Due to lacking a proofreading mechanism in their RNA-dependent RNA polymerases (RdRp), RNA viruses generally possess high mutation frequencies, making them evolve rapidly to form viral quasispecies during serial passages in cells, especially treated with mutagens, like ribavirin. Canine distemper virus (CDV) belongs to the genus Morbillivirus. Its L protein functions as an RdRp during viral replication. In this study, a recombinant enhanced green fluorescence protein-tagged CDV (rCDV-eGFP) was rescued from its cDNA clone, followed by viral identification and characterization at passage-7 (P7). This recombinant was independently subjected to extra 40 serial passages (P8 to 47) in ribavirin- and non-treated cells. Two viral progenies, undergoing passages in ribavirin- and non-treated VDS cells, were named rCDV-eGFP-R and -N, respectively. Both progenies were simultaneously subjected to next-generation sequencing (NGS) at P47 for comparing their quasispecies diversities with each other. The rCDV-eGFP-R and -N showed 62 and 23 single-nucleotide mutations (SNMs) in individual antigenomes, respectively, suggesting that the ribavirin conferred a mutagenic effect on the rCDV-eGFP-R. The spectrum of 62 SNMs contained 26 missense and 36 silent mutations, and that of 23 SNMs was composed of 17 missense and 6 silent mutations. Neither the rCDV-eGFP-R nor -N exhibited nonsense mutation in individual antigenomes. We speculate that the rCDV-eGFP-R may contain at least one P47 sub-progeny characterized by high-fidelity replication in cells. If such a sub-progeny can be purified from the mutant swarm, its L protein would elucidate a molecular mechanism of CDV high-fidelity replication.

由于其依赖于 RNA 的 RNA 聚合酶 (RdRp) 缺乏校对机制，RNA 病毒通常具有高突变频率，这使得它们在细胞连续传代期间迅速进化形成病毒准种，尤其是用诱变剂处理的病毒，如病毒唑。犬瘟热病毒 (CDV) 属于该属麻疹病毒. 它的 L 蛋白在病毒复制过程中起到 RdRp 的作用。在这项研究中，重组增强型绿色荧光蛋白标记 CDV (rCDV-eGFP) 从其 cDNA 克隆中获救，随后在第 7 代 (P7) 进行病毒鉴定和表征。该重组体在利巴韦林和未处理的细胞中独立进行额外的 40 次连续传代（P8 至 47）。在利巴韦林和未处理的 VDS 细胞中进行传代的两个病毒后代分别被命名为 rCDV-eGFP-R 和 -N。两个后代同时在 P47 进行下一代测序 (NGS)，以比较它们的准种多样性。rCDV-eGFP-R 和 -N 在单个反基因组中分别显示 62 和 23 个单核苷酸突变 (SNM)，表明利巴韦林对 rCDV-eGFP-R 具有致突变作用。62个SNMs的光谱包含26个错义和36个沉默突变，23个SNMs的光谱由17个错义和6个沉默突变组成。rCDV-eGFP-R 和-N 都没有在个体反基因组中表现出无义突变。我们推测 rCDV-eGFP-R 可能包含至少一个 P47 亚后代，其特征在于细胞中的高保真复制。如果可以从突变群中纯化出这样的子后代，其 L 蛋白将阐明 CDV 高保真复制的分子机制。