Abstract
Increasing reports of resistance to a frontline malaria blood-stage treatment, chloroquine (CQ), raises concerns for the elimination of Plasmodium vivax. The absence of an effective molecular marker of CQ resistance in P. vivax greatly constrains surveillance of this emerging threat. A recent genetic cross between CQ sensitive (CQS) and CQ resistant (CQR) NIH-1993 strains of P. vivax linked a moderate CQR phenotype with two candidate markers in P. vivax CQ resistance transporter gene (pvcrt-o): MS334 and In9pvcrt. Longer TGAAGH motif lengths at MS334 were associated with CQ resistance, as were shorter motifs at the In9pvcrt locus. In this study, high-grade CQR clinical isolates of P. vivax from a low endemic setting in Malaysia were used to investigate the association between the MS334 and In9pvcrt variants and treatment efficacy. Among a total of 49 independent monoclonal P. vivax isolates assessed, high-quality MS334 and In9pvcrt sequences could be derived from 30 (61%) and 23 (47%), respectively. Five MS334 and six In9pvcrt alleles were observed, with allele frequencies ranging from 2 to 76% and 3 to 71%, respectively. None of the clinical isolates had the same variant as the NIH-1993 CQR strain, and none of the variants were associated with CQ treatment failure (all P > 0.05). Multi-locus genotypes (MLGs) at 9 neutral microsatellites revealed a predominant P. vivax strain (MLG6) accounting for 52% of Day 0 infections. The MLG6 strain comprised equal proportions of CQS and CQR infections. Our study reveals complexity in the genetic basis of CQ resistance in the Malaysian P. vivax pre-elimination setting and suggests that the proposed pvcrt-o MS334 and In9pvcrt markers are not reliable markers of CQ treatment efficacy in this setting. Further studies are needed in other endemic settings, applying hypothesis-free genome-wide approaches, and functional approaches to understand the biological impact of the TGAAGH repeats linked to CQ response in a cross are warranted to comprehend and track CQR P. vivax.
| Original language | English |
|---|---|
| Pages (from-to) | 1-12 |
| Number of pages | 12 |
| Journal | Antimicrobial Agents and Chemotherapy |
| Volume | 67 |
| Issue number | 7 |
| DOIs | |
| Publication status | Published - 18 Jul 2023 |
Bibliographical note
Funding Information:We thank the participants in this study; the Malaysian clinical and laboratory research staff; the Director-General of Health, Malaysia; Kim Piera and Ammar Aziz for conducting the PCR for species diagnosis; and Irene Handayuni for conducting the microsatellite genotyping. [The study was funded by the National Health and Medical Research Council (NHMRC) Australia Ideas Grant (APP2001083) awarded to S.A., program Grant 1037304, project grant 1045156, and a Senior Principal Research Fellowship to NMA (1135820)], Malaysian Ministry of Health (grant BP00500420), and the AusAID Asia-Pacific Malaria Elimination Network (grant 108-07). The work was also supported by the Australian Centre for Research Excellence on Malaria Elimination (ACREME), funded by the National Health and Medical Research Council of Australia (APP1134989). J.M.S. was supported by the Division of Intramural Research from the National Institute of Allergy and Infectious Diseases, National Institutes of Health.
Publisher Copyright:
Copyright © 2023 Rumaseb et al.
