期刊
MOLECULAR AND BIOCHEMICAL PARASITOLOGY
卷 113, 期 1, 页码 139-150出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/S0166-6851(01)00207-9
关键词
DHFR; drug resistance; malaria
资金
- NIAID NIH HHS [AI42321, AI46065] Funding Source: Medline
Inhibitors of dihydrofolate reductase (DHFR) have been a mainstay of chemotherapy of falciparum malaria for > 50 years. Unfortunately, point mutations in DHFR are the major cause of resistance to drugs of this class and mutations have rapidly diminished the clinical effectiveness of these drugs. We designed a simple yeast-based system to produce and analyze point mutations in the Plasmodium falciparum DHFR domain of the DHFR-thymidylate synthase gene that confers resistance to pyrimethamine (PM), the major antifolate currently used in malaria treatment, or to WR99210, an experimental antifolate. We used PCR mutagenesis, screened > 1000 DHFR alleles that encoded functional enzymes and studied approximate to 100 that were more resistant than a naturally occurring resistant allele (N51I and S108N). The IC50 values for both drugs were determined fur a subset of 44 alleles that carried only a single new mutation. Mutations that increased resistance to PM 10- 100 fold (to > 10 (-4) M) were identified in three regions of the DHFR domain - around amino acids 50, 188 and 213. In contrast, mutations that caused WR-resistance were far less common and only conferred approximate to 10-fold resistance (to approximate to 10 (7) M). Even more interesting, only the mutations at 188 increased resistance to WR and mutations in the 213 and other regions either had no effect or actually increased sensitivity to WR. This collateral hypersensitivity raises the possibility that opposing selection for resistance/sensitivity to PM and WR might be used to slow selection of populations of P. falciparum resistant to antifolate treatment. (C) 2001 Elsevier Science B.V. All rights reserved.
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