BINDING CHARACTERISTICS OF S-FIMBRIATED ESCHERICHIA-COLI TO ISOLATED BRAIN MICROVASCULAR ENDOTHELIAL-CELLS

To assess the role of S fimbriae in the pathogenesis of Escherichia co li meningitis, transformants of E. coli strains with or without S fimb riae plasmid were compared for their binding to microvessel endothelia l cells isolated from bovine brain cortices (BMEC). The BMEC's display ed a cobblestone appearance, were positive for factor VIII, carbonic a nhydrase IV, took up fluorescent-labeled acetylated low density lipopr otein, and exhibited gamma glutamyl transpeptidase activity. Binding o f S fimbriated E. coli to BMEC was approximately threefold greater tha n nonfimbriated E. coli. Similarly S fimbriated E. coli bound to human brain endothelial cells approximately threefold greater than nonfimbr iated E. coli. Binding was reduced approximately 60% by isolated S fim briae and about 80% by anti-S adhesin antibody. Mutating the S adhesin gene resulted in a complete loss of the binding, whereas mutagenesis of the major S fimbriae subunit gene sfaA did not significantly affect binding. Pretreatment of BMEC with neuraminidase or prior incubation of S fimbriated E. coli with NeuAc alpha 2,3-sialyl lactose completely abolished binding. These findings indicate that S fimbriated E. coli bind to NeuAc alpha 2,3-galactose containing glycoproteins on brain en dothelial cells via a lectin-like activity of SfaS adhesin. This might be an important early step in the penetration of bacteria across the blood-brain barrier in the development of E. coli meningitis. ,