Production of Chimeric Tir-intimin Protein from E. coli O157:H7 in the Tobacco (Nicotiana tobbacum) Plant and its Immunological Evaluation in an Animal Model

Escherichia coli (E. coli) O157: H7 is one of the most important pathogenic causes of hemorrhagic colitis in humans. Cattle are the main reservoirs of this bacteria and vaccination is a key mechanism for its control. The intimin، translocated intimin receptor (tir)، and EspA proteins are virulence factors expressed by the LEE locus of enterohemorrhagic E. coli. EspA protein is a member of the type III secretion system (TTSS) needle complexes that delivers the tir protein into the host cell. Surface arrayed intimin docks the bacterium to the translocated intimin receptor (Tir). This intimate linkage is the starting point for attachment and effacing lesions. We hypothesize that the chimeric recombinant forms of two of these three effectors، as edible-based immunogens، would reduce colonization of E. coli O157: H7 in the mice model. We constructed a synthetic gene (it) composed of eae (i) and tir (t) attached together by a peptide linker. The synthetic gene (it) was codon optimized based on the tobacco (Nicotiana tobbacum) plant and cloned into plant expression vectors adjacent to CaMV35S promoters for expression in transgenic tobacco plants. The antigen produced in this plant was orally fed to mice. Immunization of the mice model by the transgenic plant that contained the divalent immunogen showed the presence of IgG antibodies against E. coli O157: H7. This method could be an effective tool for protecting against E. coli O157: H7 hemorrhagic colitis.