This proposal addresses molecular mechanisms that are central for formation and reactivation of latent stages of Toxoplasma gondii, a protozoan parasite that causes life-threatening opportunistic infection in AIDS/HIV patients. The ability of Toxoplasma to convert from its proliferative stage (tachyzoite) to latent tissue cysts (bradyzoite) gives rise to the life-threatening chronic opportunistic disease that afflicts AIDS patients. There is a vital need for new approaches for treatment of AIDS-toxoplasmosis, but this effort has been hindered by an insufficient understanding of the mechanisms by which the latent stage develops and reactivates. We discovered that phosphorylation of the Toxoplasma alpha subunit of eukaryotic initiation factor-2 (TgIF2?) contributes to bradyzoite development. Using polysome profiling, which we adapted for use in Toxoplasma, we showed that TgIF2? phosphorylation leads to preferential translation of a subset of mRNAs that are linked to bradyzoite development. Further support that translational control has critical functions during both replicative and lateny stages comes from our new studies using the drugs salubrinal (SAL) and guanabenz (GA), which inhibit TgIF2? dephosphorylation and block the reactivation of bradyzoites. Here we show that GA also protects mice acutely infected with Toxoplasma and decreases the number of cysts in chronically infected mice. Together, our genetic, biochemical, and pharmacological experiments support our hypothesis that translational control mediated by TgIF2? phosphorylation is critical for parasite stage interconversion. Our proposed experiments will address this hypothesis and 1) establish how TgIF2? kinases coordinate conversion to bradyzoites, 2) identify translationally controlled mRNAs initiating bradyzoite development and reconversion into replicating tachyzoites, and 3) determine the mechanisms underlying TgIF2? dephosphorylation and reactivation of infection. Completion of these aims will help define the mechanics of Toxoplasma stage conversion, with an eye towards developing critically needed novel therapies for AIDS-toxoplasmosis.

Public Health Relevance

Toxoplasma gondii is a parasite that causes life-threatening disease in HIV/AIDS patients due to its ability to remain in the host as a latent cyst form that ca reactivate during immune suppression. Using genetic, biochemical, and pharmacological approaches, we determined that conversion between latent and replicative stages of the parasite involves a process called translational control, which features preferential synthesis of proteins that direct adaptation to changing environmental conditions. The proposed studies will address the process by which translational control contributes to toxoplasmosis, with the goal of uncovering novel therapies to thwart this opportunistic infection in AIDS patients.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI124723-02
Application #
9226018
Study Section
Special Emphasis Panel (ZRG1-AARR-K (02)M)
Program Officer
Mcgugan, Glen C
Project Start
2016-03-01
Project End
2021-02-28
Budget Start
2017-03-01
Budget End
2018-02-28
Support Year
2
Fiscal Year
2017
Total Cost
$389,080
Indirect Cost
$139,080
Name
Indiana University-Purdue University at Indianapolis
Department
Pharmacology
Type
Schools of Medicine
DUNS #
603007902
City
Indianapolis
State
IN
Country
United States
Zip Code
46202
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