Evaluation of the immune response elicited by multi-antigenic DNA vaccine expressing SAG1, ROP2 and GRA2 against Toxoplasma gondii.

The parasite Toxoplasma gondii can infect most mammals and birds, sometimes causing severe pathology. Previous studies have reported that multi-antigenic vaccines were more effective than single-antigenic vaccine. It was also reported that the a single-gene vaccine with SAG1 or ROP2, GRA2 could only produce partial protection against T. gondii. In this study, we constructed a multi-antigenic DNA vaccine containing SAG1, ROP2 and GRA2, and evaluated its immune response. We used IL-12 as an adjuvant to enhance the immune response. We immunized BALB/c mice intramuscularly. After immunization, we evaluated the immune response using lymphocyte proliferation assay, cytokine and antibody measurements. The results showed that the group immunized with pcDNA3.1-SAG1-ROP2-GRA2 produced high Th1 immune response compared to other groups immunized with double-gene plasmid, empty plasmid or phosphate-buffered saline, respectively. Moreover, the co-immunization with IL-12 genes enhanced the immune response significantly and prolonged survival time. The current study showed that multi-antigenic DNA with IL-12 produced potent, effective and long-term protection against T. gondii challenge.