Flukicide effects in the juvenile liver fluke, Fasciola hepatica

Abstract

This thesis exploits advances in the in vitro culture of juvenile liver fluke to characterise the response to triclabendazole (TCBZ), its active metabolite triclabendazole sulfoxide (TCBZ.SO), and rafoxanide. The results highlight differences in the responses of different fluke isolates and juveniles at different developmental stages. Drug susceptibility was found to be multi-factorial, with in vitro delineation of TCBZ-resistant (TCBZ-R) and susceptible (TCBZ-S) isolates exposing diversity in juvenile fluke motility, growth and survival phenotypic responses to drug treatments. The results also provided evidence that informed drug action, supporting a microtubule-inhibiting mode of action for TCBZ and TCBZ.SO and a metabolism-interfering mode of action for rafoxanide. It was also shown that TCBZ and the active metabolite inhibit the proliferation of neoblast-like cells in the TCBZ-S isolate irrespective of age, exposing neoblasts as a potential source of repair in TCBZ-R isolates, and as such, a potential target in fluke control. Subsequently, it was shown that the TCBZ-susceptibility status of juvenile fluke could be altered through the manipulation of neoblast-like cell proliferation and growth dynamics. Exploiting RNA-interference (RNAi) to silence Fasciola hepatica polo-like kinase 1 (FhPLK1) inhibited neoblast-like cell proliferation to significantly decrease growth and survival of the TCBZ-R isolate, transforming its in vitro phenotype to one that more closely resembled the TCBZ-S isolate. RNAi-induced silencing of neuropeptide F (FhNPF4) resulted in an enhanced growth phenotype and increased survival, transforming the phenotype of the TCBZ-S isolate to one that more closely resembled the TCBZ-R phenotype. Overall, this thesis has contributed to our understanding of the F. hepatica flukicide response, providing evidence in support of drug mode of action and the potential mechanism(s) of fluke resistance to identify novel targets for fluke control.

Thesis is embargoed until 31 July 2027.

Date of Award	Jul 2024
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Northern Ireland Department for the Economy
Supervisor	Aaron Maule (Supervisor) & Nikki Marks (Supervisor)