Modulation of the Immune Response to DNA Vaccine Encoding Gene of 8-kDa Subunit of Echinococcus granulosus Antigen B Using Murine Interleukin-12 Plasmid in BALB/c Mice

Background: The current study was designed to evaluate immune responses induced by DNA vaccines encoding 8-kDa subunit of antigen B (HydI) of Echinococcus granulosus and murine interleukin 12 (IL-12) as genetic adjuvants in BALB/c mice.

Methods: Expression plasmid pcDNA3.1 containing HydI (pcHyd1) as vaccine along with the murine interleukin 12 (pcMIL12) as adjuvant were used. Thirty-five mice in the five experimental groups received PBS, empty pcDNA3.1, pcHydІ, pcMIL-12, and pcHydІ+ pcMIL-12 in days zero, 14^th and 28^th. Two weeks after the last immunization, evaluation of the immune response was performed by evaluating the proliferation of splenic lymphocytes, IFN-γ and IL-4, determination of IgG isotyping titer.

Results: Mice that received the pcHydI+pcMIL12 exhibited higher levels of lymphocyte proliferation compared to mice that received the pcHydI alone (P<0.001), and produced significantly more IFN-γ in comparison to other groups (P< 0.001). In addition, they produced significantly less IL-4 than mice receiving the PBS and the empty plasmid (P<0.023). The IgG2a levels were clearly higher in pcHydI+pcMIL12 group in comparison with the groups of pcHydI alone, empty plasmid, and PBS. In contrast, IgG1 was elevated in the group of pcHydI.

Conclusion: Co-delivery of IL-12 with DNA encoding 8-kDa subunit of antigen B was effective significantly in inducing the immune response in mice.