Nasal administration of glucosyltransferase-I of Streptococcus sobrinus without adjuvant induces protective immunity

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.