Intravenous immunoglobulin (IVIG) promotes brain repair and improves cognitive outcomes after traumatic brain injury in a FcγRIIB receptor-dependent manner.

Intravenous immunoglobulin (IVIG) is a promising immune-modulatory therapy for limiting harmful inflammation and associated secondary tissue loss in neurotrauma. Here, we show that IVIG therapy attenuates spatial learning and memory deficits following a controlled cortical impact mouse model of traumatic brain injury (TBI). These improvements in cognitive outcomes were associated with increased neuronal survival, an overall reduction in brain tissue loss, and a greater preservation of neural connectivity. Furthermore, we demonstrate that the presence of the main inhibitory FcγRIIB receptor is required for the beneficial effects of IVIG treatment in TBI, with our results simultaneously highlighting the role of this receptor in reducing secondary damage arising from brain injury.

CNS Antigen-Specific Neuroinflammation Attenuates Ischemic Stroke With Involvement of Polarized Myeloid Cells.

BACKGROUND AND OBJECTIVES: Experimental studies indicate shared molecular pathomechanisms in cerebral hypoxia-ischemia and autoimmune neuroinflammation. This has led to clinical studies investigating the effects of immunomodulatory therapies approved in multiple sclerosis on inflammatory damage in stroke. So far, mutual and combined interactions of autoimmune, CNS antigen-specific inflammatory reactions and cerebral ischemia have not been investigated so far. METHODS: Active MOG35-55 experimental autoimmune encephalomyelitis (EAE) was induced in male C57Bl/6J mice. During different phases of EAE, transient middle cerebral artery occlusion (tMCAO, 60 minutes) was induced. Brain tissue was analyzed for infarct size and immune cell infiltration. Multiplex gene expression analysis was performed for 186 genes associated with neuroinflammation and hypoxic-ischemic damage. RESULTS: Mice with severe EAE disease showed a substantial reduction in infarct size after tMCAO. Histopathologic analysis showed less infiltration of CD45+ hematopoietic cells in the infarct core of severely diseased acute EAE mice; this was accompanied by an accumulation of Arginase1-positive/Iba1-positive cells. Gene expression analysis indicated an involvement of myeloid cell-driven anti-inflammatory mechanisms in the attenuation of ischemic injury in severely diseased mice exposed to tMCAO in the acute EAE phase. DISCUSSION: CNS autoantigen-specific autoimmunity has a protective influence on primary tissue damage after experimental stroke, indicating a very early involvement of CNS antigen-specific, myeloid cell-associated anti-inflammatory immune mechanisms that mitigate ischemic injury in the acute EAE phase.

Antineonatal Fc Receptor Antibody Treatment Ameliorates MOG-IgG-Associated Experimental Autoimmune Encephalomyelitis.

BACKGROUND AND OBJECTIVES: Myelin oligodendrocyte glycoprotein antibody-associated disorder (MOGAD) is a rare, autoimmune demyelinating CNS disorder, distinct from multiple sclerosis and neuromyelitis optica spectrum disorder. Characterized by pathogenic immunoglobulin G (IgG) antibodies against MOG, a potential treatment strategy for MOGAD is to reduce circulating IgG levels, e.g., by interference with the IgG recycling pathway mediated by the neonatal Fc receptor (FcRn). Although the optic nerve is often detrimentally involved in MOGAD, the effect of FcRn blockade on the visual pathway has not been assessed. Our objective was to investigate effects of a monoclonal anti-FcRn antibody in murine MOG-IgG-associated experimental autoimmune encephalomyelitis (EAE). METHODS: We induced active MOG35-55 EAE in C57Bl/6 mice followed by the application of a monoclonal MOG-IgG (8-18C5) 10 days postimmunization (dpi). Animals were treated with either a specific monoclonal antibody against FcRn (α-FcRn, 4470) or an isotype-matched control IgG on 7, 10, and 13 dpi. Neurologic disability was scored daily on a 10-point scale. Visual acuity was assessed by optomotor reflex. Histopathologic hallmarks of disease were assessed in the spinal cord, optic nerve, and retina. Immune cell infiltration was visualized by immunohistochemistry, demyelination by Luxol fast blue staining and complement deposition and number of retinal ganglion cells by immunofluorescence. RESULTS: In MOG-IgG-augmented MOG35-55 EAE, anti-FcRn treatment significantly attenuated neurologic disability over the course of disease (mean area under the curve and 95% confidence intervals (CIs): α-FcRn [n = 27], 46.02 [37.89-54.15]; isotype IgG [n = 24], 66.75 [59.54-73.96], 3 independent experiments), correlating with reduced amounts of demyelination and macrophage infiltration into the spinal cord. T- and B-cell infiltration and complement deposition remained unchanged. Compared with isotype, anti-FcRn treatment prevented reduction of visual acuity over the course of disease (median cycles/degree and interquartile range: α-FcRn [n = 16], 0.50 [0.48-0.55] to 0.50 [0.48-0.58]; isotype IgG [n = 17], 0.50 [0.49-0.54] to 0.45 [0.39-0.51]). DISCUSSION: We show preserved optomotor response and ameliorated course of disease after anti-FcRn treatment in an experimental model using a monoclonal MOG-IgG to mimic MOGAD. Selectively targeting FcRn might represent a promising therapeutic approach in MOGAD.

Evaluation of diagnostic criteria and red flags of myelin oligodendrocyte glycoprotein encephalomyelitis in a clinical routine cohort.

AIMS: Myelin oligodendrocyte glycoprotein antibodies (MOG-IgG) have been proposed to define "MOG encephalomyelitis" (MOG-EM), with published diagnostic and "red flag" criteria. We aimed to evaluate these criteria in a routine clinical setting. METHODS: We retrospectively analyzed patients with borderline/positive MOG-IgG and applied the diagnostic and red flag criteria to determine likelihood of MOG-EM diagnosis. Para-/clinical parameters were described and analyzed with chi-square test. RESULTS: In total, 37 patients fulfilled MOG-EM diagnostic criteria (female-to-male ratio: 1.6:1, median onset age: 28.0 years [IQR 18.5-40.5], n = 8 with pediatric onset). In 24/37, red flags were present, predominantly MOG-IgG at assay cutoff and/or MRI lesions suggestive of multiple sclerosis (MS). As proposed in the consensus criteria, these patients should rather be described as "possible" MOG-EM. Of these, we classified 13 patients as "unlikely" MOG-EM in the presence of the red flag "borderline MOG-IgG" with negative MOG-IgG retest or coincidence of ≥1 additional red flag. This group mainly consisted of patients diagnosed with MS (n = 11). Frequency of cerebrospinal fluid (CSF-)-specific oligoclonal bands (OCB) is significantly lower in definite vs possible and unlikely MOG-EM (P = .0005). CONCLUSION: Evaluation of diagnostic and red flag criteria, MOG-IgG retesting (incl. change of assay), and CSF-specific OCB are relevant in clinical routine cohorts to differentiate MOG-EM from MS.

Functional relevance of the multi-drug transporter abcg2 on teriflunomide therapy in an animal model of multiple sclerosis.

BACKGROUND: The multi-drug resistance transporter ABCG2, a member of the ATP-binding cassette (ABC) transporter family, mediates the efflux of different immunotherapeutics used in multiple sclerosis (MS), e.g., teriflunomide (teri), cladribine, and mitoxantrone, across cell membranes and organelles. Hence, the modulation of ABCG2 activity could have potential therapeutic implications in MS. In this study, we aimed at investigating the functional impact of abcg2 modulation on teri-induced effects in vitro and in vivo. METHODS: T cells from C57BL/6 J wild-type (wt) and abcg2-knockout (KO) mice were treated with teri at different concentrations with/without specific abcg2-inhibitors (Ko143; Fumitremorgin C) and analyzed for intracellular teri concentration (HPLC; LS-MS/MS), T cell apoptosis (annexin V/PI), and proliferation (CSFE). Experimental autoimmune encephalomyelitis (EAE) was induced in C57BL/6J by active immunization with MOG35-55/CFA. Teri (10 mg/kg body weight) was given orally once daily after individual disease onset. abcg2-mRNA expression (spinal cord, splenic T cells) was analyzed using qRT-PCR. RESULTS: In vitro, intracellular teri concentration in T cells was 2.5-fold higher in abcg2-KO mice than in wt mice. Teri-induced inhibition of T cell proliferation was two fold increased in abcg2-KO cells compared to wt cells. T cell apoptosis demonstrated analogous results with 3.1-fold increased apoptosis after pharmacological abcg2-inhibition in wt cells. abcg2-mRNA was differentially regulated during different phases of EAE within the central nervous system and peripheral organs. In vivo, at a dosage not efficacious in wt animals, teri treatment ameliorated clinical EAE in abcg2-KO mice which was accompanied by higher spinal cord tissue concentrations of teri. CONCLUSION: Functional relevance of abcg2 modulation on teri effects in vitro and in vivo warrants further investigation as a potential determinant of interindividual treatment response in MS, with potential implications for other immunotherapies.

Vitamin D increases glucocorticoid efficacy via inhibition of mTORC1 in experimental models of multiple sclerosis.

The limited efficacy of glucocorticoids (GCs) during therapy of acute relapses in multiple sclerosis (MS) leads to long-term disability. We investigated the potential of vitamin D (VD) to enhance GC efficacy and the mechanisms underlying this VD/GC interaction. In vitro, GC receptor (GR) expression levels were quantified by ELISA and induction of T cell apoptosis served as a functional readout to assess synergistic 1,25(OH)2D3 (1,25D)/GC effects. Experimental autoimmune encephalomyelitis (MOG35-55 EAE) was induced in mice with T cell-specific GR or mTORc1 deficiency. 25(OH)D (25D) levels were determined in two independent cohorts of MS patients with stable disease or relapses either responsive or resistant to GC treatment (initial cohort: n = 110; validation cohort: n = 85). Gene expression of human CD8+ T cells was analyzed by microarray (n = 112) and correlated with 25D serum levels. In vitro, 1,25D upregulated GR protein levels, leading to increased GC-induced T cell apoptosis. 1,25D/GC combination therapy ameliorated clinical EAE course more efficiently than respective monotherapies, which was dependent on GR expression in T cells. In MS patients from two independent cohorts, 25D deficiency was associated with GC-resistant relapses. Mechanistic studies revealed that synergistic 1,25D/GC effects on apoptosis induction were mediated by the mTOR but not JNK pathway. In line, 1,25D inhibited mTORc1 activity in murine T cells, and low 25D levels in humans were associated with a reduced expression of mTORc1 inhibiting tuberous sclerosis complex 1 in CD8+ T cells. GR upregulation by 1,25D and 1,25D/GC synergism in vitro and therapeutic efficacy in vivo were abolished in animals with a T cell-specific mTORc1 deficiency. Specific inhibition of mTORc1 by everolimus increased the efficacy of GC in EAE. 1,25D augments GC-mediated effects in vitro and in vivo in a T cell-specific, GR-dependent manner via mTORc1 inhibition. These data may have implications for improvement of anti-inflammatory GC therapy.

Teriflunomide and monomethylfumarate target HIV-induced neuroinflammation and neurotoxicity.

HIV-associated neurocognitive disorders (HAND) affect about 50% of infected patients despite combined antiretroviral therapy (cART). Ongoing compartmentalized inflammation mediated by microglia which are activated by HIV-infected monocytes has been postulated to contribute to neurotoxicity independent from viral replication. Here, we investigated effects of teriflunomide and monomethylfumarate on monocyte/microglial activation and neurotoxicity. Human monocytoid cells (U937) transduced with a minimal HIV-Vector were co-cultured with human microglial cells (HMC3). Secretion of pro-inflammatory/neurotoxic cytokines (CXCL10, CCL5, and CCL2: p < 0.001; IL-6: p < 0.01) by co-cultures was strongly increased compared to microglia in contact with HIV-particles alone. Upon treatment with teriflunomide, cytokine secretion was decreased (CXCL10, 3-fold; CCL2, 2.5-fold; IL-6, 2.2-fold; p < 0.001) and monomethylfumarate treatment led to 2.9-fold lower CXCL10 secretion (p < 0.001). Reduced toxicity of co-culture conditioned media on human fetal neurons by teriflunomide (29%, p < 0.01) and monomethylfumarate (27%, p < 0.05) indicated functional relevance. Modulation of innate immune functions by teriflunomide and monomethylfumarate may target neurotoxic inflammation in the context of HAND.