Ordered accumulation of mutations conferring resistance to sulfadoxine-pyrimethamine in the Plasmodium falciparum parasite.
BACKGROUND
Monitoring the prevalence of drug resistant Plasmodium falciparum is essential for effective malaria control. Resistance to pyrimethamine and sulfadoxine increases as mutations accumulate in the parasite genes encoding dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps), respectively. Although parasites are exposed to these antifolate drugs simultaneously, it remains virtually unknown whether dhfr and dhps mutations accumulate along interrelated paths.


METHODS
We investigated the order of step-wise accumulation in dhfr and dhps by cumulative analyses using binomial tests in 575 P. falciparum isolates obtained from 7 countries in Asia and Melanesia.


RESULTS
An initial step in the accumulation of mutations preferentially occurred in dhfr (2 mutations), followed by 1 mutation in dhps. In a subsequent step, mutations were estimated separately for 5 dhfr/dhps-resistant lineages identified using 12 microsatellites flanking dhfr and dhps. Among these lineages, we found 3 major mutational paths, each of which follows a unique stepwise trajectory to produce the most highly resistant form with 4 mutations in dhfr and 3 in dhps.


CONCLUSIONS
The ordered accumulation of mutations in dhfr and dhps elucidated here will assist in predicting the status and progression of antifolate resistance in malaria-endemic regions where antifolate drugs are used for intermittent preventive treatment.
Department of Molecular and Cellular Parasitology, Juntendo University School of Medicine, Tokyo, Japan.
Toshihiro
T
Mita
Jun
J
Ohashi
Meera
M
Venkatesan
Aung Swi Prue
AS
Marma
Masatoshi
M
Nakamura
Christopher V
CV
Plowe
Kazuyuki
K
Tanabe
D000595:Amino Acid Sequence; D000962:Antimalarials / Q000494:pharmacology*; D004094:Dihydropteroate Synthase / Q000737:chemistry / Q000235:genetics; D004338:Drug Combinations; D004351:Drug Resistance; D019143:Evolution, Molecular; D006239:Haplotypes; D006801:Humans; D016778:Malaria, Falciparum / Q000469:parasitology; D008969:Molecular Sequence Data; D009154:Mutation; D010963:Plasmodium falciparum / Q000145:classification / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics*; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics; D011739:Pyrimethamine / Q000494:pharmacology*; D013413:Sulfadoxine / Q000494:pharmacology*; D013762:Tetrahydrofolate Dehydrogenase / Q000737:chemistry / Q000235:genetics
D000962:Antimalarials; D004338:Drug Combinations; D015800:Protozoan Proteins; C001205:fanasil, pyrimethamine drug combination; D013413:Sulfadoxine; D013762:Tetrahydrofolate Dehydrogenase; D004094:Dihydropteroate Synthase; D011739:Pyrimethamine
Plasmodium falciparum; dhfr/dhps; drug resistance; molecular evolution; order of mutational accumulations; sulfadoxine/pyrimethamine