Soluble BAFF Level Is Not Correlated to Mycobacterium avium Subspecies Paratuberculosis Antibodies and Increases After Interferon-β Therapy in Multiple Sclerosis Patients

B cells are being recognized as one of the major players in the pathogenesis of multiple sclerosis (MS). The B cell activating factor (BAFF) system plays an essential role in B cell homeostasis and function in the periphery. Mycobacterium avium subspecies paratuberculosis (MAP) has been previously associated to MS in Sardinia. Antibodies against a MAP surface protein, MAP_2694, have been found significantly associated to MS patients, and this response was modified by interferon-β therapy. Increased BAFF levels following IFN-β therapy have been also described in MS patients. In this study, we evaluated whether soluble BAFF levels are comparable in men and women affected by MS and performed a correlation of the reported BAFF increase in MS patients under IFN-β therapy with changes of humoral response against MAP_2694. For these reasons, we investigated 44 MS patients before and after IFN-β therapy. A significant difference of BAFF levels was found between men and women with MS; moreover, we confirmed that IFN-β therapy strongly induces BAFF serum levels, but this was not related to the modification of immunological response against MAP_2694. In conclusion, our study highlights that IFN-β therapy induces the potent B cell survival factor BAFF without alterations of the humoral immune response against MAP.