“…IFN-beta is a cytokine naturally expressed in response to viral infections [22], however, its mechanism of action in MS is not completely understood, but it has been speculated that, besides its immunomodulatory properties, the efficacy of IFN-beta may be related to its antiviral properties [23]. However, it has been observed consistently that a proportion of patients (2% to 47%) develop NAbs directed against IFN beta as a consequence of the treatment [24], [25]. In our study, the 32.8% of MS patients was positive for NAbs; as NAbs are associated with a loss of efficacy of IFN-beta treatment and a reduced bioavailability, they appeared at any time of the four scheduled visits and while some NAbs positive patients remained positive along the IFN-beta treatment, others patients became negative, we decided to evaluate the variation of the anti-HHV-6A/B IgG titers only in an homogenous cohort of MS patients without NAbs.…”