IFN-β facilitates neuroantigen-dependent induction of CD25⁺ FOXP3⁺ regulatory t cells that suppress experimental autoimmune encephalomyelitis

This study introduces a flexible format for tolerogenic vaccination that incorporates IFN-β and neuroantigen (NAg) in the Alum adjuvant. Tolerogenic vaccination required all three components, IFN-β, NAg, and Alum, for inhibition of experimental autoimmune encephalomyelitis (EAE) and induction of tolerance. Vaccination with IFN-β ⁺ NAg in Alum ameliorated NAg-specific sensitization and inhibited EAE in C57BL/6 mice in pretreatment and therapeutic regimens. Tolerance induction was specific for the tolerogenic vaccine Ag PLP178-191 or myelin oligodendrocyte glycoprotein (MOG)35-55 in proteolipid protein-and MOGinduced models of EAE, respectively, and was abrogated by pretreatment with a depleting anti-CD25 mAb. IFN-β/Alum-based vaccination exhibited hallmarks of infectious tolerance, because IFN-β ⁺ OVA in Alum-specific vaccination inhibited EAE elicited by OVA ⁺ MOG in CFA but not EAE elicited by MOG in CFA. IFN-β ⁺ NAg in Alum vaccination elicited elevated numbers and percentages of FOXP3⁺ T cells in blood and secondary lymphoid organs in 2D2 MOG-specific transgenic mice, and repeated boosters facilitated generation of activated CD44high CD25⁺ regulatory T cell (Treg) populations. IFN-β and MOG35-55 elicited suppressive FOXP3⁺ Tregs in vitro in the absence of Alum via a mechanism that was neutralized by anti-TGF-β and that resulted in the induction of an effector CD69⁺ CTLA-4⁺ IFNAR⁺ FOXP3⁺ Treg subset. In vitro IFN-β ⁺ MOG-induced Tregs inhibited EAE when transferred into actively challenged recipients. Unlike IFN-β ⁺ NAg in Alum vaccines, vaccination with TGF-β ⁺ MOG35-55 in Alum did not increase Treg percentages in vivo. Overall, this study indicates that IFN-β ⁺ NAg in Alum vaccination elicits NAg-specific, suppressive CD25⁺ Tregs that inhibit CNS autoimmune disease. Thus, IFN-β has the activity spectrum that drives selective responses of suppressive FOXP3⁺ Tregs.