Evaluation of mammalian codon usage of fimH in DNA vaccine design

Uropathogenic Escherichia coli (UPEC) bacteria are the principal cause of urinary tract infections (UTI). Because these bacteria propagate intracellularly, the cellular immune response is an important factor in UTIs. Therefore, we designed a genetic construct to induce a cellular immune response. In order to develop a genetic construct that induces strong cellular immunity against this pathogen, we used the fimH synthetic gene according to mammalian codon usage, and the gene expression was compared with wild type codon usage. Initially, we designed two constructs, pVAX/fimH mam and pVAX/fimH wt, which contain mammalian and wild type codon usage, respectively. The Cos-7 cell line was transfected separately with a complex of pVAX/fimH mam-ExGene 500 poly cationic polymer and pVAX/fimH wt-ExGene 500 poly cationic polymer. Expression of the fimH gene in both constructs in COS7 cells was confirmed by RT-PCR, SDS-PAGE, and Western blotting. Both of the pVAX/fimH cassettes expressed inserted fimH genes (mam and wt) in Cos-7 cells. Our results suggest that codon optimization successfully expressed the fimH gene because the fimH gene with mammalian codon usage is compatible with the eukaryotic expression system. Therefore, mammalian codon usage could be appropriate in a pVAX/fimH construct as a DNA vaccine.