Is it safe to have Natalizumab (Tysabri) or Ocrelizumab (Ocrevus) while you are tested JC Virus positive?

I had to under go the JC virus antibody test for CSF and Serum and found that i am JC virus positive. While my neurologist are evaluating my risk for undergoing the next level of treatment with Natalizumab (Tysabri) or Ocrelizumab (Ocrevus), i wanted to understand from other MS patients who are on these treatments.

I have heard a lot and seen video testimonials of patients going through Tysabri infusions and saying that they feel better. Also few of them are JC virus positive who are at risk of getting the PML (Progressive multifocal leukoencephalopathy) a rare disorder and fatal disease that affects the brain.

My understanding of breaking this medical acronym of PML is:

Progressive - Self understanding as Progressive

Multifocal - Lesions at multiple places in brain

Leuko - White matter of the brain

Encephalopathy - Disorder

When we visit these companies official websites the main page pops up with patient risk assessment. The information clearly mentions that MS patients who are undergoing treatment on Tysabri must be closely monitored for PML disease very often.

Let us understand how do we evaluate a patient before prescribing Tysabri:

1) He or she must undergo for JC Virus test (More information on this below). Few test to confirm are: JC Virus antibody, JC virus serum, IgG index values.

2) If you are JC virus positive, then the chances of getting PML disease is 1:1000 patients (Not sure from where this data is captured or mentioned in company website. Are they updating this regularly)

3) If you are JC virus negative, then the chances of getting PML disease is 1:10000 patients (But you cannot be happy that you are tested negative, you can get this virus anytime). So again you need to get tested every 6 months.

4) You cannot take Tysabri for life long like interferons (e.g Avonex). The company Biogen says it can be taken for 2 years safely, then every 6 months you must test JC virus activity in your body. Depending on the pros and cons the neurologist will decide whether to continue Tysabri or move on to some other disease modifying therapies.

More information about JC Virus:

JC Virus is present in most of the human population (approximately 90%). While this virus is harmless among people having good immunity (Majority of the population, except few MS patients) it is harmful among people having suppressed immunity. 

MS patients immunity is compromised since we have to undergo disease modifying therapies such as interferons and immuno suppressants. While you are on these therapies (Further adding Tysabri) your immunity is less and those people who are JC Virus positive tend to get PML since JC virus is main cause of it. JC Virus enters the blood brain barrier and affects the white matter.

It will be interesting to know from others real time experience and their confidence on taking Tysabri who are currently tested positive for JC Virus.