For example, Mu class Glutathione transferase (GSTs) have been widely investigated as vaccine candidates for fasciolosis [6] [7] [8] [9] . The Mu class GSTs have established roles in general Phase II detoxification of xenobiotic and endogenously derived toxins in F. hepatica within the host bile environment [10] . The general detoxification role is supported by GSTs contributing to 4% of the total soluble protein in F. hepatica, with a widespread tissue distribution. Proteomics and EST sequencing approaches have now delineated what members of the GST family are expressed in F. hepatica and two new classes of GST, Sigma and Omega, have been uncovered [11] . In the related trematode, Schistosoma mansoni, the Sigma class GST (Sm28) has generally shown more robust protection in vaccine trials against schistosome infection [12] , than the F. hepatica Mu GSTs against F. hepatica infection.