An amino acid substitution in Fasciola hepatica P-glycoprotein from triclabendazole-resistant and triclabendazole-susceptible populations

Control of fasciolosis is threatened by the development of anthelmintic resistance. Enhanced triclabendazole (TCBZ) efflux by ABC transporters such as P-glycoprotein (Pgp) has been implicated in this process. A putative full length cDNA coding for a Pgp expressed in adult Fasciola hepatica has been constructed and used to design a primer set capable of amplifying a region encoding part of the second nucleotide binding domain of Pgp when genomic DNA was used as a template. Application of this primer set to genomic DNA from TCBZ-resistant and -susceptible field populations has shown a significant difference in the alleles present. Analysis of an allele occurring at a three-fold higher frequency in the “resistant” population revealed that it was characterised by a serine to arginine substitution at residue 1144. Homology modelling studies have been used to locate this site in the Pgp structure and hence assess its potential to modify functional activity.

Ribbon model of liver fluke P-glycoprotein with arginine substitution at residue 1144.Figure optionsDownload high-quality image (131 K)Download as PowerPoint slideHighlights
► Triclabendazole-resistant liver flukes differ in their P-glycoprotein genes.
► Triclabendazole-resistant flukes have greater allelic diversity.
► Triclabendazole resistance correlates with a change in the P-glycoprotein X-loop.
► This may provide the basis for a test for triclabendazole resistance.