Extracellular vesicle-derived protein from Bifidobacterium longum alleviates food allergy through mast cell suppression.

Background The incidence of food allergies has increased dramatically during the last decade. Recently, probiotics have been studied for the prevention and treatment of allergic disease. Objective We examined whether Bifidobacterium longum KACC 91563 and Enterococcus faecalis KACC 91532 have the capacity to suppress food allergies. Methods B longum KACC 91563 and E faecalis KACC 91532 were administered to BALB/c wild-type mice, in which food allergy was induced by using ovalbumin and alum. Food allergy symptoms and various immune responses were assessed. Results B longum KACC 91563, but not E faecalis KACC 91532, alleviated food allergy symptoms. Extracellular vesicles of B longum KACC 91563 bound specifically to mast cells and induced apoptosis without affecting T-cell immune responses. Furthermore, injection of family 5 extracellular solute-binding protein, a main component of extracellular vesicles, into mice markedly reduced the occurrence of diarrhea in a mouse food allergy model. Conclusion B longum KACC 91563 induces apoptosis of mast cells specifically and alleviates food allergy symptoms. Accordingly, B longum KACC 91563 and family 5 extracellular solute-binding protein exhibit potential as therapeutic approaches for food allergies.