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Probiotic bacteria have been shown to have health benefits in various situations (inflammation, allergy, infection). We previously showed that a bacteria-free fermentation product of Bifidobacterium breveC50 (BbC50sn) induced high IL-10 secretion by human dendritic cells. As IL-10 is a regulatory cytokine, the aim of the present study was to examine whether DCs cultured in the presence of BbC50sn could induce regulatory T cells in an allogeneic context. Purified CD4+CD25-human T cells were co-cultured with allogeneic BbC50sn-treated dendritic cells for 4 weeks. The T cell population (BbC50sn-T) was analysed both at phenotypical and functional [ability to inhibit a mixed lymphocyte reaction (MLR)] levels. We showed that T lymphocytes acquired phenotype characteristics of regulatory T cells after 4 weeks of co-culture with BbC50sn-DCs, and inhibited in vitroT lymphocyte proliferation and IFN-? production in an MLR. Transwell experiments demonstrated that this suppressive activity was not T cell contact-dependent but probably mediated by a soluble factor. Although BbC50sn-T cells secreted significant amounts of IL-10 and TGF-ß, their suppressive effect is most likely not mediated through these cytokines. This is, to our knowledge, the first demonstration of in vitroregulatory T cell induction by a bacteria-free fermentation product in an allogeneic context.

To determine whether long‐term consumption of a fermented infant formula could influence the incidence of acute diarrhea and its severity in healthy infants. Nine hundred seventy‐one infants, ranging in age from 4 to 6 months, were included in a randomized, double‐blind, placebo‐controlled trial during a period of 5 months. They consumed daily either a fermented infant formula (FF) (fermentation with Bifidobacterium breve C50and Streptococcus thermophilus 065) or a standard infant formula (SF) of the same nutritional composition. Number and duration of acute diarrhea episodes were evaluated. Severity of the episodes was determined by the number of hospital admissions, incidence of dehydration, number of medical consultations, number of oral rehydration solution prescriptions, and number of formula switches. Growth of the infants and acceptability of the formulas were identical in the two groups. Incidence, duration of diarrhea episodes, and number of hospital admissions did not differ significantly between groups. Episodes were less severe in the FF (fermented formula) group. There were fewer cases of dehydration 2.5%versus6.1% (P= 0.01), fewer medical consultations (46%v56.6%, P= 0.003), fewer ORS prescriptions 41.9%v51.9% (P= 0.003) and fewer switches to other formulas (59.5%v74.9%, P= 0.0001) in FF infants compared to SF. A fermented formula may reduce the severity of acute diarrhea among healthy young infants. This outcome may be linked to the bifidogenic effects of fermentation products and their interactions with the intestinal immune system.