Adjuvant Effect Of CpG DNA Recombinant Plasmid On Compound Gene Vaccine Of Toxoplasma Gondii

The protozoan parasite Toxoplasma gondii invades and replicates within nucleated cells of warm-blooded animals and causes toxoplasmosis. To control T. gondii, a tool such as a vaccine is necessary because of the massive disease burden of T. gondii in the world.Previous studies have reported that DNA vaccine could only produce partial protection against Toxoplasma gondii, especially in human and big animals. To enhance the immunity of DNA vaccine, we choose CpG motif as the immunoadjuvant. The unmethylated CpG motifs are oligo deoxynudeotides that have strong immunostimulatory activity. It has been reported that either the synthesized CpG motifs or unmethylated CpG exsiting in bacterial DNA can activated the innate immunity to secret IL-6, IL-10 and IL-12.In this study, a segment of double-stranded oligodeoxynucleotide containing CpG motifs was synthesized and subcloned into the plasmid vector of DNA vaccine. We constructed plasmid pcDNA-3.1/CpG, then subcloned SAG1-ROP2 into pcDNA3.1/CpG, and contructed a multiantigenic DNA vaccine pcDNA3.1-SAG1-ROP2-CpG. 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-R.OP2/CpG produced higher Thl immune response compared to other groups immunized with pcDNA3.1-SAG1, pcDNA3.1-SAG1-ROP2, empty plasmid pcDNA3.1 or phosphate buffered saline, respectively. Our study demonstrated that CpG motifs can enhance the protective effect of DNA vaccine.