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

MATÉ L.; BALLENT, M.; CANTON, C.; CEBALLOS L; LIFSCHITZ A.; LANUSSE C; ALVAREZ L; LIRÓN, JUAN PEDRO

VETERINARY PARASITOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2018

0304-4017

The efflux transporter P-glycoprotein (P-gp) has been implicated in multidrug resistance of nematodes affecting livestock species. Increased expression of P-gp in nematodes after in vitro as well as in vivo exposure to anthelmintics suggests a role of P-gp in drug resistance. The present work evaluated the P-gp gene expression in a highly-resistant isolate of the ovine gastrointestinal nematode Haemonchus contortus, selected after exposure to treatment at 10-fold the therapeutic dose of ivermectin (IVM), a macrocyclic lactone (ML) anthelmintic. Four lambs were artificially infected with larvae 3 (7.000 L3/animal). Adult parasites were collected at 0 (untreated), 6, 12 and 24 h post-oral IVM (2 mg/kg) treatment. The relative transcription levels of different H. contortus P-gp genes were studied by quantitative real-time PCR (qPCR) and confirmed by RNA-seq. P-gp1 and P-gp11 gene expression do not change throughout the experimental sampling period. P-gp3 and P-gp9.1 transcripts were decreased significantly at both 12 and 24 h post IVM exposure. Interestingly, even if P-gp2 expression was progressively increased in a time-dependent manner at 1.81 (6h), 2.08 (12h) and 2.49 (24h) -folds compared to the adult parasites not exposure (control 0 h) to IVM, there were not statistically differences (P>0.05). P-gp12 was not detected neither by qPCR nor RNA-seq analysis. These relatively modest changes in the P-gp gene expression alone could not be sufficient to explain the high level of IVM resistance displayed by the H. contortus isolate here analyzed. Overexpression of membrane drug transporters including P-gp has been associated with IVM resistance in different nematodes, however, some evidence suggests that resistance to ML may develop by multiple mechanisms. Further studies are needed to improve the understanding of resistance mechanisms in adult stages of H. contortus. Key words: nematode resistance, ivermectin, Haemonchus contortus, P-glycoprotein.