Plasmodium vivax mdr1 genotypes in isolates from successfully cured patients living in endemic and non-endemic Brazilian areas

Abstract

BackgroundPlasmodium vivax is the most widely distributed species causing the highest number of malaria cases in the world. In Brazil, P. vivax is responsible for approximately 84 % of reported cases. In the absence of a vaccine, control strategies are based on the management of cases through rapid diagnosis and adequate treatment, in addition to vector control measures. The approaches used to investigate P. vivax resistance to chloroquine (CQ) were exclusively in vivo studies because of the difficulty in keeping parasites in continuous in vitro culture. In view of the limitations related to follow-up of patients and to assessing the plasma dosage of CQ and its metabolites, an alternative approach to monitor chemo-resistance (QR) is to use molecular markers. Single nucleotide polymorphisms (SNPs) in the multidrug resistance gene pvmdr1 are putative determinants of CQ resistance (CQR), but such SNPs in P. vivax isolates from patients with good response to treatment should be further explored. The aim of this study is to investigate the mutations in the gene, supposedly associated to QR, in P. vivax isolates from successfully cured patients, living in Brazilian endemic and non-endemic areas.MethodsBlood samples were collected from 49 vivax malaria patients from endemic (Amazon Basin: 45) and non-endemic (Atlantic Forest: four) Brazilian regions and analysed for SNPs in the CQR-related P. vivax gene (pvmdr1), using PCR-based methods.ResultsAmong the 49 isolates genetically characterized for the gene pvmdr1, 34 (70 %) presented at least one mutation. T958M mutant alleles were the most frequent (73 %) followed Y976F (15 %) and F1076L (12 %). Single mutation was detected in 24 (70.5 %) isolates and double mutations in ten (29.5 %). The most common single mutant genotype was the 958M/Y976/F1076 (79 %), followed by 976F/F1076 (21 %) whereas 958M/Y976/1076L (60 %) and 976F/1076L (40 %) double mutant genotypes were detected. Single mutant profile was observed only in isolates from Amazon Basin, although double mutants were found both in the Amazon and Atlantic Forest regions. Interestingly, the genotype 958M/Y976/1076L was present in all isolates from the Atlantic Forest in the Rio de Janeiro State.ConclusionsConsidering that primaquine (PQ) efficacy is highly dependent on concurrent administration of a blood schizontocidal agent and that PQ could not circumvent CQR, together with the fact that no pvmdr1 mutation should be expected in successfully cured patients, these findings seem to indicate that the pvmdr1 gene is not a reliable marker of CQR. Further investigations are needed to define a reliable molecular marker for monitoring P. vivax CQR in P. vivax populations.

Characterization of P. vivax blood stage transcriptomes from field isolates reveals similarities among infections and complex gene isoforms

“…Our study, by thoroughly characterizing these regions (that were very incompletely annotated previously), also provides an important resource to better investigate the role of these regions and their variability. One gene that would be interesting to further study based on our findings is PvMDR1, which is commonly duplicated in some endemic regions 34 and has been implicated in chloroquine or mefloquine resistance 35 , 36 . Our data clearly indicated the presence of alternatively spliced 3′-UTR introns in some transcripts, and it would be interesting to test whether these isoforms affect PvMDR1 translation or are associated with antimalarial drug resistance.…”

Plasmodium vivax multidrug resistance-1 gene polymorphism in French Guiana

“…These temporal variations of allele frequencies could be explained by different factors, such as the increased circulation of isolates between French Guiana and Brazil or changes in drug policy for the treatment of P. falciparum . This is supported by a recent study showing that the T958M mutation allele is the majority among Brazilian isolates collected between 2010 and 2014 [42]. Many studies in Southeast Asia have shown that isolates with pvmdr1 gene amplification were characterized by increased susceptibility to chloroquine but decreased susceptibility to mefloquine [13, 31].…”

Genetic diversity of Plasmodium vivax metacaspase 1 and Plasmodium vivax multi-drug resistance 1 genes of field isolates from Mauritania, Sudan and Oman

“…Analysis of pvmdr1 sequences has shown SNPs at three codons 958, 976 and 1076 as previously described [ 6 , 12 , 15 , 17 , 19 ]. The substitution in the codon T958 M is known as an allelic variant, of which T958 wild-type was identified in Ecuador and 958M is thought being characteristic of Asia and Africa [ 12 ], while it has also been found in samples from Brazil [ 19 ]., The allelic form 958M was identified in samples from Africa and south western Asia tested here. Few isolates showed the single mutation Y976 F (4/30), in agreement with the fact that the single 976 F mutant is not very common worldwide [ 17 , 19 ].…”

“…The substitution in the codon T958 M is known as an allelic variant, of which T958 wild-type was identified in Ecuador and 958M is thought being characteristic of Asia and Africa [ 12 ], while it has also been found in samples from Brazil [ 19 ]., The allelic form 958M was identified in samples from Africa and south western Asia tested here. Few isolates showed the single mutation Y976 F (4/30), in agreement with the fact that the single 976 F mutant is not very common worldwide [ 17 , 19 ]. In contrast, many studies have reported a high prevalence of the Y976 L and/or F1076 L mutants associated with treatment failure [ 15 , 18 ].…”

“…Pvmdr1 mutated codon 976F was linked to treatment failure in studies conducted in Southeast Asia and Ethiopia [ 17 , 18 ]. However, still no consensus exists regarding the relationship between polymorphism at codons 976 and 1076 in the pvmdr1 gene and drug resistance or clinical failures [ 19 , 20 ].…”