Stefan Nessler

Intrathecal pathogenic anti–aquaporin-4 antibodies in early neuromyelitis optica†

The serum of most neuromyelitis optica (NMO) patients contains autoantibodies (NMO‐IgGs) directed against the aquaporin‐4 (AQP4) water channel located on astrocyte foot processes in the perivessel and subpial areas of the brain. Our objectives were to determine the source of central nervous system (CNS) NMO‐IgGs and their role in disease pathogenesis.

Identification of Epstein-Barr virus proteins as putative targets of the immune response in multiple sclerosis

MS is a chronic inflammatory and demyelinating disease of the CNS with as yet unknown etiology. A hallmark of this disease is the occurrence of oligoclonal IgG antibodies in the cerebrospinal fluid (CSF). To assess the specificity of these antibodies, we screened protein expression arrays containing 37,000 tagged proteins. The 2 most frequent MS-specific reactivities were further mapped to identify the underlying high-affinity epitopes. In both cases, we identified peptide sequences derived from EBV proteins expressed in latently infected cells. Immunoreactivities to these EBV proteins, BRRF2 and EBNA-1, were significantly higher in the serum and CSF of MS patients than in those of control donors. Oligoclonal CSF IgG from MS patients specifically bound both EBV proteins. Also, CD8(+) T cell responses to latent EBV proteins were higher in MS patients than in controls. In summary, these findings demonstrate an increased immune response to EBV in MS patients, which suggests that the virus plays an important role in the pathogenesis of disease.

Immunopathogenesis and immunotherapy of multiple sclerosis

Multiple sclerosis (MS) is a chronic disease of the CNS that is characterized by inflammation, demyelination and axonal injury. Although the etiology of MS is still unknown, many findings point toward a central role for the immune system in the pathogenesis of the disease. This hypothesis is strongly supported by the beneficial effects of immunomodulatory and immunosuppressive therapy on disease activity. Over the past few years, substantial progress has been made in deciphering the immune response in MS. Although animal models have advanced our knowledge of basic mechanisms of immune responses in the CNS, recent studies have also highlighted the differences between MS and its animal equivalent, experimental autoimmune encephalomyelitis. New immunotherapeutic agents have been developed and evaluated in clinical trials. Here, we review current knowledge of the immunopathogenesis of MS and corresponding animal models of disease, and discuss new immunointerventional treatment strategies based on changing pathogenetic concepts.

Identification of a pathogenic antibody response to native myelin oligodendrocyte glycoprotein in multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system. Although the cause of MS is still uncertain, many findings point toward an ongoing autoimmune response to myelin antigens. Because of its location on the outer surface of the myelin sheath and its pathogenicity in the experimental autoimmune encephalomyelitis model, myelin oligodendrocyte glycoprotein (MOG) is one of the potential disease-causing self antigens in MS. However, the role of MOG in the pathogenesis of MS has remained controversial. In this study we addressed the occurrence of autoantibodies to native MOG and its implication for demyelination and axonal loss in MS. We applied a high-sensitivity bioassay, which allowed detecting autoantibodies that bind to the extracellular part of native MOG. Antibodies, mostly IgG, were found in sera that bound with high affinity to strictly conformational epitopes of the extracellular domain of MOG. IgG but not IgM antibody titers to native MOG were significantly higher in MS patients compared with different control groups with the highest prevalence in primary progressive MS patients. Serum autoantibodies to native MOG induced death of MOG-expressing target cells in vitro. Serum from MS patients with high anti-MOG antibody titers stained white matter myelin in rat brain and enhanced demyelination and axonal damage when transferred to autoimmune encephalomyelitis animals. Overall these findings suggest a pathogenic antibody response to native MOG in a subgroup of MS patients.

Pathogenesis of multiple sclerosis: an update on immunology

&NA; Multiple sclerosis is characterized by demyelination and chronic inflammation of the central nervous system. Extensive studies in the animal model experimental autoimmune encephalomyelitis have suggested that multiple sclerosis is an autoimmune disorder mediated by myelin‐specific CD4 T cells secreting T helper type 1 cytokines and tumor necrosis factor alpha. This concept has been widely used to develop new experimental therapies. However, recent findings in both experimental autoimmune encephalomyelitis and multiple sclerosis question a simple CD4 T helper type 1 T cell paradigm and provide evidence for the role of various immune cells in the pathogenesis of experimental autoimmune encephalomyelitis and multiple sclerosis. In this paper we review recent progress and discuss the implications for new therapeutic strategies. Curr Opin Neurol 15:227‐231.

Immunomodulatory synergy by combination of atorvastatin and glatiramer acetate in treatment of CNS autoimmunity

One approach to improving efficacy in MS therapy is to identify medications that provide additive or synergistic benefit in combination. Orally administered cholesterol-lowering HMG-CoA reductase inhibitors (known as statins), which exhibit immunomodulatory properties and are effective in treatment of the MS model EAE, are being tested in MS. As atorvastatin can enhance protective Th2 responses and has a different mechanism of action than glatiramer acetate (GA), a parenterally administered immunomodulatory agent approved for MS treatment, we tested whether the combination of these agents could be beneficial in EAE. Combination therapy using suboptimal doses of atorvastatin and GA prevented or reversed clinical and histologic EAE. Secretion of proinflammatory Th1 cytokines was reduced--and conversely Th2 cytokine secretion was increased--in these mice, but not in mice treated with each drug alone at the same doses. Monocytes treated with the combination of suboptimal doses of atorvastatin and GA secreted an antiinflammatory type II cytokine pattern and, when used as APCs, promoted Th2 differentiation of naive myelin-specific T cells. Our results demonstrate that agents with different mechanisms of immune modulation can combine in a synergistic manner for the treatment of CNS autoimmunity and provide rationale for testing the combination of atorvastatin and GA in MS.

Assessment of lesion pathology in a new animal model of MS by multiparametric MRI and DTI

Magnetic resonance imaging (MRI) is the gold standard for the detection of multiple sclerosis (MS) lesions. However, current MRI techniques provide little information about the structural features of a brain lesion with inflammatory cell infiltration, demyelination, gliosis, acute axonal damage and axonal loss. To identify methods for a differentiation of demyelination, inflammation, and axonal damage we developed a novel mouse model combining cuprizone-induced demyelination and experimental autoimmune encephalomyelitis. MS-like brain lesions were assessed by T1-weighted, T2-weighted, and magnetization transfer MRI as well as by diffusion tensor imaging (DTI). T2-weighted MRI differentiated control and diseased mice, while T1-weighted MRI better reflected the extent of inflammation and axonal damage. In DTI, axonal damage and cellular infiltration led to a reduction of the axial diffusivity, whereas primary demyelination after cuprizone treatment was reflected by changes in radial but not axial diffusivity. Importantly, alterations in radial diffusivity were less pronounced in mice with demyelination, inflammation, and acute axonal damage, indicating that radial diffusivity may underestimate demyelination in acute MS lesions. In conclusion, the combined information from different DTI parameters allows for a more precise identification of solely demyelinated lesions versus demyelinated and acutely inflamed lesions. These findings are of relevance for offering individualized, stage-adapted therapies for MS patients.

The antidepressant venlafaxine ameliorates murine experimental autoimmune encephalomyelitis by suppression of pro-inflammatory cytokines

Antidepressants are known to impact on the immune system. In this study, we examined the immunomodulatory properties of venlafaxine, a selective serotonin/norepinephrine reuptake inhibitor (SNRI), in murine experimental autoimmune encephalomyelitis (EAE), a T-cell-mediated CNS demyelinating disease model of multiple sclerosis. EAE was induced in SJL/J mice by adoptive transfer of myelin-specific T cells. Mice received different doses of venlafaxine before induction and after onset of disease. Sustained daily oral treatment with 6, 20 and 60 mg/kg significantly ameliorated the clinical symptoms of the disease compared to vehicle during both preventive and therapeutic intervention. Venlafaxine suppressed the generation of pro-inflammatory cytokines IL-12 p40, TNF-alpha and IFN-gamma in encephalitogenic T-cell clones, splenocytes and peritoneal macrophages in vitro. It also diminished mRNA expression of a number of inflammatory genes in the inflamed CNS tissue, among them CD3, CD8, Granzyme B, IL-12 p40, IFN-gamma, TNF-alpha and the chemokines Ccl2 and RANTES, whereas the expression of brain-derived neurotrophic factor was increased. These findings demonstrate the strong immunomodulatory property of the selective SNRI venlafaxine. Further studies are warranted to clarify whether venlafaxine may exert similar effects in humans.

Active Immunization with Amyloid-β 1–42 Impairs Memory Performance through TLR2/4-Dependent Activation of the Innate Immune System

Active immunization with amyloid-β (Aβ) peptide 1–42 reverses amyloid plaque deposition in the CNS of patients with Alzheimer’s disease and in amyloid precursor protein transgenic mice. However, this treatment may also cause severe, life-threatening meningoencephalitis. Physiological responses to immunization with Aβ1–42 are poorly understood. In this study, we characterized cognitive and immunological consequences of Aβ1–42/CFA immunization in C57BL/6 mice. In contrast to mice immunized with myelin oligodendrocyte glycoprotein (MOG)35–55/CFA or CFA alone, Aβ1–42/CFA immunization resulted in impaired exploratory activity, habituation learning, and spatial-learning abilities in the open field. As morphological substrate of this neurocognitive phenotype, we identified a disseminated, nonfocal immune cell infiltrate in the CNS of Aβ1–42/CFA-immunized animals. In contrast to MOG35–55/CFA and PBS/CFA controls, the majority of infiltrating cells in Aβ1–42/CFA-immunized mice were CD11b+CD14+ and CD45high, indicating their blood-borne monocyte/macrophage origin. Immunization with Aβ1–42/CFA was significantly more potent than immunization with MOG35–55/CFA or CFA alone in activating macrophages in the secondary lymphoid compartment and peripheral tissues. Studies with TLR2/4-deficient mice revealed that the TLR2/4 pathway mediated the Aβ1–42-dependent proinflammatory cytokine release from cells of the innate immune system. In line with this, TLR2/4 knockout mice were protected from cognitive impairment upon immunization with Aβ1–42/CFA. Thus, this study identifies adjuvant effects of Aβ1–42, which result in a clinically relevant neurocognitive phenotype highlighting potential risks of Aβ immunotherapy.

Suppression of autoimmune encephalomyelitis by a neurokinin-1 receptor antagonist — A putative role for substance P in CNS inflammation

Substance P (SP) is an excitatory neurotransmitter in the central and peripheral nervous system. Most of its physiological functions are mediated through binding to the neurokinin-1 receptor (NK-1R). Recently, proinflammatory properties of SP have been described. In this study we utilized T cell transfer experimental autoimmune encephalomyelitis (EAE) to investigate the role of SP in CNS autoimmune disease. Treatment with the NK-1R antagonist CP-96,345 dramatically reduced clinical and histological signs of EAE if administered before disease onset. The protective effect of CP96,345 treatment was related to a reduced expression of the adhesion molecules ICAM-1 and VCAM-1 on CNS endothelia. The cellular composition or activation status of splenocytes was not affected by CP-96,345 administration, while the secretion of proinflammatory Th1 cytokines was reduced in treated animals. Th2 cytokines remained largely unaffected by NK-1 receptor antagonist treatment. In summary, our findings suggest that the protective effect of CP96,345 treatment is mediated by stabilization of the blood-brain barrier and suppression of Th1 immunity.