title: A porcine circovirus type 2 (PCV2) mutant with 234 amino acids in capsid protein showed more virulence in vivo, compared with classical PCV2a/b strain.
abstract: BACKGROUND
  Porcine circovirus type 2 (PCV2) is considered to be the primary causative agent of postweaning multisystemic wasting syndrome (PMWS), which has become a serious economic problem for the swine industry worldwide. The major genotypes, PCV2a and PCV2b, are highly prevalent in the pig population and are present worldwide. However, another newly emerging PCV2b genotype mutant, which has a mutation in its ORF2-encoded capsid protein, has been sporadically present in China, as well as in other countries. It is therefore important to determine the relative virulence of the newly emerging PCV2b genotype mutant, compared with the existing PCV2a and PCV2b genotypes, and to investigate whether the newly emerging mutant virus induces more severe illness.
  
  
  RESULTS
  Twenty healthy, 30-day-old, commercial piglets served as controls or were challenged with PCV2a, PCV2b and the newly emerging mutant virus. A series of indexes representing different parameters were adopted to evaluate virulence, including clinical signs, serological detection, viral load and distribution, changes in immune cell subsets in the peripheral blood, and evaluation of pathological lesions. The newly emerging PCV2 mutant demonstrated more severe signs compatible with PMWS, characterized by wasting, coughing, dyspnea, diarrhea, rough hair-coat and depression. Moreover, the pathological lesions and viremia, as well as the viral loads in lymph nodes, tonsils and spleen, were significantly more severe (P<0.05) for piglets challenged with the newly emerging mutant compared with those in the groups challenged with PCV2a and PCV2b. In addition, a significantly lower average daily weight gain (P<0.05) was recorded in the group challenged with the newly emerging PCV2 mutant than in the groups challenged with the prevailing PCV2a and PCV2b.
  
  
  CONCLUSIONS
  This is believed to be the first report to confirm the enhanced virulence of the newly emerging PCV2 mutant in vivo.
authors: Division of Swine Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China.
authors: Longjun
authors: L
authors: Guo
authors: Yujie
authors: Y
authors: Fu
authors: Yiping
authors: Y
authors: Wang
authors: Yuehua
authors: Y
authors: Lu
authors: Yanwu
authors: Y
authors: Wei
authors: Qinghai
authors: Q
authors: Tang
authors: Peihu
authors: P
authors: Fan
authors: Jianbo
authors: J
authors: Liu
authors: Long
authors: L
authors: Zhang
authors: Feiyan
authors: F
authors: Zhang
authors: Liping
authors: L
authors: Huang
authors: Dan
authors: D
authors: Liu
authors: Shengbin
authors: S
authors: Li
authors: Hongli
authors: H
authors: Wu
authors: Changming
authors: C
authors: Liu
mesh_terms: D000818:Animals; D036022:Capsid Proteins / Q000235:genetics / Q000378:metabolism*; D018173:Circoviridae Infections / Q000235:genetics / Q000821:virology*; D017925:Circovirus / Q000235:genetics* / Q000472:pathogenicity*; D013552:Swine; D013553:Swine Diseases / Q000235:genetics / Q000821:virology; D014774:Virulence / Q000235:genetics*
chemical_list: D036022:Capsid Proteins