Fig. 1.

Analyses of tumor-reactive CD8⁺ T cell responses induced by the 47-LDA vaccine. a CTL activities against NXS2 and Neuro2a neuroblastoma cells as well as EL4 lymphoma (GD2⁺, H-2^b) cells in A/J mice immunized with the 47-LDA (closed symbols) or sham (open symbols) vector in the presence of IL-15 and IL-21 genes were analyzed in a standard ⁵¹Cr-release assay. All determinants were made in triplicate samples, and the SD was <10%. Results are presented as the means ± SD of three independent experiments. b CD8⁺ T cells from A/J mice (n = 8), which had been immunized with the 47-LDA vaccine in combination with the IL-15 and IL-21 genes and rejected s.c. NXS2 tumor challenge, were used for adoptive transfer (■). For the adoptive cell transfer, mice that were challenged s.c. with 10⁶ NXS2 cells were sublethally irradiated (500 rad) and treated by i.v. injection with freshly isolated CD8⁺ T cells from the cured mice (2 × 10⁷ cells). All recipient mice were vaccinated every 2 weeks by i.v. injection of 47-LDA-transfected DCs (2 × 10⁶ cells) and i.m. injection of IL-15 and IL-21 genes delivered at the time of immunization and 5 days latter, respectively. NXS2-challenged mice that received CD8⁺ T cells from untreated animals served as controls (□). Survival was defined as the point at which mice were killed due to extensive tumor growth. Kaplan–Meier survival plots were prepared, and significance was determined using logrank Mantel–Cox method