IMMU-27. IMMUNE CHECKPOINT BLOCKADE OF EX VIVO EXPANDED T CELLS FOR USE IN ADOPTIVE CELLULAR THERAPY (ACT) FOR GLIOBLASTOMA

ABSTRACT: Abstract BACKGROUND Despite aggressive treatments, GBM continues to have unacceptably high mortality rates. Immune-checkpoint blockade and ACT have shown excellent results in other solid tumors, especially in melanoma. Unfortunately, these results have not been extrapolated to GBM. We have developed a novel platform for ACT using tumor mRNA-pulsed dendritic cells(DCs) to in-vitro expand polyclonal populations of tumor-reactive T-cells. This platform has shown promising effects in preclinical brain tumor models (Flores et al OncoImmunology 2015, Wildes et al CCR 2018, Flores et al NatureComm 2018) and being evaluated in clinical trials at UF Health (NCT02465268,NCT03334305). STUDY OBJECTIVE Evaluate whether immune-checkpoint blockade during ex-vivo expansion of antigen-specific T-cells impact their use in ACT. METHODS CMVpp65 was used as model antigen for in-vitro activation of T-cells. Mature pp65 mRNA-pulsed DCs from CMV+ healthy donors were co-cultured with T-cells in IL2-containing medium for 15days. We tested four checkpoint inhibitor groups: PD1(n= 6), PDL1(n= 4), TIM3(n= 7) and PD1+TIM3(n= 6) that were compared with non-blockade group, respectively. Checkpoint blockade was performed every 3days. T-cell proliferation, immune-phenotyping, and IFN-g release were analyzed. RESULTS Cell proliferation was lower in all the blockade groups but significantly lower in the TIM3 (p= 0.03) and TIM3+PD1 (p= 0.01) blockade groups. TIM3 expression was significantly lower in the TIM3 (p= 0.006) and PD1+TIM3 blockade groups (p= 0.0001). There was a trend of reduced pp65 tetramer positive in the TIM3 and PD1+TIM3 blockade groups (PD1+TIM3 subgroup at 3mcg/mL, p= 0.02) and lower INFg release in the TIM3 and PD1+TIM3 blockade groups. CONCLUSION The exact role of checkpoints during expansion of T-cells for ACT is not well understood. In our study checkpoint blockade with PD-1 or TIM-3 alone or in combination did not enhance T-cell expansion or function, in fact, appeared to have an inhibitory effect on measured parameters. Our results suggest that TIM-3 may have an activating role in our system.

SUBMITTER: Ogando-Rivas E 

PROVIDER: S-EPMC6846700 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature