title: Effect of polyclonal and monoclonal antibodies on surface properties of Streptococcus sobrinus.
abstract: In this study, the effect of antibody adsorption on physicochemical properties of Streptococcus sobrinus was studied. Bacteria were preincubated with polyclonal antibodies or with OMVU10, a monoclonal antibody (MAb) reactive with S. sobrinus. The zeta potentials and the hydrophobicity as determined by microbial adhesion to hydrocarbons were measured in potassium phosphate buffer with a pH ranging from 2 to 9. S. sobrinus preincubated with polyclonal antibodies was positively charged at pH 2, 3, and 4 and had an isoelectric point at pH 4.8. Untreated S. sobrinus cells or cells preincubated with MAbs were negatively charged over the whole pH range. X-ray photoelectron spectroscopy showed a decrease in O/C and P/C ratios for bacteria preincubated with polyclonal antibodies. A combination of the pH-dependent zeta potential and the X-ray photoelectron spectroscopy data of the overall chemical composition of the cell surface suggests that polyclonal antibody adsorption occurs through blocking of surface phosphate. The measurement of hydrophobicity by microbial adhesion to hydrocarbons revealed that S. sobrinus preincubated with polyclonal antibodies was hydrophobic (90% of the bacteria bound to hexadecane), whereas the controls were relatively hydrophilic. S. sobrinus preincubated with OMVU10 was found to be more hydrophobic than the controls at pH 5 and 7. Hydrophobicity as measured by water contact angles showed an increase in hydrophobicity when S. sobrinus was preincubated with polyclonal antibodies. The epitopes to which the antibodies are directed were visualized by immunogold labeling and electron microscopy. The results suggested that OMVU10 is reactive with only a few epitopes of the cell surface, whereas polyclonal antibodies were found to be reactive with many epitopes. In conclusion, adsorption of polyclonal antibodies was found to influence the overall physicochemical surface properties of the organism, probably by forming a coating over the whole cell surface. Adsorption of MAbs was more localized, which could explain their lesser influence on these surface properties.
authors.affiliation: Department of Oral Microbiology, Academic Centre for Dentistry Amsterdam, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: van Raamsdonk
authors.forename: H C
authors.initials: HC
authors.lastname: van der Mei
authors.forename: J J
authors.initials: JJ
authors.lastname: de Soet
authors.forename: H J
authors.initials: HJ
authors.lastname: Busscher
authors.forename: J
authors.initials: J
authors.lastname: de Graaff
mesh_terms: D000327:Adsorption; D000907:Antibodies, Bacterial / Q000494:pharmacology*; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001422:Bacterial Adhesion / Q000502:physiology; D002462:Cell Membrane / Q000737:chemistry; D004577:Electron Probe Microanalysis; D008564:Membrane Potentials; D011485:Protein Binding; D016986:Streptococcus sobrinus / Q000187:drug effects / Q000276:immunology / Q000502:physiology* / Q000648:ultrastructure; D013499:Surface Properties / Q000187:drug effects*
chemical_list: D000907:Antibodies, Bacterial; D000911:Antibodies, Monoclonal