Immunity induced by DNA vaccine of plasmid encoding the rhoptry protein 1 gene combined with the genetic adjuvant of pcIFN-gamma against Toxoplasma gondii in mice

Objective To construct the eukaryotic expression recombinant plasmid, pcIFN -gamma, as a genetic adjuvant and observe the immune responses elicited by pcDNA3-rhoptry protein 1 (pc-ROP1) combined with pcIFN-gamma against Toxopl asma gondii (T. gondii) infection in mice. Methods A fragment of the IFN-gamma gene was directly inserted into the pcD NA3 plasmid and identified by two restriction endonucleases digestion. pcIF N and pcROP1 DNA was injected into the left leg muscle of mice at a dosage of 100 mug, and a booster vaccination was given at the same dosage after tw o weeks. Control groups were injected with pcDNA3 blank plasmid or normal s aline. At 30, 50 and 70 days after booster injection, kinetic tests were ca rried out: MTT assay for the proliferation response of T lymphocyte cells a nd the activity of NK cells, sandwich ABC-ELISA for the determination of IF N-gamma, IL-2 and IL-10; a serum enzymetic aassay for nitric oxide (NO) in sera and ELISA for the titer of IgG antibody in sera. Results The recombinant plasmid, pcIFN-gamma was constructed. The prolifera tion response of spleen T lymph cells, NK cell killing activity, and serum levels of IFN-gamma, IL-2 and NO in mice injected with pcROP1 and pcIFN-gam ma were higher than in those injected with pcROP1 alone. There was no diffe rence in IgG antibody levels between the two groups. Conclusion The genetic adjuvant, pcIFN-gamma, could enhance the cellular im mune response induced by DNA vaccine of pcROP1 in mice against Toxoplasma g ondii infection.