Wednesday, September 17, 2014

Selective and strain-specific NFAT4 activation by the Toxoplasma gondii polymorphic dense granule protein GRA6

 2014 Sep 15. pii: jem.20131272. [Epub ahead of print]

Abstract

Toxoplasma gondii infection results in co-option and subversion of host cellular signaling pathways. This process involves discharge of T. gondii effector molecules from parasite secretory organelles such as rhoptries and dense granules. We report that the T. gondii polymorphic dense granule protein GRA6 regulates activation of the host transcription factor nuclear factor of activated T cells 4 (NFAT4). GRA6 overexpression robustly and selectively activated NFAT4 via calcium modulating ligand (CAMLG). Infection with wild-type (WT) but not GRA6-deficient parasites induced NFAT4 activation. Moreover, GRA6-deficient parasites failed to exhibit full virulence in local infection, and the treatment of WT mice with an NFAT inhibitor mitigated virulence of WT parasites. Notably, NFAT4-deficient mice displayed prolonged survival, decreased recruitment of CD11b+ Ly6G+ cells to the site of infection, and impaired expression of chemokines such as Cxcl2 and Ccl2. In addition, infection with type I parasites culminated in significantly higher NFAT4 activation than type II parasites due to a polymorphism in the C terminus of GRA6. Collectively, our data suggest that GRA6-dependent NFAT4 activation is required for T. gondii manipulation of host immune responses to maximize the parasite virulence in a strain-dependent manner.
© 2014 Ma et al.
PMID:
 
25225460
 
[PubMed - as supplied by publisher]

Sustained Translational Repression of Lactate Dehydrogenase 1 in Toxoplasma gondii Bradyzoites is Conferred by a Small Regulatory RNA Hairpin

 2014 Sep 15. doi: 10.1111/febs.13048. [Epub ahead of print]

Abstract

In response to environmental stresses, Toxoplasma gondii induces a global translational repression which allows for the remodeling of its transcriptome. While some transcripts are preferentially translated, another subset is translationally repressed and maintained in bradyzoites. Although little is known of how transcripts are targeted for sustained translational repression, the targeting likely operates through an RNA-centric mechanism relying on the recognition of cis-acting elements. In this study, we sought to determine if the targeting of transcripts through recognizable cis-acting elements could be responsible for the transcript-specific sustained translational repression displayed by Toxoplasma bradyzoites. We examined the UTRs of a translationally repressed gene, lactate dehydrogenase 1, and found a 40 nucleotide regulatory element in its 5'UTR. This element specifically induces translational repression in otherwise constitutively expressed transcripts. Mutational studies revealed that the formation of a small 16 nucleotide regulatory RNA hairpin is essential for this activity. We suggest that this hairpin may act as the nucleation site for the binding of a yet to be identified trans-acting factor that allows for the transcript to be targeted for translational repression removal from the active translational pool. To our knowledge, this is the first report characterizing a specific cis-acting element contributing to post-transcriptional gene regulation in Toxoplasma and suggests the presence of a pathway by which the parasites can recognize, identify, and specifically target transcripts for sustained translational repression under stressful conditions. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.

KEYWORDS:

Toxoplasma gondii ; 5'UTR; RNA hairpin; lactate dehydrogenase; translational repression
PMID:
 
25223457
 
[PubMed - as supplied by publisher]

Expanded task battery in the Morris water maze reveals effects of Toxoplasma gondii infection on learning and memory in rats

 2014 Sep 8. pii: S1383-5769(14)00113-5. doi: 10.1016/j.parint.2014.09.002. [Epub ahead of print]

Abstract

Infection with the neurotropic parasite Toxoplasma gondii is wide spread among human populations; however, the impacts of latent central nervous system (CNS) T. gondii infection have only recently come to light. Epidemiological evidence in humans and experimental studies in rodents have revealed a number of neurological and behavioral sequelae following the establishment of latent CNS toxoplasmosis. Here, we report alterations in learning and memory task performance in latently infected rats using the Morris water maze. While simple spatial reference learning was intact, infected rodents exhibited poor performance compared to controls in probe trials requiring spatial memory recall and progressively poorer performance with increasing time intervals before memory testing, but, surprisingly, enhanced performance in reversal learning tasks. Despite obvious changes to memory task performance, no cysts were detected in the hippocampi of infected rats. Instead, cysts were stochastically distributed across the entire brain, suggesting that behavioral alterations in this study were due to accumulated changes in neurophysiology across multiple anatomical regions. Together, these data provide new evidence that latent toxoplasmosis contributes to neurocognitive symptoms in mammalian hosts, and does so on a broad anatomical scale within the CNS.
Copyright © 2014. Published by Elsevier Ireland Ltd.

KEYWORDS:

Morris water maze; Toxoplasma gondii; behavior; toxoplasmosis
PMID:
 
25220582
 
[PubMed - as supplied by publisher]

Monday, September 08, 2014

POSTDOCTORAL POSITION available

POSTDOCTORAL POSITION
Indiana University School of Medicine
POSTDOCTORAL POSITION available to investigate gene expression and cellular signaling in the protozoan parasite Toxoplasma gondii. Related to the malaria parasite, Plasmodium, Toxoplasma causes birth defects and life-threatening infection in immunocompromised patients. We have shown that lysine acetylation is required for parasite growth and development, representing an exciting new drug target (Wang et al., PLoS Pathogens 2014; Jeffers & Sullivan, Eukaryotic Cell 2012; Naguleswaran et al., PLoS Pathogens 2010). Current projects involve analyzing the role of lysine acetylation in cellular signaling and gene expression, as well as the regulation of lysine acetyltransferase (KAT) enzymes.
Position requires a Ph.D., strong expertise in molecular biology, biochemistry, and cell signaling, and excellent communication skills (speaking and writing English). Experience in microbiology/parasitology or epigenetics is a plus, but not required. Please read this before applying. Submit CV and contact information for three references to Dr. Bill Sullivan (wjsulliv@iu.edu).
Our lab is part of the “Intracellular Pathogens Group” at IU, which meets regularly to foster innovation and collaboration. Visit www.sullivanlab.com for more information.
Located in downtown Indianapolis, Indiana University School of Medicine (IUSM) is the second largest medical school in the US and boasts an outstanding intellectual atmosphere and core facilities. IUSM was nationally ranked in the Top 30 Best Places to Work for Postdocs. IUSM is an equal opportunity employer.

Wednesday, September 03, 2014

Toxoplasma, or the discovery of a heterophage

2014 Aug 29. pii: S1471-4922(14)00143-3. doi: 10.1016/j.pt.2014.08.005. [Epub ahead of print
 
In mammalian cells, the protozoan pathogen Toxoplasma resides in a nonfusiogenic vacuole that segregates it from host cell resources. How the parasite acquires nutrients and whether it is capable of internalizing host macromolecules have been long-standing mysteries. By exploiting a mutant of Toxoplasma lacking the cathepsin protease L, Dou et al. observed the accumulation of host cytosolic-derived proteins in a multivesicular post-Golgi compartment, which establishes the existence of a functional heterophagic pathway in Toxoplasma.

KEYWORDS:

Toxoplasma; intracellular parasitism; macromolecule digestion; nutrient uptake; protease cathepsins
PMID:
25178740
[PubMed - as supplied by publisher]

Wednesday, August 27, 2014

Electrophoretic Patterns of Toxoplasma gondii Excreted/Secreted Antigens and Their Role in Induction of the Humoral Immune Response

2014 Apr;7(4):e9525. doi: 10.5812/jjm.9525. Epub 2014 Apr 1
 

BACKGROUND:

Toxoplasma gondii is an obligatory intracellular protozoan parasite on which studies are pending regarding production of vaccine. To date, the production of human vaccine has not been successful where approximately one third of the world's population is thought to be infected with T. gondii.

OBJECTIVES:

The present study was designed to compare the electrophoretic patterns of T. gondii excreted/secreted antigens (ESAs) and determine their role in the stimulation of the humoral immune response.

MATERIALS AND METHODS:

T. gondii ESAs were prepared from cell cultures (albino rat fibroblast) and cell-free mediums (RPMI-1640). Next, the SDS-PAGE technique was used for comparing molecular weights of the antigens. Forty C57BL/6 mice were divided randomly into four groups (n = 10). Immunization was performed subcutaneously at an interval of 2 weeks in two groups by injecting 100 µg of each of the above-mentioned antigens. Two groups, as negative control, also received fibroblast lysate proteins or adjuvant separately. All of the groups were then challenged with the T. gondii RH strain. Serum samples were collected from all mice and measured by immunoblotting technique for detection of immunogenic antigens.

RESULTS:

The electrophoretic mobility of the prepared antigens/proteins from cell culture, cell-free media, Fibroblast Lysate Proteins and Toxoplasma Lysate Antigens (TLA) showed 13, 12, 8 and 8 bands, respectively. The case groups, in challenge with T. gondii (RH strain), showed more survival prolongation than the control groups. Furthermore, the survival period was identical for both case groups with a tendency for slightly higher survival of mice receiving ESA from cell-free medium. Analysis of sera by immunoblotting also revealed one band of 65 KDa in sera from both case groups.

CONCLUSIONS:

We suggest that this band be extracted and its amino acids sequence determined to produce Synthetic Polypeptide for immunization studies.

KEYWORDS:

Immunization; Immunoblotting; Toxoplasma
PMID:
25147706
[PubMed]

Internalization and TLR-dependent type I interferon production by monocytes in response to Toxoplasma gondii

2014 Aug 26. doi: 10.1038/icb.2014.70. [Epub ahead of print]
 
 
The classic anti-viral cytokine interferon (IFN)-β can be induced during parasitic infection, but relatively little is know about the cell types and signaling pathways involved. Here we show that inflammatory monocytes (IMs), but not neutrophils, produce IFN-β in response to T. gondii infection. This difference correlated with the mode of parasite entry into host cells, with phagocytic uptake predominating in IMs and active invasion predominating in neutrophils. We also show that expression of IFN-β requires phagocytic uptake of the parasite by IMs, and signaling through Toll-like receptors (TLRs) and MyD88. Finally, we show that IMs are major producers of IFN-β in mesenteric lymph nodes following in vivo oral infection of mice, and mice lacking the receptor for type I IFN-1 show higher parasite loads and reduced survival. Our data reveal a TLR and internalization-dependent pathway in IMs for IFN-β induction to a non-viral pathogen.Immunology and Cell Biology advance online publication, 26 August 2014; doi:10.1038/icb.2014.70.
PMID:
25155465
[PubMed - as supplied by publisher]

Nuclear Glycolytic Enzyme Enolase of Toxoplasma gondii Functions as a Transcriptional Regulator

2014 Aug 25;9(8):e105820. doi: 10.1371/journal.pone.0105820. eCollection 2014.
 
 
Apicomplexan parasites including Toxoplasma gondii have complex life cycles within different hosts and their infectivity relies on their capacity to regulate gene expression. However, little is known about the nuclear factors that regulate gene expression in these pathogens. Here, we report that T. gondii enolase TgENO2 is targeted to the nucleus of actively replicating parasites, where it specifically binds to nuclear chromatin in vivo. Using a ChIP-Seq technique, we provide evidence for TgENO2 enrichment at the 5' untranslated gene regions containing the putative promoters of 241 nuclear genes. Ectopic expression of HA-tagged TgENO1 or TgENO2 led to changes in transcript levels of numerous gene targets. Targeted disruption of TgENO1 gene results in a decrease in brain cyst burden of chronically infected mice and in changes in transcript levels of several nuclear genes. Complementation of this knockout mutant with ectopic TgENO1-HA fully restored normal transcript levels. Our findings reveal that enolase functions extend beyond glycolytic activity and include a direct role in coordinating gene regulation in T. gondii.
PMID:
25153525
[PubMed - in process]

Protozoan parasites and type I interferons: a cold case reopened

2014 Aug 18. pii: S1471-4922(14)00128-7. doi: 10.1016/j.pt.2014.07.007. [Epub ahead of print
 
 
Protozoan parasites, such as Plasmodium, Toxoplasma, Cryptosporidium, trypanosomes, and Leishmania, are a major cause of disease in both humans and other animals, highlighting the need to understand the full spectrum of strategies used by the host immune system to sense and respond to parasite infection. Although type II interferon (IFN-γ) has long been recognized as an essential antiparasite immune effector, much less is known about the role of type I interferons (IFN-α and -β) in host defense, particularly in vivo. Recent studies are reviewed which collectively highlight that type I IFN can be induced in response to parasite infection and influence the outcome of infection.
Copyright © 2014 Elsevier Ltd. All rights reserved.

KEYWORDS:

immunity; infection; intracellular parasite; protozoan; type I interferon
PMID:
25153940
[PubMed - as supplied by publisher]

Friday, August 22, 2014

Nucleotide-Oligomerization-Domain-2 Affects Commensal Gut Microbiota Composition and Intracerebral Immunopathology in Acute Toxoplasma gondii Induced Murine Ileitis

2014 Aug 20;9(8):e105120. doi: 10.1371/journal.pone.0105120. eCollection 2014.
 

BACKGROUND:

Within one week following peroral high dose infection with Toxoplasma (T.) gondii, susceptible mice develop non-selflimiting acute ileitis due to an underlying Th1-type immunopathology. The role of the innate immune receptor nucleotide-oligomerization-domain-2 (NOD2) in mediating potential extra-intestinal inflammatory sequelae including the brain, however, has not been investigated so far.

METHODOLOGY/PRINCIPAL FINDINGS:

Following peroral infection with 100 cysts of T. gondii strain ME49, NOD2-/- mice displayed more severe ileitis and higher small intestinal parasitic loads as compared to wildtype (WT) mice. However, systemic (i.e. splenic) levels of pro-inflammatory cytokines such as TNF-α and IFN-γ were lower in NOD2-/- mice versus WT controls at day 7 p.i. Given that the immunopathological outcome might be influenced by the intestinal microbiota composition, which is shaped by NOD2, we performed a quantitative survey of main intestinal bacterial groups by 16S rRNA analysis. Interestingly, Bifidobacteria were virtually absent in NOD2-/- but not WT mice, whereas differences in remaining bacterial species were rather subtle. Interestingly, more distinct intestinal inflammation was accompanied by higher bacterial translocation rates to extra-intestinal tissue sites such as liver, spleen, and kidneys in T. gondii infected NOD2-/- mice. Strikingly, intracerebral inflammatory foci could be observed as early as seven days following T. gondii infection irrespective of the genotype of animals, whereas NOD2-/- mice exhibited higher intracerebral parasitic loads, higher F4/80 positive macrophage and microglia numbers as well as higher IFN-γ mRNA expression levels as compared to WT control animals.

CONCLUSION/SIGNIFICANCE:

NOD2 signaling is involved in protection of mice from T. gondii induced acute ileitis. The parasite-induced Th1-type immunopathology at intestinal as well as extra-intestinal sites including the brain is modulated in a NOD2-dependent manner.
PMID:
25141224
[PubMed - in process]

Design, synthesis and biological characterization of thiazolidin-4-one derivatives as promising inhibitors of Toxoplasma gondii

2014 Aug 15;86C:17-30. doi: 10.1016/j.ejmech.2014.08.046. [Epub ahead of print]
 
 
We designed and synthesized a large number of novel thiazolidin-4-one derivatives for the evaluation of their anti-Toxoplasma gondii activity. This scaffold was functionalized at the N1-hydrazine portion with aliphatic, cycloaliphatic and (hetero)aromatic moieties. Then, a benzyl pendant was introduced at the lactamic NH of the core nucleus to evaluate the influence of this chemical modification on biological activity. The compounds were subjected to several in vitro assays to assess their anti-parasitic efficacy, cytotoxicity on fibroblasts, inhibition of tachyzoite invasion/attachment and replication after treatment. Results showed that fourteen of these thiazole-based compounds compare favorably to control compound trimethoprim in terms of parasite growth inhibition.
Copyright © 2014. Published by Elsevier Masson SAS.

KEYWORDS:

Cytotoxicity; Host cell invasion; Parasite growth inhibition; Thiazolidin-4-one; Toxoplasma
PMID:
25140751
[PubMed - as supplied by publisher]

Toxoplasma gondii infection reduces predator aversion in rats through epigenetic modulation in the host medial amygdala

2014 Aug 20. doi: 10.1111/mec.12888. [Epub ahead of print]
 

Abstract

Male rats (Rattus novergicus) infected with protozoan Toxoplasma gondii relinquish their innate aversion to the cat odors. This behavioral change is postulated to increase transmission of the parasite to its definitive felid hosts. Here, we show that the Toxoplasma gondii infection institutes an epigenetic change in the DNA methylation of the arginine vasopressin promoter in the medial amygdala of male rats. Infected animals exhibit hypomethylation of arginine vasopressin promoter, leading to greater expression of this nonapeptide. The infection also results in the greater activation of the vasopressinergic neurons after exposure to the cat odor. Furthermore, we show that loss of fear in the infected animals can be rescued by the systemic hypermethylation, and recapitulated by directed hypomethylation in the medial amygdala. These results demonstrate an epigenetic proximate mechanism underlying the extended phenotype in the Rattus novergicus - Toxoplasma gondii association. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.

KEYWORDS:

Arginine vasopressin; Behavioral manipulation; DNA methylation; Extended phenotype; Fear; Testosterone
PMID:
25142402
[PubMed - as supplied by publisher]

Wednesday, August 20, 2014

Effects of soluble extracts from Leishmania infantum promastigotes, Toxoplasma gondii tachyzoites on TGF-β mediated pathways in activated CD4+ T lymphocytes

2014 Aug 12. pii: S1286-4579(14)00102-6. doi: 10.1016/j.micinf.2014.08.002. [Epub ahead of print]
 
 
Interference with transforming growth factor-β-mediated pathways helps several parasites to survive for long periods in immunocompetent hosts. Macrophages and dendritic cells infected by Toxoplasma, Leishmania and Plasmodium spp. produce large amounts of transforming growth factor-β and induce the differentiation of antigen-specific T-regulatory cells. Mechanisms not mediated by antigen-presentation could also account for the expansion of T-regulatory cells in parasitic diseases and they also might be mediated through transforming growth factor-β-receptor activated pathways. We explored the properties of soluble extracts from Leishmania infantum promastigotes, Toxoplasma gondii tachyzoites, Trichinella spiralis muscle larvae to expand the pool of T-regulatory cells in a population of polyclonally activated T cells in the absence of accessory cells, and compared their effects to those induced by Plasmodium falciparum extracts. Similarly to Plasmodium falciparum, Leishmania infantum extracts activate the latent soluble form of transforming growth factor-β and that bound to the membrane of activated T lymphocytes. The interaction of the active cytokine with transforming growth factor-β receptor induces Foxp3 expression by activated lymphocytes, favouring their conversion through the T-regulatory phenotype. Both Toxoplasma gondii and Leishmania infantum extracts are able to induce transforming growth factor-β production by activated T cells in the absence of accessory cells.
Copyright © 2014. Published by Elsevier Masson SAS.

KEYWORDS:

Leishmania infantum; T-regulatory cells; Toxoplasma gondii; transforming growth factor
PMID:
25130316
[PubMed - as supplied by publisher]

Withdrawal of skeletal muscle cells from cell cycle progression triggers differentiation of Toxoplasma gondii towards the bradyzoite stage

2014 Aug 14. doi: 10.1111/cmi.12342. [Epub ahead of print]
 
 
Toxoplasma gondii is a widespread intracellular parasite of mammals and birds and an important opportunistic pathogen of humans. Following primary infection, fast replicating tachyzoites disseminate within the host and are subsequently either eliminated by the immune system or transform to latent bradyzoites which preferentially persist in brain and muscle tissues. The factors which determine the parasites' tissue distribution during chronic toxoplasmosis are unknown. Here we show that mouse skeletal muscle cells (SkMCs) after differentiation to mature, myosin heavy chain-positive, polynucleated myotubes, significantly restrict tachyzoite replication and facilitate expression of bradyzoite-specific antigens and tissue cyst formation. In contrast, proliferating mononuclear myoblasts and control fibroblasts enable vigorous T. gondii replication but do not sustain bradyzoite or tissue cyst formation. Bradyzoite formation correlates with up-regulation of testis-specific Y-encoded-like protein-2 gene expression (Tspyl2) and p21Waf1/Cip1 as well as down-regulation of cyclin B1 and absence of DNA synthesis, i.e. a cell cycle arrest of syncytial myotubes. Following infection with T. gondii, myotubes but not myoblasts or fibroblasts further up-regulate the negative cell cycle regulator Tspyl2. Importantly, RNA interference-mediated knockdown of Tspyl2 abrogates differentiation of SkMCs to myotubes and enables T. gondii to replicate vigorously but abolishes bradyzoite-specific gene expression and tissue cyst formation. Together, these data indicate that Tspyl2-mediated host cell cycle withdrawal is a physiological trigger of Toxoplasma stage conversion in mature SkMCs. This finding might explain the preferred distribution of T. gondii tissue cysts in vivo.
This article is protected by copyright. All rights reserved.
PMID:
25131712
[PubMed - as supplied by publisher]

One minute ultraviolet exposure inhibits Toxoplasma gondii tachyzoite replication and cyst conversion without diminishing host humoral-mediated immune response

2014 Aug 14. pii: S0014-4894(14)00191-X. doi: 10.1016/j.exppara.2014.08.001. [Epub ahead of print
 
 
We developed a protocol to inactivate Toxoplasma gondii (T. gondii) tachyzoites employing 1 minute of ultraviolet (UV) exposure. We show that this treatment completely inhibited parasite replication and cyst formation in vitro and in vivo but did not affect the induction of a robust IgG response in mice. We propose that our protocol can be used to study the contribution of the humoral immune response to rodent behavioral alterations following T. gondii infection.
Copyright © 2014. Published by Elsevier Inc.

KEYWORDS:

Animal models; Behavior; Immune response; Inactivation, Cysts; Toxoplasma
PMID:
25131777
[PubMed - as supplied by publisher]

Monday, August 18, 2014

Toxoplasma gondii and anxiety disorders in a community-based sample

2014 Aug 12. pii: S0889-1591(14)00418-8. doi: 10.1016/j.bbi.2014.08.001. [Epub ahead of print]
 

Abstract

A growing body of literature suggests that exposure to the neurotropic parasite Toxoplasma gondii (T. gondii) is associated with increased risk of mental disorders, particularly schizophrenia. However, a potential association between T. gondii exposure and anxiety disorders has not been rigorously explored. Here, we examine the association of T. gondii infection with both anxiety and mood disorders. Participants (n=484) were drawn from the Detroit Neighborhood Health Study, a population-representative sample of Detroit residents. Logistic regression was used to examine the associations between T. gondii exposure (defined by seropositivity and IgG antibody levels) and three mental disorders: generalized anxiety disorder (GAD), posttraumatic stress disorder (PTSD) and depression. We found that T. gondii seropositivity was associated with a 2 times greater odds of GAD (odds ratio (OR), 2.25; 95% confidence interval (CI), 1.11-4.53) after adjusting for age, gender, race, income, marital status, and medication. Individuals in the highest antibody level category had more than 3 times higher odds of GAD (OR, 3.35; 95% CI, 1.41-7.97). Neither T. gondii seropositivity nor IgG antibody levels was significantly associated with PTSD or depression. Our findings indicate that T. gondii infection is strongly and significantly associated with GAD. While prospective confirmation is needed, T. gondii infection may play a role in the development of GAD.
Copyright © 2014. Published by Elsevier Inc.

KEYWORDS:

Depression; Generalized anxiety disorder; Infection; Mental health; PTSD; Toxoplasma gondii
PMID:
25124709
[PubMed - as supplied by publisher]

Sequence Variation in Toxoplasma gondii rop17 Gene among Strains from Different Hosts and Geographical Locations

2014;2014:349325. doi: 10.1155/2014/349325. Epub 2014 Jul 10.
 

Abstract

Genetic diversity of T. gondii is a concern of many studies, due to the biological and epidemiological diversity of this parasite. The present study examined sequence variation in rhoptry protein 17 (ROP17) gene among T. gondii isolates from different hosts and geographical regions. The rop17 gene was amplified and sequenced from 10 T. gondii strains, and phylogenetic relationship among these T. gondii strains was reconstructed using maximum parsimony (MP), neighbor-joining (NJ), and maximum likelihood (ML) analyses. The partial rop17 gene sequences were 1375 bp in length and A+T contents varied from 49.45% to 50.11% among all examined T. gondii strains. Sequence analysis identified 33 variable nucleotide positions (2.1%), 16 of which were identified as transitions. Phylogeny reconstruction based on rop17 gene data revealed two major clusters which could readily distinguish Type I and Type II strains. Analyses of sequence variations in nucleotides and amino acids among these strains revealed high ratio of nonsynonymous to synonymous polymorphisms (>1), indicating that rop17 shows signs of positive selection. This study demonstrated the existence of slightly high sequence variability in the rop17 gene sequences among T. gondii strains from different hosts and geographical regions, suggesting that rop17 gene may represent a new genetic marker for population genetic studies of T. gondii isolates.
PMID:
25126596
[PubMed - in process]
PMCID:
PMC4121216

Activated microglia contribute to neuronal apoptosis in Toxoplasmic Encephalitis

2014 Aug 15;7(1):372. [Epub ahead of print]
 

Abstract

BACKGROUND:

A plethora of evidence shows that activated microglia play a critical role in the pathogenesis of the central nervous system (CNS). Toxoplasmic encephalitis (TE) frequently occurs in HIV/AIDS patients. However, knowledge remains limited on the contributions of activated microglia to the pathogenesis of TE.

METHODS:

A murine model of reactivated encephalitis was generated in a latent infection with Toxoplasma gondii induced by cyclophosphamide. The neuronal apoptosis in the CNS and the profile of pro-inflammatory cytokines were assayed in both in vitro and in vivo experiments.

RESULTS:

Microglial cells were found to be activated in the cortex and hippocampus in the brain tissues of mice. The in vivo expression of interleukin-6 (IL-6), interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and inducible nitric oxide synthase (iNOS) were up-regulated in TE mice, and accordingly, the neuronal apoptosis was significantly increased. The results were positively correlated with those of the in vitro experiments. Additionally,apoptosis of the mouse neuroblastoma type Neuro2a (N2a) remarkably increased when the N2a was co-cultured in transwell with microglial cells and Toxoplasma tachyzoites. Both in vivo and in vitro experiments showed that minocycline (a microglia inhibitor) treatment notably reduced microglial activation and neuronal apoptosis.

CONCLUSIONS:

Activated microglia contribute to neuronal apoptosis in TE and inhibition of microglia activation might represent a novel therapeutic strategy of TE.
PMID:
25128410
[PubMed - as supplied by publisher]

The potential of quinoline derivatives for the treatment of Toxoplasma gondii Infection

2014 Aug 13. pii: S0014-4894(14)00198-2. doi: 10.1016/j.exppara.2014.08.008. [Epub ahead of print]
 

Abstract

Here we reported our investigation, as part of our drug repositioning effort, on anti-Toxoplasma properties of newly synthesized quinoline compounds. A collection of 4-aminoquinoline and 4-piperazinylquinoline analogs have recently been synthesized for use in cancer chemotherapy. Some analogs were able to outperform chloroquine, a quinoline derivative drug which is commonly used in the treatment of malaria and other parasitic infections. Herein 58 compounds containing one or two quinoline rings were examined for their effectiveness as potential anti-Toxoplasma compounds. Of these 58 compounds, 32 were efficient at inhibiting Toxoplasma growth (IC50 < 100 μM). Five compounds with single and simple quinoline rings exhibited similar cLogP values of ∼2 and IC50 values between 5 - 6 μM, with one exception of 8-hydroxyquinoline whose IC50 value was 213 nM. The addition of one hydroxyl group at position 8 caused a 40-fold increase in the inhibitory effect of quinoline. A significant improvement in anti-Toxoplasma effect among quinoline derivatives was detected in B11, B12, B23, and B24, whose structures carry two quinoline rings, and their resultant cLogP values are ⩾7. Among these compounds, B23 was the most effective compound with IC50 value of 425 ± 35 nM, and TI value of 4.9. It was also noted that compounds with at least one quinoline ring, displaying anti-Toxoplasma effects were capable of causing the disappearance of the apicoplast, a plastid-like organelle. When treated with quinoline, 8-hydroxyquinoline or B23, 40 - 45% of the parasites lost their apicoplasts. Our findings recapitulate the properties of quinoline derivatives in diminishing apicoplast. This could aid further investigations of anti-parasitic treatments specific to Apicomplexan. More importantly, B12 and B23 which harbor superior anti-cancer properties than chloroquine, have effective anti-Toxoplasma activity. These compounds therefore have significant potential for future development of chemotherapeutic agents for patients suffering from breast cancers and parasitic infection.
Copyright © 2014. Published by Elsevier Inc.

KEYWORDS:

Apicoplast; Quinoline derivatives; Toxoplasma gondii
PMID:
25128801
[PubMed - as supplied by publisher]