Thursday, April 17, 2014

Effectiveness of a novel immunogenic nanoparticle platform for Toxoplasma peptide vaccine in HLA transgenic mice

2014 Apr 12. pii: S0264-410X(14)00483-6. doi: 10.1016/j.vaccine.2014.03.092. [Epub ahead of print]

Effectiveness of a novel immunogenic nanoparticle platform for Toxoplasma peptide vaccine in HLA transgenic mice

 

Abstract

We created and produced a novel self-assembling nanoparticle platform for delivery of peptide epitopes that induces CD8+ and CD4+T cells that are protective against Toxoplasma gondii infection. These self-assembling polypeptide nanoparticles (SAPNs) are composed of linear peptide (LP) monomers which contain two coiled-coil oligomerization domains, the dense granule 7 (GRA720-28 LPQFATAAT) peptide and a universal CD4+T cell epitope (derived from PADRE). Purified LPs assemble into nanoparticles with icosahedral symmetry, similar to the capsids of small viruses. These particles were evaluated for their efficacy in eliciting IFN-γ by splenocytes of HLA-B*0702 transgenic mice and for their ability to protect against subsequent T. gondii challenge. This work demonstrates the feasibility of using this platform approach with a CD8+ epitope that binds HLA-B7 and tests the biological activity of potentially protective peptides restricted by human major histocompatibility complex (HLA) class I molecules in HLA transgenic mice.
Copyright © 2014 Elsevier Ltd. All rights reserved.

KEYWORDS:

HLA-B7, Nanoparticles, Toxoplasma gondii, Vaccine
PMID:
24736000
[PubMed - as supplied by publisher]

Disruption of Lipid Rafts Interferes with the Interaction of Toxoplasma gondii with Macrophages and Epithelial Cells

2013;2013:687835. doi: 10.1155/2014/687835. Epub 2014 Mar 9.

Disruption of Lipid Rafts Interferes with the Interaction of Toxoplasma gondii with Macrophages and Epithelial Cells

 

Abstract

The intracellular parasite Toxoplasma gondii can penetrate any warm-blooded animal cell. Conserved molecular assemblies of host cell plasma membranes should be involved in the parasite-host cell recognition. Lipid rafts are well-conserved membrane microdomains that contain high concentrations of cholesterol, sphingolipids, glycosylphosphatidylinositol, GPI-anchored proteins, and dually acylated proteins such as members of the Src family of tyrosine kinases. Disturbing lipid rafts of mouse peritoneal macrophages and epithelial cells of the lineage LLC-MK2 with methyl-beta cyclodextrin (M β CD) and filipin, which interfere with cholesterol or lidocaine, significantly inhibited internalization of T. gondii in both cell types, although adhesion remained unaffected in macrophages and decreased only in LLC-MK2 cells. Scanning and transmission electron microscopy confirmed these observations. Results are discussed in terms of the original role of macrophages as professional phagocytes versus the LLC-MK2 cell lineage originated from kidney epithelial cells.
PMID:
24734239
[PubMed - in process]

Wednesday, April 16, 2014

Avirulent strains of Toxoplasma gondii infect macrophages by active invasion from the phagosome

2014 Apr 14. [Epub ahead of print]

Avirulent strains of Toxoplasma gondii infect macrophages by active invasion from the phagosome

 

Abstract

Unlike most intracellular pathogens that gain access into host cells through endocytic pathways, Toxoplasma gondii initiates infection at the cell surface by active penetration through a moving junction and subsequent formation of a parasitophorous vacuole. Here, we describe a noncanonical pathway for T. gondii infection of macrophages, in which parasites are initially internalized through phagocytosis, and then actively invade from within a phagosomal compartment to form a parasitophorous vacuole. This phagosome to vacuole invasion (PTVI) pathway may represent an intermediary link between the endocytic and the penetrative routes for host cell entry by intracellular pathogens. The PTVI pathway is preferentially used by avirulent strains of T. gondii and confers an infectious advantage over virulent strains for macrophage tropism.

KEYWORDS:

Trojan horse, apicomplexa, phagocytes, virulence
PMID:
24733931
[PubMed - as supplied by publisher]

Isolation and molecular characterization of the shikimate dehydrogenase domain from the Toxoplasma gondii AROM complex

2014 Apr 11. pii: S0166-6851(14)00041-3. doi: 10.1016/j.molbiopara.2014.04.002. [Epub ahead of print]

Isolation and molecular characterization of the shikimate dehydrogenase domain from the Toxoplasma gondii AROM complex

Abstract

The apicomplexan parasite Toxoplasma gondii, the etiologic agent of toxoplasmosis, is estimated to infect 10-80% of different human populations. T. gondii encodes a large pentafunctional polypeptide known as the AROM complex which catalyzes five reactions in the shikimate pathway, a metabolic pathway required for the biosynthesis of the aromatic amino acids and a promising target for anti-parasitic agents. Here, we present the isolation, cloning and kinetic characterization of the shikimate dehydrogenase domain (TgSDH) from the T. gondii AROM complex. Recombinant TgSDH catalyzed the NADP+-dependent oxidation of shikimate in the absence of the remaining AROM domains and was sensitive to inhibition by a previously identified SDH inhibitor. Analysis of the TgSDH amino acid sequence revealed a number of novel insertions not found in SDH homologs from other organisms. Nevertheless, a three-dimensional structural model of TgSDH predicts a high level of conservation in the 'core' structure of the enzyme.
Copyright © 2014. Published by Elsevier B.V.

KEYWORDS:

AROM complex, Enzyme inhibition, Enzyme kinetics, Shikimate dehydrogenase, Toxoplasma gondii, shikimate pathway
PMID:
24731949
[PubMed - as supplied by publisher]

Saturday, April 12, 2014

Parasite Fate and Involvement of Infected Cells in the Induction of CD4+ and CD8+ T Cell Responses to Toxoplasma gondii

 2014 Apr 10;10(4):e1004047. doi: 10.1371/journal.ppat.1004047. eCollection 2014.

Parasite Fate and Involvement of Infected Cells in the Induction of CD4+ and CD8+ T Cell Responses to Toxoplasma gondii

Abstract

During infection with the intracellular parasite Toxoplasma gondii, the presentation of parasite-derived antigens to CD4+ and CD8+ T cells is essential for long-term resistance to this pathogen. Fundamental questions remain regarding the roles of phagocytosis and active invasion in the events that lead to the processing and presentation of parasite antigens. To understand the most proximal events in this process, an attenuated non-replicating strain of T. gondii (the cpsII strain) was combined with a cytometry-based approach to distinguish active invasion from phagocytic uptake. In vivo studies revealed that T. gondii disproportionately infected dendritic cells and macrophages, and that infected dendritic cells and macrophages displayed an activated phenotype characterized by enhanced levels of CD86 compared to cells that had phagocytosed the parasite, thus suggesting a role for these cells in priming naïve T cells. Indeed, dendritic cells were required for optimal CD4+ and CD8+ T cell responses, and the phagocytosis of heat-killed or invasion-blocked parasites was not sufficient to induce T cell responses. Rather, the selective transfer of cpsII-infected dendritic cells or macrophages (but not those that had phagocytosed the parasite) to naïve mice potently induced CD4+ and CD8+ T cell responses, and conferred protection against challenge with virulent T. gondii. Collectively, these results point toward a critical role for actively infected host cells in initiating T. gondii-specific CD4+ and CD8+ T cell responses.
PMID:
 
24722202
 
[PubMed - in process]

Border maneuvers: deployment of mucosal immune defenses against Toxoplasma gondii

 2014 Apr 9. doi: 10.1038/mi.2014.25. [Epub ahead of print]

Border maneuvers: deployment of mucosal immune defenses against Toxoplasma gondii

Abstract

Toxoplasma gondii is a highly prevalent protozoan pathogen that is transmitted through oral ingestion of infectious cysts. As such, mucosal immune defenses in the intestine constitute the first and arguably most important line of resistance against the parasite. The response to infection is now understood to involve complex three-way interactions between Toxoplasma, the mucosal immune system, and the host intestinal microbiota. Productive outcome of these interactions ensures resolution of infection in the intestinal mucosa. Nonsuccessful outcome may result in emergence of proinflammatory damage that can spell death for the host. Here, we discuss new advances in our understanding of the mechanisms underpinning these disparate outcomes, with particular reference to initiators, effectors, and regulators of mucosal immunity stimulated by Toxoplasma in the intestine.Mucosal Immunology advance online publication, 9 April 2014; doi:10.1038/mi.2014.25.
PMID:
 
24717355
 
[PubMed - as supplied by publisher]

Characterization of a homolog of DEAD-box RNA helicases in Toxoplasma gondii as a marker of cytoplasmic mRNP stress granules

 2014 Apr 5. pii: S0378-1119(14)00411-9. doi: 10.1016/j.gene.2014.04.011. [Epub ahead of print]

Characterization of a homolog of DEAD-box RNA helicases in Toxoplasma gondii as a marker of cytoplasmic mRNP stress granules

Abstract

Toxoplasma gondii is an obligate intracellular protozoan which infects one-third of the human population. Due to its high infection prevalence, Toxoplasma offers an ideal system for the study of host-parasite interaction. Similar to other eukaryotes, Toxoplasma maintains levels and localization of cytoplasmic mRNAs throughout its life cycle as part of a gene regulation network to meet all cellular and biochemical requirements. More recently, it was reported that the presence of cytoplasmic mRNA granules could contribute to the parasite pathogenesis and viability. Here we identified a novel Toxoplasma DEAD-box RNA helicase, referred to as Toxoplasma gondiiHomolog of DOZI (TgHoDI), because of its high homology (81%) to Plasmodium DOZI. TgHoDI is the functional ortholog of yeast DHH1, and its function was authenticated by complementation studies in Δdhh1 yeast strain. We demonstrated that TgHoDI is a marker of cytoplasmic RNA stress granules, which assemble when the parasites experience cellular stresses and translational arrest.
Copyright © 2014. Published by Elsevier B.V.

KEYWORDS:

DEAD-box RNA helicase, Environmental responses, Stress granules, Toxoplasma
PMID:
 
24709106
 
[PubMed - as supplied by publisher]

Toxoplasma gondii Seroprevalence in the United States 2009-2010 and Comparison with the Past Two Decades

 2014 Apr 7. [Epub ahead of print]

Toxoplasma gondii Seroprevalence in the United States 2009-2010 and Comparison with the Past Two Decades

Abstract

Toxoplasma gondii is a ubiquitous parasite that can cause neurologic and ocular disease. We tested sera from 7,072 people ≥ 6 years of age in the 2009-2010 National Health and Nutrition Examination Survey (NHANES) for immunoglobulin G antibodies and compared these results with two previous NHANES surveys. The overall T. gondii antibody seroprevalence among persons ≥ 6 years of age in 2009-2010 was 13.2% (95% confidence limit [CL] 11.8%, 14.5%) and age-adjusted seroprevalence was 12.4% (95% CL 11.1%, 13.7%); age-adjusted seroprevalence among women 15-44 years of age was 9.1% (95% CL 7.2%, 11.1%). In U.S. born persons 12-49 years of age, the age-adjusted T. gondii seroprevalence decreased from 14.1% (95% CL 12.7%, 15.5%) in NHANES III (1988-1994) to 9.0% (95% CL 7.6%, 10.5%) in NHANES 1999-2004 to 6.7% (95% CL 5.3%, 8.2%) in NHANES 2009-2010 (P < 0.001 linear trend). Although T. gondii antibody presence is still relatively common, the prevalence in the United States has continued to decline.
PMID:
 
24710615
 
[PubMed - as supplied by publisher]

GRA25 is a novel virulence factor of Toxoplasma gondii and influences the host immune response

 2014 Apr 7. [Epub ahead of print]

GRA25 is a novel virulence factor of Toxoplasma gondii and influences the host immune response

Abstract

The obligate intracellular parasite Toxoplasma gondii is able to infect a broad range of hosts and cell types due, in part, to the diverse arsenal of effectors it secretes into the host cell. Here, using genetic crosses between Type II and Type III Toxoplasma strains and QTL mapping of the changes they induce in macrophage gene expression, we identify a novel dense granule protein, GRA25. Encoded on chromosome IX, GRA25 is a phosphoprotein that is secreted outside of the parasites and is found within the parasitophorous vacuole. In vitro experiments with a Type II Δgra25 strain showed that macrophages infected with this strain secrete lower levels of CCL2 and CXCL1 compared to those infected with the wild type or complemented control parasites. In vivo experiments showed that mice infected with a Type II Δgra25 strain are able to survive an otherwise lethal dose of Toxoplasma tachyzoites, and complementation of the mutant with an ectopic copy of GRA25 largely rescues this phenotype. Interestingly, the Type II and Type III versions of GRA25 vary in endogenous expression; however, both are able to promote parasite expansion in vivo when expressed in a Type II Δgra25 strain. These data establish GRA25 as a novel virulence factor and immune modulator.
PMID:
 
24711568
 
[PubMed - as supplied by publisher]

New findings: Depression, suicide, and Toxoplasma gondii infection

 2014 Apr 8. doi: 10.1002/2327-6924.12129. [Epub ahead of print]

New findings: Depression, suicide, and Toxoplasma gondii infection

Abstract

PURPOSE:

This article provides an overview of the evidence of a potential pathophysiological relationship between depression, suicide, and the Toxoplasma gondii (T. gondii) infection. It discusses the role of inflammatory processes in depressive illness and the infection theory of psychiatric disease. It also provides guidelines for the screening, diagnosis, and treatment of depression for nurse practitioners (NPs).

DATA SOURCE:

A narrative review was conducted of the literature from PubMed, PsycINFO, and Google Scholar. References of identified articles were also reviewed.

CONCLUSIONS:

Seropositivity of the obligate intracellular protozoan parasite, T. gondii is related to various mental health disorders including schizophrenia, suicide attempt, depression, and other neuropsychiatric diseases. Depressive symptoms have been linked to interferon-γ (IFN-γ) blocking T. gondii growth by inducing indoleamine-2,3-dioxygenase (IDO) activation and tryptophan depletion, which results in a decrease of serotonin production in the brain. Although exposure to T. gondii was considered unlikely to reactivate in immune-competent individuals, new findings report that this reactivation may be triggered by immune imbalance.

IMPLICATIONS FOR PRACTICE:

NPs caring for patients with psychiatric illness need to understand the potential mechanisms associated with depression and the T. gondii infection in order to provide effective screening, treatment, and disease prevention.
©2014 The Author(s) ©2014 American Association of Nurse Practitioners.

KEYWORDS:

IDO, dopamine, proinflammatory cytokines, serotonin, tryptophan
PMID:
 
24715687
 
[PubMed - as supplied by publisher]

Astrocytes, microglia/macrophages, and neurons expressing Toll-like receptor 11 contribute to innate immunity against encephalitic Toxoplasma gondii infection

 2014 Apr 2. pii: S0306-4522(14)00272-3. doi: 10.1016/j.neuroscience.2014.03.049. [Epub ahead of print]

Astrocytes, microglia/macrophages, and neurons expressing Toll-like receptor 11 contribute to innate immunity against encephalitic Toxoplasma gondii infection

Abstract

Toll-like receptor 11 (TLR11) is a specific receptor for Toxoplasma gondii and uropathogenic Escherichia coli and has recently been identified in the mouse brain. In the present study, TLR11 gene expression was measured in the mouse brain by reverse-transcription PCR (RT-PCR). Furthermore, the TLR11 protein expression profile was evaluated in neuroglia and neurons throughout the encephalitic period (10, 20, and 30 days after inoculation) in mice with experimentally induced T. gondii infection. In the brains of experimental (n = 21) and control (n = 7) mice, TLR11, GFAP, cd11b, NeuN, TLR11/GFAP+, TLR11/cd11b+, and TLR11/NeuN+ cells were investigated using either indirect single- or double-labelling immunoperoxidase staining. The results indicated that TLR11 gene expression increased during chronic toxoplasmic encephalitis, and there was a variable degree of TLR11 immunopositivity among cd11b+, GFAP+, and NeuN+ cells in the brain. On the tenth day of infection, there was a significant increase in TLR11 protein and gene expression, which remained stable during the later stages of infection. In this experimental model, TLR11 expression was induced in astrocytes, neurons, and microglia/macrophages during the immune response to T. gondii infection.
Copyright © 2014. Published by Elsevier Ltd.

KEYWORDS:

Astrocyte, Microglia, Neuron, TLR11, Toxoplasma gondii
PMID:
 
24704432
 
[PubMed - as supplied by publisher]

Saturday, April 05, 2014

Protozoan HSP90-Heterocomplex: Molecular Interaction Network and Biological Significance

 2014 Mar 31. [Epub ahead of print]

Protozoan HSP90-Heterocomplex: Molecular Interaction Network and Biological Significance

Abstract

The HSP90 chaperone is a highly conserved protein from bacteria to higher eukaryotes. In eukaryotes, this chaperone participates in different large complexes, such as the HSP90 heterocomplex, which has important biological roles in cell homeostasis and differentiation. The HSP90-heterocomplex is also named the HSP90/HSP70 cycle because different co-chaperones (HIP, HSP40, HOP, p23, AHA1, immunophilins, PP5) participate in this complex by assembling sequentially, from the early to the mature complex. In this review, we analyze the conservation and relevance of HSP90 and the HSP90-heterocomplex in several protozoan parasites, with emphasis in Plasmodium spp., Toxoplasma spp., Leishmania spp. and Trypanosoma spp. In the last years, there has been an outburst of studies based on yeast two-hybrid methodology, co-immunoprecipitation-mass spectrometry and bioinformatics, which have generated a most comprehensive protein-protein interaction (PPI) network of HSP90 and its co-chaperones. This review analyzes the existing PPI networks of HSP90 and its co-chaperones of some protozoan parasites and discusses the usefulness of these powerful tools to analyze the biological role of the HSP90-heterocomplex in these parasites. The generation of a T. gondii HSP90 heterocomplex PPI network based on experimental data and a recent Plasmodium HSP90 heterocomplex PPI network are also included and discussed. As an example, the putative implication of nuclear transport and chromatin (histones and Sir2) as HSP90-heterocomplex interactors is here discussed.
PMID:
 
24694366
 
[PubMed - as supplied by publisher]

Autophagy activated by Toxoplasma gondii infection in turn facilitates Toxoplasma gondii proliferation

 2014 Apr 3. [Epub ahead of print]

Autophagy activated by Toxoplasma gondii infection in turn facilitates Toxoplasma gondii proliferation

Abstract

Autophagy was found to play an antimicrobial or antiparasitic role in the activation of host cells to defend against intracellular pathogens, at the same time, pathogens could compete with host cell and take advantage of autophagy to provide access for its proliferation, but there are few articles for studying the outcome of this competition between host cell and pathogens. Therefore, the aim of our study was to investigate the relationship between autophagy activated by Toxoplasma gondii (T. gondii) and proliferation of T. gondii affected by autophagy in vitro. Firstly, human embryonic fibroblasts (HEF) cells were infected with T. gondii for different times. The monodansylcadaverine (MDC) staining, acridine orange (AO) staining, punctuate GFP-LC3 distribution, and transmission electron microscopy (TEM) assays were conducted, and the results were consistent in showing that gondii infection could induce autophagy. Secondly, HEF cells were infected with T. gondii and treated with autophagy inhibitor bafilomycin A1 or inducer lithium chloride for different times. Giemsa staining was conducted, and the results exhibited that T. gondii infection-induced autophagy could in turn promote T. gondii proliferation. Simultaneously, the results of Giemsa staining also revealed that autophagy inhibitor could reduce the number of each cell infected with T. gondii and inhibit T. gondii proliferation. In contrast, autophagy inducer could increase the number of each cell infected with T. gondii and encourage T. gondii proliferation. Therefore, our study suggests that T. gondii infection could activate autophagy, and this autophagy could in turn facilitate T. gondii proliferation in HEF cells for limiting nutrients.
PMID:
 
24696274
 
[PubMed - as supplied by publisher]

Thursday, April 03, 2014

Characterization of TgPuf1, a member of the Puf family RNA-binding proteins from Toxoplasma gondii

2014 Mar 31;7(1):141. [Epub ahead of print]

Characterization of TgPuf1, a member of the Puf family RNA-binding proteins from Toxoplasma gondii

Abstract

BACKGROUND:

Puf proteins act as translational regulators and affect many cellular processes in a wide range of eukaryotic organisms. Although Puf proteins have been well characterized in many model systems, little is known about the structural and functional characteristics of Puf proteins in the parasite Toxoplasma gondii.

METHODS:

Using a combination of conventional molecular approaches, we generated endogenous TgPuf1 tagged with hemagglutinin (HA) epitope and investigated the TgPuf1 expression levels and localization in the tachyzoites and bradyzoites. We used RNA Electrophoretic Mobility Shfit Assay (EMSA) to determine whether the recombination TgPuf1 has conserverd RNA binding activity and specificity.

RESULTS:

TgPuf1 was expressed at a significantly higher level in bradyzoites than in tachyzoites. TgPuf1 protein was predominantly localized within the cytoplasm and showed a much more granular cytoplasmic staining pattern in bradyzoites. The recombinant Puf domain of TgPuf1 showed strong binding affinity to two RNA fragments containing Puf-binding motifs from other organisms as artificial target sequences. However, two point mutations in the core Puf-binding motif resulted in a significant reduction in binding affinity, indicating that TgPuf1 also binds to conserved Puf-binding motif.

CONCLUSIONS:

TgPuf1 appears to exhibit different expression levels in the tachyzoites and bradyzoites, suggesting that TgPuf1 may function in regulating the proliferation or/and differentiation that are important in providing parasites with the ability to respond rapidly to changes in environmental conditions. This study provides a starting point for elucidating the function of TgPuf1 during parasite development.
PMID:
24685055
[PubMed - as supplied by publisher]

TLR4 in Toxoplasmosis; friends or foe?

2014 Mar 28. pii: S0882-4010(14)00039-4. doi: 10.1016/j.micpath.2014.03.006. [Epub ahead of print]

TLR4 in Toxoplasmosis; friends or foe?

Abstract

Toxoplasma species are obligate intracellular protozoan which are responsible for induction of several forms of Toxoplasmosis in humans. The mechanisms responsible for the progression of the prolonged forms of Toxoplasmosis and associated pathologies are yet to be identified. However, previous studies proposed that immunological and genetic parameters may play important roles in the etiology and complexity of Toxoplasmosis. Pathogen recognition receptors (PRRs) recognise microbial antigens and induce immune responses against parasites, including toxoplasma species. Toll like receptors (TLRs) are PRRs which recognize toxoplasma as a pathogenic parasite and activate immune cells. It has been reported that the TLR4 is a critical innate immune cell receptor in toxoplasma detection and subsequently activates immune responses using either MYD88 or TRIF pathways. This review collates recent information regarding the role of TLR4 and its related signaling molecules with Toxoplasmosis.
Copyright © 2014. Published by Elsevier Ltd.

KEYWORDS:

Signaling molecule, TLR4, Toxoplasma, pathogen recognition receptor
PMID:
24685700
[PubMed - as supplied by publisher]

ALOX12 In Human Toxoplasmosis

2014 Mar 31. [Epub ahead of print]

ALOX12 In Human Toxoplasmosis

Abstract

ALOX12 is a gene encoding arachidonate 12-lipoxygenase (12-LOX), a member of a non-heme lipoxygenase family of dioxygenases. ALOX12 catalyzes the addition of oxygen onto arachidonic acid producing 12-hydroperoxyeicosatetraenoic acid, 12-HPETE, which can be reduced to eicosanoid, 12-HETE. 12-HETE acts in diverse cellular processes including catecholamine synthesis, vasoconstriction, neuronal function and inflammation. Consistent with effects on these fundamental mechanisms, allelic variants of ALOX12 are associated with diseases including schizophrenia, atherosclerosis and cancers without definition of mechanisms. Toxoplasma gondii is an apicomplexan parasite that causes morbidity and mortality and stimulates an innate and adaptive immune inflammatory reaction. Recently, it has been shown that a gene region known as Toxo1 is critical for susceptibility or resistance to T. gondii infection in rats. An orthologous gene region with ALOX12 centromeric is also present in humans. Herein, we report that the human ALOX12 gene has susceptibility alleles for human congenital toxoplasmosis (rs6502997 [P<0 .000309="" a="" acid="" alox12.="" alox12="" and="" arachidonic="" attenuated="" be="" been="" burden="" but="" cell="" cells.="" cells="" consequent="" critical="" death="" decreased="" demonstrate="" diseases.="" engineered="" expression="" findings="" genetically="" gondii="" greater="" has="" herein="" host="" human="" humans.="" important="" in="" increased.="" infection="" influences="" interference="" knockdown="" late="" lentivirus="" line.="" line="" monocytic="" now="" numerous="" of="" other="" p="" parasite="" plays="" progression="" responses="" resulted="" rna="" role="" rs312462="" rs434473="" rs6502998="" shown="" studies="" substrate="" suggest="" t.="" that="" the="" these="" to="" using="" was="" we="">
PMID:
24686056
[PubMed - as supplied by publisher]

Bumped Kinase Inhibitor 1294 Treats Established Toxoplasma gondii Infection

2014 Mar 31. [Epub ahead of print]

Bumped Kinase Inhibitor 1294 Treats Established Toxoplasma gondii Infection

Abstract

Toxoplasma gondii is a unicellular parasite that causes severe brain and eye disease. Current drugs for T. gondii are limited by toxicity. Bumped kinase inhibitors (BKI) selectively inhibit calcium-dependent protein kinases of the apicomplexan pathogens T. gondii, Cryptosporidia and Plasmodia. A lead anti-Toxoplasma BKI, 1294, has been developed to be metabolically stable and orally bioavailable. Herein, we demonstrate the oral efficacy of 1294 against toxoplasmosis in vivo.
PMID:
24687502
[PubMed - as supplied by publisher]

CRTAM controls residency of gut CD4+CD8+ T cells in the steady state and maintenance of gut CD4+ Th17 during parasitic infection

2014 Mar 31. [Epub ahead of print]

CRTAM controls residency of gut CD4+CD8+ T cells in the steady state and maintenance of gut CD4+ Th17 during parasitic infection

 

Abstract

Retention of lymphocytes in the intestinal mucosa requires specialized chemokine receptors and adhesion molecules. We find that both CD4+CD8+ and CD4+ T cells in the intestinal epithelium, as well as CD8+ T cells in the intestinal mucosa and mesenteric lymph nodes, express the cell adhesion molecule class I-restricted T cell-associated molecule (Crtam) upon activation, whereas the ligand of Crtam, cell adhesion molecule 1 (Cadm1), is expressed on gut CD103+DCs. Lack of Crtam-Cadm1 interactions in Crtam-/- and Cadm1-/- mice results in loss of CD4+CD8+ T cells, which arise from mucosal CD4+ T cells that acquire a CD8 lineage expression profile. After acute oral infection with Toxoplasma gondii, both WT and Crtam-/- mice mounted a robust TH1 response, but markedly fewer TH17 cells were present in the intestinal mucosa of Crtam-/- mice. The almost exclusive TH1 response in Crtam-/- mice resulted in more efficient control of intestinal T. gondii infection. Thus, Crtam-Cadm1 interactions have a major impact on the residency and maintenance of CD4+CD8+ T cells in the gut mucosa in the steady state. During pathogenic infection, Crtam-Cadm1 interactions regulate the dynamic equilibrium between newly formed CD4+ T cells and their retention in the gut, thereby shaping representation of disparate CD4+ T cell subsets and the overall quality of the CD4+ T cell response.
PMID:
24687959
[PubMed - as supplied by publisher]

Synergy of mIL-21 and mIL-15 in enhancing DNA vaccine efficacy against acute and chronic Toxoplasma gondii infection in mice

2014 Mar 29. pii: S0264-410X(14)00411-3. doi: 10.1016/j.vaccine.2014.03.042. [Epub ahead of print]

Synergy of mIL-21 and mIL-15 in enhancing DNA vaccine efficacy against acute and chronic Toxoplasma gondii infection in mice

 
The synergistic protective efficacy of murine interleukin 21 (mIL-21) and mIL-15 administrated with DNA vaccine against acute and chronic Toxoplasma gondii infection in mice was investigated using T. gondii MIC8 (TgMIC8) as a model. We cloned mIL-21 and mIL-15 from splenic tissues of Kunming mice, and constructed eukaryotic plasmid pVAX/mIL-15, pVAX/mIL-21, and pVAX/mIL-21/mIL-15, respectively. After immunizing with pVAX/TgMIC8 in the presence or absence of these cytokines, immune responses were analyzed using lymphoproliferative assay, cytokine and serum antibody measurements, flow cytometric surface markers on lymphocytes and protection against acute and chronic T. gondii infection. Mice receiving pVAX/TgMIC8 alone developed a strong humoral responses and Th1 type cellular immune responses, and showed an increase of CD4+ and CD8+ T cells compared with all the controls. Adding pVAX/mIL-21 to pVAX/TgMIC8 compared to pVAX/TgMIC8 resulted in only a slight increase in humoral and cellular immune responses, and this immune response was lower than that induced by the pVAX/mIL-15 combined with pVAX/TgMIC8. Co-administration of pVAX/mIL-21/mIL-15 combined with pVAX/TgMIC8 elicited the strongest humoral and cellular immune responses among all the groups, leading to significantly increased survival time against acute infection and the significant reduction of tissue cysts, compared to all the controls. Synergy of mIL-21 and mIL-15 can facilitate specific humoral as well as cellular immune responses elicited by DNA vaccine against acute and chronic T. gondii infection in mice.
Copyright © 2014. Published by Elsevier Ltd.

KEYWORDS:

DNA vaccine, Protective immunity, Synergy, TgMIC8, Toxoplasma gondii, Toxoplasmosis, mIL-15, mIL-21
PMID:
24690150
[PubMed - as supplied by publisher]

Treatment with interleukin-18 binding protein ameliorates Toxoplasma gondii-induced small intestinal pathology that is induced by bone marrow cell-derived interleukin-18

2012 Sep;2(3):249-57. doi: 10.1556/EuJMI.2.2012.3.11. Epub 2012 Sep 10.

Treatment with interleukin-18 binding protein ameliorates Toxoplasma gondii-induced small intestinal pathology that is induced by bone marrow cell-derived interleukin-18

Abstract

Peroral infection with Toxoplasma gondii results in a Th1-type immunopathology characterized by small intestinal necrosis and is dependent on IL-18. In the present study, we investigated whether treatment with IL-18 binding protein (IL-18bp) prevents ileal pathology. We observed increased expression of IL-18bp in intestinal biopsies of mice following infection. Whereas small intestines of control mice showed severe necrosis with complete destruction of the small intestinal architecture, mice treated with IL-18bp daily displayed only mild inflammatory changes including flattening of villi and edema in the space between the epithelium and lamina propria. Small intestinal parasite loads and concentrations of pro-inflammatory cytokines did not differ in control and IL-18bp-treated mice. Binding of IL-18 to immobilized IL-18bp revealed a remarkably slow dissociation rate, indicating high affinity. Using chimeric mice we observed that bone marrow-derived rather than stromal cells were the primary source of IL-18 that resulted in small intestinal pathology following peroral infection with T. gondii. In conclusion, the results presented here suggest that IL-18bp may be an effective and safe treatment for small intestinal inflammation. Antigen-presenting rather than epithelial cells appear to be the main source of IL-18 in T. gondii-induced small intestinal inflammation.

KEYWORDS:

IL-18, IL-18 binding protein, Toxoplasma gondii, ileitis, immunopathology
PMID:
24688772
[PubMed]

Shear Forces Enhance Toxoplasma gondii Tachyzoite Motility on Vascular Endothelium

2014 Apr 1;5(2). pii: e01111-13. doi: 10.1128/mBio.01111-13.

Shear Forces Enhance Toxoplasma gondii Tachyzoite Motility on Vascular Endothelium

Abstract

ABSTRACT Toxoplasma gondii is a highly successful parasite that infects approximately one-third of the human population and can cause fatal disease in immunocompromised individuals. Systemic parasite dissemination to organs such as the brain and eye is critical to pathogenesis. T. gondii can disseminate via the circulation, and both intracellular and extracellular modes of transport have been proposed. However, the processes by which extracellular tachyzoites adhere to and migrate across vascular endothelium under the conditions of rapidly flowing blood remain unknown. We used microfluidics and time-lapse fluorescence microscopy to examine the interactions between extracellular T. gondii and primary human endothelial cells under conditions of physiologic shear stress. Remarkably, tachyzoites adhered to and glided on human vascular endothelium under shear stress conditions. Compared to static conditions, shear stress enhanced T. gondii helical gliding, resulting in a significantly greater displacement, and increased the percentage of tachyzoites that invaded or migrated across the endothelium. The intensity of the shear forces (from 0.5 to 10 dynes/cm(2)) influenced both initial and sustained adhesion to endothelium. By examining tachyzoites deficient in the T. gondii adhesion protein MIC2, we found that MIC2 contributed to initial adhesion but was not required for adhesion strengthening. These data suggest that under fluidic conditions, T. gondii adhesion to endothelium may be mediated by a multistep cascade of interactions that is governed by unique combinations of adhesion molecules. This work provides novel information about tachyzoite interactions with vascular endothelium and contributes to our understanding of T. gondii dissemination in the infected host. IMPORTANCE Toxoplasma gondii is a global parasite pathogen that can cause fatal disease in immunocompromised individuals. An unresolved question is how the parasites circulate in the body to tissues to cause disease. T. gondii parasites are found in the bloodstream of infected animals and patients, and they have been shown to adhere to and cross the endothelial cells that line blood vessel walls. To investigate these interactions, we devised a microfluidic system to visualize parasites interacting with vascular endothelium under conditions similar to those found in the bloodstream. Interestingly, parasite migration was significantly influenced by the mechanical force of shear flow. Furthermore, we identified a role for the parasite surface protein MIC2 in the initial phase of adhesion. Our study is the first to document T. gondii interactions with endothelium under shear stress conditions and provides a foundation for future studies on the molecules that mediate parasite interaction with the vasculature.
PMID:
24692639
[PubMed - in process]

Saturday, March 29, 2014

The inner membrane complex sub-compartment proteins critical for replication of the apicomplexan parasite Toxoplasma gondii adopt a Pleckstrin homology fold

 2014 Mar 27. [Epub ahead of print]

The inner membrane complex sub-compartment proteins critical for replication of the apicomplexan parasite Toxoplasma gondii adopt a Pleckstrin homology fold

Abstract

Toxoplasma gondii, an apicomplexan parasite prevalent in developed nations, infects up to one third of the human population. The success of this parasite depends on several unique structures including an Inner Membrane Complex (IMC) that lines the interior of the plasma membrane and contains proteins important for gliding motility and replication. Of these proteins, the IMC Sub-compartment Proteins (ISPs) have recently been shown to play a role in asexual T. gondii daughter cell formation, yet the mechanism is unknown. Complicating mechanistic characterization of the ISPs is a lack of sequence identity with proteins of known structure or function. In support of elucidating the function of ISPs, we first determined the crystal structures of representative members TgISP1 and TgISP3 to a resolution of 2.10Å and 2.32Å, respectively. Structural analysis revealed that both ISPs adopt a Pleckstrin homology (PH) fold often associated with phospholipid binding or protein-protein interactions. Substitution of basic for hydrophobic residues in the region that overlays with phospholipid binding in related PH domains, however, suggests that ISPs do not retain phospholipid binding activity. Consistent with this observation, biochemical assays revealed no phospholipid binding activity. Interestingly, mapping of conserved surface residues combined with crystal packing analysis indicates that TgISPs have functionally repurposed the phospholipid-binding site likely to coordinate protein partners. Recruitment of larger protein complexes may also be aided through avidity-enhanced interactions resulting from multimerization of the ISPs. Overall, we propose a model where TgISPs recruit protein partners to the IMC to ensure correct progression of daughter cell formation.

KEYWORDS:

Apicomplexa, Cell division, Inner Membrane Complex, Parasite, Pleckstrin Homology Fold, Protein-protein interactions, Structural biology, Toxoplasma gondii, X-ray crystallography, endodyogeny
PMID:
 
24675080
 
[PubMed - as supplied by publisher]