Background: The risk of progressive multifocal leukoencephalopathy (PML) caused by the JC virus (JCV) is increased in patients with multiple sclerosis receiving biological therapies.
Objectives: To determine the seroprevalence of anti-JCV antibodies in Finnish patients with multiple sclerosis (MS) and clinically isolated syndrome and to assess the clinical risk factors for JCV seropositivity.
Methods: The JCV seroprevalence was analyzed in 503 patients using a second-generation two-step ELISA. Sixty-seven patients underwent longitudinal serological evaluation over 4.5 years.
Results: The overall seroprevalence of JCV was 57.4%. The seropositivity was higher in men than in women, tended to increase with age, and was not affected by different immunomodulatory therapies. However, in patients with ongoing natalizumab treatment (n = 72), the anti-JCV antibody screening index was lower than in patients without such therapy [median 0.3 (range 0.1-3.1) vs 0.6 (0.1-3.1), respectively, P = 0.01]. Over 4.5 years, 4/19 (21%) initially seronegative patients converted to seropositivity, whereas 4/48 (8.3%) initially seropositive patients reverted to seronegativity. Fluctuations in serostatus were observed in 3/67 patients.
Conclusion: The study confirmed a high anti-JCV antibody prevalence in patients with MS and its association with age and male gender but not with disease-modifying therapies. Our data suggest that therapy with natalizumab may cause a decrease in anti-JCV antibody levels, suggesting an immunosuppressive effect of natalizumab without an impact on JCV seroprevalence. The results of studies performed until now confirm the predictive value of anti-JCV antibody measurement in the assessment of PML risk; however, changes in serostatus need to be considered.
Keywords: JC virus; anti-JCV antibodies; multiple sclerosis; screening index.
© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.