Protective effect of DNA-mediated immunization with liposome-encapsulated GRA4 against infection of Toxoplasma gondii.
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)-gamma 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 10(3) 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.
Chen
Rui
R
College of Life Sciences, Zhejiang University, Hangzhou 310058, China; Institute of Parasitology, Zhejiang Academy of Medical Science, Hangzhou 310013, China.
Lu
Shao-Hong
SH
Tong
Qun-Bo
QB
Lou
Di
D
Shi
Dong-Yan
DY
Jia
Bing-Bing
BB
Huang
Guo-Ping
GP
Wang
Jin-Fu
JF
D000818:Animals; D005260:Female; D008081:Liposomes / Q000737:chemistry*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D015800:Protozoan Proteins / Q000235:genetics* / Q000276:immunology*; D014123:Toxoplasmosis / Q000276:immunology* / Q000517:prevention & control*; D016896:Treatment Outcome; D019444:Vaccines, DNA / Q000008:administration & dosage* / Q000737:chemistry*
C079248:GRA4 protein, Toxoplasma gondii; D008081:Liposomes; D015800:Protozoan Proteins; D019444:Vaccines, DNA