Small mammals like mice or rats are indispensable for preclinical research. However, growing ethical concerns led to the incorporation of the 3R principle (replacement, reduction, and refinement)1 into animal experiments legislation and research funding2. In the future, the number of vertebrate laboratory animals should be reduced, and non-vertebrate alternatives should be used where possible. Furthermore, the incorporation of the 3R principle will also economize preclinical research since insect husbandry is much cheaper than the traditional housing of laboratory mammals.
In that context, insect larvae like Manduca can serve as an alternative in vivo animal model. Particularly, with the high degree of evolutionary conservation in the innate immunity of the gut and similarities in the enteric epithelial structure3, lepidopteran larvae like Manduca sexta can serve as a model for human gut inflammation4,5.
In the introduced paper, we employed larvae of the tobacco hornworm Manduca sexta, which are big enough for macroscopic imaging techniques, such as computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) as a high-throughput platform to study the innate immunity of the gut and host-pathogen interactions.
The developed platform represents an ethically acceptable, resource-saving, large-scale, and 3R-compatible screening tool for various life science disciplines, including the identification of new effectors and inhibitors in gut inflammation, the assessment of pesticides or other environmental factors, the assessment and evaluation of new antibiotic therapies, the analysis of host-pathogen interactions, and the identification of new contrast agents or tracers in radiology. Since 75% of the known human disease-causing genes have homologs in insects, this approach will also be helpful in testing preclinical hypotheses in inflammatory bowel disease6.
1 Balls, M., Russell, W. M. S. & Burch, R. L. three Rs and the humanity criterion. (FRAME, 2009).
2 Hubrecht, R. C. & Carter, E. The 3Rs and humane experimental technique: implementing change. Animals 9, 754, (2019).
3 Galenza, A. & Foley, E. Immunometabolism: insights from the Drosophila model. Dev. Comp. Immunol.94, 22-34, (2019).
4 Lange, A., Schäfer, A., Bender, A., Steimle, A., Beier, S., Parusel, R. & Frick, J.-S. Galleria mellonella: a novel invertebrate model to distinguish intestinal symbionts from pathobionts. Front. Immunol. 9, 2114, (2018).
5 Emery, H., Johnston, R., Rowley, A. F. & Coates, C. J. Indomethacin-induced gut damage in a surrogate insect model, Galleria mellonella. Arch. Toxicol. 93, 2347-2360, (2019).
6 Reiter, L. T., Potocki, L., Chien, S., Gribskov, M. & Bier, E. A systematic analysis of human disease-associated gene sequences in Drosophila melanogaster. Genome Res. 11, 1114-1125, (2001).