目的 利用大肠杆菌Nissle 1917（EcN）表达抗菌免疫肽Scygonadin（Scy），并评估EcN-Scy缓解结肠炎的作用，为研发新型抗生素替代品提供理论依据。 方法 用PCR扩增载体pnirBMisl（pnir）与抗菌免疫肽Scy目的基因，通过同源重组获得重组载体EcN-Scy。选用20只8周龄雌性BALB/c小鼠，平均分为4组（对照组、DSS组、DSS+EcN组和DSS+EcN-Scy组），每2 d分别灌胃小鼠PBS、EcN菌液或EcN-Scy菌液并记录其体质量，试验期14 d。其中除对照组外，其他3组第0~7天通过在饮水中添加3% DSS诱导结肠炎。第14天麻醉后处死小鼠并采集血清和结肠组织样本进行检测。 结果 与DSS组相比，EcN-Scy处理显著缓解了小鼠体质量下降（P<0.05）和由DSS引起的结肠缩短的症状（P<0.05），明显改善了结肠绒毛结构。与DSS组相比，DSS+EcN-Scy组血清中ALP和Urea水平分别显著升高28.6 U/L、1.35 mol/L（P<0.05）；TBil和LDH水平有降低趋势（P>0.05）。与DSS组相比，DSS+EcN-Scy组血清中的促炎因子TNF-α、MCP1和IL-1β水平分别显著降低18.9%、50.9%和8.9%（P<0.05），结肠中MCP1和IL-6分别降低了40.4%和21.9%（P<0.05）。 结论 成功利用工程菌EcN表达抗菌免疫肽Scy，具有显著缓解小鼠结肠炎的效果，能够改善DSS诱导的小鼠体质量下降、结肠缩短及形态破损，并降低血清和结肠炎症因子水平。

Objectives Escherichia coli Nissle 1917 (EcN) was used to express antimicrobial immune peptide Scygonadin (Scy) and the effects of EcN-Scy on alleviating colitis were evaluated to provide theoretical basis for the development of novel substitutes for antibiotic. Methods The vector pnirBMisl (pnir) and the target gene of antimicrobial peptide Scy were amplified with PCR, and the recombinant vector EcN-Scy was obtained by homologous recombination connection. Twenty 8-week-old female BALB/c mice were randomly divided into four groups including the control group, DSS group, DSS+EcN group, and DSS+EcN Scy group. The mice were orally administered with PBS, EcN bacterial solution, or EcN-Scy bacterial solution every 2 days and their body weight was recorded. The experiment lasted for 14 days. Except for the control group, the other three groups were induced colitis by adding 3% DSS to their drinking water from day 0 to day 7. Mice were killed on day 14 after anesthesia, and samples of serum and colon tissue were collected for testing. Results EcN-Scy treatment significantly alleviated the weight loss in mice (P<0.05) and the symptoms of colon shortening caused by DSS (P<0.05), and significantly improved the structure of colonic villi compared with DSS group. The level of ALP and Urea in serum in the DSS+EcN-Scy group was significantly increased by 28.6 U/L and 1.35 mol/L (P<0.05) compared with that in DSS group. The level of TBil and LDH had a decreasing trend (P>0.05). The level of pro-inflammatory cytokines TNF-α, MCP1, and IL-1 β in the serum of the DSS+EcN-Scy group was significantly reduced by 18.9%, 50.9%, and 8.9%, respectively (P<0.05), and the level of MCP1 and IL-6 in the colon were reduced by 40.4% and 21.9%, respectively (P<0.05) compared with that in the DSS group. Conclusions The antimicrobial immune peptide Scy was successfully expressed with the engineered bacterium EcN, which has a significant effect on alleviating colitis in mice. It can improve the weight loss, colon shortening, and morphological damages in mice induced by DSS, and reduce the level of inflammatory factors in serum and colon.