Figure 6. Therapeutic vaccination synergizes with checkpoint blockade to improve outcome.

A. Mice were inoculated with 2500 BCR-ABL⁺ leukemic cells at d0, and then rechallenged with one of four different treatments. 1) No treatment (Black); 2) Homologous vaccination with Lymphocytic Choriomeningitis Virus (LCMV) Armstrong at day 7, day 14, and day 21, with 200μg exogenous BAp peptide delivered i.v. at three and five days post-infection (days 10, 12, 17, 19, 24, 26) (Brown); 3) Heterologous vaccination with LCMV-Armstrong at day 7, LM-BAp at day 14, and Vesicular Stomatitis Virus (VSV) Indiana at day 21, with with 200μg exogenous BAp peptide delivered i.v. at three and five days post-infection (days 10, 12, 17, 19, 24, 26), (Blue); 4) as in 3, except with 200μg of anti-PDL1 and 200μg of anti-CTLA4 twice per week from day 7 to day 80, (Green). Surviving mice were euthanized at day 80 post-leukemia inoculation. Shown are survival curves; Log-Rank (Mantel-Cox) test was used to analyze statistics. B. Mice were treated as in A, but treatment was started on the same day as leukemia challenge. Mice were euthanized at day 21 and BAp:I-A^b-specific T cells were harvested and enumerated. Shown are BAp:I-A^b-specific Log (Y+1) T cell counts; two or more independent experiments shown for each infection. Groups were compared with Kruskal-Wallace and Dunn’s test; no significant differences were found. Two or more independent experiments with 10 or more replicates are shown for each group.