Characterization of Treatment Failure in Efficacy Trials of Drugs against Plasmodium vivax by Genotyping Neutral and Drug Resistance-Associated Markers

Abstract

Plasmodium vivax intervention trials customarily report uncorrected treatment failure rates. Application of recrudescence-reinfection genotyping and drug resistance single-nucleotide polymorphism typing to a 4-arm comparative efficacy trial illustrated that molecular approaches can assist in understanding the relative contributions of true drug resistance (recurrent with same genotype) and new infections to treatment failure. The PCR-corrected adequate clinical and parasitologic response may constitute an informative secondary endpoint in future P. vivax drug trials.

Fixed-Dose Artesunate–Amodiaquine Combination vs Chloroquine for Treatment of Uncomplicated Blood Stage P. vivax Infection in the Brazilian Amazon: An Open-Label Randomized, Controlled Trial

“…Genotyping has been applied in P. vivax efficacy studies with interesting results [35, 36]. However, unlike in P. falciparum , there are no well-defined criteria to differentiate recrudescence from reinfection and relapse [25].…”

“…For the genotyping procedures for comparing day 0 and recurrence samples, 3 highly polymorphic gene regions were chosen according to diversity and discriminatory potential in the region, namely, msp1F3, MS2, and MS8 [31–34]. As there is no standard recommendation for classifying P. vivax recurrences due to difficulties distinguishing reinfection, recrudescence, and relapse [35, 36], we adapted the classification method recommended by WHO for P. falciparum [25]. For each recurrence, samples were classified as homologous if at least 1 allele for each loci investigated was detected in both paired samples and as heterologous if all alleles for a given marker were different.…”

A new high-throughput method for simultaneous detection of drug resistance associated mutations in Plasmodium vivax dhfr, dhps and mdr1 genes

“…Data from PNG isolates on pvdhps have not been generated; only one isolate from PNG was previously sequenced, showing a mutation at codon 647 (647 P ) [40]. As for pvmdr1 , the 976F mutation was found at a prevalence of 39.4% [24] and remains at the same level here (35.1%) despite known high level of CQ-SP drug resistance in PNG (51.4% after PCR correction [41]). It has already been discussed that 4-aminoquinoline resistance may result from a multigenic process involving different SNPs and/or gene amplification, variation in the level of expression [24,25]; it is therefore harder to correlate the 976F mutation frequency with an increase of the in vivo level of drug resistance.…”

Diagnosis and Treatment of Plasmodium vivax Malaria

“…A variety of methodologies have been developed for P. vivax with as few as three polymorphic markers proving to be sufficient to discriminate homologous from heterologous infections. [73][74][75][76] However, recurrence of P. vivax genetically identical to the pretreatment isolate can occur from either a true recrudescence of the initial infection or a relapse from hypnozoites generated from the prior blood-stage infection 74,77 ; unsurprisingly molecular methods are unable to distinguish between these alternatives. Relapses are also commonly genetically heterologous.…”