The Levilactobacillus Brevis NZ3 Isolated From Fermented Brassica Rapa L. Induces IL‐15 Production in Dendritic Cells via Inducing IFN‐α

Interleukin‐15 (IL‐15) is a potential adjuvant in the activation of antitumor and antiviral immunity. Certain fermented food components possess immunomodulatory effects. We previously showed that lactic acid bacteria (LAB) isolated from Nozawana‐zuke—the traditional Japanese fermented Brassica rapa L. pickle—activate immune function. Here we aimed to identify the LAB strain in fermented B. rapa L. that can markedly induce the expression of IL‐15 mRNA in dendritic cells (DCs). We found that the Levilactobacillus brevis NZ3 strain isolated from B. rapa L. induces IL‐15 production in DCs. We also provided mechanistic insight into the mechanism by which the NZ3 strain induces IL‐15 production in DCs. We report that the NZ3 strain‐induced IL‐15 production in DCs is mediated by Toll‐like receptor 3 signaling. Furthermore, inhibiting the interferon‐α/β receptor alpha chain abrogated the NZ3 strain‐induced IL‐15 production. Further analysis using a Protein Kinase B (AKT) inhibitor revealed that the NZ3 strain‐induced IL‐15 production is mediated by AKT signaling, which occurs downstream of Interferon‐α/β receptor signaling. Overall, our results indicate that the Levilactobacillus brevis NZ3 strain may serve as a potentially beneficial immunomodulatory bacterial strain. Moreover, due to its ability to induce IL‐15 production, the NZ3 strain may serve as a candidate immunomodulatory strain for future studies.