The improvement of immunity and activation of TLR2/NF-κB signaling pathway by Romboutsia ilealis in broilers

This study was conducted to investigate the effects of Romboutsia (R.) ilealis on the immune function of broilers and the underlying mechanisms. A total of 48 one-d-old Arbor Acres broilers were allocated to 4 groups as follows: broilers treated daily with 1 mL live R. ilealis in GAM broth media (0, 1×104, 1×106 and 1×108 CFU/mL) from d 1 to 7. Samples were collected on d 8 and 14. The results showed that R. ilealis had no negative effect on the body weight of broilers (P > 0.05). R. ilealis significantly increased the levels of lysozyme, IFN-γ, IFN-γ/IL-4, and IgG in the serum (P < 0.05). R. ilealis significantly increased the levels of IL-4, IFN-γ, sIgA, lysozyme, and iNOS in the ileal mucosa (P < 0.05). R. ilealis significantly increased the mRNA levels of TLR2, TLR4, NF-κB, IL-1β, TNF-α, IFN-γ, IgA, pIgR, iNOS, and MHC-Ⅱ in the ileum (P < 0.05). R. ilealis significantly increased the relative abundance of Enterococcus and Paracoccus in the jejunum and ileum, ileal Candidatus Arthromitus, and cecal Romboutsia and Intestinimonas (P < 0.05). Correlation analysis showed that Enterococcus, Paracoccus, Romboutsia, and Intestinimonas were significantly positively correlated with humoral immune function (P < 0.05). In conclusion, Romboutsia ilealis boosted the immune system, activated the intestinal TLR2/NF-κB signaling pathway, and improved the gut microbiota in broilers.