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The dense granule protein 4(GRA4) is a granular protein from Toxoplasma gondii,and is a candidate for vaccination against this parasite. In this study,the plasmid pcDNA3.1-GRA4(pGRA4) ,encoding for the GRA4 antigen,was incorporated by the dehydration-rehydration method into liposomes composed of 16 mmol/L egg phosphatidylcholine(PC) ,8 mmol/L dioleoyl phosphatidylethanolamine(DOPE) ,and 4 mmol/L 1,2-diodeoyl-3-(trimethylammonium) propane(DOTAP) . C57BL/6 mice and BALB/c mice were immunized intramuscularly three times with liposome-encapsulated pGRA4 to determine whether DNA immunization could elicit a protective immune response to T. gondii. Enzyme-linked immunosorbent assay(ELISA) of sera from immunized mice showed that liposome-encapsulated pGRA4 generated high levels of IgG antibodies to GRA4. Production of primary interferon(IFN) -γ and interleukin(IL) -2 in GRA4-stimulated splenocytes from vaccinated mice suggested a modulated Th1-type response. 72.7% of C57BL/6 mice immunized with liposome-encapsulated pGRA4 survived the challenge with 80 tissue cysts of ME49 strain,whereas C57BL/6 mice immunized with pGRA4 had only a survival rate of 54.5%. When immunized BALB/c mice were intraperitoneally challenged with 103 tachyzoites of the highly virulent RH strain,the survival time of mice immunized with liposome-encapsulated pGRA4 was markedly longer than that of other groups. Our observations show that liposome-encapsulated pGRA4 enhanced the protective effect against infection of T. gondii.
The present granzyme pcDNA3.1-GRA4 (pGRA4), encoding for the GRA4 antigen, was incorporated by Toxoplasma gondii, and is a candidate for vaccination against this parasite. the dehydration-rehydration method into liposomes composed of 16 mmol / L egg phosphatidylcholine (PC), 8 mmol / L dioleoyl phosphatidylethanolamine (DOPE), and 4 mmol / L 1,2-diiodoyl- 3- (trimethylammonium) propane (DOTAP). C57BL / 6 mice were immunized intramuscularly with three times with liposome-encapsulated pGRA4 to determine whether DNA immunization could elicit a protective immune response to T. gondii. Enzyme-linked immunosorbent assay (ELISA) of sera from immunized mice showed that Production of primary interferon (IFN) -γ and interleukin (IL) -2 in GRA4-stimulated splenocytes from vaccinated mice suggested a modulated Th1-type response. 72.7% of C57BL / 6 mice immunized wi th liposome-encapsulated pGRA4 survived the challenge with 80 tissue cysts of ME49 strain, while C57BL / 6 mice immunized with pGRA4 had only a survival rate of 54.5%. When immunized BALB / c mice were intraperitoneally challenged with 103 tachyzoites of the highly virulent RH strain, the survival time of mice immunized with liposome-encapsulated pGRA4 was markedly longer than that of other groups. Our observations show that liposome-encapsulated pGRA4 enhanced the protective effect against infection of T. gondii.