Protective effect of DNA-mediated immunization with a combination of SAG1 and IL-2 gene adjuvant against infection of Toxoplasma gondii in mice
Chen, G.; Chen, H.; Guo, H.; Zheng, H.
Chinese Medical Journal 115(10): 1448-1452
2002
ISSN/ISBN: 0366-6999 PMID: 12490084 Document Number: 540989
Objective: To characterize the immune response induced by surface antigen 1 (SAG1) encoding plasmid combined with interleukin 2 (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 a dose of 100 micro g. Booster immunizations were employed 2 more times at 3-week interval. As controls, mice were inoculated with PBS or empty plasmid pcDNA3. Humoral and cellular responses were assayed using ELISA for the determination of Ab, Ab isotype and IFN- gamma , as well as IL-4. To detect the integration and dissemination of DNA in the injected mice, PCR and in situ hybridization were performed. All mice were then infected with highly virulent RH tachyzoites of T. gondii intraperitoneally. Results: Significant increases in specific IgG levels were observed in mice after immunization 3 times with SAG1 expression plasmid. With respect to the IgG isotype, coinoculation of IL-2 expression plasmid enhanced the level of IgG2a and the production of IFN- gamma . Challenging mice by vaccinating with combined plasmids with RH tachyzoites resulted in prolonged survival. Conclusion: Humoral and cytokine responses elicited by SAG1 DNA immunization can be modulated by coinoculation with IL-2 expression plasmid. The use of DNA vaccine in combination with an appropriate cytokine gene to prevent T. gondii infection warrants further investigation.