Fig. 1.

Effect of transient hypothermia on ring-stage artemisinin susceptibility of P. falciparum (3D7). A. Ring-stage survival (proportion of control) of DHA pulse-treated 3D7 parasites (black circles) transiently incubated at hypothermic and normothermic temperatures. Open circles represent RSA survival estimates, in our hands, for previously described Cambodian parasite lines Cam 3.11 (reduced DHA susceptibility) and Cam 3.11^REV (fully DHA susceptible) (Straimer et al., 2014), with corresponding K13 genotypes in superscript. P value was estimated by two-sided t-test between 17 °C (n = 4) and 37 °C (n = 6) (mean difference 58.7% survival; 95% CI 57.7–59.8% survival; 8 d.f.).B. Effects of temperature modulation on 3D7 parasite proliferation in the absence of drug. Relative drug-free parasitaemia of temperature-pulsed parasite cultures was measured 72 h post-invasion as a proportion of the parasitaemia of parallel cultures incubated at 37 °C for the duration of the experiment. Each data point in A and B represents the mean of at least four biological replicates at each temperature, each performed in technical duplicate, with standard error. Each technical replicate enumerates at least 100,000 gate-stopping events by flow cytometry.C. Effects of transient (3–7 h post-invasion) incubation at hypothermic temperature on parasite susceptibility to a 48-h exposure to chloroquine.

Mean of at least three biological replicates is shown, each performed in technical duplicate; standard error is shown.