Short communicationPhylogenetic analysis and molecular characteristics of 17 porcine reproductive and respiratory syndrome virus isolates in Southern China from 2010 to 2011
Introduction
Porcine reproductive and respiratory syndrome (PRRS) has been commonly regarded as one of the most severe diseases in pigs, and it has resulted in unprecedented economic losses [5]. It was first identified in the United States in 1987, then in Europe in 1990, and later in China in 1995. However, a highly pathogenic strain of PRRSV (HP-PRRSV) with a unique 30-amino acid deletion within its Nsp2-coding region was isolated from diseased piglets in China which caused enormous economic losses since 2006 [13]. Its causative agent, porcine reproductive and respiratory syndrome virus (PRRSV) not only causes reproductive failure in sows and gilts, but also triggers complex respiratory problem in pigs of all ages [5]. At present, all PRRSV isolates are divided into two different genotypes: genotype 1 and genotype 2 which were formally called European genotype, (EU genotype) and North American genotype, (NA genotype) respectively [10].
PRRSV, a member of the family Arteriviridae, genus Arterivirus, is a small enveloped virus with a single-strand, positive-sense RNA genome of about 15 kb that includes ten open reading frames: ORF1a, ORF1b, ORF2a, ORF2b, ORF3, ORF4, ORF5, ORF5a, ORF6 and ORF7 [3], [6], [14]. ORF1a and ORF1b constitute about 75% of the entire genome and they are translated through ribosomal frame shifting, leading to the formation of two polyproteins, pp1a and pp1b, which by autocatalytic cleavage generates approximately 14 nonstructural proteins and several intermediate proteins [9].
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Materials and methods
To have a better understanding of the pandemic situation of PRRSV in Southern China, thousands of clinical samples were collected based on the geographical distribution that covered almost the whole of Guangdong province during 2010 and 2011,and 300 positive cases of highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) were identified by RT-PCR and virus isolation. Virus isolation was performed by inoculating MARC-145 cells according to the previously description [19]
Results and discussion
Further sequence analysis revealed that these isolates from 2010 to 2011 belonged to the NA genotype. These isolates were compared with representative strains as follows: VR-2332 for the North American genotype, LV for the European genotype, CH-1a (the representative strain of classic PRRSV in China) and JXA1 (the representative strain of HP-PRRSV from China in 2006), which contains a 30-aa deletion in Nsp2 coding regions, and 07QN isolated from Vietnam. The nucleotide similarity analysis
Acknowledgments
We thank Dr. Shuo Su of the South China Agricultural University for for his contributions in the research design and technical editing assistance.
This work was supported by the National Natural Science Foundation (Grant No. 31272564) and the Guangdong Provincial Natural Science Foundation, China (U0931003) and Modern Agro-industry Technology Research System (CARS-36).
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Equally contributed authors.