Functional validation of the truncated UNC-63 acetylcholine receptor subunit in levamisole resistance

International audienceLevamisole is a broad-spectrum anthelmintic which permanently activates cholinergic receptors from nematodes, inducing a spastic paralysis of the worms. Whereas this molecule is widely used to control parasitic nematodes impacting livestock, its efficacy is compromised by the emergence of drug-resistant parasites. In that respect, there is an urgent need to identify and validate molecular markers associated with resistance. Previous transcriptomic analyses revealed truncated cholinergic receptor subunits as potential levamisole resistance markers in the trichostrongylid nematodes Haemonchus contortus, Telodorsagia circumcincta and Trichostrongylus colubriformis. In the present study we used the Xenopus oocyte, as well as the free-living model nematode Caenorhabditis elegans, as heterologous expression systems to functionally investigate truncated isoforms of the levamisole-sensitive acetylcholine receptor (L-AChR) UNC-63 subunit. In the Xenopus oocyte, we report that truncated UNC-63 from C. elegans has a strong dominant negative effect on the expression of the recombinant C. elegans L-AChRs. In addition, we show that when expressed in C. elegans muscle cells, truncated UNC-63 induces a drastic reduction in levamisole susceptibility in transgenic worms, thus providing the first known functional validation for this molecular marker in vivo

Investigating anthelmintic mode of action and resistance using the Xenopus oocyte as a heterologous expression system

The control of parasitic nematode infections in humans, livestock and companion animals is critically dependent on anthelmintic treatment. However, the indiscriminate use of anthelmintic drugs has inevitably led to the selection of resistant parasites. Most of the currently available anthelmintic drug classes target ion-channels. By permanently activating or inhibiting these ion channels, anthelmintics induce a paralysis of the worms. Our ability to identify and characterize ion-channels targeted by anthelmintics in parasitic nematode species mainly relies on C. elegans data and the use of the African frog (Xenopus laevis) oocyte as a heterologous expression system. However, there is a need for complementary approaches to validate “in wormo” the results obtained from the experiments carried out on the Xenopus oocyte. In the present talk, advantages and limitations of the use of a vertebrate oocyte as an expression system for parasitic nematode ion-channels will be discussed

Investigating and monitoring anthelmintic resistance: from molecular markers to High Throughput diagnosis tools

International audienceThe control of parasitic nematode infections in humans, livestock and companion animals is critically dependent on anthelmintic treatment. However, the indiscriminate use of anthelmintic drugs has inevitably led to the selection of resistant parasites. In this presentation, identification and functional validation of molecular markers associated with resistance will be presented, opening a discussion about advantages and limitations of the use of C. elegans as model for parasitic species. In addition, as diagnosis tools are of particular interest to monitor resistance spreading and refine strategies for the control resistant parasites, recent advances in automated phenotypic assays performed on larval stages of the parasite will be discusse

The Brown Alga <i>Bifurcaria bifurcata</i> Presents an Anthelmintic Activity on All Developmental Stages of the Parasitic Nematode <i>Heligmosomoides polygyrus bakeri</i>

The current control of gastrointestinal (GI) parasitic nematodes mainly relies on the widespread use of anthelmintics, which has inevitably led to resistance. Therefore, there is an urgent need to find new sources of antiparasitic compounds. Macroalgae represent a rich source of active molecules and are widely described as having medicinal properties. In the present study, we investigated the potential anthelmintic activity of aqueous extracts from three species of algae (Bifurcaria bifurcata, Grateloupia turuturu and Osmundea pinnatifida) on the murine parasite Heligmosomoides polygyrus bakeri. Using a set of complementary in vitro tests, including larval development assays, egg hatching tests and nematicidal activity assays on larvae and adults, we report the nematicidal activity of aqueous extracts of B. bifurcata. In addition, aqueous extract fractionation using liquid/liquid partitioning with a solvent of increasing polarity was performed in order to identify the groups of active molecules underlying the anthelmintic activity. Non-polar extracts (heptane, ethyl acetate) demonstrated high anthelmintic potential, highlighting the role of non-polar metabolites such as terpenes. Here, we highlight the strong anthelmintic potential of the brown alga B. bifurcata on a mouse model of GI parasites, thus confirming the strong interest in algae as natural alternatives for the control of parasitic nematodes