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UBC Theses and Dissertations

High throughput imaging for anthelmintic discovery and Caenorhabditis elegans genetic tools for target elucidation Mathew, Mark


Nearly three billion humans worldwide have helminth infections, which accounts for a global disease burden of 5.2 million disability-adjusted life years. Parasitic nematodes also have a great affect on agriculture, annually destroying 12.3% of global food crops and accounting for an annual loss of approximately $10 billion (USD) worldwide in the sheep and cattle industry. There is widespread resistance to all classes of anthelmintic drugs. The last drug to enter human clinical trials was 35 years ago. There is a great need for new anthelmintics and this concern has been strongly voiced by the World Health Organization and Gates Foundation. Anthelmintics are considered rare, which is why large chemical libraries are a necessity for anthelmintic discovery. I adapted my Caenorhabditis elegans high-throughput technique WormScan to overcome the bottleneck of whole organism screening for anthelmintic discovery. WormScan was used to screen a library of approximately 26,000 molecules. Hits were tested against diverse organisms to identify nematode specific compounds. I took into account preexisting drug resistance of the established anthelmintics. For every class of anthelmintics there is a corresponding C. elegans resistant strain. Screening the hits against these known resistant strains allowed me to determine if any of the compounds target a novel or established anthelmintic pathways. A forward genetic screen and C. elegans genetic tools were employed to identify the mechanism of action of the candidate D19. Molecular modelling was undertaken to elucidate the resistance mechanism and phylogenetic specificity of the D19. I undertook a structure activity relationship to identify structural moieties of D19 activity. The high throughput screen identified 14 new potential anthelmintics, 5 of which had nematode specificity, which indicates low toxic side effects in humans and limited environmental toxicity. Forward genetic screening and molecular modelling identified D19 to be a worm specific mitochondrial complex II inhibitor. The Structure Activity Relationship demonstrated the chemical features needed for D19 activity. C. elegans was used as a surrogate of parasitic nematodes for whole organism anthelmintic discovery. This thesis is a starting point to replenish the pipeline of potential nematicides. Future studies should focus on progressing these hits to a lead status.

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