Probiotic modulation of dendritic cells co-cultured with intestinal epithelial cells

AIM： To investigate cytokine production and cell surface phenotypes of dendritic cells （DC） in the presence of epithelial cells stimulated by probiotics.METHODS： Mouse DC were cultured alone or together with mouse epithelial cell monolayers in normal or in- verted systems and were stimulated with heat-killed probiotic bacteria, Bifidobacterium lactis ADO 11 （BL）, Bifidobacterium bilfidum BGN4 （BB）, Lactobacillus casei IBS041 （LC）, and Lactobacillus acidophilus AD031 （LA）, for 12 h. Cytokine levels in the culture supernatants were determined by enzyme-linked immunosorbent as say and phenotypic analysis of DC was investigated by flow cytometry.RESULTS： BB and LC in singlecultured DC increased the expression of I-Ad, CD86 and CD40 （I-Ad, 18.51 vs 30.88, 46.11, CD86, 62.74 vs 92.7, 104.12; CD40, 0.67 vs 6.39, 3.37, P 〈 0.05）. All of the experimental probiot-ics increased the production of inflammatory cytokines, interleukin （IL）-6 and tumor necrosis factor （TNF）-α. However, in the normal coculture systems, LC and LA decreased the expression of I-A^α （39.46 vs 30.32, 33.26, P 〈 0.05）, and none of the experimental probiotics increased the levels of IL-6 or TNF-α. In the inverted coculture systems, LC decreased the expression of CD40 （1.36 vs -2.27, P 〈 0.05）, and all of the experimental probiotics decreased the levels of IL-6. In addition, BL increased the production of IL-10 （103.8 vs 166.0, P 〈 0.05） and LC and LA increased transforming growth factor-13 secretion （235.9 vs 618.9, 607.6, P 〈 0.05）.CONCLUSION： These results suggest that specific pro- biotic strains exert differential immune modulation mediated by the interaction of dendritic cells and epithelial cells in the homeostasis of gastrointestinal tract.

Lactobacillus salivarius HHuMin-U Activates Innate Immune Defense against Norovirus Infection through TBK1-IRF3 and NF-κB Signaling Pathways

The composition of commensal bacteria plays a critical role in controlling immune responses in the intestine.Studies have shown that specific bacterial strains may have the capacity to enhance host immune defense against gastrointestinal viral infections.While norovirus is known to be the most common cause of gastroenteritis,leading to an estimated 200,000 deaths every year,identification of bacterial strains with protective effects against norovirus infection remains elusive.Here,we discovered Lactobacillus salivarius HHuMin-U(HHuMin-U)as a potent antiviral strain against norovirus infection.HHuMin-U significantly suppressed murine norovirus replication and lowered viral RNA titers in macrophages.The transcriptome sequencing(RNA sequencing)analysis revealed that HHuMin-U markedly enhanced the expression level of antiviral interferon-stimulated genes compared to mock treatment.HHuMin-U treatment dose-dependently induced type I interferons(IFN-αand IFN-β)and tumor necrosis factor-αproduction in mouse and human macrophages,promoting antiviral innate responses against norovirus infection.Investigation on the molecular mechanism demonstrated that HHuMin-U can activate nuclear factorκB and TANK-binding kinase 1(TBK1)–interferon regulatory factor 3 signaling pathways,leading to the phosphorylation of signal transducer and activator of transcription 1 and signal transducer and activator of transcription 2,the key mediators of interferon-stimulated genes.Finally,oral administration of HHuMin-U increased IFN-βlevels in the ileum of mice and altered the gut microbiome profile.These results suggest the species/strain-specific importance of gut microbial composition for antiviral immune responses and the potential use of HHuMin-U as a probiotic agent.