Understanding the mechanisms underlying the unfortunate occurrence of progressive multifocal leukoencephalopathy (PML), a disease caused by reactivation of the JC polyomavirus, in a small subset of patients during treatment of autoimmune disease with natalizumab is important at several levels. The most important and immediate outcome would be a more complete appreciation of the risk of PML, not only with natalizumab therapy but also with other immunomodulatory therapeutic strategies currently in development. The second most important outcome would be the potential for the development of approaches for monitoring patients treated with natalizumab and other therapies that may have similar risks, in turn allowing for the safer use of these treatments. Finally, an understanding of the mechanism(s) contributing to the association of PML with natalizumab therapy may provide new insights into the disease processes in multiple sclerosis and PML.
McFarland HF, Jacobson S. Natalizumab and Immune Cells. Arch Neurol. 2006;63(10):1366-1367. doi:10.1001/archneur.63.10.1366