Co-delivery of cc119 gene enhances anti-caries DNA vaccine pCIA-P immunogenicity in mice by increasing dendritic cell migration to secondary lymphoid tissues

Aim： To investigate how co-delivery of the gene encoding C-C chemokine ligand-19 （CCL-19） affected the systemic immune responses to an anti-caries DNA vaccine pClA-P in mice. Methods： Plasmid encoding CCL19-GFP fusion protein （pCCL19/GFP） was constructed by inserting murine cc119 gene into GFP- expressing vector pAcGFP1-NI. Chemotactic effect of the fusion protein on murine dendritic cells （DCs） was assessed in vitro and in vivo using transwell and flow cytometric analysis, respectively. BALB/c mice were administered anti-caries DNA vaccine pClA-P plus pCCL19/GFP （each 100 pg, im） or pClA-P alone. Serum level of anti-PAc IgG was assessed with ELISA. Splenocytes from the mice were stimulated with PAc protein for 48 h, and IFN-~ and IL-4 production was measured with ELISA. The presence of pCCL19/GFP in spleen and draining lymph nodes was assessed using PCR. The expression of pCCL19/GFP protein in these tissues was analyzed under microscope and with flow cytometry. Results： The expression level of CCL19-GFP fusion protein was considerably increased 48 h after transfection of COS-7 cells with pCCL19/GFP plasmids. The fusion protein showed potent chemotactic activity on DCs in vitro. The level of serum PAc-specific IgG was significantly increased from 4 to 14 weeks in the mice vaccinated with pClA-P plus pCCL19/GFP. Compared to mice vaccinated with pClA-P alone, the splenocytes from mice vaccinated with pClA-P plus pCCL19/GFP produced significantly higher level of IFN-y, but IL-4 production had no significant change. Following intromuscular co-delivery, pCCL19/GFP plasmid and fusion protein were detected in the spleen and draining lymph nodes. Administration of CCL19 gene in mice markedly increased the number of mature DCs in second- ary lymphoid tissues. Conclusion： CCL19 serves as an effective adjuvant for anti-caries DNA vaccine by inducing chemotactic migration of DCs to secondary lymphoid tissues.