The immunobiology of the innate response to Toxoplasma gondii

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.

Baseline circulating biomarkers, their changes, and subsequent suicidal ideation and depression severity at 6 months: A prospective analysis in patients with mood disorders

BACKGROUND

Identifying circulating biomarkers associated with prospective suicidal ideation (SI) and depression could help better understand the dynamics of these phenomena and identify people in need of intense care. In this study, we investigated the associations between baseline peripheral biomarkers implicated in neuroplasticity, vascular homeostasis and inflammation, and prospective SI and depression severity during 6 months of follow-up in patients with mood disorders.

METHODS

149 patients underwent a psychiatric evaluation and gave blood to measure 32 plasma soluble proteins. At follow-up, SI incidence over six months was measured with the Columbia Suicide Severity Rating Scale, and depressive symptoms were assessed with the Inventory for Depressive Symptomatology. Ninety-six patients provided repeated blood samples. Statistical analyses included Spearman partial correlation and Elastic Net regression, followed by the covariate-adjusted regression models.

RESULTS

51.4 % (N = 71) of patients reported SI during follow-up. After adjustment for covariates, higher baseline levels of interferon-γ were associated with SI occurrence during follow-up. Higher baseline interferon-γ and lower orexin-A were associated with increased depression severity, and atypical and anxious, but not melancholic, symptoms. There was also a tendency for associations of elevated baseline levels of interferon-γ, interleukin-1β, and lower plasma serotonin levels with SI at the six-month follow-up time point. Meanwhile, reduction in transforming growth factor- β1 (TGF-β1) plasma concentration correlated with atypical symptoms reduction.

CONCLUSION

We identified interferon-γ and orexin-A as potential predictive biomarkers of SI and depression, whereas TGF-β1 was identified as a possible target of atypical symptoms.

Trem2/Syk/PI3K axis contributes to the host protection against Toxoplasma gondii-induced adverse pregnancy outcomes via modulating decidual macrophages

Decidual macrophages residing at the maternal-fetal interface have been recognized as pivotal factors for maintaining normal pregnancy; however, they are also key target cells of Toxoplasma gondii (T. gondii) in the pathology of T. gondii-induced adverse pregnancy. Trem2, as a functional receptor on macrophage surface, recognizes and binds various kinds of pathogens. The role and underlying mechanism of Trem2 in T. gondii infection remain elusive. In the present study, we found that T. gondii infection downregulated Trem2 expression and that Trem2-/- mice exhibited more severe adverse pregnancy outcomes than wildtype mice. We also demonstrated that T. gondii infection resulted in increased decidual macrophages, which were significantly reduced in the Trem2-/- pregnant mouse model as compared to wildtype control animals. We further described the inhibited proliferation, migration, and invasion functions of trophoblast cell by T. gondii antigens through macrophages as an "intermediate bridge", while this inhibition can be rescued by Trem2 agonist HSP60. Concurrently, Trem2 deficiency in bone marrow-derived macrophages (BMDMs) heightened the inhibitory effect of TgAg on the migration and invasion of trophoblast cells, accompanied by higher pro-inflammatory factors (IL-1β, IL-6 and TNF-α) but a lower chemokine (CXCL1) in T. gondii antigens-treated BMDMs. Furthermore, compelling evidence from animal models and in vitro cell experiments suggests that T. gondii inhibits the Trem2-Syk-PI3K signaling pathway, leading to impaired function of decidual macrophages. Therefore, our findings highlight Trem2 signaling as an essential pathway by which decidual macrophages respond to T. gondii infection, suggesting Trem2 as a crucial sensor of decidual macrophages and potential therapeutic target in the pathology of T. gondii-induced adverse pregnancy.

Toxoplasma gondii IgG serointensity and cognitive function in bipolar disorder

BACKGROUND

Alongside affective episodes, cognitive dysfunction is a core symptom of bipolar disorder. The intracellular parasite T. gondii has been positively associated with both, the diagnosis of bipolar disorder and poorer cognitive performance, across diagnostic boundaries. This study aims to investigate the association between T. gondii seropositivity, serointensity, and cognitive function in an euthymic sample of bipolar disorder.

METHODS

A total of 76 participants with bipolar disorder in remission were tested for T. gondii-specific IgG and IgM antibodies and for cognitive performance using neuropsychological test battery. Cognitive parameters were categorized into three cognitive domains (attention and processing speed, verbal memory, and executive function). Statistical analysis of associations between continuous indicators of cognitive function as dependent variables in relationship to T. gondii, included multivariate analyses of co-variance for seropositivity, and partial correlations with IgG serointensity in IgG seropositives. All analyses were controlled for age and premorbid IQ.

RESULTS

In seropositives (n = 27), verbal memory showed significant inverse partial correlations with IgG antibody levels (short delay free recall (r=-0.539, p = 0.005), long delay free recall (r=-0.423, p = 0.035), and immediate recall sum trial 1-5 (r=-0.399, p = 0.048)). Cognitive function did not differ between IgG seropositive and seronegative individuals in any of the cognitive domains (F (3,70) = 0.327, p = 0.806, n = 76). IgM positives (n = 7) were too few to be analyzed.

CONCLUSIONS

This investigation is the first to show an association between T. gondii IgG serointensity and memory function in a well-diagnosed bipolar disorder sample. It adds to the existing literature on associations between latent T. gondii infection and cognition in bipolar disorder, while further research is needed to confirm and expand our findings, eliminate potential sources of bias, and establish cause-effect relationships.

Seroprevalence of Toxoplasma gondii and Neospora spp. in horse population of Tehran, Iran

Neospora spp. and Toxoplasma gondii are two closely related protozoan parasites that are widely distributed throughout the world. Horses can act as intermediate hosts for both parasites and can acquire disease. Blood samples were taken from 487 clinically healthy horses from 17 different mechanized stables in Tehran, the capital of Iran, during September and November of 2022. IFAT and ELISA were employed to detect antibodies directed against Neospora spp. and T. gondii. The anti-N. caninum antibodies were detected in 52 of the horses (10.67%) based on IFAT and in 86 of the 487 horses (17.65%) based on the ELISA test. Also, antibodies against T. gondii were detected in 41 horses (8.42%) based on IFAT and in 63 of 487 horses (12.94%) based on the ELISA test. Also, in 6 of the horses (1.23%) based on IFAT and in 13 of the 487 horses (2.67%) based on the ELISA test, double positivity suggested co-infection with both parasites. Gender, age groups, and the presence of dogs for neosporosis, and age groups and the presence of cats for toxoplasmosis, could be considered factors having an influence on the seroprevalences (P < 0.05). The results proved the importance of the urgent implementation of stringent regulatory measures to prevent and control the spread of these parasites.

Copaifera spp. oleoresins and two isolated compounds (ent-kaurenoic and ent-polyalthic acid) inhibit Toxoplasma gondii growth in vitro

Toxoplasmosis affects about one-third of the world's population. The disease treatment methods pose several side effects and do not efficiently eliminate the parasite, making the search for new therapeutic approaches necessary. We aimed to assess the anti-Toxoplasma gondii activity of four Copaifera oleoresins (ORs) and two isolated diterpene acids, named ent-kaurenoic and ent-polyalthic acid. We used HeLa cells as an experimental model of toxoplasmosis. Uninfected and infected HeLa cells were submitted to the treatments, and the parasite intracellular proliferation, cytokine levels and ROS production were measured. Also, tachyzoites were pre-treated and the parasite invasion was determined. Finally, an in silico analysis was performed to identify potential parasite targets. Our data show that the non-cytotoxic concentrations of ORs and diterpene acids controlled the invasion and proliferation of T. gondii in HeLa cells, thus highlighting the possible direct action on parasites. In addition, some compounds tested controlled parasite proliferation in an irreversible manner. An additional and non-exclusive mechanism of action involves the modulation of host cell components, by affecting the upregulation of the IL-6. Additionally, molecular docking suggested that ent-polyalthic acid has a high affinity for the active site of the TgCDPK1 protein. Copaifera ORs have great antiparasitic activity against T. gondii, and this effect can be partially explained by the presence of the isolated compounds ent-kaurenoic and ent-polyalthic acid.

Potential Association Between Latent Toxoplasma gondii Infection and Suicide Attempts: A Case-Control Registry-Based Study

Toxoplasma gondii is a ubiquitous parasitic protozoan that may be an important cause of neurological and psychiatric diseases. The purpose of this case-control registry-based study was to evaluate the prevalence of T. gondii infection and related risk factors among subjects who attempted suicide by drug use and a control group at the Iranian National Registry Center for Toxoplasmosis in Mazandaran Province, northern Iran. Baseline data were collected from participants using a questionnaire, and a blood sample was taken from each individual. The plasma was prepared for serological analysis, whereas the buffy coat was used for molecular analysis. Out of 282 individuals (147 cases with suicide attempters [SA] and 135 controls), 42.9% of patients and 16.3% of control subjects were positive for anti-Toxoplasma immunoglobin G (IgG), but all participants were negative for T. gondii DNA and anti-Toxoplasma immunoglobin M. Based on multiple logistic regressions, IgG seropositivity in SA in the age group of 20-30 years was 3.22 times higher than that in the control group (p < 0.001). These findings suggest that latent T. gondii infection among SA is significantly higher than that in healthy individuals, indicating a potential association between latent toxoplasmosis and SA at least in the studied area. Further research is needed to shed light on the potential association between T. gondii and suicide among different populations and areas of the world.

Toxoplasma gondii seropositivity and cognitive functioning in older adults: an analysis of cross-sectional data of the National Health and Nutrition Examination Survey 2011-2014

OBJECTIVES

This study sought to examine the relationship between Toxoplasma gondii seropositivity and cognitive function in older adults.

DESIGN

An observational cross-sectional study.

SETTING

The National Health and Nutrition Examination Survey (NHANES) study took place at participants' homes and mobile examination centres.

PARTICIPANTS

A total of 2956 older adults aged 60 and above from the NHANES from 2011 to 2014 were included in the study. Exposure of interest: participants had serum Toxoplasma gondii antibody analysed in the laboratory. A value>33 IU/mL was categorised as seropositive for Toxoplasma gondii infection; <27 IU/mL was categorised as seronegative for Toxoplasma gondii infection.

PRIMARY AND SECONDARY OUTCOME MEASURES

Cognitive tests included the Consortium to Establish a Registry for Alzheimer's Disease Word Learning subtest (CERAD-WL) for immediate and delayed memory, the Animal Fluency Test (AFT), and the Digit Symbol Substitution Test (DSST).

RESULTS

About half of the 2956 participants (mean age 70.0) were female (51.0%), non-Hispanic White (48.3%), and completed some college or above (48.3%). A total of 703 participants were positive for Toxoplasma gondii infection (23.8%). Adjusted linear regression showed that compared with participants with negative Toxoplasma gondii infection, those with positive Toxoplasma gondii infection had lower CERAD-WL immediate memory (beta (β) -0.16, 95% CI -0.25 to -0.07), CERAD-WL delayed memory (β -0.15, 95% CI -0.24 to -0.06), AFT (β -0.15, 95% CI -0.24 to -0.06), DSST (β -0.34, 95% CI -0.43 to -0.26), and global cognition (β -0.24, 95% CI -0.32 to -0.16) z-scores after controlling for the covariates.

CONCLUSIONS

Toxoplasma gondii seropositivity is associated with worse immediate and delayed verbal learning, language proficiency, executive functioning, processing speed, sustained attention, working memory, as well as global cognition in older adults. Public health measures aiming at preventing Toxoplasma gondii infection may help preserve cognitive functioning in older adults.

Plasma Cholinesterase Activity in Patients With Rheumatoid Arthritis and Toxoplasmosis

Background and objective Rheumatoid arthritis (RA) is a chronic autoimmune disease causing synovium inflammation and functional impairment. Toxoplasmosis is an intracellular zoonotic parasitic infection and a risk factor in immunosuppressed diseases including RA. The involvement of the cholinergic mechanism is not clear when both diseases exist in combination. This study aimed to examine plasma cholinesterase (ChE) activity in patients suffering from RA with concomitant toxoplasmosis, taking into account the enzyme susceptibility to in vitro inhibitory challenge with the organophosphate dichlorvos in RA patients. Methods This was a case-control study involving 88 RA patients and 61 healthy controls of both genders. The RA patients were allocated into three groups. The first group received no therapy (n=14), the second group received conventional anti-arthritis therapy (n=49), and the third group received conventional + biologic therapy (n=25). Plasma ChE activity was determined by an electrometric method. Plasma samples were screened for Toxoplasma gondii (T. gondii) infection, using ELISA T. gondii antibodies IgG and IgM. In vitro inhibition of plasma ChE activity was assessed by incubating the samples with dichlorvos at 0.25 and 0.5 μM. The time-dependent dichlorvos (0.25 μM)-induced plasma ChE inhibition and its kinetics were determined. Results The RA patients comprised 76 (86.4%) females and 12 males (13.6%), whereas healthy controls included 22 (36.1%) females and 39 (63.9%) males. The rates of toxoplasmosis IgG positivity in controls and RA patients were 26.2% and 39.8%, respectively. Plasma ChE activity in patients with RA was significantly higher than that in the control group, by 16%. Plasma ChE values of RA patients with conventional therapy and conventional + biologic therapy were higher than that of the control group, by 18% and 27%, respectively. Odds and risk ratios of elevated plasma ChE activity (20%) in RA patients with therapy indicated that high plasma ChE activity among RA patients with therapy is a risk factor. The plasma ChE activity of T. gondii IgG-positive RA patients was not significantly different from that of the IgG-negative ones. Dichlorvos at 0.25 and 0.5 μM significantly inhibited in vitro plasma ChE activity in controls and RA patients. The rates of plasma ChE inhibition by dichlorvos were lower in the RA groups with conventional therapy in comparison with those in the control group (77% vs. 91%). Examining the dichlorvos time-dependent ChE inhibition kinetics, RA groups showed increases in the half-life of inhibition by 23.6% to 32.7% and the total inhibition time by 23.5% to 32.5%, together with decreases in the inhibition rate constant by 19% to 24.5%, an indication of reduced inhibition rate of plasma ChE activity compared to that of the control group. Conclusions The autoimmune nature of RA and its chronicity might have contributed to the increase in plasma ChE activity among the patients. This increase in enzyme activity could be a risk factor in RA patients undergoing conventional therapy alone or in combination with biologic therapy; however, the clinical significance of such a condition remains obscure at present. The in vitro inhibition of plasma ChE activity in RA patients suggests reduced susceptibility of the enzyme to ChE inhibition by dichlorvos. Toxoplasmosis was not a risk factor when plasma ChE activity was taken into account among RA patients.

CD4+ T Cell Responses to Toxoplasma gondii Are a Double-Edged Sword

CD4+ T cells have been found to play critical roles in the control of both acute and chronic Toxoplasma infection. Previous studies identified a protective role for the Toxoplasma CD4+ T cell-eliciting peptide AS15 (AVEIHRPVPGTAPPS) in C57BL/6J mice. Herein, we found that immunizing mice with AS15 combined with GLA-SE, a TLR-4 agonist in emulsion adjuvant, can be either helpful in protecting male and female mice at early stages against Type I and Type II Toxoplasma parasites or harmful (lethal with intestinal, hepatic, and spleen pathology associated with a storm of IL6). Introducing the universal CD4+ T cell epitope PADRE abrogates the harmful phenotype of AS15. Our findings demonstrate quantitative and qualitative features of an effective Toxoplasma-specific CD4+ T cell response that should be considered in testing next-generation vaccines against toxoplasmosis. Our results also are cautionary that individual vaccine constituents can cause severe harm depending on the company they keep.

Anti-Toxoplasma gondii Effects of Lipopeptide Derivatives of Lycosin-I

Toxoplasmosis, caused by Toxoplasma gondii (T. gondii), is a serious zoonotic parasitic disease. We previously found that Lycosin-I exhibited anti-T. gondii activity, but its serum stability was not good enough. In this study, we aimed to improve the stability and activity of Lycosin-I through fatty acid chain modification, so as to find a better anti-T. gondii drug candidate. The α/ε-amino residues of different lysine residues of Lycosin-I were covalently coupled with lauric acid to obtain eight lipopeptides, namely L-C12, L-C12-1, L-C12-2, L-C12-3, L-C12-4, L-C12-5, L-C12-6, and L-C12-7. Among these eight lipopeptides, L-C12 showed the best activity against T. gondii in vitro in a trypan blue assay. We then conjugated a shorter length fatty chain, aminocaproic acid, at the same modification site of L-C12, namely L-an. The anti-T. gondii effects of Lycosin-I, L-C12 and L-an were evaluated via an invasion assay, proliferation assay and plaque assay in vitro. A mouse model acutely infected with T. gondii tachyzoites was established to evaluate their efficacy in vivo. The serum stability of L-C12 and L-an was improved, and they showed comparable or even better activity than Lycosin-I did in inhibiting the invasion and proliferation of tachyzoites. L-an effectively prolonged the survival time of mice acutely infected with T. gondii. These results suggest that appropriate fatty acid chain modification can improve serum stability and enhance anti-T. gondii effect of Lycosin-I. The lipopeptide derivatives of Lycosin-I have potential as a novel anti-T. gondii drug candidate.

Co-Immunization with DNA Vaccines Expressing SABP1 and SAG1 Proteins Effectively Enhanced Mice Resistance to Toxoplasma gondii Acute Infection

Toxoplasma gondii (T. gondii) has many intermediate hosts, obligately invades nucleated cells, and seriously threatens human and animal health due to a lack of effective drugs and vaccines. Sialic acid-binding protein 1 (SABP1) is a novel invasion-related protein that, like surface antigen 1 (SAG1), is found on the plasma membrane of T. gondii. To investigate the immunogenicity and protective efficacy of DNA vaccines expressing SABP1 and SAG1 proteins against T. gondii acute infection, the recombinant plasmids pVAX1-SABP1 and pVAX1-SAG1 were produced and administered intramuscularly in Balb/c mice. Serum antibody levels and subtypes, lymphocyte proliferation, and cytokines were used to assess immunized mice's humoral and cellular immune responses. Furthermore, the ability of DNA vaccines to protect mice against T. gondii RH tachyzoites was tested. Immunized mice exhibited substantially higher IgG levels, with IgG2a titers higher than IgG1. When the immune group mice's splenocytes were stimulated with T. gondii lysate antigen, Th1-type cytokines (IL-12p70, IFN-γ, and IL-2) and Th2-type cytokine (IL-4) increased significantly. The combined DNA vaccine significantly increased the immunized mouse survival compared to the control group, with an average death time extended by 4.33 ± 0.6 days (p < 0.0001). These findings show that DNA vaccines based on the SABP1 and SAG1 genes induced robust humoral and cellular immunity in mice, effectively protecting against acute toxoplasmosis and potentially serving as a viable option for vaccination to prevent T. gondii infection.

Metallic Nanoparticles and Core-Shell Nanosystems in the Treatment, Diagnosis, and Prevention of Parasitic Diseases

The usage of nanotechnology in the fight against parasitic diseases is in the early stages of development, but it brings hopes that this new field will provide a solution to target the early stages of parasitosis, compensate for the lack of vaccines for most parasitic diseases, and also provide new treatment options for diseases in which parasites show increased resistance to current drugs. The huge physicochemical diversity of nanomaterials developed so far, mainly for antibacterial and anti-cancer therapies, requires additional studies to determine their antiparasitic potential. When designing metallic nanoparticles (MeNPs) and specific nanosystems, such as complexes of MeNPs, with the shell of attached drugs, several physicochemical properties need to be considered. The most important are: size, shape, surface charge, type of surfactants that control their dispersion, and shell molecules that should assure specific molecular interaction with targeted molecules of parasites' cells. Therefore, it can be expected that the development of antiparasitic drugs using strategies provided by nanotechnology and the use of nanomaterials for diagnostic purposes will soon provide new and effective methods of antiparasitic therapy and effective diagnostic tools that will improve the prevention and reduce the morbidity and mortality caused by these diseases.

Nanoparticles as a Delivery System of Antigens for the Development of an Effective Vaccine against Toxoplasma gondii

Nanoparticles include particles ranging in size from nanometers to micrometers, whose physicochemical characteristics are optimized to make them appropriate delivery vehicles for drugs or immunogens important in the fight and/or prevention of infectious diseases. There has been a rise in the use of nanoparticles in preventive vaccine formulations as immunostimulatory adjuvants, and as vehicles for immunogen delivery to target immune cells. Toxoplasma is important worldwide, and may cause human toxoplasmosis. In immunocompetent hosts, infection is usually asymptomatic, but in immunocompromised patients it can cause serious neurological and ocular consequences, such as encephalitis and retinochoroiditis. Primary infection during pregnancy may cause abortion or congenital toxoplasmosis. Currently, there is no effective human vaccine against this disease. Evidence has emerged from several experimental studies testing nanovaccines showing them to be promising tools in the prevention of experimental toxoplasmosis. For the present study, a literature review was carried out on articles published over the last 10 years through the PubMed database, pertaining to in vivo experimental models of T. gondii infection where nanovaccines were tested and protection and immune responses evaluated. This review aims to highlight the way forward in the search for an effective vaccine for toxoplasmosis.

Immunological evaluation of a novel multi-antigenic DNA vaccine encoding SAG1, SAG3, MIC4, GRA5, GRA7, AMA1and BAG1 against Toxoplasma gondii in BALB/c mice

Many recent studies have been conducted to find new DNA vaccines based on Toxoplasma gondii antigens. DNA vaccines encoding complex of different antigens showed better immune responses compared to single antigen vaccine. In this study, we constructed a DNA vaccine encoding SAG1, SAG3, MIC4, GRA5, GRA7, AMA1 and BAG1 against T. gondii, and evaluated the immune response it induced in BALB/c mice. For this purposes, thirty BALB/c mice were randomly divided into three groups containing tenmice each. There were two negative control groups (PBSand pVAX1 vector) and one vaccination group (pVAX1-MAF, Multantigenic Fragment). On days 0, 14 and 28, the mice were immunized intramuscularly, and 5 weeks later they were challenged with T. gondii RH strain. The immune responses were evaluated using lymphocyte proliferation assay, T-cell subsets detection, and measurement of antibody and cytokine levels. The results showed that mice immunized with pVAX1-MAF developed high levels of IL-2, IL-12, IgG and IFN- γ as well as CD3+CD4+ T cells. In addition, the survival time of mice immunized by pVAX1-MAF was longer than that control mice. In conclusion, our results show that the multiple DNA vaccine encodingSAG1, SAG3, mic4, GRA5, GRA7, AMA and BAG1effectively enhanced humoral and cellular immune responses, and prolonged the survival time. Together this would suggest that further investigation may result in a promising candidate vaccine to treat toxoplasmosis.

Leaf hydroalcoholic extract and oleoresin from Copaifera multijuga control Toxoplasma gondii infection in human trophoblast cells and placental explants from third-trimester pregnancy

The conventional treatment of congenital toxoplasmosis is mainly based on the combination of sulfadiazine and pyrimethamine. However, therapy with these drugs is associated with severe side effects and resistance, requiring the study of new therapeutic strategies. There are currently many studies with natural products, including Copaifera oleoresin, showing actions against some pathogens, as Trypanosoma cruzi and Leishmania. In the present study, we investigated the effects of the leaf hydroalcoholic extract and oleoresin from Copaifera multijuga against Toxoplasma gondii in human villous (BeWo) and extravillous (HTR8/SVneo) trophoblast cells, as well as in human villous explants from third-trimester pregnancy. For this purpose, both cells and villous explants were infected or not with T. gondii, treated with hydroalcoholic extract or oleoresin from C. multijuga and analyzed for toxicity, parasite proliferation, cytokine and ROS production. In parallel, both cells were infected by tachyzoites pretreated with hydroalcoholic extract or oleoresin, and adhesion, invasion and replication of the parasite were observed. Our results showed that the extract and oleoresin did not trigger toxicity in small concentrations and were able to reduce the T. gondii intracellular proliferation in cells previously infected. Also, the hydroalcoholic extract and oleoresin demonstrated an irreversible antiparasitic action in BeWo and HTR8/SVneo cells. Next, adhesion, invasion and replication of T. gondii were dampened when BeWo or HTR8/SVneo cells were infected with pretreated tachyzoites. Finally, infected and treated BeWo cells upregulated IL-6 and downmodulated IL-8, while HTR8/SVneo cells did not change significantly these cytokines when infected and treated. Finally, both the extract and oleoresin reduced the T. gondii proliferation in human explants, and no significant changes were observed in relation to cytokine production. Thus, compounds from C. multijuga presented different antiparasitic activities that were dependent on the experimental model, being the direct action on tachyzoites a common mechanism operating in both cells and villi. Considering all these parameters, the hydroalcoholic extract and oleoresin from C. multijuga can be a target for the establishment of new therapeutic strategy for congenital toxoplasmosis.

Wheat Germ Oil and Propolis Decrease Parasite Burden and Restore Marked Histopathological Changes in Liver and Lung in Mice with Chronic Toxoplasmosis

Toxoplasmosis is a parasitic zoonotic disease with a worldwide distribution. Its effects can be critical in immunocompromised patients. However, there is a limited availability of effective, low-toxicity drugs against this disease, particularly in its chronic form. The present study evaluated the effect of propolis and wheat germ oil (WGO) as safe, natural products to reduce Toxoplasma cysts in experimentally infected mice. For the experiment, five groups (10 mice per group) were examined: Group 1: negative control (noninfected, nontreated); Group 2: positive control (infected, nontreated); Group 3: infected and treated with WGO at a dose of 0.2 mg/1.5 mL per kg body weight/day; Group 4: infected and treated with 0.1 mL propolis extract/day; and Group 5: infected and treated with a combination of WGO and propolis at the same doses as Group 3 and 4. After the mice were sacrificed, liver and lung specimens underwent histopathological examination, and the parasite burden was investigated by parasitological methods and quantified using real-time polymerase chain reaction. Notably, the results showed a substantial decrease in parasitic burden in Group 5 compared to the control group. These results were further confirmed by molecular analysis and quantification of the DNA concentration of the Toxoplasma P29 gene after treatment in all tested samples. Furthermore, the combination of propolis and WGO restored all histopathological changes in the liver and lungs. Taken together, these findings provide remarkably promising evidence of the effects of the combination of WGO and propolis against chronic toxoplasmosis in mice.

Immune Cell Reaction Associated with Coenurus cerebralis Infection in Sheep with Particular Reference to ELISA as a Diagnostic Tool

Simple Summary

Infected sheep with Coenurus cerebralis (C. cerebralis) were subjected to histopathological, hematological, immunological and serological examination. In histopathological sections, cerebral tissue showed an areolar cyst wall with many protoscolices attached to the tissue with necrosis and inflammatory cells’ aggregation. The infected sheep exhibited a significant alteration in blood profile when contrasted with apparently healthy sheep. Evaluation of ELISA specificity using two antigens showed specificities of 46.2% and 38.5% for fluid and scolex Ag, respectively. Meanwhile, accuracy ranged from 76.7% and 73.3% for fluid and scolex Ag, respectively. Levels of TNF-α and IFN-γ were significantly elevated in infected sheep when contrasted with control ones.

Abstract

Sturdy is a disease caused by Coenurus cerebralis (C. cerebralis) that typically affects the brain and spinal cord of sheep. So, this study aimed to detect the pathological, hematological and immunological changes caused by C. cerebralis in sheep. On examination, a total of 17 sheep out of 30 sheep (56.7%) from various regions in Egypt were found infected with C. cerebralis from May to August 2019. Each cyst was extracted from the sheep brain; in addition, tissue specimens were taken from the brain tissues for histopathological examination. The hematological profile was analyzed. Enzyme-Linked Immunosorbent Assay’s (ELISA) specificity and sensitivity were evaluated using cystic fluid and protoscolices antigens (Ag). The cell-mediated immunity against the C. cerebralis cyst was also assessed via quantitative Real Time—Polymerase Chain Reaction (qRT-PCR) to show alterations in mRNA expression of the Tumor Necrosis Factor-alpha (TNF-α) and gamma Interferon (IFN-γ) cytokines qRT-PCR. In histopathological sections, cerebral tissue showed an areolar cyst wall with many protoscolices attached to the tissue. The affected part showed prominent necrosis together with inflammatory cells’ aggregation. Hyperplastic proliferation of the ependymal cells was a common finding. The infected sheep exhibited significantly lower total erythrocyte numbers (ER), hemoglobin levels (Hb), packed cell volume (PCV), platelet numbers (PN) and segmented cell numbers compared to apparently healthy sheep. Despite the sensitivity for the indirect ELISA being 100% for both of the Ags (fluid and scolex), the evaluation of ELISA specificity using the two antigen (Ag) preparations showed specificities of 46.2% and 38.5% for fluid and scolex Ag, respectively. Meanwhile accuracy ranged from 76.7% and 73.3% for the fluid and scolex Ags, respectively, that showed the priority was directed to the fluid to be used as an ideal sample type for ELISA. Levels of TNF-α and IFN-γ were significantly elevated in infected sheep compared to non-infected control ones. In conclusion, C. cerebralis is a serious disease infecting sheep in Egypt revealing economic losses. Although this investigation supports preliminary information about the prevalence, pathological and serological characterization of C. cerebralis, further sequencing and phylogenetic analysis is needed to understand better the T. multiceps epidemiology in ruminants and canines in Egypt.

Toxoplasmosis in patients with an autoimmune disease and immunosuppressive agents: A multicenter study and literature review

Background

Cases of Toxoplasma reactivation or more severe primary infection have been reported in patients receiving immunosuppressive (IS) treatment for autoimmune diseases (AID). The purpose of this study was to describe features of toxoplasmosis occurring in patients with AID treated by IS therapy, excluded HIV-positive and transplant patients.

Methods

A multicenter descriptive study was conducted using data from the French National Reference Center for Toxoplasmosis (NRCT) that received DNA extracts or strains isolated from patients, associated with clinical data. Other cases were retrieved through a questionnaire sent to all French parasitology and internal medicine departments. Furthermore, a systematic literature review was conducted.

Results

61 cases were collected: 25 retrieved by the NRCT and by a call for observations and 36 from a literature review. Half of the cases were attributed to reactivation (50.9%), and most of cases (49.2%) were cerebral toxoplasmosis. The most common associated AID were rheumatoid arthritis (28%) and most frequent treatments were antimetabolites (44.3%). Corticosteroids were involved in 60.7% of cases. Patients had a favorable outcome (50.8%) but nine did not survive. For 12 cases, a successful Toxoplasma strain characterization suggested the possible role of this parasitic factor in ocular cases.

Conclusion

Although this remains a rare condition, clinicians should be aware for the management of patients and for the choice of IS treatment.

Toxoplasma gondii Rhoptry Protein 7 (ROP7) Interacts with NLRP3 and Promotes Inflammasome Hyperactivation in THP-1-Derived Macrophages

Toxoplasma gondii is a common opportunistic protozoan pathogen that can parasitize the karyocytes of humans and virtually all other warm-blooded animals. In the host’s innate immune response to T. gondii infection, inflammasomes can mediate the maturation of pro-IL-1β and pro-IL-18, which further enhances the immune response. However, how intercellular parasites specifically provoke inflammasome activation remains unclear. In this study, we found that the T. gondii secretory protein, rhoptry protein 7 (ROP7), could interact with the NACHT domain of NLRP3 through liquid chromatography-mass spectrometry analysis and co-immunoprecipitation assays. When expressing ROP7 in differentiated THP-1 cells, there was significant up-regulation in NF-κB and continuous release of IL-1β. This process is pyroptosis-independent and leads to inflammasome hyperactivation through the IL-1β/NF-κB/NLRP3 feedback loop. The loss of ROP7 in tachyzoites did not affect parasite proliferation in host cells but did attenuate parasite-induced inflammatory activity. In conclusion, these findings unveil that a T. gondii-derived protein is able to promote inflammasome activation, and further study of ROP7 will deepen our understanding of host innate immunity to parasites.

An evaluation of the level of testosterone, DHEA and prolactin among Toxoplasma gondii infected and uninfected infertile couples attending to Fatima Al-Zahra infertility treatment center, Babol, Northern Iran

Introduction/Aims: Toxoplasmosis modifies various hormones and cytokines in the infected hosts which may result in several disorders. This study was conducted to assess testosterone, DHEA, and prolactin concentration levels among Toxoplasma gondii infected and uninfected infertile couples. Methods: Blood samples were collected and sera were separated. The sera were analyzed for the detection of anti-Toxoplasma (IgG& IgM) antibodies using commercial ELISA kits. The level of DHEA was measured by ELISA and the levels of testosterone and prolactin were evaluated by enzyme-linked fluorescent assay (ELFA, VIDAS). Results: The overall seroprevalence of toxoplasmosis was 58.0% (218/376). Among women, 56.9% (107/188) and 6.5% (7/107) were positive for anti-T. gondii antibodies IgG and IgM, respectively. The IgG and IgM were detected in the sera of 111/188 (59.0%) and 9/111 (8.1%) in male subjects, respectively. A positive association was observed between T. gondii infection and the upper and lower ranges of the normal value of testosterone in males (x 2 = 6.8, p = 0.033) but not in females (x 2 = 0.62, p = 0.99). A positive correlation was seen between toxoplasmosis and the upper and lower ranges of the normal value of prolactin in females (x 2 = 6.5, p = 0.039) but not in male cases (x 2 = 1.06, p = 0.59). Conclusion: Our results demonstrated no statistically significant differences between the level of sexual hormones between Toxoplasma-infected individuals and Toxoplasma-free subjects suffering from infertility. These findings suggest that further studies should be performed on infertile cases with large sample sizes in a case-control format.

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.

Prevalence and Predictors of Toxoplasma gondii Infection in Psychiatric Inpatients in Fars Province, Southern Iran

BACKGROUND

Psychiatric patients are at increased risk of exposure to Toxoplasma gondii infection, which may be linked to their living facilities and behaviors. Limited knowledge on the prevalence of T. gondii infection and its associated risk factors in psychiatric patients are available to the international medical communities. Thus, the aim of the current study was to assess seroprevalence of T. gondii and its associated risk factors in psychiatric inpatients in Fars Province, southern Iran.

METHODS

This cross-sectional study was carried out on psychiatric patients hospitalized in Ibn Sina Hospital affiliated to Shiraz University of Medical Sciences, Fars Province, southern Iran, March to July 2021. Blood samples were collected from 318 psychiatric patients and assessed for the detection of IgG against T. gondii using enzyme-linked immunosorbent assay (ELISA). Moreover, structured questionnaires were completed for the participants at the time of sampling. Logistic regression analysis was used to assess possible associations between the latent toxoplasmosis and the variables.

RESULTS

The overall seroprevalence of anti-T. gondii IgG in psychiatric inpatients was 22.3% (71/318; 95% CI = 17.9-27.3). Multivariate analyses revealed that age > 30 years [adjusted odds ratio (AOR) = 2.24, 95% CI = 1.10-4.60, p = 0.03], contact with cats (AOR = 2.52, 95% CI = 1.14-5.58, p = 0.03), raw vegetable consumption (AOR = 3.65, 95% CI = 1.74-7.65, p = 0.001), raw/undercooked meat consumption (AOR = 4.30, 95% CI = 1.47-12.63, p = 0.008), suicide attempt (AOR = 3.77, 95% CI = 1.58-8.97, p = 0.003) and cigarette smoking history (AOR = 0.38, 95% CI = 0.17-0.83, p = 0.02) were independent risk factors for T. gondii infection.

CONCLUSION

The current results demonstrated that contact with cats, raw vegetable consumption and raw/undercooked meat consumption were independent risk factors for T. gondii seropositivity. Moreover, the current study showed significant associations between seropositivity of T. gondii and suicide attempts as well as negative associations between seropositivity of T. gondii and cigarette smoking in psychiatric inpatients using multivariate logistic regression.

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.

Toxoplasma gondii seropositivity in patients with depressive and anxiety disorders

Introduction

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

Methods

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

Results

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

Conclusions

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

Evaluation of Adjuvant Effectiveness of Alum-Propranolol Mixture on the Immunogenicity of Excreted/Secreted Antigens of Toxoplasma gondii RH Strain

Purpose: The introduction of novel adjuvants is an important step in attempts to develop a safe and more efficient vaccine. The present study was performed to determine whether the use of a mixed beta-adrenergic receptor antagonist propranolol (PRP) and aluminum (alum), as an adjuvant, have efficacy for Toxoplasma gondii vaccine to induce protective immunity in a mouse model. Methods: Female BALB/c mice divided into five groups were immunized with excretorys-ecretory antigens (ESA) vaccine, alum-ESA vaccine, PRP-ESA vaccine, and alum-PRP ESA vaccine, as well as with phosphate buffered saline (PBS), as a negative control group. The immune responses were evaluated by lymphocyte proliferation assay for measuring delayedtype hypersensitivity (DTH) response and by cytokine assay for evaluating IFN-γ and IL-5 levels. The survival rate of mice in all groups was assessed during a three-week monitoring period after an intraperitoneal challenge with T. gondii tachyzoites. Results: The results showed that mice immunized with PRP, as an adjuvant, could secret a higher level of IFN-γ, which was significant in comparison to other groups. However, mice vaccinated with alum-precipitated ESA antigen had ability to produce an elevated level of IL-5 compared to other mouse groups (P ≤ 0.05). Moreover, alum-PRP co-administration together with ESA vaccine resulted in the longer survival of mice. Conclusion: The findings of this study revealed that the combination of alum-PRP adjuvants and ESA vaccine of T. gondii elicits both humoral and cellular immune responses, which are comparable to either alum or PRP alone.

An Exaggerated Immune Response in Female BALB/c Mice Controls Initial Toxoplasma gondii Multiplication but Increases Mortality and Morbidity Relative to Male Mice

Studies indicate that female mice are more susceptible to T. gondii infection, as defined by higher mortality rates in comparison to male mice. However, whether this is due to an inability to control initial parasite multiplication or due to detrimental effects of the immune system has not been determined. Therefore, the following studies were undertaken to determine the influence of sex on early parasite multiplication and the immune response during T. gondii infection and to correlate this with disease outcome. Early parasite replication was studied through applying an in vivo imaging system (IVIS) with luciferase expressing T. gondii. In parallel immunological events were studied by cytometric bead array to quantify key immunological mediators. The results confirmed the previous findings that female mice are more susceptible to acute infection, as determined by higher mortality rates and weight loss compared with males. However, conflicting with expectations, female mice had lower parasite burdens during the acute infection than male mice. Female mice also exhibited significantly increased production of Monocyte Chemoattractant Protein-1 (MCP-1), Interferon (IFN)-γ, and Tumour Necrosis Factor (TNF)-α than male mice. MCP-1 was found to be induced by T. gondii in a dose dependent manner suggesting that the observed increased levels detected in female mice was due to a host-mediated sex difference rather than due to parasite load. However, MCP-1 was not affected by physiological concentration of estrogen or testosterone, indicating that MCP-1 differences observed between the sexes in vivo are due to an as yet unidentified intermediary factor that in turn influences MCP-1 levels. These results suggest that a stronger immune response in female mice compared with male mice enhances their ability to control parasite replication but increases their morbidity and mortality.

Pathogen-mediated selection favours the maintenance of innate immunity gene polymorphism in a widespread wild ungulate

Toll-like receptors (TLR) play a central role in recognition and host frontline defence against a wide range of pathogens. A number of recent studies have shown that TLR genes (Tlrs) often exhibit large polymorphism in natural populations. Yet, there is little knowledge on how this polymorphism is maintained and how it influences disease susceptibility in the wild. In previous work, we showed that some Tlrs exhibit similarly high levels of genetic diversity as genes of the Major Histocompatibility Complex (MHC), and signatures of contemporary balancing selection in roe deer (Capreolus capreolus), the most abundant cervid species in Europe. Here, we investigated the evolutionary mechanisms by which pathogen-mediated selection could shape this innate immunity genetic diversity by examining the relationships between Tlr (Tlr2, Tlr4 and Tlr5) genotypes (heterozygosity status and presence of specific alleles) and infections with Toxoplasma and Chlamydia, two widespread intracellular pathogens known to cause reproductive failure in ungulates. We showed that Toxoplasma and Chlamydia exposures vary significantly across years and landscape features with few co-infection events detected and that the two pathogens exert antagonistic selection on Tlr2 polymorphism. By contrast, we found limited support for Tlr heterozygote advantage. Our study confirmed the importance of looking beyond Mhc genes in wildlife immunogenetic studies. It also emphasized the necessity to consider multiple pathogen challenges and their spatiotemporal variation to improve our understanding of vertebrate defence evolution against pathogens.

Cyclooxygenase (COX)-2 modulates Toxoplasma gondii infection, immune response and lipid droplets formation in human trophoblast cells and villous explants

Congenital toxoplasmosis is represented by the transplacental passage of Toxoplasma gondii from the mother to the fetus. Our studies demonstrated that T. gondii developed mechanisms to evade of the host immune response, such as cyclooxygenase (COX)-2 and prostaglandin E2 (PGE2) induction, and these mediators can be produced/stored in lipid droplets (LDs). The aim of this study was to evaluate the role of COX-2 and LDs during T. gondii infection in human trophoblast cells and villous explants. Our data demonstrated that COX-2 inhibitors decreased T. gondii replication in trophoblast cells and villous. In BeWo cells, the COX-2 inhibitors induced an increase of pro-inflammatory cytokines (IL-6 and MIF), and a decrease in anti-inflammatory cytokines (IL-4 and IL-10). In HTR-8/SVneo cells, the COX-2 inhibitors induced an increase of IL-6 and nitrite and decreased IL-4 and TGF-β1. In villous explants, the COX-2 inhibitors increased MIF and decreased TNF-α and IL-10. Furthermore, T. gondii induced an increase in LDs in BeWo and HTR-8/SVneo, but COX-2 inhibitors reduced LDs in both cells type. We highlighted that COX-2 is a key factor to T. gondii proliferation in human trophoblast cells, since its inhibition induced a pro-inflammatory response capable of controlling parasitism and leading to a decrease in the availability of LDs, which are essentials for parasite growth.

Toxoplasma gondii: A possible etiologic agent for Alzheimer's disease

Toxoplasma gondii (T. gondii) is one of the most pervasive neurotropic pathogens causing different lesions in a wide variety of mammals as intermediate hosts, including humans. It is estimated that one-third of the world population is infected with T. gondii; however, for a long time, there has been much interest in the examination of the possible role of this parasite in the development of mental disorders, such as Alzheimer's disease (AD). T. gondii may play a role in the progression of AD using mechanisms, such as the induction of the host's immune responses, inflammation of the central nervous system (CNS), alteration in the levels of neurotransmitters, and activation of indoleamine-2,3-dyoxigenase. This paper presents an appraisal of the literature, reports, and studies that seek to the possible role of T. gondii in the development of AD. For achieving the purpose of the current study, a search of six English databases (PubMed, ScienceDirect, Web of Science, Scopus, ProQuest, and Google Scholar) was performed. The results support the involvement of T. gondii in the induction and development of AD. Indeed, T. gondii can be considered a risk factor for the development of AD and requires the special attention of specialists and patients. Furthermore, the results of this study may contribute to prevent or delay the progress of AD worldwide. Therefore, it is required to carry out further studies in order to better perceive the parasitic mechanisms in the progression of AD.

Early immune responses and parasite tissue distribution in mice experimentally infected with oocysts of either archetypal or non-archetypal genotypes of Toxoplasma gondii

In most of the world Toxoplasma gondii is comprised of archetypal types (types I, II and III); however, South America displays several non-archetypal strains. This study used an experimental mouse model to characterize the immune response and parasite kinetics following infection with different parasite genotypes. An oral inoculation of 50 oocysts per mouse from T. gondii M4 type II (archetypal, avirulent), BrI or BrIII (non-archetypal, virulent and intermediate virulent, respectively) for groups (G)2, G3 and G4, respectively was used. The levels of mRNA expression of cytokines, immune compounds, cell surface markers and receptor adapters [interferon gamma (IFNγ), interleukin (IL)-12, CD8, CD4, CD25, CXCR3 and MyD88] were quantified by SYBR green reverse transcription-quantitative polymerase chain reaction. Lesions were characterized by histology and detection by immunohistochemistry established distribution of parasites. Infection in G2 mice was mild and characterized by an early MyD88-dependent pathway. In G3, there were high levels of expression of pro-inflammatory cytokines IFNγ and IL-12 in the mice showing severe clinical symptoms at 8–11 days post infection (dpi), combined with the upregulation of CD25, abundant tachyzoites and tissue lesions in livers, lungs and intestines. Significant longer expression of IFNγ and IL-12 genes, with other Th1-balanced immune responses, such as increased levels of CXCR3 and MyD88 in G4, resulted in survival of mice and chronic toxoplasmosis, with the occurrence of tissue cysts in brain and lungs, at 14 and 21 dpi. Different immune responses and kinetics of gene expression appear to be elicited by the different strains and non-archetypal parasites demonstrated higher virulence.

Imbalance of uterine innate lymphoid cells is involved in the abnormal pregnancy induced by Toxoplasma gondii infection

Toxoplasma gondii (T. gondii) is a ubiquitous intracellular protozoan parasite that causes adverse pregnancy outcomes. Innate lymphoid cells (ILCs) are critical mediators of mucosal immunity, and have been reported to play an important role in uterine vascular adaptation for successful pregnancy. However, the specific role of ILCs in T. gondii-infection-induced adverse pregnancy outcomes remains elusive. In the present study, we found that T. gondii infection caused the imbalance of uterine ILC cells (uILCs). It was characterized by substantially lower expression of the transcription factor GATA-3 and RORγt and higher expression of T-bet in uILCs. Consistent with the transcription factor changes, uILCs from T. gondii-infected mice produced much less IL-5 and IL-17 and substantially more IFN-γ and TNF-α than did uILCs from uninfected mice. Notably, IL-12, IL-18, and their receptors were increased in the uterus of T. gondii-infected mice. In vitro experiments showed that IL-12 and IL-18 treatment reduced the percentages of uILC2 and uILC3 and increased the percentages of uILC1. Conclusion, our data suggest that alterations in uILC composition may disrupt the balance of immune microenvironment after T. gondii infection and contribute to the adverse pregnancy outcomes caused by T. gondii infection.

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.

Toxoplasma gondii, Suicidal Behavior, and Intermediate Phenotypes for Suicidal Behavior

Within the general literature on infections and suicidal behavior, studies on Toxoplasma gondii (T. gondii) occupy a central position. This is related to the parasite's neurotropism, high prevalence of chronic infection, as well as specific and non-specific behavioral alterations in rodents that lead to increased risk taking, which are recapitulated in humans by T. gondii's associations with suicidal behavior, as well as trait impulsivity and aggression, mental illness and traffic accidents. This paper is a detailed review of the associations between T. gondii serology and suicidal behavior, a field of study that started 15 years ago with our publication of associations between T. gondii IgG serology and suicidal behavior in persons with mood disorders. This "legacy" article presents, chronologically, our primary studies in individuals with mood disorders and schizophrenia in Germany, recent attempters in Sweden, and in a large cohort of mothers in Denmark. Then, it reviews findings from all three meta-analyses published to date, confirming our reported associations and overall consistent in effect size [ranging between 39 and 57% elevation of odds of suicide attempt in T. gondii immunoglobulin (IgG) positives]. Finally, the article introduces certain links between T. gondii and biomarkers previously associated with suicidal behavior (kynurenines, phenylalanine/tyrosine), intermediate phenotypes of suicidal behavior (impulsivity, aggression) and state-dependent suicide risk factors (hopelessness/dysphoria, sleep impairment). In sum, an abundance of evidence supports a positive link between suicide attempts (but not suicidal ideation) and T. gondii IgG (but not IgM) seropositivity and serointensity. Trait impulsivity and aggression, endophenotypes of suicidal behavior have also been positively associated with T. gondii seropositivity in both the psychiatrically healthy as well as in patients with Intermittent Explosive Disorder. Yet, causality has not been demonstrated. Thus, randomized interventional studies are necessary to advance causal inferences and, if causality is confirmed, to provide hope that an etiological treatment for a distinct subgroup of individuals at an increased risk for suicide could emerge.

Toxoplasma gondii infection as a potential risk for chronic liver diseases: A systematic review and meta-analysis

Toxoplasma gondii, the etiological agent of toxoplasmosis, can cause serious public health problems. Although Toxoplasma gondii tends more to neurotropic and ocular organs, some existing evidence suggest that this disease might induce serious pathological effects on liver. Hence, this study aimed to evaluate the relationship between chronic liver diseases and toxoplasmosis. Meanwhile, it attempted to assess whether patients with toxoplasmosis are susceptible to chronic liver diseases. To achieve this aim, the published studies related to the subject were systematically searched in five major electronic databases between the January 1, 1950 and October 1, 2019. The meta-analysis was carried out using the StatsDirect statistical software and a p-value less than 0.05 was considered significant for any test. Out of 691 identified studies, 10 studies met our inclusion criteria and entered this systematic review. The pooled prevalence rates of Toxoplasma gondii in patients with liver diseases (35.97%; 95% CI: 28.38-43.93) were higher than those in the control group (18.24%; 95% CI: 13.85-23.09). The meta-analysis indicated that the common Odd Ratio by a random effect model was 2.7 (95% CI: 2.30-3.24), revealing a significant association between chronic liver diseases and anti-Toxoplasma IgG antibody. The results of this systematic review confirmed the positive connection between toxoplasmosis and chronic liver diseases. Nonetheless, more studies are needed to clarify the detailed association between these diseases.

Seropositivity for pathogens associated with chronic infections is a risk factor for all-cause mortality in the elderly: findings from the Memory and Morbidity in Augsburg Elderly (MEMO) Study

Immunostimulation by chronic infection has been linked to an increased risk for different non-communicable diseases, which in turn are leading causes of death in high- and middle-income countries. Thus, we investigated if a positive serostatus for pathogens responsible for common chronic infections is individually or synergistically related to reduced overall survival in community dwelling elderly. We used data of 365 individuals from the German MEMO (Memory and Morbidity in Augsburg Elderly) cohort study with a median age of 73 years at baseline and a median follow-up of 14 years. We examined the effect of a positive serostatus at baseline for selected pathogens associated with chronic infections (Helicobacter pylori, Borrelia burgdorferi sensu lato, Toxoplasma gondii, cytomegalovirus, Epstein-Barr virus, herpes simplex virus 1/2, and human herpesvirus 6) on all-cause mortality with multivariable parametric survival models. We found a reduced survival time in individuals with a positive serostatus for Helicobacter pylori (accelerated failure time (AFT) - 15.92, 95% CI - 29.96; - 1.88), cytomegalovirus (AFT - 22.81, 95% CI - 36.41; - 9.22) and Borrelia burgdorferi sensu lato (AFT - 25.25, 95% CI - 43.40; - 7.10), after adjusting for potential confounders. The number of infectious agents an individual was seropositive for had a linear effect on all-cause mortality (AFT per additional infection - 12.42 95% CI - 18.55; - 6.30). Our results suggest an effect of seropositivity for Helicobacter pylori, cytomegalovirus, and Borrelia burgdorferi sensu lato on all-cause mortality in older community dwelling individuals. Further research with larger cohorts and additional biomarkers is required, to assess mediators and molecular pathways of this effect.

Evolutionary puzzle of Toxoplasma gondii with suicidal ideation and suicide attempts: An updated systematic review and meta-analysis

The World Health Organization has reported an annual global suicide rate of 14.5 per 100,000 people. On the other hand, it is estimated that approximately one-third of the global population are infected with Toxoplasma gondii (T. gondii) parasite. It is widely assumed that microbial pathogens, such as T. gondii, are probably associated with affective and behavioural modulation. The present article aimed to assess the proposed role of toxoplasmosis in raising the risk of suicidal ideation (SI) and suicide attempts (SA) using the available epidemiological data. Seven major electronic databases and the Internet search engine Google were searched for all the studies published between the 1st of January 1950 and 31st of October 2019. The heterogeneity and the risk of bias within and across studies were assessed. Following data extraction, pooled odds ratios (ORs) with 95% confidence interval (CI) across studies were calculated using the random-effects models. A total number of 9,696 articles were screened and 27 studies were regarded as eligible in our systematic review (SI with five papers and 22 papers on SA). A significant association was detected between antibodies against T. gondii with TA (ORs = 1.57; 95% confidence interval [CI] 1.23-2.00, p = .000). Exploration of the association between T. gondii and SA yielded a positive effect of seropositivity for IgG antibodies but not IgM. Despite the limited number of studies, a statistical association was detected between suicidal behaviours and infection with latent T. gondii.

Latent infection, inflammatory markers and suicide attempt history in depressive disorders

BACKGROUND

Numerous reports have described increased rates of exposure to Toxoplasma gondii levels in individuals with a history of suicide attempts in comparison with well controls, or psychiatrically ill individuals, with no suicide attempt history. Such findings suggest that the behavioral effects this parasite exerts on rodent hosts extends to humans though few studies have searched for underlying mechanisms.

METHODS

The present study compared 96 patients with an active depressive disorder and a history of at least two suicide attempts to 126 depressed patients with no history of suicide attempts by IgG and IgM levels of Toxoplasma gondii and cytomegalovirus (CMV). The groups were also compared by IL_1b, TNF-alpha, CRP, IL_6, and IL_1ra titers.

RESULTS

Toxoplasma gondii IgM levels were higher, and seropositivity more likely, in the suicide attempt group. CMV IgG levels were also higher among suicide attempters. Several of these immunoglobulin measures were more robustly associated with the number of suicide attempts than with the dichotomy of suicide attempter and non-attempter. These two antibody levels were also additive in their association with suicide attempter status. IL_1a levels were lower in suicide attempters and correlated negatively with levels of antibodies to Toxoplasma gondii and CMV.

LIMITATIONS

These include a sample size insufficient to explore differences across mood disorder diagnoses or demographic groupings.

CONCLUSIONS

These results indicate that exposure to common infectious agents such as Toxoplasma gondii and CMV are associated with increased risk of suicide attempts but the mechanism of association does not appear to involve the activation of cytokines. Elucidation of the mechanisms which define the relationship between infections and suicide attempts may lead to new methods for the prediction and prevention of suicide attempts.

Association of T. gondii infection with suicide: a systematic review and meta-analysis

BACKGROUND

Findings on the association between Toxoplasma gondii (T. gondii) infection and suicide are contradictory. This paper aimed to resolve this uncertainty by conducting a meta-analysis.

METHODS

We found the relevant studies using keywords include "Toxoplasmosis" and "Suicide" and the related synonyms in international databases such as ISI, Medline, and Scopus. The eligible studies were included in the meta-analysis phase. The random effect approach was applied to combine the results.

RESULTS

Out Of 150 initial studies, 15 were included in the meta-analysis. Odds of suicide in people with T. gondii infection was 43% (OR: 1.43, 95%CI; 1.15 to 1.78) higher than those without this infection. The test for publication bias was not statistically significant, which indicates the absence of likely publication bias.

CONCLUSION

This study confirms that T. gondii infection is a potential risk factor for suicide. To reduce cases of suicide attributable to T. gondii infection, it is recommended to implement some measures to prevent and control the transmission of the disease.

Immunobiotic and Paraprobiotic Potential Effect of Lactobacillus casei in a Systemic Toxoplasmosis Murine Model

One of the main characteristics of probiotics is their ability to stimulate and modulate the immune response regardless of their viability. Lactobacillus casei (Lc) can stimulate local and systemic immunity, in addition to the activation of macrophages at sites distant from the intestine. Activated macrophages limit the replication of intracellular protozoa, such as Toxoplasma gondii, through the production of nitric oxide. The present study aimed to evaluate the protection generated by treatment with viable and non-viable Lc in the murine systemic toxoplasmosis model. CD1 male mice were treated with viable Lc (immunobiotic) and non-viable Lc (paraprobiotic), infected with tachyzoites of Toxoplasma gondii RH strain. The reduction of the parasitic load, activation of peritoneal macrophages, inflammatory cytokines, and cell populations was evaluated at 7 days post-infection, in addition to the survival. The immunobiotic and paraprobiotic reduced the parasitic load, but only the immunobiotic increased the activation of peritoneal macrophages, and the production of interferon-gamma (IFN-γ), tumor necrosis factor (TNF), and interleukin-6 (IL-6) while the paraprobiotic increased the production of monocyte chemoattractant protein-1 (MCP-1) and T CD4⁺CD44⁺ lymphocytes. Viable and non-viable Lc increases survival but does not prevent the death of animals. The results provide evidence about the remote immunological stimulation of viable and non-viable Lc in an in vivo parasitic model.

Toxoplasma gondii infection reduces serum progesterone levels and adverse effects at the maternal-foetal interface

AIMS

Pregnant BALB/c mice infected with a Toxoplasma gondii type II strain were used to determine how pregnancy interferes with the development of maternal immunity to T gondii and how infection disrupts pregnancy and foetal development.

METHODS

Maternal and foetal parasite loads were assessed by amplification of T gondii SAG1 using qPCR. Adverse effects of infection were evaluated on foetal-placental development by quantification of implantation units undergoing resorption and by histopathological analyses. Serum progesterone levels were quantified by immunoassay. The effect of T gondii infection on maternal immunity was determined by assessing the cellular composition of spleens by flow cytometry.

RESULTS

Infected pregnant mice exhibited clinical signs of infection, inflammation and necrosis at the maternal-foetal interface and decreased serum progesterone levels. In infected mice, there was a clear effect of pregnancy and infection on macrophage cell numbers. However, no differences in the parasite load were detected between non-pregnant and pregnant mice.

CONCLUSIONS

Maternal T gondii infection induced adverse effects at the maternal-foetal interface. Alterations were found in immune spleen cells, dependent on the day of pregnancy, relative to nonpregnant animals. The results obtained suggest a pregnancy-dependent mechanism during T gondii infection able to interfere with macrophage numbers.

Association of Suicide Attempt With Seroprevalence of Toxoplasma gondii in Adolescents

In this study, we aimed to explore the potential pathophysiological relationship between suicide attempts and Toxoplasma gondii infection. Fifty patients aged between 12 and 18 years who attempted suicide and 50 healthy adolescents were included in this study. All adolescents were evaluated by a child psychiatrist using a semistructured interview and Rosenberg Self-Esteem Scale (RSES), Children's Depression Inventory (CDI), and Inventory of Parent and Peer Attachment. T. gondii IgM and IgG antibodies of patients and control subjects were analyzed from blood samples by enzyme-linked immunosorbent assay. Psychiatric disorders particularly mood disorders were more common in adolescents in the patient group. Adolescents attempting suicide were found to have worse relationships with their parents; their CDI scores were higher, and their RSES scores were lower than their healthy peers. There were no significant differences between the patient and the control groups in terms of Toxoplasma IgG antibody positivity. Although the seropositivity of Toxoplasma IgG antibody was higher in the patient group than that in the control group, the difference between the two groups was not statistically significant.

Toxoplasma gondii induces extracellular traps release in cat neutrophils

Neutrophils respond differently to violations of the body's physiological barriers during infections. Extracellular traps comprise one of the mechanisms used by these cells to reduce the spread of pathogens to neighboring tissues, as well as ensure a high concentration of antimicrobial agents at the site of infection. To date, this innate defense mechanism has not been previously demonstrated in neutrophils of cats exposed to Toxoplasma gondii. The aim of this study was to characterize the in vitro release of neutrophil extracellular traps (NETs) when neutrophils isolated from cats were exposed to T. gondii. First, cellular viability was tested at different time points after parasite exposure. The production of reactive oxygen species (ROS) and lactate dehydrogenase and the amount of extracellular DNA were quantified. In addition, the number of parasites associated with neutrophils was determined, and the observed NETs formed were microscopically characterized. Results showed that (i) in culture, neutrophils isolated from cats presented diminished cellular viability after 4 h of incubation, and when neutrophils were incubated with T. gondii, they displayed cytotoxic effects after 3 h of interaction; (ii) neutrophils were able to release structures composed of DNA and histones, characterized as NETs under optical, immunofluorescence, and electron scanning microscopy, when stimulated with T. gondii; (iii) only 11.4% of neutrophils were able to discharge NETs during 3 h of incubation; however, it was observed through extracellular quantification of DNA that this small number of cells were able to display different behavior compared to a negative control (no parasite) group; (iv) significant differences in ROS production were observed in neutrophils exposed to T. gondii. In conclusion, our results showed that neutrophils isolated from cats exposed to T. gondii release structures composed of DNA and histones, similar to what has already been described in other neutrophil species infected with the parasite.

Detection of Humoral and Cellular Immune Responses in Buffaloes Naturally Infected with Sarcocystosis with Risk Factor Assessment

Sarcocystosis is a silent, parasitic disease which affects various animal species and causes significant economic losses. It is caused by a number of different intracellular Sarcocystis spp. This study was aimed to detect the host humoral and cellular immune response due to natural infection. Adding to the determination of the infection rate in Monufia Governorate, Egypt. A total number of 127 Egyptian buffaloes (Bubalus bubalis); 30 males and 97 females between 2-11 years of age were examined during 2018. An infection rate of 74% (94/127) was detected by macroscopic examination. The old age females were found to be at a high risk of 90.7% (88/97) in comparison with the young males 20% (6/30). Immunologically, the cellular and humoral immune response was determined using ELISA. A marked down-regulation of the proinflammatory Th-1 cytokine (IFN-γ) and up-regulation of the anti-inflammatory Th-2 cytokine (IL-5) adding to a high level of IgG and IgE were detected in the infected animals compared to the non infected ones. The local cellular immune response in the infected tissues was characterized by an accumulation of mixed inflammatory cells, granuloma formation, eosinophilic infiltration, muscular edema, and necrotic degeneration. In conclusion, the Sarcocystis infection rate in the naturally infected buffaloes in Monufia Governorate was high. This is the first study to provide a fundamental insight into the immune profile in buffaloes infected with Sarcocystis spp. So, it will provide valuable insights to develop novel effective vaccines in future studies. Moreover, sensitive and specific tools should be established for the accurate diagnosis of this disease in the different Egyptian governorates through well-structured serological surveys.

Toxoplasma gondii activates a Syk-CARD9-NF-κB signaling axis and gasdermin D-independent release of IL-1β during infection of primary human monocytes

IL-1β is a potent pro-inflammatory cytokine that promotes immunity and host defense, and its dysregulation is associated with immune pathology. Toxoplasma gondii infection of myeloid cells triggers the production and release of IL-1β; however, the mechanisms regulating this pathway, particularly in human immune cells, are incompletely understood. We have identified a novel pathway of T. gondii induction of IL-1β via a Syk-CARD9-NF-κB signaling axis in primary human peripheral blood monocytes. Syk was rapidly phosphorylated during T. gondii infection of primary monocytes, and inhibiting Syk with the pharmacological inhibitors R406 or entospletinib, or genetic ablation of Syk in THP-1 cells, reduced IL-1β release. Inhibition of Syk in primary cells or deletion of Syk in THP-1 cells decreased parasite-induced IL-1β transcripts and the production of pro-IL-1β. Furthermore, inhibition of PKCδ, CARD9/MALT-1 and IKK reduced p65 phosphorylation and pro-IL-1β production in T. gondii-infected primary monocytes, and genetic knockout of PKCδ or CARD9 in THP-1 cells also reduced pro-IL-1β protein levels and IL-1β release during T. gondii infection, indicating that Syk functions upstream of this NF-κB-dependent signaling pathway for IL-1β transcriptional activation. IL-1β release from T. gondii-infected primary human monocytes required the NLRP3-caspase-1 inflammasome, but interestingly, was independent of gasdermin D (GSDMD) cleavage and pyroptosis. Moreover, GSDMD knockout THP-1 cells released comparable amounts of IL-1β to wild-type THP-1 cells after T. gondii infection. Taken together, our data indicate that T. gondii induces a Syk-CARD9/MALT-1-NF-κB signaling pathway and activation of the NLRP3 inflammasome for the release of IL-1β in a cell death- and GSDMD-independent manner. This research expands our understanding of the molecular basis for human innate immune regulation of inflammation and host defense during parasite infection.

Driving us mad: the association of Toxoplasma gondii with suicide attempts and traffic accidents - a systematic review and meta-analysis

Unnatural causes of death due to traffic accidents (TA) and suicide attempts (SA) constitute a major burden on global health, which remained stable in the last decade despite widespread efforts of prevention. Recently, latent infection with Toxoplasma gondii (T. gondii) has been suggested to be a biological risk factor for both TA and SA. Therefore, a systematic search concerning the relationship of T. gondii infection with TA and/or SA according to PRISMA guidelines in Medline, Pubmed and PsychInfo was conducted collecting papers up to 11 February 2019 (PROSPERO #CRD42018090206). The random-effect model was applied and sensitivity analyses were subsequently performed. Lastly, the population attributable fraction (PAF) was calculated. We found a significant association for antibodies against T. gondii with TA [odds ratio (OR) = 1.69; 95% confidence interval (CI) 1.20-2.38, p = 0.003] and SA (OR = 1.39; 95% CI 1.10-1.76, p = 0006). Indication of publication bias was found for TA, but statistical adjustment for this bias did not change the OR. Heterogeneity between studies on SA was partly explained by type of control population used (ORhealthy controls = 1.9, p &lt; 0.001 v. ORpsychiatric controls = 1.06, p = 0.87) and whether subjects with schizophrenia only were analysed (ORschizophrenia = 0.87, p = 0.62 v. ORvarious = 1.8, p &lt; 0.001). The association was significantly stronger with higher antibody titres in TA and in studies that did not focus on schizophrenia subjects concerning SA. PAF of a T. gondii infection was 17% for TA and 10% for SA. This indicates that preventing T. gondii infection may play a role in the prevention of TA or SA, although uncertainty remains whether infection and outcome are truly causally related.

In vitro therapeutic effect of Hemiscorpius lepturus venom on tachyzoites of Toxoplasma gondii

Pyrimethamine which is a main anti-Toxoplasma gondii drug has a serious side and toxic effects on the host. Accordingly, the development of new treatment options for toxoplasmosis with less toxic effects, low teratogenicity and parasiticidal effect against the various stage of T. gondii are dramatically crucial. Currently, natural molecules from scorpion and snake venoms are widely used as an alternative treatment against human disease, these compounds considered to be safe and to have low toxicity in comparison with synthetic drugs. Therefore, the goal of our study was to investigate the anti-Toxoplasma gondii activities of Hemiscorpius lepturus venom. We measured cytotoxicity of H. lepturus whole venom on Vero cells as well as effectiveness of this compound on viability of T. gondii applying colorimetric assay, according to mitochondrial oxidation of the MTT reagent (Methylthiazol tetrazolium 98%). The results of this study indicated that the H. lepturus whole venom has an anti-Toxoplasma effects with less toxic effect on Vero cells. Also, the T. gondii tachyzoites were treated with H. lepturus venom reached better results in comparison with Pyrimethamine-treated group. This research will serve as a base for future studies on toxoplasmosis and suggest a role for scorpion venom in promoting natural drugs.

GRA24-Based DNA Vaccine Prolongs Survival in Mice Challenged With a Virulent Toxoplasma gondii Strain

Toxoplasma gondii causes infections in a wide range of intermediate hosts and remains a threatening disease worldwide because of the lack of effective drugs and vaccines. Dense granule protein 24 (GRA24) is a novel essential virulence factor that is transferred into the nucleus of host cells from the parasitophorous vacuole to regulate gene expression. In the present study, bioinformatic analysis showed that GRA24 had a high score for B-cell and T-cell epitopes compared with surface antigen 1 (SAG1), which has been studied as a promising vaccine candidate. As a DNA vaccine, pVAX1-GRA24 was injected intramuscularly into BALB/c mice and the induced immune response was evaluated. pVAX1-GRA24 induced high levels of a mixed Th1/Th2 cytokines at 6 weeks after immunization. Antibody determinations, cytokines [interferon gamma (IFN-γ), interleukin (IL)-12, IL-4, IL-10], antigen-specific lymphocyte proliferation, CD4+ and CD8+ T lymphocytes, and cytotoxic T lymphocyte activity showed that mice immunized with pVAX1-GRA24 produced specific humoral and cellular immune responses. The expression levels of interferon regulatory factor 8 (IRF8), nuclear factor kappa B (NF-κB), and T-Box 21 (T-bet) were significantly higher in the pVAX1-GRA24 immunization group than in the control groups. Survival times were prolonged significantly (24.6 ± 5.5 days) in the mice immunized with pVAX1-GRA24 compared with the mice in the control groups, which died within 7 days of T. gondii challenge (p < 0.05). The results of the present study showed that pVAX1-GRA24 induced a T. gondii-specific immune response and thus represents a promising candidate vaccine to treat toxoplasmosis.

An experimental genetically attenuated live vaccine to prevent transmission of Toxoplasma gondii by cats

Almost any warm-blooded creature can be an intermediate host for Toxoplasma gondii. However, sexual reproduction of T. gondii occurs only in felids, wherein fertilisation of haploid macrogametes by haploid microgametes, results in diploid zygotes, around which a protective wall develops, forming unsporulated oocysts. Unsporulated oocysts are shed in the faeces of cats and meiosis gives rise to haploid sporozoites within the oocysts. These, now infectious, sporulated oocysts contaminate the environment as a source of infection for people and their livestock. RNA-Seq analysis of cat enteric stages of T. gondii uncovered genes expressed uniquely in microgametes and macrogametes. A CRISPR/Cas9 strategy was used to create a T. gondii strain that exhibits defective fertilisation, decreased fecundity and generates oocysts that fail to produce sporozoites. Inoculation of cats with this engineered parasite strain totally prevented oocyst excretion following infection with wild-type T. gondii, demonstrating that this mutant is an attenuated, live, transmission-blocking vaccine.