Paving the way to construct a new vaccine against Escherichia coli from its recombinant outer membrane protein C via a murine model

• Expression of OmpC in Escherichia coli by an auto-induction system.
• High immunogenicity and significant immunologic cross-reactivity of rOmpC.
• The anti-rOmpC sera activated complement pathways and induced opsonophagocytosis.
• Vaccination with rOmpC improved the survival ratios of mice.
• Vaccination with rOmpC reduced the adhesion and colonization of E. coli.

Pathogenic Escherichia coli (E. coli) is one of the primary pathogens in humans and domestic animals. Outer membrane protein C (OmpC) has previously been demonstrated to be a protective antigen. In this study, the immunogenicity and protection efficacy of the recombinant OmpC (rOmpC) protein was investigated in a mouse model. OmpC from E. coli CVCC 1515 shares a high homology (93–100%) with other Escherichia and Shigella strains. OmpC was expressed in E. coli BL21 (DE3) system, with the average molecular weight of 40 kDa and with the purity of 96%. Immunization of mice with rOmpC triggered an immune response. The titers of anti-rOmpC sera against rOmpC and whole cells were 1:240,000 and 1:27,000, respectively. rOmpC provided a high level of immunogenicity to protect mice against E. coli infection and cross-protection against Shigella strains. The anti-rOmpC sera induced the phagocytic activity of neutrophils against E. coli. The survival ratios of mice immunized with rOmpC and PBS were 50% and 20%, respectively, 72 h post challenge with E. coli CVCC 1515. rOmpC also supplied partial protection against the oral infection of E. coli CICC 21530. Based on these findings, rOmpC is a potential candidate to be a vaccine against E. coli infections.

The ompC gene was cloned from Escherichia coli CVCC1515 and was expressed in E. coli BL21 (DE3). After purification by Ni2+-NTA affinity chromatography and refolding using folding buffer, the rOmpC protein was used to vaccinate mice. Two weeks after the final immunization, the mice were challenged with E. coli. The anti-rOmpC sera were evaluated by iELISA, OPKA, SBA and protection efficacy in vitro and in vivo, respectively. The results indicated that the anti-rOmpC sera have a high affinity to Escherichia and Shigella strains (I), can induce a significantly high level of opsonphagocytic killing (II), and activate complement systems (III).Figure optionsDownload as PowerPoint slide