Evolution of porcine reproductive and respiratory syndrome virus during sequential passages in pigs
Evolution of porcine reproductive and respiratory syndrome virus during sequential passages in pigs
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DOI：
10.1128/jvi.76.10.4750-4763.2002
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发表时间：
2002-05-01
影响因子：
5.4
通讯作者：
Murtaugh, MP
中科院分区：
文献类型：
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作者：
Chang, CC;Yoon, KJ;Murtaugh, MP
猪繁殖与呼吸综合征（PRRS）病毒被认为具有高度的遗传和抗原变异性。病毒多样性导致了关于病毒突变与宿主持续感染之间的关联的问题，并引起了对保护性免疫、诊断测定检测新变体的能力以及可能出现的强毒株的关注。本研究的目的是描述在实验条件下猪繁殖过程中PRRS病毒的持续变化。用源自北美PRRS病毒原型VR-2332的噬斑克隆病毒接种动物。通过以60天的间隔将病毒从猪传至猪，将三个独立的体内复制系维持367天。在367天的观察期内，从21头猪中共回收了315株空斑克隆病毒，并通过病毒中和试验、单克隆抗体分析和基因组开放阅读框（ORF）1b（复制酶）、5（主要包膜蛋白）和7（核衣壳）的测序，将其与原始空斑克隆病毒进行比较。在接种后第7天检测到变异体，并且在观察期内取样的每头猪中同时存在多种变异体。序列分析表明ORFs 1b和7高度保守。相比之下，ORF 5的测序揭示了48个核苷酸变体，其对应于22个氨基酸变体。尽管在本实验条件下未检测到表位变化，但PRRS病毒在感染猪中显示出持续进化，病毒基因组的不同基因经历不同程度的变化。
Porcine reproductive and respiratory syndrome (PRRS) viruses are recognized as possessing a high degree of genetic and antigenic variability. Viral diversity has led to questions regarding the association of virus mutation and persistent infection in the host and has raised concerns vis-a-vis protective immunity, the ability of diagnostic assays to detect novel variants, and the possible emergence of virulent strains. The purpose of this study was to describe ongoing changes in PRRS virus during replication in pigs under experimental conditions. Animals were inoculated with a plaque-cloned virus derived from VR-2332, the North American PRRS virus prototype. Three independent lines of in vivo replication were maintained for 367 days by pig-to-pig passage of virus at 60-day intervals. A total of 315 plaque-cloned viruses were recovered from 21 pigs over the 367-day observation period and compared to the original plaque-cloned virus by virus neutralization assay, monoclonal antibody analysis, and sequencing of open reading frames (ORFs) 1b (replicase), 5 (major envelope protein), and 7 (nucleocapsid) of the genome. Variants were detected by day 7 postinoculation, and multiple variants were present concurrently in every pig sampled over the observation period. Sequence analysis showed ORFs 1b and 7 to be highly conserved. In contrast, sequencing of ORF 5 disclosed 48 nucleotide variants which corresponded to 22 amino acid variants. Although no epitopic changes were detected under the conditions of this experiment, PRRS virus was shown to evolve continuously in infected pigs, with different genes of the viral genome undergoing various degrees of change.