Figure 4.

Δldh mutant immunization prevented cyst formation from further infections. (A) ICR mice were pre-immunized with ME49 Δldh as in Figure 2 and 30 days later challenged with 10⁴ tachyzoites of TgPIG-WH1. Non-immunized mice were included as control and survival of mice were monitored for another 30 days (n = 10 mice for each strain). (B) Cyst loads in the brains of non-immunized but TgPIG-WH1 challenged mice, immunized and TgPIG-WH1 challenged mice, and Δldh immunized but not TgPIG-WH1 challenged mice [not shown in (A)]. The mice survived at day 30 in (A) were sacrificed, and the number of Toxoplasma cysts in the brain homogenate was determined by DBA-FITC staining and fluorescent microscopy. Data from the analysis of five mice in each group were graphed, *p < 0.05, Student’s t-test.