Entomology Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.
Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
PLoS One. 2019 Jan 30;14(1):e0210586. doi: 10.1371/journal.pone.0210586. eCollection 2019.
Decades of unmanaged insecticide use and routine exposure to agrochemicals have left many populations of malaria vectors in the Americas resistant to multiple classes of insecticides, including pyrethroids. The molecular basis of pyrethroid resistance is relatively uncharacterised in American malaria vectors, preventing the design of suitable resistance management strategies. Using whole transcriptome sequencing, we characterized the mechanisms of pyrethroid resistance in Anopheles albimanus from Peru and Guatemala. An. albimanus were phenotyped as either deltamethrin or alpha-cypermethrin resistant. RNA from 1) resistant, 2) unexposed, and 3) a susceptible laboratory strain of An. albimanus was sequenced and analyzed using RNA-Seq. Expression profiles of the three groups were compared based on the current annotation of the An. albimanus reference genome. Several candidate genes associated with pyrethroid resistance in other malaria vectors were found to be overexpressed in resistant An. albimanus. In addition, gene ontology terms related to serine-type endopeptidase activity, extracellular activity and chitin metabolic process were also commonly overexpressed in the field caught resistant and unexposed samples from both Peru and Guatemala when compared to the susceptible strain. The cytochrome P450 CYP9K1 was overexpressed 14x in deltamethrin and 8x in alpha-cypermethrin-resistant samples from Peru and 2x in deltamethrin-resistant samples from Guatemala, relative to the susceptible laboratory strain. CYP6P5 was overexpressed 68x in deltamethrin-resistant samples from Peru but not in deltamethrin-resistant samples from Guatemala. When comparing overexpressed genes between deltamethrin-resistant and alpha-cypermethrin-resistant samples from Peru, a single P450 gene, CYP4C26, was overexpressed 9.8x (p<0.05) in alpha-cypermethrin-resistant samples. In Peruvian deltamethrin-resistant samples, the knockdown resistance mutation (kdr) variant alleles at position 1014 were rare, with approximately 5% frequency, but in the alpha-cypermethrin-resistant samples, the frequency of these alleles was approximately 15-30%. Functional validation of the candidate genes and the kdr mutation as a resistance marker for alpha-cypermethrin will confirm the role of these mechanisms in conferring pyrethroid resistance.
几十年来，杀虫剂的管理不善和常规使用以及常规接触农用化学品，使得美洲的许多疟疾传播媒介种群对包括拟除虫菊酯在内的多类杀虫剂产生了抗药性。在美洲的疟疾传播媒介中，拟除虫菊酯抗性的分子基础尚未得到充分描述，这阻碍了合适的抗性管理策略的设计。本研究使用全转录组测序，对来自秘鲁和危地马拉的致倦库蚊的拟除虫菊酯抗性机制进行了表征。致倦库蚊被表型鉴定为对溴氰菊酯或α-氯氰菊酯具有抗性。对 1) 抗性、2) 未暴露和 3) 实验室敏感株的致倦库蚊进行了 RNA 测序，并使用 RNA-Seq 进行了分析。基于致倦库蚊参考基因组的当前注释，比较了三组的表达谱。在其他疟疾传播媒介中与拟除虫菊酯抗性相关的几个候选基因在抗性致倦库蚊中表达过高。此外，与敏感株相比，来自秘鲁和危地马拉的野外捕获的抗性和未暴露样本中，与丝氨酸内肽酶活性、细胞外活性和几丁质代谢过程相关的基因本体论术语也普遍过表达。在来自秘鲁的溴氰菊酯和α-氯氰菊酯抗性样本中，细胞色素 P450 CYP9K1 分别过表达 14 倍和 8 倍，而在来自危地马拉的溴氰菊酯抗性样本中过表达 2 倍，与实验室敏感株相比。在来自秘鲁的溴氰菊酯抗性样本中，CYP6P5 过表达 68 倍，但在来自秘鲁的溴氰菊酯抗性样本中未过表达。在比较来自秘鲁的溴氰菊酯抗性和α-氯氰菊酯抗性样本中过表达的基因时，单个 P450 基因 CYP4C26 在α-氯氰菊酯抗性样本中过表达 9.8 倍（p<0.05）。在秘鲁的溴氰菊酯抗性样本中，位置 1014 的击倒抗性突变（kdr）变异等位基因的频率约为 5%，但在α-氯氰菊酯抗性样本中，这些等位基因的频率约为 15-30%。候选基因和 kdr 突变作为α-氯氰菊酯抗性标记的功能验证将确认这些机制在赋予拟除虫菊酯抗性方面的作用。
