BACKGROUND: The anti-JC virus (JCV) antibody status has been introduced to stratify MSers for higher or lower risk of progressive multifocal leukoencephalopathy (PML).
OBJECTIVE: To assess the potential utility of anti-JCV antibody levels for earlier diagnosis or prediction of PML.
METHODS: An analytically validated antibody assay was used to determine serological status, normalised optical density values, and dilution titres for anti-JCV antibodies. The method was applied to stored sera of 1157 MSers including five cases of PML, all enrolled in the Swedish pharmacovigilance study for natalizumab (NAT). Anti-cytomegalovirus (CMV) and anti-varicella-zoster (VZV) antibody levels served as controls.
RESULTS: Prior to treatment with NAT, anti-JCV antibody levels were stable in the anti-JCV positive MSers. During therapy, a slight decrease in anti-JCV and anti-VZV antibody levels, but not anti-CMV antibody levels, was observed. All five MSers who developed PML showed a mild to moderate increase in anti-JCV antibody levels at time of PML diagnosis; pre-PML samples suggested that this increase might start already prior to diagnosis of PML.
CONCLUSIONS: Treatment initiation with NAT may lead to a slight decrease in anti-JCV and anti-VZV antibody levels, suggestive of a mild suppressive effect of NAT on antibody levels. Our findings in five cases of PML demonstrate that the onset of PML can be accompanied by increasing anti-JCV antibodies in serum. Monitoring of anti-JCV antibody levels could potentially be used as a tool for prediction or earlier diagnosis of PML during NAT treatment for MS.
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| JCV particles |
This will need replication and you would need serial JCV tests for this to be of use. News on the block is that Biogen have data to confirm this observation; watch this space.