Expression and immunoreactivity of a recombinant multi-epitope antigen designed based on four major structural proteins of avian infectious bronchitis virus

The development of rapid, simple, and sensitive diagnostic methods for identification of avian infectious bronchitis virus (IBV) is crucial for the effective control of avian infectious bronchitis. In the present study, a tandemly arranged multiepitope peptide (named SEMN) was designed with four antigenic regions derived from four major structural proteins of IBV. Then, we performed codon optimization of SEMN gene by changing the codon-adaptation index from 0.45 to 0.94 and expressed the optimized gene in codon bias-adjusted Escherichia coli Rosetta (DE3), followed by determination of the immunoreactivity of the purified protein. Bioinformatics analysis of SEMN showed a high antigenicity, surface probability and hydrophilicity. The recombinant protein rSEMN was expressed both in soluble forms and as inclusion bodies, and the molecular weight of rSEMN was about 39 kDa. The preliminary diagnostic performance of rSEMN was confirmed by Western blotting analysis using chicken anti-IBV polyclonal antibodies. Further studies are needed to evaluate the immunogenicity in animal models and to give a final assessment of the diagnostic utility of this recombinant multi-epitope antigen.