GLUCOSYLTRANSFERASE MEDIATES ADHESION OF STREPTOCOCCUS-GORDONII TO HUMAN ENDOTHELIAL-CELLS IN-VITRO

Human umbilical vein endothelial cells (HUVEC) were used as an experim ental host model to investigate the mechanism(s) of streptococcal adhe sion in infective endocarditis. Adhesion activity of Streptococcus gor donii was maximal during the logarithmic phase of growth and was great ly reduced or eliminated by pretreatment of bacteria with heat, formal dehyde, or trypsin. At saturating numbers of streptococci, an average of 81 bacteria were bound per HUVEC. Streptococcal adhesion was inhibi ted by low-molecular-weight dextran and heparin but not by sucrose, fi bronectin, or laminin. Adhesion was also prevented by pretreatment of HUVEC with proteins dissociated from the surface of S. gordonii with 1 0 mM EDTA or isolated from spent culture medium. Western blot (immunob lot) assays detected a single adhesin protein of 153 kDa (AP153) on HU VEC after incubation with unfractionated extracts of streptococci. The adhesin exhibited glucosyltransferase (GTF) activity when incubated w ith sucrose and Triton X-100 after sodium dodecyl sulfate-polyacrylami de gel electrophoresis. The AP153 was purified by affinity chromatogra phy on dextran beads and shown to have binding activity for HUVEC, GTF activity, an amino acid composition similar to that reported for GTF of S. gordonii, and the ability to inhibit S. gordonii adhesion. Incub ation of the streptococci with antibodies to the adhesin inhibited bac terial attachment to HUVEC monolayers. These results indicate that sur face-localized GTF mediates adhesion of S. gordonii to HUVEC in vitro and may serve as a mechanism for colonization of the endocardium in in fective endocarditis.