Bacterial binding to salivary proteins may in part account for individual differences in the colonization of tooth surfaces. High-molecular-weight glycoproteins, agglutinins, mediate S. mutans adherence, whereas acidic proline-rich proteins mediate adherence of other early-colonizing streptococci and Actinomyces. The aim of the present study was to examine the composition of adherence-related salivary proteins and dental plaque micro-organisms in three individuals with a low, moderate, and high capacity to mediate S. mutans adherence. The S. mutans (strain Ingbritt) binding activity resided with a 300-kDa agglutinin which was six-fold more prevalent in the high S. mutans binding saliva compared with the low one. Binding to all three salivas was completely blocked by a monoclonal anti-agglutinin antibody. The moderate S. mutans binding saliva was found to contain adherence-inhibiting components. Furthermore, the low and moderate S. mutans binding salivas mediated binding of A. naeslundii strain LY7 to a greater extent than the saliva with high S. mutans binding. The A. naeslundii binding activity resided with the acidic proline-rich proteins (APRPs) and paralleled the relative content of 106- and 150-residue APRPs. Low A. naeslundii binding coincided with an almost two-fold higher ratio of 106/150 APRPs compared with the high A. naeslundii binding saliva. During conventional gel filtration, a degradation of the acidic, basic, and glycosylated proline-rich proteins was evident in the saliva with high S. mutans and low A. naeslundii binding. This saliva donor had a comparably high rate of dental plaque formation, high counts of S. mutans, and low counts of other streptococci and Actinomyces.

Tryptic digestion of the 150-residue human acidic salivary proline-rich protein 1 (PRP-1) generated eight peptides, two of which corresponded to the N-terminal 30-residue segment. In each of the other six tryptic peptides, a consensus repeat with the structure PQGPPQQGG was present. A facile Gln-Gly cleavage between the second and the third residues of the repeat was observed during collision-induced dissociation experiments. We postulate possible mechanisms to account for this reactivity, involving attack on the peptidyl carbonyl group by the Gln sidechain. Significantly, the Gln-Gly cleavage has been shown to be biologically important in the bacterial degradation of PRPs in saliva, generating bacteria-binding Pro-Gln C-termini. We suggest a link between the gas-phase chemistry and the biochemical degradation of these molecules.

This study suggests degradation of salivary acidic proline-rich proteins (PRPs) into potential innateimmunity-like peptides by oralThe acidic proline-rich proteins (PRPs), encoded by the PRH1 and PRH2 loci on chromosome 12p13.2 (4), are major saliva proteins (15). As polymorphic and multifunctional proteins (4, 15, 20), they are potential determinants of host susceptibility to dental caries (23,24).Acidic PRPs adsorb to hydroxyapatite surfaces, regulate calcium phosphate and hydroxyapatite crystal equilibrium (15), attach commensal Actinomyces and Streptococcus species to teeth (13, 21), and inactivate ingested plant polyphenols (tannins) (5). While the proline-poor N-terminal 30-residue domain confers hydroxyapatite and calcium binding (15), the proline-rich middle/C-terminal domain binds tannins via prolinerich repeats (5) and bacteria via the ProGln terminus (13, 21).Acidic PRPs consists of large allelic (e.g., PRP-1 and PIF-s) and small posttranslational (e.g., PRP-3 and PIF-f) variants (4). The small acidic PRPs resulting from proteolytic cleavage at Arg 106 -Gly 107 display poor bacterial adhesion activities but high affinities for hydroxyapatite surfaces (15).After secretion, the acidic PRPs are rapidly enriched on tooth surfaces and degraded into potential innate-immunity peptides by dental plaque proteolysis (22). Both gram-negative and gram-positive bacteria display complex profiles of glycosidases and proteases, but little is known about turnover of acidic PRPs by commensal and early-colonizing Streptococcus and Actinomyces species (8). In this study, we used mass spectrometry of peptide mixtures to suggest turnover of acidic PRPs into innate-immunity-like peptides by commensal Streptococcus and Actinomyces species.PRP-1 and PRP-3 were purified from parotid saliva of three subjects homozygous for PRP-1 and PIF-s by DEAE-Sephacel column chromatography (15 by 1.6 cm; Pharmacia, Uppsala, Sweden) using a linear gradient of 25 to 1,000 mmol of NaCl/ liter in 50 mmol of Tris-HCl/liter (pH 8.0). The acidic PRP fractions were then concentrated (Centriprep 10 concentrator; Amicon Inc., Beverly, Mass.) and separated by gel filtration (HiLoad 26/60 Superdex S-200 prep-grade column; Pharmacia) in Tris-HCl (20 mmol/liter)-NaCl (500 mmol/liter), pH

The aim of the present study was to identify salivary molecules affecting adhesion of Candida albicans and Candida krusei to salivary pellicles and epithelial cells. Strains of C. albicans (GDH18, GDH3339, CA1957, ATCC 28366 and ATCC 10321), but not C. krusei (strains ATCC 14243 and Ck9), bound to saliva-coated hydroxyapatite and buccal epithelial cells. Parotid saliva fractions containing statherin, glycosylated proline-rich proteins (PRP) and as yet unidentified components mediated adhesion of strain GDH18; Fuc alpha 1-2Gal beta 1-4Glc partly inhibited the adhesion to those fractions not containing statherin. Pure statherin, but not PRP-1, mediated dose-dependent adhesion of C. albicans strain GDH18 to hydroxyapatite beads. Candida isolates (GDH18, GDH3339 and CA1957) bound somewhat more avidly to statherin/saliva relative to ATCC strains 28366 and 10321, while the opposite was true for adhesion to buccal epithelial cells. Adhesion of C. albicans strain GDH18 to saliva-coated hydroxyapatite and buccal epithelial cells was completely (93%) and partly (43%) blocked by statherin-specific immunoglobulin G (IgG) antibodies, respectively. Control IgG antibodies did not block Candida adhesion. Blockage of Candida adhesion to epithelial cells also occurred with Fuc alpha 1-2Gal beta 1-4Glc (49%) and N-acetylglucosamine (38%), while statherin specific IgG antibodies in combination with Fuc alpha 1-2Gal beta 1-4Glc almost completely eliminated Candida adhesion (79%). In addition, statherin in solution blocked the adhesion of strain GDH18 to epithelial cells by inducing aggregation of Candida cells.

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