Polymorphisms in Pf mdr1 , Pf crt , and Pf nhe1 Genes Are Associated with Reduced In Vitro Activities of Quinine in Plasmodium falciparum Isolates from Western Kenya

Abstract

bIn combination with antibiotics, quinine is recommended as the second-line treatment for uncomplicated malaria, an alternative first-line treatment for severe malaria, and for treatment of malaria in the first trimester of pregnancy. Quinine has been shown to have frequent clinical failures, and yet the mechanisms of action and resistance have not been fully elucidated. However, resistance is linked to polymorphisms in multiple genes, including multidrug resistance 1 (Pfmdr1), the chloroquine resistance transporter (Pfcrt), and the sodium/hydrogen exchanger gene (Pfnhe1). Here, we investigated the association between in vitro quinine susceptibility and genetic polymorphisms in Pfmdr1codons 86 and 184, Pfcrt codon 76, and Pfnhe1 ms4760 in 88 field isolates from western Kenya. In vitro activity was assessed based on the drug concentration that inhibited 50% of parasite growth (the IC 50 ), and parasite genetic polymorphisms were determined from DNA sequencing. Data revealed there were significant associations between polymorphism in Pfmdr1-86Y, Pfmdr1-184F, or Pfcrt-76T and quinine susceptibility (P < 0.0001 for all three associations). Eighty-two percent of parasites resistant to quinine carried mutant alleles at these codons (Pfmdr1-86Y, Pfmdr1-184F, and Pfcrt-76T), whereas 74% of parasites susceptible to quinine carried the wild-type allele (Pfmdr1-N86, Pfmdr1-Y184, and Pfcrt-K76, respectively). In addition, quinine IC 50 values for parasites with Pfnhe1 ms4760 3 DNNND repeats were significantly higher than for those with 1 or 2 repeats (P ‫؍‬ 0.033 and P ‫؍‬ 0.0043, respectively). Clinical efficacy studies are now required to confirm the validity of these markers and the importance of parasite genetic background.

Temporal and Seasonal Changes of Genetic Polymorphisms Associated with Altered Drug Susceptibility to Chloroquine, Lumefantrine, and Quinine in Guinea-Bissau between 2003 and 2012

“…Furthermore, the preliminary data indicate that treatment with quinine selected for pfcrt 76T among recrudescing P. falciparum. Other studies have indicated that pfcrt is involved in the transport of quinine and that SNPs in pfcrt, including 76T, decrease P. falciparum susceptibility to quinine (22,(33)(34)(35). Thus, it seems highly probable that the increased pfcrt 76T frequency was due to the increased use of quinine.…”

“…The increased TN haplotype might be due to direct selection by quinine. However, decreased quinine susceptibility has more often been linked with the TY haplotype (22,35). The discrepancy may be due to the probable multigenic basis of quinine resistance (22,37).…”

Single nucleotide polymorphisms in Plasmodium falciparum V type H+ pyrophosphatase gene (pfvp2) and their associations with pfcrt and pfmdr1 polymorphisms

“…Between 2010 and 2012 QN was prescribed to 44% of children diagnosed with P. falciparum malaria [236]. Several studies have linked pfcrt 76T to decreased QN susceptibility [168,[262][263][264]. In line with this, the pfcrt 76T frequency was higher amongst recrudescing P. falciparum compared to day 0 after treatment with QN in Guinea-Bissau [236].…”

“…In line with this, the increase of pfcrt 76T + pfmdr1 86N between 2007 and 2012 in Guinea-Bissau could be due to direct selection by QN. However, decreased QN susceptibility has more often been linked with the TY haplotype[168,264]. The discrepancy may be due to the probably multigenic basis of QN resistance[75,168].…”

Analysis of Major Genome Loci Underlying Artemisinin Resistance and pfmdr1 Copy Number in pre- and post-ACTs in Western Kenya

“…Further, we observed significant association of increased pfmdr 1 gene expression with reduced in vitro drug susceptibility to amodiaquine and piperaquine. Based on molecular markers, studies have shown chloroquine resistance remains high in western Kenya 29 30 . Amodiaquine, chloroquine and piperaquine are in the 4-aminoquinoline drug family, which might explain the significant association seen of increased pfmdr 1 gene expression with reduced in vitro susceptibility to amodiaquine and piperaquine.…”