Salivary Control of Oral Microflora

Abstract Body: Saliva plays many varied roles in the defence of the oral cavity. Certain proteins and peptides in saliva function directly as general antimicrobial agents. These include lysozyme, lactoferrin, and lactoperoxidase as well as cationic antimicrobial peptides such as salivary histatins and defensins. A more specific recognition of microorganisms is provided by components of the acquired immune system present in saliva, predominantly secretory immunoglobulin A, and to a lesser degree other classes of immunoglobulins. Most of the major highly abundant salivary proteins act as modulators of the oral microbiota. On the one hand, salivary proteins serve as growth substrates and attachment sites for oral microorganisms leading under physiological conditions to the colonization of oral surfaces by a beneficial microflora. On the other hand, they can act as scavenger molecules by agglutinating planktonic microorganisms, thereby leading to their elimination from the oral cavity. This presentation will review the various ways by which salivary proteins interact with oral microorganisms. Particular emphasis will be placed on mechanisms of glycan-mediated binding of oral commensal bacteria and systemic pathogens to salivary glycoproteins. The findings presented here support the role of saliva as a gate keeper for microbes at the entrance to gastro-intestinal and respiratory tracts. Saliva maintains a balance by retaining a beneficial resident microflora in the oral cavity and at the same time eliminating potential pathogens that traverse the oral environment. Insight into the basic molecular mechanisms of bacterial adhesion may open up new avenues to prevent and control oral and systemic diseases associated with the pathogenic colonisation of host surfaces.Funding: NIDCR grant R01DE019807 (SR)