Division of Livestock Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, No. 427 Maduan Street, Harbin 150001, PR China.
Antiviral Res. 2013 Oct;100(1):1-7. doi: 10.1016/j.antiviral.2013.07.008. Epub 2013 Jul 20.
In a screen for RNA mutagen-resistant foot-and-mouth disease virus (FMDV) strains, we isolated an FMDV mutant with RNA-dependent RNA polymerase (RdRp) R84H substitution. This mutant, selected under the mutagenic pressure of 5-fluorouracil (5-FU), is resistant not only to 5-FU but also to other two RNA mutagens, 5-azacytidine and ribavirin, suggesting that the RdRp R84H mutant is a high fidelity variant. Subsequently, the increased fidelity of this mutant was verified through analysis of mutation frequency, which revealed a 1.4-fold enhancement in RdRp fidelity compared with the wild-type virus. Further studies indicated that the R84H mutant exhibited slightly increased fitness in vitro, and its virulence was not reduced in suckling mice. These results indicated that an increase in RdRp fidelity does not always correlate with reduced virus fitness and virus attenuation. Thus, this isolated R84H mutant provides a new platform to examine the evolutionary dynamics of fidelity-changing RNA viruses, such as mutagen resistance, fitness and virulence.
在筛选对 RNA 致突变剂具有抗性的口蹄疫病毒（FMDV）株的实验中，我们分离到了一个 FMDV 突变株，其 RNA 依赖性 RNA 聚合酶（RdRp）的第 84 位氨基酸由精氨酸（Arg）突变为组氨酸（His）。该突变株在 5-氟尿嘧啶（5-FU）的致突变压力下被筛选出来，不仅对 5-FU 具有抗性，而且对其他两种 RNA 致突变剂——5-氮杂胞苷和利巴韦林也具有抗性，这表明 RdRp 的第 84 位氨基酸突变使其成为一个高保真度的变体。随后，通过突变频率分析验证了该突变株的高保真度，结果显示其 RdRp 保真度比野生型病毒提高了 1.4 倍。进一步的研究表明，该突变株在体外具有略微增强的适应性，并且在乳鼠中的毒力并未降低。这些结果表明，RdRp 保真度的提高并不总是与病毒适应性和减毒相关。因此，该分离得到的第 84 位氨基酸突变株为研究 RNA 突变病毒的进化动态提供了一个新的平台，例如致突变抗性、适应性和毒力。
