Institut Pasteur, Dynamics of Host-Pathogen Interactions Unit, Paris, France, and Centre National de le la Recherche Scientifique (CNRS) UMR3691, Paris, France.
Institut Pasteur, Transcriptome and Epigenome Platform, Paris, France.
PLoS Pathog. 2020 Apr 13;16(4):e1008446. doi: 10.1371/journal.ppat.1008446. eCollection 2020 Apr.
Microfold (M) cell host-pathogen interaction studies would benefit from the visual analysis of dynamic cellular and microbial interplays. We adapted a human in vitro M cell model to physiological bacterial infections, expression of fluorescent localization reporters and long-term three-dimensional time-lapse microscopy. This approach allows following key steps of M cell infection dynamics at subcellular resolution, from the apical onset to basolateral epithelial dissemination. We focused on the intracellular pathogen Shigella flexneri, classically reported to transcytose through M cells to initiate bacillary dysentery in humans, while eliciting poorly protective immune responses. Our workflow was critical to reveal that S. flexneri develops a bimodal lifestyle within M cells leading to rapid transcytosis or delayed vacuolar rupture, followed by direct actin motility-based propagation to neighboring enterocytes. Moreover, we show that Listeria monocytogenes, another intracellular pathogen sharing a tropism for M cells, disseminates in a similar manner and evades M cell transcytosis completely. We established that actin-based M cell-to-enterocyte spread is the major dissemination pathway for both pathogens and avoids their exposure to basolateral compartments in our system. Our results challenge the notion that intracellular pathogens are readily transcytosed by M cells to inductive immune compartments in vivo, providing a potential mechanism for their ability to evade adaptive immunity.
微皱褶（M）细胞与病原体的相互作用研究将受益于对动态细胞和微生物相互作用的可视化分析。我们将人类体外 M 细胞模型适应于生理细菌感染、荧光定位报告基因的表达和长期的三维延时显微镜检查。这种方法允许以亚细胞分辨率跟踪 M 细胞感染动力学的关键步骤，从顶端开始到基底外侧上皮细胞的传播。我们专注于细胞内病原体福氏志贺菌，经典报道称其通过 M 细胞易位，在人类中引发细菌性痢疾，同时引发保护作用差的免疫反应。我们的工作流程对于揭示福氏志贺菌在 M 细胞内形成双模态生活方式至关重要，导致快速易位或延迟空泡破裂，随后直接通过肌动蛋白运动进行传播到邻近的肠上皮细胞。此外，我们表明，李斯特菌属单核细胞增生李斯特菌，另一种具有 M 细胞趋向性的细胞内病原体，以类似的方式传播，并完全逃避 M 细胞易位。我们确定了基于肌动蛋白的 M 细胞到肠上皮细胞的传播是两种病原体的主要传播途径，并在我们的系统中避免了它们暴露于基底外侧隔室。我们的结果挑战了细胞内病原体易位通过 M 细胞到体内诱导性免疫隔室的观点，为它们逃避适应性免疫的能力提供了潜在的机制。
