PMID- 29321316 OWN - NLM STAT- MEDLINE DCOM- 20180417 LR - 20181113 IS - 1098-5514 (Electronic) IS - 0022-538X (Print) IS - 0022-538X (Linking) VI - 92 IP - 7 DP - 2018 Apr 1 TI - Two Residues in NSP9 Contribute to the Enhanced Replication and Pathogenicity of Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus. LID - 10.1128/JVI.02209-17 [doi] LID - e02209-17 AB - Highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) possesses greater replicative capacity and pathogenicity than classical PRRSV. However, the factors that lead to enhanced replication and pathogenicity remain unclear. In our study, an alignment of all available full-length sequences of North American-type PRRSVs (n = 204) revealed two consistent amino acid mutations that differed between HP-PRRSV and classical PRRSV and were located at positions 519 and 544 in nonstructural protein 9. Next, a series of mutant viruses with either single or double amino acid replacements were generated from HP-PRRSV HuN4 and classical PRRSV CH-1a infectious cDNA clones. Deletion of either of the amino acids led to a complete loss of virus viability. In both Marc-145 and porcine alveolar macrophages, the replicative efficiencies of mutant viruses based on HuN4 were reduced compared to the parent, whereas the replication level of CH-1a-derived mutant viruses was increased. Plaque growth assays showed clear differences between mutant and parental viruses. In infected piglets, the pathogenicity of HuN4-derived mutant viruses, assessed through clinical symptoms, viral load in sera, histopathology examination, and thymus atrophy, was reduced. Our results indicate that the amino acids at positions 519 and 544 in NSP9 are involved in the replication efficiency of HP-PRRSV and contribute to enhanced pathogenicity. This study is the first to identify specific amino acids involved in PRRSV replication or pathogenicity. These findings will contribute to understanding the molecular mechanisms of PRRSV replication and pathogenicity, leading to better therapeutic and prognostic options to combat the virus.IMPORTANCE Porcine reproductive and respiratory syndrome (PRRS), caused by porcine reproductive and respiratory syndrome virus (PRRSV), is a significant threat to the global pig industry. Highly pathogenic PRRSV (HP-PRRSV) first emerged in China in 2006 and has subsequently spread across Asia, causing considerable damage to local economies. HP-PRRSV strains possess a greater replication capacity and higher pathogenicity than classical PRRSV strains, although the mechanisms that underlie these characteristics are unclear. In the present study, we identified two mutations in HP-PRRSV strains that distinguish them from classical PRRSV strains. Further experiments that swapped the two mutations in an HP-PRRSV strain and a classical PRRSV strain demonstrated that they are involved in the replication efficiency of the virus and its virulence. Our findings have important implications for understanding the molecular mechanisms of PRRSV replication and pathogenicity and also provide new avenues of research for the study of other viruses. CI - Copyright (c) 2018 American Society for Microbiology. FAU - Zhao, Kuan AU - Zhao K AD - State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China. FAU - Gao, Jia-Cong AU - Gao JC AD - State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China. FAU - Xiong, Jun-Yao AU - Xiong JY AD - State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China. FAU - Guo, Jin-Chao AU - Guo JC AD - State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China. FAU - Yang, Yong-Bo AU - Yang YB AD - State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China. FAU - Jiang, Cheng-Gang AU - Jiang CG AD - State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China. FAU - Tang, Yan-Dong AU - Tang YD AD - State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China. FAU - Tian, Zhi-Jun AU - Tian ZJ AD - State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China. FAU - Cai, Xue-Hui AU - Cai XH AD - State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China. FAU - Tong, Guang-Zhi AU - Tong GZ AD - Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China. FAU - An, Tong-Qing AU - An TQ AD - State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China antongqing@caas.cn. LA - eng PT - Journal Article PT - Research Support, Non-U.S. Gov't DEP - 20180314 PL - United States TA - J Virol JT - Journal of virology JID - 0113724 RN - 0 (Viral Nonstructural Proteins) SB - IM MH - Amino Acid Substitution MH - Animals MH - Cell Line MH - *Mutation, Missense MH - *Porcine Reproductive and Respiratory Syndrome/genetics/metabolism/pathology MH - *Porcine respiratory and reproductive syndrome virus/pathogenicity/physiology MH - Swine MH - *Viral Nonstructural Proteins/genetics/metabolism MH - Virus Replication/*genetics PMC - PMC5972891 OTO - NOTNLM OT - highly pathogenic PRRSV OT - mutation OT - pathogenicity OT - replication OT - residue EDAT- 2018/01/13 06:00 MHDA- 2018/04/18 06:00 PMCR- 2018/09/14 CRDT- 2018/01/12 06:00 PHST- 2017/12/29 00:00 [received] PHST- 2018/01/02 00:00 [accepted] PHST- 2018/01/13 06:00 [pubmed] PHST- 2018/04/18 06:00 [medline] PHST- 2018/01/12 06:00 [entrez] PHST- 2018/09/14 00:00 [pmc-release] AID - JVI.02209-17 [pii] AID - 02209-17 [pii] AID - 10.1128/JVI.02209-17 [doi] PST - epublish SO - J Virol. 2018 Mar 14;92(7):e02209-17. doi: 10.1128/JVI.02209-17. Print 2018 Apr 1.