Optimizing the HRP-2 in vitro malaria drug susceptibility assay using a reference clone to improve comparisons of Plasmodium falciparum field isolates.
Malar J
; 11: 325, 2012 Sep 13.
Article
in En
| MEDLINE
| ID: mdl-22974086
ABSTRACT
BACKGROUND:
Apparent emerging artemisinin-resistant Plasmodium falciparum malaria in Southeast Asia requires development of practical tools to monitor for resistant parasites. Although in vitro anti-malarial susceptibility tests are widely used, uncertainties remain regarding interpretation of P. falciparum field isolate values.METHODS:
Performance parameters of the W2 P. falciparum clone (considered artemisinin "sensitive") were evaluated as a reference for the HRP-2 immediate ex vivo assay. Variability in W2 IC50s was assessed, including intra- and inter-assay variability among and between technicians in multiple experiments, over five freeze-thaw cycles, over five months of continuous culture, and before and after transport of drug-coated plates to remote field sites. Nominal drug plate concentrations of artesunate (AS) and dihydroartemisinin (DHA) were verified by LC-MS analysis. Plasmodium falciparum field isolate IC50s for DHA from subjects in an artemisinin-resistant area in Cambodia were compared with W2 susceptibility.RESULTS:
Plate drug concentrations and day-to-day technical assay performance among technicians were important sources of variability for W2 IC50s within and between assays. Freeze-thaw cycles, long-term continuous culture, and transport to and from remote sites had less influence. Despite variability in W2 susceptibility, the median IC50s for DHA for Cambodian field isolates were higher (p <0.0001) than the W2 clone (3.9 nM), both for subjects with expected (less than 72 hours; 6.3 nM) and prolonged (greater or equal to 72 hours; 9.6 nM) parasite clearance times during treatment with artesunate monotherapy.CONCLUSION:
The W2 reference clone improved the interpretability of field isolate susceptibility from the immediate ex vivo HRP-2 assay from areas of artemisinin resistance. Methods to increase the reproducibility of plate coating may improve overall assay interpretability and utility.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Plasmodium falciparum
/
Protozoan Proteins
/
Malaria, Falciparum
/
Parasitic Sensitivity Tests
/
Antigens, Protozoan
/
Antimalarials
Limits:
Humans
Language:
En
Journal:
Malar J
Journal subject:
MEDICINA TROPICAL
Year:
2012
Type:
Article
Affiliation country:
Thailand