Abstract: PURPOSE: To investigate the efficiency of pcDNA3-PAc on Japanese long-eared white rabbits by intranasal immunization, and observe the appreciate gene vaccine dose in rabbit immunization. METHODS: Thirty Japanese long-eared white rabbits were randomly divided into 5 groups (6 in each group) as follows: 200, 400, 600 μg pcDNA3-PAc plasmid group; 400 μg pcDNA3 group and inactivated whole-cell vaccine positive control group. The rabbits were immunized twice, and plasmid groups and whole-cell group were coupled Freund's adjuvant with 1:1 ratio. The specific IgG and S-IgA antibodies in serum and saliva were detected with indirect ELISA method. The data was analyzed with SPSS 17.0 software package. RESULTS: ① The peak time of the antibodies appeared between 8-10 weeks after the first immunization; ②The specific antibodies IgG and S-IgA could be detected 2 weeks after immunization;③The level of salivary specific S-IgA and serum specific IgG of pcDNA3-PAc were significantly higher than negative groups (P<0.05). The titer of the 200 μg was significantly lower than those of 400 μg and 600 μg group (P<0.05). CONCLUSIONS: ①The recombinant plasmid pcDNA3-PAc has immunogenicity, which can induce specific immune responses for 14 weeks in rabbits. ②The results of the present study show that 200 μg, 400 μg and 600 μg are effective immunizational dosage to 1.5 kg Japanese long-eared white rabbits. ③400 μg and 600 μg pcDNA3-PAc can be considered as the optimal dosage than 200 μg at present experimental condition.

Key words: Gene vaccine, Dental caries, Streptococcus mutans, PAc