Mukherjee Angana, Bopp Selina, Magistrado Pamela, Wong Wesley, Daniels Rachel, Demas Allison, Schaffner Stephen, Amaratunga Chanaki, Lim Pharath, Dhorda Mehul, Miotto Olivo, Woodrow Charles, Ashley Elizabeth A, Dondorp Arjen M, White Nicholas J, Wirth Dyann, Fairhurst Rick, Volkman Sarah K
Department of Immunology and Infectious Disease, Harvard T.H. Chan School of Public Health, 665 Huntington Avenue, I-704, Boston, MA, 02115, USA.
Infectious Disease Initiative, The Broad Institute of MIT and Harvard, Cambridge, MA, USA.
Malar J. 2017 May 12;16(1):195. doi: 10.1186/s12936-017-1845-5.
Artemisinin resistance is associated with delayed parasite clearance half-life in vivo and correlates with ring-stage survival under dihydroartemisinin in vitro. Both phenotypes are associated with mutations in the PF3D7_1343700 pfkelch13 gene. Recent spread of artemisinin resistance and emerging piperaquine resistance in Southeast Asia show that artemisinin combination therapy, such as dihydroartemisinin-piperaquine, are losing clinical effectiveness, prompting investigation of drug resistance mechanisms and development of strategies to surmount emerging anti-malarial resistance.
Sixty-eight parasites isolates with in vivo clearance data were obtained from two Tracking Resistance to Artemisinin Collaboration study sites in Cambodia, culture-adapted, and genotyped for pfkelch13 and other mutations including pfmdr1 copy number; and the RSA survival rates and response to antimalarial drugs in vitro were measured for 36 of these isolates.
Among these 36 parasites one isolate demonstrated increased ring-stage survival for a PfKelch13 mutation (D584V, RSA = 8%), previously associated with slow clearance but not yet tested in vitro. Several parasites exhibited increased ring-stage survival, yet lack pfkelch13 mutations, and one isolate showed evidence for piperaquine resistance.
This study of 68 culture-adapted Plasmodium falciparum clinical isolates from Cambodia with known clearance values, associated the D584V PfKelch13 mutation with increased ring-stage survival and identified parasites that lack pfkelch13 mutations yet exhibit increased ring-stage survival. These data suggest mutations other than those found in pfkelch13 may be involved in conferring artemisinin resistance in P. falciparum. Piperaquine resistance was also detected among the same Cambodian samples, consistent with reports of emerging piperaquine resistance in the field. These culture-adapted parasites permit further investigation of mechanisms of both artemisinin and piperaquine resistance and development of strategies to prevent or overcome anti-malarial resistance.
青蒿素耐药性与体内疟原虫清除半衰期延长相关，且与体外双氢青蒿素作用下环状体期存活相关。这两种表型均与PF3D7_1343700 pfkelch13基因突变有关。近期东南亚青蒿素耐药性的传播以及新出现的哌喹耐药性表明，双氢青蒿素-哌喹等青蒿素联合疗法正在丧失临床疗效，这促使人们对耐药机制进行研究，并制定克服新出现的抗疟耐药性的策略。
从柬埔寨的两个青蒿素耐药性监测合作研究地点获得了68株有体内清除数据的疟原虫分离株，对其进行适应性培养，并对pfkelch13和其他突变（包括pfmdr1拷贝数）进行基因分型；对其中36株分离株测定了体外环状体期存活率和对抗疟药物的反应。
在这36株疟原虫中，有1株因PfKelch13突变（D584V，环状体期存活率=8%）而表现出环状体期存活增加，该突变先前与清除缓慢有关，但尚未进行体外测试。有几株疟原虫表现出环状体期存活增加，但缺乏pfkelch13突变，还有1株分离株显示出哌喹耐药的证据。
这项对来自柬埔寨的68株适应性培养的恶性疟原虫临床分离株（已知清除值）的研究，将D584V PfKelch13突变与环状体期存活增加联系起来，并鉴定出缺乏pfkelch13突变但环状体期存活增加的疟原虫。这些数据表明，除pfkelch13中发现的突变外，其他突变可能也参与了恶性疟原虫青蒿素耐药性的产生。在同一批柬埔寨样本中还检测到了哌喹耐药性，这与该领域新出现的哌喹耐药性报告一致。这些适应性培养的疟原虫有助于进一步研究青蒿素和哌喹耐药机制，并制定预防或克服抗疟耐药性的策略。
