Current Progress and Challenges in the Study of Adjuvants for Oral Vaccines.

Over the past 20 years, a variety of potential adjuvants have been studied to enhance the effect of oral vaccines in the intestinal mucosal immune system; however, no licensed adjuvant for clinical application in oral vaccines is available. In this review, we systematically updated the research progress of oral vaccine adjuvants over the past 2 decades, including biogenic adjuvants, non-biogenic adjuvants, and their multi-type composite adjuvant materials, and introduced their immune mechanisms of adjuvanticity, aiming at providing theoretical basis for developing feasible and effective adjuvants for oral vaccines. Based on these insights, we briefly discussed the challenges in the development of oral vaccine adjuvants and prospects for their future development.

Deletion of the cheZ gene results in the loss of swimming ability and the decrease of adhesion ability to Caco-2 cells in Escherichia coli Nissle 1917.

The aim of this study was to elucidate the biological functions of the motility regulatory protein CheZ in the probiotic strain Escherichia coli Nissle 1917. A cheZ gene deletion strain Nissle 1917ΔcheZ was constructed using the CRISPR/Cas9 two-plasmid system, and the corresponding complemented strain Nissle 1917ΔcheZ/pBR322-cheZ was established. Combined studies of growth kinetics testing, motility assays, swarming motility assays, and bacterial adherence assays were performed to study the motility regulatory protein CheZ-mediated functions in the prototype Nissle 1917 strain, its isogenic cheZ mutant, and the corresponding complemented strain. The growth rate of the cheZ mutant strain was lower than that of the wild-type strain in the exponential growth phase. The motility of the cheZ mutant strain was significantly lower than that of the wild-type strain. And the adhesion ability of ΔcheZ mutant to the Caco-2 cells was significantly lower than that of the wild-type strain and complemented strain. In conclusion, the results presented in our study suggested that the deletion of the cheZ gene in E. coli Nissle 1917 led to a significant reduction of its swimming ability and a subsequent marked decrease of adhesion to the Caco-2 cells.