Identifying and Characterizing Genes Important for Evading the Host Immune Response in Toxoplasma gondii

Toxoplasma gondii is an obligate intracellular parasite that causes the disease toxoplasmosis. The parasite life cycle involves transition between three developmental stages tachyzoites, bradyzoites and oocysts. Like all intracellular pathogens, T. gondii alters its host cell to enable its own intracellular survival. The overall goal in the current study is to identify parasite genes that are important for surviving the IFN-gamma-induced cell autonomous immune response during infection. We also describe the isolation of a unique mutant, 11BE9, which we propose to use to identify global gene regulators that direct the parasite from tachyzoites toward sexual stages. Bioinformatic analysis of the up-regulated genes revealed that the majority were putative oocyst and bradyzoite genes that were misexpressed in the tachyzoite stage in the 11BE9 mutant. The 11BE9 provides a novel tool to dissect parasite gene function and pathways important for differentiation toward sexual stages in the feline definitive host.