Purified P fimbriae from two cloned gene clusters of a single pyelonephritogenic strain adhere to unique structures in the human kidney

We have completed immunofluorescence binding studies of purified fimbriae from two clones which express Pap or Pap-2 fimbriae. Although the two fimbrial types exhibited common binding to the uroepithelia of the bladder and renal pelvis and to occasional cells located within the glomeruli which we have termed glomerular elements, only Pap-2 fimbriae adhered to Bowman's capsule. Previous studies have demonstrated that the Galα1→4Gal disaccharide moiety is capable of inhibiting Pap hemagglutination and adherence to uroepithelial cells. Results of our experiments demonstrate that this disaccharide is not sufficient for blocking binding of Pap-2 fimbriae to Bowman's capsule but that GalNAcβ1→3Gal completely blocks Pap-2 adherence to Bowman's capsule. These results indicate that the different hemagglutination capacities of the two clones reflect different receptor specificities and differential tissue tropisms in the urinary tract. These unique receptor specificities may provide uropathogenic strains of Escherichia coli carrying multiple chromosomal copies of pap-like gene clusters with the advantage of increased numbers of binding sites within the urinary tract. This, in turn, might improve the chances of colonization and the establishment of infection.