Transcriptomic Analysis of ABCTransporters (P-GP, MRP and HAF) in Haemonchus Contortus Isolates With Different Susceptibility to IVM

Abstract

Inadequate and intensive use of anthelmintic compounds has led to the emergence of high levels of parasite resistance in nematodes of sheep. Changes in drug target sites and the up-regulation of detoxification systems seem to be implicated in this phenomenon. Several studies have shown that ATP-binding-cassette (ABC) transporters such as P-glycoprotein (P-gp) play an important role in multidrug resistance in many organisms, including several nematode species. The goals of the current work were: 1) to compare the gene expression of several cellular transporters in both a susceptible (S-IVM) and a highly ivermectin (IVM)-resistant Haemonchus contortus isolate (HR-IVM); 2) to assess the effect of IVM on ABC transporters expression patterns in the HR-IVM isolate under in vivo conditions. To this end, the transcriptional levels of ABC transporters in adult HR-IVM H. contortus recovered from IVM-treated lambs (2 mg/kg) at 12 and 24 hours post-treatment, were compared to those obtained from the S-IVM and HR-IVM specimens collected from untreated lambs. The phylogenetic tree with the transporter sequences of the reference nematode Caenorabditis elegans and H. contortus allowed us to found the putative orthologous genes P-gp 1, 2, 3, 9.1, 10, 11, 13, 16 and 17; MRP 3, 4, 7 and 8; and Haf 2, 3, 4, 6 and 9. Next generation sequencing analysis showed that both H. contortus isolates express 6 of the 9 P-gps, 3 of the 5 multi-drug resistant proteins (MRPs) and 4 of the 5 Half (HAF) transporter genes. Some of these ABC transporter genes are differentially expressed in the S and HR isolates. IVM treatment induced slight changes in the mRNA levels of MRP-4 and P-gp transporters, but the biological significance of the observed changes may not be enough to explain the high level of IVM resistance displayed by the isolate under study in the current trial.