Toxoplasmosis and behavioural changes

[Ocular toxoplasmosis]

Ocular toxoplasmosis is the most common cause of posterior uveitis worldwide, with an estimated incidence of 8.4%. It follows infection by the ubiquitous parasite Toxoplasma gondii. The diagnosis is based on clinical examination looking for uveitis and most often retinochoroiditis. Microbiological confirmation is an element of positive diagnosis. The indications for treatment remain debated, whether for acute forms or recurrences.

Skrjabingylus chitwoodorum in a rabies-positive striped skunk in Texas

We describe here a case of the sinus roundworm, Skrjabingylus chitwoodorum, found incidentally in a rabies-positive striped skunk (Mephitis mephitis) in Texas, USA. Skunks serve as a natural definitive host for this metastrongylid nematode in North America, in which infections result in observable damage to the host cranium, where adult parasites reside. Additionally, skunks are considered the primary reservoir of rabies in Texas. In November 2022, the animal was discovered in northern Texas displaying neurologic signs before euthanasia and submission to the Oklahoma Animal Disease Diagnostic Laboratory for rabies testing. Direct fluorescent antibody testing indicated that the animal was rabies-positive, and, upon tissue collection, numerous adult nematodes were recovered from the cranium and identified as S. chitwoodorum by morphology and amplification of the mitochondrial cytochrome c oxidase subunit I gene. Histologically, we found lymphohistiocytic meningitis in several loci and chronic sinusitis rostral to the cribriform plate. Due to behavioral abnormalities, we additionally tested for Toxoplasma gondii via PCR, but no parasite DNA was detected. Concurrent infection by S. chitwoodorum and rabies virus may contribute to neurologic signs in skunks.

Seroprevalence of Toxoplasma gondii immunoglobulins and its association with systemic lupus erythematosus: A systematic review and meta-analysis

BACKGROUND

The exact cause of systemic lupus erythematosus (SLE) is still unknown. However, hormonal, genetic, and environmental factors may play significant roles in its development. Infection has been recognized as a crucial trigger for SLE development. Several studies have reported a higher prevalence of Toxoplasma gondii infections in patients with SLE than in healthy individuals. However, these results were inconsistent. Therefore, this study aimed to conduct a systematic review and meta-analysis of published studies to provide a definitive conclusion regarding the relationship between T. gondii infection and SLE.

MATERIALS AND METHODS

We conducted a comprehensive search across diverse databases using an array of search tools to uncover pertinent literature. Following the stringent application of the inclusion and exclusion criteria, we carefully selected the appropriate reports for our meta-analysis. Using Comprehensive Meta-Analysis software v4, we analyzed the data and determined the prevalence of antibodies against T. gondii in patients affected with SLE. To investigate the correlation between T. gondii seropositivity and SLE, we computed the risk ratios (RRs) and 95% confidence intervals (CI).

RESULTS

Eleven studies were considered eligible for inclusion in the present study. The prevalence of anti-IgG and IgM antibodies against T. gondii was 33.9% and 7.7%, respectively. A significant association between T. gondii IgG seropositivity and SLE was observed when compared to the controls (risk ratio = 2.14, 95% CI = 1.42 to 3.22, p = .000). However, IgM seropositivity against T. gondii was comparable between patients with SLE and healthy controls.

CONCLUSIONS

In summary, this study suggests that T. gondii IgG is more prevalent in patients with SLE than in healthy individuals in areas where T. gondii infections are more frequent. However, an exact cause-and-effect relationship still needs to be established. Therefore, additional research is necessary to validate these findings and to investigate the underlying mechanisms.

Therapeutic potential of oral alginate nanoparticles against experimental toxoplasmosis

Side effects and low efficacy of current anti-toxoplasmosis therapeutics against encysted bradyzoites necessitate research into alternative safe therapeutic options. The safety, immunostimulatory, and antimicrobial properties of alginate nanoparticle formulation (Alg-NP) highlight its potential as an oral therapy against acute toxoplasmosis. In the current study, Alg-NP was formulated and characterized and then assessed for its anti-Toxoplasma effects using parasitological, ultrastructural, immunological, and histopathological studies. Treatment with Alg-NP significantly prolonged mice survival and reduced the parasite burden in both peritoneal fluid and tissue impression smears. In addition, it altered parasite viability and caused severe tachyzoite deformities as evidenced by ultrastructural studies. Alg-NP induced high levels of serum IFN-γ in infected mice with significant amelioration in histopathological changes in both hepatic and splenic tissue sections. In conclusion, Alg-NP could be considered a promising therapeutic agent against acute murine toxoplasmosis, and owing to its safety, it could potentially be enlisted for human use.

Contrasting Disease Progression, Microglia Reactivity, Tolerance, and Resistance to Toxoplasma gondii Infection in Two Mouse Strains

Our study investigated the innate immune response to Toxoplasma gondii infection by assessing microglial phenotypic changes and sickness behavior as inflammatory response markers post-ocular tachyzoite instillation. Disease progression in Swiss albino mice was compared with the previously documented outcomes in BALB/c mice using an identical ocular route and parasite burden (2 × 105 tachyzoites), with saline as the control. Contrary to expectations, the Swiss albino mice displayed rapid, lethal disease progression, marked by pronounced sickness behaviors and mortality within 11-12 days post-infection, while the survivors exhibited no apparent signs of infection. Comparative analysis revealed the T. gondii-infected BALB/c mice exhibited reduced avoidance of feline odors, while the infected Swiss albino mice showed enhanced avoidance responses. There was an important increase in microglial cells in the dentate gyrus molecular layer of the infected Swiss albino mice compared to the BALB/c mice and their respective controls. Hierarchical cluster and discriminant analyses identified three microglial morphological clusters, differentially affected by T. gondii infection across strains. The BALB/c mice exhibited increased microglial branching and complexity, while the Swiss albino mice showed reduced shrunken microglial arbors, diminishing their morphological complexity. These findings highlight strain-specific differences in disease progression and inflammatory regulation, indicating lineage-specific mechanisms in inflammatory responses, tolerance, and resistance. Understanding these elements is critical in devising control measures for toxoplasmosis.

Multiomics and bioinformatics identify differentially expressed effectors in the brain of Toxoplasma gondii infected masked palm civet

Introduction

The masked palm civet (Paguma larvata) serves as a reservoir in transmitting pathogens, such as Toxoplasma gondii, to humans. However, the pathogenesis of T. gondii infection in masked palm civets has not been explored. We studied the molecular changes in the brain tissue of masked palm civets chronically infected with T. gondii ME49.

Methods

The differentially expressed proteins in the brain tissue were investigated using iTRAQ and bioinformatics.

Results

A total of 268 differential proteins were identified, of which 111 were upregulated and 157 were downregulated. KEGG analysis identified pathways including PI3K-Akt signaling pathway, proteoglycans in cancer, carbon metabolism, T-cell receptor signaling pathway. Combing transcriptomic and proteomics data, we identified 24 genes that were differentially expressed on both mRNA and protein levels. The top four upregulated proteins were REEP3, REEP4, TEP1, and EEPD1, which was confirmed by western blot and immunohistochemistry. KEGG analysis of these 24 genes identified signaling cascades that were associated with small cell lung cancer, breast cancer, Toll-like receptor signaling pathway, Wnt signaling pathways among others. To understand the mechanism of the observed alteration, we conducted immune infiltration analysis using TIMER databases which identified immune cells that are associated with the upregulation of these proteins. Protein network analysis identified 44 proteins that were in close relation to all four proteins. These proteins were significantly enriched in immunoregulation and cancer pathways including PI3K-Akt signaling pathway, Notch signaling pathway, chemokine signaling pathway, cell cycle, breast cancer, and prostate cancer. Bioinformatics utilizing two cancer databases (TCGA and GEPIA) revealed that the four genes were upregulated in many cancer types including glioblastoma (GBM). In addition, higher expression of REEP3 and EEPD1 was associated with better prognosis, while higher expression of REEP4 and TEP1 was associated with poor prognosis in GBM patients.

Discussion

We identified the differentially expressed genes in the brain of T. gondii infected masked palm civets. These genes were associated with various cellular signaling pathways including those that are immune- and cancer-related.

Redundant targeting signals of the apicoplast-resident protein TgMnmA in Toxoplasma gondii involve trans-organellar function

The apicoplast, which is the result of secondary endosymbiosis, is a distinctive subcellular organelle and a crucial therapeutic target for apicomplexan parasites. The majority of apicoplast-resident proteins are encoded by the nuclear genome and target the apicoplast via bipartite targeting signals consisting of a signal peptide and a transit peptide. The properties and functions of these peptides are poorly understood, which hinders the identification of apicoplast proteins and the study for plastid evolution. Here, the targeting signals of the recently discovered apicoplast tRNA thiouridylase TgMnmA of Toxoplasma gondii were analyzed. Our data using a reporter (the enhanced green fluorescent protein) fused with individual fragments containing various numbers of its N-terminal amino acids unequivocally revealed that the first 28 amino acids of TgMnmA functioned as a signal peptide for cellular secretion. The N-terminal 150 amino acids were sufficient to direct the fusion protein to the apicoplast, whereas its deletion caused the fusion protein to be localized to the mitochondrion. Our data further demonstrated that the apicoplast, rhoptry, and mitochondrion shared similar targeting signals, indicating that the apicoplast localization peptide was trans-organellar in function. In addition, the apicoplast localization peptide was important for the healthy proliferation of tachyzoites. In conclusion, the targeting signals of the nucleus-encoded apicoplast-targeted protein TgMnmA have been mapped out and the importance of this localization peptide has been elucidated in the current study.

Behavioral and Neuropathological Changes After Toxoplasma gondii Ocular Conjunctival Infection in BALB/c Mice

Ocular infection with Toxoplasma gondii causes toxoplasmosis in mice. However, following ocular infection with tachyzoites, the cause of the accompanying progressive changes in hippocampal-dependent tasks, and their relationship with the morphology and number of microglia, is less well understood. Here, in 6-month-old, female BALB/c mice, 5 μl of a suspension containing 48.5 × 10⁶ tachyzoites/ml was introduced into the conjunctival sac; control received an equal volume of saline. Before and after instillation, all mice were subject to an olfactory discrimination (OD) test, using predator (cat) feces, and to an open-field (OF) task. After the behavioral tests, the animals were culled at either 22 or 44 days post-instillation (dpi), and the brains and retinas were dissected and processed for immunohistochemistry. The total number of Iba-1-immunolabeled microglia in the molecular layer of the dentate gyrus was estimated, and three-dimensional reconstructions of the cells were evaluated. Immobility was increased in the infected group at 12, 22, and 43 dpi, but the greatest immobility was observed at 22 dpi and was associated with reduced line crossing in the OF and distance traveled. In the OD test, infected animals spent more time in the compartment with feline fecal material at 14 and at 43 dpi. No OD changes were observed in the control group. The number of microglia was increased at 22 dpi but returned to control levels by 44 dpi. These changes were associated with the differentiation of T. gondii tachyzoites into bradyzoite-enclosed cysts within the brain and retina. Thus, infection of mice with T. gondii alters exploratory behavior, gives rise to a loss in predator’s odor avoidance from 2 weeks after infection, increased microglia number, and altered their morphology in the molecular layer of the dentate gyrus.

Epigenetic Manipulation of Psychiatric Behavioral Disorders Induced by Toxoplasma gondii

Toxoplasma gondii is known to have a complex life cycle and infect almost all kinds of warm-blooded animals around the world. The brain of the host could be persistently infected by cerebral cysts, and a variety of psychiatric disorders such as schizophrenia and suicide have been reported to be related with latent toxoplasmosis. The infected animals showed fear reduction and a tendency to be preyed upon. However, the mechanism of this “parasites manipulation” effects have not been elucidated. Here, we reviewed the recent infection prevalence of toxoplasmosis and the evidence of mental and behavioral disorders induced by T. gondii and discussed the related physiological basis including dopamine dysregulation and gamma-aminobutyric acid (GABA) pathway and the controversial opinion of the necessity for cerebral cysts existence. Based on the recent advances, we speculated that the neuroendocrine programs and neurotransmitter imbalance may play a key role in this process. Simultaneously, studies in the evaluation of the expression pattern of related genes, long noncoding RNAs (lncRNAs), and mRNAs of the host provides a new point for understanding the mechanism of neurotransmitter dysfunction induced by parasite manipulation. Therefore, we summarized the animal models, T. gondii strains, and behavioral tests used in the related epigenetic studies and the responsible epigenetic processes; pinpointed opportunities and challenges in future research including the causality evidence of human psychiatric disorders, the statistical analysis for rodent-infected host to be more vulnerable preyed upon; and identified responsible genes and drug targets through epigenetics.

Association between Toxoplasma gondii and systemic lupus erythematosus: A systematic review and meta-analysis

Infecting approximately one-third of the world's population, the intraneuronal parasite Toxoplasma gondii has been associated with several autoimmune diseases. While Toxoplasma gondii may be protective against multiple sclerosis, other findings have negatively associated Toxoplasma gondii with different autoimmune diseases, including systemic lupus erythematosus. To further characterize the association between Toxoplasma gondii and systemic lupus erythematosus, we completed a systematic review and meta-analysis of published studies looking at the association between Toxoplasma gondii and systemic lupus erythematosus. The primary results of a random-effects model showed an odds ratio of 2.34 (95% confidence interval 1.17–4.69, P = 0.017), indicating the odds of Toxoplasma gondii seropositivity were 2.34 times higher in the group with systemic lupus erythematosus than in the healthy control group. Few available source studies, an overall lack of information about immunosuppressive status, and little information about sex composition and assays limit this finding and indicate the need for additional research to further characterize the association between systemic lupus erythematosus and Toxoplasma gondii.

Toxoplasma gondii Infection and Suicidal Behavior in People with Alcohol Consumption

We determined the association between T. gondii infection and suicidal behavior in people with alcohol consumption. One-thousand four-hundred and twenty-three people with alcohol consumption were screened for suicidal behavior and tested for anti-T. gondii IgG and IgM antibodies using commercially available enzyme-linked immunosorbent assays. Anti-T. gondii IgG antibodies were found in 34 of 224 (15.2%) individuals with suicidal ideation and in 118 (9.8%) of 1199 individuals without suicidal ideation (OR: 1.63; 95% CI: 1.08–2.47; p = 0.01). Seropositivity to T. gondii was associated with suicidal ideation in women (OR: 2.24; 95% CI: 1.33–3.78; p = 0.001) and in individuals aged ≤30 years (OR: 2.68; 95% CI: 1.22–5.87; p = 0.01) and >50 years (OR: 2.85; 95% CI: 1.19–6.77; p = 0.01). Anti-T. gondii IgG antibodies were found in 17 of 136 (12.5%) individuals with suicide attempts and in 135 (10.5%) of 1287 individuals without suicide attempts (OR: 1.21; 95% CI: 0.71–2.08; p = 0.47). Seroprevalence of T. gondii infection was associated with suicide attempts in women (OR: 1.88; 95% CI: 0.99–3.55; p = 0.04). No association between anti-T. gondii IgM and suicidal ideation or suicide attempts was found. Results suggest that T. gondii infection is associated with suicidal behavior in people with alcohol consumption.

Dissociating direct and indirect effects: a theoretical framework of how latent toxoplasmosis affects cognitive profile across the lifespan

About one-third of the world's population has latent toxoplasmosis, which is typically most prevalent in old age due to its lifelong persistence. Most infected people do not reveal clinically relevant symptoms, but T. gondii might trigger cognitive changes in otherwise asymptomatic individuals. As intact cognitive processes are essential for various achievements and successful aging, this review focuses on the cognitive profile associated with latent toxoplasmosis across the lifespan. It could be explained by a shift in balance between direct effects (increased dopamine synthesis) and indirect effects (neurodegeneration and chronic inflammation, which can decrease dopamine levels). Based thereon, we provide a possibly comprehensive framework of how T. gondii can differently affect cognitive performance across the lifespan (i.e., from increased catecholaminergic signaling in young age to decreased signaling in old age). We outline how future studies may inform our knowledge on the role of individual differences in response to T. gondii and how longitudinal studies can help trace the temporal dynamics in the shift of the balance between direct and indirect effects.

Seroprevalence of toxoplasma gondii infection: An umbrella review of updated systematic reviews and meta-analyses

Objectives:

Toxoplasmosis is one of the neglected parasitic disease in humans and animals that produced via toxoplasma gondii. This study we implemented an umbrella review of all existing systematic reviews, meta-analyzing studies to apprise, and summarize seroprevalence of human toxoplasmosis in worldwide.

Methods:

The search was carried out in databases including: Pub Med, Google Scholar, Science Direct, Scopus, Web of Science, Cochrane, and global health from their start dates until December 2018 in Persian and English language. A total of 21 systematics review and meta-analysis met the inclusion criteria of umbrella review. The Q test and the I² statistic were used to evaluate heterogeneities. Quality assessment were performed and made use of the AMSTAR tool.

Results:

The estimated pooled seroprevalence of T. gondii infection in blood donors, Immunocompromised patients, childbearing age women, general population, newborns and children, pregnant women and overall was 33% (95% CI, 29.0–38.0%), 42.0% (95 CI, 34.0–49.0%), 32.0% (CI, 26.0–38.0%), 42.0% (CI, 38.0–45.0%), 4.0% (CI, 2.0–5.0%), 40.0% (CI,37.0–44.0%), and 36% (CI, 24.0–48.0%), respectively.

Conclusion:

The results of our umbrella review show a higher seroprevalence of T. gondii infection in immunocompromised patients, general population, pregnant women, blood donors, childbearing age women, and newborn groups, respectively. Routine serologic screening test and health education by primary care physicians for Toxoplasmosis is recommended to be conducted in high-risk groups in the endemic region.