If you have MS and have been through the process of finding the right Disease Modifying Drug, chances are you’ve picked up some fancy new vocabulary words along the way. You probably whip out words like lesion, atrophy, relapse, and ataxia in daily conversation. And if you have considered taking, or are already taking Tysabri, chances are you encounter the acronyms JCV and PML often. This is a very confusing topic for most, and I hope to demystify some of it for you here today!
JCV stands for John Cunningham Virus because, obviously, as medical professionals naming something after yourself means you have arrived in the world! The JC virus is very similar to other well known viruses like the Chicken Pox. It is a common virus which is passed from person to person. In someone with a normal immune system the JC virus usually does not cause any symptoms, and sits dormant (inactive) because your immune system keeps it from attacking your body. Chicken Pox is very similar, generally you have one outbreak as a child and afterwards the virus sits inactive in your body, and when you are older the virus may flare up again as the Shingles.
Now enter Tysabri…
Tysabri works by weakening your immune system. Since MS is an autoimmune disease in which your immune system attacks your own body, weakening the immune system can slow or stop the progression of MS. The drawback is that Tysabri weakens your entire immune system, not just the part responsible for MS, and your body can no longer fight off viruses as effectively. So now your immune system that was defending you and keeping the JC virus dormant is vulnerable, and the virus can become activated.
When the JC virus becomes active there is a chance that it could cross the Blood Brain Barrier and go into the brain causing an infection called PML, or progressive multifocal leukoencephalopathy. PML targets the cells in your brain that make myelin and can result in major illness, and even death. Scary stuff to say the least!
So here’s the good news: we can easily test to see if you carry the JC virus. The Stratify JCV Antibody ELISA blood test (we just love sounding fancy, don’t we?) will tell your neurologist if you have been exposed to the JC virus, and what your risk of developing PML is. If you test negative, meaning you do not carry the JC virus, we will keep testing you every 6 months because you can be exposed to the virus at any time.
If you do test positive for the JC virus we also get an index value which gives us even more information about how likely you are to get PML. A low index value means a low chance of PML, and a higher number is associated with an greater risk. PML is not a common side effect with an incidence rate of less than 1 in 1,000 (see the tables below). However, even though PML is not very common it is very serious, so we as providers aren’t willing to let you let be that 1 in 1,000! During the first year of being treated with Tysabri your risk for PML is very low, and after two or more years the risk increases. Therefore the length of time you have been on Tysabri, testing positive for the JC virus, and a high index value are all factors in deciding the best course of action.
So what are the symptoms of PML, and how do we diagnose and treat it?
Since PML attacks the myelin, much like MS does, the symptoms include confusion, difficulty speaking, loss of balance and coordination, vision problems, weakness, and memory loss. Sound like your everyday life? You would want to alert your healthcare provider if you experience any new or worsening symptoms. If PML is suspected an MRI of the brain will be ordered and your doctor may want to do a lumbar puncture to see if the JC virus is in your spinal fluid. Treatment includes admission to the hospital and plasma exchange, which is a process similar to dialysis in which we try to remove the virus from your body.
As with every topic I recommend reading up on it, becoming well informed, and speaking with your doctor about any concerns you have.
Any other questions, comments, or concerns??
If you want to get your nerd on check out these sources: