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Racca NM, Dontu A, Riley K, Yolcu ES, Shirwan H, Coronel MM. Bending the Rules: Amplifying PD-L1 Immunoregulatory Function Through Flexible Polyethylene Glycol Synthetic Linkers. Tissue Eng Part A 2024; 30:299-313. [PMID: 38318841 DOI: 10.1089/ten.tea.2023.0274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2024] Open
Abstract
Immune checkpoint signaling, such as programmed cell death protein-1 (PD-1), is a key target for immunotherapy due to its role in dampening immune responses. PD-1 signaling in T cells is regulated by complex physicochemical and mechanical cues. However, how these mechanical forces are integrated with biochemical responses remains poorly understood. Our previous work demonstrated that the use of an immobilizing polyethylene glycol (PEG) linker on synthetic microgels for the presentation of a chimeric form of PD-L1, SA-PD-L1, lead to local regulatory responses capable of abrogating allograft rejection in a model of cell-based transplantation. We herein provide evidence that enhanced immune regulating function can be obtained when presentation of SA-PD-L1 is achieved through a longer more flexible PEG chain. Presentation of SA-PD-L1 through a linker of high molecular weight, and thus longer length (10 kDa, 60 nm in length), led to enhance conversion of naive T cells into T regulatory cells (Tregs) in vitro. In addition, using a subcutaneous implant model and protein tethered through three different linker sizes (6, 30, and 60 nm) to the surface of PEG hydrogels, we demonstrated that longer linkers promoted PD-1 immunomodulatory role in vivo through three main functions: (1) augmenting immune cell recruitment at the transplant site; (2) promoting the accumulation of naive Tregs expressing migratory markers; and (3) dampening CD8+ cytolytic molecule production while augmenting expression of exhaustion phenotypes locally. Notably, accumulation of Treg cells at the implant site persisted for over 30 days postimplantation, an effect not observed when protein was presented with the shorter version of the linkers (6 and 30 nm). Collectively, these studies reveal a facile approach by which PD-L1 function can be modulated through external tuning of synthetic presenting linkers. Impact statement Recently, there has been a growing interest in immune checkpoint molecules as potential targets for tolerance induction, including programmed cell death protein-1 (PD-1). However, how the mechanics of ligand binding to PD-1 receptor affect downstream activation signaling pathways remains unresolved. By taking advantage of the effect of polyethylene glycol chain length on molecule kinetics in an aqueous solution, we herein show that PD-L1 function can be amplified by adjusting the length of the grafting linker. Our results uncover a potential facile mechanism that can be exploited to advance the role of immune checkpoint ligands, in particular PD-L1, in tolerance induction for immunosuppression-free cell-based therapies.
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Affiliation(s)
- Nicole M Racca
- Department of Biomedical Engineering and Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
- Elizabeth Caswell Diabetes Institute, University of Michigan, Ann Arbor, Michigan, USA
| | - Alexander Dontu
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Kayle Riley
- Department of Biomedical Engineering and Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
- Elizabeth Caswell Diabetes Institute, University of Michigan, Ann Arbor, Michigan, USA
| | - Esma S Yolcu
- Department of Pediatrics and University of Missouri, Columbia, Missouri, USA
- Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, Missouri, USA
| | - Haval Shirwan
- Department of Pediatrics and University of Missouri, Columbia, Missouri, USA
- Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, Missouri, USA
- Associate Director, Immunomodulation and Regenerative Medicine Program, Ellis Fischel Cancer Center, Columbia, Missouri, USA
| | - María M Coronel
- Department of Biomedical Engineering and Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
- Elizabeth Caswell Diabetes Institute, University of Michigan, Ann Arbor, Michigan, USA
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Perica K, Kosmides AK, Schneck JP. Linking form to function: Biophysical aspects of artificial antigen presenting cell design. BIOCHIMICA ET BIOPHYSICA ACTA 2015; 1853:781-90. [PMID: 25200637 PMCID: PMC4344884 DOI: 10.1016/j.bbamcr.2014.09.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 08/15/2014] [Accepted: 09/01/2014] [Indexed: 12/22/2022]
Abstract
Artificial antigen presenting cells (aAPCs) are engineered platforms for T cell activation and expansion, synthesized by coupling T cell activating proteins to the surface of cell lines or biocompatible particles. They can serve both as model systems to study the basic aspects of T cell signaling and translationally as novel approaches for either active or adoptive immunotherapy. Historically, these reductionist systems have not been designed to mimic the temporally and spatially complex interactions observed during endogenous T cell-APC contact, which include receptor organization at both micro- and nanoscales and dynamic changes in cell and membrane morphologies. Here, we review how particle size and shape, as well as heterogenous distribution of T cell activating proteins on the particle surface, are critical aspects of aAPC design. In doing so, we demonstrate how insights derived from endogenous T cell activation can be applied to optimize aAPC, and in turn how aAPC platforms can be used to better understand endogenous T cell stimulation. This article is part of a Special Issue entitled: Nanoscale membrane organisation and signalling.
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Affiliation(s)
- Karlo Perica
- Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, MD, USA; Institute of Cell Engineering, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Alyssa K Kosmides
- Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, MD, USA; Institute of Cell Engineering, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Jonathan P Schneck
- Institute of Cell Engineering, Johns Hopkins School of Medicine, Baltimore, MD, USA; Department of Pathology, Johns Hopkins School of Medicine, Baltimore, MD, USA; Department of Oncology, Johns Hopkins School of Medicine, Baltimore, MD, USA; Department of Medicine, Johns Hopkins School of Medicine, Baltimore, MD, USA.
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