Institut de Recherche pour le Développement (IRD), Mère et enfant face aux infections tropicales (UMR216), Paris Cedex, France.
Malar J. 2011 Jul 19;10:196. doi: 10.1186/1475-2875-10-196.
The prevention of malaria faces with the repeated emergence of Plasmodium falciparum resistance to drugs, often involving point mutations of the target gene. In the pregnant woman, currently the WHO recommendation is the administration of an intermittent preventive treatment (IPTp) with sulphadoxine-pyrimethamine. Sulphadoxine-pyrimethamine (SP) resistance has increased for several years in Africa, stressing the need for alternative molecules. In this context, the first randomized clinical trial comparing the efficacy of SP and mefloquine for IPTp has been conducted recently in Benin. Using samples from this trial, the current study evaluated and quantified the prevalence of mutations on the pfdhfr and pfdhps genes as well as the copy number of the pfmdr1 gene in parasites from P. falciparum-infected pregnant women before first and second IPTp administration, and at delivery.
PCR-restriction fragment length polymorphism of polymorphic codons of the pfdhfr gene (51, 59, 108, and 164) was performed. The identification of mutations in three codons of the pfdhps gene (436, 437 and 540) was achieved by PCR and sequencing. Copy number quantification for pfmdr1 gene was performed using real-time PCR.
Results show a high prevalence rate of mutant parasites in women taking IPTp with sulphadoxine-pyrimethamine or mefloquine. The prevalence of triple and quadruple mutants was high before first drug regimen administration (79/93, 85%), and remained similar until delivery. Infection with mutant parasites was not correlated with low birth weight nor placental infection. In all samples, the copy number of pfmdr1 gene was equal to one.
The clinical trial comparing SP and mefloquine efficacy during IPTp showed SP remained efficacious in preventing low birth weight. The present study shows a high prevalence of triple and quadruple mutations implicated in SP resistance. Although the pfdhfr/pfdhps triple and quadruple mutations were frequent, there was no evidence of correlation between these genotypes and the lack of efficacy of SP in the context of IPTp. Nevertheless, it is now obvious that SP will soon be compromised in whole Africa. Molecular markers have been recommended to monitor SP efficacy for IPTp, but given the current prevalence of mutant parasites their usefulness is questionable.
疟疾的防治面临着恶性疟原虫对药物的反复耐药，这种耐药通常涉及靶基因的点突变。在孕妇中，目前世界卫生组织的建议是采用磺胺多辛-乙胺嘧啶间歇性预防治疗（IPTp）。磺胺多辛-乙胺嘧啶（SP）耐药性在非洲已经多年来不断增加，这凸显了需要替代分子的必要性。在此背景下，最近在贝宁进行了一项比较 SP 和甲氟喹用于 IPTp 的疗效的随机临床试验。利用该试验的样本，本研究评估并量化了寄生虫中 pfdhfr 和 pfdhps 基因的突变以及 pfmdr1 基因的拷贝数在首次和第二次 IPTp 给药前和分娩时感染恶性疟原虫的孕妇中的流行率。
对 pfdhfr 基因（51、59、108 和 164）的多态性密码子进行 PCR-限制性片段长度多态性分析。通过 PCR 和测序鉴定 pfdhps 基因三个密码子（436、437 和 540）的突变。使用实时 PCR 进行 pfmdr1 基因拷贝数定量。
结果表明，接受磺胺多辛-乙胺嘧啶或甲氟喹 IPTp 的女性中，突变寄生虫的流行率很高。三重和四重突变体在首次药物治疗前的流行率很高（79/93，85%），直到分娩时仍保持相似。感染突变寄生虫与低出生体重或胎盘感染无关。在所有样本中，pfmdr1 基因的拷贝数均为 1。
比较 SP 和甲氟喹在 IPTp 期间疗效的临床试验表明，SP 仍然有效预防低出生体重。本研究表明，SP 耐药相关的三重和四重突变体的流行率很高。尽管 pfdhfr/pfdhps 三重和四重突变很常见，但没有证据表明这些基因型与 SP 在 IPTp 中的疗效丧失有关。然而，现在很明显，SP 将很快在整个非洲受到影响。已经推荐分子标记来监测 SP 用于 IPTp 的疗效，但鉴于目前突变寄生虫的流行率，其有用性值得怀疑。
