Construction of a recombinant plasmid harbouring the rhoptry protein 1 gene of Toxoplasma gondii and preliminary observations on DNA immunity

Objective To observe the immune responses elicited in BALB/c mice by a DNA vaccine. A gene encoding rhoptry protein 1 (ROP1) from Toxoplasma gondii (T . gondii) was cloned into vector pcDNA3. Methods Amplifyied gene fragments coding for ROP1 from the genomic DNA of T . gondii ZS2 were inserted into cloning vector, pUC18, and sub-cloned into pcDNA3. Mice were injected at a dosage of 100 pg recombinant plasmid DNA by intramuscular injection and boosted after 2 weeks. pcDNA3 and normal salin e were used as control. 30, 50 and 70 days after the second immunization, N K cell activity, T lymphocyte proliferation and sub-clusters and serum IgG antibody were assayed. Results The specific gene fragment coding for ROP1 was amplified and a pcRO P1 recombinant was constructed. At 30 days after immunization, the spleens of the mice were obviously enlarged evidently. NKC activity and the prolife ration of spleen T lymphocytes seen on MTT assay were higher in pcROP1 grou p than in the controls. The number of CD4(+) T cells exhibited no obvious i ncrease compared with that of the control, but CD8(+) T cells were obviousl y increased (P < 0.05). At 90 days after vaccination, the titer of IgG anti body in the serum of vaccinated mice was positive (1:100). Conclusion pcROP1 was constructed and it could elicit both cellular and hum oral immune responses in immunized mice.