Receptors for Escherichia coli Adhesins in the Genitourinary Tract in a Non-human Primate

Objective: To study the expression of receptors allowing adhesin-mediated binding of Escherichia coli to urogenital tissues ranging from the kidney to the vagina in cynomolgus monkeys using an in situ assay. Material and Methods: Receptors specific for four relevant adhesins were investigated: PapG and PrsG of P-fimbriae binding to gal-α(1-4)gal glycosphingolipids (preferentially globoside and the Forssman antigen respectively); and two variants of FimH of type 1 fimbriae, one binding to monomannose/trimannose and the other to trimannose only. To ascertain the specificity of the observed bindings we used adhesion inhibition by receptor analogues as well as E. coli adhesin knockout mutants. Results: The distributions of PapG and FimH receptors in monkey tissues showed great similarities to available data in humans. Whilst monomannose receptors were expressed on the surface epithelium in both the monkey bladder and ureter, trimannose receptors were not. The different distribution of FimH isoreceptors and the heterogeneity of FimH adhesin variants among E. coli may explain contradictory earlier findings in type 1 fimbriae-mediated adhesion to the human bladder and to renal tissues. We also found evidence of a hitherto unknown type of host-aggressor interaction on vaginal and urethral mucosa, which was not discovered until type 1 fimbriae had been eliminated. Conclusions: A precise molecular fit between host receptors and bacterial lectins is important in infectious pathogenesis. We conclude that urinary tract infection in the cynomolgus monkey is a relevant model of the human disease because of the similarity in the expression of receptors for E. coli adhesins on epithelial surfaces in the two species.