Experimental Fish Models (ExFiMo), Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, Denmark.
Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Frederiksberg, Denmark.
Front Cell Infect Microbiol. 2023 Jul 5;13:1190931. doi: 10.3389/fcimb.2023.1190931. eCollection 2023.
The protozoan parasite is an economically important parasite for the aquaculture- and ornamental fish industry. The parasite is abundant worldwide and infects the skin, gills and fins of freshwater fish species. For approximately the last fifty years the innate and protective immune mechanisms induced by have been in focus in different fish hosts. By utilizing transgenic zebrafish, new tools to investigate this have emerged. The aim of this study was therefore to elucidate early immune responses in zebrafish larvae by using gene expression and imaging of neutrophil and macrophage behavior during infection. For the first time, zebrafish larvae were infected with the parasite and infection dynamics, parasite size and host-parasite interactions were investigated. Results showed that the larvae responded with mild inflammation and that the 12 compared to 5 days post fertilization larvae were significantly less susceptible. It was furthermore observed that neutrophils and macrophages were attracted to the parasites and that neutrophils reacted with neutrophil extracellular traps (NETs) when fighting the parasite. The parasite was rotating vigorously, presumably to impede the neutrophils and macrophages from attaching to it but on rare occasions, neutrophils and macrophages were able to kill the parasite. Based on these observations, we concluded that the parasite uses the rotation as an immune evasive strategy and that the zebrafish larvae respond with high activity from neutrophils and macrophages locally but systemically only with mild inflammation.
原生动物寄生虫是水产养殖和观赏鱼产业中一种具有重要经济意义的寄生虫。该寄生虫在全球范围内广泛存在，感染淡水鱼类的皮肤、鳃和鳍。大约在过去五十年间，不同鱼类宿主中由 引起的固有和保护性免疫机制一直是研究的重点。利用转基因斑马鱼，出现了新的研究工具。因此，本研究旨在通过研究中性粒细胞和巨噬细胞行为的基因表达和 成像，阐明斑马鱼幼虫的早期免疫反应。这是首次感染该寄生虫并研究感染动力学、寄生虫大小和宿主-寄生虫相互作用。结果表明，幼虫会出现轻度炎症，且与受精后 5 天相比，12 天幼虫的敏感性显著降低。此外，观察到中性粒细胞和巨噬细胞被寄生虫吸引，并且当与寄生虫作斗争时，中性粒细胞会产生中性粒细胞胞外诱捕网（NETs）。寄生虫剧烈旋转，可能是为了阻止中性粒细胞和巨噬细胞附着在它身上，但偶尔也会有中性粒细胞和巨噬细胞能够杀死寄生虫。基于这些观察，我们得出结论，寄生虫利用旋转作为一种免疫逃避策略，而斑马鱼幼虫局部会产生强烈的中性粒细胞和巨噬细胞反应，但全身仅出现轻度炎症。
