Efficient Oral Priming of Tenebrio molitor Larvae Using Heat-Inactivated Microorganisms

Microbial resistance is a global health problem that will increase over time. Advances in insect antimicrobial peptides (AMPs) offer a powerful new approach to combat antimicrobial resistance. Invertebrates represent a rich group of animals for the discovery of new antimicrobial agents due to their high diversity and the presence of adaptive immunity or “immune priming”. Here, we report a priming approach for Tenebrio molitor that simulates natural infection via the oral route. This oral administration has the advantage of minimizing the stress caused by conventional priming techniques and could be a viable method for mealworm immunity studies. When using inactivated microorganisms for oral priming, our results showed an increased survival of T. molitor larvae after exposure to various pathogens. This finding was consistent with the induction of antimicrobial activity in the hemolymph of primed larvae. Interestingly, the hemolymph of larvae orally primed with Escherichia coli showed constitutive activity against Staphylococcus aureus and heterologous activity for other Gram-negative bacteria, such as Salmonella enterica. The priming of T. molitor is generally performed via injection of the microorganism. To our knowledge, this is the first report describing the oral administration of heat-inactivated microorganisms for priming mealworms. This technique has the advantage of reducing the stress that occurs with the conventional methods for priming vertebrates.This research was funded by projects APOGEO (Cooperation Program INTERREG-MAC 2014–2020, with European Funds for Regional Development-FEDER. “Agencia Canaria de Investigación, Innovación y Sociedad de la Información (ACIISI) del Gobierno de Canarias” (Project ProID2020010134), CajaCanarias (Project 2019SP43). M.R.L. is currently funded by theCabildo de Tenerife, under the TFinnova Programme, supported byMEDI and FDCAN funds (project number 19-0231). A.O.-P. and P.A.-C. are recipients of pre-doctoral contracts from the “Agencia Canaria de Investigación, Innovación y Sociedad de la Información (ACIISI) del Gobierno de Canarias”. V.B.-G. is a recipient of a pre-doctoral contract funded by the Spanish Ministry of Education under the FPU program. A.M.-d. is a recipient of a postdoctoral Marie Curie fellowship under grant agreement 101030604 (IGYMERA).Peer reviewe