Bradyzoite pseudokinase 1 is crucial for efficient oral infectivity of the Toxoplasma tissue cyst

Eukaryot Cell. 2013 Jan 4. [Epub ahead of print]

Bradyzoite pseudokinase 1 is crucial for efficient oral infectivity of the Toxoplasma tissue cyst

Buchholz KR, Bowyer PW, Boothroyd JC.

Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, 94305, USA.

The tissue cyst formed by the bradyzoite stage of Toxoplasma gondii is essential for persistent infection of the host as well as oral transmission. Bradyzoite secreted 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 from in vitro bradyzoite cultures, 4 days post-infection, identifies at least four associating proteins: MAG1, MCP4, GRA8 and GRA9. To determine the role of BPK1, a strain of Toxoplasma was generated with the bpk1 locus deleted. This BPK1 knock-out strain (Δbpk1) was investigated in vitro and in vivo. No defect was found in terms of in vitro cyst formation and no difference in pathogenesis or cyst burden 4 weeks post-infection (wpi) was detected after intraperitoneal (i.p.) infection with Δbpk1 tachyzoites, although the Δbpk1 cysts were significantly smaller than parental or BPK1-complemented strains at 8 wpi. Pepsin-acid treatment of 4 wpi in vivo cysts revealed Δbpk1 parasites are significantly more sensitive to this treatment compared to the parental and complemented strains. Consistent with this, 4 wpi Δbpk1 cysts were reduced in the ability to cause oral infection compared to the parental and complemented strains. Together, these data reveal that BPK1 plays a crucial role in the in vivo development and infectivity of Toxoplasma cysts.

PMID: 23291621 [PubMed - as supplied by publisher]