Therapeutic Plasma Exchange in Multiple Sclerosis Patients with Abolished Interferon-beta Bioavailability

Background: Neutralizing antibodies (NAb) to interferon-beta (IFN-beta) are associated with reduced bioactivity and efficacy of IFN-beta 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-beta. We hypothesized that therapeutic plasma exchange (TPE) can restore the ability of IFN-beta to induce the MxA mRNA expression and that maintenance plasmapheresis can sustain the bioavailability of IFN-beta. Material/Methods: Eligible patients underwent 4 primary separate plasma exchange sessions. After the induction TPE sessions, they were transferred to maintenance plasmapheresis. Bioactivity of IFN-beta was expressed as in vivo MxA mRNA induction in whole blood using RT-qPCR. Results: Six patients with low IFN-beta 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-beta in the majority of studied patients, but the effect of TPE on the IFN-beta bioavailability was transient.