The long-term objective of this application is to understand the molecular pathogenesis of infection with the intracellular protozoan Toxoplasma gondii. The parasite is an important pathogen in immunosuppressed populations and is classified by the NIAID as a category B biodefense organism. Nevertheless, in most cases infection with this widespread parasite is asymptomatic. Host survival during infection requires robust Type 1 cytokine production, yet overly exuberant responses can result in host pathology and death. Thus, both parasite and host benefit from regulated proinflammatory cytokine responses. The underlying hypothesis to be tested is that T. gondii possesses molecular mechanisms to subvert host signaling pathways leading to proinflammatory cytokine production. Recent work has revealed the ability of Toxoplasma to down-regulate cytokines such as TNF-? from within infected cells. Increasing evidence indicates this is achieved through sophisticated manipulation of host intracellular signaling cascades. The goal of this proposal is to elucidate mechanisms by which Toxoplasma subverts proinflammatory signaling cascades in the innate immune system, in particular within cells such as macrophages and dendritic cells that are targeted for in vivo infection. Cellular and biochemical methods will be employed to define the points at which Toxoplasma interferes with host signal transduction. In this regard, parasite-induced activation of signaling molecule STAT3, known to be involved in down-regulation of proinflammatory cytokines IL-12 and TNF-?, will be examined. The nature of TNF-? suppression in infected macrophages is profound. Therefore, we will employ molecular methods to determine how the parasite influences promoter activity of the TNF-? gene. The last part of this proposal will focus effort on examining if parasite-infected macrophages and dendritic cells display a suppression phenotype during in vivo mouse infections. This will be accomplished using cellular and immunological methods to determine IL-12 and TNF-? production in infected cells in vivo and their in vivo ability to respond to defined Toll-like receptor ? ligands. In addition, macrophage and dendritic cell expression of cell surface activation markers will be analyzed. From these studies, we expect to gain important information on how T. gondii interacts with the host innate immune system, allowing a deeper understanding of infection with this important opportunistic pathogen. PROJECT NARRATIVE /

Public Health Relevance

The relevance of the project to public health is that Toxoplasma infects between 30-80% of the human population worldwide. While normally an asymptomatic infection, with suboptimal immune function the parasite emerges as a devastating and sometimes lethal infection. This project will enhance our understanding of immunity to the parasite, leading to improved treatment strategies.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI050617-10
Application #
8239540
Study Section
Pathogenic Eukaryotes Study Section (PTHE)
Program Officer
Wali, Tonu M
Project Start
2002-09-15
Project End
2014-03-31
Budget Start
2012-04-01
Budget End
2014-03-31
Support Year
10
Fiscal Year
2012
Total Cost
$371,185
Indirect Cost
$126,160
Name
Cornell University
Department
Microbiology/Immun/Virology
Type
Schools of Veterinary Medicine
DUNS #
872612445
City
Ithaca
State
NY
Country
United States
Zip Code
14850
Schneider, Anne G; Abi Abdallah, Delbert S; Butcher, Barbara A et al. (2013) Toxoplasma gondii triggers phosphorylation and nuclear translocation of dendritic cell STAT1 while simultaneously blocking IFNýý-induced STAT1 transcriptional activity. PLoS One 8:e60215
Cohen, Sara B; Maurer, Kirk J; Egan, Charlotte E et al. (2013) CXCR3-dependent CD4ýýý T cells are required to activate inflammatory monocytes for defense against intestinal infection. PLoS Pathog 9:e1003706
Denkers, Eric Y; Bzik, David J; Fox, Barbara A et al. (2012) An inside job: hacking into Janus kinase/signal transducer and activator of transcription signaling cascades by the intracellular protozoan Toxoplasma gondii. Infect Immun 80:476-82
Butcher, Barbara A; Fox, Barbara A; Rommereim, Leah M et al. (2011) Toxoplasma gondii rhoptry kinase ROP16 activates STAT3 and STAT6 resulting in cytokine inhibition and arginase-1-dependent growth control. PLoS Pathog 7:e1002236
Denkers, Eric Y (2010) Toll-like receptor initiated host defense against Toxoplasma gondii. J Biomed Biotechnol 2010:737125
Egan, C E; Sukhumavasi, W; Butcher, B A et al. (2009) Functional aspects of Toll-like receptor/MyD88 signalling during protozoan infection: focus on Toxoplasma gondii. Clin Exp Immunol 156:17-24
Leng, J; Butcher, B A; Denkers, E Y (2009) Dysregulation of macrophage signal transduction by Toxoplasma gondii: past progress and recent advances. Parasite Immunol 31:717-28
Leng, Jin; Butcher, Barbara A; Egan, Charlotte E et al. (2009) Toxoplasma gondii prevents chromatin remodeling initiated by TLR-triggered macrophage activation. J Immunol 182:489-97
Leng, Jin; Denkers, Eric Y (2009) Toxoplasma gondii inhibits covalent modification of histone H3 at the IL-10 promoter in infected macrophages. PLoS One 4:e7589
Bierly, Allison L; Shufesky, William J; Sukhumavasi, Woraporn et al. (2008) Dendritic cells expressing plasmacytoid marker PDCA-1 are Trojan horses during Toxoplasma gondii infection. J Immunol 181:8485-91

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