Nuralitha Suci, Siregar Josephine E, Syafruddin Din, Hoepelman Andy I M, Marzuki Sangkot
Eijkman Institute for Molecular Biology, Jakarta, Indonesia.
Internal Medicine and Infectious Diseases, University Medical Centre, Utrecht, Netherlands.
Malar J. 2017 May 23;16(1):216. doi: 10.1186/s12936-017-1860-6.
To study within-host selection of resistant parasites, an important factor in the development of resistance to anti-malarial drugs, a mouse model of repeated interrupted malaria treatment (RIT) has been developed. The characteristics of within host selection of resistance to atovaquone and pyrimethamine in Plasmodium yoelii was examined in such a model.
Treatment of P. yoelii infected mice, with atovaquone or pyrimethamine, was started at parasitaemia level of 3-5%, interrupted when reduced to less than 0.4%, and restarted following parasitaemia recovery to the initial level. Treatment cycles were repeated until stable phenotype resistance was observed.
Plasmodium yoelii rapidly developed resistance to atovaquone (2.75 ± 1.06 cycles) and to pyrimethamine (5.4 ± 0.89 cycles) under RIT. A dose dependent phenomenon in the selection of atovaquone resistance mutations was observed. All mutations that underlie resistance to therapeutic doses of 0.3-1.44 mg kg BW were found to be in the Qo2 domain of the cytochrome b gene (I258M, F267I/L/S, L271V, K272R, L271V and K272R). Those associated with lower doses of 0.01-0.03 mg kg BW were in the Qo1 domain (M133I and T139S). The resistance mutations occurred at four of the 16 atovaquone putative drug binding sites suggested in P. falciparum.
RIT of P. yoelii infected mice led to rapid development of resistance to atovaquone and pyrimethamine. The dose dependent selection of resistance mutants to atovaquone observed during RIT might reflect the outcome of two different causes of malaria treatment failure in human, repeated incomplete treatment with therapeutic dose and repeated inadequate treatment associated with sub-therapeutic dose, and need to be systematically investigated.
为了研究宿主体内抗药寄生虫的选择，这是抗疟药物耐药性发展的一个重要因素，已经建立了一种重复间断疟疾治疗（RIT）的小鼠模型。在此模型中研究了约氏疟原虫对阿托伐醌和乙胺嘧啶耐药性的宿主体内选择特征。
对感染约氏疟原虫的小鼠，当疟原虫血症水平达到3%-5%时开始用阿托伐醌或乙胺嘧啶治疗，当疟原虫血症水平降至低于0.4%时中断治疗，当疟原虫血症恢复到初始水平时重新开始治疗。重复治疗周期，直到观察到稳定的表型耐药性。
在RIT条件下，约氏疟原虫对阿托伐醌（2.75±1.06个周期）和乙胺嘧啶（5.4±0.89个周期）迅速产生耐药性。观察到阿托伐醌耐药突变选择中的剂量依赖性现象。所有导致对0.3-1.44mg/kg体重治疗剂量耐药的突变都位于细胞色素b基因的Qo2结构域（I258M、F267I/L/S、L271V、K272R、L271V和K272R）。那些与0.01-0.03mg/kg体重较低剂量相关的突变位于Qo1结构域（M133I和T139S）。耐药突变发生在恶性疟原虫中16个推测的阿托伐醌药物结合位点中的4个。
感染约氏疟原虫小鼠的RIT导致对阿托伐醌和乙胺嘧啶迅速产生耐药性。在RIT期间观察到的阿托伐醌耐药突变体的剂量依赖性选择可能反映了人类疟疾治疗失败的两种不同原因的结果，即治疗剂量的重复不完全治疗和与亚治疗剂量相关的重复不足治疗，需要进行系统研究。
