As shown in Figures 6D, F, H, ,J no death was observed in mice infected with 500 PruΔpp7, and the parasite cyst burden and number of plaques of PruΔpp7 were significantly lower than that of WT, suggesting that loss of pp7 gene in Pru strain markedly attenuated the virulence of the tachyzoites. The gene discussed is PPEF1; the disease is cyst.