Institut Pasteur, Université Paris Cité, Université Paris Cité, Biologie des Bactéries Intracellulaires and CNRS UMR 6047, Paris, France.
Institut Pasteur, Université Paris Cité, Unité Macrophages et Développement de l'Immunité and CNRS UMR 3738, Paris, France.
PLoS Pathog. 2023 May 8;19(5):e1011375. doi: 10.1371/journal.ppat.1011375. eCollection 2023 May.
The zebrafish has become a powerful model organism to study host-pathogen interactions. Here, we developed a zebrafish model to dissect the innate immune response to Legionella pneumophila during infection. We show that L. pneumophila cause zebrafish larvae death in a dose dependent manner. Additionally, we show that macrophages are the first line of defence and cooperate with neutrophils to clear the infection. Immunocompromised humans have an increased propensity to develop pneumonia, similarly, when either macrophages or neutrophils are depleted, these "immunocompromised" larvae become lethally sensitive to L. pneumophila. Also, as observed in human infections, the adaptor signalling molecule Myd88 is not required to control disease in the larvae. Furthermore, proinflammatory cytokine genes il1β and tnf-α were upregulated during infection, recapitulating key immune responses seen in human infection. Strikingly, we uncovered a previously undescribed infection phenotype in zebrafish larvae, whereby bloodborne, wild type L. pneumophila invade and grow in the larval yolk region, a phenotype not observed with a type IV secretion system deficient mutant that cannot translocate effectors into its host cell. Thus, zebrafish larva represents an innovative L. pneumophila infection model that mimics important aspects of the human immune response to L. pneumophila infection and will allow the elucidation of mechanisms by which type IV secretion effectors allow L. pneumophila to cross host cell membranes and obtain nutrients from nutrient rich environments.
斑马鱼已成为研究宿主-病原体相互作用的强大模式生物。在这里,我们开发了一种斑马鱼模型来剖析感染期间肺炎嗜肺军团菌的先天免疫反应。我们表明,肺炎嗜肺军团菌以剂量依赖的方式导致斑马鱼幼虫死亡。此外,我们表明巨噬细胞是第一道防线,并与中性粒细胞合作清除感染。免疫功能低下的人更容易发生肺炎,同样,当巨噬细胞或中性粒细胞被耗尽时,这些“免疫功能低下”的幼虫对肺炎嗜肺军团菌变得致命敏感。此外,正如在人类感染中观察到的那样,衔接信号分子 Myd88 对于控制幼虫中的疾病并不是必需的。此外,在感染期间,促炎细胞因子基因 il1β 和 tnf-α 被上调,重现了人类感染中观察到的关键免疫反应。引人注目的是,我们在斑马鱼幼虫中发现了一个以前未描述的感染表型,即血源性、野生型肺炎嗜肺军团菌侵入并在幼虫卵黄区生长,而无法将效应蛋白易位到其宿主细胞中的 IV 型分泌系统缺陷突变体则没有观察到这种表型。因此,斑马鱼幼虫代表了一种创新的肺炎嗜肺军团菌感染模型,它模拟了人类对肺炎嗜肺军团菌感染的免疫反应的重要方面,并将允许阐明 IV 型分泌效应子如何使肺炎嗜肺军团菌穿过宿主细胞膜并从富含营养的环境中获取营养。