Department of Molecular Cell Biology and Immunology, Amsterdam UMC, Location VUmc, Amsterdam, The Netherlands.
Abera Bioscience AB, Stockholm, Sweden.
Acta Biomater. 2019 Jun;91:248-257. doi: 10.1016/j.actbio.2019.04.033. Epub 2019 Apr 17.
Outer membrane vesicles (OMVs) are vesicular nano-particles produced by Gram-negative bacteria that are recently being explored as vaccine vector. The fact that OMVs can be efficiently produced by a hypervesiculating Salmonella typhimurium strain, are packed with naturally-occurring adjuvants like lipopolysaccharides (LPS), and can be engineered to express any antigen of choice, makes them ideal candidates for vaccinology. However, it is unclear whether OMVs induce dendritic cell (DC)-mediated antigen-specific T cell responses and how immune activation is coordinated. Here, we show that OMVs induce maturation of human monocyte-derived DCs, murine bone marrow-derived DCs and CD11c+ splenic DCs. OMV-induced DC maturation was dependent on the presence of LPS and the myeloid differentiation primary response 88 (MyD88) adapter protein downstream of toll-like receptor signaling. Importantly, OMVs did not induce pyroptosis/cell death, but instead provided a significant survival benefit in DCs over non-stimulated DCs. OMVs displaying a sizeable ovalbumin fragment at the vesicle surface induce potent cross-presentation in BMDCs and splenic CD11c DCs to OTI CD8 T cells, dependent on MyD88. Interestingly, the OMV-induced preference to cross-presentation was only partly dependent on the BATF3-dependent CD8a professional cross-presenting DC subset. Hence, an OMV-specific programming of DCs that induces maturation and provides a survival benefit for antigen presentation to T cells is identified. Additionally, for the first time, antigen-specific and potent cross-presentation of antigen-loaded OMVs to CD8 T cells is demonstrated. These data provide mechanistical insight into the processes needed for the DC-mediated cross-presentation of OMV-derived antigens to CD8 T cells with implications for therapeutic strategies. STATEMENT OF SIGNIFICANCE: Bacteria are primarily known to cause disease. However, recent research has focused on using engineered bacteria and its byproducts as vaccine agents. In particular, outer membrane vesicles (OMVs) have shown promise in eliciting potent immunity against a variety of pathogens. While most vaccines rely on the generation of antibodies, the control of viral replication and tumor growth is driven by cytotoxic CD8 T cells induced by dendritic cells (DCs). As such, there is a dire need for vaccines that use DCs to elicit CD8 T cell responses. Studying OMVs as engineered biomaterial and its interaction with DCs allows tailored induction of immunity. This study includes important findings on OMV-dendritic cell interactions and for the first time supports OMVs as vehicles for the induction of antigen-specific CD8 T cell responses. Additionally, important mechanistical insight into the molecular pathways needed for the cross-presentation of OMV-derived antigens to CD8 T cells is provided.
外膜囊泡 (OMVs) 是革兰氏阴性细菌产生的囊泡纳米颗粒,最近被探索作为疫苗载体。事实上,超囊泡化的鼠伤寒沙门氏菌菌株可以有效地产生 OMVs,并且充满了天然佐剂,如脂多糖 (LPS),并且可以被设计来表达任何所需的抗原,这使得它们成为疫苗学的理想候选物。然而,目前尚不清楚 OMVs 是否诱导树突状细胞 (DC) 介导的抗原特异性 T 细胞反应,以及免疫激活如何协调。在这里,我们表明 OMVs 诱导人单核细胞衍生的 DC、鼠骨髓衍生的 DC 和 CD11c+脾 DC 的成熟。OMV 诱导的 DC 成熟依赖于 LPS 的存在和 Toll 样受体信号下游的髓样分化初级反应 88 (MyD88) 衔接蛋白。重要的是,OMVs 不会诱导细胞焦亡/细胞死亡,而是在未刺激的 DC 中为 DC 提供显著的生存优势。在囊泡表面显示出大量卵清蛋白片段的 OMVs 诱导 BMDC 和脾 CD11c DC 中 OTI CD8 T 细胞的有效交叉呈递,依赖于 MyD88。有趣的是,OMV 诱导的交叉呈递偏好仅部分依赖于 BATF3 依赖性 CD8a 专业交叉呈递 DC 亚群。因此,鉴定了一种诱导 DC 成熟并为 T 细胞提供抗原呈递生存优势的 OMV 特异性编程。此外,首次证明了负载抗原的 OMV 对 CD8 T 细胞的抗原特异性和有效交叉呈递。这些数据为 DC 介导的 OMV 衍生抗原向 CD8 T 细胞的交叉呈递所需的过程提供了机制见解,并为治疗策略提供了启示。意义声明:细菌主要被认为会引起疾病。然而,最近的研究集中在使用工程细菌及其副产物作为疫苗剂。特别是,外膜囊泡 (OMVs) 在引发针对多种病原体的强烈免疫方面显示出了希望。虽然大多数疫苗依赖于抗体的产生,但病毒复制和肿瘤生长的控制是由树突状细胞 (DC) 诱导的细胞毒性 CD8 T 细胞驱动的。因此,迫切需要使用 DC 引发 CD8 T 细胞反应的疫苗。研究 OMV 作为工程生物材料及其与 DC 的相互作用可以实现对免疫的精确诱导。这项研究包括关于 OMV-树突状细胞相互作用的重要发现,并首次支持 OMVs 作为诱导抗原特异性 CD8 T 细胞反应的载体。此外,还提供了关于 OMV 衍生抗原向 CD8 T 细胞交叉呈递所需的分子途径的重要机制见解。
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