Antigen presentation, but not antibody secretion, by B cells drives CNS autoimmunity induced by immunization with human MOG.

Dimethyl fumarate (DMF) (BG-12, Tecfidera) is a fumaric acid ester (FAE) that was advanced as a multiple sclerosis (MS) therapy largely for potential neuroprotection as it was recognized that FAEs are capable of activating the antioxidative transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2) pathway. However, DMF treatment in randomized controlled MS trials was associated with marked reductions in relapse rate and development of active brain MRI lesions, measures considered to reflect CNS inflammation. Here, we investigated the antiinflammatory contribution of Nrf2 in DMF treatment of the MS model, experimental autoimmune encephalomyelitis (EAE). C57BL/6 wild-type (WT) and Nrf2-deficient (Nrf2 −/− ) mice were immunized with myelin oligodendrocyte glycoprotein (MOG) peptide 35-55 (p35-55) for EAE induction and treated with oral DMF or vehicle daily. DMF protected WT and Nrf2 −/− mice equally well from development of clinical and histologic EAE. The beneficial effect of DMF treatment in Nrf2 −/− and WT mice was accompanied by reduced frequencies of IFN-γ and IL-17-producing CD4 + cells and induction of antiinflammatory M2 (type II) monocytes. DMF also modulated B-cell MHC II expression and reduced the incidence of clinical disease in a B-cell-dependent model of spontaneous CNS autoimmunity. Our observations that oral DMF treatment promoted immune modulation and provided equal clinical benefit in acute EAE in Nrf2 −/− and WT mice, suggest that the antiinflammatory activity of DMF in treatment of MS patients may occur through alternative pathways, independent of Nrf2.multiple sclerosis | dimethyl fumarate | Nrf2 | EAE | M2 monocytes

Laquinimod is a novel oral drug that is currently being evaluated for the treatment of relapsing-remitting (RR) multiple sclerosis (MS). Using the animal model for multiple sclerosis, experimental autoimmune encephalomyelitis (EAE), we examined how laquinimod promotes immune modulation. Oral laquinimod treatment reversed established RR-EAE and was associated with reduced central nervous system (CNS) inflammation, decreased Th1 and Th17 responses, and an increase in regulatory T cells (Treg). In vivo laquinimod treatment inhibited donor myelin-specific T cells from transferring EAE to naive recipient mice. In vivo laquinimod treatment altered subpopulations of myeloid antigen presenting cells (APC) that included a decrease in CD11c+CD11b+CD4+ dendritic cells (DC) and an elevation of CD11bhiGr1hi monocytes. CD11b+ cells from these mice exhibited an anti-inflammatory type II phenotype characterized by reduced STAT1 phosphorylation, decreased production of IL-6, IL-12/23 and TNF, and increased IL-10. In adoptive transfer, donor type II monocytes from laquinimod-treated mice suppressed clinical and histologic disease in recipients with established EAE. As effects were observed in both APC and T cell compartments, we examined whether T cell immune modulation occurred as a direct effect of laquinimod on T cells, or as a consequence of altered APC function. Inhibition of Th1 and Th17 differentiation was observed only when type II monocytes or DC from laquinimod-treated mice were used as APC, regardless of whether myelin-specific T cells were obtained from laquinimod-treated or untreated mice. Thus, laquinimod modulates adaptive T cell immune responses via its effects on cells of the innate immune system, and may not influence T cells directly.

Newly formed synapses undergo maturation during ontogenetic development via mechanisms that remain poorly understood. We show that maturation of the presynaptic endocytotic machinery in CNS neurons requires substitution of the adaptor protein 3 (AP-3) with AP-2 at the presynaptic plasma membrane. In mature synapses, AP-2 associates with the intracellular domain of the neural cell adhesion molecule (NCAM). NCAM promotes binding of AP-2 over binding of AP-3 to presynaptic membranes, thus favoring the substitution of AP-3 for AP-2 during formation of mature synapses. The presynaptic endocytotic machinery remains immature in adult NCAM-deficient (NCAM−/−) mice accumulating AP-3 instead of AP-2 and its partner protein AP180 in synaptic membranes and vesicles. NCAM deficiency or disruption of the NCAM/AP-2 complex in wild-type (NCAM+/+) neurons by overexpression of AP-2 binding-defective mutant NCAM interferes with efficient retrieval of the synaptic vesicle v-SNARE synaptobrevin 2. Abnormalities in synaptic vesicle endocytosis and recycling may thus contribute to neurological disorders associated with mutations in NCAM.

Objective:Studies evaluating T-cell recognition of myelin oligodendrocyte glycoprotein (MOG) in multiple sclerosis (MS) and its model, experimental autoimmune encephalomyelitis (EAE), have focused mostly on its 117 amino acid (aa) extracellular domain, especially peptide (p) 35-55. We characterized T-cell responses to the entire 218 aa MOG sequence, including its transmembrane and cytoplasmic domains.Methods:T-cell recognition in mice was examined using overlapping peptides and intact full-length mouse MOG. EAE was evaluated by peptide immunization and by adoptive transfer of MOG epitope-specific T cells. Frequency of epitope-specific T cells was examined by ELISPOT.Results:Three T-cell determinants of MOG were discovered in its transmembrane and cytoplasmic domains, p119–132, p181–195, and p186–200. Transmembrane MOG p119-132 induced clinical EAE, CNS inflammation, and demyelination as potently as p35-55 in C57BL/6 mice and other H-2b strains. p119-128 contained its minimal encephalitogenic epitope. p119-132 did not cause disease in EAE-susceptible non-H-2b strains, including Biozzi, NOD, and PL/J. MOG p119-132–specific T cells produced Th1 and Th17 cytokines and transferred EAE to wild-type recipient mice. After immunization with full-length MOG, a significantly higher frequency of MOG-reactive T cells responded to p119-132 than to p35-55, demonstrating that p119-132 is an immunodominant encephalitogenic epitope. MOG p181-195 did not cause EAE, and MOG p181-195–specific T cells could not transfer EAE into wild-type or highly susceptible T- and B-cell–deficient mice.Conclusions:Transmembrane and cytoplasmic domains of MOG contain immunodominant T-cell epitopes in EAE. A CNS autoantigen can also contain nonpathogenic stimulatory T-cell epitopes. Recognition that a myelin antigen contains multiple encephalitogenic and nonencephalitogenic determinants may have implications for therapeutic development in MS.

Objective:Recently, we reported that the 218 amino acid murine full-length myelin oligodendrocyte glycoprotein (MOG) contains novel T-cell epitopes p119-132, p181-195, and p186-200, located within its transmembrane and cytoplasmic domains, and that p119-132 is its immunodominant encephalitogenic T-cell epitope in mice. Here, we investigated whether the corresponding human MOG sequences contain T-cell epitopes in patients with multiple sclerosis (MS) and healthy controls (HC).Methods:Peripheral blood T cells from patients with MS and HC were examined for proliferation to MOG p119-130, p181-195, p186-200, and p35-55 by fluorescence-activated cell sorting analysis using carboxylfluorescein diacetate succinimidyl ester dilution assay. Intracellular production of proinflammatory cytokines was analyzed by flow cytometry.Results:MOG p119-130, p181-195, and p186-200 elicited significantly greater T-cell responses than p35-55 in patients with MS. T cells from patients with MS proliferated significantly more strongly to MOG p119-130 and p186-200 than did T cells from HC. Further, MOG p119-130–specific T cells exhibited Th17 polarization, suggesting this T-cell epitope may be relevant to MS pathogenesis.Conclusions:Transmembrane and cytoplasmic MOG domains contain potent T-cell epitopes in MS. Recognition of these determinants is important when evaluating T-cell responses to MOG in MS and may have implications for development of myelin antigen-based therapeutics.

Serum antibodies against amyloid-β peptide (Aβ) in humans with or without diagnosis of Alzheimer's disease (AD) indicate the possibility of immune responses against brain antigens. In an unbiased screening for antibodies directed against brain proteins, we found in AD patients high serum levels of antibodies against the neuronal cytoskeletal protein ankyrin G (ankG); these correlated with slower rates of cognitive decline. Neuronal expression of ankG was higher in AD brains than in nondemented age-matched healthy control subjects. AnkG was present in exosomal vesicles, and it accumulated in β-amyloid plaques. Active immunization with ankG of arcAβ transgenic mice reduced brain β-amyloid pathology and increased brain levels of soluble Aβ(42). AnkG immunization induced a reduction in β-amyloid pathology, also in Swedish transgenic mice(.) Anti-ankG monoclonal antibodies reduced Aβ-induced loss of dendritic spines in hippocampal ArcAβ organotypic cultures. Together, these data established a role for ankG in the human adaptive immune response against resident brain proteins, and they show that ankG immunization reduces brain β-amyloid and its related neuropathology.

No abstract