Multiple sclerosis (MS) patients treated with natalizumab have an increased risk of developing high levels of antibodies associated with a virus causing a rare, but often fatal, brain infection known as progressive multifocal leukoencephalopathy (PML), researchers reported.
Their study, “Therapy with natalizumab is associated with high JCV seroconversion and rising JCV index values,” was recently published in the online issue of Neurology, Neuroimmunology and Neuroinflammation, a medical journal of the American Academy of Neurology (AAN).
A common virus causes PML, the John Cunningham virus (JCV). JCV is usually kept under control by the immune system, although people with a weakened immune system or undergoing immunosuppressive treatments are at risk of developing related diseases, such as PML.
Researchers analyzed the levels of anti-JCV antibodies in blood samples from MS patients taking natalizumab (commercialized as TYSABRI) over a long period of time: more than 15 months in 525 German patients and over two years and 711 French patients.
The team discovered that a fraction of patients in both groups, who were initially anti-JCV negative, became positive during the course of the study — specifically, 43 out of 339 German and 41 out of 243 French patients. Moreover, researchers also observed an increase in anti-JCV positive antibodies within patients who were already positive at the study’s beginning. In total, treatment with natalizumab was associated with a 13 percent increase, annually, in anti-JCV antibodies in the blood of MS-treated patients.
Dr. Adil Javed, from the University of Chicago in Illinois, a member of the AAN and the author of an editorial about the study, said in a press release, “Even though anti-JCV antibodies were present at a higher level, it does not necessarily mean that an individual will get PML. The risk of PML in JCV positive people being treated for multiple sclerosis with natalizumab without prior immunosuppressant therapy is one in 1,000 people. The risk of a multiple sclerosis attack in untreated patients is one in every two people.”
Dr. Heinz Wiendl, from the University of Münster in Germany, a member of the AAN and the study’s lead author, added, “It is important that people with multiple sclerosis taking natalizumab speak with their doctor before making any changes to their treatment. Still, this study shows anti-JCV antibodies may serve as a useful biomarker. Natalizumab did appear to increase the levels of anti-JCV antibodies and this higher level may be associated with a higher risk of PML. The results of this study underscore the need for frequent monitoring of anti-JCV antibodies in people who are being treated with natalizumab for multiple sclerosis.”