BACKGROUND: Neutralizing antibodies (NAb) to interferon-beta (IFN-β) are associated with reduced bioactivity and efficacy of IFN-β in multiple sclerosis (MS). The myxovirus resistance protein A (MxA) gene expression is one of the most appropriate markers of biological activity of exogenous IFN-β. We hypothesized that therapeutic plasma exchange (TPE) can restore the ability of IFN-β to induce the MxA mRNA expression and that maintenance plasmapheresis can sustain the bioavailability of IFN-β.

MATERIAL AND METHODS: Eligible patients underwent 4 primary separate plasma exchange sessions. After the induction TPE sessions, they were transferred to maintenance plasmapheresis. Bioactivity of IFN-β was expressed as in vivo MxA mRNA induction in whole blood using RT-qPCR.

RESULTS: Six patients with low IFN-β bioavailability detected by the MxA mRNA response were included. Four patients became biological responders after induction plasmapheresis. In 2 patients an increase of MxA mRNA expression was found, but the values persisted below the cut-off and the patients remained as “poor biological responders”. The effect of maintenance plasmapheresis was transient: MxA mRNA expression values reverted to the baseline levels after 1–2 months.

CONCLUSIONS: Therapeutic plasma exchange is able to restore the bioavailability of IFN-β in the majority of studied patients, but the effect of TPE on the IFN-β bioavailability was transient.

Keywords: Antibodies, Neutralizing - immunology, Biological Availability, Biomarkers - metabolism, Interferon-beta - pharmacokinetics, Multiple Sclerosis - therapy, Myxovirus Resistance Proteins - metabolism, Pilot Projects, Plasma Exchange - methods, Plasmapheresis - methods, Reverse Transcriptase Polymerase Chain Reaction