Preparation of Escherichia coli ghost of anchoring bovine Pasteurella multocida OmpH and its immunoprotective effect

Pasteurella multocida is a pathogen that can infect humans and animals. A ghost is an empty bacterial body devoid of cytoplasm and nucleic acids that can be efficiently presented by antigen-presenting cells. To study a novel ghost vector vaccine with cross-immune protection, we used bacteriophage PhiX174 RF1 and Pasteurella multocida standard strain CVCC393 as templates to amplify the split genes E and OmpH to construct a bidirectional expression vector E’-OmpH-pET28a-ci857-E. This is proposed to prepare a ghost Escherichia coli (engineered bacteria) capable of attaching and producing Pasteurella multocida OmpH on the inner membrane of Escherichia coli (BL21). The aim is to assess the antibody levels and the effectiveness of immune protection by conducting a mouse immunoprotective test. The bidirectional expression vector E’-OmpH-pET28a-ci857-E was successfully constructed. After induction by IPTG, identification by SDS-PAGE, western blot, ghost culture and transmission electron microscope detection, it was proven that the Escherichia coli ghost anchored to Pasteurella multocida OmpH was successfully prepared. The immunoprotective test in mice showed that the antibody levels of Pasteurella multocida inactivated vaccine, OmpH, ghost (aluminum glue adjuvant) and ghost (Freund’s adjuvant) on day 9 after immunization were significantly different from those of the PBS control group (P < 0.01). The immune protection rates were 100%, 80%, 75%, and 65%, respectively, and the PBS negative control was 0%, which proved that they all had specific immune protection effects. Therefore, this study lays the foundation for the further study of ghosts as carriers of novel vaccine-presenting proteins.