PML is a rare condition that causes damage to white matter in the brain. The cause of PML is John Cunningham virus, which is generally kept under control by the immune system. In individuals with a weakened immune system, John Cunningham virus can cause problems and complications. The researchers found that multiple sclerosis patients taking natalizumab are at a higher risk of developing complications associated with JCV.
Senior author Heinz Wiendl said, “An increase in the levels of anti-JCV antibodies could signify an increased risk of PML.”
The researchers looked at blood tests to monitor anti-JCV antibodies in 525 people in Germany over the course of 15 months and in 711 people in France over the course of two years. All participants had multiple sclerosis and were taking natalizumab.
The annual rate of conversion from being anti-JCV negative to being anti-JCV positive was 10 percent for the Germans and nine percent for the French. Both results are much higher than the annual one percent rate among the general population and multiple sclerosis patients who are not taking the medication in question.
Adil Javed of the University of Chicago in Illinois wrote in an accompanying editorial, “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.”
Wiendle 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.”
John Cunningham virus and risks for MS patients
John Cunningham virus is quite common in the U.S., with 70 to 90 percent of the population living with JCV. Majority of JCV carriers will never know they have the virus and will not experience any associated symptoms or side effects. Patients with multiple sclerosis are at a higher risk of developing complications related to JCV, either due to multiple sclerosis itself or because their immune system is weakened by medications.
JCV can be carried into the brain where it can cause an infection – PML. When the white matter gets infected by the virus, it attacks the myelin-making cells, thus stripping the nerve cells off their protective coating and exposing them to harm as a result.
JCV often causes complications in individuals with weakened immune systems, making multiple sclerosis patients the perfect target. Not only do multiple sclerosis patients often take immunosuppressants, but their immune system is often compromised regardless, simply due to multiple sclerosis itself.
There is an FDA-approved test that can check for JCV. If you have multiple sclerosis, especially if you are on certain medications that may compromise your immune system, you can undergo a routine testing for JCV to determine your risk of PML.
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Sources:
https://www.aan.com/PressRoom/home/PressRelease/1429
http://www.healthline.com/health/multiple-sclerosis/jc-virus-risks-for-ms-patients#1