A novel Plasmodium falciparum expression system for assessing antifolate resistance caused by mutant P. vivax dihydrofolate reductase-thymidylate synthase.
With the emergence of drug-resistant vivax malaria, in vitro studies are urgently needed to examine resistance mechanisms and for drug development. Currently, Plasmodium vivax culturing is inadequate for addressing these needs; therefore, surrogate biological systems have been developed. Although these systems are informative, they do not address Plasmodium species-specific mechanisms, such as drug delivery through erythrocytes and parasite membranes. Here, we demonstrate that P. falciparum is an excellent biological system for expression of P. vivax dhfr-ts alleles to assess dihydrofolate reductase (DHFR)-thymidylate synthase interactions with antifolates. Our results show that the P. vivax dhfr-ts quadruple-mutant allele AMRU1, expressed in P. falciparum, provides significant protection against pyrimethamine, cycloguanil, and clocicguanil. Moreover, the PvDHFR quadruple mutant confers greater resistance to cycloguanil, clociguanil, and WR99210 than the PfDHFR quadruple mutant. Modeling of both P. vivax and P. falciparum DHFR quadruple mutants suggests that mutations unique to P. vivax DHFR are responsible for differences seen in parasite susceptibility to antifolates.
O'Neil
Michael T
MT
Drug Resistance and Diagnostics, Australian Army Malaria Institute, Brisbane, Australia. michael.t.oneil@us.army.mil
Korsinczky
Michael L J
ML
Gresty
Karryn J
KJ
Auliff
Alyson
A
Cheng
Qin
Q
D000818:Animals; D030801:Animals, Genetically Modified; D000962:Antimalarials / Q000494:pharmacology*; D001665:Binding Sites; D004351:Drug Resistance; D005786:Gene Expression Regulation; D009154:Mutation; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000378:metabolism*; D010966:Plasmodium vivax / Q000201:enzymology*; D011487:Protein Conformation; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics* / Q000378:metabolism; D013940:Thymidylate Synthase / Q000235:genetics* / Q000378:metabolism
D000962:Antimalarials; D013762:Tetrahydrofolate Dehydrogenase; D013940:Thymidylate Synthase