DNA immune responses induced by codelivery of IL-12 expression vectors with hepatitis C structural antigens

Objective: To demonstrate the utility of DNA vaccines for the tailored methods, the efficacy of enhanced immune responses, and the types of increased immune responses. Methods: Four recombinant plasmids constructed included the coding regions for the core protein (pC) and for the core, E₁ and E₂ together (pCE₁E₂), IL-12 p35 and p40. These plasmids were transfected into mammalian cells to test their protein expression and were injected into the quadriceps muscles of BALB/ C mice for measurement of specific antibodies and cytotoxic T-lymphocyte (CTL) responses. Results: All the recombinant plasmids were shown to express specific antigens stably in mammalian cells. Codelivery of pIL-12 expression cassettes with pC and pCE₁E₂ in mice resulted in the enhancement of Ag-dependent CTL responses and the reduction of specific Ab response. The CTL activity was: pC = 18.65% ± 5.71%, pCE₁E₂ = 20.07% ± 11.11%, pC + pIL-12 = 60.11% ± 17.37%, pCE₁E₂ + pIL-12 = 67.48% ± 15.57%, respectively. The average A values of anti-HCV were pC = 0.415 ± 0.127, pCE₁E₂ = 0.358 ± 0.096, pC + pIL-12 = 0.210 ± 0.086, pCE₁E₂ + pIL-12 = 0.258 ± 0.125. Conclusion: Codelivery of pIL-12 with plasmid DNA can enhance the efficacy of immune responses and shift the type of immune responses.