Toxoplasma gondii is the causal agent of toxoplasmosis in which one third of the world's population has been infected. In pregnant women, it may cause abortion and severe damage to the fetal central nervous system. During pregnancy, the prevalence of toxoplasmosis increases throughout the second and third quarter of gestation, simultaneously progesterone and 17β-estradiol also increase. Thus, it has been suggested that these hormones can aggravate or reduce parasite reproduction. The aim of this study was reviewing the relationship between hormones and infection caused by T. gondii in several experimental animal models and humans, focused mainly on: (a) congenital transmission, (b) parasite reproduction, (c) strain virulence, (d) levels of hormone in host induced by T. gondii infection, and (e) participation of hormone receptors in T. gondii infection. Are the hormones specific modulators of T. gondii infection? A systematic review methodology was used to consult several databases (Pub Med, Lilacs, Medline, Science direct, Scielo, Ebsco, Sprinker, Wiley, and Google Scholar) dated from September, 2013 to March, 2014.
Thirty studies were included; eight studies in humans and 22 in animals and cell cultures. In the human studies, the most studied hormones were testosterone, progesterone, prolactin, and 17β-estradiol. Type I (RH and BK) and Type II (Prugniaud, SC, ME49, T45, P78, and T38) were the most frequent experimental strains.
Thirty-five years have passed since the first studies regarding T. gondii infection and its relationship with hormones. This systematic review suggests that hormones modulate T. gondii infection in different animal models. However, given that data were not comparable, further studies are required to determine the mechanism of hormone action in the T. gondii infectious process.
Toxoplasma; Toxoplasma infection; no steroid hormones; steroids hormones; toxoplasmosis
Toxoplasmosis, one of the most common zoonotic diseases worldwide, can induce various hormonal and behavioural alterations in infected hosts, and its most common form, latent toxoplasmosis, influences the course of pregnancy. Autoimmune thyroid diseases (AITD) belong to the well-defined risk factors for adverse pregnancy outcomes. The aim of this study was to investigate whether there is a link between latent toxoplasmosis and maternal AITD in pregnancy.
Cross-sectional study in 1248 consecutive pregnant women in the 9-12th gestational weeks. Serum thyroid-stimulating hormone (TSH), thyroperoxidase antibodies (TPOAb), and free thyroxine (FT4) were assessed by chemiluminescence; the Toxoplasma status was detected by the complement fixation test (CFT) and anti-Toxoplasma IgG enzyme-linked immunosorbent assay (ELISA).
Overall, 22.5% of the women were positive for latent toxoplasmosis and 14.7% were screened positive for AITD. Women with latent toxoplasmosis had more often highly elevated TPOAb than the Toxoplasma-negative ones (p = 0.004), and latent toxoplasmosis was associated with decrease in serum TSH levels (p = 0.049). Moreover, we found a positive correlation between FT4 and the index of positivity for anti-Toxoplasma IgG antibodies (p = 0.033), which was even stronger in the TPOAb-positive Toxoplasma-positive women, (p = 0.014), as well as a positive correlation between FT4 and log2 CFT (p = 0.009).
Latent toxoplasmosis was associated with a mild increase in thyroid hormone production in pregnancy. The observed Toxoplasma-associated changes in the parameters of AITD are mild and do not seem to be clinically relevant; however, they could provide new clues to the complex pathogenesis of autoimmune thyroid diseases.
Host cell invasion by Toxoplasma gondii and other apicomplexan parasites requires transmembrane adhesins that mediate binding to receptors on the substrate and host cell to facilitate motility and invasion. Rhomboid proteases (ROMs) are thought to cleave adhesins within their transmembrane segments, thus allowing the parasite to disengage from receptors and completely enter the host cell. To examine the specific roles of individual ROMs during invasion, we generated single, double, and triple knockouts for the three ROMs expressed in T. gondii tachyzoites. Analysis of these mutants demonstrated that ROM4 is the primary protease involved in adhesin processing and host cell invasion, whereas ROM1 or ROM5 plays negligible roles in these processes. Deletion of ROM4 blocked the shedding of adhesins such as MIC2 (microneme protein 2), causing them to accumulate on the surface of extracellular parasites. Increased surface adhesins led to nonproductive attachment, altered gliding motility, impaired moving junction formation, and reduced invasion efficiency. Despite the importance of ROM4 for efficient invasion, mutants lacking all three ROMs were viable and MIC2 was still efficiently removed from the surface of invaded mutant parasites, implying the existence of ROM-independent mechanisms for adhesin removal during invasion. Collectively, these results suggest that although ROM processing of adhesins is not absolutely essential, it is important for efficient host cell invasion by T. gondii.
Phosphoinositides regulate numerous cellular processes, by recruiting cytosolic effector proteins and acting as membrane signaling entities. The cellular metabolism and localization of phosphoinositides are tightly regulated by distinct lipid kinases and phosphatases. Here, we identify and characterize a unique phosphatidylinositol 3-Kinase (PI3K) in Toxoplasma gondii, a protozoan parasite belonging to the phylum Apicomplexa. Conditional depletion of this enzyme and subsequently of its product, PI(3)P, drastically alters the morphology and inheritance of the apicoplast, an endosymbiontic organelle of algal origin that is a unique feature of many Apicomplexa. We searched the T. gondii genome for PI(3)P binding proteins and identified in total six PX and FYVE-domain containing proteins including a PIKfyve lipid kinase, which phosphorylates PI(3)P into PI(3,5)P2 . While depletion of putative PI(3)P binding proteins shows that they are not essential for parasite growth and apicoplast biology, conditional disruption of PIKfyve induces enlarged apicoplasts, as observed upon the loss of PI(3)P. A similar defect of apicoplast homeostasis was also observed by knocking-down the PIKfyve regulatory protein ArPIKfyve, suggesting that in T. gondii, PI(3)P-related function for the apicoplast might mainly be to serve as a precursor for the synthesis of PI(3,5)P2 . Accordingly, PI3K is conserved in all apicomplexan parasites whereas PIKfyve and ArPIKfyve are absent in Cryptosporidium species which lack an apicoplast, supporting a direct role of PI(3,5)P2 in apicoplast homeostasis. This study enriches the already diverse functions attributed to PI(3,5)P2 in eukaryotic cells and highlights these parasite lipid kinases as potential drug targets.
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Lipid bodies [lipid droplets (LBs)] are lipid-rich organelles involved in lipid metabolism, signalling and inflammation. Recent findings suggest a role for LBs in host response to infection; however, the potential functions of this organelle in Toxoplasma gondii infection and how it alters macrophage microbicidal capacity during infection are not well understood. Here, we investigated the role of host LBs in T. gondii infection in mouse peritoneal macrophages in vitro. Macrophages cultured with mouse serum (MS) had higher numbers of LBs than those cultured in foetal bovine serum and can function as a model to study the role of LBs during intracellular pathogen infection. LBs were found in association with the parasitophorous vacuole, suggesting that T. gondii may benefit from this lipid source. Moreover, increased numbers of macrophage LBs correlated with high prostaglandin E2 (PGE2) production and decreased nitric oxide (NO) synthesis. Accordingly, LB-enriched macrophages cultured with MS were less efficient at controlling T. gondii growth. Treatment of macrophages cultured with MS with indomethacin, an inhibitor of PGE2 production, increased the microbicidal capacity against T. gondii. Collectively, these results suggest that culture with MS caused a decrease in microbicidal activity of macrophages against T. gondii by increasing PGE2 while lowering NO production.
Toxoplasmosis is a major cause of foodborne disease, congenital complication, and morbidity. There is an urgent need for safe and effective therapies to encounter congenital and persisting toxoplasmosis. The hypothesis was: combination diclazuril plus atovaquone to exert a novel therapeutic synergy to prevent toxoplasmosis syndromes.
Pregnant dams were treated with diclazuril and atovaquone monotherapy or combination therapy and infected i.p with Toxoplasma tachyzoites.
Infected dams developed severe toxoplasmosis associated syndrome with increases in the abdominal adiposity surrounding uteri, gansterointestinal and other internal organs and excessive weight gain. Numerous organisms along with infiltration of inflammatory cells were detected scattered into adipose tissues. Combination therapy (p < 0.01) and to a lesser extent diclazuril (p < 0.05) protected dams from inflammatory fat and excess weight gains. This was consistent with pancreatitis development in infected dams (versus normal p < 0.05) with infiltration of inflammatory cells, degeneration and necrosis of pancreatic cells followed by the degeneration and loss of islets. Combination and monotherapy protected dams from these inflammatory and pathological aspects of pancreatitis. Infected dams exhibited severe colitis, and colonic tissues significantly shortened in length. Brush border epithelial cells were replaced with infiltration of lymphocytes, granulocytes, and microabscess formations into cryptic microstructures. Combination therapy synergistically preserved colonic structure and normalized pathological damages (p < 0.001) and to a lesser degree diclazuril monotherapy protected dams from colitis (p < 0.05) and gastrointestinal toxoplasmosis. Other complications included severe splenitis (p < 0.001) and hepatitis (p < 0.001) which were normalized with combination therapy.
Combination diclazuril plus atovaquone was safe and with a novel therapeutic synergism protected dams and fetuses from toxoplasmosis.
Latent chronic infection with Toxoplasma gondii (T. gondii), a common neurotropic pathogen, has been previously linked with suicidal self-directed violence (SSDV). We sought to determine if latent infection with T. gondii is associated with trait aggression and impulsivity, intermediate phenotypes for suicidal behavior, in psychiatrically healthy adults.
Traits of aggression and impulsivity were analyzed in relationship to IgG antibody seropositivity for T. gondii and two other latent neurotropic infections, herpes simplex virus 1 (HSV1) and cytomegalovirus (CMV). One thousand community-residing adults residing in the Munich metropolitan area with no Axis I or II conditions by SCID for DSM-IV (510 men, 490 women, mean age 53.6 ± 15.8, range 20-74). Plasma samples were tested for IgG antibodies to T. gondii, HSV-1 and CMV by ELISA. Self-reported ratings of trait aggression scores (Questionnaire for Measuring Factors of Aggression [FAF]) and trait impulsivity (Sensation-Seeking Scale-V [SSS-V]) were analyzed using linear multivariate methods.
T. gondii IgG seropositivity was significantly associated with higher trait reactive aggression scores among women (p < .01), but not among men. T. gondii-positivity was also associated with higher impulsive sensation-seeking (SSS-V Disinhibition) among younger men (p < .01) aged 20-59 years old (median age = 60). All associations with HSV-1 and CMV were not significant.
Aggression and impulsivity, personality traits considered as endophenotypes for SSDV, are associated with latent T. gondii infection in a gender and age-specific manner, and could be further investigated as prognostic and treatment targets in T. gondii-positive individuals at risk for SSDV.
Published by Elsevier Ltd.
The obligate intracellular parasite, Toxoplasma gondii, disseminates through its host inside infected immune cells. We hypothesize that parasite nutrient requirements lead to manipulation of migratory properties of the immune cell. We demonstrate that 1) T. gondii relies on glutamine for optimal infection, replication and viability, and 2) T. gondii-infected bone marrow-derived dendritic cells (DCs) display both "hypermotility" and "enhanced migration" to an elevated glutamine gradient in vitro. We show that glutamine uptake by the sodium-dependent neutral amino acid transporter 2 (SNAT2) is required for this enhanced migration. SNAT2 transport of glutamine is also a significant factor in the induction of migration by the small cytokine stromal cell-derived factor-1 (SDF-1) in uninfected DCs. Blocking both SNAT2 and C-X-C chemokine receptor 4 (CXCR4; the unique receptor for SDF-1) blocks hypermotility and the enhanced migration in T. gondii-infected DCs. Changes in host cell protein expression following T. gondii infection may explain the altered migratory phenotype; we observed an increase of CD80 and unchanged protein level of CXCR4 in both T. gondii-infected and lipopolysaccharide (LPS)-stimulated DCs. However, unlike activated DCs, SNAT2 expression in the cytosol of infected cells was also unchanged. Thus, our results suggest an important role of glutamine transport via SNAT2 in immune cell migration and a possible interaction between SNAT2 and CXCR4, by which T. gondii manipulates host cell motility.
Gelatinous polymers including extracellular polymeric substances (EPSs) are fundamental to biophysical processes in aquatic habitats, including mediating aggregation processes and functioning as the matrix of biofilms. Yet insight into the impact of these sticky molecules on the environmental transmission of pathogens in the ocean is limited. We used the zoonotic parasite Toxoplasma gondii as a model to evaluate polymer-mediated mechanisms that promote transmission of terrestrially derived pathogens to marine fauna and humans. We show that transparent exopolymer particles, a particulate form of EPS, enhance T. gondii association with marine aggregates, material consumed by organisms otherwise unable to access micrometre-sized particles. Adhesion to EPS biofilms on macroalgae also captures T. gondii from the water, enabling uptake of pathogens by invertebrates that feed on kelp surfaces. We demonstrate the acquisition, concentration and retention of T. gondii by kelp-grazing snails, which can transmit T. gondii to threatened California sea otters. Results highlight novel mechanisms whereby aquatic polymers facilitate incorporation of pathogens into food webs via association with particle aggregates and biofilms. Identifying the critical role of invisible polymers in transmission of pathogens in the ocean represents a fundamental advance in understanding and mitigating the health impacts of coastal habitat pollution with contaminated runoff.