AlGusbi, S

Demeler, Janina

Geldhof, Peter

Krücken, J

Pomroy, WE

Vercruysse, Jozef

von Samson-Himmelstjerna, G

Ghent University Academic Bibliography

Characterization of non-specific resistance mechanisms against ivermectin in Cooperia oncophora   J. Demeler1, S. AlGusbi1, J. Krücken1, W. E Pomroy2, P. Geldhof3, J. Vercruysse3, G. von Samson-Himmelstjerna1 1Institute for Parasitology and Tropical Veterinary Medicine, Freie Universität Berlin, Germany; 2 Massey University, Institute of Veterinary, Animal and Biomedical Sciences, Palmerston North, New Zealand; 3Ghent University, Faculty of Veterinary Medicine, Laboratory for Parasitology, Merelbeke, Belgium   Background: While facing increasing anthelmintic resistance, knowledge about resistance mechanism becomes crucial. Despite its importance, for resistance to macrocyclic lactones this still remains unresolved. Non-specific mechanisms of resistance involving transporters, e.g. P-glycoproteins (Pgps), or inactivating enzymes, e.g. Cytochrome P450s (CyP450s), are believed to play an important role. Nematodes have a complex repertoire of both protein classes. It is currently unknown, which transporter or enzyme system is associated with resistance to certain anthelmintics. The cattle nematode Cooperia oncophora was used as a model to study contribution of both, CyP450s and two individual Pgps, to the development of resistance in more detail. Methods: The response of susceptible and ML-resistant isolates of C. oncophora to ivermectin were evaluated in vitro in the presence of Pgp and CyP450-inhibitors verapamil hydrochloride (VPL) and piperonyl butoxide (PBO), respectively,. Full-length Pgp cDNAs were cloned following amplification by RT-PCR and RACE-PCR. Sequence variation of two Pgps was compared between six C. oncophora isolates with different resistance status by SeqDoc-analysis. Inducibility of Pgp transcript level by ivermectin was analysed by real-time RT-PCR. Results: In the presence of VPL and PBO the susceptibility of all tested isolates to ivermectin was significantly increased in the in vitro assays measuring development (100-fold) or motility (10-fold). Comparison of full length Pgp-2 and Pgp-3 (currently 65% of the sequence analysed) sequences between C. oncophora isolates revealed no major differences correlating with resistance though sequence variability was generally lower in resistant isolates. Preliminary results indicate only minor differences in Pgp-2 expression levels between C. oncophora isolates. Expression of Pgp-3 and inducibility of both Pgps by ivermectin are currently examined. Summary/Conclusions: Though these data indicate that degradation and extrusion as non-specific xenobiotic detoxification mechanisms are both involved in ivermectin-resistance in C. oncophora, identification of the relevant genes still remains problematic. The characterised panel of C. oncophora isolates nevertheless provides a useful tool for further analyses of specific Pgp and CyP450 genes and their possible contribution to ivermectin efflux and metabolism.  

Characterization of non-specific resistance mechanisms against ivermectin in Cooperia oncophora

https://biblio.ugent.be/publication/2034533/file/2034574

Characterization of non-specific resistance mechanisms against ivermectin in Cooperia oncophora

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Ghent University Academic Bibliography