Assessment of P-glycoprotein gene expression in adult stage of Haemonchus contortus in vivo exposed to ivermectin

MATÉ, L.; BALLENT, M.; CANTÓN, C.; CEBALLOS, L.; LIFSCHITZ, A.; LANUSSE, C.; ALVAREZ, L.; LIRÓN, J.P.

VETERINARY PARASITOLOGY

ELSEVIER SCIENCE BV

Año: 2018

0304-4017

The efflux transporter P-glycoprotein (P-gp) has been implicated in multidrug resistance ofdifferent nematode parasites affecting livestock species. Increased expression of P-gp innematodes after their in vitro as well as in vivo exposure to anthelmintics suggests a role of P-gpin drug resistance. The current work evaluated the P-gp gene expression in a highly-resistantisolate of the sheep nematode Haemonchus contortus, selected after exposure to ivermectin (IVM)treatments at 10-fold the therapeutic dose. Four lambs were artificially infected with L3 (7.000ACCEPTED MANUSCRIPT2L3/animal) of a previously selected IVM highly resistant H. contortus isolate. Forty five (45) daysafter infection, adult worms were collected at 0 (untreated), 6, 12 and 24 h post-oral IVM (2 mg/kg)administration. The relative transcription levels of different H. contortus P-gp genes were studiedby quantitative real-time PCR (qPCR) and confirmed by RNA-seq. P-gp1 and P-gp11 geneexpressions do not change throughout the experimental sampling period. P-gp3 and P-gp9.1transcripts decreased significantly at both 12 and 24 h post IVM exposure. P-gp2 expression wasprogressively increased in a time-dependent manner at 1.81 (6 h), 2.08 (12 h) and 2.49 (24 h) -fold compared to adult worms not exposed (control 0 h) to IVM, although without reachingstatistically significant differences (P>0.05). P-gp12 was neither detected by qPCR nor by RNAseqanalysis. These relatively modest changes in the P-gp gene expression could not be enoughto explain the high level of IVM resistance displayed by the H. contortus isolate under assessment.Overexpression of membrane drug transporters including P-gp has been associated with IVMresistance in different nematode parasites. However, some evidences suggest that resistance toIVM and other macrocyclic lactones may develop by multiple mechanisms. Further studies areneeded to improve the understanding of resistance mechanisms in adult stages of H. contortus.