RETREG2 and cyst: Cyst counts of infected brain homogenates demonstrated that MAG2 did not affect the ability of T. gondii to form cysts in vivo and did not affect the number of cysts seen in the brains of mice following infection; e.g., there were no significant differences seen between the Pru parental, ΔMAG2, and MAG2-COMP strains (Fig. 4A).