Preventative delivery of IL-35 by Lactococcus lactis ameliorates DSS-induced colitis in mice

Ulcerative colitis (UC) is one of the two major forms of inflammatory bowel disease (IBD) characterized by superficial mucosal inflammation, rectal bleeding, diarrhea, and abdominal pain. Anti-inflammatory and immunosuppressive drugs have been used in the therapy of human UC. Interleukin (IL)-35, which functions as an anti-inflammatory cytokine, has been shown to play a potential therapeutic role in a UC-like mouse colitis induced by dextran sodium sulfate (DSS). However, the contribution of IL-35 via oral administration to colitis prevention has not been determined. In order to explore its preventative potentiality, a dairy Lactococcus lactis NZ9000 strain was engineered to express murine IL-35 (NZ9000/IL-35), and this recombinant bacteria was applied to prevent and limit the development of DSS-induced mouse colitis. We found that oral administration of NZ9000/IL-35 induced the accumulation of IL-35 in the gut lumen of normal mice. When administrated preventatively, NZ9000/IL-35-gavaged mice exhibited decreased weight loss, DAI score, colon shortening as well as colitis-associated histopathological changes in colon, indicating that the oral administration of NZ9000/35 contributed to the suppression of DSS-induced colitis progression. Moreover, much less Th17 cells and higher level of Treg cells in lamina propria, as well as increased colon and serum levels of IL-10 with a concomitant reduced pro-inflammatory cytokines, IL-6, IL-17A, IFN-γ, and TNF-α were apparently regulated by NZ9000/IL-35 in colitis mice. Together, we put forward direct evidence pinpointing the effectiveness of NZ9000/IL-35 in preventing UC-like mouse colitis, implying a potential candidate of this recombinant Lactococcus lactis that prevent the progression of IBD.