Identification and Evaluation of a Panel of Strong Constitutive Promoters in Listeria monocytogenes for Improving the Expression of Foreign Antigens

Attenuated Listeria monocytogenes (L. monocytogenes) could be used as a vaccine vector for immunotherapy of tumors or pathogens. However, the lack of reliable promoters limits its ability to express foreign antigens. In this work, 21 promoters from L. monocytogenes were identified by RNA-seq analysis under two conditions of pH 7.4 and pH 5.5. Based on the constructed fluorescence report system, 7 constitutive promoters showed higher strength than that of Phelp, a previously reported strong promoter. Further, the selected 5 constitutive promoters also showed high activity in the production of UreB, a widely used antigen against Helicobacter pylori (H. pylori). In particular, a well-characterized constitutive promoter P18, which performed best in both fluorescence intensity and UreB production, was proved to be highly active in vitro and in vivo. In summary, we provide a useful promoter library for Listeria species and offer a reference for constitutive promoter mining in other organisms. Key pointsO_LI21 promoters from L. monocytogenes were identified by RNA-seq. C_LIO_LIFluorescent tracer of L. monocytogenes (P18) was performed in vitro and in vivo. C_LIO_LIA well-characterized constitutive promoter P18 could improve the expression level of a foreign antigen UreB in L. monocytogenes C_LI