CART123 cells exhibit characteristics of immunologic memory. (A) In a challenge/rechallenge model, NSG mice were sublethally irradiated and then injected via tail vein with saline or with 1 × 106 green fluorescent protein/luciferase+ MOLM14 cells on day 0. After BLI quantification of AML burden and randomization into treatment groups, CART123 cells (1 × 106) were injected IV on day 10, and mice were followed with serial BLI until AML eradication. Approximately 2 weeks after AML clearance, all mice were challenged (right) or rechallenged (left) with 1 × 106 MOLM14 cells and followed with weekly retro-orbital venous bleeding for T-cell quantification and by BLI for AML burden. (B) Summary of BLI radiance in CART123-treated mice following rechallenge or primary challenge with MOLM14. Each symbol represents an individual animal. The dashed line depicts the mean radiance measurement of untreated NSG mice. (C) CART123-treated, MOLM14-treated mice that are rechallenged with MOLM14 demonstrate increased numbers of peripheral CART123 cells in comparison with CART123-treated mice administered MOLM14 cells for the first time. Mice were bled 7 days prior to (day 28) and 7 days following (day 42) injection of MOLM14 cells. CART123 cells were identified as live, singlet, human CD45+ CD3+ CAR+ cells per the gating strategy in supplemental Figure 7 and quantified using Countbright beads. (D) Representative mouse (the highest blue data point from Figure 5B) showing that initial failure to reject MOLM14 is associated with low CART123 cell numbers in peripheral blood and that late rejection is accompanied by emergence of CART123 cells. Results are representative of 2 to 5 independent experiments. NS, nonsignificant.
