SAG1和IL-2基因佐剂混合免疫诱导鼠抗弓形虫感染的研究

DNA-mediated immunization with a combination of SAG1 and IL-2 gene adjuvant against infection of Toxoplasma gondii in mice

目的 了解编码SAG1的重组质粒和IL 2基因佐剂在小鼠体内的免疫反应 ,评价该疫苗对弓形虫的保护作用。方法 编码SAG1的质粒和鼠源性IL 2表达载体以 10 0 μg的剂量免疫小鼠 ,3w后两次以相同的剂量加强免疫 ,分别以PBS和空质粒 pcDNA3 感染。采用ELISA法测定抗体水平、亚型、IFN γ和IL 4的含量 ,PCR及原位杂交检测感染鼠中DNA的整合及降解。所有鼠均由强毒力RH株弓形虫感染。结果 SAG1表达质粒 3次免疫后鼠体内特异IgG水平明显增高 ,IL 2表达质粒的联合使用导致IgG2a水平升高和IFN γ的产生。混合质粒注射的小鼠抗弓形虫感染的存活时间延长。结论 由SAG1DNA诱导的免疫应答因IL - 2表达质粒的共同注射而增强 。

Objective To characterize the immune responses induced by SAG1 encoding plasmid combined with IL-2 gene adjuvant in mice and to assess the protective effect of this vaccination against toxoplasmosis. Methods Mice were co-injected intramuscularly with plasmid encoding Toxoplasma gondii SAG1 plus murine IL-2 expression vector at the dose of 100μg. Booster immunizations were employed at the same dose 2 times at 3-week interval. Mice were injected with PBS and vector plasmid, pcDNA 3, as control group. Humoral and cellular responses were analyzed using ELISA for the determination of the production of antibodies, antibody isotypes, IFN-γ and IL-4. To detect the integration and dissemination of the plasmid DNA in the injected mice, PCR and in situ hybridization were performed. All mice were conducted challenge infection with highly virulent RH tachyzoites of Toxoplasma gondii via intraperitoneal injection. Results SAG1 specific IgG was produced in a significant level in mice after immunization three times with SAG1 expression plasmid. Co-injection with IL-2 expression plasmid enhanced the expression level of IgG2a and IFN-γ. Challenge of the mice vaccinated with combined plasmids with RH tachyzoites resulted in a prolongation survival. Conclusion Humoral and cytokine responses elicited by SAG1 DNA immunization can be modulated by co-injection with IL-2 cytokine expression plasmid. The use of DNA vaccine in combination with an appropriate cytokine gene to prevent T.gondii infection is valuable for further investigation.