Invited Speaker 11th Asia-Pacific Congress of the International Society on Toxinology 2021

Ponericins - stinging ant peptides with broad-spectrum bioactivities (#25)

Samantha A Nixon 1 2 3 , Samuel D Robinson 1 , Akello J Agwa 1 4 , Andrew A Walker 1 3 , Shivani Choudhary 5 , Axel Touchard 6 , Eivind AB Undheim 7 , Alan Robertson 5 , Irina Vetter 1 8 , Christina I Schroeder 1 4 , Andrew C Kotze 2 , Volker Herzig 1 9 , Glenn F King 1 3
  1. Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
  2. CSIRO Agriculture and Food, St Lucia, QLD, Australia
  3. Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, The University of Queensland, St Lucia, QLD, Australia
  4. National Cancer Institute, National Institutes of Health, Frederick, MD, USA
  5. Department of Biomedical Science, College of Veterinary Medicine, Iowa State University, Ames, IA, USA
  6. CNRS, UMR EcoFoG, AgroParis Tech, INRAE, Université des Antilles, Université de Guyane, , Kourou, France
  7. Department of Biology, Centre for Biodiversity Dynamics, NTNU, Trondheim, Norway
  8. School of Pharmacy, The University of Queensland, Woolloongabba, QLD, Australia
  9. GeneCology Research Centre & School of Science, Technology and Engineering, University of the Sunshine Coast, Sippy Downs, QLD, Australia

In the face of increasing drug resistance, the development of new anthelmintics is critical for controlling nematodes that parasitise livestock. Although venom toxins have attracted attention for applications in agriculture and medicine, few studies have explored their potential as anthelmintics. Here we explored invertebrate venoms as a possible source of new anthelmintic compounds by screening over 250 crude venoms from a diverse panel of spiders, scorpions, assassin bugs, caterpillars, marine snails, ants and wasps for anthelmintic activity against the blood-feeding small ruminant nematode Haemonchus contortus in a larval development assay. At 0.2 mg/ml crude venom the hit rate for the screen was 20.6%, with hits dominated by arthropod venoms, particularly tarantulas and ants. Using bioassay-guided fractionation coupled with liquid chromatography-tandem mass spectrometry, we identified four novel anthelmintic peptides (ponericins) from the venom of the neotropical ant Neoponera commutata and the previously described ponericin M-PONTX-Na1b from Neoponera apicalis venom. These peptides were synthesised and found to inhibit H. contortus development with IC50 values of 2.8–5.6 µM. Circular dichroism spectropolarimetry indicated that the ponericins are unstructured in aqueous solution but adopt α-helical conformations in lipid mimetic environments. We show that the ponericins induce non-specific membrane perturbation, which confers broad-spectrum antimicrobial, insecticidal, cytotoxic, haemolytic, and algogenic activities, with activity across all assays typically correlated. We also show for the first time that ponericins induce spontaneous pain behaviour when injected in mice. We propose that the broad-spectrum activity of the ponericins enables them to play both a predatory and defensive role in neoponeran ants, consistent with their high abundance in venom. This study reveals a much broader functionality for ponericins than previously assumed, and highlights both the opportunities and challenges in pursuing ant venom peptides as potential therapeutics.