Bacillus Subtilis-Derived Exopolysaccharide Halts Depigmentation and Autoimmunity in Vitiligo.

Vitiligo has a complex multifactorial etiology involving a T-cell-mediated autoimmune response to cutaneous melanocytes. Microbial dysbiosis has been assigned a contributing role in vitiligo etiology. Treating vitiligo can be a challenging task, and finding novel treatment approaches is crucial. In this study, we tested exopolysaccharides (EPSs) isolated from Bacillus subtilis as a microbiome-based therapy. Vitiligo-prone h3TA2 mice were treated by weekly intraperitoneal EPS injection for 18 weeks. Depigmentation was evaluated over time, measuring immune responses at end point. EPS treatment significantly limited the rate of depigmentation. The abundance of cutaneous T cells, specifically CD8+ cytotoxic T cells, was reduced, whereas regulatory T cells were more abundant in the skin of treated mice than in untreated mice. Moreover, EPS treatment was associated with increased numbers of splenic M2 macrophages, elevated splenic indoleamine 2,3-dioxygenase expression, and a systemic cytokine shift toward a type 2 pattern of cytokines. Importantly, splenocytes retrieved from EPS-treated mice were less responsive to cognate tyrosinase peptide, as demonstrated by limited release of IFN-γ and other inflammatory cytokines. In summary, EPS isolated from Bsubtilis interfered with T-cell-mediated depigmentation in the h3TA2 mouse model of vitiligo, suggesting that Bsubtilis EPS could serve as a novel treatment entity for vitiligo.