Comparison of cholera toxin A2/B and murine interleukin-12 as adjuvants of Toxoplasma multi-antigenic SAG1-ROP2 DNA vaccine

Toxoplasmosis can lead to severe pathology in both humans and animals. However, an effective vaccine for humans has not been successfully developed. In this study, we used multi-antigenic SAG1-ROP2 as a DNA vaccine and cholera toxin A2/B subunit and murine interleukin-12 to compare their effectiveness as genetic adjuvants. Bagg albino/c (BAL/c) mice were immunized intramuscularly with pcDNA3.1-SAG1-ROP2 alone (control group), or pcDNA3.1-SAG1-ROP2 with co-administration of pCTA2/B or pIL-12, respectively. After immunization, the effectiveness of these two adjuvants were compared using lymphocyte proliferation assay, cytokine and antibody measurements. The group co-administered pIL-12 elicited stronger humoral and Th1-type cellular immune responses than those immunized with pcDNA3.1-SAG1-ROP2 alone, while in the group co-administered pCTA2/B there was no obvious enhancement of immunity. When challenged with Toxoplasma gondii RH strain, mice immunized with pIL-12 co-administration had significantly higher survival rates, whereas there was no notable augmentation of immunity in pCTA2/B group. Therefore, since pIL-12 significantly enhanced the antigenicity of multi-antigenic DNA vaccine, this suggests that IL-12 is a better and more effective adjuvant than CTA2/B in this situation.