Complete genome sequence of an overattenuated highly pathogenic porcine reproductive and respiratory syndrome virus

JXA1-P170 is an overattenuated highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) that has been passaged in vitro 170 times. Vaccination with JXA1-P170 cannot protect pigs against JXA1 challenge. Compared with the parental virus JXA1, JXA1-P170 contains 1 nucleotide (nt) deletion and 113 nt mutations leading to 59 amino acid substitutions. Here we announce the first complete genome sequence of the overattenuated HP-PRRSV.     

Complete genome sequence of porcine reproductive and respiratory syndrome virus isolated from piglet stool samples

WUH4 is a highly pathogenic North American porcine reproductive and respiratory syndrome virus (PRRSV). Unlike previous PRRSV isolates, which were mainly recovered from sera or tissues, WUH4 was isolated from a piglet stool sample. Here we announce its complete genome sequence.     

Complete genome sequence of two novel Chinese virulent porcine reproductive and respiratory syndrome virus variants

A highly pathogenic strain of porcine reproductive and respiratory syndrome virus (PRRSV), characterized by a discontinuous 30-amino-acid deletion in its Nsp2-coding region, has been emerging in China since 2006. Here, we report the complete genomic sequence of two novel Chinese virulent PRRSV variants with additional NSP2-gene deletions, which will help us understand the molecular and evolutionary characteristics of PRRSV in Asia.     

Complete genome sequence of a porcine epidemic diarrhea virus variant

In 2011, outbreaks of viral diarrhea were observed on most swine-breeding farms in most of the provinces of China. The disease is characterized by vomiting, severe diarrhea, and a high mortality rate (82.3%) in newborn piglets. The clinical appearance was similar to that of porcine epidemic diarrhea virus (PEDV) infection. PEDVs were detected in samples (feces or small intestines) from most farms. In order to investigate whether there is a PEDV variant circulating in China, we sequenced and analyzed the complete genome of the recently identified field strain, CH/FJND-3/2011. The sequence data indicate that this PEDV variant prevails in China.     

Complete genome sequence of porcine reproductive and respiratory syndrome virus strain QY2010 reveals a novel subgroup emerging in China

QY2010 is a highly pathogenic North American-type porcine reproductive and respiratory syndrome virus (PRRSV). The complete genome sequence shows that QY2010 shares low sequence identity (60 to 88.7%) to all known PRRSV isolates. Phylogenetic analyses further reveal that QY2010 constitutes a novel subgroup within the North American genotype of PRRSV.     

Biophysical characterisation of the nucleocapsid protein from a highly pathogenic porcine reproductive and respiratory syndrome virus strain

The arterivirus nucleocapsid (N) protein is a multifunctional protein that binds viral RNA for encapsidation and has potential roles in host cell processes. This study characterised the N protein from a highly virulent North American strain of porcine reproductive and respiratory syndrome virus (PRRSV). The association with viral RNA was mapped to defined motifs on the N protein. The results indicated that disulphide bridge formation played a key role in RNA binding, offering an explanation why infectious virus cannot be rescued if cysteine residues are mutated, and that multiple sites may promote RNA binding.     

Molecular characterization of a highly pathogenetic porcine reproductive and respiratory syndrome virus variant in Hubei, China

Porcine reproductive and respiratory syndrome virus (PRRSV) has been recognized as one of the most important pathogens of pigs throughout the world. In 2006, more than 10 provinces of China have experienced an epizootic outbreak of pig diseases characterized by high fever, reddened skin and high morbidity and mortality. From June 2006 to April 2007, we have investigated some clinical samples in Hubei province by RT-PCR and cloned several major genes, N, GP5 and NSP2 gene, shown in this study. Phylogenetic analysis of these genes revealed that the highly pathogenic PRRSV variant, ZB, was responsible for 2006 emergent outbreak of pig disease in Hubei province similar with those variants isolated from other provinces in China in 2006, and belongs to the NA-type PRRSV. In the PRRSV variants, the N and GP5 shear about 90% identity with prototypic ATCC VR-2332 and some typical NA-type Chinese isolates, except the 2850bp NSP2 gene (only shares 65% identity with ATCC VR-2332). But they all shear more than and 97% identity with other highly pathogenetic Chinese PRRSV strains. Additionally, there are extensive amino acid (aa) mutations in the GP5 protein and 2 deletions in the Nsp2 protein when compared with the previous isolates. Most of the variants found in 2006 epizootic outbreak of pig diseases in China were the farthest variants from the typical NA-type PRRSV in phylogenetic distance, and these diversities may be responsible for the differences in the pathogenicity observed between these variants and original Chinese PRRSV strains.     

Complete genome sequence of a highly prevalent isolate of porcine epidemic diarrhea virus in South china

A widespread porcine epidemic diarrhea virus (PEDV) occurred in southern China during 2010 to 2012. A virulent field PEDV strain, GD-B, was isolated from a sucking piglet suffering from severe diarrhea in Guangdong, China. We sequenced and analyzed the complete genome of strain GD-B, which will promote a better understanding of the molecular epidemiology and genetic diversity of PEDV field isolates in southern China.     

高致病性猪繁殖与呼吸综合征病毒TJ株致弱过程中遗传变异和致病性分析

为了研制高致病性猪繁殖与呼吸综合征(HP-PRRS)弱毒疫苗,将高致病性猪繁殖与呼吸综合征病毒(HP-PRRSV)TJ株进行了致弱驯化,在Marc-145细胞上对其进行了连续传代,每5～10代进行噬斑克隆纯化病毒。对致弱过程中不同代次病毒进行遗传变异及致病性分析。结果表明,TJ株在致弱过程中各基因均存在不同程度的变异,至第140代,共有58个氨基酸发生突变,同时在非结构蛋白nsp2区域,在不连续的30个氨基酸缺失(481位和533～561位)之后又出现连续120个氨基酸的缺失,与VR-2332相比,该缺失位点位于推定氨基酸序列的628～747位。动物接种试验结果表明,TJ株经Marc-145细胞传至第20代时,病毒对猪的致病性明显减弱,推测TJ株在这一传代过程中非结构蛋白nsp2-nsp5、nsp7和结构蛋白GP5所发生的遗传变异对病毒毒力致弱起到一定作用。     

猪繁殖与呼吸障碍综合征病毒(PRRSV)3′末端非翻译区中调控序列的研究

以北美株PRRSV感染性克隆pCBC2为平台进行反向遗传操作,将3′UTR中的一级结构进行了系列缺失或插入突变,并改变二级结构中的一个保守的茎环结构,构建全长PRRSV突变体克隆,解析3′UTR突变对病毒感染性的影响,旨在界定调控PRRSV3′UTR的启动子序列及二级结构,即复制过程中的最小调控元件。以空斑和Northern blot来研究拯救后重组病毒的复制、转录和生长特性,发现重组病毒感染动力学与亲本病毒无可见差别。结果表明PRRSV3′UTR的5′端可耐受一定数目的核苷酸的缺失(41nt)与插入(23nt)突变,但进一步9nt缺失造成保守的环结构突变后就使病毒失去了感染性。证明了这是3′UTR中控制PRRSV复制过程的的必需序列及二级结构,为进一步解析PRRSV复制过程的调控元件奠定了基础。     

Complete genome sequence of a Chinese virulent porcine epidemic diarrhea virus strain

CH/S is a virulent porcine epidemic diarrhea virus (PEDV) strain and is used as the virulent strain to evaluate the protection rates of vaccines against PEDV infection in China. Here, we report the complete genome sequence of strain CH/S, which may aid in understanding the molecular characteristics of this strain.     

Complete genome sequence of a novel porcine epidemic diarrhea virus in South china

Since early 2010, outbreaks of porcine epidemic diarrhea (PED) have been observed frequently in immunized swine herds in southern China. The suckling piglets are particularly susceptible to porcine epidemic diarrhea virus (PEDV), with a high mortality rate (90%). Recently, a virulent PEDV strain, GD-A, was isolated from an immunized-swine breeding farm in Guangdong, China. This report describes the complete genome sequence of GD-A, and the data will provide important insights into the variation of PEDV field isolates in southern China.     

Complete genome sequences of porcine reproductive and respiratory syndrome viruses: perspectives on their temporal and spatial dynamics

Porcine reproductive and respiratory syndrome virus (PRRSV) has been investigated extensively at the molecular level. Nevertheless, genome wide study on the temporal and spatial dynamics of the virus is non-existed. To explore this topic, we determined complete coding genome sequences for four PRRSV isolates and analyzed them together with 122 global published ones using the Bayesian coalescent approach as well as Bayesian inferences and maximum likelihood methods. All EU-type viruses belonged to one of two groups or were unclassified (5 isolates), and all NA-type isolates were divided into one of three major groups or were unclassified (1 isolate). Here, there was no apparent association between temporal or geographic origin and heterogeneity of global PRRSVs. Of the eight ORFs, ORF1a showed the most powerful evolutionary signal. Our findings also indicated that the PRRS virus evolved at a rate of 1.98 × 10^?3 substitutions/site/year, and the most recent common ancestor of the virus existed 786.4 years ago. Here, EU-type viruses segregated 115.7 years ago, while NA-type isolates diverged 179.8 years before the present. In addition, our reconstruction of the effective population size depicted five phases of epidemic growth: an initial constant, followed sequentially by slow decrease, slight increase, sharp decline, and then a rapid expansion approaching the present.     

Overview: Replication of porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome virus (PRRSV), an arterivirus that causes significant losses in the pig industry, is one of the most important animal pathogens of global significance. Since the discovery of the virus, significant progress has been made in understanding its epidemiology and transmission, but no adequate control measures are yet available to eliminate infection with this pathogen. The genome replication of PRRSV is required to reproduce, within a few hours of infection, the millions of progeny virions that establish, disseminate, and maintain infection. Replication of the viral RNA genome is a multistep process involving a replication complex that is formed not only from components of viral and cellular origin but also from the viral genomic RNA template; this replication complex is embedded within particular virus-induced membrane vesicles. PRRSV RNA replication is directed by at least 14 replicase proteins that have both common enzymatic activities, including viral RNA polymerase, and also unusual and poorly understood RNA-processing functions. In this review, we summarize our current understanding of PRRSV replication, which is important for developing a successful strategy for the prevention and control of this pathogen.     

Divergence time of porcine reproductive and respiratory syndrome virus subtypes

Porcine reproductive and respiratory syndrome virus (PRRSV) recently emerged in domestic pigs of Western Europe and North America. Although time of emergence was identical on the two continents, genetic composition was markedly different with a clear geographical subtype structure, indicating that subtypes diverged in separate reservoirs prior to emergence. Genetic analyses have shown that the most recent common ancestor (MRCA) of Western European isolates existed around 1980 and that these originate from Eastern European pigs. These findings are challenged by a study of Hanada et al. who place the MRCA of all PRRSV isolates around 1980 and find that no significant subtype divergence occurred before emergence. Here, I discuss problems of information content, methodology, and biological plausibility associated with this study. Using alternative methodology, I reanalyze the existing data and conclude that the MRCA of all PRRSV isolates existed around 1880, 100 years before the date estimated by Hanada et al.     

Complete genome sequence of a novel porcine circovirus-like agent

We report here the genome sequence of a porcine circovirus-like agent. The sequenced genome of this porcine circovirus-like agent is composed of a 648-nucleotide circular DNA that includes three predicted protein-coding genes, which means the agent should be a novel member of the family Circoviridae.