Table_1_Aedes aegypti Infection With Trypanosomatid Strigomonas culicis Alters Midgut Redox Metabolism and Reduces Mosquito Reproductive Fitness.docx

Aedes aegypti mosquitoes transmit arboviruses of important global health impact, and their intestinal microbiota can influence vector competence by stimulating the innate immune system. Midgut epithelial cells also produce toxic reactive oxygen species (ROS) by dual oxidases (DUOXs) that are essential players in insect immunity. Strigomonas culicis is a monoxenous trypanosomatid that naturally inhabits mosquitoes; it hosts an endosymbiotic bacterium that completes essential biosynthetic pathways of the parasite and influences its oxidative metabolism. Our group previously showed that S. culicis hydrogen peroxide (H2O2)-resistant (WTR) strain is more infectious to A. aegypti mosquitoes than the wild-type (WT) strain. Here, we investigated the influence of both strains on the midgut oxidative environment and the effect of infection on mosquito fitness and immunity. WT stimulated the production of superoxide by mitochondrial metabolism of midgut epithelial cells after 4 days post-infection, while WTR exacerbated H2O2 production mediated by increased DUOX activity and impairment of antioxidant system. The infection with both strains also disrupted the fecundity and fertility of the females, with a greater impact on reproductive fitness of WTR-infected mosquitoes. The presence of these parasites induced specific transcriptional modulation of immune-related genes, such as attacin and defensin A during WTR infection (11.8- and 6.4-fold, respectively) and defensin C in WT infection (7.1-fold). Thus, we propose that A. aegypti oxidative response starts in early infection time and does not affect the survival of the H2O2-resistant strain, which has a more efficient antioxidant system. Our data provide new biological aspects of A. aegypti–S. culicis relationship that can be used later in alternative vector control strategies.

埃及伊蚊（Aedes aegypti）可传播对全球健康具有重要影响的虫媒病毒，其肠道菌群可通过激活先天免疫系统影响媒介传播效能。中肠上皮细胞还可通过双氧化酶（dual oxidases, DUOXs）产生活性氧（reactive oxygen species, ROS），而DUOXs是昆虫免疫的关键效应因子。库氏斯氏虫（Strigomonas culicis）是一种单宿主型动基体目锥虫体，天然寄生于蚊虫体内；其体内携带一株内共生细菌，可完成该寄生虫的核心生物合成途径并影响其氧化代谢。我们团队此前的研究表明，库氏斯氏虫过氧化氢（hydrogen peroxide, H₂O₂）抗性菌株（WTR）相较于野生型（wild-type, WT）菌株，对埃及伊蚊的感染能力更强。

本研究探究了两种菌株对蚊虫中肠氧化微环境的影响，以及感染对蚊虫适合度与免疫功能的作用。研究发现，感染后第4天，野生型菌株可通过中肠上皮细胞的线粒体代谢诱导超氧阴离子产生；而WTR菌株则通过增强DUOX活性与破坏抗氧化系统，加剧了过氧化氢的生成。此外，两种菌株的感染均会破坏雌性蚊虫的繁殖力与生育力，其中WTR感染对蚊虫繁殖适合度的影响更为显著。

这类寄生虫的感染会诱导免疫相关基因的特异性转录调控：WTR感染时，抗菌肽Attacin与防御素A的转录水平分别上调11.8倍与6.4倍；而WT感染时，防御素C的转录水平上调7.1倍。

综上，我们提出埃及伊蚊的氧化响应在感染早期即已启动，且该响应不会影响过氧化氢抗性菌株的存活——该抗性菌株拥有更为高效的抗氧化系统。本研究揭示了埃及伊蚊与库氏斯氏虫之间互作关系的全新生物学特征，可为后续开发新型媒介防控策略提供理论依据。