Comparison of isoenzyme profiles of Toxoplasma gondii tachyzoites produced under different culture conditions.

The isoenzyme profiles for ten enzymes of tachyzoites either grown in vivo in TG 180 mouse sarcoma cells or cultivated in vitro in human fibroblast cell culture were compared in eight cloned strains by means of isoelectric focusing in polyacrylamide gels. Fibroblast-cultivated tachyzoites of all strains tested showed an extra band in the LDH isoenzyme pattern that was not seen in tachyzoites from TG 180 mouse sarcoma cells. The isoenzyme patterns of four enzymes [aspartate aminotransferase (ASAT), glutathione reductase (GSR), glucose phosphate isomerase (GPI) and amylase] used to differentiate the strains did not change under the two different culture conditions. Nevertheless, the shift observed in the LDH isoenzyme pattern underlines the fact that isoenzyme analysis of Toxoplasma strains could be carried out with tachyzoites produced under the same culture conditions.