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Braun L, Brenier-Pinchart MP, Yogavel M, Curt-Varesano A, Curt-Bertini RL, Hussain T, Kieffer-Jaquinod S, Coute Y, Pelloux H, Tardieux I, Sharma A, Belrhali H, Bougdour A, Hakimi MA. A Toxoplasma dense granule protein, GRA24, modulates the early immune response to infection by promoting a direct and sustained host p38 MAPK activation. ACTA ACUST UNITED AC 2013; 210:2071-86. [PMID: 24043761 PMCID: PMC3782045 DOI: 10.1084/jem.20130103] [Citation(s) in RCA: 187] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Toxoplasma gondii secretes a novel dense granule protein, GRA24, that traffics from the vacuole to the host cell nucleus where it prolongs p38a activation and correlates with proinflammatory cytokine production. Toxoplasma gondii, the causative agent of toxoplasmosis, is an obligate intracellular protozoan parasite that resides inside a parasitophorous vacuole. During infection, Toxoplasma actively remodels the transcriptome of its hosting cells with profound and coupled impact on the host immune response. We report that Toxoplasma secretes GRA24, a novel dense granule protein which traffics from the vacuole to the host cell nucleus. Once released into the host cell, GRA24 has the unique ability to trigger prolonged autophosphorylation and nuclear translocation of the host cell p38α MAP kinase. This noncanonical kinetics of p38α activation correlates with the up-regulation of the transcription factors Egr-1 and c-Fos and the correlated synthesis of key proinflammatory cytokines, including interleukin-12 and the chemokine MCP-1, both known to control early parasite replication in vivo. Remarkably, the GRA24–p38α complex is defined by peculiar structural features and uncovers a new regulatory signaling path distinct from the MAPK signaling cascade and otherwise commonly activated by stress-related stimuli or various intracellular microbes.
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Affiliation(s)
- Laurence Braun
- Centre National de la Recherche Scientifique (CNRS), UMR5163, Laboratoire Adaptation et Pathogénie des Microorganismes, F-38041 Grenoble, France
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152
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153
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MAP kinase phosphatase-2 plays a key role in the control of infection with Toxoplasma gondii by modulating iNOS and arginase-1 activities in mice. PLoS Pathog 2013; 9:e1003535. [PMID: 23966857 PMCID: PMC3744406 DOI: 10.1371/journal.ppat.1003535] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Accepted: 06/18/2013] [Indexed: 11/19/2022] Open
Abstract
The dual specific phosphatase, MAP kinase phosphatase-2 (MKP-2) has recently been demonstrated to negatively regulate macrophage arginase-1 expression, while at the same time to positively regulate iNOS expression. Consequently, MKP-2 is likely to play a significant role in the host interplay with intracellular pathogens. Here we demonstrate that MKP-2(-/-) mice on the C57BL/6 background have enhanced susceptibility compared with wild-type counterparts following infection with type-2 strains of Toxoplasma gondii as measured by increased parasite multiplication during acute infection, increased mortality from day 12 post-infection onwards and increased parasite burdens in the brain, day 30 post-infection. MKP-2(-/-) mice did not, however, demonstrate defective type-1 responses compared with MKP-2(+/+) mice following infection although they did display significantly reduced serum nitrite levels and enhanced tissue arginase-1 expression. Early resistance to T. gondii in MKP-2(+/+), but not MKP-2(-/-), mice was nitric oxide (NO) dependent as infected MKP-2(+/+), but not MKP-2(-/-) mice succumbed within 10 days post-infection with increased parasite burdens following treatment with the iNOS inhibitor L-NAME. Conversely, treatment of infected MKP-2(-/-) but not MKP-2(+/+) mice with nor-NOHA increased parasite burdens indicating a protective role for arginase-1 in MKP-2(-/-) mice. In vitro studies using tachyzoite-infected bone marrow derived macrophages and selective inhibition of arginase-1 and iNOS activities confirmed that both iNOS and arginase-1 contributed to inhibiting parasite replication. However, the effects of arginase-1 were transient and ultimately the role of iNOS was paramount in facilitating long-term inhibition of parasite multiplication within macrophages.
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154
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Fox BA, Sanders KL, Chen S, Bzik DJ. Targeting tumors with nonreplicating Toxoplasma gondii uracil auxotroph vaccines. Trends Parasitol 2013; 29:431-7. [PMID: 23928100 DOI: 10.1016/j.pt.2013.07.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Revised: 06/28/2013] [Accepted: 07/04/2013] [Indexed: 12/15/2022]
Abstract
Toxoplasma gondii is an intracellular parasite that has evolved to actively control its invaded host cells. Toxoplasma triggers then actively regulates host innate interleukin-12 (IL-12) and interferon-γ (IFN-γ) responses that elicit T cell control of infection. A live, nonreplicating avirulent uracil auxotroph vaccine strain (cps) of Toxoplasma triggers novel innate immune responses that stimulate amplified CD8(+) T cell responses and life-long immunity in vaccinated mice. Here, we review recent reports showing that intratumoral treatment with cps activated immune-mediated regression of established solid tumors in mice. We speculate that a better understanding of host-parasite interaction at the molecular level and applying improved genetic models based on Δku80 Toxoplasma strains will stimulate development of highly effective immunotherapeutic cancer vaccine strategies using engineered uracil auxotrophs.
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Affiliation(s)
- Barbara A Fox
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, 1 Medical Center Drive, Lebanon, NH 03756, USA
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155
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Rommereim LM, Hortua Triana MA, Falla A, Sanders KL, Guevara RB, Bzik DJ, Fox BA. Genetic manipulation in Δku80 strains for functional genomic analysis of Toxoplasma gondii. J Vis Exp 2013:e50598. [PMID: 23892917 PMCID: PMC3735270 DOI: 10.3791/50598] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Targeted genetic manipulation using homologous recombination is the method of choice for functional genomic analysis to obtain a detailed view of gene function and phenotype(s). The development of mutant strains with targeted gene deletions, targeted mutations, complemented gene function, and/or tagged genes provides powerful strategies to address gene function, particularly if these genetic manipulations can be efficiently targeted to the gene locus of interest using integration mediated by double cross over homologous recombination. Due to very high rates of nonhomologous recombination, functional genomic analysis of Toxoplasma gondii has been previously limited by the absence of efficient methods for targeting gene deletions and gene replacements to specific genetic loci. Recently, we abolished the major pathway of nonhomologous recombination in type I and type II strains of T. gondii by deleting the gene encoding the KU80 protein1,2. The Δku80 strains behave normally during tachyzoite (acute) and bradyzoite (chronic) stages in vitro and in vivo and exhibit essentially a 100% frequency of homologous recombination. The Δku80 strains make functional genomic studies feasible on the single gene as well as on the genome scale1-4. Here, we report methods for using type I and type II Δku80Δhxgprt strains to advance gene targeting approaches in T. gondii. We outline efficient methods for generating gene deletions, gene replacements, and tagged genes by targeted insertion or deletion of the hypoxanthine-xanthine-guanine phosphoribosyltransferase (HXGPRT) selectable marker. The described gene targeting protocol can be used in a variety of ways in Δku80 strains to advance functional analysis of the parasite genome and to develop single strains that carry multiple targeted genetic manipulations. The application of this genetic method and subsequent phenotypic assays will reveal fundamental and unique aspects of the biology of T. gondii and related significant human pathogens that cause malaria (Plasmodium sp.) and cryptosporidiosis (Cryptosporidium).
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Affiliation(s)
- Leah M Rommereim
- Department of Microbiology and Immunology, The Geisel School of Medicine at Dartmouth, USA
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156
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Smith NL, Abi Abdallah DS, Butcher BA, Denkers EY, Baird B, Holowka D. Toxoplasma gondii inhibits mast cell degranulation by suppressing phospholipase Cγ-mediated Ca(2+) mobilization. Front Microbiol 2013; 4:179. [PMID: 23847603 PMCID: PMC3701878 DOI: 10.3389/fmicb.2013.00179] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Accepted: 06/14/2013] [Indexed: 12/21/2022] Open
Abstract
Toxoplasma gondii is well-known to subvert normal immune responses, however, mechanisms are incompletely understood. In particular, its capacity to alter receptor-activated Ca2+-mediated signaling processes has not been well-characterized. In initial experiments, we found evidence that T. gondii infection inhibits Ca2+ responses to fMetLeuPhe in murine macrophages. To further characterize the mechanism of inhibition of Ca2+ mobilization by T. gondii, we used the well-studied RBL mast cell model to probe the capacity of T. gondii to modulate IgE receptor-activated signaling within the first hour of infection. Ca2+ mobilization that occurs via IgE/FcεRI signaling leads to granule exocytosis in mast cells. We found that T. gondii inhibits antigen-stimulated degranulation in infected cells in a strain-independent manner. Under these conditions, we found that cytoplasmic Ca2+ mobilization, particularly antigen-mediated Ca2+ release from intracellular stores, is significantly reduced. Furthermore, stimulation-dependent activation of Syk kinase leading to tyrosine phosphorylation and activation of phospholipase Cγ is inhibited by infection. Therefore, we conclude that inhibitory effects of infection are likely due to parasite-mediated inhibition of the tyrosine kinase signaling cascade that results in reduced hydrolysis of phosphatidylinositol 4,5-bisphosphate. Interestingly, inhibition of IgE/FcεRI signaling persists when tachyzoite invasion is arrested via cytochalasin D treatment, suggesting inhibition is mediated by a parasite-derived factor secreted into the cells during the invasion process. Our study provides direct evidence that immune subversion by T. gondii is initiated concurrently with invasion.
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Affiliation(s)
- Norah L Smith
- Baker Laboratory, Department of Chemistry and Chemical Biology, Cornell University Ithaca, NY, USA
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157
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Talevich E, Kannan N. Structural and evolutionary adaptation of rhoptry kinases and pseudokinases, a family of coccidian virulence factors. BMC Evol Biol 2013; 13:117. [PMID: 23742205 PMCID: PMC3682881 DOI: 10.1186/1471-2148-13-117] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 05/22/2013] [Indexed: 12/17/2022] Open
Abstract
Background The widespread protozoan parasite Toxoplasma gondii interferes with host cell functions by exporting the contents of a unique apical organelle, the rhoptry. Among the mix of secreted proteins are an expanded, lineage-specific family of protein kinases termed rhoptry kinases (ROPKs), several of which have been shown to be key virulence factors, including the pseudokinase ROP5. The extent and details of the diversification of this protein family are poorly understood. Results In this study, we comprehensively catalogued the ROPK family in the genomes of Toxoplasma gondii, Neospora caninum and Eimeria tenella, as well as portions of the unfinished genome of Sarcocystis neurona, and classified the identified genes into 42 distinct subfamilies. We systematically compared the rhoptry kinase protein sequences and structures to each other and to the broader superfamily of eukaryotic protein kinases to study the patterns of diversification and neofunctionalization in the ROPK family and its subfamilies. We identified three ROPK sub-clades of particular interest: those bearing a structurally conserved N-terminal extension to the kinase domain (NTE), an E. tenella-specific expansion, and a basal cluster including ROP35 and BPK1 that we term ROPKL. Structural analysis in light of the solved structures ROP2, ROP5, ROP8 and in comparison to typical eukaryotic protein kinases revealed ROPK-specific conservation patterns in two key regions of the kinase domain, surrounding a ROPK-conserved insert in the kinase hinge region and a disulfide bridge in the kinase substrate-binding lobe. We also examined conservation patterns specific to the NTE-bearing clade. We discuss the possible functional consequences of each. Conclusions Our work sheds light on several important but previously unrecognized features shared among rhoptry kinases, as well as the essential differences between active and degenerate protein kinases. We identify the most distinctive ROPK-specific features conserved across both active kinases and pseudokinases, and discuss these in terms of sequence motifs, evolutionary context, structural impact and potential functional relevance. By characterizing the proteins that enable these parasites to invade the host cell and co-opt its signaling mechanisms, we provide guidance on potential therapeutic targets for the diseases caused by coccidian parasites.
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Affiliation(s)
- Eric Talevich
- Institute of Bioinformatics, University of Georgia, Athens, GA, USA
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158
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Macêdo AG, Cunha JP, Cardoso THS, Silva MV, Santiago FM, Silva JS, Pirovani CP, Silva DAO, Mineo JR, Mineo TWP. SAG2A protein from Toxoplasma gondii interacts with both innate and adaptive immune compartments of infected hosts. Parasit Vectors 2013; 6:163. [PMID: 23735002 PMCID: PMC3706231 DOI: 10.1186/1756-3305-6-163] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2013] [Accepted: 05/26/2013] [Indexed: 11/26/2022] Open
Abstract
Background Toxoplasma gondii is an intracellular parasite that causes relevant clinical disease in humans and animals. Several studies have been performed in order to understand the interactions between proteins of the parasite and host cells. SAG2A is a 22 kDa protein that is mainly found in the surface of tachyzoites. In the present work, our aim was to correlate the predicted three-dimensional structure of this protein with the immune system of infected hosts. Methods To accomplish our goals, we performed in silico analysis of the amino acid sequence of SAG2A, correlating the predictions with in vitro stimulation of antigen presenting cells and serological assays. Results Structure modeling predicts that SAG2A protein possesses an unfolded C-terminal end, which varies its conformation within distinct strain types of T. gondii. This structure within the protein shelters a known B-cell immunodominant epitope, which presents low identity with its closest phyllogenetically related protein, an orthologue predicted in Neospora caninum. In agreement with the in silico observations, sera of known T. gondii infected mice and goats recognized recombinant SAG2A, whereas no serological cross-reactivity was observed with samples from N. caninum animals. Additionally, the C-terminal end of the protein was able to down-modulate pro-inflammatory responses of activated macrophages and dendritic cells. Conclusions Altogether, we demonstrate herein that recombinant SAG2A protein from T. gondii is immunologically relevant in the host-parasite interface and may be targeted in therapeutic and diagnostic procedures designed against the infection.
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Affiliation(s)
- Arlindo G Macêdo
- Laboratório de Imunoparasitologia "Dr, Mário Endsfeldz Camargo", Instituto de Ciências Biomédicas, Universidade Federal de Uberlândia, Av, Pará 1720-Bloco 4C, Campus Umuarama, Uberlândia, Minas Gerais 38.400-902, Brazil
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159
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Baird JR, Fox BA, Sanders KL, Lizotte PH, Cubillos-Ruiz JR, Scarlett UK, Rutkowski MR, Conejo-Garcia JR, Fiering S, Bzik DJ. Avirulent Toxoplasma gondii generates therapeutic antitumor immunity by reversing immunosuppression in the ovarian cancer microenvironment. Cancer Res 2013; 73:3842-51. [PMID: 23704211 DOI: 10.1158/0008-5472.can-12-1974] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Reversing tumor-associated immunosuppression seems necessary to stimulate effective therapeutic immunity against lethal epithelial tumors. Here, we show this goal can be addressed using cps, an avirulent, nonreplicating uracil auxotroph strain of the parasite Toxoplasma gondii (T. gondii), which preferentially invades immunosuppressive CD11c(+) antigen-presenting cells in the ovarian carcinoma microenvironment. Tumor-associated CD11c(+) cells invaded by cps were converted to immunostimulatory phenotypes, which expressed increased levels of the T-cell receptor costimulatory molecules CD80 and CD86. In response to cps treatment of the immunosuppressive ovarian tumor environment, CD11c(+) cells regained the ability to efficiently cross-present antigen and prime CD8(+) T-cell responses. Correspondingly, cps treatment markedly increased tumor antigen-specific responses by CD8(+) T cells. Adoptive transfer experiments showed that these antitumor T-cell responses were effective in suppressing solid tumor development. Indeed, intraperitoneal cps treatment triggered rejection of established ID8-VegfA tumors, an aggressive xenograft model of ovarian carcinoma, also conferring a survival benefit in a related aggressive model (ID8-Defb29/Vegf-A). The therapeutic benefit of cps treatment relied on expression of IL-12, but it was unexpectedly independent of MyD88 signaling as well as immune experience with T. gondii. Taken together, our results establish that cps preferentially invades tumor-associated antigen-presenting cells and restores their ability to trigger potent antitumor CD8(+) T-cell responses. Immunochemotherapeutic applications of cps might be broadly useful to reawaken natural immunity in the highly immunosuppressive microenvironment of most solid tumors.
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Affiliation(s)
- Jason R Baird
- Department of Microbiology and Immunology, The Geisel School of Medicine at Dartmouth, Norris Cotton Cancer Center, Lebanon, New Hampshire 03756, USA
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160
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Protein kinases of Toxoplasma gondii: functions and drug targets. Parasitol Res 2013; 112:2121-9. [DOI: 10.1007/s00436-013-3451-y] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 04/10/2013] [Indexed: 10/26/2022]
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161
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Zhao ZJ, Zhang J, Wei J, Li Z, Wang T, Yi SQ, Shen JL, Yang TB, Hide G, Lun ZR. Lower expression of inducible nitric oxide synthase and higher expression of arginase in rat alveolar macrophages are linked to their susceptibility to Toxoplasma gondii infection. PLoS One 2013; 8:e63650. [PMID: 23691079 PMCID: PMC3655142 DOI: 10.1371/journal.pone.0063650] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2012] [Accepted: 04/05/2013] [Indexed: 11/20/2022] Open
Abstract
Rats are naturally resistant to Toxoplasma gondii infection, particularly the RH strain, while mice are not. Previous studies have demonstrated that inducible nitric oxide synthase (iNOS) and arginase-1 of rodent peritoneal macrophages are linked to the mechanism of resistance. As an increasing number of studies on human and animal infections are showing that pulmonary toxoplasmosis is one of the most severe clinical signs from T. gondii infection, we are interested to know whether T. gondii infection in alveolar macrophages of rats is also linked to the levels of iNOS and arginase-1 activity. Our results demonstrate that T. gondii could grow and proliferate in rat alveolar macrophages, both in vitro and in vivo, at levels higher than resistant rat peritoneal macrophages and at comparable levels to sensitive mouse peritoneal macrophages. Lower activity and expression levels of iNOS and higher activity and expression levels of arginase-1 in rat alveolar macrophages were found to be linked to the susceptibility of T. gondii infection in these cells. These novel findings could aid a better understanding of the pathogenesis of clinical pulmonary toxoplasmosis in humans and domestic animals.
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Affiliation(s)
- Zhi-Jun Zhao
- State Key Laboratory of Biocontrol, Center for Parasitic Organisms, School of Life Sciences, and Key Laboratory of Tropical Disease and Control (Sun Yat-Sen University), Ministry of Education, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, PR China
- General Hospital of Ningxia Medical University, Yinchuan, PR China
| | - Jia Zhang
- State Key Laboratory of Biocontrol, Center for Parasitic Organisms, School of Life Sciences, and Key Laboratory of Tropical Disease and Control (Sun Yat-Sen University), Ministry of Education, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, PR China
| | - Jun Wei
- General Hospital of Ningxia Medical University, Yinchuan, PR China
| | - Zhi Li
- State Key Laboratory of Biocontrol, Center for Parasitic Organisms, School of Life Sciences, and Key Laboratory of Tropical Disease and Control (Sun Yat-Sen University), Ministry of Education, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, PR China
| | - Tao Wang
- State Key Laboratory of Biocontrol, Center for Parasitic Organisms, School of Life Sciences, and Key Laboratory of Tropical Disease and Control (Sun Yat-Sen University), Ministry of Education, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, PR China
| | - Si-Qi Yi
- State Key Laboratory of Biocontrol, Center for Parasitic Organisms, School of Life Sciences, and Key Laboratory of Tropical Disease and Control (Sun Yat-Sen University), Ministry of Education, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, PR China
| | - Ji-Long Shen
- Provincial Laboratory of Microbiology and Parasitology and the Key Laboratory of Zoonoses Anhui, Department of Parasitology, Anhui Medical University, Hefei, Anhui, PR China
| | - Ting-Bao Yang
- State Key Laboratory of Biocontrol, Center for Parasitic Organisms, School of Life Sciences, and Key Laboratory of Tropical Disease and Control (Sun Yat-Sen University), Ministry of Education, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, PR China
| | - Geoff Hide
- Ecosystems and Environment Research Centre and Biomedical Research Centre, School of Environment and Life Sciences, University of Salford, Salford, United Kingdom
| | - Zhao-Rong Lun
- State Key Laboratory of Biocontrol, Center for Parasitic Organisms, School of Life Sciences, and Key Laboratory of Tropical Disease and Control (Sun Yat-Sen University), Ministry of Education, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, PR China
- Ecosystems and Environment Research Centre and Biomedical Research Centre, School of Environment and Life Sciences, University of Salford, Salford, United Kingdom
- * E-mail:
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162
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Boothroyd JC. Have it your way: how polymorphic, injected kinases and pseudokinases enable Toxoplasma to subvert host defenses. PLoS Pathog 2013; 9:e1003296. [PMID: 23633947 PMCID: PMC3635977 DOI: 10.1371/journal.ppat.1003296] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- John C Boothroyd
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA.
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163
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Toxoplasma gondii rhoptry 16 kinase promotes host resistance to oral infection and intestinal inflammation only in the context of the dense granule protein GRA15. Infect Immun 2013; 81:2156-67. [PMID: 23545295 DOI: 10.1128/iai.01185-12] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Toxoplasma gondii transmission between intermediate hosts is dependent on the ingestion of walled cysts formed during the chronic phase of infection. Immediately following consumption, the parasite must ensure survival of the host by preventing adverse inflammatory responses and/or by limiting its own replication. Since the Toxoplasma secreted effectors rhoptry 16 kinase (ROP16) and dense granule 15 (GRA15) activate the JAK-STAT3/6 and NF-κB signaling pathways, respectively, we explored whether a particular combination of these effectors impacted intestinal inflammation and parasite survival in vivo. Here we report that expression of the STAT-activating version of ROP16 in the type II strain (strain II+ROP16I) promotes host resistance to oral infection only in the context of endogenous GRA15 expression. Protection was characterized by a lower intestinal parasite burden and dampened inflammation. Host resistance to the II+ROP16I strain occurred independently of STAT6 and the T cell coinhibitory receptors B7-DC and B7-H1, two receptors that are upregulated by ROP16. In addition, coexpression of ROP16 and GRA15 enhanced parasite susceptibility within tumor necrosis factor alpha/gamma interferon-stimulated macrophages in a STAT3/6-independent manner. Transcriptional profiling of infected STAT3- and STAT6-deficient macrophages and parasitized Peyer's patches from mice orally challenged with strain II+ROP16I suggested that ROP16 activated STAT5 to modulate host gene expression. Consistent with this supposition, the ROP16 kinase induced the sustained phosphorylation and nuclear localization of STAT5 in Toxoplasma-infected cells. In summary, only the combined expression of both GRA15 and ROP16 promoted host resistance to acute oral infection, and Toxoplasma may possibly target the STAT5 signaling pathway to generate protective immunity in the gut.
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164
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Schneider AG, Abi Abdallah DS, Butcher BA, Denkers EY. Toxoplasma gondii triggers phosphorylation and nuclear translocation of dendritic cell STAT1 while simultaneously blocking IFNγ-induced STAT1 transcriptional activity. PLoS One 2013; 8:e60215. [PMID: 23527309 PMCID: PMC3603897 DOI: 10.1371/journal.pone.0060215] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 02/23/2013] [Indexed: 12/29/2022] Open
Abstract
The protozoan Toxoplasma gondii actively modulates cytokine-induced JAK/STAT signaling pathways to facilitate survival within the host, including blocking IFNγ-mediated STAT1-dependent proinflammatory gene expression. We sought to further characterize inhibition of STAT1 signaling in infected murine dendritic cells (DC) because this cell type has not previously been examined, yet is known to serve as an early target of in vivo infection. Unexpectedly, we discovered that T. gondii infection alone induced sustained STAT1 phosphorylation and nuclear translocation in DC in a parasite strain-independent manner. Maintenance of STAT1 phosphorylation required active invasion but intracellular parasite replication was dispensable. The parasite rhoptry protein ROP16, recently shown to mediate STAT3 and STAT6 phosphorylation, was not required for STAT1 phosphorylation. In combination with IFNγ, T. gondii induced synergistic STAT1 phosphorylation and binding of aberrant STAT1-containing complexes to IFNγ consensus sequence oligonucleotides. Despite these findings, parasite infection blocked STAT1 binding to the native promoters of the IFNγ-inducible genes Irf-1 and Lrg47, along with subsequent gene expression. These results reinforce the importance of parasite-mediated blockade of IFNγ responses in dendritic cells, while simultaneously showing that T. gondii alone induces STAT1 phosphorylation.
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Affiliation(s)
- Anne G. Schneider
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
| | - Delbert S. Abi Abdallah
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
| | - Barbara A. Butcher
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
| | - Eric Y. Denkers
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
- * E-mail:
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165
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Zewdu E, Agonafir A, Tessema TS, Tilahun G, Medhin G, Vitale M, Di Marco V, Cox E, Vercruysse J, Dorny P. Seroepidemiological study of caprine toxoplasmosis in East and West Shewa Zones, Oromia Regional State, Central Ethiopia. Res Vet Sci 2013; 94:43-8. [DOI: 10.1016/j.rvsc.2012.07.020] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2012] [Revised: 06/12/2012] [Accepted: 07/07/2012] [Indexed: 01/01/2023]
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166
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The rhoptry proteome of Eimeria tenella sporozoites. Int J Parasitol 2013; 43:181-8. [DOI: 10.1016/j.ijpara.2012.10.024] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Revised: 10/23/2012] [Accepted: 10/27/2012] [Indexed: 11/18/2022]
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167
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Hunter CA, Sibley LD. Modulation of innate immunity by Toxoplasma gondii virulence effectors. Nat Rev Microbiol 2013; 10:766-78. [PMID: 23070557 DOI: 10.1038/nrmicro2858] [Citation(s) in RCA: 362] [Impact Index Per Article: 32.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Toxoplasma gondii is a common parasite of animals and humans and can cause serious opportunistic infections. However, the majority of infections are asymptomatic, possibly because the organism has co-evolved with its many vertebrate hosts and has developed multiple strategies to persist asymptomatically for the lifetime of the host. Over the past two decades, infection studies in the mouse, combined with forward-genetics approaches aimed at unravelling the molecular basis of infection, have revealed that T. gondii virulence is mediated, in part, by secretion of effector proteins into the host cell during invasion. Here, we review recent advances that illustrate how these virulence factors disarm innate immunity and promote survival of the parasite.
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Affiliation(s)
- Christopher A Hunter
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia 19104, USA.
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168
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Van Dyken SJ, Locksley RM. Interleukin-4- and interleukin-13-mediated alternatively activated macrophages: roles in homeostasis and disease. Annu Rev Immunol 2013; 31:317-43. [PMID: 23298208 DOI: 10.1146/annurev-immunol-032712-095906] [Citation(s) in RCA: 494] [Impact Index Per Article: 44.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The macrophage, a versatile cell type prominently involved in host defense and immunity, assumes a distinct state of alternative activation in the context of polarized type 2 immune responses such as allergic inflammation and helminth infection. This alternatively activated phenotype is induced by the canonical type 2 cytokines interleukin (IL)-4 and IL-13, which mediate expression of several characteristic markers along with a dramatic shift in macrophage metabolic pathways that influence surrounding cells and tissues. We discuss recent advances in the understanding of IL-4- and IL-13-mediated alternatively activated macrophages and type 2 immune responses; such advances have led to an expanded appreciation for functions of these cells beyond immunity, including maintenance of physiologic homeostasis and tissue repair.
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Affiliation(s)
- Steven J Van Dyken
- Departments of Medicine and Microbiology & Immunology, Howard Hughes Medical Institute, University of California, San Francisco, California 94143, USA
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169
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Kemp LE, Yamamoto M, Soldati-Favre D. Subversion of host cellular functions by the apicomplexan parasites. FEMS Microbiol Rev 2012. [PMID: 23186105 DOI: 10.1111/1574-6976.12013] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Rhoptries are club-shaped secretory organelles located at the anterior pole of species belonging to the phylum of Apicomplexa. Parasites of this phylum are responsible for a huge burden of disease in humans and animals and a loss of economic productivity. Members of this elite group of obligate intracellular parasites include Plasmodium spp. that cause malaria and Cryptosporidium spp. that cause diarrhoeal disease. Although rhoptries are almost ubiquitous throughout the phylum, the relevance and role of the proteins contained within the rhoptries varies. Rhoptry contents separate into two intra-organellar compartments, the neck and the bulb. A number of rhoptry neck proteins are conserved between species and are involved in functions such as host cell invasion. The bulb proteins are less well-conserved and probably evolved for a particular lifestyle. In the majority of species studied to date, rhoptry content is involved in formation and maintenance of the parasitophorous vacuole; however some species live free within the host cytoplasm. In this review, we will summarise the knowledge available regarding rhoptry proteins. Specifically, we will discuss the role of the rhoptry kinases that are used by Toxoplasma gondii and other coccidian parasites to subvert the host cellular functions and prevent parasite death.
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Affiliation(s)
- Louise E Kemp
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland.
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170
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Nance JP, Vannella KM, Worth D, David C, Carter D, Noor S, Hubeau C, Fitz L, Lane TE, Wynn TA, Wilson EH. Chitinase dependent control of protozoan cyst burden in the brain. PLoS Pathog 2012; 8:e1002990. [PMID: 23209401 PMCID: PMC3510238 DOI: 10.1371/journal.ppat.1002990] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Accepted: 09/10/2012] [Indexed: 02/07/2023] Open
Abstract
Chronic infections represent a continuous battle between the host's immune system and pathogen replication. Many protozoan parasites have evolved a cyst lifecycle stage that provides it with increased protection from environmental degradation as well as endogenous host mechanisms of attack. In the case of Toxoplasma gondii, these cysts are predominantly found in the immune protected brain making clearance of the parasite more difficult and resulting in a lifelong infection. Currently, little is known about the nature of the immune response stimulated by the presence of these cysts or how they are able to propagate. Here we establish a novel chitinase-dependent mechanism of cyst control in the infected brain. Despite a dominant Th1 immune response during Toxoplasma infection there exists a population of alternatively activated macrophages (AAMØ) in the infected CNS. These cells are capable of cyst lysis via the production of AMCase as revealed by live imaging, and this chitinase is necessary for protective immunity within the CNS. These data demonstrate chitinase activity in the brain in response to a protozoan pathogen and provide a novel mechanism to facilitate cyst clearance during chronic infections. Described here is a novel mechanism of protozoan cyst clearance in the CNS during chronic infection. These data show the presence of a population of alternatively activated macrophages in the brain that secrete the active chitinase, AMCase, in response to chitin in the cyst wall. Using both chemical and genetic inhibition in vitro, it is revealed that this enzyme is required for efficient degradation and destruction of the cyst. The necessity for AMCase is demonstrated in vivo, as the absence of the enzyme resulted in a significant increase in cyst burden and decrease in survival during chronic infection. Together, these data identify an important mechanism of parasite control and cyst clearance in the CNS. Currently, no therapies exist that lead to the total clearance of this parasite from the brain. Therefore, developing an understanding of the natural mechanisms of cyst clearance has the potential to lead to new and effective therapies for this and other chronic infections.
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Affiliation(s)
- J. Philip Nance
- Division of Biomedical Sciences, University of California, Riverside, California, United States of America
| | - Kevin M. Vannella
- National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Danielle Worth
- Division of Biomedical Sciences, University of California, Riverside, California, United States of America
| | - Clément David
- Division of Biomedical Sciences, University of California, Riverside, California, United States of America
| | - David Carter
- Institute for Integrative Genome Biology, University of California, Riverside, California, United States of America
| | - Shahani Noor
- Division of Biomedical Sciences, University of California, Riverside, California, United States of America
| | - Cedric Hubeau
- Department of Inflammation and Immunology, Pfizer, Cambridge, Massachusetts, United States of America
| | - Lori Fitz
- Department of Inflammation and Immunology, Pfizer, Cambridge, Massachusetts, United States of America
| | - Thomas E. Lane
- Department of Molecular Biology and Biochemistry, Institute for Immunology, University of California, Irvine, Irvine, California, United States of America
| | - Thomas A. Wynn
- National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Emma H. Wilson
- Division of Biomedical Sciences, University of California, Riverside, California, United States of America
- * E-mail:
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171
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McBerry C, Egan CE, Rani R, Yang Y, Wu D, Boespflug N, Boon L, Butcher B, Mirpuri J, Hogan SP, Denkers EY, Aliberti J, Herbert DR. Trefoil factor 2 negatively regulates type 1 immunity against Toxoplasma gondii. THE JOURNAL OF IMMUNOLOGY 2012; 189:3078-84. [PMID: 22896633 DOI: 10.4049/jimmunol.1103374] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
IL-12-mediated type 1 inflammation confers host protection against the parasitic protozoan Toxoplasma gondii. However, production of IFN-γ, another type 1 inflammatory cytokine, also drives lethality from excessive injury to the intestinal epithelium. As mechanisms that restore epithelial barrier function following infection remain poorly understood, this study investigated the role of trefoil factor 2 (TFF2), a well-established regulator of mucosal tissue repair. Paradoxically, TFF2 antagonized IL-12 release from dendritic cells (DCs) and macrophages, which protected TFF2-deficient (TFF2(-/-)) mice from T. gondii pathogenesis. Dysregulated intestinal homeostasis in naive TFF2(-/-) mice correlated with increased IL-12/23p40 levels and enhanced T cell recruitment at baseline. Infected TFF2(-/-) mice displayed low rates of parasite replication and reduced gut immunopathology, whereas wild-type (WT) mice experienced disseminated infection and lethal ileitis. p38 MAPK activation and IL-12p70 production was more robust from TFF2(-/-)CD8+ DC compared with WT CD8+ DC and treatment of WT DC with rTFF2 suppressed TLR-induced IL-12/23p40 production. Neutralization of IFN-γ and IL-12 in TFF2(-/-) animals abrogated resistance shown by enhanced parasite replication and infection-induced morbidity. Hence, TFF2 regulated intestinal barrier function and type 1 cytokine release from myeloid phagocytes, which dictated the outcome of oral T. gondii infection in mice.
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Affiliation(s)
- Cortez McBerry
- Division of Molecular Immunology, Cincinnati Children's Research Foundation, Cincinnati, OH 45229, USA
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172
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Denkers EY, Schneider AG, Cohen SB, Butcher BA. Phagocyte responses to protozoan infection and how Toxoplasma gondii meets the challenge. PLoS Pathog 2012; 8:e1002794. [PMID: 22876173 PMCID: PMC3410898 DOI: 10.1371/journal.ppat.1002794] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Affiliation(s)
- Eric Y Denkers
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
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173
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Luzina IG, Keegan AD, Heller NM, Rook GAW, Shea-Donohue T, Atamas SP. Regulation of inflammation by interleukin-4: a review of "alternatives". J Leukoc Biol 2012; 92:753-64. [PMID: 22782966 DOI: 10.1189/jlb.0412214] [Citation(s) in RCA: 242] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Studies of IL-4 have revealed a wealth of information on the diverse roles of this cytokine in homeostatic regulation and disease pathogenesis. Recent data suggest that instead of simple linear regulatory pathways, IL-4 drives regulation that is full of alternatives. In addition to the well-known dichotomous regulation of Th cell differentiation by IL-4, this cytokine is engaged in several other alternative pathways. Its own production involves alternative mRNA splicing, yielding at least two functional isoforms: full-length IL-4, encoded by the IL-4 gene exons 1-4, and IL-4δ2, encoded by exons 1, 3, and 4. The functional effects of these two isoforms are in some ways similar but in other ways quite distinct. When binding to the surface of target cells, IL-4 may differentially engage two different types of receptors. By acting on macrophages, a cell type critically involved in inflammation, IL-4 induces the so-called alternative macrophage activation. In this review, recent advances in understanding these three IL-4-related branch points--alternative splicing of IL-4, differential receptor engagement by IL-4, and differential regulation of macrophage activation by IL-4--are summarized in light of their contributions to inflammation.
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Affiliation(s)
- Irina G Luzina
- University of Maryland School of Medicine, Baltimore, MD 21201, USA
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174
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O'Shea JJ, Plenge R. JAK and STAT signaling molecules in immunoregulation and immune-mediated disease. Immunity 2012; 36:542-50. [PMID: 22520847 DOI: 10.1016/j.immuni.2012.03.014] [Citation(s) in RCA: 812] [Impact Index Per Article: 67.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Indexed: 12/12/2022]
Abstract
The discovery of the Janus kinase (JAK)-signal transducer and activator of transcripton (STAT) signaling pathway, a landmark in cell biology, provided a simple mechanism for gene regulation that dramatically advanced our understanding of the action of hormones, interferons, colony-stimulating factors, and interleukins. As we learn more about the complexities of immune responses, new insights into the functions of this pathway continue to be revealed, aided by technology that permits genome-wide views. As we celebrate the 20(th) anniversary of the discovery of this paradigm in cell signaling, it is particularly edifying to see how this knowledge has rapidly been translated to human immune disease. Not only have genome-wide association studies demonstrated that this pathway is highly relevant to human autoimmunity, but targeting JAKs is now a reality in immune-mediated disease.
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Affiliation(s)
- John J O'Shea
- Molecular Immunology and Inflammation Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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175
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Mirpuri J, Yarovinsky F. IL-6 signaling SOCS critical for IL-12 host response to Toxoplasma gondii. Future Microbiol 2012; 7:13-6. [PMID: 22191442 DOI: 10.2217/fmb.11.147] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
SOCS are a family of proteins that play an important role in the negative regulation of the cytokine-JAK-STAT pathway. Socs3 deletion results in prolonged IL-6 signaling measured by STAT3 phosphorylation. A role for STAT3 and SOCS3 in the context of Toxoplasma gondii infection is of particular importance, because STAT3 appears to be a key target of T. gondii virulence factors. By utilizing LysM-cre Socs3(fl/fl) mice, the Hunter laboratory recently established that macrophage-specific SOCS3 knockout mice have enhanced susceptibility to infection with T. gondii. The authors demonstrated that lack of SOCS3-mediated control of IL-6 signaling results in acute susceptibility to T. gondii due to impaired IL-12 production by inflammatory monocytes, macrophages and neutrophils. This article further explores these findings and their implications in the field of host resistance to microbial pathogens.
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Affiliation(s)
- Julie Mirpuri
- Department of Immunology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9093, USA
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176
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Reid AJ, Vermont SJ, Cotton JA, Harris D, Hill-Cawthorne GA, Könen-Waisman S, Latham SM, Mourier T, Norton R, Quail MA, Sanders M, Shanmugam D, Sohal A, Wasmuth JD, Brunk B, Grigg ME, Howard JC, Parkinson J, Roos DS, Trees AJ, Berriman M, Pain A, Wastling JM. Comparative genomics of the apicomplexan parasites Toxoplasma gondii and Neospora caninum: Coccidia differing in host range and transmission strategy. PLoS Pathog 2012; 8:e1002567. [PMID: 22457617 PMCID: PMC3310773 DOI: 10.1371/journal.ppat.1002567] [Citation(s) in RCA: 153] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Accepted: 01/23/2012] [Indexed: 11/18/2022] Open
Abstract
Toxoplasma gondii is a zoonotic protozoan parasite which infects nearly one third of the human population and is found in an extraordinary range of vertebrate hosts. Its epidemiology depends heavily on horizontal transmission, especially between rodents and its definitive host, the cat. Neospora caninum is a recently discovered close relative of Toxoplasma, whose definitive host is the dog. Both species are tissue-dwelling Coccidia and members of the phylum Apicomplexa; they share many common features, but Neospora neither infects humans nor shares the same wide host range as Toxoplasma, rather it shows a striking preference for highly efficient vertical transmission in cattle. These species therefore provide a remarkable opportunity to investigate mechanisms of host restriction, transmission strategies, virulence and zoonotic potential. We sequenced the genome of N. caninum and transcriptomes of the invasive stage of both species, undertaking an extensive comparative genomics and transcriptomics analysis. We estimate that these organisms diverged from their common ancestor around 28 million years ago and find that both genomes and gene expression are remarkably conserved. However, in N. caninum we identified an unexpected expansion of surface antigen gene families and the divergence of secreted virulence factors, including rhoptry kinases. Specifically we show that the rhoptry kinase ROP18 is pseudogenised in N. caninum and that, as a possible consequence, Neospora is unable to phosphorylate host immunity-related GTPases, as Toxoplasma does. This defense strategy is thought to be key to virulence in Toxoplasma. We conclude that the ecological niches occupied by these species are influenced by a relatively small number of gene products which operate at the host-parasite interface and that the dominance of vertical transmission in N. caninum may be associated with the evolution of reduced virulence in this species.
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Affiliation(s)
- Adam James Reid
- Wellcome Trust Sanger Institute, Hinxton, Cambridgshire, United Kingdom
| | - Sarah J. Vermont
- Institute of Infection and Global Health and School of Veterinary Science, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, Merseyside, United Kingdom
| | - James A. Cotton
- Wellcome Trust Sanger Institute, Hinxton, Cambridgshire, United Kingdom
| | - David Harris
- Wellcome Trust Sanger Institute, Hinxton, Cambridgshire, United Kingdom
| | | | | | - Sophia M. Latham
- Institute of Infection and Global Health and School of Veterinary Science, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, Merseyside, United Kingdom
| | - Tobias Mourier
- Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark
| | - Rebecca Norton
- Institute of Infection and Global Health and School of Veterinary Science, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, Merseyside, United Kingdom
| | - Michael A. Quail
- Wellcome Trust Sanger Institute, Hinxton, Cambridgshire, United Kingdom
| | - Mandy Sanders
- Wellcome Trust Sanger Institute, Hinxton, Cambridgshire, United Kingdom
| | - Dhanasekaran Shanmugam
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Amandeep Sohal
- Wellcome Trust Sanger Institute, Hinxton, Cambridgshire, United Kingdom
| | - James D. Wasmuth
- Program in Molecular Structure and Function, Hospital for Sick Children and Departments of Biochemistry and Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- Laboratory of Parasitic Diseases, National Institutes of Health, National Institute of Allergy and Infectious Diseases (NIAID), Bethesda, Maryland, United States of America
| | - Brian Brunk
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Michael E. Grigg
- Laboratory of Parasitic Diseases, National Institutes of Health, National Institute of Allergy and Infectious Diseases (NIAID), Bethesda, Maryland, United States of America
| | - Jonathan C. Howard
- Institute for Genetics, University of Cologne, Cologne, North Rhine-Westphalia, Germany
| | - John Parkinson
- Program in Molecular Structure and Function, Hospital for Sick Children and Departments of Biochemistry and Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - David S. Roos
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Alexander J. Trees
- Institute of Infection and Global Health and School of Veterinary Science, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, Merseyside, United Kingdom
| | - Matthew Berriman
- Wellcome Trust Sanger Institute, Hinxton, Cambridgshire, United Kingdom
| | - Arnab Pain
- Wellcome Trust Sanger Institute, Hinxton, Cambridgshire, United Kingdom
- King Abdullah University of Science and Technology, Thuwal, Jeddah, Kingdom of Saudi Arabia
- * E-mail: (AP); (JMW)
| | - Jonathan M. Wastling
- Institute of Infection and Global Health and School of Veterinary Science, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, Merseyside, United Kingdom
- * E-mail: (AP); (JMW)
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177
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Skariah S, Bednarczyk RB, McIntyre MK, Taylor GA, Mordue DG. Discovery of a novel Toxoplasma gondii conoid-associated protein important for parasite resistance to reactive nitrogen intermediates. THE JOURNAL OF IMMUNOLOGY 2012; 188:3404-15. [PMID: 22387554 DOI: 10.4049/jimmunol.1101425] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Toxoplasma gondii modifies its host cell to suppress its ability to become activated in response to IFN-γ and TNF-α and to develop intracellular antimicrobial effectors, including NO. Mechanisms used by T. gondii to modulate activation of its infected host cell likely underlie its ability to hijack monocytes and dendritic cells during infection to disseminate to the brain and CNS where it converts to bradyzoites contained in tissue cysts to establish persistent infection. To identify T. gondii genes important for resistance to the effects of host cell activation, we developed an in vitro murine macrophage infection and activation model to identify parasite insertional mutants that have a fitness defect in infected macrophages following activation but normal invasion and replication in naive macrophages. We identified 14 independent T. gondii insertional mutants out of >8000 screened that share a defect in their ability to survive macrophage activation due to macrophage production of reactive nitrogen intermediates (RNIs). These mutants have been designated counter-immune mutants. We successfully used one of these mutants to identify a T. gondii cytoplasmic and conoid-associated protein important for parasite resistance to macrophage RNIs. Deletion of the entire gene or just the region encoding the protein in wild-type parasites recapitulated the RNI-resistance defect in the counter-immune mutant, confirming the role of the protein in resistance to macrophage RNIs.
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Affiliation(s)
- Sini Skariah
- Department of Microbiology and Immunology, New York Medical College, Valhalla, NY 10595, USA
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178
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Deficiency of a Niemann-Pick, type C1-related protein in toxoplasma is associated with multiple lipidoses and increased pathogenicity. PLoS Pathog 2011; 7:e1002410. [PMID: 22174676 PMCID: PMC3234224 DOI: 10.1371/journal.ppat.1002410] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Accepted: 10/16/2011] [Indexed: 02/07/2023] Open
Abstract
Several proteins that play key roles in cholesterol synthesis, regulation, trafficking and signaling are united by sharing the phylogenetically conserved 'sterol-sensing domain' (SSD). The intracellular parasite Toxoplasma possesses at least one gene coding for a protein containing the canonical SSD. We investigated the role of this protein to provide information on lipid regulatory mechanisms in the parasite. The protein sequence predicts an uncharacterized Niemann-Pick, type C1-related protein (NPC1) with significant identity to human NPC1, and it contains many residues implicated in human NPC disease. We named this NPC1-related protein, TgNCR1. Mammalian NPC1 localizes to endo-lysosomes and promotes the movement of sterols and sphingolipids across the membranes of these organelles. Miscoding patient mutations in NPC1 cause overloading of these lipids in endo-lysosomes. TgNCR1, however, lacks endosomal targeting signals, and localizes to flattened vesicles beneath the plasma membrane of Toxoplasma. When expressed in mammalian NPC1 mutant cells and properly addressed to endo-lysosomes, TgNCR1 restores cholesterol and GM1 clearance from these organelles. To clarify the role of TgNCR1 in the parasite, we genetically disrupted NCR1; mutant parasites were viable. Quantitative lipidomic analyses on the ΔNCR1 strain reveal normal cholesterol levels but an overaccumulation of several species of cholesteryl esters, sphingomyelins and ceramides. ΔNCR1 parasites are also characterized by abundant storage lipid bodies and long membranous tubules derived from their parasitophorous vacuoles. Interestingly, these mutants can generate multiple daughters per single mother cell at high frequencies, allowing fast replication in vitro, and they are slightly more virulent in mice than the parental strain. These data suggest that the ΔNCR1 strain has lost the ability to control the intracellular levels of several lipids, which subsequently results in the stimulation of lipid storage, membrane biosynthesis and parasite division. Based on these observations, we ascribe a role for TgNCR1 in lipid homeostasis in Toxoplasma.
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179
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Toxoplasma and Plasmodium protein kinases: roles in invasion and host cell remodelling. Int J Parasitol 2011; 42:21-32. [PMID: 22154850 DOI: 10.1016/j.ijpara.2011.11.007] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Revised: 11/16/2011] [Accepted: 11/16/2011] [Indexed: 11/20/2022]
Abstract
Some apicomplexan parasites have evolved distinct protein kinase families to modulate host cell structure and function. Toxoplasma gondii rhoptry protein kinases and pseudokinases are involved in virulence and modulation of host cell signalling. The proteome of Plasmodium falciparum contains a family of putative kinases called FIKKs, some of which are exported to the host red blood cell and might play a role in erythrocyte remodelling. In this review we will discuss kinases known to be critical for host cell invasion, intracellular growth and egress, focusing on (i) calcium-dependent protein kinases and (ii) the secreted kinases that are unique to Toxoplasma (rhoptry protein kinases and pseudokinases) and Plasmodium (FIKKs).
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180
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An inside job: hacking into Janus kinase/signal transducer and activator of transcription signaling cascades by the intracellular protozoan Toxoplasma gondii. Infect Immun 2011; 80:476-82. [PMID: 22104110 DOI: 10.1128/iai.05974-11] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The intracellular protozoan Toxoplasma gondii is well known for its skill at invading and living within host cells. New discoveries are now also revealing the astounding ability of the parasite to inject effector proteins into the cytoplasm to seize control of the host cell. This review summarizes recent advances in our understanding of one such secretory protein called ROP16. This molecule is released from rhoptries into the host cell during invasion. The ROP16 molecule acts as a kinase, directly activating both signal transducer and activator of transcription 3 (STAT3) and STAT6 signaling pathways. In macrophages, an important and preferential target cell of parasite infection, the injection of ROP16 has multiple consequences, including downregulation of proinflammatory cytokine signaling and macrophage deviation to an alternatively activated phenotype.
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