We investigated the inhibitory effects of oral administration of Tetragenococcus halophilus MN45 (MN45) isolated from miso on the development of atopic dermatitis (AD) using NC/Nga AD model mice. NC/Nga mice were fed a diet containing 0.05% or 0.5% MN45 (0.05% or 0.5% MN45 groups) or lacking MN45 (control group). Mice were sensitized and boosted with picryl chloride by topical application once per week. IgE production in serum, clinical score and ear thickness in both MN45 groups were significantly suppressed. In addition, IgE and IL-17 production from splenocytes from mice in both MN45 groups were significantly decreased. IL-4 production from splenocytes in the 0.5% MN45 group decreased significantly, while IL-10 production from splenocytes in the 0.05% MN45 group increased significantly. These results demonstrate that intake of MN45 is effective in preventing and alleviating the development of type-1 allergic symptoms in humans.

We measured the ability of 100 strains of lactic acid bacteria (LAB) isolated from miso to induce Th1-type cytokines (interleukin (IL)-12 and IFN-γ) using mouse Peyer's patch (PP) cells, and selected Tetragenococcus halophilus MN45 strain (MN45) as the strain with the potential for a strong anti-allergic effect. MN45 cultured in medium containing 15% NaCl for more than 2 days showed the strongest activity of Th1-type cytokine induction among MN45 cultured at various NaCl concentrations and culture times. Next, we analyzed the ability of MN45 to suppress IgE production and the mechanism thereof by neutralizing IL-12 and IFN-γ using PP cells and splenocytes from ovalbumin (OVA)-induced allergic diarrhea model mice. Analysis revealed that MN45 induced IL-12 first, and then IL-12 induced IFN-γ strongly and inhibited IgE production. These results indicate that MN45 may exert an anti-allergic effect.