A DNA vaccine against Escherichia coli O157:H7

Infection with Escherichia coli O157:H7 rarely leads to bloody diarrhea and causes hemolytic uremic syndrome with renal failure that can be deadly dangerous. Intimin, translocated Intimin receptor (Tir), and enterohemorrhagic E. coli (EHEC) secreted protein A (EspA) proteins are the virulence factors expressed by locus of enterocyte effacement locus of EHEC. This bacterium needs EspA as a conduit for Tir delivery into the host cell and the surface arrayed Intimin, which docks the bacterium to the translocated Tir.

Here we used triplet synthetic gene (eit) which was designed from three genes: espA coding EspA 120 lacking 36 amino acids from the N-terminal of the protein, eae coding Intimin constructed of 282 amino acids from the C-terminal and tir coding Tir 103, residues 258-361 which interacts with Intimin. The multimeric gene was cloned in two eukaryotic vectors pAAV-multiple cloning site-green fluorescent protein and pCI-neo. The pAAV was used for gene expression assay in cell line 293T and pCI-neo-EIT (EspA, Intimin, Tir) was used as DNA vaccine in mice. Test groups were injected intramuscularly with pCI-neo-EIT four times and mice control group was injected under the same conditions with PBS or pCI-neo vector.

The titration of serums showed that BALB/c mice were successfully immunized with DNA vaccine compared to control groups and also they were protected against challenges of live oral using E. coli O157:H7.

The results suggest that the DNA vaccine could induce protective immunity either alone or in combination with purified antigens to reduce EHEC infection.