1Yoon KJ. , Wu LL. , Zimmerman JJ. , et al. Field isolates of porcine reproductive and respiratory syndrome virus (PRRSV) vary in their susceptibility to antibody dependent enhancement (ADE) of infection[J]. Veterinary Microbiology, 1997, 55 (1 4) :277-287.
2Wu WH. , Fang Y. , Farwell R. ,et al. A 10-kDa structural pro rein of porcine reproductive and respiratory syndrome virus encoded byORF2b[J]. Virology, 2001, 287(1):183-191.
3Pirzadeh B. , Dea S.. Immune response in pigs vaccinated with plasmid DNA encoding ORF5 of porcine reproductive and respiratory syndrome virus[J]. Journal of General Virology, 1998, 79 (Pt 5) :989-999.
4Wesley RD. , Mengeling WL. , Lager KM. ,et al. Differentiation of a porcine reproductive and respiratory syndrome virus vaccine strain from North American field strains by restriction fragment length polymorphism analysis of ORF 5[J]. Journal of Veterinary Diagnostic Investigation, 1998, 10(2):140-144.
6Mondaea-Fernandez E. , Murtaugh MP, , Morrison RB.. Association between genetic sequence homology of Porcine reproductive and respiratory syndrome virus and geographic distance between pig sites[J]. Canadian Journal of Veterinary Research, 2006, 70(3) :237-239.
2Key K F, Haqshenas G, Guenette D K, et al. Genetic variation and phylogenetic analysis of the ORF5 gene of acute porcine reproductive and respiratory syndrome virus isolates[J]. Vet Microbiol,2001,83 :249-263.
3Kegong T, Xiuling Y, Tiezhu Z, et al. Emergence of fatal PRRSV variants: unparalleled outbreaks of atypical PRRS in China and molecular dissection of the unique hallmark[J]. Plos One, 2007,6 : 1-10.
4Kapur V, Elam M R, Pawlovich T M, et al. Genetic variation in porcine reproductive and respiratory syndrome virus isolates in the Mid-western United States [J]. Gen Virol, 1996, 77 1271-1276.
5J un H, Gongping P, Yue W, et al. Identification of nonessential regions of the nsp2 replicase protein of porcine reproductive and respiratory syndrome virus strain VR-2332 for replication in cell culture[J]. Virology, 2007, 18:9878-9890.
6Wesley R D, Mengelong W L, Lager K M, et al. Differentiation of porcine reproductive and respiratory syndrome virus vaccine strain from North America field strains by restriction fragment length polymorphism analysis of ORF5 [J] . Vet Diagn Invest, 1998, 10z 140-144.
7Larochelle R, D'Allaire S, Magar R. Molecular epidemiology of porcine reproductive and respiratory syndrome virus (PRRSV) in Quebec[J]. Virus Research, 2003, 96,3-14.
8Mengeling W L, Vorwaid A C, Large K M, et al. Comparison among strains of porcine reproductive and respiratory syndrome virus for their ability to cause reproductive failure[J].Am Vet Rest 1996,57:834-839.
9Andreyer V G, Wesley R D, Mengelong W L, et al. Genetic variation and phylogenetic relationships of 22 porcine reproductive and respiratory syndrome virus (PRRSV) field strain based on sequence analysis of reading frame 5[J]. Arch Virol, 1997, 142:993-1001.
10Cai H Y, Alexander H, Carman S, et al. Restriction fragment length polymorphism of porcine reproductive and respiratory syndrome virus recovered from Ontario farms, 1998- 2002[J]. Vet Diagn Invest,2002, 14,343-347.
