Assessment of immune responses of the flagellin (FliC) fused to FimH adhesin of Uropathogenic Escherichia coli

Urinary tract infection (UTI) caused by Uropathogenic Escherichia coli (UPEC) is one of the most common infectious diseases in the world. Despite extensive efforts, a vaccine that protects humans against UTI is currently missing. In this study, the immunogenicity of flagellin (FliC) of UPEC strain in different vaccine combinations with FimH antigen of UPEC and conventional adjuvant Montanide ISA 206 was assessed. Finally, efficacy of the immune responses was evaluated for protection of the bladder and kidney of challenged immunized mice. Mice immunized with the fusion FimH·FliC induced significantly higher anti-FliC humoral (IgG1) and cellular (Th1 and Th2) immune responses than with FliC alone or FliC admixed with FimH. The Montanide enhanced the immune responses of FliC antigen and directed the anti-FliC responses preferentially toward Th1. The FliC vaccine combinations reduced bladder infection as compared to control mice. The fusion FimH·FliC and FliC admixed with FimH and Montanide combinations gave the best results in protection of kidney infection, compared to the control mice. The results of this study propose new promising vaccine combinations based on the FliC antigen and Montanide against UTI caused by UPEC.

► We describe the first UTI vaccine candidate based on the FliC or Montanide. ► FliC induced strong humoral and cell immune responses. ► Montanide directed the anti-FliC responses to Th1 direction. ► FimH·FliC and FimH + FliC + Montanide significantly reduced kidney colonization. ► This study presents FimH·FliC as a promising vaccine candidate against UTI.