FIG 6.

P. yoelii lisp2⁻ plasmei2⁻ GAP immunization induces long-term liver-specific CD8 T cell immunity. SW mice were immunized three times, challenged after 6 weeks by mosquito bite (Table 2), and then rechallenged i.v. with 7,000 luciferase-expressing P. yoelii sporozoites 40 days later. (A) Parasite liver burden was assessed at 42 h postinfection by bioluminescent imaging. (B to D) Mice were sacrificed and their livers perfused for isolation of liver nonparenchymal cells and phenotyping by flow cytometry. The total numbers of liver lymphocytes (B), CD8 T_EM (CD8⁺ CD62L⁻ KLRG1⁺ population) (C), and antigen-experienced CD8⁺ CXCR6⁺ T cells (CD8⁺ CD44^hi CXCR6⁺) (D) are shown compared to those in naive, challenged controls. (E) CD8 T cells were isolated from the livers of BALB/cJ 45 days after they had been immunized twice with lisp2⁻ plasmei2⁻ GAP. A total of 1.5 × 10⁶ liver CD8 T cells from immunized mice and an equivalent number from mock-immunized mice were injected i.v. into naive BALB/cJ mice. Twenty-four hours after the transfer, each mouse was infected i.v. with 1,500 luciferase-expressing wild-type sporozoites. Forty-four hours later, liver stage burden was quantified by in vivo bioluminescent imaging (total flux, y axis). Each point represents a single mouse. Statistical comparisons were performed by Mann-Whitney U test (*, P < 0.05; **, P < 0.01).