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.
项目摘要 立克次体是节肢动物传播的专性胞内细菌, 生命周期立克次体感染的全球影响突出表现在人类感染立克次体的重新抬头。 立克次氏体(Rocky Mountain Spotted Fever)在中南美洲的重新出现; 欧洲、中东和非洲9的康氏杆菌(布顿热的病原体)和最近爆发的 R. rickettsii和R.伤寒(鼠伤寒的病原体)在美国。不幸的是,我们的不足 了解立克次体与宿主的相互作用,特别是在立克次体通过受体-配体- 介导的吞噬功能对宿主防御细胞,如巨噬细胞(MΦ),已显着受损, 开发针对这些病原体的有效疗法。为了弥补这些知识差距,我们 建议:i)表征参与免疫应答的特异性立克次体外膜甘油磷脂配体, MΦ对SFG和TG立克次体的吞噬过程,ii)解读巨噬细胞受体CD 300 f在M Φ吞噬SFG和TG立克次体中的作用, 促进有毒立克次体物种的宿主定殖。我们的初步工作确定了磷脂酰丝氨酸 (PS),一种特征明确的“eat-me”信号,参与凋亡细胞的吞噬作用(又名吞噬作用), 立克次体外膜上的一种假定配体。我们进一步验证了PS作为吞噬的关键配体, R. typhi和R.立克次氏体[Shelia Smith],分别代表TG和SFG的两种毒性细菌,通过使用 重组膜联蛋白V,一种已知可阻断PS介导的巨噬细胞增多的分子,在骨髓源性 巨噬细胞(BMMΦ)。由于PS依赖的吞噬作用需要PS受体识别,我们将重点放在 CD 300 f是一种I型跨膜细胞表面受体,对PS具有高结合亲和力。使用WT和CD 300 f- /- BMMΦ的吞噬作用。typhi和R.立克次体依赖于CD 300 f的表达, 通过α CD 300 f抗体介导的WT BMMΦ中和试验进一步证实。我们测试了 CD 300 f在小鼠体内的LD_(50),通过建立立克次体病小鼠模型,typhi和R.立克次体 在C57 BL/6 J WT小鼠中,CD 300 f-/-动物被保护免于 立克次体引起的致死性此外,通过氯膦酸盐-脂质体体内消耗MΦ表明, MΦ上的CD 300 f表达有助于对立克次体诱导的致死性的保护。因此,我们将测试 假设SFG和TG立克次体都利用巨噬细胞信号传导侵入MΦ,使用以下 目的:鉴定立克次体外膜甘油磷脂[磷脂酰丝氨酸(PS)或其他]配体 参与MΦ对致病性立克次体的吞噬和定殖(目的1),并定义了 甘油磷脂结合受体CD 300 f在促进宿主吞噬和定植中的作用 MΦ致病性立克次体(Aim 2)。在这个“探索/发展研究资助计划”下,我们将 研究来自SFG和TG的立克次氏体利用正常单核细胞CD 300 f配体的机制 系统成功地定殖宿主。总之,这笔赠款的目的是揭示机制, 立克次体入侵的目标,以确定更熟练的抗毒力治疗的目标。

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:
    10674996
  • 财政年份:
    2022
  • 资助金额:
    $ 23.18万
  • 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:
    $ 23.18万
  • 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:
    $ 23.18万
  • 项目类别:
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