Qu Daofeng, Wang Suhua, Cai Weiming, Du Aifang
Institute of Preventive Veterinary Medicine, Zhejiang University, Hangzhou, Zhejiang 310029, China.
Vaccine. 2008 Aug 18;26(35):4541-8. doi: 10.1016/j.vaccine.2008.06.030. Epub 2008 Jun 30.
Infection with the intracellular protozoan parasite Toxoplasma gondii causes serious public health problems and is of great economic importance worldwide. The T. gondii surface antigen protein SAG1 is a significant candidate vaccine against toxoplasmosis. In this study, we evaluated safety, stability of ZJ111/pcDNA3-SAG1, a DNA vaccine delivered in attenuated Salmonella typhimurium, and immune responses induced by immunizing ICR mice orally with ZJ111/pcDNA3-SAG1 of different doses. Mice had no significant differences in body weight between the groups before immunization and at week 4 after the booster immunization. The ZJ111/pcDNA3-SAG1 was eventually eliminated from the spleen and liver on week 6 post-immunization. The plasmid pcDNA3-SAG1 was stably maintained over 90% of the attenuated S. typhimurium population after 100 generations of growth in antibiotic-free media. Oral immunization of mice with ZJ111/pcDNA3-SAG1 elicited specific humoral responses and stimulated proliferation of splenocytes (P<0.05). The cellular immune response was associated with the production of IFN-gamma, indicating that a Th-1 type response was elicited, which was confirmed by the production of large amounts of IgG2a (P<0.01). Mice immunized with ZJ111/pcDNA3-SAG1 displayed significant protection against an intraperitoneally challenge with 500 tachyzoite forms of T. gondii RH strain. Vaccination at 10(7) and 10(8)CFU per mice provided a 20% and 10% survival rate comparing 100% mortality of the non-immunized mice, exhibiting longer living time and better survival rate. These results confirmed a DNA vaccine delivered in attenuated S. typhimurium, ZJ111/pcDNA3-SAG1, can elicit specific immune response as well as provide effective protection against T. gondii infection, and the dosage of 10(7)CFU was a most considerate one.
细胞内原生动物寄生虫刚地弓形虫感染会引发严重的公共卫生问题，在全球范围内具有重大经济影响。刚地弓形虫表面抗原蛋白SAG1是抗弓形虫病的重要候选疫苗。在本研究中，我们评估了通过减毒鼠伤寒沙门氏菌递送的DNA疫苗ZJ111/pcDNA3-SAG1的安全性、稳定性，以及用不同剂量的ZJ111/pcDNA3-SAG1口服免疫ICR小鼠所诱导的免疫反应。免疫前及加强免疫后第4周，各实验组小鼠体重无显著差异。免疫后第6周，ZJ111/pcDNA3-SAG1最终从脾脏和肝脏中清除。在无抗生素培养基中传代100代后，质粒pcDNA3-SAG1在超过90%的减毒鼠伤寒沙门氏菌群体中稳定维持。用ZJ111/pcDNA3-SAG1口服免疫小鼠可引发特异性体液反应，并刺激脾细胞增殖（P<0.05）。细胞免疫反应与IFN-γ的产生相关，表明引发了Th-1型反应，大量IgG2a的产生证实了这一点（P<0.01）。用ZJ111/pcDNA3-SAG1免疫的小鼠对腹腔注射500个刚地弓形虫RH株速殖子具有显著的保护作用。每只小鼠接种10(7)和10(8)CFU时，生存率分别为20%和10%，而未免疫小鼠的死亡率为100%，显示出更长的存活时间和更好的生存率。这些结果证实，通过减毒鼠伤寒沙门氏菌递送的DNA疫苗ZJ111/pcDNA3-SAG1可引发特异性免疫反应，并有效抵抗刚地弓形虫感染，10(7)CFU的剂量是最为合适的。
