DNA hybridization for assessment of response of Plasmodium falciparum to chloroquine therapy.

We studied the accuracy of PFR1-AP, a synthetic DNA hybridization probe conjugated to alkaline phosphatase, in monitoring Plasmodium falciparum parasitemia during in vivo drug susceptibility surveys. Duplicate blood samples were collected from six children enrolled in a 14-day in vivo chloroquine study in Rwanda. Results obtained by microscopic examination of Giemsa-stained thick blood smears and by DNA hybridization were compared. Both techniques successfully monitored an infection with chloroquine-susceptible parasites and infections exhibiting various levels of resistance to treatment. For each patient, temporal evolution of the microscopic parasite counts and the DNA hybridization signals were closely parallel, although a wide range of rapidly changing levels of parasitemia occurred through the course of the study. This suggests that DNA hybridization assay using PFR1-AP detects P. falciparum parasites sensitively and specifically and is a valuable tool for drug resistance surveys.