IMMU-68. SINGLE-CELL PROTEOMIC ANALYSIS OF IMMUNE CELL RESPONSE TO CHECKPOINT BLOCKADE USING 30-PARAMETER FLOW CYTOMETRY

s vi137 NEURO-ONCOLOGY • NOVEMBER 2018 suppress immunity, but rather, heightened interferon-(IFN)-γ reactivity. Addition of ICIs (to animals primed with RNA-NPs) augmented periph-eral/intratumoral PD-1+CD8+ cells and mediated synergistic anti-tumor efficacy in settings where ICIs alone did not confer therapeutic benefit. These synergistic effects were mediated by type-I-interferon released from PD-L1+ plasmacytoid dendritic-cells. In translational studies, personal-ized mRNA-NPs (from whole tumor-transcriptome) were safe and active in a client-owned canine with a spontaneous malignant glioma. In this patient, RNA-NPs elicited robust immunologic activity with increased percentages of activated PD-L1+ APCs and IFNγ+CD8+ cells. CONCLUSION: RNA-NPs elicit widespread immune activation concomitant with inducible PD-L1 expression on intratumoral APCs that can be therapeutically exploited. Since RNA-NPs bypass cost/complexity of cellular thera-peutics, are amenable to central distribution, and can be made within days of tumor resection, these formulations can be expeditiously translated as biomodulators of GBM immunogenicity.