Designing of a chimeric protein contains StxB, intimin and EscC against toxicity and adherence of enterohemorrhagic Escherichia coli O157:H7 and evaluation of serum antibody titers against it

•Considering the importance of EHEC, and on the other hand, the lack of an efficient vaccine in this terms.•The present study aims to design a novel chimeric protein as immunogen against EHEC.•A chimeric protein composed of StxB, intimin and EscC was designed, by using immunoinformatics tools.•StxB, intimin and EscC chimeric protein have immunogenicity. Enterohemorrhagic Escherichia coli (EHEC) O157:H7 strain is known as one of the major human foodborne pathogens. Lack of effective clinical treatment for human diarrheal diseases confirms the need for vaccine production against enteric bacteria such as E.coli O157:H7. Shiga-like toxin (Stx), EscC, and Intimin are the main important virulent factors of this enteric pathogen. In the present study, a comparative Omics analysis was conducted to identify most invasion EHEC antigenic factors as a potential immunogen. SEI (Stx-EscC-Intimin) trivalent chimeric protein was designed from the exposed and epitope rich part of these virulence factors. Sequence optimization, physicochemical properties, mRNA folding, three-dimensional structure and immunoinformatics data were investigated. The chimeric gene was synthesized with codon bias of E. coli. Recombinant protein was expressed and confirmed by western blot analysis. To evaluate the immunogenicity of the designed protein, the protein was administered to BALB/c mice and the serum IgG was determined by ELISA. Based on the Ramachandran plot, the validation data showed that 90.1 % of residues lie in the favored region. The high antigenicity of the multimeric protein was predicted by the immunoinformatic analysis. Epitope prediction had shown the proper distribution of linear and conformational B-cell epitopes and the competition of T-cell epitopes to bind MHC molecules too. Recombinant ESI Protein with 74.5 kDa was expressed in E. coli. Western blot analysis by anti-Stx antibody, confirmed a single band of chimeric protein. Consequently, the chimeric gene was designed and constructed after assessments. From in silico approach, the protein deduced from this cassette can be an immunogen candidate, and act against toxicity and adherence of EHEC.