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伤寒沙门氏菌 Vi 荚膜多糖通过结合人 C 型凝集素 DC-SIGN 促进巨噬细胞吞噬作用。

The Vi Capsular Polysaccharide of Salmonella Typhi Promotes Macrophage Phagocytosis by Binding the Human C-Type Lectin DC-SIGN.

机构信息

Department of Medical Microbiology and Immunology, University of California at Davis, Davis, California, USA.

Institute for Immunology & Research Center for Emerging Infections and Zoonoses, University of Veterinary Medicine Hannover, Hanover, Germany.

出版信息

mBio. 2022 Dec 20;13(6):e0273322. doi: 10.1128/mbio.02733-22. Epub 2022 Oct 26.

Abstract

Capsular polysaccharides are common virulence factors of extracellular, but not intracellular bacterial pathogens, due to the antiphagocytic properties of these surface structures. It is therefore paradoxical that Salmonella enterica subspecies serovar Typhi, an intracellular pathogen, synthesizes a virulence-associated (Vi) capsule, which exhibits antiphagocytic properties. Here, we show that the Vi capsular polysaccharide has different functions when S. Typhi interacts with distinct subsets of host phagocytes. The Vi capsular polysaccharide allowed S. Typhi to selectively evade phagocytosis by human neutrophils while promoting human macrophage phagocytosis. A screen of C-type lectin receptors identified human DC-SIGN as the receptor involved in macrophage binding and phagocytosis of capsulated S. Typhi. Consistent with the anti-inflammatory activity of DC-SIGN, purified Vi capsular polysaccharide reduced inflammatory responses in macrophages. These data suggest that binding of the human C-type lectin receptor DC-SIGN by the Vi capsular polysaccharide contributes to the pathogenesis of typhoid fever. Salmonella enterica subspecies serovar Typhi is the causative agent of typhoid fever. The recent emergence of S. Typhi strains which are resistant to antibiotic therapy highlights the importance of vaccination in managing typhoid fever. The virulence-associated (Vi) capsular polysaccharide is an effective vaccine against typhoid fever, but the role the capsule plays during pathogenesis remains incompletely understood. Here, we identify the human C-type lectin receptor DC-SIGN as the receptor for the Vi capsular polysaccharide. Binding of capsulated S. Typhi to DC-SIGN resulted in phagocytosis of the pathogen by macrophages and induction of an anti-inflammatory cytokine response. Thus, the interaction of the Vi capsular polysaccharide with human DC-SIGN contributes to the pathogenesis of typhoid fever and should be further investigated in the context of vaccine development.

摘要

荚膜多糖是细胞外,但不是细胞内细菌病原体的常见毒力因子,这是由于这些表面结构具有抗吞噬作用。因此,具有讽刺意味的是,细胞内病原体沙门氏菌亚种血清型 Typhi 合成了一种与毒力相关的(Vi)荚膜,该荚膜具有抗吞噬作用。在这里,我们表明,当 S. Typhi 与宿主吞噬细胞的不同亚群相互作用时,Vi 荚膜多糖具有不同的功能。Vi 荚膜多糖使 S. Typhi 能够选择性逃避人中性粒细胞的吞噬作用,同时促进人巨噬细胞的吞噬作用。C 型凝集素受体的筛选鉴定了人类 DC-SIGN 作为涉及包裹 S. Typhi 的巨噬细胞结合和吞噬的受体。与 DC-SIGN 的抗炎活性一致,纯化的 Vi 荚膜多糖降低了巨噬细胞中的炎症反应。这些数据表明,Vi 荚膜多糖与人 C 型凝集素受体 DC-SIGN 的结合有助于伤寒的发病机制。沙门氏菌亚种血清型 Typhi 是伤寒的病原体。最近出现的对抗生素治疗具有抗性的 S. Typhi 菌株突显了疫苗接种在管理伤寒中的重要性。与毒力相关的(Vi)荚膜多糖是伤寒的有效疫苗,但荚膜在发病机制中的作用仍不完全清楚。在这里,我们确定了人类 C 型凝集素受体 DC-SIGN 作为 Vi 荚膜多糖的受体。包裹的 S. Typhi 与 DC-SIGN 的结合导致病原体被巨噬细胞吞噬,并诱导抗炎细胞因子反应。因此,Vi 荚膜多糖与人类 DC-SIGN 的相互作用有助于伤寒的发病机制,并且应该在疫苗开发的背景下进一步研究。

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