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Longitudinal evaluation of reactivity against a new immunological target in neuromyelitis optica

Background: Neuromyelitis optica is an autoimmune disease usually restricted to spinal cord and optic nerves. Recently, an immunological marker (NMO-IgG) directed against the aquaporin-4 (AQP4) has been found in this disease. Although it usefulness in NMO diagnosis was established, its correlation with disease activity and its interest for NMO follow up was not demonstrated yet. The results of a previous study have suggested that reactivity against new immunological targets can be found in NMO. A reactivity against glucosylated CSF114, a synthetic peptide derivated from myelin oligodendrocyte glycopeptide, was especially observed in 38.5% of NMO patients. Objective: To look for a correlation of anti-CSF reactivity with disease activity in NMO through a longitudinal evaluation. Patients and Methods: Sera from 12 NMO patients (either positive or negative for NMO-IgG) were collected at 3 or 4 different points of the disease from 2006 to 2009. The severity of the disease was evaluated using the expanded disease disability scale (EDSS) score at the moment of each blood sampling. The presence of a clinical relapse during the previous month was also noted. The level of anti-CSF IgG was measured using enzyme-linked immunosorbent assays and compared with the disease severity. We also looked for an association between the presence of a relapse and higher anti-CSF reactivity. Results: We collected 38 sera (11 sera during a relapsing phase and 27 during a remitting phase). Mean EDSS score of the 12 patients was 3+/-2.4. Mean optical density of the 38 sera was 0.53+/-0.5. We found a significant increase in anti-CSF IgG levels in the sera collected during the relapses of NMO (0.87+/-0.56 versus 0.39+/-0.42). A less significant correlation was also observed between EDSS score and anti-CSF reactivity. No correlation with the NMO-IgG status was noted. Conclusions: These results suggest that anti-CSF reactivity in NMO sera is correlated with the activity of the disease. The increased response against glucosylated targets in NMO could result from disturbances of glucose metabolism in the lesions. Prospective studies are warranted to evaluate the interest of anti-CSF IgG assessment in NMO follow up.

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