Polymorphisms of Molecular Markers of Antimalarial Drug Resistance and Relationship with Artesunate-Mefloquine Combination Therapy in Patients with Uncomplicated Plasmodium falciparum Malaria in Thailand

Abstract

Abstract. The aim of this study was to investigate the association between genetic polymorphisms of Plasmodium falciparum chloroquine resistance transporter ( pfcrt ), P. falciparum multidrug resistance 1 ( pfmdr1 ), and P. falciparum ATPase ( pfatp6 ) and clinical outcome after a three-day mefloquine-artesunate combination therapy in 134 patients with uncomplicated Plasmodium falciparum malaria in an area with multidrug resistance along the Thailand-Myanmar border. Analysis of gene mutation and amplification were performed by nested real-time polymerase chain reaction and SYBR Green I real-time polymerase chain reaction, respectively. The mutation for pfcrt (codons 76, 220, 271, 326, 356, and 371) was found in all isolates (100%), whereas no mutation of pfmdr1 (codon 86) and pfatp6 (codons 37, 693, 769, 898) was found. The Pfmdr1 copy number was significantly higher in isolates with recrudescence (median number = 2.44) compared with a sensitive response (median number = 1.44). The gene copy number was also found to be significantly higher in paired isolates collected before treatment and at the time of recrudescence. All isolates carried one pfatp6 gene copy.

Molecular surveillance for drug-resistant Plasmodium falciparum in clinical and subclinical populations from three border regions of Burma/Myanmar: cross-sectional data and a systematic review of resistance studies

“…The prevalence of pfmdr1 amplification was relatively low (12-19%) across the three border regions included in the current study; and only a single isolate had a CN of three or more. Results from Karen State contrast with recent studies documenting elevated CN in at least 40% of isolates [9] with a mean CN of 2.9 (SE 1.4) [39] among refugee, migrant and cross-border populations in Thailand (Figure 1). Findings from Kachin State contrast with a recent study in Laiza that found no pfmdr1 amplification in 171 P. falciparum isolates [40,41], but is consistent with a study conducted in 2004 in nearby counties of Yunnan province [42].…”

“… Systematic review of in vivo , in vitro , and molecular resistance studies in Myanmar and neighbouring countries, 1996–2009 [ [1,7,9,10,13,39,40,60-82] ]. …”

“…Tracking Plasmodium falciparum multidrug resistance protein ( pfmdr1 ) gene copy number (CN) has become an important surveillance tool, particularly in populations receiving artesunate-mefloquine. Pfmdr1 CN is associated with delayed response to ACT, including artesunate-mefloquine [9] and artemether–lumefantrine [10,11], as well as resistance to multiple monotherapy including mefloquine [12-15]. …”

Polymorphic patterns of pfcrt and pfmdr1 in Plasmodium falciparum isolates along the Thai-Myanmar border

“…With regards to pfmdr1 copy number, the increase of copy number found in some P. falciparum isolates in this study correlates well with the observation of decline in sensitivity of P. falciparum to artesunate and mefloquine and therefore, the chance of recrudescence/treatment failure following treatment with this artemisinin-based combination therapy regimen [25,26] . Application of the median copy number and prevalence of isolates carrying more than one gene copies can sort out the provinces with relatively high possibility of treatment failure and require close monitoring for drug resistance as Kanchanaburi, followed by Mae Hongson, Tak and Ranong, respectively.…”

Temporal trends in prevalence of Plasmodium falciparum molecular markers selected for by artemether–lumefantrine treatment in pre-ACT and post-ACT parasites in western Kenya

“…Although polymorphisms at the pfmdr1 codons 86, 184, 1034, 1042, 1246 are associated with altered sensitivity to artemisinins and mefloquine in SEA, the key determinant has been shown to be the copy number variation ( Cowman et al., 1994; Price et al., 1999; Duraisingh et al., 2000; Price et al., 2004; Sidhu et al., 2005; Picot et al., 2009; Muhamad et al., 2011 ). Further, the discovery of mutations in K13-propeller in SEA but not in African parasites shows the multigenetic nature of artemisinin resistance in different parts of the world.…”