CTL responses in infected/nontreated mice and infected/immunotherapy–treated animals. (A) Expression of IFNγ⁺ in CTLs. Mice were infected neonatally and immunotherapy treated as indicated and IFNγ was assayed by flow cytometry in CD8⁺ T cells in 8-week-old mice. Three mice per group were used in 3 independent experiments. Data are presented as means ± SEM. The statistical significance between groups was established using the Student t test. **P < .01. (B) Expression of GzmB (Gzm) in CTLs. Experiments were conducted as in panel A with an anti-Gzm antibody. Kinetic expression of PD-1 at the surface of CD8⁺ T cells in spleens (C) and lymph nodes (D). Mice were neonatally infected, 667 immunotherapy treated or not, and PD-1 was assayed by flow cytometry at the surface of CD8⁺ T cells at various time points. Values are the means ± SEM of 3 independent experiments conducted with 2 mice per time point. Data corresponding to 667-F(ab′)₂– and 672-treated mice are presented in supplemental Figure 2.