Parasite viability time-course in response to various concentrations of drugs.

<p><b>A</b>. <i>P. falciparum</i> viability time-course profiles for atovaquone, pyrimethamine, and artemisinin at concentrations corresponding to 1×, 3×, 10×, and 100× their respective IC₅₀. Error bars are SEM of at least 4 independent experiments. <b>B</b>. Values represented in panel A. No PRR or 99.9% PCT could be calculated for the 1× IC₅₀ conditions.</p

Comparison of metabolic and viability assays.

<p><b>A</b>. <i>P. falciparum</i> radio-labeled hypoxanthine incorporations after 48 hours of drug treatment at concentrations corresponding to 10× IC₅₀ with artemisinin, atovaquone, and azithromycin, reported as percentages of untreated controls. Data are averages of 12 repetitions from two independent experiments <b>B</b>. <i>P. falciparum</i> viability after 48 hours of drug treatment at concentrations corresponding to 10× IC₅₀ with artemisinin, atovaquone, and azithromycin, reported as number of viable parasite, as determined by limiting serial dilutions. Data are averages of 4 independent experiments. In both panels, error bars represent the standard error of the mean (SEM).</p

Parasite viability in response to various classical antimalarial drugs.

<p><b>A. </b><i>P. falciparum</i> viability time-course profiles for chloroquine (chq), mefloquine (mef), piperaquine (pip), artemisinin (art), lumefantrine (lum), pyronaridine (pyro), pyrimethamine (pyri), and atovaquone (ato). Error bars represent the SEM of at least 4 independent experiments. <b>B</b>. and <b>C</b>. Scatter plots of the compounds tested reporting the IC₅₀ versus the log(PRR) and 99.9% PCT, respectively. The dotted line in panel B is a log linear regression, the slope thereof is not significantly different from zero (<i>p</i> = 0.48). Data of panel C do not converge enough to establish a regression line.</p

Parasite viability correlates with the mode-of-action of antimalarials.

<p><i>P. falciparum</i> viability time-course profiles for artemisinin, atovaquone, GW648495, and GW844520 measured at 0, 24, 48, 72, 96, and 120 hours. Artemether and artesunate have been investigated at 24 hours only. Error bars are SEM of at least 4 independent experiments.</p

<i>In vitro</i> parasite reduction ratio and clearance time in response to classical antimalarial drugs.

a<p>estimation based on the first 24 hours of treatment.</p

Schematic representation of the <i>in vitro</i> PRR assay.

<p><b>A</b>. Intraerythrocytic <i>P. falciparum</i> cultured at 0.5% parasitemia and 2% hematocrit is treated with drugs. The medium is exchanged and the drug replenished every 24 hours. Aliquots corresponding to 10⁵ parasites are taken out at defined time points, washed, and free-drug parasites cultured with fresh erythrocytes under limiting serial dilution conditions (see Material and Methods). Parasite growth is subsequently monitored after 21 days and confirmed after 28 days, allowing to calculate the initial number of viable parasite in the aliquot. <b>B</b>. Parasite viability measurement allows in turn to determine the drug lag phase (i.e. time needed to reach the maximal rate of killing), PRR over one life cycle, and 99.9% PCT (i.e. the time needed to decrease the number of viable parasites by 3 –log units). The data presented in this panel are for illustration purpose only. Axe Y shows log (viable parasites +1) to allow representation of logarithms when counting of number of viable parasites is equal to zero.</p

Single time-point viability measurement.

<p><i>P. falciparum</i> viability after 72 hours of treatment with the indicated drugs, reported as the log of viable parasite+1, as compared to the untreated controls. The red line represents the threshold of 99.9% parasite reduction. The data are representative of at least 3 independent experiments.</p