Effects of the administration of cholera toxin as a mucosal adjuvant on the immune and protective response induced by Proteus mirabilis MrpA fimbrial protein in the urinary tract

Proteus mirabilis is commonly associated with complicated UTI and expresses several virulence factors, including MR/P fimbriae. In the present study mice were immunised nasally with MrpA, the structural subunit of MR/P, with or without CT as a mucosal adjuvant. The animals were then challenged with P. mirabilis and induction of specific serum and urine IgG and IgA, IFN-γ production and bacterial kidney and bladder colonization were assessed. MrpA-immunised mice exhibited significant induction of serum IgA and urine IgA and IgG. MrpA/CT-immunised mice showed both significant serum and urine IgA and IgG production. Only this group showed significant IFN-γ production. Both groups of animals had significant decrease in bacterial colonization of kidneys but not of bladders. No correlation between specific antibody induction in serum and CFU decrease was observed in any group of animals. Our results suggest that a mucosal adjuvant (CT) in the urinary tract enhanced humoral and cytokine response although it did not influence the degree of protection against UTI provided by MrpA. Further studies are necessary to understand immune modulation in the urinary tract.