Saliva protein binding to streptococcal layers placed at different oral sites in 48 persons

Preliminary studies of 10 subjects suggested that saliva protein binding to oral bacteria might vary among oral sites. This study investigated saliva protein binding to layers of oral streptococci in an expanded sample of 48 subjects. Those persons were at opposite extremes for unstimulated whole saliva amylase, sIgA, lactoferrin, and lysozyme in an initial screening of 128 individuals. Layers of Streptococcus gordonii Blackburn or Streptococcus oralis 10557 on enamel chips were placed on buccal left and right upper premolars and molars (UL, UR), labial upper central incisors (UC), and lingual lower central incisors (LL). After a 10-minute exposure to saliva, bacterial extracts were assayed for bound amylase, sIgA, lactoferrin, and lysozyme. Those proteins also were quantified in unstimulated whole saliva collected after chip exposure. Both strains bound significantly more amylase at UL and UR, and significantly less at UC. Blackburn bound more amylase than 10557 at all sites. Significantly less sIgA was bound at UC; strain differences for sIgA were inconsistent across sites. Significantly more lactoferrin and lysozyme were bound at LL. There were no strain differences for lactoferrin; 10557 bound significantly more lysozyme at UL and UR. Subjects at opposite extremes for saliva protein concentrations differed for bound amylase and lactoferrin; those differences were smaller than site and strain differences. Bound protein levels were correlated across sites and strains. Correlations between whole saliva and bound proteins were moderate and were most consistent at LL. These findings suggest that saliva protein effects on oral ecology may vary among oral sites.