Type VI Secretion System and Its Effectors PdpC, PdpD, and OpiA Contribute to Francisella Virulence in Galleria mellonella Larvae.
Type VI Secretion System and Its Effectors PdpC, PdpD, and OpiA Contribute to Francisella Virulence in Galleria mellonella Larvae.
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DOI：
10.1128/iai.00579-20
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发表时间：
2021-06-16
影响因子：
3.1
通讯作者：
Basler M
中科院分区：
文献类型：
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作者：
Brodmann M;Schnider ST;Basler M
土拉弗朗西斯菌引起人类致命的人畜共患兔热病，并且能够感染包括节肢动物在内的多种生物体，节肢动物被认为在弗朗西斯菌传播中发挥着重要作用。然而，虽然哺乳动物体外和体内感染模型被广泛用于研究弗朗西斯菌致病性，但节肢动物体内感染模型中主要弗朗西斯菌毒力因子（非典型 VI 型分泌系统（T6SS））的详细表征却缺失。在这里，我们利用大蜡螟幼虫来分析弗朗西斯菌 T6SS 及其相应效应子在土拉弗朗西斯亚种中的作用。新凶手的毒力。我们报告大蜡螟幼虫的杀灭取决于功能性 T6SS 和感染剂量。与其他哺乳动物体内感染模型相比，即使 T6SS 效应子 PdpC、PdpD 或 OpiA 之一也足以杀死大蜡螟幼虫，而 ClpB 的鞘回收是可有可无的。我们进一步证明，聚乙二醇 (PEG) 处理可激活液体培养物中的弗朗西斯菌 T6SS，并且这与反应调节剂 PmrA 无关。 PEG 激活的 IglC 分泌依赖于 T6SS 结构成分 PdpB，但独立于假定的效应子 PdpC、PdpD、AnmK、OpiB1、OpiB2 和 OpiB3。幼虫感染和分泌测定的结果表明，AnmK（一种功能未知的假定 T6SS 成分）会干扰 OpiA 介导的毒性，但不会干扰一般 T6SS 活性。我们建立了易于使用的大蜡螟幼虫感染模型，为了解 T6SS 的功能和弗朗西斯氏菌的发病机制提供了新的见解。
Francisella tularensis causes the deadly zoonotic disease tularemia in humans and is able to infect a broad range of organisms including arthropods, which are thought to play a major role in Francisella transmission. However, while mammalian in vitro and in vivo infection models are widely used to investigate Francisella pathogenicity, a detailed characterization of the major Francisella virulence factor, a noncanonical type VI secretion system (T6SS), in an arthropod in vivo infection model is missing. Here, we use Galleria mellonella larvae to analyze the role of the Francisella T6SS and its corresponding effectors in F. tularensis subsp. novicida virulence. We report that G. mellonella larvae killing depends on the functional T6SS and infectious dose. In contrast to other mammalian in vivo infection models, even one of the T6SS effectors PdpC, PdpD, or OpiA is sufficient to kill G. mellonella larvae, while sheath recycling by ClpB is dispensable. We further demonstrate that treatment by polyethylene glycol (PEG) activates Francisella T6SS in liquid culture and that this is independent of the response regulator PmrA. PEG-activated IglC secretion is dependent on T6SS structural component PdpB but independent of putative effectors PdpC, PdpD, AnmK, OpiB1, OpiB2, and OpiB3. The results of larvae infection and secretion assay suggest that AnmK, a putative T6SS component with unknown function, interferes with OpiA-mediated toxicity but not with general T6SS activity. We establish that the easy-to-use G. mellonella larvae infection model provides new insights into the function of T6SS and pathogenesis of Francisella.