This proposal outlines a comprehensive plan to genetically dissect the fatty acid metabolism of the human pathogen Toxoplasma gondii. T. gondii infection is widespread in the U.S. (22% of the population is chronically infected) and while usually benign can cause life-threatening disease in immunosuppressed individuals (e.g. those with HIV-AIDS, transplant recipients, or hematological malignancies). Congenital transmission of T. gondii is also a major public health concern. Highly virulent parasite strains have been recently identified as the cause of severe and recurring eye infections that ultimately lead to blindness. T. gondii also has the potential to cause significant waterborne outbreaks and has been listed by the CDC as a potential bioterrorism pathogen (appendix B). The currently available treatment has frequent and significant adverse effects and shows no efficacy in chronic infection, thus allowing for recrudescence of the active infection. Thus, new drugs are urgently needed. The discovery of a chloroplast-like organelle in apicomplexan parasites provides several promising parasite-specific target pathways for drug development. Among these pathways is a bacterial type II fatty acid synthesis pathway, and enzymes in this pathway have been the subject of intensive medicinal chemistry efforts to develop drugs against malaria and toxoplasmosis. However, what the precise function of this pathway for T. gondii and related apicomplexan parasites is remains unclear. Furthermore, the parasite genome encodes additional enzyme systems that might supply fatty acids either by synthesis or salvage from the host cell. A detailed understanding of the function and relative importance of these pathways is needed to guide the drug development effort to the most promising targets. In this project we will use genetics and metabolomics to dissect the complex interaction of three individual pathways. Using a novel and highly efficient approach to engineer conditional T. gondii mutants we will rigorously test the importance and function of each individual pathway in vivo. We will determine the impact of the loss of specific pathways on the parasite fatty acid and lipid composition using unbiased metabolomic profiling. To define the interactions between individual pathways and between the parasite and its host cell we conduct metabolic flux studies using stable epitope tracing. Overall we expect the outlined studies to produce a detailed mechanistic understanding of fatty acid synthesis as an important part of parasite metabolism and metabolic host-parasite interaction. Mutant analysis will highlight truly essential components as potential pharmacological targets. We also expect that the genetic and metabolomic tools honed along the way will prove highly useful for the dissection of many facets of parasite biology beyond lipid metabolism.

Public Health Relevance

This project will use modern genetic and metabolomic approaches to dissect the metabolism of the human pathogen Toxoplasma gondii. The studies will provide important information to guide the development of drug treatments and will lead to a detailed understanding of host-parasite interaction at the metabolic level.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI084415-03
Application #
8232138
Study Section
Special Emphasis Panel (ZRG1-AARR-C (04))
Program Officer
Mcgugan, Glen C
Project Start
2010-03-15
Project End
2015-02-28
Budget Start
2012-03-01
Budget End
2013-02-28
Support Year
3
Fiscal Year
2012
Total Cost
$334,765
Indirect Cost
$81,398
Name
University of Georgia
Department
Public Health & Prev Medicine
Type
Organized Research Units
DUNS #
004315578
City
Athens
State
GA
Country
United States
Zip Code
30602
Bowman, Jessica D; Merino, Emilio F; Brooks, Carrie F et al. (2014) Antiapicoplast and gametocytocidal screening to identify the mechanisms of action of compounds within the malaria box. Antimicrob Agents Chemother 58:811-9
Cai, Guobin; Deng, Lisheng; Xue, Jian et al. (2013) Expression, characterization and inhibition of Toxoplasma gondii 1-deoxy-D-xylulose-5-phosphate reductoisomerase. Bioorg Med Chem Lett 23:2158-61
Ramakrishnan, Srinivasan; Serricchio, Mauro; Striepen, Boris et al. (2013) Lipid synthesis in protozoan parasites: a comparison between kinetoplastids and apicomplexans. Prog Lipid Res 52:488-512
Li, Zhu-Hong; Ramakrishnan, Srinivasan; Striepen, Boris et al. (2013) Toxoplasma gondii relies on both host and parasite isoprenoids and can be rendered sensitive to atorvastatin. PLoS Pathog 9:e1003665