title: Therapy with natalizumab is associated with high JCV seroconversion and rising JCV index values.
abstract: OBJECTIVE
  The aim of the study was to analyze John Cunningham virus (JCV) serology in natalizumab-treated patients over time and assess whether they are influenced by natalizumab treatment.
  
  
  METHODS
  German (n = 1,921; 525 longitudinally) and French (n = 1,259; 711 longitudinally) patients were assessed for JCV serology alongside their therapy with natalizumab.
  
  
  RESULTS
  JCV serostatus changed in 69 of 525 longitudinally followed German patients (13.1%) over 14.8 months. Seroconversion according to serostatus was seen in 43 of 339 initially JCV- German patients (12.7% in 14.8 months; 10.3% per year) and 41 of 243 initially JCV- French patients (16.9% in 24 months; 8.5% per year). JCV index values could be reproduced (R (2) = 0.89) with the caveat of 8 of 50 samples (16%) being set into different risk categories between 2 assessments. Index values of JCV+ patients rose over time (p = 0.009) but not because of aging. Treatment with natalizumab was associated with a 15.9% increase of value in JCV+ patients in 14.8 months (12.9% per year).
  
  
  CONCLUSIONS
  JCV seroconversion and index values may be influenced by treatment with natalizumab. It is therefore important to monitor patients' JCV serology but also to incorporate additional risk factors into the progressive multifocal leukoencephalopathy risk stratification.
authors: Department of Neurology (N.S., T.S.-H., J.B., C.C.G., K.G., H.W.), University of Münster, Germany; and Pole des Neurosciences Centre Hospitalier Universitaire Toulouse (B.P., D.B.), CPTP INSERM UMR 1043 et Université de Toulouse, UPS, Toulouse, France. D.B. also represents the BioNAT Study Group.
authors: Nicholas
authors: N
authors: Schwab
authors: Department of Neurology (N.S., T.S.-H., J.B., C.C.G., K.G., H.W.), University of Münster, Germany; and Pole des Neurosciences Centre Hospitalier Universitaire Toulouse (B.P., D.B.), CPTP INSERM UMR 1043 et Université de Toulouse, UPS, Toulouse, France. D.B. also represents the BioNAT Study Group.
authors: Tilman
authors: T
authors: Schneider-Hohendorf
authors: Department of Neurology (N.S., T.S.-H., J.B., C.C.G., K.G., H.W.), University of Münster, Germany; and Pole des Neurosciences Centre Hospitalier Universitaire Toulouse (B.P., D.B.), CPTP INSERM UMR 1043 et Université de Toulouse, UPS, Toulouse, France. D.B. also represents the BioNAT Study Group.
authors: Béatrice
authors: B
authors: Pignolet
authors: Department of Neurology (N.S., T.S.-H., J.B., C.C.G., K.G., H.W.), University of Münster, Germany; and Pole des Neurosciences Centre Hospitalier Universitaire Toulouse (B.P., D.B.), CPTP INSERM UMR 1043 et Université de Toulouse, UPS, Toulouse, France. D.B. also represents the BioNAT Study Group.
authors: Johanna
authors: J
authors: Breuer
authors: Department of Neurology (N.S., T.S.-H., J.B., C.C.G., K.G., H.W.), University of Münster, Germany; and Pole des Neurosciences Centre Hospitalier Universitaire Toulouse (B.P., D.B.), CPTP INSERM UMR 1043 et Université de Toulouse, UPS, Toulouse, France. D.B. also represents the BioNAT Study Group.
authors: Catharina C
authors: CC
authors: Gross
authors: Department of Neurology (N.S., T.S.-H., J.B., C.C.G., K.G., H.W.), University of Münster, Germany; and Pole des Neurosciences Centre Hospitalier Universitaire Toulouse (B.P., D.B.), CPTP INSERM UMR 1043 et Université de Toulouse, UPS, Toulouse, France. D.B. also represents the BioNAT Study Group.
authors: Kerstin
authors: K
authors: Göbel
authors: Department of Neurology (N.S., T.S.-H., J.B., C.C.G., K.G., H.W.), University of Münster, Germany; and Pole des Neurosciences Centre Hospitalier Universitaire Toulouse (B.P., D.B.), CPTP INSERM UMR 1043 et Université de Toulouse, UPS, Toulouse, France. D.B. also represents the BioNAT Study Group.
authors: David
authors: D
authors: Brassat
authors: Department of Neurology (N.S., T.S.-H., J.B., C.C.G., K.G., H.W.), University of Münster, Germany; and Pole des Neurosciences Centre Hospitalier Universitaire Toulouse (B.P., D.B.), CPTP INSERM UMR 1043 et Université de Toulouse, UPS, Toulouse, France. D.B. also represents the BioNAT Study Group.
authors: Heinz
authors: H
authors: Wiendl