Data from: Costs and benefits of sub-lethal Drosophila C virus infection

Viruses are major evolutionary drivers of insect immune systems. Much of our knowledge of insect immune responses derives from experimental infections using the fruit fly Drosophila melanogaster. Most experiments, however, employ lethal pathogen doses through septic injury, frequently overwhelming host physiology. While this approach has revealed several immune mechanisms, it is less informative about the fitness costs hosts may experience during infection in the wild. Using both systemic and oral infection routes we find that even apparently benign, sub-lethal infections with the horizontally transmitted Drosophila C Virus (DCV) can cause significant physiological and behavioral morbidity that is relevant for host fitness. We describe DCV-induced effects on fly reproductive output, digestive health, and locomotor activity, and we find that viral morbidity varies according to the concentration of pathogen inoculum, host genetic background and sex. Notably, sub-lethal DCV infection resulted in a significant increase in fly reproduction, but this effect depended on host genotype. We discuss the relevance of sub-lethal morbidity for Drosophila ecology and evolution, and more broadly, we remark on the implications of deleterious and beneficial infections for the evolution of insect immunity.

病毒是驱动昆虫免疫系统演化的核心因素。我们对昆虫免疫应答的多数认知，均源自以黑腹果蝇（Drosophila melanogaster）为实验对象的感染研究。然而绝大多数此类实验均通过针刺创伤感染（septic injury）途径施加致死剂量的病原体，往往会使宿主生理机能过载。尽管该策略已揭示了多种免疫机制，但对于宿主在自然环境中感染病原体时可能承受的适合度代价，此类实验的阐释力度相对有限。本研究采用全身感染与经口感染两种侵染途径，发现即便是由水平传播的果蝇C病毒（Drosophila C Virus, DCV）引发的看似良性的亚致死感染，也可导致与宿主适合度密切相关的显著生理与行为病态症状。本研究阐明了DCV感染对果蝇繁殖能力、消化健康以及运动活性的影响，并发现病毒引发的病态程度会随病原体接种剂量、宿主遗传背景与性别发生变化。值得注意的是，亚致死性DCV感染可显著提升果蝇的繁殖能力，但该效应完全依赖于宿主的基因型。本研究探讨了亚致死病态对于黑腹果蝇生态学与演化的相关意义，并进一步拓展讨论了有害与有益感染对昆虫免疫系统演化的启示。