Beta-tubulin complementary DNA sequence variations observed between cyathostomins from benzimidazole-susceptible and -resistant populations.

This study aims to identify the molecular mechanism behind the resistance of certain horse parasites (cyathostomins) to benzimidazole (BZ), a commonly used anti-parasitic drug. Through genetic sequencing, comparisons revealed a specific mutation potentially influencing this resistance mechanism in a population of these parasites.

Study Overview

• The research is focussed on the resistance of a horse parasitic group, cyathostomins, to Benzimidazole (BZ), an anthelmintic (anti-parasitic) drug. The cyathostomins studied here include several species, amongst them Cylicocyclus nassatus, Cyathostomum pateratum, and Cyathostomum coronatum.
• The researchers recognized that the pathway to resistance is different in these horse-specific parasites compared to similar parasites in sheep, where a specific gene mutation is notably linked to the resistance.
• To precisely identify the mutated spot in the cyathostomins’ genes associated with BZ resistance, they sequenced full complementary DNA (cDNA), which is created from an mRNA template, for the beta-tubulin gene in adult worms isolated from a BZ-resistant cyathostomin population.

Methods and Key Findings

• The scientists used specific primers to characterize the cDNA sequences encoding beta-tubulin in the various cyathostomin species. The beta-tubulin gene was chosen because it codes for a protein that’s a significant drug target for BZ.
• Each species’ cDNA sequence spanned 1,429 base pairs, which is responsible for encoding a protein made of 448 amino acids. The sequences showed a high similarity (95.2% to 99.6%) on the genetic (nucleotide) level and an even higher similarity (98.7% to 100%) on the peptide (protein) level when compared across different species.
• However, a comparison between BZ-resistant and BZ-susceptible organisms revealed a difference in 11 amino acid positions.
• An important observation was a mutation from phenylalanine to tyrosine at position 167 in the beta-tubulin protein across all BZ-resistant species. It suggests that this mutation could be mainly driving the resistance to BZ in the horse parasites. However, more investigation would be required to confirm this.

Study Impact

• The findings provide a vital understanding of the potential molecular mechanism of BZ resistance in cyathostomins, a critical step towards tackling drug resistance in these parasites.
• Based on these new insights, drug targets could be re-evaluated and new therapeutic strategies could effectively be developed, ensuring the effective treatment and control of these equine parasites.