Monitoring resistance of Plasmdium vivax: point mutations in dihydrofolate reductase gene in isolates from Central China.

Fang Huang,Hongwei Zhang,Shuisen Zhou,Shaosen Zhang,Weidong Li

doi:10.1186/1756-3305-4-80

Abstract

BackgroundMalaria still represents a significant public health problem in China, and the cases dramatically increased in Central China after 2001. Antifolate resistance in Plasmodium vivax is caused by point mutations in genes encoding dihydrofolate reductase (pvdhfr) and dihydropteroate synthase (pvdhps). In this study, we used direct sequencing to investigate genetic variation in pvdhfr of malaria patients' samples from Central China.ResultsAmong all the samples, 21.4% were wild-type, whereas mutations were detected at three codons (58, 61 and 117) including single mutant (34.6%) and double mutants (43.8%). The most prevalent mutant allele was the one with double mutation at codons 58 and 117 (24.6%). Three types of single mutation (S58R, T61M and S117N) were found in 2.1%, 11.8% and 20.9% of parasite isolates, respectively. The four P. vivax parasite populations in Central China also differed in pvdhfr allele frequencies.ConclusionsThis study suggested that P. vivax in Central China may be relatively susceptible to pyrimethamine. And it also highlights genotyping in the pvdhfr genes remains a useful tool to monitor the emergence and spread of P. vivax pyrimethamine resistance.

Highlights

Malaria still represents a significant public health problem in China, and the cases dramatically increased in Central China after 2001
Zhou [23] found that the spatial distribution between malaria cases and water-body, the changing of meteorological factors, and increasing vectorial capacity and basic reproductive rate of An. sinensis lead to malaria re-emergence in these areas
The four P. vivax parasite populations in Central China differed in pvdhfr allele frequencies (Table 1). 147 of 187 samples yielded identical dhfr sequence which was of mutant type

Summary

Introduction

Malaria still represents a significant public health problem in China, and the cases dramatically increased in Central China after 2001. Antifolate resistance in Plasmodium vivax is caused by point mutations in genes encoding dihydrofolate reductase (pvdhfr) and dihydropteroate synthase (pvdhps). We used direct sequencing to investigate genetic variation in pvdhfr of malaria patients’ samples from Central China. In Central China, the re-emergence of malaria was considerable in provinces along the Huang-Huai River, especially in Anhui and Henan Provinces. The malaria prevalence increased considerably with the highest incidence and over half of the total malaria cases in 2006 in Anhui Province [4]. Antifolate resistance is strongly associated with mutations at specific sites in the gene encoding dhfr in malaria parasites [6]. Dhfr and thymidylate synthases are parts of a bifunctional enzyme encoded by a single gene. Some research showed that by in vitro assays and kinetic studies of recombinant DHFR enzymes there are several codons that may undergo amino acid substitutions [7,8,9]

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Conclusion