1984 年至 1998 年间非洲地区耐乙胺嘧啶和氯喹恶性疟原虫的鉴定：存档血样的基因分型。

Identification of pyrimethamine- and chloroquine-resistant Plasmodium falciparum in Africa between 1984 and 1998: genotyping of archive blood samples.

机构信息

Department of Parasitology, National Institute of Infectious Diseases, Shinjuku-ku, Tokyo, Japan.

出版信息

Malar J. 2011 Dec 31;10:388. doi: 10.1186/1475-2875-10-388.

DOI:10.1186/1475-2875-10-388

PMID:22208458

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC3309963/

Abstract

BACKGROUND

Understanding the geographical distribution of drug resistance of Plasmodium falciparum is important for the effective treatment of malaria. Drug resistance has previously been inferred mainly from records of clinical resistance. However, clinical resistance is not always consistent with the parasite's genetic resistance. Thus, molecular identification of the parasite's drug resistance is required. In Africa, clinical resistance to pyrimethamine (Pyr) and chloroquine (CQ) was evident before 1980 but few studies investigating the genetic resistance to these drugs were conducted before the late 1990s. In this study, genotyping of genes involved in resistance to Pyr and CQ was performed using archive blood samples from Africa between 1984 and 1998.

METHODS

Parasite DNA was extracted from P. falciparum-infected blood smears collected from travellers returning to Japan from Africa between 1984 and 1998. Genotypes of the dihydrofolate reductase gene (dhfr) and CQ-resistance transporter gene (pfcrt) were determined by polymerase chain reaction amplification and sequencing.

RESULTS

Genotyping of dhfr and pfcrt was successful in 59 and 80 samples, respectively. One wild-type and seven mutant dhfr genotypes were identified. Three dhfr genotypes lacking the S108N mutation (NRSI, ICSI, IRSI; amino acids at positions 51, 59, 108, and 164 with mutations underlined) were highly prevalent before 1994 but reduced after 1995, accompanied by an increase in genotypes with the S108N mutation. The dhfr IRNI genotype was first identified in Nigeria in 1991 in the present samples, and its frequency gradually increased. However, two double mutants (ICNI and NRNI), the latter of which was exclusively found in West Africa, were more frequent than the IRNI genotype. Only two pfcrt genotypes were found, the wild-type and a Southeast Asian type (CVIET; amino acids at positions 72-76 with mutations underlined). The CVIET genotype was already present as early as 1984 in Tanzania and Nigeria, and appeared throughout Africa between 1984 and 1998.

CONCLUSIONS

This study is the first to report the molecular identification of Pyr- and CQ-resistant genotypes of P. falciparum in Africa before 1990. Genotyping of dhfr and pfcrt using archive samples has revealed new aspects of the evolutionary history of Pyr- and CQ-resistant parasites in Africa.

摘要

背景

了解恶性疟原虫的耐药性的地理分布对于疟疾的有效治疗很重要。耐药性以前主要是根据临床耐药记录推断的。然而，临床耐药性并不总是与寄生虫的遗传耐药性一致。因此，需要对寄生虫的耐药性进行分子鉴定。在非洲，1980 年以前已经明显存在对氨苯砜（Pyr）和氯喹（CQ）的临床耐药性，但在 20 世纪 90 年代末之前，很少有研究调查这些药物的遗传耐药性。在这项研究中，使用 1984 年至 1998 年间从非洲返回日本的旅行者的血液样本进行了与 Pyr 和 CQ 耐药性相关的基因的基因分型。

方法

从 1984 年至 1998 年间从感染疟原虫的旅行者的血涂片提取寄生虫 DNA。通过聚合酶链反应扩增和测序确定二氢叶酸还原酶基因（dhfr）和 CQ 耐药转运蛋白基因（pfcrt）的基因型。

结果

成功对 59 个和 80 个样本进行了 dhfr 和 pfcrt 基因分型。鉴定了一个野生型和七个突变 dhfr 基因型。在 1994 年之前，高度流行缺乏 S108N 突变的三种 dhfr 基因型（NRSI、ICSI、IRSI；位置 51、59、108 和 164 的氨基酸用下划线表示突变），但在 1995 年后减少，同时伴有 S108N 突变的基因型增加。dhfrIRNI 基因型于 1991 年在尼日利亚首次在本样本中发现，其频率逐渐增加。然而，两种双突变体（ICNI 和 NRNI），后者仅在西非发现，比 IRNI 基因型更为常见。仅发现两种 pfcrt 基因型，野生型和东南亚型（CVIET；位置 72-76 的氨基酸用下划线表示突变）。CVIET 基因型早在 1984 年就在坦桑尼亚和尼日利亚出现，并于 1984 年至 1998 年间在整个非洲出现。