Effects of bumped kinase inhibitor 1517 (BKI-1517) on CDPK1 inhibition. A, CDPK1 expression in siCDPK- and siGP900-transfected parasites and wild type parasites treated only with transfection reagent (WT). B, Cryptosporidium oocyst containing wild type parasites were treated with only transfection reagent (WT), 1 µM of silencer complex siCDPK to knock down CDPK1, BKI-1517 (0.1 µM) alone, BKI-1517 plus siCDPK, BKI-1294 (0.1 µM) alone, or BKI-1294 plus siCDPK. Numbers of parasites were evaluated (gray bars). The results are the mean value (±SD) of 3 independent experiments evaluated by reverse-transcription polymerase chain reaction analysis. Asterisks denote statistically significant differences.