Toxoplasma gondii is an important opportunistic infection of AIDS patients. Improved strategies and approaches are urgently needed to more effectively prevent and treat recurrent infections in AIDS. Following primary infection, a chronic life-long T. gondii infection characterized by the presence of persisting cysts containing slowly or nonreplicating bradyzoite parasite forms is established in CNS/brain. Reactivated infection due to cyst rupture during immune suppression causes a difficult to treat and life-threatening Toxoplasmic encephalitis in AIDS. Currently, no vaccine is approved for use in humans to prevent infection and drug treatments for acute infection are suboptimal. Eradicating pre-existing cysts and chronic infection is an excellent approach to control/prevent infection in AIDS. However, no current treatment is effective at eradicating pre-existing cysts and chronic infection. Lack of progress in targeting cyst stages can be attributed to major gaps in our knowledge of parasite biology underlying cyst development and maintenance of chronic infection. Recent progress in understanding the complex host-parasite interaction has revealed that many rhoptry bulb (ROP) proteins appear to be central players in host cell manipulation due to their secretion into the host cell at invasion and their subsequent localization to host cell cytosol/nucleus or their intimate association with the parasitophorous vacuole. Host cell manipulation by these secreted ROP proteins is likely to be critical to the success of parasite biology necessary for acute and chronic infection in vivo. The parasitophorous vacuole appears to be critical for replication of tachyzoites as well as being central to the development of the cyst wall and tissue cyst that characterize chronic infection. We hypothesize that a family of ~ 34 secreted ROP proteins possessing homology to kinases (the """"""""ROP kinome"""""""") are outstanding candidates as potential targets to disrupt virulence, cyst development, or chronic infection. Here, we propose to delete each predicted gene member of the secreted ROP kinome in type II T. gondii, and to then ascertain any defect in acute virulence, in early cyst development, or in chronic infection. Using a directed functional genetic approach, this work will identify specific members of the secreted ROP kinome that participate in critical functions required for establishing or maintaining chronic infection in vivo. This project will identify and validate specific secreted ROP kinases as key targets for preventing acute or chronic infection. This project will also develop essential tools and methods required for the future undertaking of larger scale higher throughput knockout and functional genomic projects in type II T. gondii. Consequently, this innovative project has high overall impact by advancing genetic models for dissection of type II biology, by revealing new aspects of host-parasite interaction, and by exposing new targets to prevent or eradicate chronic infection.

Public Health Relevance

This project will identify specialized parasite proteins that are essential for the ability of Toxoplasma gondii to establish and maintain a chronic infection. No vaccine is currently available to prevent infection and no drug treatment is available that can eradicate chronic infection. By functional analysis of a family of specialized parasite proteins we expect to identify new targets to prevent or eradicate chronic infection. The information gained in this project helps to uncovering fundamental knowledge of how a parasite manipulates mammalian cells and the mammalian host, and will thus uncover new approaches to eradicate a significant parasite of humans.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Exploratory/Developmental Grants (R21)
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Study Section
AIDS-associated Opportunistic Infections and Cancer Study Section (AOIC)
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Mcgugan, Glen C
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Dartmouth College
Schools of Medicine
United States
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Fox, Barbara A; Rommereim, Leah M; Guevara, Rebekah B et al. (2016) The Toxoplasma gondii Rhoptry Kinome Is Essential for Chronic Infection. MBio 7:
Fox, Barbara A; Sanders, Kiah L; Rommereim, Leah M et al. (2016) Secretion of Rhoptry and Dense Granule Effector Proteins by Nonreplicating Toxoplasma gondii Uracil Auxotrophs Controls the Development of Antitumor Immunity. PLoS Genet 12:e1006189
Rommereim, Leah M; Bellini, Valeria; Fox, Barbara A et al. (2016) Phenotypes Associated with Knockouts of Eight Dense Granule Gene Loci (GRA2-9) in Virulent Toxoplasma gondii. PLoS One 11:e0159306
Leroux, Louis-Philippe; Dasanayake, Dayal; Rommereim, Leah M et al. (2015) Secreted Toxoplasma gondii molecules interfere with expression of MHC-II in interferon gamma-activated macrophages. Int J Parasitol 45:319-32
Fox, Barbara A; Bzik, David J (2015) Nonreplicating, cyst-defective type II Toxoplasma gondii vaccine strains stimulate protective immunity against acute and chronic infection. Infect Immun 83:2148-55
Zhao, Yanlin; Marple, Andrew H; Ferguson, David J P et al. (2014) Avirulent strains of Toxoplasma gondii infect macrophages by active invasion from the phagosome. Proc Natl Acad Sci U S A 111:6437-42
Patil, Veerupaxagouda; Zhao, Yanlin; Shah, Suhagi et al. (2014) Co-existence of classical and alternative activation programs in macrophages responding to Toxoplasma gondii. Int J Parasitol 44:161-4
Mouveaux, Thomas; Oria, Gabrielle; Werkmeister, Elisabeth et al. (2014) Nuclear glycolytic enzyme enolase of Toxoplasma gondii functions as a transcriptional regulator. PLoS One 9:e105820
Baird, Jason R; Byrne, Katelyn T; Lizotte, Patrick H et al. (2013) Immune-mediated regression of established B16F10 melanoma by intratumoral injection of attenuated Toxoplasma gondii protects against rechallenge. J Immunol 190:469-78
Fox, Barbara A; Sanders, Kiah L; Bzik, David J (2013) Non-replicating Toxoplasma gondii reverses tumor-associated immunosuppression. Oncoimmunology 2:e26296

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