Calibration of an in vitro assay system using a non-adherent cell line to evaluate the effect of a drug on Toxoplasma gondii

A TG 180 non-adherent cell culture with Toxoplasma gondii and spiramycin was performed in order to calibrate TG 180 cells used in a therapeutic assay system. TG 180 cells were infected with the RH strain of T. gondii, and spiramycin was added at final concentrations of 1, 2, 4, 8, 12, 16, 20 and 25 μg/ml. A least-squares linear regression with confidence interval was calculated from the experimental curve and allowed the determination of the 50% inhibitory concentration of spiramycin. The IC 50 of 13.7 μg/ml obtained is comparable with the results of the literature. The system including TG 180 cells (recently cultured in vitro) provides a rapid, accurate and economical determination of the effects of a drug on Toxoplasma gondii.