Fitness Costs and the Rapid Spread of kelch13-C580Y Substitutions Conferring Artemisinin Resistance
Fitness Costs and the Rapid Spread of kelch13-C580Y Substitutions Conferring Artemisinin Resistance
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DOI：
10.1128/aac.00605-18
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发表时间：
2018-09-01
影响因子：
4.9
通讯作者：
Anderson, Tim J. C.
中科院分区：
文献类型：
--
作者：
Nair, Shalini;Li, Xue;Anderson, Tim J. C.
适应性成本是耐药性等位基因是否建立以及它们在人群中传播速度的关键决定因素。在过去15年中，在青蒿素选择下，东南亚疟疾寄生虫（恶性疟原虫）种群中出现了超过125个不同的kelch13等位基因，每个等位基因含有一个不同的氨基酸取代，这是软选择事件的一个戏剧性例子。然而，在多个不同的国家，只有其中一个等位基因（C580Y）在竞争中战胜了其他等位基因，并正在向固定方向扩散。在这里，我们研究了C580Y的适应度后果，相对于另一个不太成功的kelch13突变（R561H），试图解释C580Y的独特动态。我们假设在没有青蒿素治疗的情况下，C580Y将比其他kelch13取代体显示更低的适应度成本。我们使用CRISPR/Cas9方法将单个突变（C580Y或R561H）或同义对照编辑引入到泰国-缅甸边境分离的野生型寄生虫中，进行了重复的头对头竞争分析，并使用kelch13扩增子的深度测序确定了竞争结果。与我们的预测相反，这些实验表明C580Y比R561H具有更高的适合度成本（s[选择系数]= 0.15 +/- 0.008[1标准误差{SE}]） （s = 0.084 +/- 0.005）。R561H在直接竞争中优于C580Y （s = 0.065 +/- 0.004）。我们得出结论，C580Y单独的适应度成本不太可能解释这种替代的快速传播。
Fitness costs are key determinants of whether drug resistance alleles establish and how fast they spread within populations. More than 125 different kelch13 alleles, each containing a different amino acid substitution, have arisen in Southeast Asian malaria parasite (Plasmodium falciparum) populations under artemisinin selection over the past 15 years in a dramatic example of a soft selective event. However, just one of these alleles (C580Y) is now outcompeting other alleles in multiple different countries and is spreading toward fixation. Here we examine the fitness consequences of C580Y, relative to another less successful kelch13 mutation (R561H), to try to explain the distinctive dynamics of C580Y. We hypothesized that C580Y will show lower fitness costs than other kelch13 substitutions in the absence of artemisinin treatment. We used CRISPR/Cas9 methods to introduce single mutations (C580Y or R561H) or synonymous control edits into a wild-type parasite isolated on the Thailand-Myanmar border, conducted replicated head-to-head competition assays, and determined the outcome of competition using deep sequencing of kelch13 amplicons. Contrary to our predictions, these experiments reveal that C580Y carries higher fitness costs (s [selection coefficient] = 0.15 +/- 0.008 [1 standard error {SE}]) than R561H (s = 0.084 +/- 0.005). Furthermore, R561H outcompetes C580Y in direct competition (s = 0.065 +/- 0.004). We conclude that fitness costs of C580Y in isolation are unlikely to explain the rapid spread of this substitution.