昆虫杆状病毒表达的猪圆环病毒2d型Cap蛋白-VLP对仔猪的免疫保护效果

Immunoprotective effect of porcine circovirus type 2d Cap-VLP expressed by insect baculovirus on piglets

猪圆环病毒2d基因型(Porcine circovirus type 2d,PCV2d)为猪场当前流行的PCV2优势基因型,为了研究针对PCV2d基因型的病毒样颗粒(Virus-like particle,VLP)疫苗,提高猪圆环病毒病的防控效果。本研究利用杆状病毒表达系统表达了能够自组装为VLP的PCV2d-Cap蛋白,然后将9头21日龄健康仔猪随机分为VLP组、攻毒对照组和空白对照组(n=3)。VLP组的每头仔猪经颈部肌肉注射400μg Cap蛋白-佐剂复合物(PCV2d-VLP),攻毒组注射等体积的PBS与佐剂混合物,空白组注射等体积的PBS。共接种2次,每次间隔14 d。于第2次免疫后21 d,VLP组和攻毒对照组的仔猪通过鼻腔感染PCV2 HBDX-2018株(106TCID50/头),评价PCV2d-VLP诱导的免疫效果。结果表明PCV2d-VLP能够诱导仔猪产生高水平的特异性IgG抗体和中和抗体,刺激IFN-γ水平升高,引起外周血淋巴细胞增殖能力增强,降低病毒经鼻腔和直肠的排毒率及病毒血症阳性率,减轻腹股沟淋巴结和脾脏的病理损伤,降低组织中的病毒载量。上述研究表明,应用杆状病毒表达的PCV2d-Cap蛋白能自组装为VLP,并能诱导仔猪产生良好的免疫保护效应,具有进一步开发为PCV2d-VLP疫苗的潜力。

Porcine circovirus type 2d(PCV2d)is the dominant PCV2 genotype currently prevalent in swine farms.In order to obtain a virus-like particle(VLP)vaccine targeting the PCV2d genotype to improve the prevention and control of porcine circovirus disease.In this study used the baculovirus expression system to express the PCV2d-Cap protein which can self-assemble into VLP.And then nine 21-day-old healthy piglets were randomly divided into VLP group,Challenge control group,and Blank control group(n=3).400μg of Cap protein-adjuvant complex(PCV2d-VLP vaccine)was injected intramuscularly in the neck on each piglet in the VLP group,An equal volume of PBS with adjuvant mixture was injected in the challenge group,and the blank group was injected with an equal volume of PBS.A total of two vaccinations were administered at 14 d intervals.At 21 d after the second immunization,pigs in the VLP group and the challenge control group were infected with the PCV2 HBDX-2018 strain(106TCID50/each)through the nasal cavity to evaluate the immunoprotective effect induced by the PCV2d-VLP vaccine.The PCV2d-VLP vaccine was able to induce piglets to produce higher levels of specific IgG antibodies and neutralizing antibodies,causing a significant increase in both IFN-γlevels and the proliferative capacity of peripheral blood lymphocytes.The rate of nasal and rectal excretion and the positive rate of viremia were reduced.The pathological damage of the inguinal lymph nodes and spleen were reduced,and the viral load in tissues also reduced.The above studies demonstrated that the PCV2d-Cap protein expressed by baculoviruses could self-assemble into VLPs,which induced a favorable immunoprotective effect in piglets,and had the potential to be further developed into a PCV2d-VLP vaccine.