Immune response induced in mice by codelivery of interleukin-18 recombinant and HBV S gene DNA vaccine

Objective To investigate the effect of interleukin 18(IL 18)on immune response induced by plasmid encoding hepatitis B virus surface antigen and to explore new strategies for prophylactic and therapeutic HBV DNA vaccines. Methods Balb/c mice were immunized with pcDNA3 S alone or co immunized with pcDNA3 18 and pcDNA3 S.Their sera were collected for analyzing anti HBsAg antibody by ELISA and splenocytes were isolated for defecting specific CTL response. HBsAg specific lymphocyte proliferation test and specific cytokine level were also assayed in vitro . Results The anti HBsAg antibody level of mice co immunized with pcDNA3 18 and pcDNA3 S was slightly higher than that of mice immunized with pcDNA3 S alone, but there was no significant difference (P 0.05). Compared with mice injected with pcDNA3 S alone, the specific CTL cytotoxity activity of mice immunized with pcDNA3 18 and pcDNA3 S was significantly enhanced ( P 0.05) and the level of IFN γ in supernatant of splenocytes cultured with HBsAg in vitro was significantly elevated ( P 0.05) while the level of IL 4 did not change significantly ( P 0.05). The stimulatory index (SI) of splenocytes stimulated with HBsAg in co immunized group was slightly elevated compared with mice immunized with pcDNA3 S alone,but therewas no significant difference( P 0.05). Conclusions The plasmid encoding IL 18 together with HBV S gene DNA vaccines may enhance specific TH1 cells and CTL cellular immune response elicited in mice, hence IL 18 is a promising immune adjuvant.