期刊
INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE
卷 2, 期 -, 页码 154-161出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.ijpddr.2012.03.005
关键词
Teladorsagia circumcincta; Sheep; Anthelmintic resistance; Ivermectin; GluCl channels
资金
- national projects INIA-MEC [RTA2006-00183-C03-02, RTA2010-00094-C03-02]
- Consejo Superior de Investigaciones Cientificas (CSIC)
- European Social Fund
- Scottish Government Rural and Environmental Research and Analysis Directorate (RERAD)
Individual mutations (e. g. L256F) and polymorphisms in the avr-14B gene, a glutamate-gated chloride channel subunit, have been associated with ivermectin (IVM) resistance in Caenorhabditis elegans and Cooperia oncophora. The aim of the present study was to determine the full-length coding sequence of the avr-14B subunit homologue in Teladorsagia circumcincta and determine the presence/absence of the putative L256F SNP or any other potential SNPs of interest. Subsequently, we investigated sequence polymorphisms and transcription patterns between four different T. circumcincta isolates: two from Scotland (MTci1 susceptible and MTci5 triple resistant to benzimidazoles, levamisole and IVM) and two from Spain (S-Sp susceptible and R-Sp double resistant to levamisole and IVM). The complete amino acid sequence of the T. circumcincta avr-14B subunit comprises 438 amino acids. Pyrosequencing analysis failed to detect the presence of the L256F mutation in any of the MTci5 or Sp-R samples tested. However, we revealed significant allele frequency changes by means of SSCP analysis of a 106 bp region encompassing the L256F SNP. Allele E showed the greatest change, following IVM exposure in vitro and in vivo, although sequence analysis did not reveal any coding changes. Sequence analysis of the full-length avr-14B coding sequence showed that two SNPs exclusively found in the resistant strain McTi5 (I270F and T305A) are situated in codons involved in the interaction of the receptor with IVM. Moreover, other potentially significant SNPs (K361E and L364M) were identified between transmembrane regions 3 and 4. However, due to the low frequency of all these SNPs, we cannot conclude they confer IVM resistance in T. circumcincta. Moreover, a modest increase in expression of the avr-14B in both resistant isolates has been shown although these differences were not sufficiently great to consider avr-14B to be the sole or even a major determinant of IVM resistance in this species. (C) 2012 Australian Society for Parasitology Published by Elsevier Ltd. All rights reserved.
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