Vaccine against dental caries--a personal view

Glycan recognition at the saliva - oral microbiome interface

The mouth is a first critical interface where most potentially harmful substances or pathogens contact the host environment. Adaptive and innate immune defense mechanisms are established there to inactivate or eliminate pathogenic microbes that traverse the oral environment on the way to their target organs and tissues. Protein and glycoprotein components of saliva play a particularly important role in modulating the oral microbiota and helping with the clearance of pathogens. It has long been acknowledged that glycobiological and glycoimmunological aspects play a pivotal role in oral host-microbe, microbe-host, and microbe-microbe interactions in the mouth. In this review, we aim to delineate how glycan-mediated host defense mechanisms in the oral cavity support human health. We will describe the role of glycans attached to large molecular size salivary glycoproteins which act as a first line of primordial host defense in the human mouth. We will further discuss how glycan recognition contributes to both colonization and clearance of oral microbes.

In situ and non-invasive detection of specific bacterial species in oral biofilms using fluorescently labeled monoclonal antibodies

Noninvasive in situ detection of suspected cariogenic bacterial species within dental biofilms could facilitate monitoring of the dynamic change of oral microbial flora and assist in the assessment of the treatment efficacy of therapeutic agents. In this study, we explore the possibility to use three well-characterized monoclonal antibodies (MAbs) against Streptococcus mutans, Actinomyces naeslundii, and Lactobacillus casei to identify these three important members of the oral microbial community in the complex environment of oral biofilms. These MAbs, which were conjugated to different fluorescent labels and visualized with confocal laser scanning microscopy (CLSM), proved to be an useful tool to identify the three species of interest (S. mutans, A. naeslundii, and L. casei) under various experimental conditions including in vitro and in vivo derived oral biofilms. Manifold addition of the MAbs on consecutive days did not alter the biofilm structure thus allowing monitoring of the same biofilm over extended time periods. Using this MAb-based method the effect of sucrose challenge on the biofilm composition and the distribution of S. mutans, A. naeslundii, and L. casei were examined. S. mutans was found to be the predominant species under the various biofilm conditions tested. These studies indicate that MAbs based bacterial detection with CLSM is a versatile tool which permits new insights into the ecology of oral biofilm development.

Do we need to be concerned about dental caries in the coming millennium?

Dental caries continues to be a pubic health problem despite claims that 50% of schoolchildren are caries-free. There are widespread variations in the prevalence of caries worldwide. Caries lesions are the clinical manifestation of a pathogenic process that may have been occurring on the tooth surface for months or years. Acid production by bacteria embedded in a biofilm termed "dental plaque" is a key aspect of the pathogenesis of dental caries; nevertheless, the ability of micro-organisms to survive in a hostile acid milieu and the influence of fluoride and additional agents on this acid tolerance receive scant attention. Study of cariogenic micro-organisms largely has been limited to observations made on them in the planktonic state; clearly dental caries is essentially a surface phenomenon, and micro-organisms behave distinctively when grown on a surface. Although significant progress has been made in our understanding of the etiology, pathogenesis, and prevention of dental caries, it still remains a scientific and clinical enigma worthy of the attention of the best scientists.

Extracellular polysaccharides do not inhibit the reaction between Streptococcus mutans and its specific immunoglobulin G (IgG) or penetration of the IgG through S. mutans biofilm

The present study investigated whether extracellular polysaccharides inhibit reaction between Streptococcus mutans and its specific immunoglobulin G (IgG) and penetration of the IgG through S. mutans biofilm. The planktonic organisms with or without extracellular polysaccharides were prepared, incubated with rabbit IgG against whole cell of S. mutans and fluorescein isothiocyanate (FITC)-conjugated goat affinity purified antibody to rabbit IgG. Biofilms with or without extracellular polysaccharides were formed on cover glasses and incubated with rabbit IgG against S. mutans and FITC-conjugated goat antibody to rabbit IgG. Then, biofilms were stained with propidium iodide. The amount of specific IgG binding on S. mutans was determined by FITC intensity with a fluorescence microplate reader. The penetration of IgG through biofilms was determined by confocal laser scanning microscopy. The results showed that the fluorescence intensity of FITC in planktonic organisms with extracellular polysaccharides was similar to that in planktonic organisms without extracellular polysaccharides, indicating that extracellular polysaccharides did not inhibit the reaction between S. mutans and its specific IgG. Although biofilms of S. mutans with extracellular polysaccharides were much thicker and denser than those without extracellular polysaccharides, the speed with which IgG penetrated through both of the biofilms did not differ significantly, suggesting that penetration of IgG through S. mutans biofilm was not affected by extracellular polysaccharides.

Effects of antibodies to glucosyltransferase on soluble and insolubilized enzymes

OBJECTIVE

Previous studies have shown that glucosyltransferase enzymes (Gtfs) of Streptococcus mutans adsorbed to saliva coated hydroxyapatite (sHA) have distinct properties from the same enzymes in solution. The purpose of the present study was to determine the effects on enzyme activity of polyclonal antibodies raised to Gtfs in a soluble form and bound to sHA.

MATERIALS AND METHODS

Antiserum was raised in six New Zealand White rabbits using the purified glucosyltransferase enzymes (Gtfs) of S. mutans, GtfB, GtfC, or GtfD as soluble antigens or adsorbed to hydroxyapatite (HA, insolubilized). The antisera were examined for their ability to react to these Gtfs and Gtf from Streptococcus sanguis (GtfSs) in Western blot formats as well as inhibit enzyme activity in solution and insolubilized.

RESULTS

Antibodies raised against GtfB or GtfC detected all Gtf enzymes examined in Western blots; antibodies raised to GtfD reacted strongly to GtfD and GtfSs, poorly to GtfC, and was non-reactive with GtfB. Antibodies to GtfB or GtfC inhibited activity of GtfB and GtfC in solution by 90% or more. Enzyme activity adsorbed to sHA was inhibited from 70% to 80% by the same antisera. These same antibodies possessed no specific effect on the activities of either GtfD or GtfSs. Antibodies raised to the GtfD enzyme inhibited activity of GtfD (80% to 90% inhibition) and GtfSs activity (50% to 80%) in solution. In contrast the GtfD antibodies had no effect on the activity of either GtfB or GtfC enzymes in solution. Modest inhibitory effects were noted on GtfC and GtfSs enzymes bound to sHA, but no inhibition was observed for sHA-bound GtfB or GtfD.

CONCLUSION

These data show that some antibodies effective against enzymes in solution may have significantly lesser inhibitory effects against the same enzymes insolubilized. Further, presentation of Gtf antigen immobilized to HA has only a minor influence on the production of antibodies inhibitory to Gtf activity.

Caries prevention: current strategies, new directions

Despite major advances in caries prevention, a large subset of the U.S. population still needs additional control measures. In numerous other countries, needs are escalating as caries rates continue to rise. Building on current strategies and new insights into the specific mechanisms of caries initiation, researchers are creatively using a variety of new technologies, especially in molecular biology, to fashion a new generation of preventive measures.