Protein purification of rFhGST-S1 and native F. hepatica GSTs rFhGST-S1 protein was purified according to the glutathione affinity chromatography method of Simons and Vander Jagt [34] from transformed E. coli cytosol following protein expression. Native GSTs were purified from F. hepatica soluble cytosolic supernatants as previously described [11] . Purity of rFhGST-S1 was assessed by electrospray ionisation (ESI) mass spectrometry, sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and 2DE according to LaCourse et al. [35] .