Virulent Rickettsia species utilize the CD300f phosphatidylserine-binding receptor on macrophages for host colonization and pathogenesis

强毒立克次体利用巨噬细胞上的 CD300f 磷脂酰丝氨酸结合受体进行宿主定植和发病机制

基本信息

项目摘要

PROJECT SUMMARY Rickettsia species are arthropod-borne obligate intracellular bacteria with both symbiotic and pathogenic lifecycles. The global impact of rickettsial infections is highlighted by the resurgence of human infections with R. rickettsii (etiologic agent of Rocky Mountain Spotted Fever) in Central and South America, reappearance of R. conorii (etiologic agent of Boutonneuse Fever) in Europe, Middle East, and Africa9 and the recent outbreaks of R. rickettsii and R. typhi (etiologic agent of murine typhus) in the USA. Unfortunately, our inadequate understanding of Rickettsia-host interaction, in particular at the level on rickettsial engulfment via receptor-ligand- mediated phagocytosis on professional host defense cells, like macrophages (MΦ), has significantly impaired the development of effective therapeutics against these pathogens. To address these knowledge gaps, we propose to: i) characterize the specific rickettsial outer membrane glycerophospholipid ligand(s) involved in the phagocytic process of SFG and TG rickettsiae by MΦ, ii) decipher the role of efferocytic receptor, CD300f, in facilitating host colonization of virulent Rickettsia species. Our preliminary work identified phosphatidylserine (PS), a well-characterized “eat-me” signal involved in the phagocytosis of apoptotic cells (aka efferocytosis), as a putative ligand on outer membrane of rickettsiae. We further validated PS as crucial ligand for engulfment of R. typhi and R. rickettsii [Shelia Smith], two virulent bacteria representing the TG and SFG, respectively, by using recombinant Annexin V, a molecule known to block PS-mediated efferocytosis, in bone marrow-derived macrophages (BMMΦ). As PS-dependent phagocytosis requires PS-receptor recognition, we focused on CD300f, a type I transmembrane cell surface receptors with a high binding affinity to PS. Using WT and CD300f- /- BMMΦ, we showed that engulfment of R. typhi and R. rickettsii was dependent on CD300f expression, which was further confirmed by αCD300f antibody-mediated neutralization assays on WT BMMΦ. We tested the role of CD300f in vivo, by establishing mouse models of rickettsiosis with ~LD50 for both R. typhi and R. rickettsii species in C57BL/6J WT mice and showed that, unlike WT mice, CD300f-/- animals were protected against Rickettsia-induced lethality. Furthermore, in vivo depletion of MΦ, via clodronate-liposomes, suggest that CD300f-expression on MΦ contributed to the protection against Rickettsia-induced lethality. Hence, we will test the hypothesis, that both SFG and TGs Rickettsia exploit efferocytic signaling to invade MΦ, using the following Aims: to identify rickettsial outer membrane glycerophospholipid [phosphatidylserine (PS) or other] ligand(s) involved in the engulfment and colonization of pathogenic Rickettsia by MΦ (Aim 1) and define the contributing role of glycerophospholipid-binding receptor, CD300f, in promoting engulfment and colonization of the host by pathogenic Rickettsia in MΦ (Aim 2). Under this “Exploratory/Developmental Research Grant Program” we will study the mechanisms by which rickettsiae from both SFG and TG exploit the normally efferocytic CD300f-ligand systems on MΦ to successfully colonize the host. In sum, the purpose of this grant is to unveil mechanisms of rickettsial invasion with the goal to identify more proficient targets for anti-virulence therapy.
项目总结 立克次体是节肢动物传播的专性胞内细菌,既有共生又有致病 生命周期。立克次体感染的全球影响因人类感染R. 立克次体(落基山斑点热病原)在中南美洲重现。 铜绿假单胞菌(Boutonneuse Fever)在欧洲、中东和非洲的病原体9以及最近爆发的 美国的立克次体和伤寒杆菌(小鼠斑疹伤寒的病原体)。不幸的是,我们的不足 理解立克次体与宿主的相互作用,特别是通过受体-配体-受体吞噬立克次体的水平- 介导的对专业宿主防御细胞的吞噬作用,如巨噬细胞(MΦ),已显著受损 针对这些病原体的有效治疗方法的发展。为了解决这些知识差距,我们 建议:i)鉴定立克次体外膜甘油磷脂配体(S) MΦ吞噬SFG和TG立克次体的过程,II)破译泡泡细胞受体CD300f在 促进强毒立克次体的寄主定植。我们的初步工作确定了磷脂酰丝氨酸 (PS),一个特征明确的“Eat-Me”信号,参与了凋亡细胞的吞噬作用(又名泡泡吞噬作用),AS 立克次体外膜上的一种可能的配体。我们进一步验证了PS是吞噬的关键配体 伤寒杆菌和立克次杆菌[Shelia Smith],分别代表TG和SFG,通过使用 骨髓来源的重组Annexin V,一种已知能阻断PS介导的胞吐作用的分子 巨噬细胞(Φ)。由于PS依赖的吞噬作用需要PS受体的识别,我们将重点放在 CD300f是一种与PS具有高亲和力的I型跨膜细胞表面受体。使用WT和CD300f- /-bmmΦ,我们发现伤寒杆菌和立克次杆菌的吞噬依赖于CD300f的表达,CD300f的表达 经αCD300f抗体介导的WT BMMΦ中和试验进一步证实。我们测试了这个角色 通过建立伤寒杆菌和立克次体~(50)LD_(50)小鼠立克次体动物模型,体内应用CD300f。 与WT小鼠不同的是,CD300f-/-动物受到保护 立克次体致死。此外,通过氯膦酸脂质体体内耗尽MΦ表明 M-Φ上CD300f的表达有助于对抗立克次体诱导的致死性。因此,我们将测试 假设SFG和TGS立克次体都利用泡细胞信号入侵MΦ,使用以下方法 目的:鉴定立克次体外膜甘油磷脂[磷脂酰丝氨酸等]配体(S) 参与MΦ对致病性立克次体的吞噬和定植(目标1),并确定其贡献 甘油磷脂结合受体CD300f在促进宿主吞噬和定植中的作用 MΦ致病性立克次体(目标2)。在这项“探索/发展研究资助计划”下,我们将 研究SFG和TG立克次体利用正常吞噬细胞CD300f-配体的机制 MΦ上的系统才能成功定植该主机。总而言之,这笔赠款的目的是揭示 立克次体侵袭,目的是确定更熟练的抗毒力治疗靶点。

项目成果

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Mohammed Sayeedur Rahman其他文献

Mohammed Sayeedur Rahman的其他文献

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{{ truncateString('Mohammed Sayeedur Rahman', 18)}}的其他基金

Virulent Rickettsia species utilize the CD300f phosphatidylserine-binding receptor on macrophages for host colonization and pathogenesis
强毒立克次体利用巨噬细胞上的 CD300f 磷脂酰丝氨酸结合受体进行宿主定植和发病机制
  • 批准号:
    10526450
  • 财政年份:
    2022
  • 资助金额:
    $ 19.31万
  • 项目类别:
Rickettsia-host interface and multiple paths to invasion
立克次体-宿主界面和多种入侵途径
  • 批准号:
    10626741
  • 财政年份:
    2016
  • 资助金额:
    $ 19.31万
  • 项目类别:
Murine Typhus
鼠型斑疹伤寒
  • 批准号:
    10404649
  • 财政年份:
    1982
  • 资助金额:
    $ 19.31万
  • 项目类别:
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