title: Phylogenetic analysis and molecular characteristics of seven variant Chinese field isolates of PRRSV.
abstract: BACKGROUND
  Porcine reproductive and respiratory syndrome (PRRS) has now been widely recognized as an economically important disease. The objective of this study was to compare the molecular and biological characteristics of porcine reproductive and respiratory syndrome virus (PRRSV) field isolates in China to those of the modified live virus (MLV) PRRS vaccine and its parent strain (ATCC VR2332).
  
  
  RESULTS
  Five genes (GP2, GP3, GP4, GP5 and NSP2) of seven isolates of PRRSV from China, designated LS-4, HM-1, HQ-5, HQ-6, GC-2, GCH-3 and ST-7/2008, were sequenced and analyzed. Phylogenetic analyses based on the nucleotide sequence of the ORF2-5 and NSP2 showed that the seven Chinese isolates belonged to the same genetic subgroup and were related to the North American PRRSV genotype. Comparative analysis with the relevant sequences of another Chinese isolate (BJ-4) and North American (VR2332 and MLV) viruses revealed that these isolates have 80.8-92.9% homology with VR-2332, and 81.3-98.8% identity with MLV and 80.7-92.9% with BJ-4. All Nsp2 nonstructural protein of these seven isolates exhibited variations (a 29 amino acids deletion) in comparison with other North American PRRSV isolates. Therefore, these isolates were novel strain with unique amino acid composition. However, they all share more than 97% identity with other highly pathogenic Chinese PRRSV strains. Additionally, there are extensive amino acid (aa) mutations in the GP5 protein and the Nsp2 protein when compared with the previous isolates.
  
  
  CONCLUSIONS
  These results might be useful to study the genetic diversity of PRRSV in China and to track the infection sources as well as for vaccines development.
authors.affiliation: National Research Center for Wildlife Born Diseases, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Chengmin
authors.initials: C
authors.lastname: Wang
authors.forename: Bin
authors.initials: B
authors.lastname: Wu
authors.forename: Said
authors.initials: S
authors.lastname: Amer
authors.forename: Jing
authors.initials: J
authors.lastname: Luo
authors.forename: Hongmei
authors.initials: H
authors.lastname: Zhang
authors.forename: Yunhai
authors.initials: Y
authors.lastname: Guo
authors.forename: Guoying
authors.initials: G
authors.lastname: Dong
authors.forename: Baohua
authors.initials: B
authors.lastname: Zhao
authors.forename: Hongxuan
authors.initials: H
authors.lastname: He
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002681:China; D016000:Cluster Analysis; D005814:Genes, Viral; D005838:Genotype; D008969:Molecular Sequence Data; D010802:Phylogeny; D011110:Polymorphism, Genetic; D019318:Porcine Reproductive and Respiratory Syndrome / Q000821:virology*; D019316:Porcine respiratory and reproductive syndrome virus / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D013552:Swine / Q000821:virology*