Neutralizing antibodies, MxA expression and MMP‐9/TIMP‐1 ratio as markers of bioavailability of interferon‐beta treatment in multiple sclerosis patients: a two‐year follow‐up study

Abstract

The objective of this study was to correlate the detection of neutralizing antibodies (NAbs) by the cytopathic effect (CPE) assay, with the expression of myxovirus resistance protein A (MxA), and the ratio between matrix metalloproteinase 9 (MMP-9) and its tissular inhibitor (TIMP-1), in order to evaluate their usefulness as markers of interferon beta (IFN-beta) bioavailability. Pairs of blood and serum samples were collected from 50 patients with multiple sclerosis (MS) during 2 years of IFN-beta treatment. Expression of MxA, MMP-9 and TIMP-1 were analysed by quantitative PCR, and NAbs were measured by CPE assay. During the study, 60% of patients presented NAbs. The number of serum samples that were NAbs+ was significantly increased amongst patients with relapses (41/92 vs. 33/108, P = 0.04). With one serum sample and with a NAb titre >100 tenfold reduction unit (TRU), 66.7% of patients with MS suffered from relapses, 41.7% suffered from progression, and 75% was not an optimal clinical responder. We did not find any significant difference in MxA. We found that 62.5% of patients with MS patients whose ratio was increased twofold after 2 years suffered from relapses, 37.5% suffered from progression, and 68.7% was not an optimal clinical responder. The early detection of NAbs by CPE assay and the finding of only one serum sample with a NAb titre >100 TRU seem to be markers of low bioavailability of IFN-beta, whilst a twofold decrease in the MMP-9/TIMP-1 ratio by quantitative PCR assay seems to be a marker of high bioavailability of IFN-beta.