Transgenic T. gondii used for in vivo challenges was derived from Type II Prugniaud (Pru) strain and expresses the firefly luciferase (FLUC) gene constitutively by tachyzoites and bradyzoites. It was created, and kindly provided by S. Kim, J. Boothroyd and J. Saeij (Stanford University) and was maintained and utilized as previously described [18, 37, 39] .