BACKGROUND Outbreaks of Classical swine fever virus (CSFV) cause significant economic losses in the swine industry. Vaccination is the major method to prevent and control the disease. As live attenuated vaccines fail to elicit differentiable immunity between infected and vaccinated animals, subunit vaccine was considered as an alternative candidate to prevent and eradicate CSFV. Subunit vaccines present advantages in DIVA immunogenicity and safety. The technology was limited due to the low yield and the high cost with multiple and large doses. The native E2 signal peptide has not been well defined before. Here, the aim of this study is to develop a cost-effective and efficacious E2 vaccine candidate against CSFV with signal peptide and E2 sequence selection. RESULTS A novel CSFV E2 sequence (E2ZJ) was identified from an epidemic strain of Zhejiang for outstanding secretion in baculovirus and enhanced immunogenicity. E2 secretion induced with the selected signal peptide, SPZJ (SP23), increase at least 50% as compared to any other signal peptides tested. Besides, unique antigenic features were identified in E2ZJ. As indicated with immunized sera in IFA against CSFV infection, E2ZJ elicited CSFV antibodies at the earlier stage than other E2 types tested in mice. Moreover, higher level of neutralizing and CSFV antibodies against CSFV with E2ZJ was detected than other E2s with the same dosage at 28 dpi. Further, E2ZJ successfully elicited neutralizing immunity in piglets. A single dose of 5 μg of E2ZJ was sufficient to induce protective antibodies against CSFV in piglets and provided 100% protection against lethal virus challenge. CONCLUSIONS Our studies provide evidence that E2ZJ guided by a novel E2 signal peptide (SPZJ) was efficiently secreted and presented significantly improved immunogenicity than conventional E2 vaccines. Moreover, a single dose of 5 μg E2ZJ is efficacious against CSFV in piglets.

中文翻译：

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鉴定具有改善的针对猪的CSFV分泌和免疫原性的E2。

背景技术经典猪瘟病毒（CSFV）的爆发在养猪业中造成重大的经济损失。疫苗接种是预防和控制该疾病的主要方法。由于减毒活疫苗无法在感染和接种的动物之间引起差异性免疫，因此亚单位疫苗被认为是预防和消除CSFV的替代候选药物。亚单位疫苗在DIVA免疫原性和安全性方面具有优势。该技术由于多剂量和大剂量的低产量和高成本而受到限制。天然E2信号肽以前尚未被很好地定义。在这里，这项研究的目的是开发一种具有成本效益和有效的针对CSFV的E2候选疫苗，它具有信号肽和E2序列选择功能。结果从浙江流行病株中鉴定出一种新的CSFV E2序列（E2ZJ），该病毒在杆状病毒中具有突出的分泌并增强了免疫原性。与测试的任何其他信号肽相比，由选定的信号肽SPZJ（SP23）诱导的E2分泌增加至少50％。此外，在E2ZJ中鉴定出独特的抗原特征。正如IFA中针对CSFV感染的免疫血清所表明的那样，与在小鼠中测试的其他E2类型相比，E2ZJ在更早的阶段引发CSFV抗体。此外，在28 dpi时，与使用相同剂量的其他E2相比，检测到的E2ZJ抗CSFV的中和CSFV抗体水平更高。此外，E2ZJ成功引发了仔猪的中和免疫。单剂量5μgE2ZJ足以诱导仔猪抗CSFV的保护性抗体，并提供100％的保护力以抵抗致命的病毒攻击。结论我们的研究提供了证据，表明由新型E2信号肽（SPZJ）引导的E2ZJ与常规E2疫苗相比被有效分泌，并具有显着改善的免疫原性。此外，单剂5μgE2ZJ对仔猪的CSFV有效。