IMMU-52. LOW-INTENSITY PULSED ULTRASOUND CONDUCTS ANTIGEN-INDEPENDENT T CELL HOMING INTO THE BRAIN PARENCHYMA WITH THE INTACT BLOOD-BRAIN BARRIER

Abstract

Abstract The blood-brain barrier (BBB) protects the brain parenchyma from excessive inflammation but also leads to poor immune cell homing, hampering the success of immunotherapies, such as ones for low-grade glioma, where the BBB is intact. Low-intensity pulsed ultrasound (LIPU) combined with the application of microbubbles allows the non-invasive, transient opening of the BBB and recent studies have observed immune cell infiltration into malignant gliomas following LIPU. While these data warrant mechanistic investigations on the effects of LIPU in preclinical settings, most mouse models of malignant glioma already display BBB disruption. Therefore, to study whether LIPU affects antigen-specific immune cell trafficking through the BBB, we created a novel immunocompetent mouse model of non-tumor bearing mice that display an intact BBB and express a minigene cassette encoding for four immunogenic peptides in glia cells under the glial fibrillary acidic protein (GFAP) promotor. These peptides are either presented by major histocompatibility complex (MHC) class I: human melanoma antigen glycoprotein (gp) 100 and lymphocytic choriomeningitis virus (LCMV)gp31) or class II: LCMV gp66 and tyrosinase-related protein 1. Minigene expression in astrocytes induced antigen-specific T cell proliferation and Interferon-γ release in vitro. Intravenous adoptive T cell transfer of naïve or respectively CD3/CD28-coactivated antigen-specific CD 8 T cells targeting gp100 peptide followed by immediate LIPU treatment induced T cell homing into the CNS parenchyma, and astrocyte-T cell interaction was confirmed by ex-vivo two-photon imaging. Furthermore, some animals that underwent immediate LIPU treatment after transfer of preactivated antigen-specific T cells developed neurological deficits such as ataxia, while no deficits were observed in those animals that underwent LIPU but did not receive T cells or received activated T cells but did not undergo LIFU treatment. In conclusion, LIPU might be a novel effective tool to support antigen-independent immune cell homing with the intact BBB.