Figure 6. Zaprinast does not prevent invasion.

Cultures containing mature schizonts (∼5% parasitaemia) were incubated in the absence (green) or presence (red and blue plots) of C1 (2.5 µM). After 160 min (arrowed), all cultures were washed and recultured in fresh medium minus C1, but with the addition of zaprinast (75 µM) to one culture (blue). Appearance of rings was monitored with time. Within 30 min following the wash and reculture step, the parasitaemia profiles had merged, demonstrating rapid invasion immediately following release of the C1 block, regardless of the presence of zaprinast. The subsequent relatively slow increase in parasitaemia in the zaprinast-containing culture (blue) likely reflects premature egress of the small number of residual immature schizonts still present at the point of reculture, which would release non-invasive merozoites. Time-points at which statistically different parasitaemia values were obtained for the two cultures which had been subjected to the C1 block are indicated with asterisks (Student's unpaired t-test, two-tailed P value = 0.0024 [225 min time-point] and P value = 0.0045 [285 min time-point]). Data are presented as mean values of triplicate counts ±SD. See also Figure S6 in Text S1.