Ex vivo susceptibilities of Plasmodium vivax isolates from the China-Myanmar border to antimalarial drugs and association with polymorphisms in Pvmdr1 and Pvcrt-o genes.

Jiangyan Li,Cuiying Li,Jie Zhang,Jichen Qiao,Xi He,Jun Miao,Yonghua Ruan,Yue Hu,Weilin Zeng,Qiang Fang,Zhiyong Tao,Luyi Zhao,Zhaoqing Yang,Faiza A Siddiqui,Hui Xia,Liwang Cui,Lingwen Meng,Qian Li,Kamala Thriemer

doi:10.1371/journal.pntd.0008255

Abstract

BackgroundVivax malaria is an important public health problem in the Greater Mekong Subregion (GMS), including the China-Myanmar border. Previous studies have found that Plasmodium vivax has decreased sensitivity to antimalarial drugs in some areas of the GMS, but the sensitivity of P. vivax to antimalarial drugs is unclear in the China-Myanmar border. Here, we investigate the drug sensitivity profile and genetic variations for two drug resistance related genes in P. vivax isolates to provide baseline information for future drug studies in the China-Myanmar border.Methodology/Principal findingsA total of 64 P. vivax clinical isolates collected from the China-Myanmar border area were assessed for ex vivo susceptibility to eight antimalarial drugs by the schizont maturation assay. The medians of IC50 (half-maximum inhibitory concentrations) for chloroquine, mefloquine, pyronaridine, piperaquine, quinine, artesunate, artemether, dihydroartemisinin were 84.2 nM, 34.9 nM, 4.0 nM, 22.3 nM, 41.4 nM, 2.8 nM, 2.1 nM and 2.0 nM, respectively. Twelve P. vivax clinical isolates were found over the cut-off IC50 value (220 nM) for chloroquine resistance. In addition, sequence polymorphisms in pvmdr1 (P. vivax multidrug resistance-1), pvcrt-o (P. vivax chloroquine resistance transporter-o), and difference in pvmdr1 copy number were studied. Sequencing of the pvmdr1 gene in 52 samples identified 12 amino acid substitutions, among which two (G698S and T958M) were fixed, M908L were present in 98.1% of the isolates, while Y976F and F1076L were present in 3.8% and 78.8% of the isolates, respectively. Amplification of the pvmdr1 gene was only detected in 4.8% of the samples. Sequencing of the pvcrt-o in 59 parasite isolates identified a single lysine insertion at position 10 in 32.2% of the isolates. The pvmdr1 M908L substitutions in pvmdr1 in our samples was associated with reduced sensitivity to chloroquine, mefloquine, pyronaridine, piperaquine, quinine, artesunate and dihydroartemisinin.ConclusionsOur findings depict a drug sensitivity profile and genetic variations of the P. vivax isolates from the China-Myanmar border area, and suggest possible emergence of chloroquine resistant P. vivax isolates in the region, which demands further efforts for resistance monitoring and mechanism studies.

Highlights

With extensive control efforts over the last decade, the global malaria burden has been greatly reduced, which has motivated many countries to reset their goals for malaria elimination [1]
Our findings depict a drug sensitivity profile and genetic variations of the P. vivax isolates from the China-Myanmar border area, and suggest possible emergence of chloroquine resistant P. vivax isolates in the region, which demands further efforts for resistance monitoring and mechanism studies
In view of the important role of antimalarial drugs in malaria elimination strategies, we investigate the drug sensitivity profile and genetic variations of the P. vivax isolates from the China-Myanmar border

Summary

Introduction

With extensive control efforts over the last decade, the global malaria burden has been greatly reduced, which has motivated many countries to reset their goals for malaria elimination [1]. The Greater Mekong Subregion (GMS), which comprises six countries (Cambodia, China, Laos, Myanmar, Thailand, and Vietnam), is aiming to achieve the goal of regional malaria elimination by 2030 [2, 3]. This plan is being challenged by the increased prevalence of Plasmodium vivax (P. vivax) [4], a parasite capable of surviving as a dormant form and causing relapses [5, 6]. Previous studies have found that Plasmodium vivax has decreased sensitivity to antimalarial drugs in some areas of the GMS, but the sensitivity of P. vivax to antimalarial drugs is unclear in the China-Myanmar border. We investigate the drug sensitivity profile and genetic variations for two drug resistance related genes in P. vivax isolates to provide baseline information for future drug studies in the China-Myanmar border

Methods

Results

Conclusion