Limited polymorphisms in k13 gene in Plasmodium falciparum isolates from Dakar, Senegal in 2012–2013

Abstract

BackgroundThe emergence of Plasmodium falciparum resistance to artemisinin and its derivatives, manifested as delayed parasite clearance following the treatment, has developed in Southeast Asia. The spread of resistance to artemisinin from Asia to Africa may be catastrophic for malaria control and elimination worldwide. Recently, mutations in the propeller domain of the Kelch 13 (k13) gene (PF3D71343700) were associated with in vitro resistance to artemisinin and with delayed clearance after artemisinin treatment in southern Asia. The aim of the study was to characterize the genetic variability of k13 and to evaluate the molecular resistance to artemisinin for the first time in Senegal.MethodsPlasmodium falciparum isolates were collected from 138 malaria patients in Dakar and its districts during the rainy season of October 2012 to January 2013 at the Hôpital Principal de Dakar. The k13 gene was amplified using nested PCR and sequenced.ResultsA very limited variability within the k13 gene in Senegalese P. falciparum isolates was identified. No polymorphism was detected in the six k13-propeller blades. Only two mutations, T149S (6.3%) and K189T (42.2%), and one (N) or two (NN) asparagine insertion at the codon 142 (4.7 and 6.3%, respectively) were detected in the Plasmodium/Apicomplexa-specific domain. None of the polymorphisms associated with artemisinin resistance in Southeast Asia was detected in the 138 P. falciparum from Dakar.DiscussionThe present data do not suggest widespread artemisinin resistance in Dakar in 2012–2013. Notably, the C580Y, R539T or Y493H substitutions that were associated with in vitro resistance or delayed parasite clearance in Southeast Asia were not observed in Dakar, nor were any of the polymorphisms observed in parasites from Southeast Asia, nor the M476I mutation that was selected in vitro with artemisinin pressure in a African parasite line.

Molecular Epidemiology of Plasmodium falciparum kelch13 Mutations in Senegal Determined by Using Targeted Amplicon Deep Sequencing

“…In contrast, a recent WHO report (27) indicates that 13 polymorphisms inside the propeller domain are either associated and/or confirmed with artemisinin resistance. The predominant polymorphisms previously reported in Senegal are alleles K189T and K189N, outside the propeller domain (25,26), consistent with our own findings (Table S1). The mutant allele A578S, which is not associated with artemisinin resistance, has been reported in multiple regions in Africa (18,19,24,28) (Table S2).…”

“…Monitoring the changes in Pfk13 allele frequencies over time will be critical for guiding both treatment policy and elimination campaigns. To date, only a limited number of Pfk13 polymorphisms have been reported in Senegal (23,25,26), and overall ACT efficacy remains high (21)(22)(23).…”

Lack of Artemisinin Resistance in Plasmodium falciparum in Uganda Based on Parasitological and Molecular Assays

“…Clinical resistance has not been noted in Africa, as rapid parasite clearance has been the rule in many trials, including those in Uganda (7)(8)(9). In recent surveys in Uganda (10) and other locations in Africa (11)(12)(13)(14)(15), K13-propeller gene polymorphisms were identified, but these were not the mutations clearly associated with artemisinin resistance in Asian isolates. Results for a new correlate of artemisinin resistance, the ex vivo ring-stage survival assay (RSA) (3), have not been reported previously for P. falciparum isolates from Africa.…”

K13-Propeller Polymorphisms in Plasmodium falciparum Isolates from Patients in Mayotte in 2013 and 2014

“…K13-propeller gene amplification and sequencing were performed, as previously described (13). The K13 mutations were confirmed three times.…”