Spontaneous cystogenesis of Toxoplasma gondii in feline epithelial cells in vitro.

Toxoplasma gondii Nicolle et Manceaux, 1908 is an obligate intracellular parasite with the ability to infect mammals and birds. The only definitive hosts for T. gondii are felids, as the parasites form immature oocysts that are shed in the faeces. Here we introduce cat cells as a model for the study of experimental toxoplasmosis. We selected epithelial cells derived from cat kidneys (CRFK) as a target to determine the intracellular fate ofbradyzoites of the T. gondii ME49 strain. In parallel, we compared this infection using epithelial cells from the rat intestine (IEC-6), considering the enteroepithelial development that occurs in the cat. Different ratios of parasites to host cells were assayed over the course of a 14-day-infection. The intracellular development of T. gondii was dependent on the source of the epithelial cells and also on the parasite/host cell ratio. Cystogenesis was well established in the CRFK cell line at a ratio of 1:10 after 10-14 days of infection. This cellular model system opens a new field of investigation into the molecular aspects of the interactions between T. gondii and feline epithelial cells. The CRFK cell line appears to be a potential cellular model for large scale cyst production in vitro, which would allow a reduction in the number of animals used and/or replacement of animals by in vitro cultures.