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Emergence of Different Recombinant Porcine Reproductive and Respiratory Syndrome Viruses, China.

ABSTRACT: Epidemiological investigations were conducted on recently emerging porcine reproductive and respiratory syndrome virus (PRRSV) strains in Shandong province in 2014-2015. The proportion of the NADC30 strain identified by ORF7 sequence alignment has been gradually increasing. Three emerging PRRSV strains were successfully isolated, and the complete genomic sequences were determined. Our results indicate the importance of recombinant strains in Shandong province, China. There was a varied degree of recombination of two or three strains (classical, HP-PRRSV and/or NADC30). Moreover, the recombination strains affected the pathogenicity of newly emerged strains.

SUBMITTER: Liu Y

PROVIDER: S-EPMC5841431 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

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Emergence of Different Recombinant Porcine Reproductive and Respiratory Syndrome Viruses, China.

Liu Yanyan Y Li Jianda J Yang Jie J Zeng Hao H Guo Lihui L Ren Sufang S Sun Wenbo W Chen Zhi Z Cong Xiaoyan X Shi Jianli J Chen Lei L Du Yijun Y Li Jun J Wang Jinbao J Wu Jiaqiang J Yu Jiang J

Scientific reports 20180307 1

Epidemiological investigations were conducted on recently emerging porcine reproductive and respiratory syndrome virus (PRRSV) strains in Shandong province in 2014-2015. The proportion of the NADC30 strain identified by ORF7 sequence alignment has been gradually increasing. Three emerging PRRSV strains were successfully isolated, and the complete genomic sequences were determined. Our results indicate the importance of recombinant strains in Shandong province, China. There was a varied degree of ...[more]

PMID: 29515183

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Project description:Since its recent appearance in China, the NADC30-like strains of porcine reproductive and respiratory syndrome virus 2 (PRRSV-2) have caused an expanding epidemic, and this has further expanded the genetic diversity of PRRSV. In this study, three NADC30-like strains-GXFCG20210401, GXQZ20210403 and GXNN20210506-were isolated from pig serum samples obtained in Guangxi, and their genomes were sequenced. A comparative analysis of the whole genomes showed that the three strains were most similar to NADC30 (88.3-88.7%). In particular, the non-structural protein coding regions (nsp1, nsp4-5, nsp7-8 and nsp9) showed the highest similarities to JXA1, and the ORF2a-ORF5 regions showed the highest similarities to NADC34. The three strains had same discontinuous deletions of 111+1+19 amino acids in the nsp2 region, which were similar to the NADC30-like strains. Phylogenetic tree analysis based on the ORF5 gene showed that the three PRRSV isolates were divided into lineage 1.5 along with the representative NADC34-like strains, but they were classified as NADC30-like strains with respect to the whole genome and nsp2 evolutionary trees. Recombinant analysis revealed complex recombination patterns in the genomes of the three strains, which likely originated from multiple recombination events among JXA1-like, NADC30-like and NADC34-like strains. The results from animal experiments showed that the GXQZ20210403 strain was 20% lethal to piglets and caused more severe clinical reactions than GXFCG20210401, and both recombinant strains were similar in terms of pathogenicity to the previously reported NADC34 strains. This study demonstrates that NADC34-like strains of PRRSV have been circulating in the southern provinces of China and have exchanged genomes with several other indigenous strains. In addition, differences in recombination patterns may cause different clinical pathogenicity and indicate the importance of the surveillance and preventive control of recombinant strains.

Project description:Porcine reproductive and respiratory syndrome virus (PRRSV) can subvert early innate immunity, which leads to ineffective antimicrobial responses. Overcoming immune subversion is critical for developing vaccines and other measures to control this devastating swine virus. The overall goal of this work was to enhance innate and adaptive immunity following vaccination through the expression of interferon (IFN) genes by the PRRSV genome. We have constructed a series of recombinant PRRS viruses using an infectious PRRSV cDNA clone (pCMV-P129). Coding regions of exogenous genes, which included Renilla luciferase (Rluc), green and red fluorescent proteins (GFP and DsRed, respectively) and several interferons (IFNs), were constructed and expressed through a unique subgenomic mRNA placed between ORF1b and ORF2 of the PRRSV infectious clone. The constructs, which expressed Rluc, GFP, DsRed, efficiently produced progeny viruses and mimicked the parental virus in both MARC-145 cells and porcine macrophages. In contrast, replication of IFN-expressing viruses was attenuated, similar to the level of replication observed after the addition of exogenous IFN. Furthermore, the IFN expressing viruses inhibited the replication of a second PRRS virus co-transfected or co-infected. Inhibition by the different IFN subtypes corresponded to their anti-PRRSV activity, i.e., IFNω5 ° IFNα1 > IFN-β > IFNδ3. In summary, the indicator-expressing viruses provided an efficient means for real-time monitoring of viral replication thus allowing high‑throughput elucidation of the role of host factors in PRRSV infection. This was shown when they were used to clearly demonstrate the involvement of tumor susceptibility gene 101 (TSG101) in the early stage of PRRSV infection. In addition, replication‑competent IFN-expressing viruses may be good candidates for development of modified live virus (MLV) vaccines, which are capable of reversing subverted innate immune responses and may induce more effective adaptive immunity against PRRSV infection.

Project description:BackgroundWe examined differences in pathogenicity in pigs from China that had been experimentally infected with porcine reproductive and respiratory syndrome virus (PRRSV).MethodsWe compared pathogenic characteristics of a field isolate (GX-1/2008F), two PRRSV isolates (HN-1/2008, YN-1/2008) propagated in cells, and GX-1/2008F that had been propagated in cells (GX-1/2008). The clinical courses, along with humoral and cell-mediated responses, were monitored for 21 days post-infection (DPI). Animals were sacrificed and tissue samples used for gross pathological, histopathological and ultrastructure examination.ResultsAt 2-3 DPI, animals infected with cell-propagated viruses exhibited signs of coughing, anorexia and fever. However their rectal temperature did not exceed 40.5°C. Viremia was detectable as early as 3 DPI in animals infected with HN-1/2008 and YN-1/2008. Animals inoculated with GX-1/2008F displayed clinical signs at 6 DPI; the rectal temperature of two animals in this group exceeded 41.0°C, with viremia first detected at 7 DPI. Seroconversion for all challenged pigs, except those infected with GX-1/2008, was seen as early as 7 DPI. All of these pigs had fully seroconverted by 11 DPI. All animals challenged with GX-1/2008 remained seronegative until the end of the experiment. Innate immunity was inhibited, with levels of IFN-α and IL-1 not significantly different between control and infected animals. The cytokines IFN-γ and IL-6 transiently increased during acute infection. All virus strains caused gross lesions including multifocal interstitial pneumonia and hyperplasia of lymph nodes. Inflammation of the stomach and small intestine was also observed. Lesions in the group infected with GX-1/2008F were more serious than in other groups. Transmission electron microscopy revealed that alveolar macrophages, plasmacytes and lymphocytes had fractured cytomembranes, and hepatocytes had disrupted organelles and swollen mitochondria.ConclusionsThe pathogenicity of the PRRSV field isolate became attenuated when propagated in MARC-145 cells. Tissue tropism of highly pathogenic strains prevailing in China was altered compared with classical PRRSV strains. The observed damage to immune cells and modulation of cytokine production could be mechanisms that PRRSV employs to evade host immune responses.

Dataset Information

Emergence of Different Recombinant Porcine Reproductive and Respiratory Syndrome Viruses, China.

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Emergence of Different Recombinant Porcine Reproductive and Respiratory Syndrome Viruses, China.

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