An assay to quantify species-specific anti-JC virus antibody levels in MS patients

The StratifyJCV® test is a qualitative assay to classify MS patients as anti-JC virus (JCV) antibody positive or negative. Quantification of anti-JCV antibody levels in serum and cerebrospinal fluid (CSF) of multiple sclerosis (MS) patients might add to the progressive multifocal leukoencephalopathy (PML) risk assessment.

The objective of this study is to test sera of patients in a quantitative anti-JCV antibody assay, and to compare the results with preexisting data from the StratifyJCV® test.

Sera of a total of 175 MS patients and matched non-MS-controls were tested for anti-JCV antibodies using glutathione S-transferase-tagged-VP1 as antigen. Antibody reactivity was quantified in arbitrary units using human immunoglobulin as standard.

The comparison of our assay with StratifyJCV® showed good inter-assay agreement (kappa 0.6), and strong correlation for antibody reactivity (r (2) = 0.94). Discordant samples had low-reactive positivity, and a higher proportion (13% vs. 4%) tested positive in the StratifyJCV® test only.

The method presented is a tool for the reliable quantification of anti-JCV antibodies, which demonstrates good agreement with results from StratifyJCV®. In contrast to StratifyJCV®, we pre-adsorbed all of the sera with BK virus (BKV) VP1 protein to reduce cross-reactivity. This step may account for a higher species-specificity of our assay. As such, our assay might be a promising additional tool for PML risk assessment.