Intranasal co-delivery of IL-6 gene enhances the immunogenicity of anti-caries DNA vaccine.

AIM

To investigate the effects of co-delivering IL-6 expressing plasmid pCI-IL-6 on the immunogenicity of the anti-caries DNA vaccine pCIA-P, which encodes the surface protein antigen PAc of Streptococcus mutans.

METHODS

Plasmid pCI-IL-6 was constructed by inserting the murine IL-6 gene into the pCI vector. Expression of IL-6 in vitro was assessed using Western blot analysis. BALB/c mice were intranasally co-immunized with pCIA-P plus pCI-IL-6 on d 0 and 14. Anti-PAc IgG and secretory IgA (sIgA) were assessed by ELISA. Splenocytes from the mice were re-stimulated with the PAc protein, and IFN-γ and IL-4 production was measured using ELISA. Splenocyte proliferation was analyzed with flow cytometry. Rats were similarly immunized, and dental caries scores were determined using the Keyes method.

RESULTS

Marked expression of IL-6 was found in COS-7 cells transfected with pCI-IL-6. In the pCI-IL-6 co-immunized mice, the specific IgG antibodies in serum and sIgA antibodies in saliva were significantly higher than those in the control mice at weeks 4 and 8. Moreover, the secretion of IFN-γ from splenocytes in response to re-stimulation with PAc protein was significantly higher in the pCI-IL-6 co-immunized mice than that in the control mice, whereas the secretion of IL-4 had no significant difference. The proliferation of splenocytes from the pCI-IL-6 co-immunized mice was significantly higher than that from the mice immunized with pCIA-P and pCI vector. In the rat caries model, the pCI-IL-6 co-immunization rats displayed lower caries scores than the control rats.

CONCLUSION

Intranasal co-delivery of IL-6 gene significantly enhances the immunogenicity of the anti-caries DNA vaccine.