[ODP-168] Streptococcus sobrinus誘発性う蝕の抑制におけるIgA抗体の役割
Streptococcus sobrinus is one of major pathogens of dental caries in human. On the other hand, secretory IgA (SIgA) antibodies (Abs) play key roles in protection against exogenous bacterial infection. Our previous study showed that nasal S. sobrinus glucosyltransferase-I reduced dental caries in adult mice. However, the roles of pathogen-specific salivary SIgA Abs and IgG Abs derived from gingival crevicular fluid in suppression of dental caries remain unclear. Thus, we explored the roles of S. sobrinus-specific Abs by employing IgA knockout (KO) mice. Ten-week-old IgA KO and wild-type mice were given cariogenic diet and were orally challenged with 109 CFU of streptomycin-resistant S. sobrinus 6715 on 4 consecutive days. Sixty days after the first gavage, the mandibles were removed and S. sobrinus colonization and caries development as well as antigen-specific Ab responses were assessed.Our results showed that S. sobrinus colonized the mandibles from IgA KO but not wild-type mice. Also, dental caries was developed in S. sobrinus-infected IgA KO mice. In contrast, IgA KO and wild-type mice given PBS and S. sobrinus-infected wild-type mice displayed fewer caries lesions. S. sobrinus-specific IgA Abs were slightly induced in saliva from wild-type mice. These results suggest that S. sobrinus-specific salivary IgA play protective role against dental caries caused by the bacteria.