CD19 targets in the brain parenchyma attracts murine CD19-directed CAR T cells to infiltrate 2259766

Abstract

Abstract Introduction Neurotoxicity is a common complication of CD19-directed CAR T cell therapy for leukemia and lymphoma patients. We have previously shown that murine CD19-directed CAR T cells can induce neurotoxicity in immunocompetent non-tumor bearing mice. There is concern that CAR T cells have targets other than B cells in the brain so we are investigating whether CAR T cells infiltrate the normal brain in a targeted fashion, or if they are simply surveilling. Methods Wild type BALB/c mice received 10x10^6 murine CD19-directed CAR T cells and 10x10^6 mock-GFP T cells I.V.. We characterized T and B cells distribution in brain, dura, skull, and spleen using flow cytometry. Then longitudinally tracked the behavior of T cells in the brain and meninges using in vivo two photon imaging. Finally, we assessed CAR T cell distribution in an immunocompetent CD19+ RCAS-TVA glioma model. Results CAR to mock T cell ratios in the brain and leptomeninges are 6 fold higher than in spleen (n = 6 mice, p = 0.0001) on day 6, suggesting they are preferentially infiltrating and not a reflection of relative abundance. In vivo two photon imaging showed many extravasated and actively migrating CAR T cells are in the dura and leptomeninges, with far fewer in the parenchyma. No mock T cells were seen in brain parenchyma (n = 3 mice). When an infiltrative CD19+ brain tumor target is present, CAR T cells successfully infiltrate the brain parenchyma more than both non-target brain tumor and non-tumor bearing mice. Conclusion CAR T cells are rarely seen in the brain parenchyma in non-tumor bearing mice. However, massive CAR T cell infiltration in the brain parenchyma is seen with CD19+ infiltrative brain tumor targets. The ability of CD19 directed CAR T cells infiltrating CNS after target stimulation has therapeutic implications for treating CNS autoimmunity and malignancy. Funding Source NIH R37CA275954 (PI: Juliane Gust), NIH R03NS135446 (PI: Juliane Gust), and NIH K08NS118138 (PI: Juliane Gust) Topic Categories Neuroimmunology (NEUR)