Conformational epitopes of myelin oligodendrocyte glycoprotein are targets of potentially pathogenic antibody responses in multiple sclerosis

<p>Abstract</p> <p>Background</p> <p>Myelin/oligodendrocyte glycoprotein (MOG) is a putative autoantigen in multiple sclerosis (MS). Establishing the pathological relevance and validity of anti-MOG antibodies as biomarkers has yielded conflicting reports mainly due to different MOG isoforms used in different studies. Because epitope specificity may be a key factor determining anti-MOG reactivity we aimed at identifying <it>a priori </it>immunodominant MOG epitopes by monoclonal antibodies (mAbs) and at assessing clinical relevance of these epitopes in MS.</p> <p>Methods</p> <p>Sera of 325 MS patients, 69 patients with clinically isolated syndrome and 164 healthy controls were assayed by quantitative, high-throughput ELISA for reactivity to 3 different MOG isoforms, and quantitative titers correlated with clinical characteristics. mAbs defined unique immunodominant epitopes distinct to each of the isoforms.</p> <p>Results</p> <p>In the majority of human samples anti-MOG levels were skewed towards low titers. However, in 8.2% of samples high-titer anti-MOG antibodies were identified. In contrast to anti-MOG reactivity observed in a mouse model of MS, in patients with MS these never reacted with ubiquitously exposed epitopes. Moreover, in patients with relapsing-remitting MS high-titer anti-MOG IgG correlated with disability (EDSS; Spearman r = 0.574; p = 0.025).</p> <p>Conclusions</p> <p>Thus high-titer reactivity likely represents high-affinity antibodies against pathologically relevant MOG epitopes, that are only present in a small proportion of patients with MS. Our study provides valuable information about requirements of anti-MOG reactivity for being regarded as a prognostic biomarker in a subtype of MS.</p

Distribution of Renin Activity and Angiotensinogen in Rat Brain Effects of Dietary Sodium Chloride Intake on Brain Renin

Abstract The purpose of this study was to investigate the biochemistry and the regulation of the brain renin-angiotensin system in the Sprague-Dawley rat. Renin activity and angiotensinogen concentrations (direct and indirect radioimmunoassays) were measured in several brain areas and in neuroendocrine glands. Regional renin activities were measured in separate groups of rats on high and low NaCl diets. Mean tissue renin activities ranged from 2.2±0.6 to 54.4±19.7 fmol/mg protein per h (mean of 7±SD), with the highest amounts in pineal, pituitary, and ponsmedulla. NaCl depletion increased renin activity in selected regions; based on estimates of residual plasma contamination (despite perfusion of brains with saline), increased renin activity of pineal gland and posterior pituitary was attributed to higher plasma renin. To eliminate contamination by plasma renin, 16-h-nephrectomized rats were also studied. In anephric rats, NaCl depletion increased renin activity by 92% in olfactory bulbs and by 97% in anterior pituitary compared with NaCI-replete state. These elevations could not be accounted for by hyperreninemia. Brain renin activity was low and was unaffected by dietary NaCl in amygdala, hypothalamus, striatum, frontal cortex, and cerebellum. In contrast to renin, highest angiotensinogen concentrations were measured in hypothalamus and cerebellum. Overall, angiotensinogen measurements with the direct and the indirect assays were highly correlated (n = 56, r = 0.96, P &lt; 0.001). We conclude that (a) NaCl deprivation increases renin in olfactory bulbs and anterior pituitary of the rat, unrelated to contamination by plasma renin; and (b) the existence of angiotensinogen, the precursor of angiotensins, is demonstrated by direct radioimmunoassay throughout the brain and in neuroendocrine glands

Human Nerve Growth Factor Protects Common Marmosets against Autoimmune Encephalomyelitis by Switching the Balance of T Helper Cell Type 1 and 2 Cytokines within the Central Nervous System

Multiple sclerosis is a demyelinating disorder of the central nervous system (CNS), in which an immune attack directed against myelin constituents causes myelin destruction and death of oligodendrocytes, the myelin-producing cells. Here, the efficacy of nerve growth factor (NGF), a growth factor for neurons and oligodendrocytes, in promoting myelin repair was evaluated using the demyelinating model of experimental allergic encephalomyelitis (EAE) in the common marmoset. Surprisingly, we found that NGF delayed the onset of clinical EAE and, pathologically, prevented the full development of EAE lesions. We demonstrate by immunocytochemistry that NGF exerts its antiinflammatory effect by downregulating the production of interferon γ by T cells infiltrating the CNS, and upregulating the production of interleukin 10 by glial cells in both inflammatory lesions of EAE and normal-appearing CNS white matter. Thus, NGF, currently under investigation in human clinical trials as a neuronal trophic factor, may be an attractive candidate for therapy of autoimmune demyelinating disorders

Effective Antigen-Specific Immunotherapy in the Marmoset Model of Multiple Sclerosis

Mature T cells initially respond to Ag by activation and expansion, but high and repeated doses of Ag cause programmed cell death and can suppress T cell-mediated diseases in rodents. We evaluated repeated systemic Ag administration in a marmoset model of experimental allergic encephalomyelitis that closely resembles the human disease multiple sclerosis. We found that treatment with MP4, a chimeric, recombinant polypeptide containing human myelin basic protein and human proteolipid protein epitopes, prevented clinical symptoms and did not exacerbate disease. CNS lesions were also reduced as assessed in vivo by magnetic resonance imaging. Thus, specific Ag-directed therapy can be effective and nontoxic in primates. The Journal of Immunology, 2001, 166: 2116 -2121. M ultiple sclerosis (MS) 4 is a paralytic disease involving destruction of myelin sheaths surrounding axons in the CNS (1, 2). MS affects young adults, most often women residing in northern latitudes. The disease exhibits relapsing and remitting symptoms including disturbances in vision, speech, coordination, and cognition as well as weakness, spasticity, and paralysis (1, 2). Lymphocytic infiltration in the CNS white matter and immune reactions against myelin Ags indicate an autoimmune etiology for MS (1-8). Allergic encephalomyelitis was first observed as a side effect of the rabies vaccine prepared from rabbit brains by Pasteur in the 1880s (see Ref. 3). Rivers and others showed that the CNS inflammation was caused not by the rabies virus but by immune sensitization to the combination of adjuvant and brain tissue contaminating the vaccine (3, 4). Experimental allergic encephalomyelitis (EAE) models in various animal species, typically rodents, were later developed by immunization with myelin proteins in adjuvant or by the adoptive transfer of myelinreactive T cells, causing inflammatory damage to the white matter (1-6). Rodent EAE is the most widely used disease model despite important differences from MS (2). Encephalitogenic CD4 ϩ T cells are believed to initiate and perpetuate EAE and MS and thus constitute a therapeutic target (1-8). Abundant myelin protein Ags, including myelin basic protein (MBP) and proteolipid protein (PLP) as well as the less abundant Ags, myelin oligodendrocyte glycoprotein (MOG) and myelin-associated glycoprotein (MAG), are recognized by T cells in MS patients (9 -11). T cell responses against MBP and PLP may occur at an increased frequency in MS patients compared with controls (1, 2, 11, 12). Ag-specific immunotherapies directed at T cells could avoid the harmful side effects of general immunosuppressive treatments. We have investigated a potential immunotherapy for MS based on our observation that T cells undergo apoptosis both in vitro and in vivo when exposed to high or repeated doses of their cognate Ag (13, To present a broad array of potential epitopes to reactive T cells, we constructed MP4, a protein chimera of the 21.5-kDa isoform of human MBP, and a modified form of human PLP, termed PLP4, that lacks the hydrophobic domains of the protein but includes all of the known T cell epitopes (19 -21). MP4 is processed into multiple determinants and can eliminate rodent EAE by promoting tolerance to different epitopes In a few instances, EAE and Ag treatments have been studied in nonhuman primates. EAE was originally induced in rhesus macaques using CNS homogenates or purified MBP (3, 4, 30 -32). It was also found that repeated injections of MBP could arrest EAE The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact

Antibodies to native myelin oligodendrocyte glycoprotein are serologic markers of early inflammation in multiple sclerosis

Myelin oligodendrocyte glycoprotein (MOG) is an integral membrane protein expressed in CNS oligodendrocytes and outermost myelin lamellae. Anti-MOG Abs cause myelin destruction (demyelination) in animal models of multiple sclerosis (MS); however, such pathogenic Abs have not yet been characterized in humans. Here, a method that specifically detects IgG binding to human MOG in its native, membrane-embedded conformation on MOG-transfected mammalian cells was used to evaluate the significance of these auto Abs. Compared with healthy controls, native MOG-specific IgGs were most frequently found in serum of clinically isolated syndromes (P < 0.001) and relapsing-remitting MS (P < 0.01), only marginally in secondary progressive MS (P < 0.05), and not at all in primary progressive MS. We demonstrate that epitopes exposed in this cell-based assay are different from those exposed on the refolded, extracellular domain of human recombinant MOG tested by solid-phase ELISA. In marmoset monkeys induced to develop MS-like CNS inflammatory demyelination, IgG reactivity against the native membrane-bound MOG is always detected before clinical onset of disease (P < 0.0001), unlike that against other myelin constituents. We conclude that (i) epitopes displayed on native, glycosylated MOG expressed in vivo are early targets for pathogenic Abs; (ii) these Abs, which are not detected in solid-phase assays, might be the ones to play a pathogenic role in early MS with predominant inflammatory activity; and (iii) the cell-based assay provides a practical serologic marker for early detection of CNS autoimmune demyelination including its preclinical stage at least in the primate MS model