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    MS Drug Tied to Higher Risk for Brain Virus

    Patients taking Tysabri were more prone to show signs of exposure to JCV, which can cause a brain disease

    WebMD News from HealthDay

    By Mary Elizabeth Dallas

    HealthDay Reporter

    WEDNESDAY, Jan. 27, 2016 (HealthDay News) -- People with multiple sclerosis who are treated with the drug Tysabri (natalizumab) may have up to a 10 times greater risk for a rare and potentially deadly viral infection, a new study finds.

    The germ in question is the John Cunningham virus (JCV), a pathogen thought to cause a deadly brain condition known as progressive multifocal leukoencephalopathy (PML).

    The link between Tysabri and PML isn't new: Numerous studies published over the past few years have shown an increase in risk for the disease in patients taking the drug.

    However, even though the new study showed a link between Tysabri and JCV infection, experts stressed that the drug can be of great help to patients, who should weigh its benefits against its risks.

    The new research was led by Dr. Heinz Wiendl of the University of Muenster in Germany. The findings are published in the Jan. 27 online edition of the journal Neurology: Neuroimmunology & Neuroinflammation.

    The study authors explained that the virus is usually kept in check by the human immune system. However, people taking drugs that compromise the immune system, such as Tysabri, appear to be more vulnerable to JCV. The researchers believe that Tysabri may prevent immune cells from reaching the brain and fighting the virus.

    The new study involved 525 German and 711 French multiple sclerosis patients. All were taking Tysabri. The German patients had their blood levels of JCV antibodies monitored for 15 months, while the French patients were monitored for more than two years.

    Those taking Tysabri had higher blood levels of JCV antibodies -- an indicator of exposure to the virus, the study found. As a result, the researchers concluded these patients were at greater risk for PML.

    The patients from Germany transitioned from being negative for JCV antibodies to positive at an annual rate of about one in every 10 patients (10 percent). The patients in France made this transition at an annual rate of 9 percent, the findings showed.

    The researchers said that these rates are significantly higher than the annual rate of 1 percent among the general population and those with MS who are not treated with Tysabri.

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