Department of Arboviral Vaccine, National Institutes for Food and Drug Control, Beijing 102629, China.
Chengdu Institutes for Biological Products, Chengdu 610023, China.
Vaccine. 2018 Jul 25;36(31):4650-4656. doi: 10.1016/j.vaccine.2018.06.040. Epub 2018 Jun 25.
Japanese encephalitis (JE) live attenuated vaccine SA14-14-2 is the most widely used JE vaccine in the world. Large-scale clinical trials have demonstrated satisfactory safety and efficacy profiles. The establishment of genetic and attenuated neurovirulence characteristics and their stabilities of SA14-14-2 virus are important in relation to vaccine safety in humans. Therefore, several researchers have studied and analyzed the full-length gene sequences of the SA14-14-2 virus strain. However, sequencing results have shown a significant difference. Here, we further studied the full-length sequence of three class seed virus banks of the vaccine as well as two vaccine viruses with different passages in primary hamster kidney cells, and compared them with our original stored SA14 parent virus (low passage in mouse brain). The full-length gene sequence determined in this study indicates there were 57 nucleotide and 25 amino acid substitutions of the SA14-14-2 strain compared to its parental SA14 virus strain. The full-length sequences of the three class seed bank viruses and the vaccine virus PHKC8 were completely identical among them, but the working seed virus passaged in primary hamster kidney cells for 17 generations (PHKC17) had a single nucleotide change at the 5' NCR. Both KM and ICR mice tested by intracerebral (i.c.) or subcutaneous (s.c.) routes with the three class seed viruses and vaccine viruses with ≥5.7 lgpfu/mL remained healthy, but all the mice inoculated with the SA14 parental virus strain died as early as day 5 post-inoculation. The present study provided new information on the full-length gene sequence and attenuated neurovirulence of SA14-14-2. They can be used as a reference sequence for vaccine quality control and surveillance of neurovirulence reversion following vaccination. Moreover, the present results further demonstrated the high genetic and phenotypic stabilities of the SA14-14-2 virus, suggesting the neurovirulence reversion of the vaccine strain will be highly unlikely.
日本脑炎（JE）减毒活疫苗 SA14-14-2 是世界上应用最广泛的 JE 疫苗。大规模临床试验表明其具有良好的安全性和有效性。SA14-14-2 病毒的遗传和减毒神经毒力特征及其稳定性的建立对于人类疫苗的安全性至关重要。因此，一些研究人员对 SA14-14-2 病毒株的全长基因序列进行了研究和分析。然而，测序结果显示存在显著差异。在这里，我们进一步研究了疫苗三个批次的种子库的全长序列以及在原代仓鼠肾细胞中传代的两种不同疫苗病毒，并将其与我们原始保存的 SA14 亲代病毒（鼠脑低传代）进行了比较。本研究确定的全长基因序列表明，SA14-14-2 株与亲代 SA14 病毒株相比，有 57 个核苷酸和 25 个氨基酸的替换。三个批次的种子库病毒和 PHKC8 疫苗病毒的全长序列完全相同，但在原代仓鼠肾细胞中传代 17 代的工作种子病毒（PHKC17）在 5'NCR 有一个单核苷酸变化。通过脑内（i.c.）或皮下（s.c.）途径接种三个批次的种子病毒和疫苗病毒，其效价≥5.7 lgpfu/mL 的 KM 和 ICR 小鼠均保持健康，但所有接种 SA14 亲代病毒株的小鼠早在接种后第 5 天就死亡。本研究提供了 SA14-14-2 全长基因序列和减毒神经毒力的新信息，可作为疫苗质量控制和接种后神经毒力回复的参考序列。此外，本研究结果进一步证实了 SA14-14-2 病毒的高遗传和表型稳定性，表明疫苗株的神经毒力回复极不可能发生。
