van Zyl Albertha R, Meyers Ann E, Rybicki Edward P
Department of Molecular and Cell Biology, University of Cape Town, Private Bag X3, Rondebosch, 7700, South Africa.
Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Observatory, Cape Town, 7925, South Africa.
BMC Biotechnol. 2017 May 30;17(1):47. doi: 10.1186/s12896-017-0370-5.
Bluetongue is a disease of domestic and wild ruminants caused by bluetongue virus serotypes (BTV), which have caused serious outbreaks worldwide. Commercially available vaccines are live-attenuated or inactivated virus strains: these are effective, but there is the risk of reversion to virulence or reassortment with circulating strains for live virus, and residual live virus for the inactivated vaccines. The live-attenuated virus vaccines are not able to distinguish naturally infected animals from vaccinated animals (DIVA compliant). Recombinant vaccines are preferable to minimize the risks associated with these vaccines, and would also enable the development of candidate vaccines that are DIVA-compliant.
In this study, two novel protein body (PB) plant-produced vaccines were developed, Zera®-VP2ep and Zera®-VP2. Zera®-VP2ep contained B-cell epitope sequences of multiple BTV serotypes and Zera®-VP2 contained the full-length BTV-8 VP2 codon-optimised sequence. In addition to fulfilling the DIVA requirement, Zera®-VP2ep was aimed at being multivalent with the ability to stimulate an immune response to several BTV serotypes. Both these candidate vaccines were successfully made in N. benthamiana via transient Agrobacterium-mediated expression, and in situ TEM analysis showed that the expressed proteins accumulated within the cytoplasm of plant cells in dense membrane-defined PBs. The peptide sequences included in Zera®-VP2ep contained epitopes that bound antibodies produced against native VP2. Preliminary murine immunogenicity studies showed that the PB vaccine candidates elicited anti-VP2 immune responses in mice without the use of adjuvant.
These proof of concept results demonstrate that Zera®-VP2ep and Zera®-VP2 have potential as BTV vaccines and their development should be further investigated.
蓝舌病是由蓝舌病病毒血清型（BTV）引起的家养和野生反刍动物疾病，已在全球范围内引发严重疫情。市售疫苗为减毒活疫苗或灭活病毒株：这些疫苗有效，但减毒活疫苗存在毒力返强或与流行毒株重配的风险，灭活疫苗则存在残留活病毒的风险。减毒活病毒疫苗无法区分自然感染动物和接种疫苗的动物（不具备区分感染动物和免疫动物的能力）。重组疫苗更可取，可将与这些疫苗相关的风险降至最低，还能开发出具备区分感染动物和免疫动物能力的候选疫苗。
在本研究中，开发了两种新型植物生产的蛋白体（PB）疫苗，即Zera®-VP2ep和Zera®-VP2。Zera®-VP2ep包含多种BTV血清型的B细胞表位序列，Zera®-VP2包含经密码子优化的全长BTV-8 VP2序列。除满足区分感染动物和免疫动物的要求外，Zera®-VP2ep旨在具有多价性，能够刺激针对多种BTV血清型的免疫反应。这两种候选疫苗均通过农杆菌介导的瞬时表达在本氏烟草中成功生产，原位透射电镜分析表明，表达的蛋白在植物细胞的细胞质中以密集的膜界定蛋白体形式积累。Zera®-VP2ep中包含的肽序列含有与针对天然VP2产生的抗体结合的表位。初步的小鼠免疫原性研究表明，这些PB候选疫苗在不使用佐剂的情况下能在小鼠中引发抗VP2免疫反应。
这些概念验证结果表明，Zera®-VP2ep和Zera®-VP2有作为BTV疫苗的潜力，应进一步研究其开发。
