Elsevier

Veterinary Microbiology

Volume 147, Issues 3–4, 27 January 2011, Pages 274-282
Veterinary Microbiology

Research article
Complete genomic characterization of a Chinese isolate of porcine reproductive and respiratory syndrome virus

https://doi.org/10.1016/j.vetmic.2010.07.001Get rights and content

Abstract

The genome of one isolate of porcine reproductive and respiratory syndrome virus (PRRSV) from China, designated GDQY2, was sequenced and analyzed. The full length of GDQY2 was 15,215 nucleotides, excluding the poly(A) tail. Comparative analysis with the genomic sequences of numerous worldwide North American isolates revealed that GDQY2 shared 85.0–98.9% identity with these isolates, but only 60.9% with the European virus—LV (Lelystad Virus), indicating that this new Chinese isolate was closely related to the North American PRRSV genotype. Phylogenetic analysis based on the nucleotide sequences of the full length and ORF5 showed that this new isolate belong to the same genetic group with all other Chinese isolates. Comparison with North American PRRSV isolates revealed that GDQY2 exhibited variations in the non-structural protein 2 (NSP2) encoded by ORF1a, namely that an additional 35-amino acid deletion in NSP2 was found in GDQY2. Therefore, GDQY2 was a novel strain with unique deletions. Furthermore, our study demonstrated that North American genotype PRRSVs in China have evolved independently from other countries, indicating that geographic separation might be one factor influencing the molecular evolution of PRRSV.

Introduction

Porcine reproductive and respiratory (PRRS) is one of the widespread swine diseases around the world, which was first reported in America in 1980 (Cho and Dee, 2006) and caused enormous economic losses in the swine industry. It is mainly characterized by reproductive failure in pregnant sows and respiratory distress in young pigs. The causative agent of this disease-porcine reproductive and respiratory virus (PRRSV) was first isolated in Netherland in 1990 (Wensvoort et al., 1991) and shortly after was identified in the United States (Benfield et al., 1992). This virus was mainly divided into European type (type 1) and American type (type 2), and the prototype of which were designated LV and VR-2332, respectively (Cho and Dee, 2006).

PRRSV is an enveloped single-stranded positive-sense RNA virus which belongs to the Arteriviridae family (Cavanagh, 1997) together with equine ateritis virus (EAV), lactate dehydrogenase-elevating virus (LDV) of mice, and simian hemorrhagic fever virus (SHFV). The genome of PRRSV is about 15 kb in length and contains eight open reading frames (ORF1a, ORF1b, ORF2–7), 5′ nontranslated region (UTR) and 3′UTR (Meulenberg et al., 1993). The two large ORFs 1a and 1b cover the 5′ two-thirds of the genome and encode an ORF1ab replicase polyprotein which is proteolytically cleaved into 13 small non-structural proteins, among which NSP2 is the most variable protein and it may be associated with the virus virulence (Bautista et al., 2002, Van Dinten et al., 1999). ORF2–ORF7 code for major structural proteins (GP5, M and N) and minor structural proteins (GP2, GP3 and GP4) (Nielsen et al., 2003). GP5, the major viral envelop protein, is thought to induce virus-neutralizing antibodies (Gonin et al., 1999, Ansari et al., 2006) and is the most variable protein among structural protein (Mardassi et al., 1995, Meng et al., 1995). Although GP3 and NSP2 are also considered to be variable (Oleksiewicz et al., 2000, Fang et al., 2004), their structural and functional properties are less characterized.

Although LV and VR-2332 appeared almost simultaneously on each continent, they cause similar clinical symptoms and share the same virion morphology and genome organization, exhibit distinct and antigenic variations and share only about 60% nucleotide identity at the genome level (Nam et al., 2009). Recently, the intermingling of the two genotypes (type 1 and type 2) has been reported both in Europe and in North America, causing a significant impact on PRRSV diagnostics and management (Dewey et al., 2000, Madsen et al., 1998, Ropp et al., 2004). Also, a recent study indicated that PRRSV strains from several Chinese regions were diverse and could be divided into two major subgroups (An et al., 2007). This study was undertaken to find a possible relationship between genetic variation and pathogenicity of PRRSV isolates in China. The genome of GDQY2, isolated in Guangdong province in 2007 was sequenced and analyzed.

Section snippets

Clinical samples

Lungs and lymph nodes were collected from suspected pigs in Guangdong province of China in 2007. All of these pigs displayed typical symptoms of PRRS, including labored breathing, pyrexia, lethargy and anorexia. Clinical tissues were homogenized for RNA extraction and virus isolation, and the remaining samples were kept at −70 °C.

Virus isolation

Virus isolation from the tissue homogenates was performed in Marc-145 cells maintained in Dulbecco's modified Eagle's medium (DMEM) containing 10% fetal bovine serum

Comparison of full-length genomic sequences of GDQY2 with other strains

The sequence data showed that, excluding the poly(A) tail, the genomic sequence of GDQY2 was 15,215 nucleotides (nt) in length, consisting of a 189-nt 5′UTR, a 14,875-nt protein-coding region containing 8 ORFs, and a 150-nt 3′UTR. The complete nucleotide sequence of GDQY2 was further compared to other PRRSV isolates, including two North American strains (MN184C and VR-2332), one European type strain (LV), one Japanese strain (EDRD-1), one South Korea strain (LMY) and six Chinese isolates

Discussion

PRRS is one of the pandemic diseases in China's major pig-producing areas, which has caused huge economic losses to the pig industry since its emergence. As mid-July of 2007, the disease has been reported in 20 provinces, and more than 20,000 pigs died from the disease in a 2-week period (Zhou et al., 2008). In our study, we determined the complete nucleotide sequence of GDQY2 and analyzed the phylogenetic relationship among PRRSV strains isolated in China and other countries. As expected, a

Conclusion

All together, the data obtained from our study suggest almost all of present PRRSV isolates in China belong to North American type, and high identity could be observed among them. GDQY2 represents a recent emergence of a virus typical for this genotype owning new characterizations. Besides, while developing effective vaccines and establish prevention and control policy for PRRS, the impact of different geographic factors on the viral variation should be considered.

Acknowledgements

This research was supported by the Important Science and Technology Specific Projects of Guangdong Province (2008A020100020) from Guangdong Science and Technology Department of China. We would thank Dr. Lianxiang Wang, Guangdong Wen's Foodstuffs Group Co., Ltd. China, for providing us with animal samples and viruses, and Dr. Shan Zhong Gong at Kansas State University for revision in writing the manuscript.

References (34)

  • C. Wang et al.

    Genetic variation in open reading frame 5 gene of porcine reproductive and respiratory syndrome virus in Taiwan

    Vet. Microbiol.

    (2008)
  • I.H. Ansari et al.

    Influence of N-linked glycosylation of porcine reproductive and respiratory syndrome virus GP5 on virus infectivity, antigenicity, and ability to induce neutralizing antibodies

    J. Virol.

    (2006)
  • D.A. Benfield et al.

    Characterization of swine infertility and respiratory syndrome (SIRS) virus (isolate ATCC VR-2332)

    J. Vet. Diagn. Invest.

    (1992)
  • D. Cavanagh

    Nidoviales: a new order comprising Cornaviridae and Arteriviridae

    Arch. Virol.

    (1997)
  • S. Dea et al.

    Current knowledge on the structural proteins of the structural proteins of porcine reproductive and respiratory syndrome (PRRS) virus: comparison of the North American and European isolates

    Arch. Virol.

    (2000)
  • C. Dewey et al.

    Lelystad-like strain of porcine reproductive and respiratory syndrome virus (PRRSV) identified in Canadian swine

    Can. Vet. J.

    (2000)
  • J.A. den Boon et al.

    Processing and evolution of the N-terminal region of the arterivirus replicase ORF1a protein: identification of two papainlike cysteine proteases

    J. Virol.

    (1995)
  • Cited by (26)

    • Comparison of four commercial PRRSV MLV vaccines in herds with co-circulation of PRRSV-1 and PRRSV-2

      2019, Comparative Immunology, Microbiology and Infectious Diseases
      Citation Excerpt :

      RNA was extracted from lung homogenates. And ORF5 sequence was amplified from cDNA and sequenced as previously described [8,9]. All protocols were previously approved by the Seoul National University Institutional Animal Care and Use Committee.

    • Veterinary Medicine, Eleventh Edition

      2016, Veterinary Medicine, Eleventh Edition
    • Effect of amino acids residues 323-433 and 628-747 in Nsp2 of representative porcine reproductive and respiratory syndrome virus strains on inflammatory response in vitro

      2015, Virus Research
      Citation Excerpt :

      The rescued virus (rBB), and other recombinant viruses were propagated in MARC-145 cells upon recovery, with P5 viruses used in our in vitro experiments. In comparison with the HV2 domain of the prototype strain VR-2332, Nsp2 of certain virulent type 2 PRRSV isolates contains large deletions in this region (Han et al., 2006; Li et al., 2010; Zhu et al., 2011). The virulent PRRSV strain MN184C has three discontinuous deletions of 111, 1, and 19aa in its HV2 domain, corresponding to residues 324–434, 486, and 532–555 of Nsp2, respectively in the VR-2332 strain (Han et al., 2006).

    View all citing articles on Scopus
    View full text