ASSESSMENT OF PFMDR-1 GENE COPY NUMBER BY TANDEM COMPETITIVE POLYMERASE-CHAIN-REACTION

The pfmdr1 gene encodes a Plasmodium falciparum homologue of the human P-glycoprotein expressed on the surface of the parasite food vacuole. Variation in copy number and specific codon mutations of pfmdr1 have been implicated in the development of parasite resistance to antimalar ial drugs. We describe here the technique of Tandem-Competitive Polyme rase Chain Reaction (TC-PCR), which allows accurate measurement of pfm dr1 copy number in parasite DNA obtained directly from small quantitie s (100 mu 1) of red blood cells. We reliably quantified pfmdr1 in prev iously well characterised strains of Plasmodium falciparum with differ ing pfmdr1 gene copy numbers using starting amounts of between 3000 an d 40 000 gene copies. We then used TC-PCR to determine pfmdr1 gene cop y number in field specimens of venous blood taken from 10 patients wit h malaria contracted along the Thai-Burmese border. In this region of high grade parasite resistance to mefloquine greater than 70% of sampl es had a copy number greater than 1 of pfmdr1 determined with a repeat ability coefficient of 0.58. (C) 1997 Elsevier Science B.V.