Importance: Infection with JC virus (JCV) may lead to development of demyelinating progressive multifocal leukoencephalopathy in patients with multiple sclerosis (MS) who are treated with natalizumab.
Objective: To determine whether mononuclear cells in circulation from MS patients treated with natalizumab harbor JCV DNA.
Design, setting, and participants: In this prospective investigation, we enrolled 49 MS patients from the Clinical Center for Multiple Sclerosis at The University of Texas Southwestern Medical Center and 18 healthy volunteers. We drew 120-mL blood samples from 26 MS patients at baseline and at approximately 3-month intervals to 10 months during the course of natalizumab infusions. One blood sample was drawn from 23 MS patients receiving natalizumab for more than 24 months and from 18 healthy volunteers.
Interventions: Natalizumab treatment of MS.
Main outcomes and measures: The blood samples were separated using flow cytometry into CD34+, CD19+, and CD3+ cell subsets; DNA templates were prepared using quantitative polymerase chain reaction for JCV DNA identification. Plasma samples were tested for anti-JCV antibodies by enzyme-linked immunosorbent assays performed at the Laboratory of Molecular Medicine and Neuroscience, National Institute of Neurological and Communicative Diseases and Stroke.
Results: Thirteen of the 26 patients (50%) with baseline and follow-up blood samples had detectable viral DNA in at least 1 cell compartment at 1 or more points. Ten of the 23 patients (44%) receiving treatment for more than 24 months and 3 of the 18 healthy volunteers (17%) also had detectable viral DNA in 1 or more cell compartment. Fifteen of the 49 MS patients (31%) were confirmed to harbor JCV in CD34+ cells and 12 of 49 (24%) in CD19+ cells. Only 1 of 18 healthy volunteers were viremic in CD34+ cells and none in CD19+ cells. Nine patients and 1 healthy volunteer were viremic but had seronegative test results for JCV antibodies.
Conclusions and relevance: JC virus DNA was detectable within cell compartments of natalizumab-treated MS patients after treatment inception and longer. JC virus DNA may harbor in CD34+ cells in bone marrow that mobilize into the peripheral circulation at high concentrations. Latently infected cells initiate differentiation to CD19+ cells that favors growth of JCV. These data link the mechanism of natalizumab treatment with progressive multifocal leukoencephalopathy.