The soluble glutathione transferase superfamily: Role of Mu class in Triclabendazole sulphoxide challenge in Fasciola hepatica

Fasciola hepatica (liver fluke), a significant threat to food security, causes global economic loss for the livestock production industry and is re-emerging as a food borne disease of humans. In the absence of vaccines the commonly used method of treatment control is by anthelmintics; with only Triclabendazole (TCBZ) currently effective against all stages of F. hepatica in livestock and humans. There is widespread resistance to TCBZ and detoxification by flukes might contribute to the mechanism. However, there is limited Phase I capacity in adult parasitic helminths and the major Phase II detoxification system in adults is the soluble Glutathione transferases (GST) superfamily. Previous global proteomic studies have shown that the levels of Mu class GST from pooled F. hepatica parasites respond under TCBZ-Sulphoxide (TCBZ-SO), the likely active metabolite, challenge during in vitro culture ex-host. We have extended this finding by using a sub-proteomic lead approach to measure the change in the total soluble GST profile (GST-ome) of individual TCBZ susceptible F. hepatica on TCBZ-SO-exposure in vitro culture. TCBZ-SO exposure demonstrated a FhGST-Mu29 and FhGST-Mu26 response following affinity purification using both GSH and S-hexyl GSH affinity resins. Furthermore, a low affinity Mu class GST (FhGST-Mu5) has been identified and recombinantly expressed and represents a novel low affinity mu class GST. Low affinity GST isoforms within the GST-ome was not limited to FhGST-Mu5 with second likely low affinity sigma class GST (FhGST-S2) uncovered through genome analysis. This study represents the most complete Fasciola GST-ome generated to date and has supported the sub proteomic analysis on individual adult flukes.