ACS Med Chem Lett. 2013 Oct 4;4(12):1148-1151.

Discovery of potent and selective inhibitors of Toxoplasma gondii thymidylate synthase for opportunistic infections

Zaware N¹, Sharma H², Yang J¹, Devambatla RK¹, Queener SF³, Anderson KS², Gangjee A¹.

 

Infection by the parasite Toxoplasma gondii (tg) can lead to toxoplasmosis in immunocompromised patients such as organ transplant, cancer and HIV/AIDS patients. The bifunctional thymidylate synthase-dihydrofolate reductase (TS-DHFR) enzyme is crucial for nucleotide synthesis in T. gondii, and represents a potential target to combat T. gondii infection. While species selectivity with drugs has been attained for DHFR, TS is much more conserved across species and specificity is significantly more challenging. We discovered novel substituted-9H-pyrimido[4,5-b]indoles 1-3 with single-digit nanomolar K_i for tgTS, two of which, 2 and 3, are 28- and 122-fold selective over human TS (hTS). The synthesis of these compounds, and their structures in complex with tgTS-DHFR are presented along with binding measurements and cell culture data. These results show, for the very first time, that in spite of the high degree of conservation of active site residues between hTS and the parasite TS, specificity has been accomplished via novel structures and provides a new target (TS) for selective drug development against parasitic infections.

KEYWORDS:

Active-site inhibitors, Crystal structure, Opportunistic infection, Thymidylate-synthase inhibitors, Toxoplasma gondii

PMID:

24470841

[PubMed]

PLoS One. 2014 Jan 17;9(1):e86684. doi: 10.1371/journal.pone.0086684. eCollection 2014.

The E2-Like Conjugation Enzyme Atg3 Promotes Binding of IRG and Gbp Proteins to Chlamydia- and Toxoplasma-Containing Vacuoles and Host Resistance

Haldar AK¹, Piro AS¹, Pilla DM¹, Yamamoto M², Coers J¹.

 

Cell-autonomous immunity to the bacterial pathogen Chlamydia trachomatis and the protozoan pathogen Toxoplasma gondii is controlled by two families of Interferon (IFN)-inducible GTPases: Immunity Related GTPases (IRGs) and Guanylate binding proteins (Gbps). Members of these two GTPase families associate with pathogen-containing vacuoles (PVs) and solicit antimicrobial resistance pathways specifically to the intracellular site of infection. The proper delivery of IRG and Gbp proteins to PVs requires the autophagy factor Atg5. Atg5 is part of a protein complex that facilitates the transfer of the ubiquitin-like protein Atg8 from the E2-like conjugation enzyme Atg3 to the lipid phosphatidylethanolamine. Here, we show that Atg3 expression, similar to Atg5 expression, is required for IRG and Gbp proteins to dock to PVs. We further demonstrate that expression of a dominant-active, GTP-locked IRG protein variant rescues the PV targeting defect of Atg3- and Atg5-deficient cells, suggesting a possible role for Atg proteins in the activation of IRG proteins. Lastly, we show that IFN-induced cell-autonomous resistance to C. trachomatis infections in mouse cells depends not only on Atg5 and IRG proteins, as previously demonstrated, but also requires the expression of Atg3 and Gbp proteins. These findings provide a foundation for a better understanding of IRG- and Gbp-dependent cell-autonomous resistance and its regulation by Atg proteins.

PMID:

24466199

[PubMed - in process]

Parasit Vectors. 2014 Jan 23;7(1):47. [Epub ahead of print]

Toxoplasma gondii-skeletal muscle cells interaction increases lipid droplet biogenesis and positively modulates the production of IL-12, IFN-g and PGE2

Gomes AF, Magalhães KG, Rodrigues RM, de Carvalho L, Molinaro R, Bozza PT, Barbosa HS.

BACKGROUND:

The interest in the mechanisms involved in Toxoplasma gondii lipid acquisition has steadily increased during the past few decades, but it remains not completely understood. Here, we investigated the biogenesis and the fate of lipid droplets (LD) of skeletal muscle cells (SkMC) during their interaction with T. gondii by confocal and electron microscopy. We also evaluated whether infected SkMC modulates the production of prostaglandin E2 (PGE2), cytokines interleukin-12 (IL-12) and interferon-gamma (INF-g), and also the cyclooxygenase-2 (COX-2) gene induction.

METHODS:

Primary culture of skeletal muscle cells were infected with tachyzoites of T. gondii and analysed by confocal microscopy for observation of LD. Ultrastructural cytochemistry was also used for lipid and sarcoplasmatic reticulum (SR) detection. Dosage of cytokines (IL-12 and INF-g) by ELISA technique and enzyme-linked immunoassay (EIA) for PGE2 measurement were employed. The COX-2 gene expression analysis was performed by real time reverse transcriptase polymerase chain reaction (qRT-PCR).

RESULTS:

We demonstrated that T. gondii infection of SkMC leads to increase in LD number and area in a time course dependent manner. Moreover, the ultrastructural analysis demonstrated that SR and LD are in direct contact with parasitophorous vacuole membrane (PVM), within the vacuolar matrix, around it and interacting directly with the membrane of parasite, indicating that LD are recruited and deliver their content inside the parasitophorous vacuole (PV) in T. gondii-infected SkMC. We also observed a positive modulation of the production of IL-12 and IFN-g, increase of COX-2 mRNA levels in the first hour of T. gondii-SkMC interaction and an increase of prostaglandin E2 (PGE2) synthesis from 6 h up to 48 h of infection.

CONCLUSIONS:

Taken together, the close association between SR and LD with PV could represent a source of lipids as well as other nutrients for the parasite survival, and together with the increased levels of IL-12, INF-g and inflammatory indicators PGE2 and COX-2 might contribute to the establishment and maintenance of chronic phase of the T. gondii infection in muscle cell.

PMID:

24457118

[PubMed - as supplied by publisher]

Nat Rev Immunol. 2014 Jan 24;14(2):109-21. doi: 10.1038/nri3598.

Innate immunity to Toxoplasma gondii infection

Yarovinsky F.

 

Toxoplasma gondii is a protozoan parasite of global importance. In the laboratory setting, T. gondii is frequently used as a model pathogen to study mechanisms of T helper 1 (TH1) cell-mediated immunity to intracellular infections. However, recent discoveries have shown that innate type 1 immune responses that involve interferon-γ (IFNγ)-producing natural killer (NK) cells and neutrophils, rather than IFNγ-producing T cells, predetermine host resistance to T. gondii. This Review summarizes the Toll-like receptor (TLR)-dependent mechanisms that are responsible for parasite recognition and for the induction of IFNγ production by NK cells, as well as the emerging data about the TLR-independent mechanisms that lead to the IFNγ-mediated elimination of T. gondii.

PMID:

24457485

[PubMed - in process]

Cell Microbiol. 2014 Jan 20. doi: 10.1111/cmi.12267. [Epub ahead of print]

Toxoplasma development-turn the switch on or off?

White MW, Radke JR, Radke JB.

 

Toxoplasma gondii exhibits a complex, multi-stage life cycle in which the need for parasite expansion is balanced with the production of transmissible forms. For human disease the key developmental switch is from the tachyzoite to the mature bradyzoite, which is not well understood at the molecular level. This review highlights the role of the tachyzoite in regulating the initiation of bradyzoite differentiation through newly discovered transcription factors of the ApiAP2 family that must be turned off for development to unfold. Exit from the tachyzoite cell cycle is also tightly coordinated with the induction of bradyzoite gene expression, which is strongly influenced by the host cell environment. New evidence suggests a parasite casein kinase II and host anti-growth factor CDA1 can influence specific pathways that are responsible for sensing the host cell environment and informing the parasites decision to continue replication or to develop into bradyzoites. These results indicate tachyzoite gene expression mechanisms and signal transduction pathways likely hold the keys to tissue cyst formation in Toxoplasma.
This article is protected by copyright. All rights reserved.

KEYWORDS:

Apicomplexa, Toxoplasma gondii, cell cycle, development, tissue cyst, transcription

PMID:

24438211

[PubMed - as supplied by publisher]

Bioorg Med Chem Lett. 2013 Dec 31. pii: S0960-894X(13)01411-X. doi: 10.1016/j.bmcl.2013.12.039. [Epub ahead of print]

Virtual screening reveals allosteric inhibitors of the Toxoplasma gondii thymidylate synthase-dihydrofolate reductase

Sharma H¹, Landau MJ², Sullivan TJ³, Kumar VP¹, Dahlgren MK³, Jorgensen WL³, Anderson KS⁴.

 

The parasite Toxoplasma gondii can lead to toxoplasmosis in those who are immunocompromised. To combat the infection, the enzyme responsible for nucleotide synthesis thymidylate synthase-dihydrofolate reductase (TS-DHFR) is a suitable drug target. We have used virtual screening to determine novel allosteric inhibitors at the interface between the two TS domains. Selected compounds from virtual screening inhibited TS activity. Thus, these results show that allosteric inhibition by small drug-like molecules can occur in T. gondii TS-DHFR and pave the way for new and potent species-specific inhibitors.
Copyright © 2014 Elsevier Ltd. All rights reserved.

KEYWORDS:

Dihydrofolate reductase, Thymidylate synthase, Toxoplasma gondii, Virtual screening

PMID:

24440298

[PubMed - as supplied by publisher]

Susceptibility to Toxoplasma gondii proliferation in BeWo human trophoblast cells

Placenta. 2014 Jan 8. pii: S0143-4004(13)00873-4. doi: 10.1016/j.placenta.2013.12.013. [Epub ahead of print]

Susceptibility to Toxoplasma gondii proliferation in BeWo human trophoblast cells is dose-dependent of macrophage migration inhibitory factor (MIF), via ERK1/2 phosphorylation and prostaglandin E2 production

Barbosa BF¹, Paulesu L², Ietta F³, Bechi N⁴, Romagnoli R⁵, Gomes AO⁶, Favoreto-Junior S⁷, Silva DA⁸, Mineo JR⁹, Mineo TW¹⁰, Ferro EA¹¹.

INTRODUCTION:

Macrophage migration inhibitory factor (MIF) participates in the immune response to Toxoplasma gondii, triggers ERK1/2 and prostaglandin E₂ (PGE₂) activation, but there is limited information on these mechanisms in human trophoblast. The present study aimed to verify the role of MIF in the ERK1/2 phosphorylation and PGE₂ production, as well as its effect on the susceptibility to T. gondii in BeWo cells.

METHODS:

BeWo cells were treated with increasing concentrations of recombinant MIF (rMIF) and/or T. gondii-soluble tachyzoite antigen (STAg) and analyzed for ERK1/2 phosphorylation and PGE₂ production by Western blotting and ELISA, respectively. Cells were also treated with increasing concentrations of rMIF, rPGE₂, or ERK1/2 inhibitor and tested for T. gondii proliferation. The supernatants of cells treated with rPGE₂ were assayed for cytokine production by ELISA or CBA.

RESULTS:

ERK1/2 phosphorylation and PGE₂ production increased when the cells were treated with low MIF concentrations while the parasitism control occurred only at high MIF concentrations. STAg was unable to change ERK1/2 phosphorylation or PGE₂ release. BeWo cells demonstrated increased T. gondii proliferation and reduced production of pro-inflammatory cytokines when treated with PGE₂, while PD98059 diminished the parasite proliferation.

DISCUSSION:

The intracellular mechanisms triggered by MIF are dose-dependent in BeWo cells, and PGE₂ is an important factor for the persistence of T. gondii at the maternal fetal interface.

CONCLUSION:

MIF was unable to control T. gondii infection in BeWo cells at low concentrations since ERK1/2 and PGE₂ expression were activated, demonstrating a critical effect of these mediators favoring parasite proliferation.
Copyright © 2014 Elsevier Ltd. All rights reserved.

KEYWORDS:

ERK1/2, MIF, PGE(2), Toxoplasma gondii, Trophoblast cells

PMID:

24433846

[PubMed - as supplied by publisher]

Phosphatidylethanolamine synthesis in the parasite mitochondrion is required for efficient growth but dispensable for survival of Toxoplasma

J Biol Chem. 2014 Jan 15. [Epub ahead of print]

Phosphatidylethanolamine synthesis in the parasite mitochondrion is required for efficient growth but dispensable for survival of Toxoplasma gondii.

Hartmann A, Hellmund M, Lucius R, Voelker DR, Gupta N.

Author information

Abstract

Toxoplasma gondii is a highly prevalent obligate intracellular parasite of the phylum Apicomplexa that also includes other parasites of clinical/veterinary importance, such as Plasmodium, Cryptosporidium and Eimeria. Acute infection by Toxoplasma is hallmarked by rapid proliferation in its host cells, and requires synthesis of parasite membranes. Phosphatidylethanolamine (PtdEtn) is the second major phospholipid class in T. gondii. Here, we reveal that PtdEtn is produced in the parasite mitochondrion and parasitophorous vacuole by decarboxylation of phosphatidylserine (PtdSer), and in the endoplasmic reticulum by fusion of CDP-ethanolamine and diacylglycerol. PtdEtn in the mitochondrion is synthesized by a PtdSer decarboxylase (TgPSD1mt) of the type I class. TgPSD1mt harbors a targeting peptide at its N-terminus that is required for the mitochondrial localization but not for the catalytic activity. Ablation of TgPSD1mt expression caused up to 45% impairment in the parasite growth. The PtdEtn content of the parasite mutant was unaffected however, suggesting the presence of compensatory mechanisms. Indeed, metabolic labeling revealed an increased usage of ethanolamine for PtdEtn synthesis by the mutant strain, and depletion of nutrient exacerbated the growth defect (~56%), which was partially restored by ethanolamine. Further, the survival and residual growth of the TgPSD1mt mutant in the nutrient-depleted medium indicated additional routes of PtdEtn biogenesis such as acquisition of host-derived lipid. Collectively, these results demonstrate a metabolic cooperativity between the parasite organelles, which ensures a sustained lipid synthesis, survival and growth of T. gondii in varying nutritional milieus.

KEYWORDS:

Host-pathogen interactions, Membrane biogenesis, Microbiology, Parasite metabolism, Parasitology, Phosphatidylethanolamine, phosphatidylserine decarboxylase

PMID:

 

24429285

 

[PubMed - as supplied by publisher] 

Characterization of Toxoplasma gondii subtelomeric-like regions

BMC Genomics. 2014 Jan 13;15(1):21. [Epub ahead of print]

Characterization of Toxoplasma gondii subtelomeric-like regions: identification of a long-range compositional bias that is also associated with gene-poor regions

Dalmasso MC, Carmona SJ, Angel SO, Agüuero F.

Abstract

BACKGROUND:

Chromosome ends are composed of telomeric repeats and subtelomeric regions, which are patchworks of genes interspersed with repeated elements. Although chromosome ends display similar arrangements in different species, their sequences are highly divergent. In addition, these regions display a particular nucleosomal composition and bind specific factors, therefore producing a special kind of heterochromatin. Using data from currently available draft genomes we have characterized these putative Telomeric Associated Sequences in Toxoplasma gondii.

RESULTS:

An all-vs-all pairwise comparison of T. gondii assembled chromosomes revealed the presence of conserved regions of ~ 30 Kb located near the ends of 9 of the 14 chromosomes of the genome of the ME49 strain. Sequence similarity among these regions is ~ 70%, and they are also highly conserved in the GT1 and VEG strains. However, they are unique to Toxoplasma with no detectable similarity in other Apicomplexan parasites. The internal structure of these sequences consists of 3 repetitive regions separated by high-complexity sequences without annotated genes, except for a gene from the Toxoplasma Specific Family. ChIP-qPCR experiments showed that nucleosomes associated to these sequences are enriched in histone H4 monomethylated at K20 (H4K20me1), and the histone variant H2A.X, suggesting that they are silenced sequences (heterochromatin). A detailed characterization of the base composition of these sequences, led us to identify a strong long-range compositional bias, which was similar to that observed in other genomic silenced fragments such as those containing centromeric sequences, and was negatively correlated to gene density.

CONCLUSIONS:

We identified and characterized a region present in most Toxoplasma assembled chromosomes. Based on their location, sequence features, and nucleosomal markers we propose that these might be part of subtelomeric regions of T. gondii. The identified regions display a unique trinucleotide compositional bias, which is shared (despite the lack of any detectable sequence similarity) with other silenced sequences, such as those making up the chromosome centromeres. We also identified other genomic regions with this compositional bias (but no detectable sequence similarity) that might be functionally similar.

PMID:

24417889

[PubMed - as supplied by publisher]

Am J Alzheimers Dis Other Demen. 2014 Jan 10. [Epub ahead of print]

Possible Link Between Toxoplasma Gondii and the Anosmia Associated With Neurodegenerative Diseases

Prandota J.

Toxoplasma gondii is an intracellular protozoan infecting 30% to 50% of global human population. Recently, it was suggested that chronic latent neuroinflammation caused by the parasite may be responsible for the development of several neurodegenerative diseases manifesting with the loss of smell. Studies in animals inoculated with the parasite revealed cysts in various regions of the brain, including olfactory bulb. Development of behavioral changes was paralleled by the preferential persistence of cysts in defined anatomic structures of the brain, depending on the host, strain of the parasite, its virulence, and route of inoculation. Olfactory dysfunction reported in Alzheimer's disease, multiple sclerosis, and schizophrenia was frequently associated with the significantly increased serum anti-T gondii immunoglobulin G antibody levels. Damage of the olfactory system may be also at least in part responsible for the development of depression because T gondii infection worsened mood in such patients, and the olfactory bulbectomized rat serves as a model of depression.

KEYWORDS:

anosmia, autoimmune diseases, cerebral toxoplasmosis, depression, impaired smell, neurodegeneration, olfaction

PMID:

24413543

[PubMed - as supplied by publisher]

Prog Retin Eye Res. 2014 Jan 8. pii: S1350-9462(13)00084-0. doi: 10.1016/j.preteyeres.2013.12.005. [Epub ahead of print]

Ocular Toxoplasmosis Past, present and new aspects of an old disease

Maenz M¹, Schlüter D², Liesenfeld O³, Schares G⁴, Gross U⁵, Pleyer U⁶.

 

Ocular toxoplasmosis (OT) is considered the most frequent form of infectious posterior uveitis and is caused by the protozoan parasite Toxoplasma gondii. The resulting vision loss frequently incapacitates patients and places a considerable socio-economic burden on societies in particular in developing countries. Although, toxoplasmic retinochoroiditis is a world-wide phenomenon stark regional differences with regard to prevalence and presumably route of infection exist. This review will discuss our current clinical understanding of OT including typical and atypical manifestations, patient characteristics which influence the course of disease and treatment options. Even though, congenital and acquired OT are not regarded as separate entities, certain differences exist, which will be assessed and evaluated in detail. A strong focus is laid on the disease causing parasite T. gondii, since solving the mystery of OT aetiology and the development of improved therapies will not be possibly with clinical science alone, but rather requires a precise understanding of parasitological and immunological pathomechanisms. Additionally, the biology and genetics of T. gondii form the foundation for novel and sophisticated diagnostic methods. Scientific advances in the recent years have shed some light on the different role of T. gondii strains with regard to OT manifestation and severity of disease. Genetic and environmental factors influencing OT will be presented and commonalities between OT and toxoplasmic encephalitis will be briefly discussed. Furthermore, the laboratory tools to study OT are crucial in our understanding of OT. In vivo and in vitro experimental approaches will be summarised and evaluated extensively. Finally, a brief outlook is given in which direction OT research should be headed in the future.
Copyright © 2013. Published by Elsevier Ltd.

PMID:

24412517

[PubMed - as supplied by publisher]

Front Public Health. 2013 Dec 25;1:73. doi: 10.3389/fpubh.2013.00073.

A Positive Association between T. gondii Seropositivity and Obesity

Reeves GM¹, Mazaheri S², Snitker S³, Langenberg P⁴, Giegling I⁵, Hartmann AM⁵, Konte B⁵, Friedl M⁵, Okusaga O⁶, Groer MW⁷, Mangge H⁸, Weghuber D⁹, Allison DB¹⁰, Rujescu D⁵, Postolache TT¹¹.

Abstract

Obesity is a global public health problem that is linked with morbidity, mortality, and functional limitations and has limited options for sustained interventions. Novel targets for prevention and intervention require further research into the pathogenesis of obesity. Consistently, elevated markers of inflammation have been reported in association with obesity, but their causes and consequences are not well understood. An emerging field of research has investigated the association of infections and environmental pathogens with obesity, potential causes of low grade inflammation that may mediate obesity risk. In this study, we estimate the possible association between Toxoplasma gondii (T. gondii) infection and obesity in a sample of 999 psychiatrically healthy adults. Individuals with psychiatric conditions, including personality disorders, were excluded because of the association between positive serology to T. gondii and various forms of serious mental illness that have a strong association with obesity. In our sample, individuals with positive T. gondii serology had twice the odds of being obese compared to seronegative individuals (p = 0.01). Further, individuals who were obese had significant higher T. gondii IgG titers compared to individuals who were non-obese. Latent T. gondii infection is very common worldwide, so potential public health interventions related to this parasite can have a high impact on associated health concerns.

KEYWORDS:

Toxoplasma gondii, body weight, inflammation, obesity, parasitic infection

PMID:

24400300

[PubMed]

Benzimidazole based drugs against T. gondii

Bioorg Med Chem Lett. 2013 Dec 22. pii: S0960-894X(13)01450-9. doi: 10.1016/j.bmcl.2013.12.066. [Epub ahead of print]

The benzimidazole based drugs show good activity against T. gondii but poor activity against its proposed enoyl reductase enzyme target

Wilkinson C¹, McPhillie MJ², Zhou Y³, Woods S⁴, Afanador GA⁵, Rawson S¹, Khaliq F⁴, Prigge ST⁵, Roberts CW⁴, Rice DW², McLeod R³, Fishwick CW⁶, Muench SP⁷.

Abstract

The enoyl acyl-carrier protein reductase (ENR) enzyme of the apicomplexan parasite family has been intensely studied for antiparasitic drug design for over a decade, with the most potent inhibitors targeting the NAD⁺ bound form of the enzyme. However, the higher affinity for the NADH co-factor over NAD⁺ and its availability in the natural environment makes the NADH complex form of ENR an attractive target. Herein, we have examined a benzimidazole family of inhibitors which target the NADH form of Francisella ENR, but despite good efficacy against Toxoplasma gondii, the IC₅₀ for T. gondii ENR is poor, with no inhibitory activity at 1μM. Moreover similar benzimidazole scaffolds are potent against fungi which lack the ENR enzyme and as such we believe that there may be significant off target effects for this family of inhibitors.
Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.

KEYWORDS:

Benzimidazole, Enoyl reductase, Toxoplasma, Triclosan

PMID:

24398298

[PubMed - as supplied by publisher]

PLoS Pathog. 2014 Jan;10(1):e1003830. doi: 10.1371/journal.ppat.1003830. Epub 2014 Jan 2.

Lysine Acetyltransferase GCN5b Interacts with AP2 Factors and Is Required for Toxoplasma gondii Proliferation

Wang J1, Dixon SE1, Ting LM2, Liu TK1, Jeffers V1, Croken MM2, Calloway M3, Cannella D4, Ali Hakimi M4, Kim K2, Sullivan WJ Jr5.

Author information

Abstract

Histone acetylation has been linked to developmental changes in gene expression and is a validated drug target of apicomplexan parasites, but little is known about the roles of individual histone modifying enzymes and how they are recruited to target genes. The protozoan parasite Toxoplasma gondii (phylum Apicomplexa) is unusual among invertebrates in possessing two GCN5-family lysine acetyltransferases (KATs). While GCN5a is required for gene expression in response to alkaline stress, this KAT is dispensable for parasite proliferation in normal culture conditions. In contrast, GCN5b cannot be disrupted, suggesting it is essential for Toxoplasma viability. To further explore the function of GCN5b, we generated clonal parasites expressing an inducible HA-tagged dominant-negative form of GCN5b containing a point mutation that ablates enzymatic activity (E703G). Stabilization of this dominant-negative GCN5b was mediated through ligand-binding to a destabilization domain (dd) fused to the protein. Induced accumulation of the ddHAGCN5b(E703G) protein led to a rapid arrest in parasite replication. Growth arrest was accompanied by a decrease in histone H3 acetylation at specific lysine residues as well as reduced expression of GCN5b target genes in GCN5b(E703G) parasites, which were identified using chromatin immunoprecipitation coupled with microarray hybridization (ChIP-chip). Proteomics studies revealed that GCN5b interacts with AP2-domain proteins, apicomplexan plant-like transcription factors, as well as a "core complex" that includes the co-activator ADA2-A, TFIID subunits, LEO1 polymerase-associated factor (Paf1) subunit, and RRM proteins. The dominant-negative phenotype of ddHAGCN5b(E703G) parasites, considered with the proteomics and ChIP-chip data, indicate that GCN5b plays a central role in transcriptional and chromatin remodeling complexes. We conclude that GCN5b has a non-redundant and indispensable role in regulating gene expression required during the Toxoplasma lytic cycle.

PMID:

 

24391497

 

[PubMed - in process] 

Infect Immun. 2014 Jan 6. [Epub ahead of print]

Toxoplasma gondii upregulates interleukin-12 to prevent Plasmodium berghei-induced experimental cerebral malaria

Settles EW, Moser LA, Harris TH, Knoll LJ.

Author information

Abstract

A pre-existing chronic infection with the parasite Toxoplasma gondii has previously been shown to protect mice against subsequent viral, bacterial or protozoal infections. Here we show that a chronic T. gondii infection can prevent Plasmodium berghei ANKA-induced experimental cerebral malaria (ECM) in C57BL/6 mice. Treatment with soluble T. gondii antigens (STAg) reduced parasite sequestration and T cell infiltration in the brains of P. berghei infected mice. Administration of STAg also preserved blood brain barrier function, reduced ECM symptoms and significantly decreased mortality. STAg treatment 24 hours post P. berghei infection led to a rapid increase in serum levels of interleukin (IL)-12 and interferon-γ (IFN-γ). By five days after P. berghei infection, STAg treated mice had reduced IFN-γ levels compared to mock treated mice, suggesting that reductions in IFN-γ at the time of ECM onset protected against lethality. Using IL-10 and IL-12βR deficient mice, we found that STAg-induced protection from ECM is IL-10-independent but IL-12-dependent. Treatment of P. berghei infected mice with recombinant IL-12 significantly decreased parasitemia and mortality. These data suggest that IL-12, either induced by STAg or injected as a recombinant protein, mediates protection from ECM-associated pathology potentially through early induction of IFN-γ and reduction in parasitemia. These results highlight the importance of early IL-12 induction in protection against ECM.

PMID:

 

24396042

 

[PubMed - as supplied by publisher]

Proc Natl Acad Sci U S A. 2014 Jan 3. [Epub ahead of print]

Toxoplasma GRA7 effector increases turnover of immunity-related GTPases and contributes to acute virulence in the mouse

Alaganan A, Fentress SJ, Tang K, Wang Q, Sibley LD.

Author information

Abstract

The intracellular parasite Toxoplasma gondii enjoys a wide host range and is adept at surviving in both naive and activated macrophages. Previous studies have emphasized the importance of the active serine-threonine protein kinase rhoptry protein 18 (ROP18), which targets immunity-related GTPases (IRGs), in mediating macrophage survival and acute virulence of T. gondii in mice. Here, we demonstrate that ROP18 exists in a complex with the pseudokinases rhoptry proteins 8 and 2 (ROP8/2) and dense granule protein 7 (GRA7). Individual deletion mutant gra7 or rop18 was partially attenuated for virulence in mice, whereas the combined gra7rop18 mutant was avirulent, suggesting these proteins act together in the same pathway. The virulence defect of the double mutant was mirrored by increased recruitment of IRGs and clearance of the parasite in IFN-γ-activated macrophages in vitro. GRA7 was shown to recognize a conserved feature of IRGs, binding directly to the active dimer of immunity-related GTPase a6 in a GTP-dependent manner. Binding of GRA7 to immunity-related GTPase a6 led to enhanced polymerization, rapid turnover, and eventual disassembly. Collectively, these studies suggest that ROP18 and GRA7 act in a complex to target IRGs by distinct mechanisms that are synergistic.

KEYWORDS:

cooperative polymerization, innate immunity, pathogenesis

PMID:

 

24390541

 

[PubMed - as supplied by publisher]

PLoS One. 2013 Dec 18;8(12):e82477. doi: 10.1371/journal.pone.0082477.

A New Pathogen Transmission Mechanism in the Ocean: The Case of Sea Otter Exposure to the Land-Parasite Toxoplasma gondii

Mazzillo FF1, Shapiro K2, Silver MW1.

Author information

Abstract

Toxoplasma gondii is a land-derived parasite that infects humans and marine mammals. Infections are a significant cause of mortality for endangered southern sea otters (Enhydra lutris nereis), but the transmission mechanism is poorly understood. Otter exposure to T. gondii has been linked to the consumption of marine turban snails in kelp (Macrocystis pyrifera) forests. It is unknown how turban snails acquire oocysts, as snails scrape food particles attached to surfaces, whereas T. gondii oocysts enter kelp beds as suspended particles via runoff. We hypothesized that waterborne T. gondii oocysts attach to kelp surfaces when encountering exopolymer substances (EPS) forming the sticky matrix of biofilms on kelp, and thus become available to snails. Results of a dietary composition analysis of field-collected snails and of kelp biofilm indicate that snails graze the dense kelp-biofilm assemblage composed of pennate diatoms and bacteria inserted within the EPS gel-like matrix. To test whether oocysts attach to kelp blades via EPS, we designed a laboratory experiment simulating the kelp forest canopy in tanks spiked with T. gondii surrogate microspheres and controlled for EPS and transparent exopolymer particles (TEP - the particulate form of EPS). On average, 19% and 31% of surrogates were detected attached to kelp surfaces covered with EPS in unfiltered and filtered seawater treatments, respectively. The presence of TEP in the seawater did not increase surrogate attachment. These findings support a novel transport mechanism of T. gondii oocysts: as oocysts enter the kelp forest canopy, a portion adheres to the sticky kelp biofilms. Snails grazing this biofilm encounter oocysts as 'bycatch' and thereby deliver the parasite to sea otters that prey upon snails. This novel mechanism can have health implications beyond T. gondii and otters, as a similar route of pathogen transmission may be implicated with other waterborne pathogens to marine wildlife and humans consuming biofilm-feeding invertebrates.

PMID:

 

24386100

 

[PubMed - in process] 

PMCID:

 

PMC3867372

 

Cyst Wall Protein CST1 Is Critical for Cyst Wall Integrity and Promotes Bradyzoite Persistence

PLoS Pathog. 2013 Dec;9(12):e1003823. doi: 10.1371/journal.ppat.1003823. Epub 2013 Dec 26.

The Toxoplasma gondii Cyst Wall Protein CST1 Is Critical for Cyst Wall Integrity and Promotes Bradyzoite Persistence

Tomita T1, Bzik DJ2, Ma YF1, Fox BA2, Markillie LM3, Taylor RC3, Kim K4, Weiss LM5.

Author information

Abstract

Toxoplasma gondii infects up to one third of the world's population. A key to the success of T. gondii as a parasite is its ability to persist for the life of its host as bradyzoites within tissue cysts. The glycosylated cyst wall is the key structural feature that facilitates persistence and oral transmission of this parasite. Because most of the antibodies and reagents that recognize the cyst wall recognize carbohydrates, identification of the components of the cyst wall has been technically challenging. We have identified CST1 (TGME49_064660) as a 250 kDa SRS (SAG1 related sequence) domain protein with a large mucin-like domain. CST1 is responsible for the Dolichos biflorus Agglutinin (DBA) lectin binding characteristic of T. gondii cysts. Deletion of CST1 results in reduced cyst number and a fragile brain cyst phenotype characterized by a thinning and disruption of the underlying region of the cyst wall. These defects are reversed by complementation of CST1. Additional complementation experiments demonstrate that the CST1-mucin domain is necessary for the formation of a normal cyst wall structure, the ability of the cyst to resist mechanical stress, and binding of DBA to the cyst wall. RNA-seq transcriptome analysis demonstrated dysregulation of bradyzoite genes within the various cst1 mutants. These results indicate that CST1 functions as a key structural component that confers essential sturdiness to the T. gondii tissue cyst critical for persistence of bradyzoite forms.

PMID:

 

24385904

 

[PubMed - in process] 

PMCID:

 

PMC3873430

 

Nat Rev Microbiol. 2014 Jan 2. doi: 10.1038/nrmicro3184. [Epub ahead of print]

Cell division in apicomplexan parasites

Francia ME1, Striepen B2.

Author information

Abstract

Toxoplasma gondii and Plasmodium falciparum are important human pathogens. These parasites and many of their apicomplexan relatives undergo a complex developmental process in the cells of their hosts, which includes genome replication, cell division and the assembly of new invasive stages. Apicomplexan cell cycle progression is both globally and locally regulated. Global regulation is carried out throughout the cytoplasm by diffusible factors that include cell cycle-specific kinases, cyclins and transcription factors. Local regulation acts on individual nuclei and daughter cells that are developing inside the mother cell. We propose that the centrosome is a master regulator that physically tethers cellular components and that provides spatial and temporal control of apicomplexan cell division.

PMID:

 

24384598

 

[PubMed - as supplied by publisher]

Monsters Inside Me: Congenital Toxoplasmosis

This episode of "Monsters Inside Me" features a case of congenital toxoplasmosis: http://www.youtube.com/watch?v=dD_Eo-wL3Ns

J Infect. 2014 Jan;68 Suppl 1:S125-33. doi: 10.1016/j.jinf.2013.09.023. Epub 2013 Oct 9.

It is not only the cat that did it: How to prevent and treat congenital toxoplasmosis

Robert-Gangneux F.

Author information

Abstract

The apicomplexan parasite Toxoplasma gondii was discovered a little over one hundred years ago and was soon recognized as a pathogen responsible for congenital infection. But detailed understanding of its epidemiology emerged only after 1970 with the discovery of its life cycle. In the last ten years, high resolution molecular tools have allowed the characterization of various strain types with different virulence patterns, and current studies are exploring the distribution of these different genotypes. In parallel, sophisticated diagnostic tools have been developed and awareness of disease burden has led some European countries with high prevalence rates to implement screening of pregnant women. In this article, the screening options and therapies used to prevent congenital toxoplasmosis are dissected in the light of recent data from cohort studies and other epidemiological data.

Copyright © 2013 The British Infection Association. Published by Elsevier Ltd. All rights reserved.

KEYWORDS:

Congenital toxoplasmosis, Epidemiology, Pregnancy, Prevention, Treatment

PMID:

 

24119928

Cell Microbiol. 2013 Dec 24. doi: 10.1111/cmi.12255. [Epub ahead of print]

Toxoplasma exports dense granule proteins beyond the vacuole to the host cell nucleus and rewires the host genome expression

Bougdour A, Tardieux I, Hakimi MA.

Author information

Abstract

Toxoplasma gondii is the most widespread apicomplexan parasite and occupies a large spectrum of niches by infecting virtually any warm-blooded animals. As an obligate intracellular parasite, Toxoplasma has evolved a repertoire of strategies to fine-tune the cellular environment in an optimal way to promote growth and persistence in host tissues hence increasing the chance to be transmitted to new hosts. Short and long-term intracellular survival is associated with Toxoplasma ability to both evade the host deleterious immune defenses and to stimulate a beneficial immune balance by governing host cell gene expression. It is only recently that parasite proteins responsible for driving these transcriptional changes have been identified. While proteins contained in the apical secretory Rhoptry organelle have already been identified as bona fide secreted effectors that divert host signaling pathways, recent findings revealed that dense granule proteins should be added to the growing list of effectors as they reach the host cell cytoplasm and nucleus and target various host cell pathways in the course of cell infection. Herein, we emphasize on a novel subfamily of dense granule resident proteins, exemplified with the GRA16 and GRA24 members we recently discovered as both are exported beyond the vacuole-containing parasites and reach the host cell nucleus to reshape the host genome expression.

This article is protected by copyright. All rights reserved.

PMID:

 

24373221

Trends Parasitol. 2014 Jan;30(1):1-3. doi: 10.1016/j.pt.2013.09.006.

Parasites and food: ripe for exploitation

Thompson RC.

Author information

Abstract

Parasites are often exploited for emotive or political purposes. This is especially so for a number of foodborne parasitic zoonoses, where this exploitation may not necessarily best serve the public good.

Copyright © 2013 Elsevier Ltd. All rights reserved.

KEYWORDS:

Taenia solium, Toxoplasma, Trichinella, foodborne, media, politics

PMID:

 

24373805