Freshly harvested tachyzoites were washed by centrifugation twice with invasion medium and resuspended in invasion medium at 4´107 parasitesmlÿ1. Parasites were pretreated for 10min at room temperature with 0±5mM staurosporine before they were assayed for invasion by immuno¯uorescence staining of infected HFF cells. To determine whether the effect of staurosporine was on the parasiteoronthehostcell,HFFcellsinsix-wellplateswere®xed with 2.5% (w/v) formaldehyde for 20min at 08C. Fixed HFF monolayers were washed three times with PBS, then stored overnight at 48C in PBS. HFF monolayers were washed three more times with PBS before being challenged with staurosporine-treated (1mM) 2F tachyzoites (8´106 per well) for 20min at 378C. Parasite invasion was quanti®ed by b-gal assay.