title: Attenuation of porcine circovirus type-2b by replacement with the Rep gene of porcine circovirus type-1.
abstract: Porcine circovirus type-2 (PCV2) is the primary causative agent of porcine circovirus-associated diseases and has 4 main ORFs, ORF1 (Rep gene), ORF2 (Cap gene), ORF3 within ORF1, and ORF4, which is overlapped with ORF3, and 1 origin (Ori) of replication located between ORF1 and ORF2. The chimeric PCV1-2, containing the PCV2 capsid, PCV1 rep, and Ori genes, is attenuated in pigs. In order to verify the role of the Rep gene or Ori in the virulence of PCV2, 3 chimeric viruses [PCV2b-Ori1 (PCV1 Ori gene cloned into the backbone of PCV2b), PCV2b-rep1 (PCV1 Rep gene cloned into the backbone of PCV2b), and PCV2b-rep1-Ori1 (PCV1 Rep and Ori genes cloned into the backbone of PCV2b)] and 2 wild-type recombinant PCV2b and PCV1 were constructed and identified. The experimental results in piglets showed that clinical symptoms, viremia, viral load, lesions in lymphoid and lung tissues, and IL-10 and TNF-α expression levels in PBMCs in the PCV2b-rep1-Ori1 and PCV2b-rep1 groups were significantly decreased, compared to PCV2-infected piglets. Meanwhile, histological lesions of lymphoid and lung tissues, viral loads in lymphoid tissues, viremia, and TNF-α expression in PBMCs were not significantly different between groups PCV2b-Ori1 and PCV2b, suggesting that the Rep gene (ORF1) likely contributes to viral pathogenicity in vivo.
authors: Key Laboratory of Animal Diseases Diagnostic and Immunology, Ministry of Agriculture, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China.
authors: Tao
authors: T
authors: Hua
authors: Xianwei
authors: X
authors: Wang
authors: Juan
authors: J
authors: Bai
authors: Lili
authors: L
authors: Zhang
authors: Jie
authors: J
authors: Liu
authors: Ping
authors: P
authors: Jiang
mesh_terms: D000818:Animals; D001769:Blood / Q000821:virology; D018173:Circoviridae Infections / Q000473:pathology / Q000821:virology; D017925:Circovirus / Q000235:genetics* / Q000472:pathogenicity*; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics; D006651:Histocytochemistry; D016753:Interleukin-10 / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000276:immunology; D008168:Lung / Q000821:virology; D008221:Lymphoid Tissue / Q000821:virology; D008853:Microscopy; D008969:Molecular Sequence Data; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA; D013552:Swine; D013553:Swine Diseases / Q000473:pathology / Q000821:virology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D019562:Viral Load; D014764:Viral Proteins / Q000235:genetics* / Q000378:metabolism*; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics* / Q000378:metabolism*
chemical_list: D004279:DNA, Viral; D014409:Tumor Necrosis Factor-alpha; D014764:Viral Proteins; D037521:Virulence Factors; D016753:Interleukin-10