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Exploring the role of E. faecalis enterococcal polysaccharide antigen (EPA) and lipoproteins in evasion of phagocytosis
Molecular Microbiology ( IF 2.6 ) Pub Date : 2024-07-12 , DOI: 10.1111/mmi.15294
Joshua S Norwood 1 , Jessica L Davis 1 , Bartłomiej Salamaga 1 , Charlotte E Moss 2 , Simon A Johnston 2 , Philip M Elks 2 , Endre Kiss-Toth 2 , Stéphane Mesnage 1
Affiliation  

Enterococcus faecalis is an opportunistic pathogen frequently causing nosocomial infections. The virulence of this organism is underpinned by its capacity to evade phagocytosis, allowing dissemination in the host. Immune evasion requires a surface polysaccharide produced by all enterococci, known as the enterococcal polysaccharide antigen (EPA). EPA consists of a cell wall-anchored rhamnose backbone substituted by strain-specific polysaccharides called ‘decorations’, essential for the biological activity of this polymer. However, the structural determinants required for innate immune evasion remain unknown, partly due to a lack of suitable validated assays. Here, we describe a quantitative, in vitro assay to investigate how EPA decorations alter phagocytosis. Using the E. faecalis model strain OG1RF, we demonstrate that a mutant with a deletion of the locus encoding EPA decorations can be used as a platform strain to express heterologous decorations, thereby providing an experimental system to investigate the inhibition of phagocytosis by strain-specific decorations. We show that the aggregation of cells lacking decorations is increasing phagocytosis and that this process does not involve the recognition of lipoproteins by macrophages. Collectively, our work provides novel insights into innate immune evasion by enterococci and paves the way for further studies to explore the structure/function relationship of EPA decorations.

中文翻译:


探索粪肠球菌肠球菌多糖抗原(EPA)和脂蛋白在逃避吞噬作用中的作用



粪肠球菌是一种机会性病原体,经常引起医院感染。这种生物体的毒力源于其逃避吞噬作用的能力,从而能够在宿主中传播。免疫逃避需要所有肠球菌产生的表面多糖,称为肠球菌多糖抗原(EPA)。 EPA 由细胞壁锚定的鼠李糖骨架组成,该骨架被菌株特异性多糖(称为“装饰”)取代,这对于这种聚合物的生物活性至关重要。然而,先天免疫逃避所需的结构决定因素仍然未知,部分原因是缺乏合适的经过验证的检测方法。在这里,我们描述了一种定量的体外测定,以研究 EPA 修饰如何改变吞噬作用。使用E 。在粪肠球菌模型菌株 OG1RF 中,我们证明编码 EPA 装饰基因座缺失的突变体可以用作表达异源装饰的平台菌株,从而提供了一个实验系统来研究菌株特异性装饰对吞噬作用的抑制。我们发现,缺乏装饰的细胞聚集会增加吞噬作用,并且该过程不涉及巨噬细胞对脂蛋白的识别。总的来说,我们的工作为肠球菌的先天免疫逃避提供了新的见解,并为进一步研究探索 EPA 修饰的结构/功能关系铺平了道路。
更新日期:2024-07-12
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