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BackgroundAquaporin 4 (AQP4) is considered a putative autoantigen in patients with Neuromyelitis optica (NMO), an autoinflammatory disorder of the central nervous system (CNS). HLA haplotype analyses of patients with NMO suggest a positive association with HLA-DRB1* 03:01. We previously showed that the human (h) AQP4 peptide 281-300 is the dominant immunogenic determinant of hAQP4 in the context of HLA-DRB1*03:01. This immunogenic peptide stimulates a strong Th1 and Th17 immune response. AQP4281-300-specific encephalitogenic CD4+ T cells should initiate CNS inflammation that results in a clinical phenotype in HLA-DRB1*03:01 transgenic mice.MethodsControlled study with humanized experimental animals. HLA-DRB1*03:01 transgenic mice were immunized with hAQP4281-300, or whole-length hAQP4 protein emulsified in complete Freund's adjuvant. Humoral immune responses to both antigens were assessed longitudinally. In vivo T cell frequencies were assessed by tetramer staining. Mice were followed clinically, and the anterior visual pathway was tested by pupillometry. CNS tissue was examined histologically post-mortem. Flow cytometry was utilized for MHC binding assays and to immunophenotype T cells, and T cell frequencies were determined by ELISpot assay.ResultsImmunization with hAQP4281-300 resulted in an in vivo expansion of antigen-specific CD4+ T cells, and an immunoglobulin isotype switch. HLA-DRB1*03:01 TG mice actively immunized with hAQP4281-300, or with whole-length hAQP4 protein were resistant to developing a neurological disease that resembles NMO. Experimental mice show no histological evidence of CNS inflammation, nor change in pupillary responses. Subsequent analysis reveals that a single amino acid substitution from aspartic acid in hAQP4 to glutamic acid in murine (m)AQP4 at position 290 prevents the recognition of hAQP4281-300 by the murine T cell receptor (TCR).ConclusionInduction of a CNS inflammatory autoimmune disorder by active immunization of HLA-DRB1*03:01 TG mice with human hAQP4281-300 will be complex due to a single amino acid substitution. The pathogenic role of T cells in this disorder remains critical despite these observations.

Brain parenchymal lesions are frequently observed on conventional magnetic resonance imaging (MRI) scans of patients with neuromyelitis optica (NMO) spectrum disorder, but the specific morphological and temporal patterns distinguishing them unequivocally from lesions caused by other disorders have not been identified. This literature review summarizes the literature on advanced quantitative imaging measures reported for patients with NMO spectrum disorder, including proton MR spectroscopy, diffusion tensor imaging, magnetization transfer imaging, quantitative MR volumetry, and ultrahigh-field strength MRI. It was undertaken to consider the advanced MRI techniques used for patients with NMO by different specialists in the field. Although quantitative measures such as proton MR spectroscopy or magnetization transfer imaging have not reproducibly revealed diffuse brain injury, preliminary data from diffusion-weighted imaging and brain tissue volumetry indicate greater white matter than gray matter degradation. These findings could be confirmed by ultrahigh-field MRI. The use of nonconventional MRI techniques may further our understanding of the pathogenic processes in NMO spectrum disorders and may help us identify the distinct radiographic features corresponding to specific phenotypic manifestations of this disease.

ImportanceMost patients with relapsing-remitting (RR) multiple sclerosis (MS) who receive approved disease-modifying therapies experience breakthrough disease and accumulate neurologic disability. High-dose immunosuppressive therapy (HDIT) with autologous hematopoietic cell transplant (HCT) may, in contrast, induce sustained remissions in early MS.ObjectiveTo evaluate the safety, efficacy, and durability of MS disease stabilization through 3 years after HDIT/HCT.Design, setting, and participantsHematopoietic Cell Transplantation for Relapsing-Remitting Multiple Sclerosis (HALT-MS) is an ongoing, multicenter, single-arm, phase 2 clinical trial of HDIT/HCT for patients with RRMS who experienced relapses with loss of neurologic function while receiving disease-modifying therapies during the 18 months before enrolling. Participants are evaluated through 5 years after HCT. This report is a prespecified, 3-year interim analysis of the trial. Thirty-six patients with RRMS from referral centers were screened; 25 were enrolled.InterventionsAutologous peripheral blood stem cell grafts were CD34+ selected; the participants then received high-dose treatment with carmustine, etoposide, cytarabine, and melphalan as well as rabbit antithymocyte globulin before autologous HCT.Main outcomes and measuresThe primary end point of HALT-MS is event-free survival defined as survival without death or disease activity from any one of the following outcomes: (1) confirmed loss of neurologic function, (2) clinical relapse, or (3) new lesions observed on magnetic resonance imaging. Toxic effects are reported using National Cancer Institute Common Terminology Criteria for Adverse Events.ResultsGrafts were collected from 25 patients, and 24 of these individuals received HDIT/HCT. The median follow-up period was 186 weeks (interquartile range, 176-250) weeks). Overall event-free survival was 78.4% (90% CI, 60.1%-89.0%) at 3 years. Progression-free survival and clinical relapse-free survival were 90.9% (90% CI, 73.7%-97.1%) and 86.3% (90% CI, 68.1%-94.5%), respectively, at 3 years. Adverse events were consistent with expected toxic effects associated with HDIT/HCT, and no acute treatment-related neurologic adverse events were observed. Improvements were noted in neurologic disability, quality-of-life, and functional scores.Conclusions and relevanceAt 3 years, HDIT/HCT without maintenance therapy was effective for inducing sustained remission of active RRMS and was associated with improvements in neurologic function. Treatment was associated with few serious early complications or unexpected adverse events.

Steroid resistance poses a major challenge for the management of autoimmune neuroinflammation. T helper 17 (TH17) cells are widely implicated in the pathology of steroid resistance; however, the underlying mechanisms are unknown. In this study, we identified that interleukin-1 receptor (IL-1R) blockade rendered experimental autoimmune encephalomyelitis (EAE) mice sensitive to dexamethasone (Dex) treatment. Interleukin-1β (IL-1β) induced a signal transducer and activator of transcription 5 (STAT5)–mediated steroid-resistant transcriptional program in TH17 cells, which promoted inflammatory cytokine production and suppressed Dex-induced anti-inflammatory genes. TH17-specific deletion of STAT5 ablated the IL-1β–induced steroid-resistant transcriptional program and rendered EAE mice sensitive to Dex treatment. IL-1β synergized with Dex to promote the STAT5-dependent expression of CD69 and the development of central nervous system (CNS)–resident CD69+ TH17 cells. Combined IL-1R blockade and Dex treatment ablated CNS-resident TH17 cells, reduced EAE severity, and prevented relapse. CD69+ tissue-resident TH17 cells were also detected in brain lesions of patients with multiple sclerosis. These findings (i) demonstrate that IL-1β–STAT5 signaling in TH17 cells mediates steroid resistance and (ii) identify a therapeutic strategy for reversing steroid resistance in TH17-mediated CNS autoimmunity. Editor's summary: The treatment of autoimmune neuroinflammatory diseases including multiple sclerosis (MS) is often hindered by steroid resistance, but the underlying mechanisms are not well defined. Miller-Little et al. used an experimental autoimmune encephalitis (EAE) mouse model to study TH17-mediated resistance to the steroid dexamethasone. IL-1β signaling in TH17 cells promoted a steroid-resistant transcriptional program that overrides dexamethasone-induced transcriptional responses, sustaining the expression of pro-inflammatory cytokines. EAE mice with a TH17-specific deletion of STAT5 became sensitive to dexamethasone treatment, and a combination of IL-1R blockade with dexamethasone prevented EAE relapse. These findings demonstrate that IL-1β/STAT5 signaling in TH17 cells mediates steroid resistance in neuroinflammation, highlighting this axis as a promising therapeutic target in MS. —Hannah Isles [ABSTRACT FROM AUTHOR]

Multiple sclerosis (MS) is thought to be a CD4+ T cell mediated autoimmune demyelinating disease of the central nervous system (CNS) that is rarely diagnosed during infancy. Cellular and molecular mechanisms that confer disease resistance in this age group are unknown. We tested the hypothesis that a differential composition of immune cells within the CNS modulates age-associated susceptibility to CNS autoimmune disease. C57BL/6 mice younger than eight weeks were resistant to experimental autoimmune encephalomyelitis (EAE) following active immunization with myelin oligodendrocyte glycoprotein (MOG) peptide (p) 35-55. Neonates also developed milder EAE after transfer of adult encephalitogenic T cells primed by adult or neonate antigen presenting cells (APC). There was a significant increase in CD45+ hematopoietic immune cells and CD45+ high side scatter granulocytes in the CNS of adults, but not in neonates. Within the CD45+ immune cell compartment of adults, the accumulation of CD4+ T cells, Gr-1+ and Gr-1- monocytes and CD11c+ dendritic cells (DC) was identified. A significantly greater percentage of CD19+ B cells in the adult CNS expressed MHC II than neonate CNS B cells. Only in the adult CNS could IFNγ transcripts be detected 10 days post immunization for EAE. IFNγ is highly expressed by adult donor CD4+ T cells that are adoptively transferred but not by transferred neonate donor cells. In contrast, IL-17 transcripts could not be detected in adult or neonate CNS in this EAE model, and neither adult nor neonate donor CD4+ T cells expressed IL-17 at the time of adoptive transfer.

MS is an inflammatory CNS disorder, which typically occurs in early adulthood and rarely in children. Here we tested whether functional maturation of innate immune cells may determine susceptibility to CNS autoimmune disease in EAE. Two-week-old mice were resistant to active EAE, which causes fulminant paralysis in adult mice; this resistance was associated with an impaired development of Th1 and Th17 cells. Resistant, young mice had higher frequencies of myeloid-derived suppressor cells and plasma-cytoid DCs. Furthermore, myeloid APCs and B cells from young mice expressed lower levels of MHC class II and CD40, produced decreased amounts of proinflammatory cytokines, and released enhanced levels of anti-inflammatory IL-10. When used as APCs, splenocytes from 2-week-old mice failed to differentiate naive T cells into Th1 and Th17 cells irrespective of the T-cell donor's age, and promoted development of Treg cells and Th2 cells instead. Adoptive transfer of adult APCs restored the ability of 2-week-old mice to generate encephalitogenic T cells and develop EAE. Collectively, these findings indicate that the innate immune compartment functionally matures during development, which may be a prerequisite for development of T-cell-mediated CNS autoimmune disease.

Experimental autoimmune encephalomyelitis (EAE) is a relevant animal model for the human demyelinating inflammatory disorder of the central nervous system (CNS), multiple sclerosis (MS). Induction of EAE by adoptive transfer allows studying the role of the donor T lymphocyte in disease pathogenesis. It has been challenging to reliably induce adoptive transfer EAE in C57BL/6 (H-2b) mice. The goal of this study was to develop a reproducible and high yield protocol for adoptive transfer EAE in C57BL/6 mice. A step-wise experimental approach permitted us to develop a protocol that resulted in a consistent relatively high disease incidence of ~70% in recipient mice. Donor mice were immunized with myelin oligodendrocyte glycoprotein (MOG)p35-55 in complete Freund's adjuvant (CFA) followed by pertussis toxin (PT). Only lymph node cells (LNC) isolated at day 12 post immunization, and restimulated in vitro for 72 hours with 10 μg/mL of MOGp35-55 and 0.5 ng/mL of interleukin-12 (IL-12) were able to transfer disease. The ability of LNC to transfer disease was associated with the presence of inflammatory infiltrates in the CNS at day 12. Interferon gamma (IFNγ) was produced at comparable levels in cell cultures prepared from mice at both day 6 and day 12 post immunization. By contrast, there was a trend towards a negative association between IL-17 and disease susceptibility in our EAE model. The amount of GM-CSF secreted was significantly increased in the culture supernatants from cells collected at day 12 post immunization versus those collected at day 6 post-immunization. Activated CD4+ T cells present in the day 12 LNC cultures maintained expression of the transcription factor T-bet, which has been shown to regulate the expression of the IL-23 receptor. Also, there was an increased prevalence of MOGp35-55-specific CD4+ T cells in day 12 LNC after in vitro re-stimulation. In summary, encephalitogenic LNC that adoptively transfer EAE in C57BL/6 mice were not characterized by a single biomarker in our study, but by a composite of inflammatory markers. Our data further suggest that GM-CSF expression by CD4+ T cells regulated by IL-23 contributes to their encephalitogenicity in our EAE model.

Experimental autoimmune encephalomyelitis (EAE) is a relevant animal model for the human demyelinating inflammatory disorder of the central nervous system (CNS), multiple sclerosis (MS). Induction of EAE by adoptive transfer allows studying the role of the donor T lymphocyte in disease pathogenesis. It has been challenging to reliably induce adoptive transfer EAE in C57BL/6 (H-2b) mice. The goal of this study was to develop a reproducible and high yield protocol for adoptive transfer EAE in C57BL/6 mice. A step-wise experimental approach permitted us to develop a protocol that resulted in a consistent relatively high disease incidence of ~70% in recipient mice. Donor mice were immunized with myelin oligodendrocyte glycoprotein (MOG)p35-55 in complete Freund's adjuvant (CFA) followed by pertussis toxin (PT). Only lymph node cells (LNC) isolated at day 12 post immunization, and restimulated in vitro for 72 hours with 10 μg/mL of MOGp35-55 and 0.5 ng/mL of interleukin-12 (IL-12) were able to transfer disease. The ability of LNC to transfer disease was associated with the presence of inflammatory infiltrates in the CNS at day 12. Interferon gamma (IFNγ) was produced at comparable levels in cell cultures prepared from mice at both day 6 and day 12 post immunization. By contrast, there was a trend towards a negative association between IL-17 and disease susceptibility in our EAE model. The amount of GM-CSF secreted was significantly increased in the culture supernatants from cells collected at day 12 post immunization versus those collected at day 6 post-immunization. Activated CD4+ T cells present in the day 12 LNC cultures maintained expression of the transcription factor T-bet, which has been shown to regulate the expression of the IL-23 receptor. Also, there was an increased prevalence of MOGp35-55-specific CD4+ T cells in day 12 LNC after in vitro re-stimulation. In summary, encephalitogenic LNC that adoptively transfer EAE in C57BL/6 mice were not characterized by a single biomarker in our study, but by a composite of inflammatory markers. Our data further suggest that GM-CSF expression by CD4+ T cells regulated by IL-23 contributes to their encephalitogenicity in our EAE model.

Objective: The radiologically isolated syndrome (RIS) represents the earliest detectable pre‐clinical phase of multiple sclerosis (MS). This study evaluated the impact of therapeutic intervention in preventing first symptom manifestation at this stage in the disease spectrum. Methods: We conducted a multi‐center, randomized, double‐blinded, placebo‐controlled study involving people with RIS. Individuals without clinical symptoms typical of MS but with incidental brain MRI anomalies consistent with central nervous system (CNS) demyelination were included. Within 12 MS centers in the United States, participants were randomly assigned 1:1 to oral dimethyl fumarate (DMF) 240 mg twice daily or placebo. The primary endpoint was the time to onset of clinical symptoms attributable to a CNS demyelinating event within a follow‐up period of 96 weeks. An intention‐to‐treat analysis was applied to all participating individuals in the primary and safety investigations. The study is registered at ClinicalTrials.gov, NCT02739542 (ARISE). Results: Participants from 12 centers were recruited from March 9, 2016, to October 31, 2019, with 44 people randomized to dimethyl fumarate and 43 to placebo. Following DMF treatment, the risk of a first clinical demyelinating event during the 96‐week study period was highly reduced in the unadjusted Cox proportional‐hazards regression model (hazard ratio [HR] = 0.18, 95% confidence interval [CI] = 0.05–0.63, p = 0.007). More moderate adverse reactions were present in the DMF (34 [32%]) than placebo groups (19 [21%]) but severe events were similar (DMF, 3 [5%]; placebo, 4 [9%]). Interpretation: This is the first randomized clinical trial demonstrating the benefit of a disease‐modifying therapy in preventing a first acute clinical event in people with RIS. ANN NEUROL 2023;93:604–614 [ABSTRACT FROM AUTHOR]