Bradyzoite Pseudokinase 1 Is Crucial for Efficient Oral Infectivity of the Toxoplasma gondii Tissue Cyst
ABSTRACTThe tissue cyst formed by the bradyzoite stage ofToxoplasma gondiiis essential for persistent infection of the host and oral transmission. Bradyzoite pseudokinase 1 (BPK1) is a component of the cyst wall, but nothing has previously been known about its function. Here, we show that immunoprecipitation of BPK1 fromin vitrobradyzoite cultures, 4 days postinfection, identifies at least four associating proteins: MAG1, MCP4, GRA8, and GRA9. To determine the role of BPK1, a strain ofToxoplasmawas generated with thebpk1locus deleted. This BPK1 knockout strain (Δbpk1) was investigatedin vitroandin vivo. No defect was found in terms ofin vitrocyst formation and no difference in pathogenesis or cyst burden 4 weeks postinfection (wpi) was detected after intraperitoneal (i.p.) infection withΔbpk1tachyzoites, although the Δbpk1cysts were significantly smaller than parental or BPK1-complemented strains at 8 wpi. Pepsin-acid treatment of 4 wpiin vivocysts revealed that Δbpk1parasites are significantly more sensitive to this treatment than the parental and complemented strains. Consistent with this, 4 wpi Δbpk1cysts showed reduced ability to cause oral infection compared to the parental and complemented strains. Together, these data reveal that BPK1 plays a crucial role in thein vivodevelopment and infectivity ofToxoplasmacysts.