Abstract
The fruit fly Drosophila melanogaster forms a magnificent model for interpreting conserved host innate immune signaling and functional processes in response to microbial assaults. In the broad research field of host-microbe interactions, model hosts are used in conjunction with a variety of pathogenic microorganisms to disentangle host immune system activities and microbial pathogenicity strategies. The pathogen Photorhabdus is considered an established model for analyzing bacterial virulence and symbiosis due to its unique life cycle that extends between two invertebrate hosts: an insect and a parasitic nematode. In recent years, particular focus has been given to the mechanistic participation of the D. melanogaster thioester-containing proteins (TEPs) in the overall immune capacity of the fly upon response against the pathogen Photorhabdus alone or in combination with its specific nematode vector Heterorhabditis bacteriophora. The original role of certain TEPs in the insect innate immune machinery was linked to the antibacterial and antiparasite reaction of the mosquito malaria vector Anopheles gambiae; however, revamped interest in the immune competence of these molecules has recently emerged from the D. melanogaster-Photorhabdus infection system. Here, we review the latest findings on this topic with the expectation that such information will refine our understanding of the evolutionary immune role of TEPs in host immune surveillance.