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

Abstract 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.