The opposing effect of acute and chronic Toxoplasma gondii infection on tumor development.

BACKGROUND: The interplay between Toxoplasma gondii infection and tumor development is intriguing and not yet fully understood. Some studies showed that T. gondii reversed tumor immune suppression, while some reported the opposite, stating that T. gondii infection promoted tumor growth. METHODS: We created three mouse models to investigate the interplay between T. gondii and tumor. Model I aimed to study the effect of tumor growth on T. gondii infection by measuring cyst number and size. Models II and III were used to investigate the effect of different stages of T. gondii infection on tumor development via flow cytometry and bioluminescent imaging. Mouse strains (Kunming, BALB/c, and C57BL/6J) with varying susceptibilities to tumors were used in the study. RESULTS: The size and number of brain cysts in the tumor-infected group were significantly higher, indicating that tumor presence promotes T. gondii growth in the brain. Acute T. gondii infection, before or after tumor cell introduction, decreased tumor growth manifested by reduced bioluminescent signal and tumor size and weight. In the tumor microenvironment, CD4+ and CD8+ T cell number, including their subpopulations (cytotoxic CD8+ T cells and Th1 cells) had a time-dependent increase in the group with acute T. gondii infection compared with the group without infection. However, in the peripheral blood, the increase of T cells, including cytotoxic CD8+ T cells and Th1 cells, persisted 25 days after Lewis lung carcinoma (LLC) cell injection in the group with acute T. gondii. Chronic T. gondii infection enhanced tumor growth as reflected by increase in tumor size and weight. The LLC group with chronic T. gondii infection exhibited decreased percentages of cytotoxic CD8+ T cells and Th1 cells 25 days post-LLC injection as compared with the LLC group without T. gondii infection. At week 4 post-LLC injection, chronic T. gondii infection increased tumor formation rate [odds ratio (OR) 1.71] in both KM and BALB/c mice. CONCLUSIONS: Our research elucidates the dynamics between T. gondii infection and tumorigenesis. Tumor-induced immune suppression promoted T. gondii replication in the brain. Acute and chronic T. gondii infection had opposing effects on tumor development.

Toxoplasma gondii chitinase-like protein TgCLP1 regulates the parasite cyst burden.

Toxoplasma, an important intracellular parasite of humans and animals, causes life-threatening toxoplasmosis in immunocompromised individuals. Although Toxoplasma secretory proteins during acute infection (tachyzoite, which divides rapidly and causes inflammation) have been extensively characterized, those involved in chronic infection (bradyzoite, which divides slowly and is surrounded by a cyst wall) remain uncertain. Regulation of the cyst wall is essential to the parasite life cycle, and polysaccharides, such as chitin, in the cyst wall are necessary to sustain latent infection. Toxoplasma secretory proteins during the bradyzoite stage may have important roles in regulating the cyst wall via polysaccharides. Here, we focused on characterizing the hypothetical T. gondii chitinase, chitinase-like protein 1 (TgCLP1). We found that the chitinase-like domain containing TgCLP1 is partially present in the bradyzoite microneme and confirmed, albeit partially, its previous identification in the tachyzoite microneme. Furthermore, although parasites lacking TgCLP1 could convert from tachyzoites to bradyzoites and make an intact cyst wall, they failed to convert from bradyzoites to tachyzoites, indicating that TgCLP1 is necessary for bradyzoite reactivation. Taken together, our findings deepen our understanding of the molecular basis of recrudescence and could contribute to the development of novel strategies for the control of toxoplasmosis.

Observing astrocyte polarization in brains from mouse chronically infected with Toxoplasma gondii.

Toxoplasma gondii (T. gondii) is a protozoan parasite that infects approximately one-third of the global human population, often leading to chronic infection. While acute T. gondii infection can cause neural damage in the central nervous system and result in toxoplasmic encephalitis, the consequences of T. gondii chronic infection (TCI) are generally asymptomatic. However, emerging evidence suggests that TCI may be linked to behavioral changes or mental disorders in hosts. Astrocyte polarization, particularly the A1 subtype associated with neuronal apoptosis, has been identified in various neurodegenerative diseases. Nevertheless, the role of astrocyte polarization in TCI still needs to be better understood. This study aimed to establish a mouse model of chronic TCI and examine the transcription and expression levels of glial fibrillary acidic protein (GFAP), C3, C1q, IL-1α, and TNF-α in the brain tissues of the mice. Quantitative real-time PCR (qRT-PCR), enzyme-linked immunosorbent assay, and Western blotting were employed to assess these levels. Additionally, the expression level of the A1 astrocyte-specific marker C3 was evaluated using indirect fluorescent assay (IFA). In mice with TCI, the transcriptional and expression levels of the inflammatory factors C1q, IL-1α, and TNF-α followed an up-down-up pattern, although they remained elevated compared to the control group. These findings suggest a potential association between astrocyte polarization towards the A1 subtype and synchronized changes in these three inflammatory mediators. Furthermore, immunofluorescence assay (IFA) revealed a significant increase in the A1 astrocytes (GFAP+C3+) proportion in TCI mice. This study provides evidence that TCI can induce astrocyte polarization, a biological process that may be influenced by changes in the levels of three inflammatory factors: C1q, IL-1α, and TNF-α. Additionally, the release of neurotoxic substances by A1 astrocytes may be associated with the development of TCI.

Fam96a is essential for the host control of Toxoplasma gondii infection by fine-tuning macrophage polarization via an iron-dependent mechanism.

BACKGROUND: Toxoplasmosis affects a quarter of the world's population. Toxoplasma gondii (T.gondii) is an intracellular parasitic protozoa. Macrophages are necessary for proliferation and spread of T.gondii by regulating immunity and metabolism. Family with sequence similarity 96A (Fam96a; formally named Ciao2a) is an evolutionarily conserved protein that is highly expressed in macrophages, but whether it play a role in control of T. gondii infection is unknown. METHODOLOGY/PRINCIPAL FINDINGS: In this study, we utilized myeloid cell-specific knockout mice to test its role in anti-T. gondii immunity. The results showed that myeloid cell-specific deletion of Fam96a led to exacerbate both acute and chronic toxoplasmosis after exposure to T. gondii. This was related to a defectively reprogrammed polarization in Fam96a-deficient macrophages inhibited the induction of immune effector molecules, including iNOS, by suppressing interferon/STAT1 signaling. Fam96a regulated macrophage polarization process was in part dependent on its ability to fine-tuning intracellular iron (Fe) homeostasis in response to inflammatory stimuli. In addition, Fam96a regulated the mitochondrial oxidative phosphorylation or related events that involved in control of T. gondii. CONCLUSIONS/SIGNIFICANCE: All these findings suggest that Fam96a ablation in macrophages disrupts iron homeostasis and inhibits immune effector molecules, which may aggravate both acute and chronic toxoplasmosis. It highlights that Fam96a may autonomously act as a critical gatekeeper of T. gondii control in macrophages.

Translation initiation factor eIF1.2 promotes Toxoplasma stage conversion by regulating levels of key differentiation factors.

The parasite Toxoplasma gondii persists in its hosts by converting from replicating tachyzoites to latent bradyzoites housed in tissue cysts. The molecular mechanisms that mediate T. gondii differentiation remain poorly understood. Through a mutagenesis screen, we identified translation initiation factor eIF1.2 as a critical factor for T. gondii differentiation. A F97L mutation in eIF1.2 or the genetic ablation of eIF1.2 (∆eif1.2) markedly impeded bradyzoite cyst formation in vitro and in vivo. We demonstrated, at single-molecule level, that the eIF1.2 F97L mutation impacts the scanning process of the ribosome preinitiation complex on a model mRNA. RNA sequencing and ribosome profiling experiments unveiled that ∆eif1.2 parasites are defective in upregulating bradyzoite induction factors BFD1 and BFD2 during stress-induced differentiation. Forced expression of BFD1 or BFD2 significantly restored differentiation in ∆eif1.2 parasites. Together, our findings suggest that eIF1.2 functions by regulating the translation of key differentiation factors necessary to establish chronic toxoplasmosis.

Single-cell transcriptomic analysis of decidual immune cell landscape in the occurrence of adverse pregnancy outcomes induced by Toxoplasma gondii infection.

BACKGROUND: Toxoplasma gondii is an obligate intracellular parasite that can lead to adverse pregnancy outcomes, particularly in early pregnancy. Previous studies have illustrated the landscape of decidual immune cells. However, the landscape of decidual immune cells in the maternal-fetal microenvironment during T. gondii infection remains unknown. METHODS: In this study, we employed single-cell RNA sequencing to analyze the changes in human decidual immune cells following T. gondii infection. The results of scRNA-seq were further validated with flow cytometry, reverse transcription-polymerase chain reaction, western blot, and immunofluorescence staining. RESULTS: Our results showed that the proportion of 17 decidual immune cell clusters and the expression levels of 21 genes were changed after T. gondii infection. Differential gene analysis demonstrated that T. gondii infection induced the differential expression of 279, 312, and 380 genes in decidual NK cells (dNK), decidual macrophages (dMφ), and decidual T cells (dT), respectively. Our results revealed for the first time that several previously unknown molecules in decidual immune cells changed following infection. This result revealed that the function of maternal-fetal immune tolerance declined, whereas the killing ability of decidual immune cells enhanced, eventually contributing to the occurrence of adverse pregnancy outcomes. CONCLUSIONS: This study provides valuable resource for uncovering several novel molecules that play an important role in the occurrence of abnormal pregnancy outcomes induced by T. gondii infection.

Phosphoproteomic analysis reveals changes in A-Raf-related protein phosphorylation in response to Toxoplasma gondii infection in porcine macrophages.

BACKGROUND: Toxoplasma gondii is an obligate intracellular protozoan parasite that causes severe threats to humans and livestock. Macrophages are the cell type preferentially infected by T. gondii in vivo. Protein phosphorylation is an important posttranslational modification involved in diverse cellular functions. A rapidly accelerated fibrosarcoma kinase (A-Raf) is a member of the Raf family of serine/threonine protein kinases that is necessary for MAPK activation. Our previous research found that knockout of A-Raf could reduce T. gondii-induced apoptosis in porcine alveolar macrophages (3D4/21 cells). However, limited information is available on protein phosphorylation variations and the role of A-Raf in macrophages infected with T. gondii. METHODS: We used immobilized metal affinity chromatography (IMAC) in combination with liquid chromatography tandem mass spectrometry (LC-MS/MS) to profile changes in phosphorylation in T. gondii-infected 3D4/21 and 3D4/21-ΔAraf cells. RESULTS: A total of 1647 differentially expressed phosphorylated proteins (DEPPs) with 3876 differentially phosphorylated sites (DPSs) were identified in T. gondii-infected 3D4/21 cells (p3T group) when compared with uninfected 3D4/21 cells (pho3 group), and 959 DEPPs with 1540 DPSs were identified in the p3T group compared with infected 3D4/21-ΔAraf cells (p3KT group). Venn analysis revealed 552 DPSs corresponding to 406 DEPPs with the same phosphorylated sites when comparing p3T/pho3 versus p3T/p3KT, which were identified as DPSs and DEPPs that were directly or indirectly related to A-Raf. CONCLUSIONS: Our results revealed distinct responses of macrophages to T. gondii infection and the potential roles of A-Raf in fighting infection via phosphorylation of crucial proteins.

Anti-Toxoplasma In Vitro and In Vivo Activity of Pyrus boissieriana Arbutin-Rich Fraction.

PURPOSE: Pyrus boissieriana is a rich source of arbutin and has been used in herbal medicine to treat infectious diseases. This study aimed to investigate the effect of the arbutin-rich fraction of Pyrus boissieriana aerial parts on Toxoplasma gondii In Vitro and In Vivo. METHODS: An arbutin-rich fraction of P. boissieriana was prepared beforehand. Flow cytometry was used to evaluate the effect of different concentrations (1-512 µg/ml) of the P. boissieriana arbutin-rich fraction on Toxoplasma tachyzoites (RH strain). The cytotoxicity of the concentrations on the macrophage J774 cell line was also investigated by MTT assay. For In Vivo investigation, 4-6-week-old female mice infected with the RH strain of T. gondii were treated with different doses (16, 32, 64, 256, and 512 mg/kg) of the fraction using gavage. RESULTS: The highest and lowest lethality of the tachyzoites were 89.6% and 25.9% related to the concentrations of 512 µg/ml and 1 µg/ml, respectively, with an IC50 value of 18.1 µg/ml ± 0.37. The cytotoxicity test showed an IC50 value of 984.3 µg/ml ± 0.76 after 48 h incubation. The mean survival of mice at the lowest treated dose (16 mg/kg) was 6.6 days, and it was 15 days at the highest dose (512 mg/kg). The concentrations of 512, 256, 128, and 64 mg/kg of the fraction compared to the negative control (6.2 days mean survival) significantly increased the survival time of mice (P < 0.001, P = 0.009, P = 0.018, and P = 0.021, respectively). CONCLUSION: The results showed that the arbutin-rich fraction of P. boissieriana is effective against T. gondii In Vitro and In Vivo and may be a reliable alternative to conventional treatment for toxoplasmosis, although further studies are necessary.

Aggravation of cognitive impairments in the valproic acid-induced animal model of autism in BALB/c mice infected with Toxoplasma gondii.

PURPOSE: Toxoplasmosis is a disease caused by infection with a type of coccidial protozoan parasite called Toxoplasma gondii. The relationship between toxoplasmosis and cognitive disorders in neurodegenerative diseases has been proven. There is also evidence that children born to Toxoplasma-infected mothers are more likely to develop autism. METHODS: In the present study, Toxoplasma-infected pregnant BALB/c mice were given valproic acid to induce autism in their male offspring, and their social behaviors, learning, and memory were examined. Chronic toxoplasmosis was established in BALB/c mice by intraperitoneal injection of cyst form of T. gondii. To induce autism, 600 mg/kg of valproic acid was injected intraperitoneally into mice on the 12.5th day of pregnancy. The behavioral experiments, such as social interaction, novel object recognition, and passive avoidance tasks, were performed on male offspring at 50 days. RESULTS: Toxoplasma and valproic acid during the embryonic period caused social communication deficits and disrupted recognition memory and avoidance memory in offspring. Our findings showed that administering valproic acid to Toxoplasma-infected mothers exacerbates cognitive disorders in their offspring.

Mitochondrial dysfunction induced by bedaquiline as an anti-Toxoplasma alternative.

Toxoplasma gondii is a zoonotic parasite that infects one-third of the world's population and nearly all warm-blooded animals. Due to the complexity of T. gondii's life cycle, available treatment options have limited efficacy. Thus, there is an urgent need to develop new compounds or repurpose existing drugs with potent anti-Toxoplasma activity. This study demonstrates that bedaquiline (BDQ), an FDA-approved diarylquinoline antimycobacterial drug for the treatment of tuberculosis, potently inhibits the tachyzoites of T. gondii. At a safe concentration, BDQ displayed a dose-dependent inhibition on T. gondii growth with a half-maximal effective concentration (EC50) of 4.95 µM. Treatment with BDQ significantly suppressed the proliferation of T. gondii tachyzoites in the host cell, while the invasion ability of the parasite was not affected. BDQ incubation shrunk the mitochondrial structure and decreased the mitochondrial membrane potential and ATP level of T. gondii parasites. In addition, BDQ induced elevated ROS and led to autophagy in the parasite. By transcriptomic analysis, we found that oxidative phosphorylation pathway genes were significantly disturbed by BDQ-treated parasites. More importantly, BDQ significantly reduces brain cysts for the chronically infected mice. These results suggest that BDQ has potent anti-T. gondii activity and may impair its mitochondrial function by affecting proton transport. This study provides bedaquiline as a potential alternative drug for the treatment of toxoplasmosis, and our findings may facilitate the development of new effective drugs for the treatment of toxoplasmosis.

Urtica dioica Extract Leads to Cyst Reduction, Enhanced Cell-Mediated Immune Response, and Antioxidant Activity in Experimental Toxoplasmosis.

BACKGROUND: Toxoplasmosis is a cosmopolitan parasitic infection caused by Toxoplasma gondii which is commonly treated by pyrimethamine (PYR) plus sulfadiazine (SDZ) with several adverse side effects. The present study evaluated the therapeutic effects of Urtica dioica L. aqueous extract (UDE) on acute and chronic toxoplasmosis in mice. METHODS: For this purpose, mice were infected with 20 cysts (acute infection) or 10 cysts (chronic infection) of T. gondii (Me49 strain). The mice were treated with 200 mg/kg of UDE intraperitoneally (IP) and intragastric route (IG). The UDE-treated mice were compared with the PYR + SDZ treatment. The histopathological changes, cyst count, total antioxidant capacity (TAC), malondialdehyde (MDA) assay, and serum INF-γ were also evaluated. RESULTS: In the acute toxoplasmosis, UDE by IP and IG administration significantly reduced the number of brain cysts by 93.74 and 92.55%, respectively, and increased the survival rate to 80% compared with 60% in untreated controls. In the chronic infection, cyst burden decreased at 88.2 and 83.4%, respectively, for IP and IG treatments. Moreover, UDE significantly increased INF- γ levels in acute and chronic toxoplasmosis. Tissue inflammatory lesions were reduced in the UDE-treated subgroups compared to the untreated group. UDE treatment significantly reduced MDA levels and elevated TAC in both acute and chronic infections. CONCLUSION: The results show that U. dioica possesses significant immunostimulant and antioxidant activity with a higher cyst reduction in the brain during acute toxoplasmosis. Further studies are required to investigate the fractionations of UDE against T. gondii and its combination with other standard drugs.

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

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

L-tryptophan-titanium oxide nanoparticles showed selective anti-Toxoplasma gondii activity and improved host biocompatibility.

Toxoplasma gondii, the etiological agent of toxoplasmosis, currently affects nearly one-third of the human population. Treatment options for toxoplasmosis are limited, which underscores the need for new drugs. In the present study, we screened nanoparticles (NPs) of titanium dioxide (TiO2) and molybdenum (Mo) for their potential to inhibit the growth of T. gondii in vitro. NPs of TiO2 and Mo showed non-dose-dependent anti-T. gondii activity with EC50 values of 157.6 and 253 µg/mL, respectively. Previously, we showed that amino acid modification of NPs enhances their selective anti-parasite toxicity. Therefore, to enhance the selective anti-parasitic action of TiO2, we modified the NP surface using alanine, aspartate, arginine, cysteine, glutamate, tryptophan, tyrosine, and bovine serum albumin. The bio-modified TiO2 showed anti-parasite activity with EC50 values ranging from 45.7 to 286.4 µg/mL. At effective anti-parasite concentrations, modified-TiO2 showed no appreciable host cytotoxicity. Of the eight bio-modified TiO2, tryptophan-TiO2 showed the most promising anti-T. gondii specificity and improved host biocompatibility with a selectivity index (SI) of 49.1 versus 7.5 for TiO2 (note, pyrimethamine, a standard drug for toxoplasmosis, has an SI of 2.3). Furthermore, our data indicate that redox modulation may be part of the anti-parasite action of these NPs. Indeed, augmentation with trolox and l-tryptophan reversed the growth restriction caused by the tryptophan-TiO2 NPs. Collectively, these findings suggest that the parasite toxicity was selective and not a result of general cytotoxic action. Furthermore, surface modification with amino acids such as l-tryptophan not only enhanced the anti-parasitic action of TiO2 but also improved the host biocompatibility. Overall, our findings indicate that the nutritional requirements of T. gondii represent a viable target for the development of new and effective anti-T. gondii agents.

Use of in vitro derived human neuronal models to study host-parasite interactions of Toxoplasma gondii in neurons and neuropathogenesis of chronic toxoplasmosis.

Toxoplasma gondii infects approximately one-third of the world's population resulting in a chronic infection with the parasite located in cysts in neurons in the brain. In most immunocompetent hosts the chronic infection is asymptomatic, but several studies have found correlations between Toxoplasma seropositivity and neuropsychiatric disorders, including Schizophrenia, and some other neurological disorders. Host-parasite interactions of bradyzoites in cysts in neurons is not well understood due in part to the lack of suitable in vitro human neuronal models. The advent of stem cell technologies in which human neurons can be derived in vitro from human induced pluripotent stem cells (hiPSCs) or direct conversion of somatic cells generating induced neurons (iNs), affords the opportunity to develop in vitro human neuronal culture systems to advance the understanding of T. gondii in human neurons. Human neurons derived from hiPSCs or iNs, generate pure human neuron monolayers that express differentiated neuronal characteristics. hiPSCs also generate 3D neuronal models that better recapitulate the cytoarchitecture of the human brain. In this review, an overview of iPSC-derived neurons and iN protocols leading to 2D human neuron cultures and hiPSC-derived 3D cerebral organoids will be given. The potential applications of these 2D and 3D human neuronal models to address questions about host-parasite interactions of T. gondii in neurons and the parasite in the CNS, will be discussed. These human neuronal in vitro models hold the promise to advance the understanding of T. gondii in human neurons and to improve the understanding of neuropathogenesis of chronic toxoplasmosis.

ß-Glucan alleviates goal-directed behavioral deficits in mice infected with Toxoplasma gondii.

BACKGROUND: Toxoplasma gondii (T. gondii) is a neuroinvasive parasite causing neuroinflammation, which in turn is associated with a higher risk for several psycho-behavioral disorders. There is an urgent need to identify drugs capable of improving cognitive deficits induced by T. gondii infection. ß-Glucan, an active ingredient in mushrooms, could significantly enhance immunity. However, the effects of ß-glucan against neuroinflammation and cognitive decline induced by T. gondii infection remain unknown. The present study aimed to investigate the neuroprotective effect of ß-glucan on goal-directed behavior of mice chronically infected by T. gondii Wh6 strain. METHODS: A mice model of chronic T. gondii Wh6 infection was established by infecting mice by oral gavage with 10 cysts of T. gondii Wh6. Intraperitoneal injection of ß-glucan was manipulated 2 weeks before T. gondii infection. Performance of the infected mice on the Y-maze test and temporal order memory (TOM) test was used to assess the goal-directed behavior. Golgi-Cox staining, transmission electron microscopy, immunofluorescence, real-time PCR and western blot assays were used to detect prefrontal cortex-associated pathological change and neuroinflammation. RESULTS: The administration of ß-glucan significantly prevented T. gondii Wh6-induced goal-directed behavioral impairment as assessed behaviorally by the Y-maze test and TOM test. In the prefrontal cortex, ß-glucan was able to counter T. gondii Wh6-induced degeneration of neurites, impairment of synaptic ultrastructure and decrease of pre- and postsynaptic protein levels. Also, ß-glucan significantly prevented the hyperactivation of pro-inflammatory microglia and astrocytes, as well as the upregulation of proinflammatory cytokines caused by chronic T. gondii Wh6 infection. CONCLUSIONS: This study revealed that ß-glucan prevents goal-directed behavioral impairment induced by chronic T. gondii infection in mice. These findings suggest that ß-glucan may be an effective drug candidate to prevent T. gondii-associated psycho-behavioral disorders including goal-directed behavioral injury.

Toxoplasma gondii vaccine candidates: a concise review.

Toxoplasma gondii is an obligate intracellular parasite that causes toxoplasmosis. It has been shown that the severity of symptoms depends on the functioning of the host immune system. Although T. gondii infection typically does not lead to severe disease in healthy people and after infection, it induces a stable immunity, but it can contribute to severe and even lethal Toxoplasmosis in immunocompromised individuals (AIDS, bone marrow transplant and neoplasia). The antigens that have been proposed to be used in vaccine candidate in various studies include surface antigens and secretory excretions that have been synthesized and evaluated in different studies. In some studies, secretory antigens play an important role in stimulating the host immune response. Various antigens such as SAG, GRA, ROP, ROM, and MAG have been from different strains of T. gondii have been synthesized and their protective effects have been evaluated in animal models in different vaccine platforms including recombinant antigens, nanoparticles, and DNA vaccine. Four bibliographic databases including Science Direct, PubMed Central (PMC), Scopus, and Google Scholar were searched for articles published up to 2020.The current review article focuses on recent studies on the use and usefulness of recombinant antigens, nanoparticles, and DNA vaccines.

Recombinant Mouse Prolactin Confers Partial Protection Against Toxoplasma gondii Infection in a Pre-treated Experimental Murine Model.

INTRODUCTION: Toxoplasmosis is one of the most important health-threatening diseases with worldwide distribution and global impact. It is caused by Toxoplasma gondii (T. gondii), an intracellular apicomplexan parasite that can evade the host immune responses and establish a chronic infection. The available treatments are not efficient against this stage and have many adverse effects. There are no available effective vaccines, apart from Toxovax®, which is used in sheep to prevent abortion. Studies documented that prolactin (PRL) had in vivo and in vitro anti-Toxoplasma effects. Detailed research was recommended about the mechanisms of such inhibitory effects. AIM: This study was designed to assess the possible protective role of the recombinant prolactin (rPRL) against T. gondii. MATERIALS AND METHODS: Sixty experimentally infected mice with T. gondii were used. The treated mice received rPRL for five days before infection. Serum prolactin levels were measured; survival rate was monitored; number, size, and DNA of T. gondii cysts in the brain were measured; and histopathological and immunological studies were done. RESULTS: There was a significant increase in the survival rate of the rPRL-treated mice, a significant decrease in the number, size, and DNA amount of T. gondii cysts in the brain with a noticeable improvement of histopathological lesions in the brain and liver tissues when compared to the infected untreated group. These effects seem to be achieved through stimulating humoral and cell-mediated immune responses that were evident by the significant rise in serum levels of anti-Toxoplasma IgM, IFN-γ, and TNF-α. CONCLUSION: The rPRL elicited robust immune responses, which provided efficient protection against murine T. gondii infection.

Presence of Toxoplasma gondii tissue cysts in human semen: Toxoplasmosis as a potential sexually transmissible infection.

OBJECTIVES: Toxoplasma gondii is a widely prevalent protozoan parasite in human populations. This parasite is thought to be primarily transmitted through undercooked meat and contamination by cat feces. Here, we seek to determine if Toxoplasma gondii cysts can be found within human semen. METHODS: We used a mixture of histological and immunofluorescence stains to visualize Toxoplasma gondii cysts in thin smears of human semen. Further, we probed for presence of bradyzoite-specific mRNA transcription using in-situ hybridization. RESULTS: We visualized Toxoplasma gondii cysts in ejaculates of immune-competent and latently infected human volunteers. We confirmed the encystment by probing transcription of a bradyzoite-specific gene in these structures. These observations extend previous observations of the parasite in semen of several non-human host species, including rats, dogs, and sheep. CONCLUSIONS: Toxoplasma gondii infection is a clinically significant infection, in view of its high prevalence, its purported role in neuropsychiatric disorders such as schizophrenia, as well as in the more serious form of congenital toxoplasmosis. Our demonstration of intact Toxoplasma gondii cysts in the ejaculate supports the possibility of sexual transmission of the parasite and provides an impetus for further investigations.

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

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

In Vitro and In Vivo Activities of Tilmicosin and Acetylisovaleryltylosin Tartrate against Toxoplasma gondii.

Toxoplasma gondii is a widespread intracellular pathogen that infects humans and a variety of animals. The current therapeutic strategy for human toxoplasmosis is a combination of sulphadiazine and pyrimethamine. However, this combination still has a high failure rate and is ineffective against chronic infections. Therefore, it is important to discover a new anti-T. gondii drug that is safer and more effective in both humans and animals. In this study, we describe the anti-T. gondii activities of the 16-membered macrolide tilmicosin and acetylisovaleryltylosin tartrate (ATLL). Both tilmicosin and ATLL potently inhibited T. gondii with a half-maximal effective concentration (EC50) of 17.96 µM and 10.67 µM, respectively. Interestingly, tilmicosin and ATLL had different effects on the parasites. ATLL exhibited a potent inhibitory effect on intracellular parasite growth, while tilmicosin suppressed parasites extracellularly. By studying the lytic cycle of T. gondii after treatment, we found that ATLL potently inhibited the intracellular proliferation of tachyzoites, while tilmicosin affected the invasion of tachyzoites. Immunofluorescence analysis using ATLL-treated T. gondii showed morphologically abnormal parasites, which may be due to the inhibition of tachyzoite proliferation and division. In addition, tilmicosin and ATLL significantly delayed the death of mice caused by acute toxoplasmosis. Our results suggest that ATLL has potent anti-Toxoplasma activity both in vitro and in vivo and may be an alternative to toxoplasmosis in the future.