Muenster, Germany—Progressive multifocal leukoencephalopathy (PML), an often fatal disease caused by the John Cunningham virus (JCV) and damaging the white matter of the brain, is generally rare. Patients with weakened immune systems, or on immunosuppressive drugs, are considered to be more susceptible to JCV-related problems, however. Now, a new German study, published online recently by the journal Neurology: Neuroimmunology and Neuroinflammation, suggests that multiple sclerosis patients taking the drug natalizumab appear to have a a 10 times greater risk of developing a risk biomarker for activity of the JCV virus. University of Muenster–led researchers used a blood test to monitor levels of anti-JCV antibodies to determine that, in MS patients using natalizumab, conversion from being anti-JCV negative to anti-JCV positive occurred at a 10% rate in German study participants and nearly 9% in a French group, compared to about 1% in the general population and in MS patients not on that therapy.
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