method that controls for age, sex and genetic factors.

METHODS

We analyzed 32 MZ twin pairs who are discordant for epilepsy, comparing rates of T. gondii seropositivity (IgG) between affected and unaffected twins. The odds ratio for T. gondii seropositivity in affected twins compared to their unaffected co-twins was calculated using McNemar's chi-squared paired proportion test. Factors associated with T. gondii seropositivity were assessed using Fisher's exact test and Welch's t-test, as appropriate.

RESULTS

The frequency of seropositivity in affected twins compared to their unaffected co-twins did not differ (odds ratio of 1.67 [95 % CI: 0.39-6.97], p = 0.72), indicating no significant association between T. gondii seropositivity and epilepsy in this cohort. Age at testing was associated with T. gondii seropositivity, with individuals found to be seropositive being older than those who were seronegative [mean age at testing (SD) 59.1 years (12.6) vs 47.7 years (14.3), p = 0.03].

CONCLUSION

In our cohort of MZ twins discordant for epilepsy, we found no evidence for an association between T. gondii seropositivity and epilepsy. Larger carefully controlled studies are warranted.

A pre-existing chronic Toxoplasma gondii infection promotes epileptogenesis and neuropathology in a mouse model of mesial temporal lobe epilepsy

OBJECTIVE

There is initial evidence that the common neurotropic parasite Toxoplasma gondii is a risk factor for the development of epilepsy; however, whether it influences epileptogenesis is unknown. This study investigated whether a pre-existing chronic T. gondii infection alters epileptogenesis and neuropathology in a mouse model of mesial temporal lobe epilepsy.

METHODS

Male and female C57BL/6Jax mice were intraperitoneally administered T. gondii tachyzoites or vehicle control. After 6 weeks, mice underwent self-sustained electrical status epilepticus (SSSE) through an implanted bipolar electrode, or a sham procedure. Continuous video-EEG recordings were taken 0-4- and 12-16-weeks post-SSSE to detect spontaneous seizures. Neuroinflammatory markers were assessed within 1-week post-SSSE, behavior testing was done at 8-12 weeks post-SSSE, and ex vivo MRI was conducted at 16 weeks post-SSSE.

RESULTS

Male T. gondii + SSSE mice had an increased incidence of epilepsy compared to Vehicle + SSSE, while female T. gondii + SSSE mice had worse seizure severity compared to non-infected SSSE mice. There was amplified neuroinflammation in both male and female T. gondii + SSSE mice compared to Vehicle + SSSE mice. T. gondii infection in the absence of SSSE also resulted in epilepsy and neuroinflammation. MRI revealed abnormalities in brain morphology in T. gondii + SSSE male and female mice and changes in white matter integrity in male T. gondii + SSSE mice, compared to both non-infected SSSE and T. gondii control mice. SSSE and T. gondii infection impacted anxiety and spatial memory in males, and anxiety and social behavior in females.

INTERPRETATION

These findings demonstrate that a chronic T. gondii infection can result in epilepsy, and that a pre-existing T. gondii infection exacerbates epileptogenesis following a brain insult, in mice.

Cytoskeletal alterations in neuronal cells implicate Toxoplasma gondii secretory machinery and host microRNA-containing extracellular vesicles

The widespread protozoan Toxoplasma gondii chronically infects neural tissue in vertebrates and is linked to various neurological and neuropsychiatric disorders in humans. However, its effects on sparsely infected neurons and on broader neural circuits remain elusive. Our study reveals that T. gondii infection disrupts cytoskeletal dynamics in SH-SY5Y neuronal cells and primary cortical neurons. Infected neuronal cells undergo significant cytomorphological changes, including retraction of dendritic extensions and alterations in microtubule and F-actin networks, across both parasite genotypes I and II. These cytoskeletal alterations were notably diminished in cells exposed to T. gondii mutants with impaired secretion via the MYR translocon, and were independent of intraneuronal parasite replication. Moreover, a bystander effect was observed, with supernatants from T. gondii-challenged cells inducing similar cytoskeletal changes in uninfected cells. Analyses of extracellular vesicles (EVs) in supernatants revealed differential expression of host microRNAs in response to infection, most notably the upregulation of miR-221-3p, a microRNA not previously associated with T. gondii. The data indicate that unidentified parasite-derived effector(s) secreted via the MYR translocon, in conjunction with MYR-independently induced EV-associated host microRNAs, mediate cytoskeletal alterations in both infected and bystander neuronal cells. The findings provide new insights into molecular mechanisms by which T. gondii infection may disrupt neural networks, shedding light on its potential role in neuronal dysregulation.

Lactoferrin-modified nanoemulsions enhance brain-targeting and therapeutic efficacy of arctigenin against Toxoplasma gondii-induced neuronal injury

Toxoplasma gondii, a neurotropic protozoan parasite, affects the central nervous system and causes various neurological disorders. Previous studies have demonstrated that Arctigenin (AG) exhibits anti-T. gondii activity and reduces depression-like behaviors induced by T. gondii infection. This study aimed to enhance AG's brain-targeting and therapeutic efficacy by developing lactoferrin-modified nanoemulsions loaded with AG (Lf-AG-NEs). Lf-modified nanoemulsions were prepared and assessed using in vivo and in vitro infection models with the T. gondii RH strain, and a co-culture system of BV2 microglia and primary neuron cells. The effects of Lf-AG-NEs on T. gondii-induced neuronal injury were examined, and potential molecular mechanisms were elucidated through real-time quantitative PCR, western blotting, immunofluorescence, flow cytometry, immunohistochemistry, and Nissl staining. In vitro assessments showed significant increases in cellular uptake and blood-brain barrier penetration by Lf-AG-NEs. These nanoemulsions notably inhibited T. gondii proliferation in brain tissue and BV2 cells, surpassing the effects of free AG or AG-NEs alone. Additionally, Lf-AG-NEs substantially alleviated neuropathological changes and reduced microglial activation and neuroinflammation by downregulating the TLR4/NF-κB and TNFR1/NF-κB signaling pathways. Co-culturing BV2 cells with primary cortical neurons indicated that Lf-AG-NEs, similarly to CLI-095 and R7050, attenuated T. gondii-induced microglial activation and subsequent neuronal injury. In conclusion, the successfully prepared Lf-AG-NEs not only enhanced the anti-T. gondii effect but also strengthened the protective impact against neuronal injury induced by T. gondii, through the modulation of microglial signaling pathways.

Pregnant Women Chronically Infected by Toxoplasma gondii with Depressive Disorder: Differential Modulation of Pro-Inflammatory and Anti-Inflammatory Cytokines

Depressive disorder during pregnancy is a common condition, affecting approximately 10-15% of pregnant women, and is associated with adverse pregnancy outcomes such as inadequate prenatal care, substance abuse, and fetal growth restriction. Beyond neurotransmitter disturbances, increasing evidence suggests that infectious agents may play a role in the pathophysiology of depression through immune system modulation. Toxoplasma gondii infection has been linked to various mental disorders in the general population, including depression and anxiety. This study aimed to investigate whether depressive disorder during pregnancy is associated with chronic T. gondii infection by analyzing cytokine levels involved in inflammatory response modulation. Serum levels of TNF, IFN-γ, TGF-β1, IL-6, IL-8, IL-10, and MIF were measured in 79 pregnant women (18-40 years old) during the third trimester of an uncomplicated pregnancy. Participants were divided into four groups: Group I-depressive disorder and T. gondii seropositive (n = 19); Group II-no depressive disorder and T. gondii seropositive (n = 20); Group III-depressive disorder and T. gondii seronegative (n = 20); and Group IV-no depressive disorder and T. gondii seronegative (n = 20). Depressive symptoms were assessed using the Edinburgh Postnatal Depression Scale (EPDS) during routine prenatal visits, and blood samples were collected during standard prenatal examinations. Significant differences in cytokine levels were observed among the study groups. Notably, the group with both depressive disorder and chronic T. gondii infection exhibited a distinct cytokine profile characterized by significantly elevated TNF, IL-6, and IL-10 levels and significantly reduced IL-8 and MIF levels compared to the other groups. These findings suggest that pregnant women with depressive disorder and chronic T. gondii infection exhibit an altered balance of pro- and anti-inflammatory cytokines. This is the first study to investigate the association between serum cytokine levels, depressive disorder, and chronic T. gondii infection in pregnant women. Further research is needed to evaluate the potential of these immunobiomarkers as diagnostic tools or for monitoring therapeutic and prognostic strategies in this context.

Detection of toxoplasma tachyzoites in the cerebrospinal fluid of a COVID-19 positive SLE patient: a case study

The recurrence of latent toxoplasmosis is a frequent cause of toxoplasmic encephalopathy in individuals with immunosuppressive conditions or medication. If left untreated or diagnosed is delayed, it often resulting in fatality. The pathogen of Toxoplasma gondii has been identified in cerebrospinal fluid cytology and a limited number of documented cases of cerebral toxoplasmosis, typically observed in those with acquired immunodeficiency syndrome (AIDS). We report the identification of Toxoplasma gondii tachyzoites in the cerebrospinal fluid of a patient diagnosed with systemic lupus erythematosus (SLE) and concurrent SARS-CoV-2 positive infection. The presented case suggests that cerebral toxoplasmosis should be promptly considered when patients with systemic lupus erythematosus exhibit neurological manifestations.

Toxoplasma gondii, suicidal behaviour and suicide risk factors in US Veterans enrolled in mental health treatment

Markers of chronic infection Toxoplasma gondii (Nicolle et Manceaux, 1908) have been associated with suicidal self-directed violence (SSDV). We present the results of the first study relating T. gondii IgG serology with suicide attempts and suicidal ideation in United States Veterans, known to have higher suicide rates than members of the general population. We also related T. gondii serology to SSDV risk factors, including valid and reliable measures of trait impulsivity, aggression, self-reported depression, and sleep disturbance. We recruited 407 Veterans enrolled at three Veterans Affairs Medical Centers with mean (S.D.) age = 45.6 (11.6) years; 304 men (74.7%); 203 with a history of SSDV and 204 with no history of any self-directed violence (SDV). Seropositivity and serointensity, categorised as high (top quartile) or low (lower three quartiles), were analysed in relationship to SSDV, suicidal ideation and clinical risk factors using age and gender-adjusted linear and logistic methods, after transformations and nonparametric tests when appropriate. Associations between seropositivity and SSDV and its risk factors were not significant in all groups. High serointensity, while not associated with SSDV or repeat suicide attempts, was positively associated with suicidal ideation, depression, impulsivity, and daytime dysfunction due to sleepiness (p < 0.05), but only in Veterans with a history of SSDV. In Veterans without a history of SDV, no associations were significant. These associations remained significant after adjustment for certain socioeconomic factors (i.e., income, homelessness, military rank). Including education in the model downgraded the statistical significance of suicidal ideation and depression to statistical trends, but the significance of associations with impulsivity and daytime dysfunction due to sleepiness remained. Major limitations include the cross-sectional design, overall low seropositivity within the sample, and potentially spurious results due to multiple comparisons. Thus, the results of this report need to be replicated in larger samples, ideally longitudinally.

Association Between Toxoplasma gondii Infection and Serum Neurotransmitter Levels in Major Depressive Disorder Patients: A Case-Control Study in Bangladesh

Toxoplasma gondii (T. gondii) is an obligate, intracellular, neurotropic protozoan parasite. After primary infection, T. gondii parasite undergoes stage conversion from fast-replicating tachyzoites to slow-replicating dormant bradyzoites, particularly in the brain, and persists for a lifetime of an individual. In this study, the impact of T. gondii infection in individuals with psychological disorder, that is, major depressive disorder (MDD) has been studied. Ninety-five MDD (n = 95) patients were enrolled with age and sex-matched healthy controls (HCs, n = 90). The seroprevalence of T. gondii infection among these individuals was determined using the TOXO IgM/IgG Rapid Test Cassette that determines the anti-T. gondii IgM and IgG antibodies in the serum samples. Furthermore, to understand the impact of T. gondii in developing major depression, the serum level of neurotransmitters (i.e., dopamine, adrenaline, and noradrenaline) was determined using an enzyme-linked immunosorbent assay (ELISA). Our data suggest that anti-T. gondii IgG was slightly higher in MDD patients than in HCs. The level of dopamine was significantly lower in T. gondii-infected MDD patients than in HCs. However, adrenaline and noradrenaline levels showed increasing levels in T. gondii-infected MDD patients. The level of neurotransmitters was correlated with the DSM-D scores of MDD patients. These data, nevertheless, confirm that T. gondii might affect the level of neurotransmitters in MDD patients. However, whether the reduced level of dopamine and increased level of adrenaline and noradrenaline act as contributing factors for the development of MDD is yet to be known.

Agency

Agency is action aimed at goals selected by an agent. A deterministic world view leaves scant room for agency. To reconcile the arguments, we represent action as nested control systems, ranging from clearly deterministic to clearly volitional. Negative feedback minimizes deviations from setpoints (goals). Goals are determined by higher modules in a hierarchy of systems, ranging from gamma-efferent spindles through reflexes to operant responses; these last, and the larger system that contains them, called the Self, comprise volitional agents. When operants become habitual they descend to closed teleonomic systems-automaticity. Change in emotional states, and unpredicted changes in the context-raise them back to full volitional systems. At the highest level is the Self-the brain's model of the agent. When aroused out of open teleonomic functioning, it must reconsider means and ends. It does so by simulating action plans, using the same neural systems it uses to effect them. The simulated stimuli and responses are conscious, approximating their perceptions as experienced in real time; this verisimilitude gives them their hedonic value. Positive feedback plays a key role in these complex adaptive systems, as it focuses and holds attention on the most salient percepts and goals, permitting the self-organization of action plans. The Self is not a separate entity, but a colloquy of command modules wearing the avatar of the agent. This system is put into correspondence with Grossberg's Adaptive Resonance Theory. Free will and determinism emerge not as binary opposites, but the modulating inputs to a spectrum of systems.

Diseases Caused by and Behaviors Associated with Toxoplasma gondii Infection

Toxoplasma gondii is an Apicomplexan parasite that is estimated to infect at least one-third of the global human population. T. gondii infection may be transmitted horizontally or vertically. The main risk factors for transmission to humans are related to diet, especially the consumption of undercooked meat, along with soil contact. In immunocompetent persons, the acute infection may go undetected as it typically produces minor, non-specific symptoms that are self-limited. After infection is established, recurrent retinochoroiditis is the most common clinical disease. In contrast, severe systemic or cerebral toxoplasmosis may be life-threatening for immunocompromised individuals. Furthermore, congenital toxoplasmosis acquired in utero may have devastating consequences if not recognized and promptly treated. A growing body of research has identified associations between latent T. gondii infection, and personality traits and risk-taking behaviors. Other studies have documented associations between latent infection and psychiatric conditions that include schizophrenia and bipolar affective disorder. With no current treatment regimens being curative of T. gondii infection, effective prevention measures at both the public health and individual levels are vitally important.

Toxoplasma gondii Infection of BALB/c Mice Perturbs Host Neurochemistry

Toxoplasma gondii infection has been associated with psychoneurological disease in humans and behavioural changes in rodents. However, the mechanisms accounting for this have not been fully described and in some cases could be argued to reflect the severe neuropathology that some mice suffer during infection. Herein we employ a multi-omics approach to extensively examine BALB/c mice that are resistant to toxoplasmic encephalitis. Using a combination of LCMS (liquid chromatography-mass spectrometry) and RNAseq we demonstrate that infection alters the neurochemistry and the transcriptome of the brains of BALB/c mice. Notable changes to tryptophan, purine, arginine, nicotinamide and carnitine metabolism were observed in infected mice and this was accompanied with changes to the levels of a number of transcripts associated with enzymes these metabolic pathways. In addition, changes were seen in transcripts of many immunologically important genes known to contribute to immunity to T. gondii. Changes in the levels of additional transcripts during infection have previously been associated with psychoneurological diseases. The results demonstrate that the BALB/c mouse, with its relatively mild neurological disease, is a useful model for characterising the effects of T. gondii infection on murine neurochemistry. The results also implicate specific biochemical pathways in mediating these changes and should inform further mechanistic studies and suggest therapeutic targets.

Complement-dependent loss of inhibitory synapses on pyramidal neurons following Toxoplasma gondii infection

The apicomplexan parasite Toxoplasma gondii has developed mechanisms to establish a central nervous system infection in virtually all warm-blooded animals. Acute T. gondii infection can cause neuroinflammation, encephalitis, and seizures. Meanwhile, studies in humans, nonhuman primates, and rodents have linked chronic T. gondii infection with altered behavior and increased risk for neuropsychiatric disorders, including schizophrenia. These observations and associations raise questions about how this parasitic infection may alter neural circuits. We previously demonstrated that T. gondii infection triggers the loss of inhibitory perisomatic synapses, a type of synapse whose dysfunction or loss has been linked to neurological and neuropsychiatric disorders. We showed that phagocytic cells (including microglia and infiltrating monocytes) contribute to the loss of these inhibitory synapses. Here, we show that these phagocytic cells specifically ensheath excitatory pyramidal neurons, leading to the preferential loss of perisomatic synapses on these neurons and not those on cortical interneurons. Moreover, we show that infection induces an increased expression of the complement C3 gene, including by populations of these excitatory neurons. Infecting C3-deficient mice with T. gondii revealed that C3 is required for the loss of perisomatic inhibitory synapses. Interestingly, loss of C1q did not prevent the loss of perisomatic synapses following infection. Together, these findings provide evidence that T. gondii induces changes in excitatory pyramidal neurons that trigger the selective removal of inhibitory perisomatic synapses and provide a role for a nonclassical complement pathway in the remodeling of inhibitory circuits in the infected brain.

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.

Alterations in gut microbiota contribute to cognitive deficits induced by chronic infection of Toxoplasma gondii

Chronic infection with Toxoplasma gondii (T. gondii) emerges as a risk factor for neurodegenerative diseases in animals and humans. However, the underlying mechanisms are largely unknown. We aimed to investigate whether gut microbiota and its metabolites play a role in T. gondii-induced cognitive deficits. We found that T. gondii infection induced cognitive deficits in mice, which was characterized by synaptic ultrastructure impairment and neuroinflammation in the hippocampus. Moreover, the infection led to gut microbiota dysbiosis, barrier integrity impairment, and inflammation in the colon. Interestingly, broad-spectrum antibiotic ablation of gut microbiota attenuated the adverse effects of the parasitic infection on the cognitive function in mice; cognitive deficits and hippocampal pathological changes were transferred from the infected mice to control mice by fecal microbiota transplantation. In addition, the abundance of butyrate-producing bacteria and the production of serum butyrate were decreased in infected mice. Interestingly, dietary supplementation of butyrate ameliorated T. gondii-induced cognitive impairment in mice. Notably, compared to the healthy controls, decreased butyrate production was observed in the serum of human subjects with high levels of anti-T. gondii IgG. Overall, this study demonstrates that gut microbiota is a key regulator of T. gondii-induced cognitive impairment.

A comprehensive assessment of toxoplasmosis and its dormant impact on psychotic disorders (Review)

Toxoplasmosis is a pathological condition induced by the parasite, Toxoplasma gondii (T. gondii), which has a notable affinity for the cellular components of the central nervous system. Over the decades, the relationship between toxoplasmosis and the development of psychiatric disorders has generated profound interest within the scientific community. Whether considering immunocompetent or immunocompromised patients, epidemiological studies suggest that exposure to T. gondii may be associated with a higher risk of certain psychiatric disorders. However, there are extensive debates regarding the exact nature of this association and how T. gondii is involved in the pathogenesis of these disorders. Toxoplasmosis has long been considered an asymptomatic infection among immunocompetent patients. However, there appears to be an association between chronic brain infection with T. gondii and alterations in patient neuronal architecture, neurochemistry and behavior. The present review aimed to compile statements and pathophysiological hypotheses regarding the potential association between toxoplasmosis and psychotic disorders. Further research is necessary for understanding the potential relationship of T. gondii infection and psychotic disorders.

Allosteric strand displacement isothermal amplification for the visual detection of Toxoplasma gondii in 30 minutes

Early detection of Toxoplasma gondii (T. gondii) is critical due to a lack of effective treatment for toxoplasmosis.This study established a simple, cost-effective, and rapid colorimetric detection method for T. gondii. The entire testing process, from sample collection to results, takes only 0.5 h. These characteristics fulfill the demands of researchers seeking rapid target detection with minimal equipment reliance. For genomic extraction, this study evaluated the ability of two filter papers to capture genomes. A rapid genomic extraction device combined with the two filter papers was designed to simplify the genomic extraction process, which was completed within 10 min and increased the detection sensitivity tenfold. The method utilized a simplified primer design for isothermal amplification, namely allosteric strand displacement (ASD), and employed an underutilized commercial color indicator, Bromothymol Blue (BTB), for signal output. Compared with other reported indicators, BTB exhibited a more pronounced color change, shifting from blue to yellow in positive samples, facilitating easier visual differentiation. The reaction was completed in 20 min with a limit of detection (LOD) as low as 0.014 T. gondii per microliter.

Impact of latent toxoplasmosis on pneumonic and non-pneumonic COVID-19 patients with estimation of relevant oxidative stress biomarkers

Susceptibility to COVID-19, the most devastating global pandemic, appears to vary widely across different population groups. Exposure to toxoplasmosis has been proposed as a theory to explain the diversity of these populations. The aim of the present study was to investigate the possible association between latent toxoplasmosis and COVID-19 and its probable correlation with markers of oxidative stress, C-reactive protein (CRP) and ferritin. In a case-control study, blood samples were collected from 91 confirmed (48 non-pneumonic; NP, and 43 pneumonic; P) COVID-19 patients and 45 healthy controls. All participants were tested for IgG anti-Toxoplasma gondii antibodies and oxidative stress markers (nitric oxide [NO], superoxide dismutase [SOD] and reduced glutathione [GSH]), and CRP and serum ferritin levels were determined. In COVID-19 patients, IgG anti-T. gondii antibodies were found in 54% compared to 7% in the control group, with the difference being statistically significant (P ˂ 0.001). However, no significant correlation was found between the severity of COVID-19 and latent T. gondii infection. Latent toxoplasmosis had a strong influence on the risk of COVID-19. NO and SOD levels were significantly increased in COVID-19 patients, while GSH levels decreased significantly in them compared to control subjects (P ˂ 0.001 for both values). CRP and ferritin levels were also significantly elevated in P COVID-19 patients infected with toxoplasmosis. This is the first study to look at the importance of oxidative stress indicators in co-infection between COVID-19 and T. gondii. The high prevalence of latent toxoplasmosis in COVID-19 suggests that T. gondii infection can be considered a strong indicator of the high risk of COVID-19.

Ameliorative effects of propolis and wheat germ oil on acute toxoplasmosis in experimentally infected mice are associated with reduction in parasite burden and restoration of histopathological changes in the brain, uterus, and kidney

Toxoplasmosis continues to be a prevalent parasitic zoonosis with a global distribution. This disease is caused by an intracellular parasite known as Toxoplasma gondii, and the development of effective novel drug targets to combat it is imperative. There is limited information available on the potential advantages of wheat germ oil (WGO) and propolis, both individually and in combination, against the acute phase of toxoplasmosis. In this study, acute toxoplasmosis was induced in Swiss albino mice, followed by the treatment of infected animals with WGO and propolis, either separately or in combination. After 10 days of experimental infection and treatment, mice from all groups were sacrificed, and their brains, uteri, and kidneys were excised for histopathological assessment. Additionally, the average parasite load in the brain was determined through parasitological assessment, and quantification of the parasite was performed using Real-Time Polymerase Chain Reaction targeting gene amplification. Remarkably, the study found that treating infected animals with wheat germ oil and propolis significantly reduced the parasite load compared to the control group that was infected but not treated. Moreover, the group treated with a combination of wheat germ oil and propolis exhibited a markedly greater reduction in parasitic load compared to the other groups. Similarly, the combination treatment effectively restored the histopathological changes observed in the brain, uterus, and kidney, and the scoring of these reported lesions confirmed these findings. In summary, the present results reveal intriguing insights into the potential therapeutic benefits of wheat germ oil and propolis in the treatment of acute toxoplasmosis.

Toxoplasma-host endoplasmic reticulum interaction: How T. gondii activates unfolded protein response and modulates immune response

Toxoplasma gondii is a neurotropic single-celled zoonotic parasite that can infect human beings and animals. Infection with T. gondii is usually asymptomatic in immune-competent individual, however, it can cause symptomatic and life-threatening conditions in immunocompromised individuals and in developing foetuses. Although the mechanisms that allow T. gondii to persist in host cells are poorly understood, studies in animal models have greatly improved our understanding of Toxoplasma-host cell interaction and how this interaction modulates parasite proliferation and development, host immune response and virulence of the parasite. T. gondii is capable of recruiting the host endoplasmic reticulum (ER), suggesting it may influence the host ER function. Herein, we provide an overview of T. gondii infection and the role of host ER during stressed conditions. Furthermore, we highlight studies that explore T. gondii's interaction with the host ER. We delve into how this interaction activates the unfolded protein response (UPR) and ER stress-mediated apoptosis. Additionally, we examine how T. gondii exploits these pathways to its advantage.

Zinc Oxide and Magnesium-Doped Zinc Oxide Nanoparticles Ameliorate Murine Chronic Toxoplasmosis

Toxoplasma gondii causes a global parasitic disease. Therapeutic options for eradicating toxoplasmosis are limited. In this study, ZnO and Mg-doped ZnO NPs were prepared, and their structural and morphological chrematistics were investigated. The XRD pattern revealed that Mg-doped ZnO NPs have weak crystallinity and a small crystallite size. FTIR and XPS analyses confirmed the integration of Mg ions into the ZnO framework, producing the high-purity Mg-doped ZnO nanocomposite. TEM micrographs determined the particle size of un-doped ZnO in the range of 29 nm, reduced to 23 nm with Mg2+ replacements. ZnO and Mg-doped ZnO NPs significantly decreased the number of brain cysts (p < 0.05) by 29.30% and 35.08%, respectively, compared to the infected untreated group. The administration of ZnO and Mg-doped ZnO NPs revealed a marked histopathological improvement in the brain, liver, and spleen. Furthermore, ZnO and Mg-doped ZnO NPs reduced P53 expression in the cerebral tissue while inducing CD31 expression, which indicated a protective effect against the infection-induced apoptosis and the restoration of balance between free radicals and antioxidant defense activity. In conclusion, the study proved these nanoparticles have antiparasitic, antiapoptotic, and angiogenetic effects. Being nontoxic compounds, these nanoparticles could be promising adjuvants in treating chronic toxoplasmosis.

Phytohormones regulate asexual Toxoplasma gondii replication

The protozoan Toxoplasma gondii (T. gondii) is a zoonotic disease agent causing systemic infection in warm-blooded intermediate hosts including humans. During the acute infection, the parasite infects host cells and multiplies intracellularly in the asexual tachyzoite stage. In this stage of the life cycle, invasion, multiplication, and egress are the most critical events in parasite replication. T. gondii features diverse cell organelles to support these processes, including the apicoplast, an endosymbiont-derived vestigial plastid originating from an alga ancestor. Previous studies have highlighted that phytohormones can modify the calcium-mediated secretion, e.g., of adhesins involved in parasite movement and cell invasion processes. The present study aimed to elucidate the influence of different plant hormones on the replication of asexual tachyzoites in a human foreskin fibroblast (HFF) host cell culture. T. gondii replication was measured by the determination of T. gondii DNA copies via qPCR. Three selected phytohormones, namely abscisic acid (ABA), gibberellic acid (GIBB), and kinetin (KIN) as representatives of different plant hormone groups were tested. Moreover, the influence of typical cell culture media components on the phytohormone effects was assessed. Our results indicate that ABA is able to induce a significant increase of T. gondii DNA copies in a typical supplemented cell culture medium when applied in concentrations of 20 ng/μl or 2 ng/μl, respectively. In contrast, depending on the culture medium composition, GIBB may potentially serve as T. gondii growth inhibitor and may be further investigated as a potential treatment for toxoplasmosis.

Reduced neural progenitor cell count and cortical neurogenesis in guinea pigs congenitally infected with Toxoplasma gondii

Toxoplasma (T.) gondii is an obligate intracellular parasite with a worldwide distribution. Congenital infection can lead to severe pathological alterations in the brain. To examine the effects of toxoplasmosis in the fetal brain, pregnant guinea pigs are infected with T. gondii oocysts on gestation day 23 and dissected 10, 17 and 25 days afterwards. We show the neocortex to represent a target region of T. gondii and the parasite to infect neural progenitor cells (NPCs), neurons and astrocytes in the fetal brain. Importantly, we observe a significant reduction in neuron number at end-neurogenesis and find a marked reduction in NPC count, indicating that impaired neurogenesis underlies the neuronal decrease in infected fetuses. Moreover, we observe focal microglioses to be associated with T. gondii in the fetal brain. Our findings expand the understanding of the pathophysiology of congenital toxoplasmosis, especially contributing to the development of cortical malformations.

Pathogen-Mediated Alterations of Insect Chemical Communication: From Pheromones to Behavior

Pathogens can influence the physiology and behavior of both animal and plant hosts in a manner that promotes their own transmission and dispersal. Recent research focusing on insects has revealed that these manipulations can extend to the production of pheromones, which are pivotal in chemical communication. This review provides an overview of the current state of research and available data concerning the impacts of bacterial, viral, fungal, and eukaryotic pathogens on chemical communication across different insect orders. While our understanding of the influence of pathogenic bacteria on host chemical profiles is still limited, viral infections have been shown to induce behavioral changes in the host, such as altered pheromone production, olfaction, and locomotion. Entomopathogenic fungi affect host chemical communication by manipulating cuticular hydrocarbons and pheromone production, while various eukaryotic parasites have been observed to influence insect behavior by affecting the production of pheromones and other chemical cues. The effects induced by these infections are explored in the context of the evolutionary advantages they confer to the pathogen. The molecular mechanisms governing the observed pathogen-mediated behavioral changes, as well as the dynamic and mutually influential relationships between the pathogen and its host, are still poorly understood. A deeper comprehension of these mechanisms will prove invaluable in identifying novel targets in the perspective of practical applications aimed at controlling detrimental insect species.

Influences of Microbial Symbionts on Chemoreception of Their Insect Hosts

Chemical communication is widespread among insects and exploited to adjust their behavior, such as food and habitat seeking and preferences, recruitment, defense, and mate attraction. Recently, many studies have revealed that microbial symbionts could regulate host chemical communication by affecting the synthesis and perception of insect semiochemicals. In this paper, we review recent studies of the influence of microbial symbionts on insect chemoreception. Microbial symbionts may influence insect sensitivity to semiochemicals by regulating the synthesis of odorant-binding proteins or chemosensory proteins and olfactory or gustatory receptors and regulating host neurotransmission, thereby adjusting insect behavior. The manipulation of insect chemosensory behavior by microbial symbionts is conducive to their proliferation and dispersal and provides the impetus for insects to change their feeding habits and aggregation and dispersal behavior, which contributes to population differentiation in insects. Future research is necessary to reveal the material and information exchange between both partners to improve our comprehension of the evolution of chemoreception in insects. Manipulating insect chemoreception physiology by inoculating them with microbes could be utilized as a potential approach to managing insect populations.

The effect of chronic experimental toxoplasmosis on some brain neurotransmitters level and behavior changes

Toxoplasma is capable of causing long-lasting brain cysts in its hosts, which can lead to physiological disturbances in brain neurotransmitters and result in changes in the host's behavior. This study aimed to investigate these changes using an experimental model. Twenty-five female Wistar rats, weighing 220-220 g and six weeks old, were selected for the study. The rats were divided into two control and experimental groups. The experimental group was injected with 5 × 105 tachyzoites of Toxoplasma gondii (virulent RH strain) intra-peritoneally. Four months after the injection, the rats were subjected to behavioral tests, including learning, memory, depression, and locomotor activity tests. The rats were then euthanized, and their brain and serum samples were analyzed for dopamine and serotonin levels. To ensure the presence of cysts in the brain tissue, a PCR test and preparation of pathological slides from the brain tissue were performed. The results showed that the amount of dopamine in the brain of the infected group was significantly higher than that of the control group, while the level of serotonin in brain of the infected group was significantly lower than that of the control group (P < 0.05). However, no significant difference was observed in the amount of these neurotransmitters in the blood of the two groups (P > 0.05). Behavioral changes were evaluated, and it was found that the learning and memory levels of the infected rats were significantly lower than those of the control group (P < 0.05), but no difference was observed in locomotor activity between the two groups (P > 0.05). This experimental infection model indicated that changes in neurotransmitter levels lead to behavior changes. CONCLUSION: The presence of parasite cysts in the brain can affect some of the host's behaviors through changes in neurotransmitter levels. Therefore, there is a possibility that there is a relationship between the presence of Toxoplasma cysts in the brain and neurological disorders. The results of this study suggest that chronic toxoplasmosis may play a role in behavior changes in psychotic diseases.

Studies on the mechanism of Toxoplasma gondii Chinese 1 genotype Wh6 strain causing mice abnormal cognitive behavior

BACKGROUND

Alzheimer's disease presents an abnormal cognitive behavior. TgCtwh6 is one of the predominant T. gondii strains prevalent in China. Although T. gondii type II strain infection can cause host cognitive behavioral abnormalities, we do not know whether TgCtwh6 could also cause host cognitive behavioral changes. So, in this study, we will focus on the effect of TgCtwh6 on mouse cognitive behavior and try in vivo and in vitro to explore the underlying mechanism by which TgCtwh6 give rise to mice cognitive behavior changes at the cellular and molecular level.

METHODS

C57BL/6 mice were infected orally with TgCtwh6 cysts. From day 90 post-infection on, all mice were conducted through the open field test and then Morris water maze test to evaluate cognitive behavior. The morphology and number of cells in hippocampus were examined with hematoxylin-eosin (H&E) and Nissl staining; moreover, Aβ protein in hippocampus was determined with immunohistochemistry and thioflavin S plaque staining. Synaptotagmin 1, apoptosis-related proteins, BACE1 and APP proteins and genes from hippocampus were assessed by western blotting or qRT-PCR. Hippocampal neuronal cell line or mouse microglial cell line was challenged with TgCtwh6 tachyzoites and then separately cultured in a well or co-cultured in a transwell device. The target proteins and genes were analyzed by immunofluorescence staining, western blotting and qRT-PCR. In addition, mouse microglial cell line polarization state and hippocampal neuronal cell line apoptosis were estimated using flow cytometry assay.

RESULTS

The OFT and MWMT indicated that infected mice had cognitive behavioral impairments. The hippocampal tissue assay showed abnormal neuron morphology and a decreased number in infected mice. Moreover, pro-apoptotic proteins, as well as BACE1, APP and Aβ proteins, increased in the infected mouse hippocampus. The experiments in vitro showed that pro-apoptotic proteins and p-NF-κBp65, NF-κBp65, BACE1, APP and Aβ proteins or genes were significantly increased in the infected HT22. In addition, CD80, pro-inflammatory factors, notch, hes1 proteins and genes were enhanced in the infected BV2. Interestingly, not only the APP and pro-apoptotic proteins in HT22, but also the apoptosis rate of HT22 increased after the infected BV2 were co-cultured with the HT22 in a transwell device.

CONCLUSIONS

Neuron apoptosis, Aβ deposition and neuroinflammatory response involved with microglia polarization are the molecular and cellular mechanisms by which TgCtwh6 causes mouse cognitive behavioral abnormalities.

Curcumin modulates neurogliogenesis and purinergic receptor expression in neural precursor cells infected with Toxoplasma gondii

Toxoplasma gondii is an obligate intracellular parasite that causes toxoplasmosis, and its congenital transmission is of paramount concern. During embryonic development, infection with the parasite causes irreversible damage to the still-forming fetus's central nervous system (CNS). In the pathogenesis of neurotoxoplasmosis, purinergic receptors prejudice neuroprotection, neuroinflammation, and activation of microbicide mechanisms against the parasitic vacuole. This study used curcumin as a treatment for neural precursor cells (NPCs) infected with T. gondii. The congenital toxoplasmosis induction consisted of maternal infection with the VEG strain, and NPCs were obtained from the telencephalon of mouse embryos. Curcumin at increasing concentrations was administered in vitro to analyze NPC metabolic activity, cell number, and size, as well as neurogliogenesis, proving to be effective in recovering the size of infected NPCs. Curcumin partially re-established impaired neurogenesis. Purinergic A1, A2A, and P2X7 receptors may be related to neuroprotection, neuroinflammatory control, and activation of mechanisms for inducing the parasite's death. ERK 1/2 was highly expressed in infected cells, while its expression rates decreased after the addition of the treatment, highlighting the possible anti-inflammatory action of curcumin. These findings suggest that curcumin treats neurological perturbations induced by toxoplasmosis.

Effects of diverse Types of Toxoplasma gondii on the outcome of Alzheimer's disease in the rat model

Toxoplasma gondii has lifelong persistence in the brain and its cysts can affect gene expression and change diverse biological functions of neurons. Many studies indicated T. gondii infection as a risk factor for the development of behavioral changes and neurodegenerative diseases such as Alzheimer's disease (AD), although the etiopathogenetic link between them has not been exactly elucidated. The current study aimed to examine the effects of chronic toxoplasmosis infection with Types I, II, and III strains (RH, PRU, and VEG) alone and in combination on cognitive impairments and neuronal death in the Aβ1-42-induced rat model of Alzheimer's disease. In the chronic toxoplasmosis phase, Alzheimer's induction was conducted by injecting Aβ1-42 oligomers into the rat brain hippocampus. Behavioral tests were conducted 10 days after the AD induction. Real-time PCR was performed to evaluate T. gondii parasite burden by amplification of the B1 gene. Cytokines IL-1β, TNF-α, and IL-10 were assayed in brain tissue supernatant using ELISA. Also, histopathological examinations were conducted to calculate inflammatory changes and neuronal death in the brain. Our findings showed that chronic toxoplasmosis infection with PRU reduces cognitive disorders, while the RH strain of T. gondii plays a destructive role and aggravates cognitive impairments in AD. Also, infection with a combination of PRU and VEG strains significantly improved spatial learning and memory impairments in Alzheimer's rat model. Histopathological findings also confirmed the results of behavioral tests, so that in AβPRU and AβPRU + VEG groups, neuronal death and infiltration of inflammatory cells were negligible and significantly less than in Alzheimer's and AβRH groups. Our findings indicate that chronic toxoplasmosis infection with PRU strain alone, also in combination with VEG strain can significantly improve cognitive disorders in AD rats, while RH strain plays a destructive role in AD pathogenesis.

Chronic Toxoplasma gondii infection contributes to perineuronal nets impairment in the primary somatosensory cortex

Toxoplasma gondii is able to manipulate the host immune system to establish a persistent and efficient infection, contributing to the development of brain abnormalities with behavioral repercussions. In this context, this work aimed to evaluate the effects of T. gondii infection on the systemic inflammatory response and structure of the primary somatosensory cortex (PSC). C57BL/6 and BALB/c mice were infected with T. gondii ME49 strain tissue cysts and accompanied for 30 days. After this period, levels of cytokines IFN-γ, IL-12, TNF-α and TGF-β were measured. After blood collection, mice were perfused and the brains were submitted to immunohistochemistry for perineuronal net (PNN) evaluation and cyst quantification. The results showed that C57BL/6 mice presented higher levels of TNF-α and IL-12, while the levels of TGF-β were similar between the two mouse lineages, associated with the elevated number of tissue cysts, with a higher occurrence of cysts in the posterior area of the PSC when compared to BALB/c mice, which presented a more homogeneous cyst distribution. Immunohistochemistry analysis revealed a greater loss of PNN labeling in C57BL/6 animals compared to BALB/c. These data raised a discussion about the ability of T. gondii to stimulate a systemic inflammatory response capable of indirectly interfering in the brain structure and function.

Protection Induced by Vaccination with Recombinant Baculovirus and Virus-like Particles Expressing Toxoplasma gondii Rhoptry Protein 18

Heterologous immunization is garnering attention as a promising strategy to improve vaccine efficacy. Vaccines based on recombinant baculovirus (rBV) and virus-like particle (VLP) are safe for use, but heterologous immunization studies incorporating these two vaccine platforms remain unreported to date. Oral immunization is the simplest, most convenient, and safest means for mass immunization. In the present study, mice were immunized with the Toxoplasma gondii rhoptry protein 18 (ROP18)-expressing rBVs (rBVs-ROP18) and VLPs (VLPs-ROP18) via oral, intranasal, and intramuscular (IM) routes to evaluate the protection elicited against the intracellular parasite T. gondii ME49 strain. Overall, boost immunization with VLPs-ROP18 induced a significant increase in T. gondii-specific antibody response in all three immunization routes. Parasite-specific mucosal and cerebral antibody responses were observed from all immunization groups, but the highest mucosal IgA response was detected from the intestines of orally immunized mice. Antibody-secreting cell (ASC), CD8⁺ T cell, and germinal center B cell responses were strikingly similar across all three immunization groups. Oral immunization significantly reduced pro-inflammatory cytokine IL-6 in the brains as well as that by IN and IM. Importantly, all of the immunized mice survived against lethal challenge infections where body weight loss was negligible from all three immunizations. These results demonstrated that protection induced against T. gondii by oral rBV-VLP immunization regimen is just as effective as IN or IM immunizations.

Comparative study of oxidative stress and antioxidative markers in patients infected with Toxoplasma gondii

Recently, oxidative stress and antioxidative compounds have been described as potential biomarkers. However, there is no consensus on the most appropriate oxidative and antioxidative biomarkers for patients with Toxoplasma gondii. In the present study, we evaluated the levels of lipid, protein, DNA oxidative damage and antioxidants in samples from patients infected with T. gondii with and without ocular toxoplasmosis. The levels of MDA, TBARS, micronuclei, carbonyl, GSH, vitamin C and vitamin E were measured on samples from 8 patients positive for T. gondii antibodies with ocular toxoplasmosis (OT), 20 patients positive for T. gondii antibodies without ocular toxoplasmosis (non OT), and 12 healthy individuals negative for T. gondii antibodies. The levels of MDA, TBARS, carbonyl and micronuclei were significantly higher in non OT patients, while MDA and TBARS levels were lower in OT patients. In contrast, the antioxidative factors, GSH and vitamin E levels were significantly lower in non OT patients, while vitamin C was lower in non OT and OT patients. Additionally, non OT patients were indicated to be high producers of oxidative markers (TBARS, MDA, micronuclei and carbonyl), while control group was indicated to be high producer of antioxidative markers (GSH, vitamins C and E). However, OT patients were not found as high producers of oxidative nor antioxidative markers. Our results provide a starting point of possible markers to better understand the disease pathogenesis in patients infected with T. gondii. Additional studies are needed to clarify the potential contribution of oxidative and antioxidative markers in these patients population.

Toxoplasma gondii dense granule protein 3 promotes endoplasmic reticulum stress-induced apoptosis by activating the PERK pathway

Background

Toxoplasma gondii is a neurotropic single-celled parasite that can infect mammals, including humans. Central nervous system infection with T. gondii infection can lead to Toxoplasma encephalitis. Toxoplasma infection can cause endoplasmic reticulum (ER) stress and unfolded protein response (UPR) activation, which ultimately can lead to apoptosis of host cells. The dense granule protein GRA3 has been identified as one of the secretory proteins that contribute to the virulence of T. gondii; however, the mechanism remains enigmatic.

Methods

The expression of the GRA3 gene in RH, ME49, Wh3, and Wh6 strains was determined using quantitative real-time polymerase chain reaction (qRT–PCR). pEGFP-GRA3_Wh6 was constructed by inserting Chinese 1 Wh6 GRA3 (GRA3_Wh6) cDNA into a plasmid encoding the enhanced GFP. Mouse neuro2a (N2a) cells were transfected with either pEGFP or pEGFP-GRA3_Wh6 (GRA3_Wh6) and incubated for 24–36 h. N2a cell apoptosis and ER stress-associated proteins were determined using flow cytometry and immunoblotting. Furthermore, N2a cells were pretreated with GSK2656157 (a PERK inhibitor) and Z-ATAD-FMK (a caspase-12 inhibitor) before GRA3_Wh6 transfection, and the effect of the inhibitors on GRA3_Wh6-induced ER stress and apoptosis were investigated.

Results

GRA3 gene expression was higher in the less virulent strains of type II ME49 and type Chinese 1 Wh6 strains compared with the virulent strains of type I RH strain and type Chinese 1 Wh3 strain. Transfection with GRA3_Wh6 plasmid induced neuronal apoptosis and increased the expression of GRP78, p-PERK, cleaved caspase-12, cleaved caspase-3, and CHOP compared with the control vector. Pretreatment with GSK2656157 and Z-ATAD-FMK decreased apoptosis in N2a cells, and similarly, ER stress- and apoptosis-associated protein levels were significantly decreased.

Conclusion

GRA3 induces neural cell apoptosis via the ER stress signaling pathway, which could play a role in toxoplasmic encephalitis.

Graphical Abstract

Persisting Microbiota and Neuronal Imbalance Following T. gondii Infection Reliant on the Infection Route

Toxoplasma gondii is a highly successful parasite capable of infecting all warm-blooded animals. The natural way of infection in intermediate hosts is the oral ingestion of parasite-contaminated water or food. In murine experimental models, oral infection (p.o.) of mice with T. gondii is applied to investigate mucosal and peripheral immune cell dynamics, whereas intraperitoneal infection (i.p.) is frequently used to study peripheral inflammation as well as immune cell – neuronal interaction in the central nervous system (CNS). However, the two infection routes have not yet been systematically compared along the course of infection. Here, C57BL/6 mice were infected p.o. or i.p. with a low dose of T. gondii cysts, and the acute and chronic stages of infection were compared. A more severe course of infection was detected following i.p. challenge, characterized by an increased weight loss and marked expression of proinflammatory cytokines particularly in the CNS during the chronic stage. The elevated proinflammatory cytokine expression in the ileum was more prominent after p.o. challenge that continued following the acute phase in both i.p. or p.o. infected mice. This resulted in sustained microbial dysbiosis, especially after p.o. challenge, highlighted by increased abundance of pathobionts from the phyla proteobacteria and a reduction of beneficial commensal species. Further, we revealed that in the CNS of i.p. infected mice CD4 and CD8 T cells displayed higher IFNγ production in the chronic stage. This corresponded with an increased expression of C1q and CD68 in the CNS and reduced expression of genes involved in neuronal signal transmission. Neuroinflammation-associated synaptic alterations, especially PSD-95, VGLUT, and EAAT2 expression, were more pronounced in the cortex upon i.p. infection highlighting the profound interplay between peripheral inflammation and CNS homeostasis.

Toxoplasma gondii infection and insomnia: A case control seroprevalence study

We determined the association between Toxoplasma gondii (T. gondii) infection and insomnia. Through an age-and gender-matched case-control study, 577 people with insomnia (cases) and 577 people without insomnia (controls) were tested for anti-T. gondii IgG and IgM antibodies using commercially available enzyme-immunoassays. Anti-T. gondii IgG antibodies were found in 71 (12.3%) of 577 individuals with insomnia and in 46 (8.0%) of 577 controls (OR = 1.62; 95% CI: 1.09–2.39; P = 0.01). Men with insomnia had a higher (16/73: 21.9%) seroprevalence of T. gondii infection than men without insomnia (5/73: 6.8%) (OR: 3.81; 95% CI: 1.31–11.06; P = 0.009). The rate of high (>150 IU/ml) anti-T. gondii IgG antibody levels in cases was higher than the one in controls (OR = 2.21; 95% CI: 1.13–4.31; P = 0.01). Men with insomnia had a higher (8/73: 11.0%) rate of high anti-T. gondii IgG antibody levels than men without insomnia (0/73: 0.0%) (P = 0.006). The rate of high anti-T. gondii IgG antibody levels in cases >50 years old (11/180: 6.1%) was higher than that (3/180: 1.7%) in controls of the same age group (OR: 3.84; 95% CI: 1.05–14.00; P = 0.05). No difference in the rate of IgM seropositivity between cases and controls was found (OR = 1.33; 95% CI: 0.57–3.11; P = 0.50). Results of this seroepidemiology study suggest that infection with T. gondii is associated with insomnia. Men older than 50 years with T. gondii exposure might be prone to insomnia. Further research to confirm the association between seropositivity and serointensity to T. gondii and insomnia is needed.

Tamoxifen Increased Parasite Burden and Induced a Series of Histopathological and Immunohistochemical Changes During Chronic Toxoplasmosis in Experimentally Infected Mice

The global distribution of breast cancer and the opportunistic nature of the parasite have resulted in many patients with breast cancer becoming infected with toxoplasmosis. However, very limited information is available about the potential effects of tamoxifen on chronic toxoplasmosis and its contribution to the reactivation of the latent infection. The present study investigated the potential effects of tamoxifen on chronic toxoplasmosis in animal models (Swiss albino mice). Following induction of chronic toxoplasmosis and treatment with the drug for 14 and 28 days, the anti-parasitic effects of tamoxifen were evaluated by parasitological assessment and counting of Toxoplasma cysts. In addition, the effects of the drug on the parasite load were evaluated and quantitated using TaqMan real-time quantitative PCR followed by investigation of the major histopathological changes and immunohistochemical findings. Interestingly, tamoxifen increased the parasite burden on animals treated with the drug during 14 and 28 days as compared with the control group. The quantification of the DNA concentrations of Toxoplasma P29 gene after the treatment with the drug revealed a higher parasite load in both treated groups vs. control groups. Furthermore, treatment with tamoxifen induced a series of histopathological and immunohistochemical changes in the kidney, liver, brain, and uterus, revealing the exacerbating effect of tamoxifen against chronic toxoplasmosis. These changes were represented by the presence of multiple T. gondii tissue cysts in the lumen of proximal convoluted tubules associated with complete necrosis in their lining epithelium of the kidney section. Meanwhile, liver tissue revealed multiple T. gondii tissue cysts in hepatic parenchyma which altered the structure of hepatocytes. Moreover, clusters of intracellular tachyzoites were observed in the lining epithelium of endometrium associated with severe endometrial necrosis and appeared as diffuse nuclear pyknosis combined with sever mononuclear cellular infiltration. Brain tissues experienced the presence of hemorrhages in pia mater and multiple T. gondii tissue cysts in brain tissue. The severity of the lesions was maximized by increasing the duration of treatment. Collectively, the study concluded novel findings in relation to the potential role of tamoxifen during chronic toxoplasmosis. These findings are very important for combating the disease, particularly in immunocompromised patients which could be life-threatening.

Toxoplasma Reduces Complications of Parkinson’s Disease: An Experimental Study in BALB/c Mice

Background

Parkinson's disease (PD) has been described in dopamine brain level reductions. Conversely, several studies have shown that Toxoplasma parasite can increase the level of dopamine in an infected host. This study was conducted to assess the serum, cerebral dopamine levels, and downregulation of Parkinson's disease manifestations in mice with chronic toxoplasmosis.

Methods

PD induction was done by oral inoculation of rotenone into BALB/c mice. To induce the chronic infection, cysts of T. gondii Prugniaud strain (genotype II) were injected intraperitoneally into the mice. The rotarod test was used for the evaluation of functional motor disorders in experimental mice. The serum and cerebral dopamine levels of the mice were also measured by using high-performance liquid chromatography (HPLC) on consecutive periods (10 days).

Results

Findings of the rotarod test showed the highest and lowest average of running duration belonged to the uninfected mice and PD mice, respectively. Remarkably, the running duration of infected mice with PD was higher than PD mice. As well, the level of serum and cerebral dopamine increased in mice with PD and toxoplasmosis in comparison with PD mice.

Conclusion

Increasing the serum and cerebral dopamine levels in mice infected with toxoplasmosis is related to the presence of the parasite. Moreover, the dopamine upregulation due to the infection is effective in the reduction of PD complications.

Toxoplasma gondii infection induces cell apoptosis via multiple pathways revealed by transcriptome analysis

Toxoplasma gondii is a worldwide parasite that can infect almost all kinds of mammals and cause fatal toxoplasmosis in immunocompromised patients. Apoptosis is one of the principal strategies of host cells to clear pathogens and maintain organismal homeostasis, but the mechanism of cell apoptosis induced by T. gondii remains obscure. To explore the apoptosis influenced by T. gondii, Vero cells infected or uninfected with the parasite were subjected to apoptosis detection and subsequent dual RNA sequencing (RNA-seq). Using high-throughput Illumina sequencing and bioinformatics analysis, we found that pro-apoptosis genes such as DNA damage-inducible transcript 3 (DDIT3), growth arrest and DNA damage-inducible α (GADD45A), caspase-3 (CASP3), and high-temperature requirement protease A2 (HtrA2) were upregulated, and anti-apoptosis genes such as poly(adenosine diphosphate (ADP)-ribose) polymerase family member 3 (PARP3), B-cell lymphoma 2 (Bcl-2), and baculoviral inhibitor of apoptosis protein (IAP) repeat containing 5 (BIRC5) were downregulated. Besides, tumor necrosis factor (TNF) receptor-associated factor 1 (TRAF1), TRAF2, TNF receptor superfamily member 10b (TNFRSF10b), disabled homolog 2 (DAB2)‍-interacting protein (DAB2IP), and inositol 1,4,5-trisphosphate receptor type 3 (ITPR3) were enriched in the upstream of TNF, TNF-related apoptosis-inducing ligand (TRAIL), and endoplasmic reticulum (ER) stress pathways, and TRAIL-receptor 2 (TRAIL-R2) was regarded as an important membrane receptor influenced by T. gondii that had not been previously considered. In conclusion, the T. gondii RH strain could promote and mediate apoptosis through multiple pathways mentioned above in Vero cells. Our findings improve the understanding of the T. gondii infection process through providing new insights into the related cellular apoptosis mechanisms.

Latent Toxoplasmosis is Associated with Depression and Suicidal Behavior

OBJECTIVE

Neuroinflammation is implicated in the pathophysiology of depression. Toxoplasma gondii (T. gondii) causes chronic brain inflammatory process and may thus contribute to both depression and its most serious complication, suicidal behavior. In this study, we hypothesized that latent toxoplasmosis may underlie current depression and/or suicidal behavior.

METHOD

Currently depressed individuals (N = 384) and age, sex, and residence-matched healthy controls (HC) (N = 400) were tested for latent toxoplasmosis (i.e., positive serum T. gondii IgG antibodies). Exclusions included positive IgM and negative IgG antibodies indicating acute T. gondii infection and history of cognitive problems. Depression severity and history of lifetime suicide attempts were assessed using Beck Depression Inventory (BDI) and Columbia Suicide Severity Rating Scale, respectively.

RESULTS

Participants with seropositive anti-T. gondii IgG antibody had a significantly higher odds of being depressed compared with seronegative participants (OR = 2.9, 95% CI: 1.9-4.3; p < 0.001). BDI score was significantly different between depressed seropositive and depressed seronegative individuals (IgG＋: mean (SD)= 39.65 (11.83) vs. IgG-: mean (SD)= 33.44(9.80); t = 5.03, p < 0.001). Further, seropositive depressed participants were more likely to have prior history of actual suicide attempts compared with seronegative participants (OR= 6.2, 95% CI: 3.4-11.2, p < 0.001).

CONCLUSIONS

Latent toxoplasmosis may represent be a risk factor for depression and suicidal behavior. Screening for, and treatment of, underlying T. gondii infection may help improve depression and curb the increasing suicide rates. Future studies should prospectively test these hypotheses to be adequately implemented.HIGHLIGHTSLatent toxoplasmosis has been linked to history of psychiatric disorders.Depressed individuals have higher positivity rate of T. gondii IgG antibody than healthy controls.Depressed T. gondii seropositive individuals have increased likelihood to have history of suicidal behavior.

Exploring the Antiparasitic Activity of Tris-1,3,4-Thiadiazoles against Toxoplasma gondii-Infected Mice

Nitrogen-containing atoms in their core structures have been exclusive building blocks in drug discovery and development. One of the most significant and well-known heterocycles is the 1,3,4-thidiazole nucleus, which is found in a wide range of natural products and therapeutic agents. In the present work, certain tris-1,3,4-thiadiazole derivatives (6, 7) were synthesized through a multi-step synthesis approach. All synthesized compounds were characterized using different spectroscopic tools. Previously, thiadiazole compounds as anti-Toxoplasma gondii agents have been conducted and reported in vitro. However, this is the first study to test the anti-Toxoplasma gondii activity of manufactured molecular hybrids thiadiazole in an infected mouse model with the acute RH strain of T. gondii. All the observed results demonstrated compound (7)’s powerful activity, with a considerable reduction in the parasite count reaching 82.6% in brain tissues, followed by liver and spleen tissues (65.35 and 64.81%, respectively). Inflammatory and anti-inflammatory cytokines assessments proved that Compound 7 possesses potent antiparasitic effect. Furthermore, docking tests against TgCDPK1 and ROP18 kinase (two major enzymes involved in parasite invasion and egression) demonstrated compound 7’s higher potency compared to compound 6 and megazol. According to the mentioned results, tris-1,3,4-thiadiazole derivatives under test can be employed as potent antiparasitic agents against the acute RH strain of T. gondii.

Remarkable histopathological improvement of experimental toxoplasmosis after receiving spiramycin-chitosan nanoparticles formulation

The present study investigated the anti-Toxoplasma effect of chitosan nanoparticles [CS NPs], spiramycin, spiramycin co-administered with metronidazole and spiramycin-CS NPs formulation on the parasite burden and histopathological changes in the liver, spleen and brain in experimentally infected mice. Seventy male Swiss albino mice were classified into seven equal groups: healthy control (I), infected untreated control (II), infected group receiving CS NPs (III), spiramycin administered infected group (IV), infected group receiving spiramycin-metronidazole (V), infected receiving 400 mg/kg spiramycin-CS NPs (VI) and infected treated with spiramycin-loaded CS NPs 100 mg/kg (VII). All groups were inoculated intraperitoneally with 2500 T. gondii tachyzoites RH strain except the healthy control group. All groups were sacrificed on the 8th day after infection. Density of the parasite and histopathological examination of the liver, spleen and brain of all treated mice revealed reduction in the mean tachyzoites count as well as decreased inflammation, congestion and necrosis within tissue sections. Spiramycin-loaded NPs displayed the highest significant reduction in the pathological insult tailed by spiramycin-metronidazole and CS NPs. In conclusion, spiramycin-loaded CS NPs showed a promising synergistic combination in the treatment of the histopathology caused by toxoplasmosis.

Immune response and pathogen invasion at the choroid plexus in the onset of cerebral toxoplasmosis

BACKGROUND

Toxoplasma gondii (T. gondii) is a highly successful parasite being able to cross all biological barriers of the body, finally reaching the central nervous system (CNS). Previous studies have highlighted the critical involvement of the blood-brain barrier (BBB) during T. gondii invasion and development of subsequent neuroinflammation. Still, the potential contribution of the choroid plexus (CP), the main structure forming the blood-cerebrospinal fluid (CSF) barrier (BCSFB) have not been addressed.

METHODS

To investigate T. gondii invasion at the onset of neuroinflammation, the CP and brain microvessels (BMV) were isolated and analyzed for parasite burden. Additionally, immuno-stained brain sections and three-dimensional whole mount preparations were evaluated for parasite localization and morphological alterations. Activation of choroidal and brain endothelial cells were characterized by flow cytometry. To evaluate the impact of early immune responses on CP and BMV, expression levels of inflammatory mediators, tight junctions (TJ) and matrix metalloproteinases (MMPs) were quantified. Additionally, FITC-dextran was applied to determine infection-related changes in BCSFB permeability. Finally, the response of primary CP epithelial cells to T. gondii parasites was tested in vitro.

RESULTS

Here we revealed that endothelial cells in the CP are initially infected by T. gondii, and become activated prior to BBB endothelial cells indicated by MHCII upregulation. Additionally, CP elicited early local immune response with upregulation of IFN-γ, TNF, IL-6, host-defence factors as well as swift expression of CXCL9 chemokine, when compared to the BMV. Consequently, we uncovered distinct TJ disturbances of claudins, associated with upregulation of MMP-8 and MMP-13 expression in infected CP in vivo, which was confirmed by in vitro infection of primary CP epithelial cells. Notably, we detected early barrier damage and functional loss by increased BCSFB permeability to FITC-dextran in vivo, which was extended over the infection course.

CONCLUSIONS

Altogether, our data reveal a close interaction between T. gondii infection at the CP and the impairment of the BCSFB function indicating that infection-related neuroinflammation is initiated in the CP.

Toxoplasmosis: Targeting neurotransmitter systems in psychiatric disorders

The most common form of the disease caused by Toxoplasma gondii (T. gondii) is latent toxoplasmosis due to the formation of tissue cysts in various organs, such as the brain. Latent toxoplasmosis is probably a risk factor in the development of some neuropsychiatric disorders. Behavioral changes after infection are caused by the host immune response, manipulation by the parasite, central nervous system (CNS) inflammation, as well as changes in hormonal and neuromodulator relationships. The present review focused on the exact mechanisms of T. gondii effect on the alteration of behavior and neurotransmitter levels, their catabolites and metabolites, as well as the interaction between immune responses and this parasite in the etiopathogenesis of psychiatric disorders. The dysfunction of neurotransmitters in the neural transmission is associated with several neuropsychiatric disorders. However, further intensive studies are required to determine the effect of this parasite on altering the level of neurotransmitters and the role of neurotransmitters in the etiology of host behavioral changes.

Is Toxoplasma gondii Infection Associated with Sexual Promiscuity? A Cross-Sectional Study

We determined the association between T. gondii seropositivity and a history of sexual promiscuity. The study included 3933 people (mean age: 41.81 ± 14.31 years) who attended public health facilities. Face-to-face interviews were used to collect data. Enzyme immunoassays were used to determine anti-T. gondii IgG and IgM antibodies. Anti-T. gondii IgG antibodies were found in 57 (18.1%) of 315 individuals with sexual promiscuity and in 374 (10.3%) of 3618 individuals without this practice (OR: 1.91; 95% CI: 1.41–2.60; p < 0.0001). High (>150 IU/mL) levels of anti-T. gondii IgG antibodies were found in 29 (9.2%) of the 315 participants with sexual promiscuity and in 167 (4.6%) of the 3618 participants without this history (OR: 2.09; 95% CI: 1.38–3.16; p = 0.0003). The association of sexual promiscuity with T. gondii seropositivity and serointensity was observed in men but not in women. Sexual promiscuity was associated with T. gondii seropositivity in all age groups studied (≤30 years, 31–50 years, and >50 years) and with T. gondii serointensity in two age groups (≤30 years, and >50 years). No difference in the frequencies of anti-T. gondii IgM antibodies among the groups was found. Our findings indicate that T. gondii seropositivity and serointensity are associated with sexual promiscuity.

Effect of 17β-Estradiol, Progesterone, and Tamoxifen on Neurons Infected with Toxoplasma gondii In Vitro

Toxoplasma gondii (T. gondii) is the causal agent of toxoplasmosis, which produces damage in the central nervous system (CNS). Toxoplasma-CNS interaction is critical for the development of disease symptoms. T. gondii can form cysts in the CNS; however, neurons are more resistant to this infection than astrocytes. The probable mechanism for neuron resistance is a permanent state of neurons in the interface, avoiding the replication of intracellular parasites. Steroids regulate the formation of Toxoplasma cysts in mice brains. 17β-estradiol and progesterone also participate in the control of Toxoplasma infection in glial cells in vitro. The aim of this study was to evaluate the effects of 17β-estradiol, progesterone, and their specific agonists-antagonists on Toxoplasma infection in neurons in vitro. Neurons cultured were pretreated for 48 h with 17β-estradiol or progesterone at 10, 20, 40, 80, or 160 nM/mL or tamoxifen 1 μM/mL plus 17β-estradiol at 10, 20, 40, 80, and 160 nM/mL. In other conditions, the neurons were pretreated during 48 h with 4,4',4″-(4-propyl-[1H] pyrozole-1,3,5-triyl) trisphenol or 23-bis(4-hydroxyphenyl) propionitrile at 1 nM/mL, and mifepristone 1 µM/mL plus progesterone at 10, 20, 40, 80, and 160 nM/mL. Neurons were infected with 5000 tachyzoites of the T. gondii strain RH. The effect of 17β estradiol, progesterone, their agonists, or antagonists on Toxoplasma infection in neurons was evaluated at 24 and 48 h by immunocytochemistry. T. gondii replication was measured with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction assay. 17β-Estradiol alone or plus tamoxifen reduced infected neurons (50%) compared to the control at 48 h. Progesterone plus estradiol decreased the number of intracellular parasites at 48 h of treatment compared to the control (p < 0.001). 4,4',4″-(4-propyl-[1H] pyrozole-1,3,5-triyl) trisphenol and 23-bis(4-hydroxyphenyl) propionitrile reduced infected neurons at 48 h of treatment significantly compared to the control (p < 0.05 and p < 0.001, respectively). The Toxoplasma infection process was decreased by the effect of 17β-estradiol alone or combined with tamoxifen or progesterone in neurons in vitro. These results suggest the essential participation of progesterone and estradiol and their classical receptors in the regulation of T. gondii neuron infection.

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.

Association of Toxoplasma gondii Seropositivity With Cognitive Function in Healthy People: A Systematic Review and Meta-analysis

IMPORTANCE

The parasite Toxoplasma gondii has been associated with behavioral alterations and psychiatric disorders. Studies investigating neurocognition in people with T gondii infection have reported varying results. To systematically analyze these findings, a meta-analysis evaluating cognitive function in healthy people with and without T gondii seropositivity is needed.

OBJECTIVE

To assess whether and to what extent T gondii seropositivity is associated with cognitive function in otherwise healthy people.

DATA SOURCES

A systematic search was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline. A systematic search of PubMed, MEDLINE, Web of Science, PsycInfo, and Embase was performed to identify studies from database inception to June 7, 2019, that analyzed cognitive function among healthy participants with available data on T gondii seropositivity. Search terms included toxoplasmosis, neurotoxoplasmosis, Toxoplasma gondii, cognition disorder, neuropsychological, and psychomotor performance.

STUDY SELECTION

Studies that performed cognitive assessment and analyzed T gondii seroprevalence among otherwise healthy participants were included.

DATA EXTRACTION AND SYNTHESIS

Two researchers independently extracted data from published articles; if needed, authors were contacted to provide additional data. Quantitative syntheses were performed in predefined cognitive domains when 4 independent data sets per domain were available. Study quality, heterogeneity, and publication bias were assessed.

MAIN OUTCOMES AND MEASURES

Performance on neuropsychological tests measuring cognitive function.

RESULTS

The systematic search yielded 1954 records. After removal of 533 duplicates, an additional 1363 records were excluded based on a review of titles and abstracts. A total of 58 full-text articles were assessed for eligibility (including reference list screening); 45 articles were excluded because they lacked important data or did not meet study inclusion or reference list criteria. The remaining 13 studies comprising 13 289 healthy participants (mean [SD] age, 46.7 [16.0] years; 6586 men [49.6%]) with and without T gondii seropositivity were included in the meta-analysis. Participants without T gondii seropositivity had favorable functioning in 4 cognitive domains: processing speed (standardized mean difference [SMD], 0.12; 95% CI, 0.05-0.19; P = .001), working memory (SMD, 0.16; 95% CI, 0.06-0.26; P = .002), short-term verbal memory (SMD, 0.18; 95% CI, 0.09-0.27; P < .001), and executive functioning (SMD, 0.15; 95% CI, 0.01-0.28; P = .03). A meta-regression analysis found a significant association between older age and executive functioning (Q = 6.17; P = .01). Little suggestion of publication bias was detected.

CONCLUSIONS AND RELEVANCE

The study's findings suggested that T gondii seropositivity was associated with mild cognitive impairment in several cognitive domains. Although effect sizes were small, given the ubiquitous prevalence of this infection globally, the association with cognitive impairment could imply a considerable adverse effect at the population level. Further research is warranted to investigate the underlying mechanisms of this association.

Galectins - Important players of the immune response to CNS parasitic infection

Galectins are a family of proteins that bind β-galactosides and play key roles in a variety of cellular processes including host defense and entry of parasites into the host cells. They have been well studied in hosts but less so in parasites. As both host and parasite galectins are highly upregulated proteins following infection, galectins are an area of increasing interest and their role in immune modulation has only recently become clear. Correlation of CNS parasitic diseases with mental disorders as a result of direct or indirect interaction has been observed. Therefore, galectins produced by the parasite should be taken into consideration as potential therapeutic agents.

Mucosal Administration of Recombinant Baculovirus Displaying Toxoplasma gondii ROP4 Confers Protection Against T. gondii Challenge Infection in Mice

Pathogens require physical contact with the mucosal surface of the host organism to initiate infection and as such, vaccines eliciting both mucosal and systemic immune responses would be promising. Studies involving the use of recombinant baculoviruses (rBVs) as mucosal vaccines are severely lacking despite their inherently safe nature, especially against pathogens of global importance such as Toxoplasma gondii. Here, we generated rBVs displaying T. gondii rhoptry protein 4 (ROP4) and evaluated their protective efficacy in BALB/c mice following immunization via intranasal (IN) and oral routes. IN immunization with the ROP4-expressing rBVs elicited higher levels of parasite-specific IgA antibody responses compared to oral immunization. Upon challenge infection with a lethal dose of T. gondii ME49, IN immunization elicited significantly higher parasite-specific antibody responses in the mucosal tissues such as intestines, feces, vaginal samples, and brain than oral immunization. Marked increases in IgG and IgA antibody-secreting cell (ASC) responses were observed from intranasally immunized mice. IN immunization elicited significantly enhanced induction of CD4+, CD8+ T cells, and germinal center B (GC B) cell responses from secondary lymphoid organs while limiting the production of the inflammatory cytokines IFN-γ and IL-6 in the brain, all of which contributed to protecting mice against T. gondii lethal challenge infection. Our findings suggest that IN delivery of ROP4 rBVs induced better mucosal and systemic immunity against the lethal T. gondii challenge infection compared to oral immunization.