Abstract
This study seeks to assess the efficacy of the glucosyltransferase-I (GTF-I) produced by Streptococcus sobrinus as a nasal vaccine for the prevention of dental caries. Nasal immunization of mice with GTF-I elicited significant levels of GTF-I-specific IgG and IgA in serum and mucosal IgA antibodies in saliva. Antibody-forming cell analysis confirmed the antibody titers by detecting high numbers of GTF-I-specific antibody-forming cells in spleen and salivary glands. Coadministration of GTF-I and oligodeoxynucleotides (ODN) containing unmethylated cytosine-phosphate-guanine (CpG) dinucleotides (CpG ODN) as adjuvant further elevated salivary IgA antibody responses; however, the increase in serum antibody levels was slight. GTF-I-specific IgG antibodies from mice given GTF-I alone or GTF-I plus CpG ODN inhibited biofilm formation by S. sobrinus. Finally, the mice given nasal GTF-I showed protection and significant inhibition of dental caries caused by oral infection with S. sobrinus even without the use of CpG ODN. These results suggest that nasal administration of GTF-I could be an important tool for the prevention of dental caries.
Highlights
Dental caries is a chronic infectious disease caused by the formation of biofilm on tooth surfaces
Since mucosal administration of CpG ODN with protein antigen have proven to be an effective regimen for the induction of antigen-specific antibody responses [18,19], we examined the effect of the nasal administration of CpG ODN as adjuvant on GTF-I-specific antibody responses
A previous study has shown that specific antibodies induced by a fusion protein consisting of alanine-rich region of surface protein antigen (PAg) and GTF-I produced by S. sobrinus suppress sucrose-dependent and -independent adhesion of both S. sobrinus and S. mutans [27]
Summary
Dental caries is a chronic infectious disease caused by the formation of biofilm on tooth surfaces. Mutans streptococci are considered to be causative agents of dental caries [1]. Streptococcus sobrinus as well as S. mutans are major pathogens of dental caries [2]. Both bacteria produce water-soluble and water-insoluble glucans from sucrose, by the combined action of glucosyltransferases [1,2]. The synthesis of the water-insoluble glucan is necessary for the accumulation of these cells on the tooth surface and the induction of dental caries [3,4]. The activities of GTF-I are mediated through both catalytic and glucan-binding functions [8,9]
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