Figure 2: Protection against malaria infection after a single immunizing dose of IrPySpz. Groups of naive B6 mice and MHC-I- -Tg mice (5 per group) were immunized with 1 × 105 IrPySpz via IV or IM injection. Protection assay was performed by challenge with 5 × 104 viable P. yoelii sporozoites via IV injection 2 weeks after immunization. Naïve B6 mice and MHC-I- -Tg mice were also challenged as infection control. Parasite burden was described as a ratio of the absolute copy number of parasite-specific 18s rRNA to that of mouse GAPDH. is considered statistically significant, whereas N.S. means “not significant” in Figures 24.