Antimicrobial defence and persistent infection in insects revisited

Abstract

Insects show long-lasting antimicrobial immune responses that follow the initial fast-acting cellular processes. These immune responses are discussed to provide a form of phrophylaxis and/or to serve as a safety measure against persisting infections. The duration and components of such long-lasting responses have rarely been studied in detail, a necessary prerequisite to understand their adaptive value. Here, we present a 21 day proteomic time course of the mealworm beetle Tenebrio molitor immune-challenged with heat-killed Staphylococcus aureus . The most upregulated peptides are antimicrobial peptides (AMPs), many of which are still highly abundant 21 days after infection. The identified AMPs included toll and imd-mediated AMPs, a significant number of which have no known function against S. aureus or other Gram-positive bacteria. The proteome reflects the selective arena for bacterial infections. The results also corroborate the notion of synergistic interactions in vivo that are difficult to model in vitro . This article is part of the themed issue ‘Evolutionary ecology of arthropod antimicrobial peptides’.