Synergism between Pfcrt and Pfmdr1 genes could account for the slow recovery of chloroquine sensitive Plasmodium falciparum strains in Ghana after chloroquine withdrawal

Abstract

Unlike other countries, the chloroquine resistant marker Pfcrt T76 mutant has remained fairly stable in Ghana several years after official disuse of chloroquine. Certain mutations in Pfmdr1 may potentiate Pfcrt T76, offering a possible explanation for this observation. To understand the phenomenon, the co-existence of mutations in Pfmdr1 with Pfcrt T76 in Ghanaian Plasmodium falciparum isolates was studied. The reported presence of parasites with reduced sensitivity to amodiaquine and quinine in the country was also studied. Blood samples collected from confirmed malaria patients presenting at health facilities in two distinct ecological zones were analyzed. The prevalence of Pfcrt K76T and the five point mutations in Pfmdr1 were determined using nested PCR followed by RFLP analysis. The association between genes was determined by chi square analysis, and synergism between the two genes was ascertained using the Jonckheere-Terptra (J-T) test followed by Monte Carlo simulation (MCS). Nearly fifty-four percent (53.7%) of the P. falciparum isolates examined had the Pfcrt T76 gene, out of which 18.3% had both K76 and T76 alleles. Mutations at codon 86, 184, 1034, 1042 and 1246 of the Pfmdr1 gene were detected in 36.0%, 87.9%, 71.0%, 91.6% and 8.4% of the isolates, respectively. The haplotypes of Pfmdr1 present were NFCDD (43.46%), YFCDD (27.57%), NFSDD (7.48%), NYSNY (5.14%) and YFSDD (4.67%). Pfcrt T76 was significantly associated with a double mutation at codon 86 and 184 of Pfmdr1 (YF; χ=18.045, p=0.006). Associations were observed between Pfcrt K76T and Pfmdr1 triple mutation at codons 86, 184 and 1034 (NFC; χ=13.770, p=0.032 and YFC; χ=16.489, p=0.011). The J-T test showed significant synergism between Pfcrt 76 and Pfmdr1 polymorphisms (p<0.0001), which was confirmed by MCS at 99% CI. Synergism between Pfcrt and Pfmdr1 mutant genes could account for the slow recovery of chloroquine sensitive P. falciparum in Ghana. The same phenomenon could explain resistance to amodiaquine and quinine. The outcomes of this study also indicated a possible emergence of artemether-lumefantrine resistance in Ghana.

Asymptomatic malaria infections and Pfmdr1 mutations in an endemic area of Nigeria

“…Mutations on the Pfmdr1 gene play a pivotal role with variable parasite response to artemisinin, ACT and non-ACT, such as chloroquine, lumefantrine, primaquine, tafenoquine, piperaquine, and mefloquine [31–38], due to conformational changes in the transporter protein causing decrease in intracellular drug accumulation and effect on the malaria parasite.The haplotype N86Y-Y184F-D1246Y of Pfmdr1 was reported to be susceptible to artemisinin-based combination, whereas triple mutations S1034C, N1042D and D1246Y or increased gene copy number are associated with parasite resistance to mefloquine, halofantrine and artemisinin [36]. Although this study did not assess Pfcrt mutation, there is known synergy between mutations on Pfmdr1 and Pfcrt genes [39]. Studies in Nigeria and other areas have reported reduced in vitro and in vivo response in chloroquine-resistant isolates bearing the 76T mutation correlating strongly with Pfmdr1 86Y mutation [12, 14, 16, 21, 22, 38].…”

Age-depended Selection of Chloroquine-sensitive&nbsp;Plasmodium Falciparum&nbsp;in Some part of Central Region of Ghana

“…The study showed that CQ resistance markers have reduced to a significant level compared to the previous report from the region [35]. Although the steady decline for Pfcrt T76 and Pfmdr1 Y86 has been very slow especially at regional capital (Cape Coast) of Central Region of Ghana yet the expansion of the CQ sensitive P. falciparum strains have increased appreciably [12,15,27]. Similar findings on the reappearance of CQ sensitive parasites have been reported in Malawi, Cameroon, Ethiopia, Nigeria, Tanzania and Mozambique [9,10].…”

“…An archived Plasmodium falciparum infected blood blot samples from Cape Coast, Elmina, Twifo Praso and Assin Foso were used from for this study [27]. The air-dried blood spots in zip-locked plastic envelopes containing silica gel stored at -20°C in the Department of Biomedical Sciences, University of Cape Coast were extracted using chelex extraction method.…”

Polymorphism Analysis of pfmdr1 Gene in Plasmodium falciparum Isolates 11 Years Post-adoption of Artemisinin-based Combination Therapy in Saudi Arabia

“…Altogether, about two-thirds (69.2%; 18/26) of the isolates that carried the pfmdr1 86Y mutation were also found to be carrying the pfcrt 76T mutation. The pfmdr1 86Y point mutation is the second most important molecular marker of CQ resistance after pfcrt 76T, and several studies have suggested that there may be a synergistic association between these pfcrt and pfmdr1 point mutations 31,32 . Moreover, a remarkable decline in the prevalence of mutant pfcrt 76T and pfmdr1 86Y alleles has also been observed in low malaria transmission settings where drug pressure is likely to be lower 33 .…”

“…This pattern is different from that reported in 2012, where 66% and 31% of the examined isolates carried the single NFSN and double YFSN haplotypes while only 3% carried the wild NYSN haplotype (codon 1246 was not involved) 26 . Studies from other countries such as Yemen and Ghana have reported up to ve different haplotypes 32,36 .…”