Primary and secondary infection survival of recombinant inbred mice (AxB;BxA).

26 strains (n = 2) from the RI (AxB; BxA) panel were infected with 104 type III avirulent CEP hxgprt- T. gondii parasites; then, 35 days later, mice were challenged with 5x104 virulent type I GT1 T. gondii parasites. Primary and secondary infection survival percentages are indicated. 35–45 days after secondary challenge, brains from the surviving RI mice were homogenized in PBS and used to inoculate HFF monolayers. The resultant parasite cultures were then tested for the presence of the challenging strain; numerator = number of mice tested positive for secondary infection strain in the brain; denominator = number of mice that exhibited parasite growth in the HFF monolayer prior to drug selection. Some surviving mice failed to generate parasite positive cultures. 1Parasite growth was observed in mycophenolic acid / xanthine medium, which selects for GT1 parasites (the challenging strain) encoding the endogenous HXGPRT gene and against the primary infection CEP hxgprt- strain.
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