Figure 1. Treg depletion+IL-2 enhances tumor therapy using VSV-loaded OT-I T cells.
(a) C57Bl/6 mice were seeded with s.c. B16ova tumors. Ten days later, mice received an intraperitoneal injection of anti-CD25 antibody PC-61 or a control IgG. Twenty-four hours later, mice were injected intraperitoneally with PBS or with rhIL-2 at a dose of 75,000 U/injection three times a day for 3 days. On the fourth day, a single further injection of IL-2 was given. Two and twenty-four hours after this last injection of IL-2/PBS, mice received an intravenous injection of PBS; 107 pfu of VSV-GFP (VSV); 1 × 106 untreated OT-I (OT-I), 1 × 106 OT-I loaded with VSV at a MOI of 1 (OT-I(VSV)). The dose of 1 × 106 OT-I was selected as this is known to be nontherapeutic in this B16ova model.31,41 (b) Survival of tumor-bearing mice treated as shown (n = 7/group), and as described in a earlier, is shown with time following tumor seeding. Data are representative of three separate experiments. (c) Long-term survivors cured of tumor by the treatments shown (long-term survivors, 1° challenge) were rechallenged 60 days following the initial tumor challenge with 5 × 105 B16ova tumor cells subcutaneously along with a group of naive C57Bl/6 mice. All of the naive mice succumbed to tumor by day 35 after challenge. Numbers of mice surviving this rechallenge in each group are shown (long-term survivors, rechallenge).