Astrocyte-targeted gene delivery of interleukin 2 specifically increases brain-resident regulatory T cell numbers and protects against pathological neuroinflammation

The ability of immune-modulating biologics to prevent and reverse pathology has transformed recent clinical practice. Full utility in the neuroinflammation space, however, requires identification of both effective targets for local immune-modulation and a delivery system capable of crossing the blood-brain-barrier. The recent identification and characterization of a small population of regulatory T (Treg) cells resident in the brain presents one such potential therapeutic target. Here we identified brain interleukin 2 (IL-2) levels as a limiting factor for brain-resident Treg cells. We developed a gene-delivery approach for astrocytes, with a small-molecule on-switch to allow temporal control, and enhanced production in reactive astrocytes to spatially direct delivery to inflammatory sites. Mice with brain-specific IL-2 delivery were protected from traumatic brain injury, stroke and multiple sclerosis models, without impacting the peripheral immune system. These results validate brain-specific IL-2 gene delivery as effective protection against neuroinflammation, and provide a versatile platform for delivery of diverse biologics to neuroinflammatory patients. Overall design: Wildtype mice, treated with PHP.GFAP-IL-2 (or PHP.GFAP-GFP control vector) on day -14, were given controlled cortical impacts to induce moderate traumatic brain injury (TBI) or sham surgery. Triplicate samples for were for TBI conditions. 14 days post-TBI, T cells (TCRß+CD45+CD11b-) and microglia (CD11b+CD45+) were sorted from the perfused brains for 10x single cell transcriptomics. For each experiment, approximately 8,700 cells were added to each channel for a targeted cell recovery of 5,000 cells. Post-cell count and quality control, the samples were immediately loaded onto the Chromium Controller.