核酸疫苗初免-蛋白疫苗加强的免疫策略提高日本血吸虫核酸疫苗免疫效果

DNA prime followed by protein boost enhances the protective efficacy against Schistosoma japonicum infection in mice

摘要:

为研制抗血吸虫疫苗提供实验依据，探讨了抗血吸虫SjGST-32核酸疫苗与蛋白疫苗联合免疫的免疫增强效应及免疫应答特征。将日本血吸虫DNA疫苗VR1012-SjGST-32与重组蛋白疫苗rSjGST-32分别在第0、2和4周免疫小鼠，在第6周攻击感染日本血吸虫尾蚴，攻击感染45 d后剖杀小鼠，计算减虫率、检卵率以及检测肝脏病理变化，观察免疫保护效果；检测小鼠血清中特异性IgG抗体滴度，T细胞增殖反应和抗原特异性CD4+IFN-γ+、CD4+IL-4+和CD4+IL-10+的数量，探讨免疫应答特征。结果显示，DNA初免-蛋白加强的联合免疫组的保护作用优于单独免疫组，显著提高了减虫率 (42.3％) 和减卵率 (59.6％)，并且能够显著减轻血吸虫虫卵对肝脏的病理损害；进一步发现，DNA疫苗和蛋白疫苗联合应用增强了机体T淋巴细胞增殖反应、抗体IgG滴度以及抗原特异性CD4+IFN-γ+的产生。这些研究为新型血吸虫疫苗的优化设计和合理应用提供了依据。

Abstract:

Schistosomiasis japonica is an endemic, zoonotic disease of major public health importance in China. Vaccination is needed as a complementary approach to the ongoing control programs. In the present study, we determined if the efficacies of DNA vaccine encoding the SjGST and Sj32 asparaginyl endopeptidase protein could be enhanced by boosting with SjGST-32 protein vaccines. Mice were inoculated with a VR1012-SjGST-32 DNA vaccine followed by boosting with rSjGST-32 at 0, 14 and 28 d. Two weeks after the final boost, mice were challenged percutaneously with cercariae. On day 45 following the challenge, all mice were sacrificed and the numbers of recovered worms and hepatic eggs were counted. Moreover, we analyzed the immune response among various vaccination groups. The results showed that DNA vaccine efficacy was enhanced when mice were boosted with protein vaccine. Adult worm and liver egg burdens were reduced 42.3% and 59.6%, respectively. We further found that DNA vaccine followed by boosting with protein significantly increased the IgG titer and T cell proliferation over those seen in mice vaccinated solely with DNA vaccines. Furthermore, the higher level of IFN-γ expression in the splenetic CD4+ T cell showed that DNA prime-Protein boosting vaccine induced CD4+ Th1-type responses. Thus, DNA vaccine efficacy was significantly enhanced via boosting protein vaccine which might provide a basis for rational application of the Schistosoma vaccine.