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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 in 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. The work was supported by the VIB, an ERC Consolidator Grant TissueTreg (to A.L.), an ERC Proof of Concept Grant TreatBrainDamage (to A.L.), an ERC Starting Grant AstroFunc (to M.G.H.), an ERC Proof of Concept Grant AD-VIP (to M.G.H.), FWO Research Grant 1513616N (to M.G.H.), Thierry Latran Foundation Grant SOD-VIP (to M.G.H.), an ERNAET Chair (H2020-WIDESPREAD-2018-2020-6; NCBio: 951923; to M.G.H.), FWO Research Grants 1503420N (to E.P.) and 1513020N (to J.W.), an SAO-FRA pilot grant (20190032, to E.P.), and the Biotechnology and Biological Sciences Research Council through Institute Strategic Program Grant funding BBS/E/B/000C0427 and BBS/E/B/000C0428, and the Biotechnology and Biological Sciences Research Council Core Capability Grant to the Babraham Institute. E.P., V.L., M.M., P.G., J.W. and A.d.B. were supported by fellowships from the FWO. R.L. is a senior clinical investigator of FWO Flanders. P.B., O.A. and C.P.F. were supported by an ERA-NET-NEURON grant EJTC 2016 to C.P.F. and by the Netherlands Organization for Scientific research (NWO). The authors acknowledge the important contributions of J. Haughton (VIB) for mouse husbandry, M. Rincon (VIB) for advice on AAV design and production, K. Vennekens for technical support, P. -A. Penttila and the KUL FACS Core, J. Wouters and the KUL Molecular Small Animal Imaging Center (MoSAIC), S. Walker and the Babraham Institute Imaging Core, the VIB Bio-Imaging Core, the VIB Single Cell Sequencing Core, and R. Breedijk, M. Hink and the Leeuwenhoek Center for Advanced Microscopy at the University of Amsterdam.

Single domain antibodies (VHHs) are potentially disruptive therapeutics, with important biological value for treatment of several diseases, including neurological disorders. However, VHHs have not been widely used in the central nervous system (CNS), largely because of their restricted blood-brain barrier (BBB) penetration. Here, we propose a gene transfer strategy based on BBB-crossing adeno-associated virus (AAV)-based vectors to deliver VHH directly into the CNS. As a proof-of-concept, we explored the potential of AAV-delivered VHH to inhibit BACE1, a well-characterized target in Alzheimer's disease. First, we generated a panel of VHHs targeting BACE1, one of which, VHH-B9, shows high selectivity for BACE1 and efficacy in lowering BACE1 activity in vitro. We further demonstrate that a single systemic dose of AAV-VHH-B9 produces positive long-term (12 months plus) effects on amyloid load, neuroinflammation, synaptic function, and cognitive performance, in the AppNL-G-F Alzheimer's mouse model. These results constitute a novel therapeutic approach for neurodegenerative diseases, which is applicable to a range of CNS disease targets. We want to thank the collaborators of the VIB Nanobody Core and VIB Protein Core for their valuable contribution to the research presented in this paper. We thank Joost Schymkowitz, Frederic Rousseau, and Roosmarijn Vandenbroucke for discussions and advice. We thank Jeason Haughton for expert support with mouse husbandry. MM was supported by a predoctoral fellowship from the Fonds Wetenschappelijk Onderzoek (FWO) (SB/ 1S48018N). MYR received a postdoctoral fellowship from the FWO (133722/ 1204517N) and acknowledges the continuous support of the Fundacion Cardiovascular de Colombia. SID was supported by The Foundation for Alzheimer Research (SAO-FRA) (P#14006). MGH was supported by the Thierry Latran Foundation (SOD-VIP), FWO (Grant 1513616N), and European Research Council (ERC) (Starting Grant 281961—AstroFunc; Proof of Concept Grant 713755—AD-VIP). He is currently the ERANet Chair (NCBio) at i3S Porto funded by the European Commission (H2020-WIDESPREAD-2018- 2020-6; NCBio; 951923). Work in the BDS Lab is supported by the Opening the Future campaign of the KU Leuven, SAO-FRA (P#16017), FWO, KU Leuven, VIB, a Methusalem grant from KU Leuven and the Flemish Government, the Flanders Network for Dementia Research (VIND, Strategic Basic Research Grant 135043) and the Alzheimer’s Association. BDS is supported by the Geneeskundige Stichting Koningin Elisabeth and the Bax-Vanluffelen Chair for Alzheimer’s disease. The synopsis image was produced by David Pennington (@PenningtonArt.co.uk).

To improve the anti-tumor efficacy of immune checkpoint inhibitors, numerous combination therapies are under clinical evaluation, including with IL-12 gene therapy. The current study evaluated the simultaneous delivery of the cytokine and checkpoint-inhibiting antibodies by intratumoral DNA electroporation in mice. In the MC38 tumor model, combined administration of plasmids encoding IL-12 and an anti-PD-1 antibody induced significant anti-tumor responses, yet similar to the monotherapies. When treatment was expanded with a DNA-based anti-CTLA-4 antibody, this triple combination significantly delayed tumor growth compared to IL-12 alone and the combination of anti-PD-1 and anti-CTLA-4 antibodies. Despite low drug plasma concentrations, the triple combination enabled significant abscopal effects in contralateral tumors, which was not the case for the other treatments. The DNA-based immunotherapies increased T cell infiltration in electroporated tumors, especially of CD8

The brain is a site of relative immune privilege. Although CD4 T cells have been reported in the central nervous system, their presence in the healthy brain remains controversial, and their function remains largely unknown. We used a combination of imaging, single cell, and surgical approaches to identify a CD69+ CD4 T cell population in both the mouse and human brain, distinct from circulating CD4 T cells. The brain-resident population was derived through in situ differentiation from activated circulatory cells and was shaped by self-antigen and the peripheral microbiome. Single-cell sequencing revealed that in the absence of murine CD4 T cells, resident microglia remained suspended between the fetal and adult states. This maturation defect resulted in excess immature neuronal synapses and behavioral abnormalities. These results illuminate a role for CD4 T cells in brain development and a potential interconnected dynamic between the evolution of the immunological and neurological systems. VIDEO ABSTRACT. ispartof: CELL vol:182 issue:3 pages:625-+ ispartof: location:United States status: published

Neuroinflammation is often associated with blood-brain-barrier dysfunction, which contributes to neurological tissue damage. Here, we reveal the pathophysiology of Susac syndrome (SuS), an enigmatic neuroinflammatory disease with central nervous system (CNS) endotheliopathy. By investigating immune cells from the blood, cerebrospinal fluid, and CNS of SuS patients, we demonstrate oligoclonal expansion of terminally differentiated activated cytotoxic CD8+ T cells (CTLs). Neuropathological data derived from both SuS patients and a newly-developed transgenic mouse model recapitulating the disease indicate that CTLs adhere to CNS microvessels in distinct areas and polarize granzyme B, which most likely results in the observed endothelial cell injury and microhemorrhages. Blocking T-cell adhesion by anti-α4 integrin-intervention ameliorates the disease in the preclinical model. Similarly, disease severity decreases in four SuS patients treated with natalizumab along with other therapy. Our study identifies CD8+ T-cell-mediated endotheliopathy as a key disease mechanism in SuS and highlights therapeutic opportunities., Susac syndrome is an inflammatory pathology of the brain endothelium. Here the authors show that the pathology is driven by CD8 T cells attacking the endothelium, and that blocking T cell-endothelial adhesion ameliorates the disease in a mouse model, and associates with improved clinical score in 4 patients.

Central nervous system (CNS) inflammation occurs in a large number of neurological diseases. The type and magnitude of CNS inflammation, as well as the T-cell contribution, vary depending on the disease. Different animal models of neurological diseases have shown that T cells play an important role in CNS inflammation. Furthermore, recent studies of human neurological disorders have indicated a significant role for T cells in disease pathology. Nevertheless, how individual T-cell subsets affect neuronal survival, damage and/or loss remains largely unclear. In this review we discuss the processes by which T cells mediate either beneficial or deleterious effects within the CNS, with emphasis on the direct interaction between T cells and neurons, as occurs in multiple sclerosis, paraneoplastic cerebellar degeneration, and viral encephalitis. The therapeutic approaches targeting T cells and their mediators as treatment for neurological diseases are also described here.