The intrinsic pathogenic role of autoantibodies to aquaporin 4 mediating spinal cord disease in a rat passive-transfer model

Neuromyelitis optica (NMO) is causally linked to autoantibodies (ABs) against aquaporin 4 (AQP4). Here, we focused on the pathogenic effects exclusively mediated by human ABs to AQP4 in vivo. We performed cell-free intrathecal (i.th.) passive transfer experiments in Lewis rats using purified patient NMO immunoglobulin G (IgG) and various recombinant human anti-AQP4 IgG-ABs via implanted i.th. catheters. Repetitive application of patient NMO IgG fractions and of recombinant human anti-AQP4 ABs induced signs of spinal cord disease. Magnetic resonance imaging (MRI) revealed longitudinal spinal cord lesions at the site of application of anti-AQP4 IgG. Somatosensory evoked potential amplitudes were reduced in symptomatic animals corroborating the observed functional impairment. Spinal cord histology showed specific IgG deposition in the grey and white matter in the affected areas. We did not find inflammatory cell infiltration nor activation of complement in spinal cord areas of immunoglobulin deposition. Moreover, destructive lesions showing axon or myelin damage and loss of astrocytes and oligodendrocytes were all absent. Immunoreactivity to AQP4 and to the excitatory amino acid transporter 2 (EAAT2) was markedly reduced whereas immunoreactivity to the astrocytic marker glial fibrillary acid protein (GFAP) was preserved. The expression of the NMDA-receptor NR1 subunit was downregulated in areas of IgG deposition possibly induced by sustained glutamatergic overexcitation. Disease signs and histopathology were reversible within weeks after stopping injections. We conclude that in vivo application of ABs directed at AQP 4 can induce a reversible spinal cord disease in recipient rats by inducing distinct histopathological abnormalities. These findings may be the experimental correlate of "penumbra-like" lesions recently reported in NMO patients adjacent to effector-mediated tissue damage.

Efficacy of vitamin D3 as add-on therapy in patients with relapsing-remitting multiple sclerosis receiving subcutaneous interferon β-1a: a Phase II, multicenter, double-blind, randomized, placebo-controlled trial

Recent studies have demonstrated the immunomodulatory properties of vitamin D, and vitamin D deficiency may be a risk factor for the development of MS. The risk of developing MS has, in fact, been associated with rising latitudes, past exposure to sun and serum vitamin D status. Serum 25-hydroxyvitamin D [25(OH)D] levels have also been associated with relapses and disability progression. The identification of risk factors, such as vitamin D deficiency, in MS may provide an opportunity to improve current treatment strategies, through combination therapy with established MS treatments. Accordingly, vitamin D may play a role in MS therapy. Small clinical studies of vitamin D supplementation in patients with MS have reported positive immunomodulatory effects, reduced relapse rates and a reduction in the number of gadolinium-enhancing lesions. However, large randomized clinical trials of vitamin D supplementation in patients with MS are lacking. SOLAR (Supplementation of VigantOL(®) oil versus placebo as Add-on in patients with relapsing-remitting multiple sclerosis receiving Rebif(®) treatment) is a 96-week, three-arm, multicenter, double-blind, randomized, placebo-controlled, Phase II trial (NCT01285401). SOLAR will evaluate the efficacy of vitamin D(3) as add-on therapy to subcutaneous interferon beta-1a in patients with RRMS. Recruitment began in February 2011 and is aimed to take place over 1 calendar year due to the potential influence of seasonal differences in 25(OH)D levels.

Multiple sclerosis: glatiramer acetate induces anti-inflammatory T cells in the cerebrospinal fluid

Glatiramer acetate (GA) is believed to induce GA-reactive T cells that secrete anti-inflammatory cytokines at the site of inflammation in multiple sclerosis (MS). However, GA-reactive T cells have not been established from the intrathecal compartment of MS patients, and intrathecal T cells may differ from T cells in blood. Here, we compared the phenotype of GA-reactive T cells from the cerebrospinal fluid (CSF) and blood of five MS patients treated with GA for 3-36 months, and in three of these patients also before treatment. From the CSF of these patients, all 22 T cell lines generated before and all 38 T cell lines generated during treatment were GA-reactive. GA treatment induced a more pronounced anti-inflammatory profile of GA-reactive T cell lines from CSF than from blood. While GA-reactive T cell clones from CSF were restricted by either human leukocyte antigen (HLA) -DR or HLA-DP, only HLA-DR restricted GA-reactive T cell clones were detected in blood. No cross reactivity with myelin proteins was detected in GA-reactive T cell lines or clones from CSF. These results suggest that a selected subset of GA-reactive T cells are present in the intrathecal compartment, and support an anti-inflammatory mechanism of action for GA.

T cells from multiple sclerosis patients recognize multiple epitopes on Self-IgG

The highly diversified variable regions of immunoglobulin (Ig) molecules contain immunogenic determinants denoted idiotopes. We have previously reported that T cells from multiple sclerosis (MS) patients recognize IgG from autologous cerebrospinal fluid (CSF), and mapped a T-cell epitope to an IgG idiotope. To test the ability of CSF IgG molecules to elicit a broad polyclonal T-cell response in MS, we have analysed T-cell responses in the blood and CSF against idiotope peptides spanning complementarity determining region (CDR) 3 and somatic mutations within the variable regions of monoclonal CSF IgG. Consistent with a diversified idiotope-specific T-cell repertoire, CD4(+) T cells from both patients recognized several idiotope peptides presented by HLA-DR molecules. Mutations were critical for T-cell recognition, as T cells specific for a mutated CDR1 peptide did not recognize corresponding germline-encoded peptides. One T-cell clone recognized both an idiotope peptide and the B-cell clone expressing this idiotope, compatible with endogenous processing and presentation of this idiotope by B cells. These results suggest that mutated CSF IgG from MS patients carry several T-cell epitopes, which could mediate intrathecal IgG production and inflammation in MS through idiotope-driven T-B-cell collaboration.