Immunogenicity and pathogenicity of chimeric infectious DNA clones of pathogenic porcine circovirus type 2 (PCV2) and nonpathogenic PCV1 in weanling pigs
Immunogenicity and pathogenicity of chimeric infectious DNA clones of pathogenic porcine circovirus type 2 (PCV2) and nonpathogenic PCV1 in weanling pigs
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DOI：
10.1128/jvi.77.20.11232-11243.2003
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发表时间：
2003-10-01
影响因子：
5.4
通讯作者：
Meng, XJ
中科院分区：
文献类型：
--
作者：
Fenaux, M;Opriessnig, T;Meng, XJ
猪圆环病毒 2 型 (PCV2) 是断奶后多系统消耗综合征 (PMWS) 的主要病原体，而普遍存在的猪圆环病毒 1 型 (PCV1) 对猪来说是非致病性的。我们在此报告了 PCV1 和 PCV2 的两个嵌合感染性 DNA 克隆的构建和表征。嵌合 PCV1-2 克隆包含克隆在非致病性 PCV1 基因组骨架中的 PCV2 衣壳基因。还通过用 PCV2 基因组骨架中的 PCV1 的基因替换 PCV2 衣壳基因，构建了相互嵌合的 PCV2-1 DNA 克隆。 PCV1、PCV2以及嵌合PCV1-2和PCV2-1 DNA克隆均显示出在PK-15细胞中具有感染性，并且测定并比较了它们的体外生长特性。为了评估嵌合感染性 DNA 克隆的免疫原性和致病性，40 头无特定病原体 (SPF) 猪被随机分为 5 组，每组 8 头猪。第一组猪接受磷酸盐缓冲盐水作为阴性对照。第2组猪每只腹股沟浅淋巴结注射200杯PCV1感染性DNA克隆。类似地，将第3组猪每只注射200杯PCV2感染性DNA克隆，将第4组猪每只注射200杯嵌合PCV1-2感染性DNA克隆，将第5组猪每只注射200杯相互嵌合PCV2-1感染性DNA克隆。正如预期的那样，在第 3 组和第 4 组猪中检测到 PCV2 衣壳抗原抗体的血清转化。第 2 组和第 5 组猪全部血清转化为 PCV1 抗体。接种 PCV2 感染性 DNA 克隆的动物各组织中的肉眼和微观损伤明显比接种 PCV1、嵌合 PCV1-2 和相互嵌合 PCV2-1 感染性 DNA 克隆的猪中发现的严重。这些数据表明，具有克隆到非致病性PCV1基因组骨架中的致病性PCV2的免疫原性ORF2衣壳基因的嵌合PCV1-2病毒诱导针对致病性PCV2衣壳抗原的特异性抗体应答，但在猪中减弱。未来的研究有必要评估嵌合 PCV1-2 感染性 DNA 克隆作为针对 PCV2 感染和 PMWS 的基因工程减毒活疫苗的有用性。
Porcine circovirus type 2 (PCV2) is the primary causative agent of postweaning multisystemic wasting syndrome (PMWS), whereas the ubiquitous porcine circovirus type 1 (PCV1) is nonpathogenic for pigs. We report here the construction and characterization of two chimeric infectious DNA clones of PCV1 and PCV2. The chimeric PCV1-2 clone contains the PCV2 capsid gene cloned in the backbone of the nonpathogenic PCV1 genome. A reciprocal chimeric PCV2-1 DNA clone was also constructed by replacing the PCV2 capsid gene with that of PCV1 in the backbone of the PCV2 genome. The PCV1, PCV2, and chimeric PCV1-2 and PCV2-1 DNA clones were all shown to be infectious in PK-15 cells, and their growth characteristics in vitro were determined and compared. To evaluate the immunogenicity and pathogenicity of the chimeric infectious DNA clones, 40 specific-pathogen-free (SPF) pigs were randomly assigned into five groups of eight pigs each. Group I pigs received phosphate-buffered saline as the negative control. Group 2 pigs were each injected in the superficial inguinal lymph nodes with 200 mug of the PCV1 infectious DNA clone. Group 3 pigs were each similarly injected with 200 mug of the PCV2 infectious DNA clone, group 4 pigs were each injected with 200 mug of the chimeric PCV1-2 infectious DNA clone, and group 5 pigs were each injected with 200 mug of the reciprocal chimeric PCV2-1 infectious DNA clone. As expected, seroconversion to antibodies to the PCV2 capsid antigen was detected in group 3 and group 4 pigs. Group 2 and 5 pigs all seroconverted to PCV1 antibody. Gross and microscopic lesions in various tissues of animals inoculated with the PCV2 infectious DNA clone were significantly more severe than those found in pigs inoculated with PCV1, chimeric PCV1-2, and reciprocal chimeric PCV2-1 infectious DNA clones. These data indicated that the chimeric PCV1-2 virus with the immunogenic ORF2 capsid gene of pathogenic PCV2 cloned into the nonpathogenic PCV1 genomic backbone induces a specific antibody response to the pathogenic PCV2 capsid antigen but is attenuated in pigs. Future studies are warranted to evaluate the usefulness of the chimeric PCV1-2 infectious DNA clone as a genetically engineered live-attenuated vaccine against PCV2 infection and PMWS.