HealthDay News — Treatment with natalizumab (Tysabri) affects seroconversion and JC virus (JCV) index values in multiple sclerosis patients with JCV,  according to a study published in Neurology: Neuroimmunology & Neuroinflammation.

Nicholas Schwab, PhD, from the University of Münster in Germany, and colleagues analyzed JCV serology in natalizumab-treated patients over time. Data were included for 1,921 German patients and 1,259 French patients.

The researchers found that over 14.8 months, JCV serostatus changed in 69 of 525 longitudinally followed German patients (13.1%). Per year, 10.3% of 399 initially JCV− German patients and 8.5% of initially JCV− French patients had seroconversion according to serostatus. JCV index values could be reproduced (R² = 0.89) with 16% of samples being set into different risk categories between 2 assessments. There was an increase in the index values of JCV+ patients over time (P = 0.009), which was not attributed to aging. In 14.8 months, natalizumab treatment correlated with a 15.9% increase of value in JCV+ patients (12.9% per year).

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“JCV seroconversion and index values may be influenced by treatment with natalizumab,” the authors write. “It is therefore important to monitor patients’ JCV serology but also to incorporate additional risk factors into the progressive multifocal leukoencephalopathy risk stratification.”

Several authors disclosed financial ties to the biopharmaceutical industry.


Schwab N, Schneider-Hohendorf T, Pignolet B, et al. Therapy with natalizumab is associated with high JCV seroconversion and rising JCV index values. Neurol Neuroimmunol Neuroinflamm. 2016; doi:​10.​1212/​NXI.​0000000000000195.