Galleria mellonellaas a Model System for StudyingListeriaPathogenesis

Abstract

ABSTRACTEssential aspects of the innate immune response to microbial infection are conserved between insects and mammals. This has generated interest in using insects as model organisms to study host-microbe interactions. We used the greater wax mothGalleria mellonella, which can be reared at 37°C, as a model host for examining the virulence potential ofListeriaspp. Here we report thatGalleriais an excellent surrogate model of listerial septic infection, capable of clearly distinguishing between pathogenic and nonpathogenicListeriastrains and even between virulent and attenuatedListeria monocytogenesstrains. Virulence required listerial genes hitherto implicated in the mouse infection model and was linked to strong antimicrobial activities in both hemolymph and hemocytes of infected larvae. FollowingListeriainfection, the expression of immune defense genes such as those for lysozyme, galiomycin, gallerimycin, and insect metalloproteinase inhibitor (IMPI) was sequentially induced. Preinduction of antimicrobial activity by treatment of larvae with lipopolysaccharide (LPS) significantly improved survival against subsequentL. monocytogeneschallenge and strong antilisterial activity was detected in the hemolymph of LPS pretreated larvae. We conclude that the severity of septic infection withL. monocytogenesis modulated primarily by innate immune responses, and we suggest the use ofGalleriaas a relatively simple, nonmammalian model system that can be used to assess the virulence of strains ofListeriaspp. isolated from a wide variety of settings from both the clinic and the environment.