Background: Progressive multifocal leukoencephalopathy (PML), a potentially fatal demyelinating disease caused by the John Cunningham virus (JCV), can occur as a complication of treatment with rituximab, fingolimod, and dimethyl fumarate. The primary objective of this study was to determine changes in anti-JCV antibody index values in multiple sclerosis (MS) patients treated with these three medications. Second, we explored the relationship between absolute lymphocyte count (ALC), anti-JCV antibody index values, and various patient characteristics.
Methods: In this retrospective chart review, we evaluated changes in JCV serology and ALC in 172 MS patients treated with fingolimod, rituximab, or dimethyl fumarate (2013-2016). Only those with known anti-JCV antibody and ALC values before starting the study medications were included. Subsequent values were obtained on an ad hoc basis throughout the study.
Results: There was a significant decrease in anti-JCV antibody index values in patients treated with fingolimod and rituximab (P = 0.03 and P = 0.014, respectively). A non-significant decreasing trend in anti-JCV antibody index values occurred in patients treated with dimethyl fumarate. Notably, there was no relationship between ALC and anti-JCV antibody index values for patients treated with rituximab, fingolimod, or dimethyl fumarate.
Conclusions: Anti-JCV antibody index values significantly decreased in MS patients treated with fingolimod and rituximab; however, this did not occur with dimethyl fumarate. Fingolimod and rituximab may impair the humoral response to the JCV. Nevertheless, a declining anti-JCV antibody index in MS patients treated with fingolimod or rituximab should not necessarily be interpreted as correlating with a decreased risk for PML.
Keywords: Anti-John Cunningham virus antibody index value; John Cunningham virus; dimethyl fumarate; fingolimod; lymphocyte count; multiple sclerosis; progressive multifocal leukoencephalopathy; rituximab.