Search for specific biomarkers of IFN-beta bioactivity in patients with MS

We aimed to identify specific biomarkers of IFN-beta bioactivity in order to compare their gene expression induction by type I IFNs with the MxA, and to investigate their potential role in MS pathogenesis. Gene expression microarrays were performed in PBMC from MS patients who developed neutralizing antibodies (NAB) to IFN-beta. Nine genes followed patterns in gene expression over time similar to the MX1 and were selected for further experiments: IFI6, IFI27, IFI44L, IFIT1, HERC5, LY6E, RSAD2, SIGLEC1, and USP18. In vitro experiments revealed specific induction of selected biomarkers by IFN-beta but not IFN-gamma, and several markers, in particular USP18 and HERC5, were significantly induced at lower IFN-beta concentrations and more selective than the MX1 as biomarkers of IFN-beta bioactivity. In addition, USP18 expression was deficient in MS patients compared with healthy controls (p=0.0004). We propose specific biomarkers that may be considered in addition to the MxA to evaluate IFN-beta bioactivity, and to further explore their implication in MS pathogenesis. Number of samples: 32. We analyzed PBMC from 8 patients at baseline and after 3, 12 and 24 months of IFN-beta treatment