BACKGROUND Porcine circovirus type 2 (PCV2) is an economically important pathogen in the swine industry worldwide. Vaccination remains the principal tool to control PCV2-associated diseases (PCVADs). Current vaccines do not eliminate viral shedding in the environment. To enhance the efficacy of PCV2 vaccines, recombinant virus-like particles (VLPs) of PCV2 were generated by fusing a truncated form of flagellin FliC (TFlg: 85-111aa) with the PCV2 capsid protein (Cap). RESULTS The recombinant proteins were expressed in Escherichia coli and detected using Western blotting. The abilities of the recombinant proteins to assemble into VLPs were observed under transmission electron microscopy (TEM). The protective immune responses of recombinant VLPs were further evaluated by immunization of mice. The results showed that insertion of TFlg into C terminal of the Cap protein did not affect the formation of VLPs and boosted both humoral and cellular immune responses in mice. After a challenge with PCV2, in the Cap-TFlg vaccinated group, viremia was milder and viral loads were lower as compared with those in the Cap vaccinated group. CONCLUSION These results suggest that recombinant VLPs of PCV2 containing a TFlg adjuvant can be used as a promising PCV2 vaccine candidate.

中文翻译：

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将截短形式的鞭毛蛋白（TFlg）掺入猪圆环病毒2型病毒样颗粒可增强小鼠的免疫反应。

背景技术2型猪圆环病毒（PCV2）是全世界养猪业中经济上重要的病原体。疫苗接种仍然是控制PCV2相关疾病（PCVAD）的主要工具。当前的疫苗不能消除环境中的病毒脱落。为了增强PCV2疫苗的功效，通过将截短形式的鞭毛蛋白FliC（TFlg：85-111aa）与PCV2衣壳蛋白（Cap）融合产生了PCV2的重组病毒样颗粒（VLP）。结果重组蛋白在大肠杆菌中表达，并用蛋白质印迹法检测。在透射电子显微镜（TEM）下观察到重组蛋白组装成VLP的能力。通过小鼠免疫进一步评估了重组VLP的保护性免疫应答。结果表明，将TF1g插入Cap蛋白的C末端不会影响VLP的形成，并能增强小鼠的体液和细胞免疫反应。与Cap疫苗接种组相比，在用PCV2攻击后，Cap-TFlg疫苗接种组的病毒血症较轻，病毒载量较低。结论这些结果表明，含有TF1g佐剂的PCV2重组VLP可用作有前途的PCV2疫苗候选物。