M. Vanraamsdonk et al., EFFECT OF POLYCLONAL AND MONOCLONAL-ANTIBODIES ON SURFACE-PROPERTIES OF STREPTOCOCCUS-SOBRINUS, Infection and immunity, 63(5), 1995, pp. 1698-1702
In this study, the effect of antibody adsorption on physicochemical pr
operties of Streptococcus sobrinus was studied. Bacteria were preincub
ated with polyclonal antibodies or with OMVU10, a monoclonal antibody
(MAb) reactive with S. sobrinus. The zeta potentials and the hydrophob
icity as determined by microbial adhesion to hydrocarbons were measure
d in potassium phosphate buffer with a pH ranging from 2 to 9, S. sobr
inus preincubated with polyclonal antibodies was positively charged at
pH 2, 3, and 4 and had an isoelectric point at pH 4.8. Untreated S. s
obrinus cells or cells preincubated with MAbs were negatively charged
over the whole pH range. X-ray photoelectron spectroscopy showed a dec
rease 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 compositi
on of the cell surface suggests that polyclonal antibody adsorption oc
curs through blocking of surface phosphate. The measurement of hydroph
obicity by microbial adhesion to hydrocarbons revealed that S. sobrinu
s preincubated with polyclonal antibodies was hydrophobic (90% of the
bacteria bound to hexadecane), whereas the controls were relatively hy
drophilic. S. sobrinus preincubated with OMVU10 was found to be more h
ydrophobic than the controls at pH 5 and 7. Hydrophobicity as measured
by water contact angles shelved an increase in hydrophohicity when S.
sobrinus was preincubated with polyclonal antibodies. The epitopes to
which the antibodies are directed were visualized by immunogold label
ing and electron microscopy. The results suggested that OMVU10 is reac
tive 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 overa
ll physicochemical surface properties of the organism, probably by for
ming a coating over the whole cell surface. Adsorption of MAbs was mor
e localized, which could explain their lesser influence on these surfa
ce properties.