Laboratory of Molecular Virology and Recombinant Vaccine Development, Department of Medical Biotechnologies and Translational Medicine, University of Milan, Via Vanvitelli 32, 20129, Milan, Italy.
HPV-UNIT, Laboratory of Virology, Regina Elena National Cancer Institute, Via delle Messi d'Oro, 156, 00158, Rome, Italy.
Virol J. 2021 Mar 4;18(1):50. doi: 10.1186/s12985-021-01519-x.
Zika virus (ZIKV) has been declared a public health emergency that requires development of an effective vaccine, as it might represent an international threat.
Here, two novel DNA-based (pVAXzenv) and fowlpox-based (FPzenv) recombinant putative vaccine candidates were constructed that contained the cPrME genes of ZIKV. The env gene inserted into the fowlpox vector was verified for correct transgene expression by Western blotting and by immunofluorescence in different cell lines. The production of virus-like particles as a result of env gene expression was also demonstrated by electron microscopy. BALB/c mice were immunosuppressed with dexamethasone and immunized following a prime-boost strategy in a heterologous protocol where pVAXzenv was followed by FPzenv, to evaluate the immunogenicity of the Env protein. The mice underwent a challenge with an epidemic ZIKV after the last boost.
These data show that the ZIKV Env protein was correctly expressed in both normal human lung fibroblasts (MRC-5 cells) and green monkey kidney (Vero) cells infected with FPzenv, and that the transgene expression lasted for more than 2 weeks. After mucosal administration of FPzenv, the immunized mice showed specific and significantly higher humoral responses compared to the control mice. However, virus neutralizing antibodies were not detected using plaque reduction assays.
Although BALB/c mice appear to be an adequate model for ZIKV infection, as it mimics the natural mild infection in human beings, inadequate immune suppression seemed to occur by dexamethasone and different immune suppression strategies should be applied before challenge to reveal any protection of the mice.
寨卡病毒（ZIKV）已被宣布为公共卫生紧急事件，需要开发有效的疫苗，因为它可能构成国际威胁。
本研究构建了两种新型基于 DNA（pVAXzenv）和禽痘病毒（FPzenv）的重组候选疫苗，其中包含 ZIKV 的 cPrME 基因。通过 Western blot 和不同细胞系中的免疫荧光验证插入禽痘病毒载体的 env 基因的正确转基因表达。env 基因表达导致病毒样颗粒的产生也通过电子显微镜得到证实。BALB/c 小鼠用地塞米松免疫抑制，并按照异源方案进行初免-加强免疫策略进行免疫，其中 pVAXzenv 后接 FPzenv，以评估 Env 蛋白的免疫原性。最后一次加强免疫后，这些小鼠接受了流行的 ZIKV 挑战。
这些数据表明，FPzenv 感染的正常人类肺成纤维细胞（MRC-5 细胞）和绿猴肾（Vero）细胞中正确表达了 ZIKV Env 蛋白，并且转基因表达持续了两周以上。经黏膜给予 FPzenv 后，免疫小鼠的体液反应明显高于对照组。然而，使用蚀斑减少测定法未检测到中和抗体。
尽管 BALB/c 小鼠似乎是 ZIKV 感染的合适模型，因为它模拟了人类的自然轻度感染，但地塞米松引起的免疫抑制不足，在进行挑战之前应应用不同的免疫抑制策略以揭示对小鼠的任何保护作用。
