Host effects on glutathione S-transferase activity in Fasciola hepatica

Glutathione S-transferases (GST, E.C. 2.5.1.18) in Fasciola hepatica from sheep were previously found to be extremely variable with regard to specific GST activity and isoenzyme profile within and between parasite isolates. The effect of the host on GST activity and isoenzyme profile was examined by infecting mice, rats and cattle as well as sheep with one or the other of two isolates--either salicylanilide-resistant or salicylanilide-susceptible F. hepatica. In the case of both isolates, GST activity in hosts relatively resistant to reinfection--rats and cattle--was lower and more restricted in range compared with hosts susceptible to multiple infection--mice and sheep. In the case of the rat flukes, there was little variation in isozyme profiles whereas cattle flukes appeared to exhibit more variation than sheep flukes. In mice, despite the apparent variability in GST activity, only one GST band was found in the isoenzyme profiles. Therefore, the host appears to exert a pronounced effect on the activity and expression of GSTs in F. hepatica which may be related to variation in the immune responses of the different hosts during infection.