Figure 5

Flagellin- and rPAc-specific antibody responses and therapeutic effect of KFD2-rPAc against caries in rats. To analyze the therapeutic effect of KFD2-rPAc against caries, the rats were immunized after caries were established. Rats were fed antibiotics and challenged with S. mutans Ingbritt. The day on which the rats completed the challenge was set as d 0 (d 0). Fifty-six days after implanting S. mutans, all of the rats developed E and Ds lesions. Rats were then randomly divided into 5 groups (6 per group): control, PBS, rPAc, KF-rPAc, and KFD2-rPAc. At d 56, the control group was killed and set as the caries baseline, while the other groups were intranasally immunized with PBS, 5 μg of rPAc, 8.5 μg of KF-rPAc, or 7 μg of KFD2-rPAc in a 10-μl aliquot, and boosted on d 84 and d 112, respectively. The serum and the saliva were collected on d 126 and analyzed for flagellin- or rPAc-specific antibody responses by enzyme-linked immunosorbent assay. On d 140, the rats were killed and the caries levels were scored by the Keyes method. (a) Challenge, immunization, and sampling schedule of rats. (b) Flagellin-specific serum IgG, serum IgA, and saliva IgA responses in immunized rats. (c) rPAc-specific serum IgG, serum IgA, and saliva IgA responses in immunized rats. (d) Representative photographs of caries lesion for each group. E, Ds, Dm, and Dx lesions are indicated by a green arrow, red arrow, purple arrow, and black arrow, respectively. (e) Caries scores of enamel (E), slight dentinal (Ds), moderate dentinal (Dm), and extensive dentinal (Dx) lesions of rats immunized with different immunogens. (f) Total caries score of different groups were determined: (total score = score of E + Ds + Dm + Dx). (g) The inhibition ratio of dental caries by immunization of different immunogens. *p < 0.05; **p < 0.01; and ***p < 0.001; n.s., non-significant. n.o., not observed.