Construction of a Recombinant OmpC Dominant Epitope-Based Vaccine Against Escherichia coli and Evaluation of Its Immunogenicity and Protective Immunity

Escherichia coli can cause human diseases and cow mastitis. Use of antibiotics in the treatment of E. coli infections causes drug residues in dairy products and develops antibiotic resistance. Thus, it is of prime importance to find a new solution for the treatment of E. coli infection.
The present study aimed at constructing a novel cell epitope-based polypeptide vaccine (OmpC-EP) against E. coli infection.
Based on the outer membrane protein C (OmpC) of E. coli, we used ABCpred and BepiPred method to obtain its B cell epitopes, whereas nHLAPred and ProPred methods were used to obtain the CTL and Th cell epitopes, respectively. The predicted cell epitopes were recomposed using DNASTAR software to obtain a cell epitope-based polypeptide (OmpC-EP) of high antigenicity, which was purified by Ni-NTA flow resin. Purified OmpC-EP was mice immunized to prepare a polyclonal antibody; Western blotting analysis was used to detect antibody specificity. Pull down and ELISA detected the interaction between OmpC-EP antibodies and E. coli. Active immunity mice and challenge of E. coli were used to detect the immune protection of CM-TEP.
A novel epitope peptide (OmpC-EP), with a MW of 12.5 kDa was designed, and Ni-NTA purified OmpC-EP was mice immunized to prepare a polyclonal antibody. OmpC-EP antiserum had a good specificity and directly interacted with E. coli. Specific immunity was activated in mice, and OmpC-EP displayed a significant immune protective effect (62.5%), which was slightly higher than that of the OmpC protein (56.3%) following infection with E. coli.
The results of the present study revealed that OmpC-EP has a good immunogenicity and possesses a significant immune protective function. OmpC-EP is expected to be an approach to construct a vaccine against E. coli.