Figure 4.

CD8⁺ T cell requirement for SFV-IL-12 + anti-CD137 treatment efficacy. (a) C57BL/6 female mice were inoculated in the flank with 5 × 10⁵ B16-OVA cells on day 0 and then received intratumorally saline (first panel) or 10⁸ viral particles (vp) of SFV-IL-12 (rest of the panels) on day 7. On days 7, 10, and 14 mice treated with saline received intraperitoneally 100 µg of rat immunoglobulin G (IgG) and mice treated with SFV-IL-12 received a course of anti-CD137 mAb as in Figure 1. Depletions of CD4⁺, CD8_β⁺, and NK1.1⁺ cells were performed by intraperitoneal injection of 100 µg of specific antibodies administered at days 6, 10, 15, 21, and 28 for αCD4⁺ and αCD8⁺ and at days 6, 8, 10, 12, 15, 21, and 28 for αNK1.1⁺. Each curve represents the evolution of the mean tumor diameter for each individual mouse. The numbers in the right lower corner of each graph indicate the number of tumor-free mice on day 70 relative to the total number of animals in each group, and the percentage of sustained complete tumor regressions, respectively. (b) Kaplan–Meier plot of mouse survival. The different groups were compared with the log-rank test. **P < 0.01;***P < 0.001. The graphs correspond to pooled data from two independent experiments with similar results. α, anti-; SFV-IL-12, Semliki Forest virus encoding interleukin-12.