UEI Biologia Molecular, UEI Malária, Centro de Malária e Outras Doenças Tropicais/IHMT/UNL, Lisbon, Portugal.
PLoS One. 2010 Jul 15;5(7):e11593. doi: 10.1371/journal.pone.0011593.
Lacking suitable alternatives, the control of malaria increasingly depends upon Artemisinin Combination Treatments (ACT): resistance to these drugs would therefore be disastrous. For ACTs, the biology of resistance to the individual components has been investigated, but experimentally induced resistance to component drugs in combination has not been generated.
METHODOLOGY/PRINCIPAL FINDINGS: We have used the rodent malaria parasite Plasmodium chabaudi to select in vivo resistance to the artesunate (ATN)+mefloquine (MF) version of ACT, through prolonged exposure of parasites to both drugs over many generations. The selection procedure was carried out over twenty-seven consecutive sub-inoculations under increasing ATN+MF doses, after which a genetically stable resistant parasite, AS-ATNMF1, was cloned. AS-ATNMF1 showed increased resistance to ATN+MF treatment and to artesunate or mefloquine administered separately. Investigation of candidate genes revealed an mdr1 duplication in the resistant parasites and increased levels of mdr1 transcripts and protein. There were no point mutations in the atpase6 or ubp1genes.
Resistance to ACTs may evolve even when the two drugs within the combination are taken simultaneously and amplification of the mdr1 gene may contribute to this phenotype. However, we propose that other gene(s), as yet unidentified, are likely to be involved.
由于缺乏合适的替代品，疟疾的控制越来越依赖于青蒿素联合疗法（ACT）：因此，对这些药物产生抗药性将是灾难性的。对于 ACT，已经研究了对个别成分产生抗药性的生物学，但尚未产生对联合用药成分的实验诱导抗药性。
方法/主要发现：我们使用啮齿动物疟原虫 Plasmodium chabaudi 来选择体内对青蒿琥酯（ATN）+甲氟喹（MF）版 ACT 的耐药性，通过在许多代中长时间暴露于两种药物来选择。选择程序在连续 27 次亚接种中进行，逐渐增加 ATN+MF 剂量，然后克隆出遗传稳定的耐药寄生虫 AS-ATNMF1。AS-ATNMF1 对 ATN+MF 治疗以及单独给予青蒿琥酯或甲氟喹表现出更强的耐药性。对候选基因的研究表明，耐药寄生虫中存在 mdr1 基因重复，以及 mdr1 转录本和蛋白水平增加。atpase6 或 ubp1 基因没有点突变。
即使组合中的两种药物同时服用，ACT 的耐药性也可能会进化，并且 mdr1 基因的扩增可能促成这种表型。然而，我们提出可能涉及其他尚未确定的基因。
