CNS Parenchyma Research Articles

Truncated mini LRP1 transports cargo from luminal to basolateral side across the blood brain barrier

BackgroundThe most crucial area to focus on when thinking of novel pathways for drug delivery into the CNS is the blood brain barrier (BBB). A number of nanoparticulate formulations have been shown in earlier research to target receptors at the BBB and transport therapeutics into the CNS. However, no mechanism for CNS entrance and movement throughout the CNS parenchyma has been proposed yet. Here, the truncated mini low-density lipoprotein receptor-related protein 1 mLRP1_DIV* was presented as blood to brain transport carrier, exemplified by antibodies and immunoliposomes using a systematic approach to screen the receptor and its ligands’ route across endothelial cells in vitro.MethodsThe use of mLRP1_DIV* as liposomal carrier into the CNS was validated based on internalization and transport assays across an in vitro model of the BBB using hcMEC/D3 and bEnd.3 cells. Trafficking routes of mLRP1_DIV* and corresponding cargo across endothelial cells were analyzed using immunofluorescence. Modulation of γ-secretase activity by immunoliposomes loaded with the γ-secretase modulator BB25 was investigated in co-cultures of bEnd.3 mLRP1_DIV* cells and CHO cells overexpressing human amyloid precursor protein (APP) and presenilin 1 (PSEN1).ResultsWe showed that while expressed in vitro, mLRP1_DIV* transports both, antibodies and functionalized immunoliposomes from luminal to basolateral side across an in vitro model of the BBB, followed by their mLRP1_DIV* dependent release of the cargo. Importantly, functionalized liposomes loaded with the γ-secretase modulator BB25 were demonstrated to effectively reduce toxic Aß42 peptide levels after mLRP1_DIV* mediated transport across a co-cultured endothelial monolayer.ConclusionTogether, the data strongly suggest mLRP1_DIV* as a promising tool for drug delivery into the CNS, as it allows a straight transport of cargo from luminal to abluminal side across an endothelial monolayer and it’s release into brain parenchyma in vitro, where it exhibits its intended therapeutic effect.

Lipid-siRNA conjugate accesses perivascular transport and achieves durable knockdown throughout the central nervous system.

Short-interfering RNA (siRNA) has gained significant interest for treatment of neurological diseases by providing the capacity to achieve sustained inhibition of nearly any gene target. Yet, efficacious drug delivery throughout deep brain structures of the CNS remains a considerable hurdle for intrathecally administered therapeutics. We herein describe an albumin-binding lipid-siRNA conjugate that transports along meningeal and perivascular CSF pathways, leading to broad dispersion throughout the CNS parenchyma. We provide a detailed examination of the temporal kinetics of gene silencing, highlighting potent knockdown for up to five months from a single injection without detectable toxicity. Single-cell RNA sequencing further demonstrates gene silencing activity across diverse cell populations in the parenchyma and at brain borders, which may provide new avenues for neurological disease-modifying therapies.

Prebiotics Mitigate the Detrimental Effects of High-Fat Diet on memory, anxiety and microglia functionality in Ageing Mice

Ageing is characterised by a progressive increase in systemic inflammation and especially neuroinflammation. Neuroinflammation is associated with altered brain states that affect behaviour, such as an increased level of anxiety with a concomitant decline in cognitive abilities. Although multiple factors play a role in the development of neuroinflammation, microglia have emerged as a crucial target. Microglia are the only macrophage population in the CNS parenchyma that plays a crucial role in maintaining homeostasis and in the immune response, which depends on the activation and subsequent deactivation of microglia. Therefore, microglial dysfunction has a major impact on neuroinflammation. The gut microbiota has been shown to significantly influence microglia from birth to adulthood in terms of development, proliferation, and function. Diet is a key modulating factor that influences the composition of the gut microbiota, along with prebiotics that support the growth of beneficial gut bacteria. Although the role of diet in neuroinflammation and behaviour has been well established, its relationship with microglia functionality is less explored. This article establishes a link between diet, animal behaviour and the functionality of microglia. The results of this research stem from experiments on mouse behaviour, i.e., memory, anxiety, and studies on microglia functionality, i.e., cytochemistry (phagocytosis, cellular senescence, and ROS assays), gene expression and protein quantification. In addition, shotgun sequencing was performed to identify specific bacterial families that may play a crucial role in the brain function. The results showed negative effects of long-term consumption of a high fat diet on ageing mice, epitomised by increased body weight, glucose intolerance, anxiety, cognitive impairment and microglia dysfunction compared to ageing mice on a control diet. These effects were a consequence of the changes in gut microbiota modulated by the diet. However, by adding the prebiotics fructo- and galacto-oligosaccharides, we were able to mitigate the deleterious effects of a long-term high-fat diet.

Myelin-reactive B cells exacerbate CD4+ T cell-driven CNS autoimmunity in an IL-23-dependent manner

B cells and T cells collaborate in multiple sclerosis (MS) pathogenesis. IgH[MOG] mice possess a B cell repertoire skewed to recognize myelin oligodendrocyte glycoprotein (MOG). Here, we show that upon immunization with the T cell-obligate autoantigen, MOG[35-55], IgH[MOG] mice develop rapid and exacerbated experimental autoimmune encephalomyelitis (EAE) relative to wildtype (WT) counterparts, characterized by aggregation of T and B cells in the IgH[MOG] meninges and by CD4+ T helper 17 (Th17) cells in the CNS. Production of the Th17 maintenance factor IL-23 is observed from IgH[MOG] CNS-infiltrating and meningeal B cells, and in vivo blockade of IL-23p19 attenuates disease severity in IgH[MOG] mice. In the CNS parenchyma and dura mater of IgH[MOG] mice, we observe an increased frequency of CD4+PD-1+CXCR5- T cells that share numerous characteristics with the recently described T peripheral helper (Tph) cell subset. Further, CNS-infiltrating B and Tph cells from IgH[MOG] mice show increased reactive oxygen species (ROS) production. Meningeal inflammation, Tph-like cell accumulation in the CNS and B/Tph cell production of ROS were all reduced upon p19 blockade. Altogether, MOG-specific B cells promote autoimmune inflammation of the CNS parenchyma and meninges in an IL-23-dependent manner.

443 Myeloid Immunometabolic Reprogramming Mitigates Chronic Neurodegeneration After Experimental Traumatic Brain Injury

INTRODUCTION: Traumatic brain injury (TBI) induces immediate mechanical injury, including diffuse axonal shearing and myelin degradation. Epidemiological studies suggest a single, severe TBI initiates progressive neurodegeneration, including extensive white matter injury and culminating in long-term cognitive decline. While underlying mechanisms remain undefined, the degree of chronic inflammation correlates with delayed white matter tract damage after TBI. METHODS: Immune cell infiltration and activation was measured using preparative and analytical flow cytometry after controlled cortical impact, a pre-clinical model of focal penetrating injury, in adult mice. To assess T cell priming, APCs pulsed with myelin or isolated after experimental TBI were co-cultured with naÏve splenic T cells. Progressive neurodegeneration was assessed by histology and magnetic resonance imaging at eight weeks post-injury. RESULTS: Peripheral macrophages predominated as APCs within the CNS parenchyma after severe TBI. Myelin-pulsed APCs or APCs isolated after experimental TBI efficiently primed naÏve T cells ex vivo, generating myelin-reactive Th1/Th17 cells. Activity of the master metabolic regulator AMPK, previously shown to promote counter-inflammatory immune polarization, was decreased in myeloid cells after injury. Treatment with metformin, an AMPK activator, restored myeloid AMPK activity and attenuated neurodegenerative changes at eight weeks post-TBI. CONCLUSIONS: TBI-induced immunometabolic dysregulation allows generation of auto-reactive T cells that may contribute to chronic inflammation and progressive neurodegeneration. Metabolic reprogramming of myeloid cells via metformin restores AMPK activity and reduces progressive white matter loss after TBI, representing a potential therapeutic intervention to mitigate long-term consequences of TBI.

Innate lymphoid cells in neuroinflammation.

Innate lymphoid cells (ILCs) are largely tissue-resident cells that participate in the maintenance of tissue homeostasis and react early to inflammatory events. Mature ILCs are divided into three major groups based on the transcription factors required for their development and function. Under physiological conditions, ILCs are present within the choroid plexus and meninges while the CNS parenchyma is almost devoid of these cells. However, pathological conditions such as autoimmune neuroinflammation and viral infections of the CNS result in the infiltration of ILCs into parenchyma. In this article, we provide an overview of the involvement and function of the ILCs within the CNS during physiological conditions and in infections, autoimmune diseases, neurodegeneration, and injury.

CNS Radiotherapy As Bridging Prior to CAR T-Cell Therapy for Non-Hodgkin B-Cell Lymphoma

Introduction: Up to 80% of patients who receive CAR T-cell therapy (CAR T) for central nervous system lymphoma (CNSL) require bridging therapy, yet optimal regimens remain undefined. Radiotherapy is an established strategy for extracranial lymphoma that provides beneficial cytoreduction. However, CNS bridging radiotherapy (CNS-BRT) prior to CAR T is controversial due to concerns of potential enhanced neurotoxicity. We explored the safety and response profiles in patients treated with CNS-BRT prior to CAR T. Methods: We identified patients with non-hodgkin B-cell lymphoma who received CNS-BRT at our institution prior to commercial CAR T infusion. CNS-BRT was defined as treatment delivered between apheresis and CAR T infusion or within 30 days prior to apheresis, targeting the CNS parenchyma, leptomeninges, or epidural spine. Patients with epidural spine disease were included since the adjacent spinal cord is part of the treatment field. Safety was evaluated by rate of cytokine release syndrome (CRS) and immune effector associated neurotoxicity syndrome (ICANS) after CAR T. Best CNS response post CAR T was evaluated using the International Primary CNS Lymphoma Collaborative Group (IPCG) or Response Assessment in Neuro-Oncology (RANO) for parenchymal or leptomeningeal lesions, respectively. Cytoreduction from CNS-BRT was estimated by calculating the change in lesion size (sum of product diameter) from before and after CNS-BRT, but before CAR T infusion. Risk of any CNS relapse after CAR T was estimated using the Gray's method with death as a competing risk. Patients with epidural spine disease were not evaluate for CNS response or relapse. Results: 12 patients received CNS-BRT with median follow up of 8.5 months (range: 3.2 - 30.2), median age of 60 (30-76), median Karnofsky Performance Status (KPS) of 80 (range: 50 - 90). Histologies included diffuse large B cell (DLBCL) (n = 9), mantle cell (n = 2), and Burkitt lymphoma (n = 1), with disease localizing to the brain parenchyma (n = 6), leptomeninges (n = 4), and epidural spine (n = 2). 9 patients had secondary CNSL and 1 patient had primary CNSL. Prior to CNS-BRT, 11/12 patients had progressive disease. 5/12 patients had disease outside of the CNS. 5/12 patients received prior autologous hematopoietic stem cell transplantation. 9/12 patients received prior high dose methotrexate with median 46-day interval to CNS-BRT (range: 0 - 393). RT targets included whole brain (n = 3), involved site (partial) brain (n = 4), involved site spine (n = 4), and orbits (n = 1) with median dose 24 Gy (range: 15 - 33). CAR T products included Tisagenlecleucel (n = 4), Lisocabtagene maraleucel (n = 7), and Axicabtagene ciloleucel (n = 1). Among 10 patients with available toxicity grading, 6/10 experienced CRS (n = 1 grade (G) 1, n = 4 G2, and n = 1 G3), and 3/10 experienced ICANS (n = 1 G1, n = 1 G3, n = 1 G4). 6/10 patients required tocilizumab and/or steroids. CNS-BRT achieved a 74.4% (95% CI, 62.9 - 85.9) mean reduction in lesion size prior to CAR T infusion. Best CNS response after CAR T infusion included 3 complete responses (CR), 6 partial responses (PR), and 1 progressive disease (PD). The patients who achieved PR remained in PR at last follow up. The 12-month estimated risk of CNS progression after CNS-BRT and CAR T infusion was 20.0% (95% CI, 3- 49). CNS progression was not observed in patients who received involved site brain RT. Conclusion: Preliminary data suggest CNS-BRT achieves rapid cytoreduction prior to CAR T therapy and is associated with a favorable CNS response profile. While overall numbers are limited to date, the rate of severe CRS and ICANS is similar to that of historical series of CNSL patients treated with CAR T. However, a larger cohort will be required to determine the safety of CNS-BRT. These data support further study of RT, and exploration of involved site brain RT, as an effective bridging modality for CAR T-cell therapy in CNSL.

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

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.

CNSC-01. THE ROLE OF SEROTONERGIC RECEPTOR, HTR2B, ON MYELOID DERIVED SUPPRESSOR CELLS IN THE BRAIN METASTATIC ENVIRONMENT

Abstract In the United States, greater than 12% of cancer patients develop brain metastases (br-mets) and median survival remains an abysmal 4-6 months. Throughout the metastatic cascade, tumor cells attract and reprogram stromal cells, such as myeloid derived suppressor cells (MDSCs), which support cancer growth by promoting tissue remodeling, EMT, invasion, immunosuppression, angiogenesis. Once tumor cells have breached the brain’s CNS defenses, infiltrating immune cells can penetrate the glia limitans and enter the CNS parenchyma to help establish the brain metastatic niche. However, there is scant understanding of MDSC’s contribution to the brain metastatic microenvironment. The brain metastatic environment is particularly unique because CNS-resident cells such as microglia, astrocytes, choroid plexus, and neurons function as local mediators to alter invading immune cell plasticity and differentiation. We have demonstrated that MDSCs in the brain microenvironment respond to the neurotransmitter serotonin, upregulate the serotonergic receptor, HTR2B, resulting in increase pNF-κB and its associated signaling genes (IL-6, IL-1B, COX2, CXCL2, NOS2). Furthermore, HTR2B knockdown in MDSCs alters downregulates expression of pNF-κB signaling genes. Additionally, MDSCs in this environment support tumor cell proliferation while hindering their acquisition of neuronal traits. A better understanding of the role of HTR2B in brain metastasis may allow us to develop new treatment strategies for patients of this devastating disease.

Inconsistent Effects of Glatiramer Acetate Treatment in the 5xFAD Mouse Model of Alzheimer's Disease.

Alzheimer's disease (AD) is a chronic neurodegenerative disorder that involves strong inflammatory components. Aberrant and prolonged inflammation in the CNS is thought to contribute to the development of the pathology. The use of single cytokine approaches to curb or leverage inflammatory mechanisms for disease modifying benefit has often resulted in conflicting data. Furthermore, these treatments were usually delivered locally into the CNS parenchyma, complicating translational efforts. To overcome these hurdles, we tested the use of glatiramer acetate (GA) in reducing amyloid beta (Aβ) plaque pathology in the 5xFAD model of AD. GA immunizations were begun at the ages of 2.5 months, 5.5 months, and 8.5 months, and GA was delivered weekly for 8 weeks. While previous data describe potential benefits of GA immunization in decreasing Aβ levels in murine models of AD, we found modest decreases in Aβ levels if given during the development of pathology but, surprisingly, found increased Aβ levels if GA was administered at later stages. The impact of GA treatment was only significant for female mice. Furthermore, we observed no changes between microglial uptake of plaque, CD11c immunopositivity of microglia, or levels of TMEM119 and P2Ry12 on microglia. Overall, these data warrant exercising caution when aiming to repurpose GA for AD.

CNS radiotherapy as bridging prior to CAR T‐cell therapy for hematologic malignancies

Introduction: Up to 80% of patients who receive CAR T-cell therapy for central nervous system lymphoma (CNSL) require bridging therapy, yet optimal regimens remain undefined. Bridging radiotherapy (BRT) is an established strategy for extracranial lymphoma that provides beneficial cytoreduction. However, BRT for CNSL (CNS-BRT) is controversial due to concerns of potential enhanced neurotoxicity. We explored the safety and response profiles for CNS-BRT prior to CAR T therapy. Methods: We identified CAR T patients with hematologic malignancy at MSKCC who received CNS-BRT, defined as treatment delivered between cell collection and infusion to targets in CNS parenchyma, leptomeninges, or epidural space. Safety was evaluated by cytokine release syndrome (CRS), immune effector associated neurotoxicity syndrome (ICANS), and immune effector cell encephalopathy (ICE) scores, as documented by primary physician. Response was evaluated within the RT field for patients with baseline measurable disease using the International Primary CNS Lymphoma Collaborative Group (IPCG), Response Assessment in Neuro-Oncology (RANO), and Response Evaluation Criteria in Lymphoma (RECIL) radiographic criteria for parenchymal, leptomeningeal, and epidural lesions, respectively. Results: 11 patients received CNS-BRT with median follow up of 10.1 months (range: 1.1–25.9). At RT, median age was 51 (25–79), median KPS was 80 (50–90), and 9/11 patients had progressive CNS disease. 8/11 patients received prior methotrexate (high dose n = 7, intrathecal n = 1) with median 39-day interval to RT (0–179). Disease was localized to the brain parenchyma (n = 6), leptomeninges (n = 2), and epidural spine (n = 3). RT targets included whole brain (n = 3), involved site (partial) brain (n = 4), and involved site spine (n = 4), with median dose 24 Gy (20–30). Patient and CAR T cell characteristics are shown in Table 1. 4/10 patients experienced ICANS (n = 1 grade (G) 1, n = 1 G2, n = 1 G3, and n = 1 G4). 8/10 patients experienced CRS (n = 2 G1, n = 5 G2, and n = 1 G3). 6/11 patients required tocilizumab and/or steroids. Patients with G3/4 ICANS had decreased baseline ICE scores of 5 and 6, respectively. Median change in lesion size prior to CAR T infusion was -43.6% (-3.1% to -74.5%) among 7 evaluable patients. Best response included 6 partial responses (PR) and 4 complete responses (CR) at median 4.2 months (0.5–10.4). There were 3 CNS treatment failures, 1 in the leptomeninges and 2 in the paraspinal/epidural space. Keywords: Aggressive B-cell non-Hodgkin lymphoma, Cellular therapies, Radiation Therapy Conflicts of interests pertinent to the abstract. R. Shouval Other remuneration: Medexus Pharmaceuticals, Inc., MyBiotics P. B. Dahi Other remuneration: Curio Science LLC, Kite Pharmaceuticals, OncLive, Targeted Oncology R. J. Lin Consultant or advisory role: Kite, A Gilead Company M. L. Palomba Other remuneration: BeiGene, Ltd., Mustang Bio, Novartis, Synthekine, Inc. M. Perales Stock ownership: NexImmune, Omeros, Orca Biosystems, Inc. Other remuneration: ADC Therapeutics, Bristol-Myers Squibb, Cidara Therapeutics, Inc., CoImmune, Inc., Equillium, Inc., Incyte, Jazz Pharmaceuticals, Karyopharm, Kite Pharmaceuticals, Merck & Co Inc., Miltenyi Biotec Incorporated, MorphoSys AG, Novartis, Partners Therapeutics Inc., VectivBio AG, Vor Biopharma Inc. G. Salles Stock ownership: Owkin, Inc. Other remuneration: AbbVie, Aptitude Health, Bayer, BeiGene, Ltd., Bio Ascend, Bristol-Myers Squibb, Celgene, Epizyme, Everest Clinical Research Corporation, GenMab, Genentech, Gilead Pharmaceutical, Incyte, Ipsen, Janssen Pharmaceuticals, Inc., Loxo Oncology, Miltenyi Biotec Incorporated, MorphoSys AG, Nordic Nanovector ASA, Novartis, Physicians' Education Resource, RAPT Therapeutics, Regeneron Pharmaceuticals, Inc., Roche, Scientific Education Support Ltd., Takeda Millennium L. Falchi Consultant or advisory role: Genmab, Abbvie, Genentech, ADC therapeutics, Astrazeneca, Seagen, Roche Research funding: Genmab, Abbvie, Roche, Genentech Educational grants: Genmab C. Grommes Other remuneration: BTG International, Ono Pharma, Roche M. Scordo Consultant or advisory role: McKinsey & Company, Angiocrine Bioscience, Inc., Omeros Corporation, Kite – A Gilead Company Honoraria: i3Health, Medscape Research funding: Angiocrine Bioscience, Inc., and Omeros Corporation J. Yahalom Other remuneration: Convergent R.N.R Ltd. B. S. Imber Other remuneration: GT Medical Technologies, Inc.

Elevated Galectin-3 Is Associated with Aging, Multiple Sclerosis, and Oxidized Phosphatidylcholine-Induced Neurodegeneration.

Aging is a significant risk factor associated with the progression of CNS neurodegenerative diseases including multiple sclerosis (MS). Microglia, the resident macrophages of the CNS parenchyma, are a major population of immune cells that accumulate in MS lesions. While they normally regulate tissue homeostasis and facilitate the clearance of neurotoxic molecules including oxidized phosphatidylcholines (OxPCs), their transcriptome and neuroprotective functions are reprogrammed by aging. Thus, determining the factors that instigate aging associated microglia dysfunction can lead to new insights for promoting CNS repair and for halting MS disease progression. Through single-cell RNA sequencing (scRNAseq), we identified Lgals3, which encodes for galectin-3 (Gal3), as an age upregulated gene by microglia responding to OxPC. Consistently, excess Gal3 accumulated in OxPC and lysolecithin-induced focal spinal cord white matter (SCWM) lesions of middle-aged mice compared with young mice. Gal3 was also elevated in mouse experimental autoimmune encephalomyelitis (EAE) lesions and more importantly in MS brain lesions from two male and one female individuals. While Gal3 delivery alone into the mouse spinal cord did not induce damage, its co-delivery with OxPC increased cleaved caspase 3 and IL-1β within white matter lesions and exacerbated OxPC-induced injury. Conversely, OxPC-mediated neurodegeneration was reduced in Gal3-/- mice compared with Gal3+/+ mice. Thus, Gal3 is associated with increased neuroinflammation and neurodegeneration and its overexpression by microglia/macrophages may be detrimental for lesions within the aging CNS.SIGNIFICANCE STATEMENT Aging accelerates the progression of neurodegenerative diseases such as multiple sclerosis (MS). Understanding the molecular mechanisms of aging that increases the susceptibility of the CNS to damage could lead to new strategies to manage MS progression. Here, we highlight that microglia/macrophage-associated galectin-3 (Gal3) was upregulated with age exacerbated neurodegeneration in the mouse spinal cord white matter (SCWM) and in MS lesions. More importantly, co-injection of Gal3 with oxidized phosphatidylcholines (OxPCs), which are neurotoxic lipids found in MS lesions, caused greater neurodegeneration compared with injection of OxPC alone, whereas genetic loss of Gal3 reduced OxPC damage. These results demonstrate that Gal3 overexpression is detrimental to CNS lesions and suggest its deposition in MS lesions may contribute to neurodegeneration.

Single Cell Analysis of High-Parameter Histology Images Using Histoflow Cytometry.

Immunofluorescence histology is commonly used to study immune cells in tissues where the number of fluorescence parameters is normally limited to four or less. This makes it impossible to interrogate multiple subsets of immune cells in tissue with the same precision as flow cytometry. The latter, however, dissociates tissues and loses spatial information. To bridge the gap between these technologies, we developed a workflow to expand the number of fluorescence parameters that can be imaged on widely available microscopes. We instituted a method for identifying single cells in tissue and exporting the data for flow cytometry-based analysis. This histoflow cytometry technique successfully separates spectrally overlapping dyes and identifies similar numbers of cells in tissue sections as manual cell counts. Populations identified through flow cytometry-like gating strategies are mapped to the original tissue to spatially localize gated subsets. We applied histoflow cytometry to immune cells in the spinal cords of mice with experimental autoimmune encephalomyelitis. We ascertained that B cells, T cells, neutrophils, and phagocytes differed in their frequencies in CNS immune cell infiltrates and were increased relative to healthy controls. Spatial analysis determined that B cells and T cells/phagocytes preferentially localized to CNS barriers and parenchyma, respectively. By spatially mapping these immune cells, we inferred their preferred interacting partners within immune cell clusters. Overall, we demonstrate the ease and utility of histoflow cytometry, which expands the number of fluorescent channels used in conventional immunofluorescence and enables quantitative cytometry and spatial localization of histological analyses.

Peripheral T-Cell Lymphoma Manifesting as Multifocal Central Nervous System Disease with Prominent Spinal Cord Involvement (P2-13.001)

<h3>Objective:</h3> To emphasize the need for timely and wide-reaching diagnostic testing in the evaluation of acute-onset multifocal CNS disease with prominent spinal cord involvement. <h3>Background:</h3> Metastatic CNS neoplasms, although rare, should be considered early in rapidly declining patients with multifocal disease in whom immune-mediated or infectious etiologies have been excluded. <h3>Design/Methods:</h3> N/A <h3>Results:</h3> A 53-year-old male with Celiac disease on azathioprine presented with one-week of vertigo, diplopia, and dysarthria upon one-year of malaise and cachexia. The patient’s examination revealed right eyelid ptosis, bilateral abducens palsies, restricted up-gaze, dysarthria, and diffuse dysmetria and hyporeflexia. MRI showed a right T2 hyperintense contrast-enhancing cerebellar lesion and a small left cerebellar diffusion-restricting lesion. CSF was inflammatory (nucleated cell 6 cells/mcL, protein 181 mg/dL, glucose 30 mg/dL). Workup for autoimmune encephalitis, myelin-oligodendrocyte-glycoprotein-IgG, aquaporin-4-IgG, and infections etiologies were negative. He was empirically treated with intravenous methylprednisolone and immunoglobulin without benefit. He continued to decline and repeat CSF was again inflammatory (28 cells/mcL, protein 494 mg/dL), without clonal cells. Repeated MRI showed new left frontal leptomeningeal and cauda equina enhancement extending into the adjacent musculature. Electromyography showed proximal myopathy and subsequent biopsy was unrevealing. A bone marrow and brain biopsy were declined due to development of pulmonary embolism and multiorgan failure. He continued to decline and developed multifocal strokes, expiring 6 weeks after presentation. Autopsy demonstrated peripheral T cell lymphoma (PTLC). <h3>Conclusions:</h3> Intramedullary non-CNS spinal metastases represent less than 8.5% of all metastatic tumors and 3% of all spinal metastases. PTCL represents 15% of non-Hodgkin lymphomas and can rarely involve the CNS parenchyma or leptomeninges. Persistent enhancement, elevated protein, and minimal response to steroids or subsequent rebound should raise suspicion for neoplasm, especially considering these patients’ rapid decline can make CNS biopsy inadvisable later in the disease course. <b>Disclosure:</b> Dr. Singh has nothing to disclose. Dr. Carozza has nothing to disclose. Dr. Misulis has received publishing royalties from a publication relating to health care. Dr. Shah has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Horizon. Dr. Shah has received publishing royalties from a publication relating to health care.

Effects of a Small-Molecule Perforin Inhibitor in a Mouse Model of CD8 T Cell-Mediated Neuroinflammation.

Alteration of the blood-brain barrier (BBB) at the interface between blood and CNS parenchyma is prominent in most neuroinflammatory diseases. In several neurologic diseases, including cerebral malaria and Susac syndrome, a CD8 T cell-mediated targeting of endothelial cells of the BBB (BBB-ECs) has been implicated in pathogenesis. In this study, we used an experimental mouse model to evaluate the ability of a small-molecule perforin inhibitor to prevent neuroinflammation resulting from cytotoxic CD8 T cell-mediated damage of BBB-ECs. Using an in vitro coculture system, we first identified perforin as an essential molecule for killing of BBB-ECs by CD8 T cells. We then found that short-term pharmacologic inhibition of perforin commencing after disease onset restored motor function and inhibited the neuropathology. Perforin inhibition resulted in preserved BBB-EC viability, maintenance of the BBB, and reduced CD8 T-cell accumulation in the brain and retina. Therefore, perforin-dependent cytotoxicity plays a key role in the death of BBB-ECs inflicted by autoreactive CD8 T cells in a preclinical model and potentially represents a therapeutic target for CD8 T cell-mediated neuroinflammatory diseases, such as cerebral malaria and Susac syndrome.

Pathophysiology of myelin oligodendrocyte glycoprotein antibody disease.

Myelin Oligodendrocyte Glycoprotein Antibody Disease (MOGAD) is a spectrum of diseases, including optic neuritis, transverse myelitis, acute disseminated encephalomyelitis, and cerebral cortical encephalitis. In addition to distinct clinical, radiological, and immunological features, the infectious prodrome is more commonly reported in MOGAD (37-70%) than NMOSD (15-35%). Interestingly, pediatric MOGAD is not more aggressive than adult-onset MOGAD, unlike in multiple sclerosis (MS), where annualized relapse rates are three times higher in pediatric-onset MS. MOGAD pathophysiology is driven by acute attacks during which T cells and MOG antibodies cross blood brain barrier (BBB). MOGAD lesions show a perivenous confluent pattern around the small veins, lacking the radiological central vein sign. Initial activation of T cells in the periphery is followed by reactivation in the subarachnoid/perivascular spaces by MOG-laden antigen-presenting cells and inflammatory CSF milieu, which enables T cells to infiltrate CNS parenchyma. CD4+ T cells, unlike CD8+ T cells in MS, are the dominant T cell type found in lesion histology. Granulocytes, macrophages/microglia, and activated complement are also found in the lesions, which could contribute to demyelination during acute relapses. MOG antibodies potentially contribute to pathology by opsonizing MOG, complement activation, and antibody-dependent cellular cytotoxicity. Stimulation of peripheral MOG-specific B cells through TLR stimulation or T follicular helper cells might help differentiate MOG antibody-producing plasma cells in the peripheral blood. Neuroinflammatory biomarkers (such as MBP, sNFL, GFAP, Tau) in MOGAD support that most axonal damage happens in the initial attack, whereas relapses are associated with increased myelin damage.

SOX2 is essential for astrocyte maturation and its deletion leads to hyperactive behavior in mice.

Children with SOX2 deficiency develop ocular disorders and extra-ocular CNS anomalies. Animal data show that SOX2 is essential for retinal and neural stem cell development. In the CNS parenchyma, SOX2 is primarily expressed in astroglial and oligodendroglial cells. Here, we report a crucial role of astroglial SOX2 in postnatal brain development. Astroglial Sox2-deficient mice develop hyperactivity in locomotion and increased neuronal excitability in the corticostriatal circuit. Sox2 deficiency inhibits postnatal astrocyte maturation molecularly, morphologically, and electrophysiologically without affecting astroglia proliferation. Mechanistically, SOX2 directly binds to a cohort of astrocytic signature and functional genes, the expression of whichissignificantly reduced in Sox2-deficient CNS and astrocytes. Consistently, Sox2 deficiency remarkably reduces glutamate transporter expression and compromised astrocyte function of glutamate uptake.Our study provides insights into the cellular mechanisms underlying brain defects in children with SOX2 mutations and suggests a link of astrocyte SOX2 with extra-ocular abnormalities in SOX2-mutant subjects.

Microglia as Central Protagonists in the Chronic Stress Response

Chronic stress is a major risk factor for developing psychiatric conditions. In addition to elevating the levels of stress hormones released in the body, chronic stress activates the immune system, resulting in increased levels of proinflammatory cytokines and innate immune cells in the circulation of rodents and humans. Furthermore, exposure to chronic stress alters the phenotype of microglia, a population of innate immune cells that reside in the CNS parenchyma. In rodent models, chronic stress activates microglia in defined brain regions and induces changes in their phenotype and functional properties. In this review, we discussed how microglia are activated in stressful situations. Furthermore, we described how microglia affect the CNS environment during chronic stress, through the production of cytokines, the induction of reactive oxygen species, and phagocytosis. We suggested that, due to their strategic location as immune cells within the CNS, microglia are important players in the induction of psychopathologies after chronic stress.

Contribution of B cells to cortical damage in multiple sclerosis.

Multiple sclerosis is associated with lesions not just in the white matter, but also involving the cortex. Cortical involvement has been linked to greater disease severity and hence understanding the factor underlying cortical pathology could help identify new therapeutic strategies for multiple sclerosis. The critical role of B cells in multiple sclerosis has been clarified by multiple pivotal trials of B-cell depletion in people with multiple sclerosis. The presence of B-cell rich areas of meningeal inflammation in multiple sclerosis has been identified at all stages of multiple sclerosis. Leptomeningeal inflammation is associated with greater extent of cortical demyelination and neuronal loss and with greater disease severity. Recent studies have identified several potential mechanisms by which B cells may mediate cortical injury including antibody production, extracellular vesicles containing neurotoxic substances and production of pro-inflammatory cytokines. Additionally, B cells may indirectly mediate cortical damage through effects on T cells, macrophages or microglia. Several animal models replicate the meningeal inflammation and cortical injury noted in people with multiple sclerosis. Studies in these models have identified Bruton's tyrosine kinase inhibition and type II anti-CD20 antibodies as potential agents that can impact meningeal inflammation. Trials of anti-CD20 monoclonal antibodies in people with multiple sclerosis have unsuccessfully attempted to eliminate B cells in the leptomeninges. New strategies to target B cells in multiple sclerosis include Bruton's tyrosine kinase inhibition and cell-based therapies aimed at B cells infected with Epstein-Barr virus. Future studies will clarify the mechanisms by which B cells mediate cortical injury and treatment strategies that can target B cells in the leptomeninges and CNS parenchyma.

The Shape of μ-How Morphological Analyses Shape the Study of Microglia.

Microglia, the innate immune cells of the CNS parenchyma, serve as the first line of defense in a myriad of neurodevelopmental, neurodegenerative, and neuroinflammatory conditions. In response to the peripheral inflammation, circulating mediators, and other external signals that are produced by these conditions, microglia dynamically employ different transcriptional programs as well as morphological adaptations to maintain homeostasis. To understand these cells’ function, the field has established a number of essential analysis approaches, such as gene expression, cell quantification, and morphological reconstruction. Although high-throughput approaches are becoming commonplace in regard to other types of analyses (e.g., single-cell scRNA-seq), a similar standard for morphological reconstruction has yet to be established. In this review, we offer an overview of microglial morphological analysis methods, exploring the advantages and disadvantages of each, highlighting a number of key studies, and emphasizing how morphological analysis has significantly contributed to our understanding of microglial function in the CNS parenchyma. In doing so, we advocate for the use of unbiased, automated morphological reconstruction approaches in future studies, in order to capitalize on the valuable information embedded in the cellular structures microglia inhabit.