KS05.6.A T-CELL THERAPY COMBINED WITH LOW-INTENSITY PULSED FOCUSED ULTRASOUND, MICROBUBBLES AND POLY-ICLC PROMOTES THE PRESENTATION OF BRAIN-DERIVED ANTIGENS, BREAKING CNS TOLERANCE AND INDUCING ACTIVE T-CELL RESPONSES

• Published in: Neuro-oncology (Charlottesville, Va.) Va.), 2024-10, Vol.26 (Supplement_5), p.v7-v8
• Main Authors: Gallus, M, Yamamichi, A, Andres Arrieta, V, Saijo, A, Chuntova, P, Haegelin, J, Phyu, S, Phung, L, Long, J, Lakshmanachetty, S, Nejo, T, Okada, K, Chen, L, Habashy, K, Gould, A, Amidei, C, Chang, C, Stupp, R, Canney, M, Sonabend, A, Okada, H
• Format: Article
• Language: English
• ISSN: 1522-8517; 1523-5866
• DOI: 10.1093/neuonc/noae144.019

Abstract BACKGROUND Immunotherapies targeting glioma, such as chimeric antigen receptor (CAR) T cell therapies, offer new therapeutic opportunities; however, their application has yielded limited success. Due to the antigenic heterogeneity of gliomas, targeting a few or several antigens may still result in the recurrence with “antigen-loss” tumors, indicating a need to enhance the “epitope spreading” process where additional tumor antigens not targeted by the therapy are effectively presented to the immune system. However, due to the immune-privileged status of the brain parenchyma, attributed to natural anatomical barriers and the immunosuppression of the CNS parenchyma, neoplasms within the brain often evade detection by the peripheral immune system..Low-intensity pulsed focused ultrasound combined with microbubbles (LIPU/MB) has been recently shown to transiently open the blood-brain barrier (BBB), enabling penetration of cells and drug into the CNS. MATERIAL AND METHODS Using intravital two-photon imaging, two photon-microscopy, multiparametric spectral flow cytometry, and bone marrow chimera mice, alongside blood samples from glioblastoma patients treated with LIPU/MB, we examined whether LIPU/MB-induced transient BBB- opening promotes migration of CNS antigen-presenting cells into the periphery. Additionally, we developed new transgenic mice (GFAP-minigene mice) with intact BBB expressing four immunogenic peptides under the CNS-specific GFAP promoter, enabling assessment of the immunological relevance of LIPU/MB-mediated CNS antigen presentation to the peripheral immune system. RESULTS Within one hour after LIPU/MB treatment in colony-stimulating factor receptor 1 (CSFR1) reporter mice, we observed the migration of CSFR1+ immune cells from the brain parenchyma and perivascular space into the bloodstream, a phenomenon absent prior to LIPU/MB treatment. Spectral flow cytometry of bone marrow-chimera mice with CNS-restricted CX3CR1-GFP expression confirmed CNS-derived antigen-presenting cells in the blood following LIPU/MB. In GFAP-minigene mice, LIPU/MB combined with adoptive T cell transfer targeting CNS (minigene peptides) and toll-like receptor 3 agonist poly-ICLC, promoted CNS antigen-spreading, mirrored by the presence of antigen-specific T cells in cervical lymph nodes and brain, resulting in clinically symptomatic cytotoxic T cell responses in the CNS parenchyma. Furthermore, blood samples of glioblastoma patients undergoing LIPU/MB demonstrated