Pfatp6 Polymorphisms of Plasmodium falciparum Isolates in Thailand and Association with in Vitro Sensitivity to Artesunate and Mefloquine

Abstract

The sarco/endoplasmic reticulum Ca2+- ATPase of Plasmodium falciparum or pfatp6
has been proposed to be a target for artemisinin and derivatives which are currently used
worldwide to combat the emergence of multi-drug resistance P. falciparum. Nevertheless,
reports of clinical treatment failure with supplemented data on single-nucleotide
polymorphisms (SNPs) of P.falciparum genes associated with resistance have been
increasing in malaria endemic areas including Thailand. In this study, we investigated the
association between Pfatp6 polymorphisms, and in vitro sensitivity in a total of 63 P.
falciparum isolates collected from the Thai-Myanmar border, to artesunate and mefloquine.
All isolates were adapted to continuous culture in vitro and assessed for their susceptibility to
artesunate and mefloquine. Malarial parasite DNA was extracted from blood samples using
Chelex-100 assay. Polymorphism of pfatp6 at codons R37K, G639D, S769N and I898I were
analyzed based on polymerase chain reaction-restriction fragment length polymorphism
(PCR-RFLP). Gene copy number of all isolates was analyzed by quantitative real timepolymerase
chain reaction (qRT-PCR). Results showed no mutation of pfATP6 gene at any
codon investigated. In this limited number of isolates under investigation, no association
between SNP and amplification of pfatp6 gene and in vitro sensitivity of P.falciparum
isolates to artesunate and mefloquine.