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* These authors contributed equally
Here, we present a protocol to quickly and reproducibly generate biologically inspired, biodegradable articifical antigen presenting cells (aAPC) with tunable size, shape, and surface protein presentation for T cell expansion ex vivo or in vivo.
Artificial antigen presenting cells (aAPC) are a promising platform for immune modulation due to their potent ability to stimulate T cells. Acellular substrates offer key advantages over cell-based aAPC, including precise control of signal presentation parameters and physical properties of the aAPC surface to modulate its interactions with T cells. aAPC constructed from anisotropic particles, particularly ellipsoidal particles, have been shown to be more effective than their spherical counterparts at stimulating T cells due to increased binding and larger surface area available for T cell contact, as well as reduced nonspecific uptake and enhanced pharmacokinetic properties. Despite increased interest in anisotropic particles, even widely accepted methods of generating anisotropic particles such as thin-film stretching can be challenging to implement and use reproducibly.
To this end, we describe a protocol for the rapid, standardized fabrication of biodegradable anisotropic particle-based aAPC with tunable size, shape, and signal presentation for T cell expansion ex vivo or in vivo, along with methods to characterize their size, morphology, and surface protein content, and to assess their functionality. This approach to fabricating anisotropic aAPC is scalable and reproducible, making it ideal for generating aAPC for "off-the-shelf" immunotherapies.
Artificial antigen presenting cells (aAPC) have shown promise as immunomodulatory agents because they can generate a robust antigen-specific T cell response. Essential to these platforms are their ability to efficiently present crucial signals for T cell activation. Acellular aAPC are an attractive alternative to cell-based aAPC because they are easier and less costly to fabricate, face fewer challenges during scale-up and translation, and alleviate risks associated with cell-based therapies. Acellular aAPC also allow for a high degree of control over signal presentation parameters and physical properties of the surface that will interface with T cells1.
aAPC must recapitulate a minimum of two signals essential for T cell activation. Signal 1 provides antigen recognition and occurs when the T cell receptor (TCR) recognizes and engages with an MHC class I or II bearing its cognate antigen, culminating in signaling through the TCR complex. To bypass the antigen specificity requirement, aAPC systems often bear an agonistic monoclonal antibody against the CD3 receptor, which nonspecifically stimulates the TCR complex. Recombinant forms of MHC, particularly MHC multimers, have also been used on the surface of aAPC to provide antigen specificity2,3. Signal 2 is a costimulatory signal that directs T cell activity. To provide the costimulation necessary for T cell activation, the CD28 receptor is generally stimulated with an agonistic antibody presented on the aAPC surface, although other costimulatory receptors such as 4-1BB have been successfully targeted4. Signal 1 and 2 proteins are typically immobilized on the surface of rigid particles to synthesize aAPC. Historically, aAPC have been fabricated from a variety of materials, including polystyrene4,5 and iron dextran6. Newer systems utilize biodegradable polymers like poly(lactic-co-glycolic acid) (PLGA) to generate aAPC that can be easily coupled to signal proteins, are suitable for direct administration in vivo, and can facilitate the sustained release of encapsulated cytokines or soluble factors to augment T cell activation7,8.
In addition to the presence of necessary signal proteins, receptor engagement over a sufficiently large surface area during the aAPC/T cell interaction is essential for T cell activation. Thus, physical parameters of the aAPC such as size and shape drastically alter their available contact area and affect their ability to stimulate T cells. Micron-sized aAPC have been shown to be more effective at stimulating T cells than their nanoscale counterparts9,10. However, nano-aAPC can have superior biodistribution and better drainage to the lymph nodes that may enhance their performance in vivo over micro-aAPC11. Shape is another variable of interest in particle-based aAPC systems. Anisotropic aAPC have recently been shown to be more effective than isotropic particles at stimulating T cells, mainly due to enhanced interaction with target cells coupled with reduced non-specific cell uptake. Cells preferentially bind to the long axis of ellipsoidal particles, and the larger radius of curvature and flatter surface allow for more contact between the aAPC and T cell12. The long axis of ellipsoidal particles also discourages phagocytosis, resulting in increased circulation time compared to spherical particles following in vivo administration12,13. Because of these advantages, ellipsoidal particles mediate greater expansion of antigen-specific T cells in vitro and in vivo compared to spherical particles, an effect observed at both the micro and nanoscales12,13. There are various strategies to fabricate anisotropic particles, but thin-film stretching is a simple, widely accepted method used to generate a range of diverse particle shapes14. Following synthesis, particles are cast into films and stretched in one or two dimensions at a temperature above the glass transition temperature of the particle material. The film is then dissolved to retrieve the particles. Despite growing interest in anisotropic particles, current approaches for fabricating particle-based aAPC are mostly limited to isotropic systems, and methods of altering particle shape can be difficult to implement, incompatible with certain aAPC synthesis strategies, and lack precision and reproducibility15. Our thin-film stretching technique can be performed manually or in an automated fashion to rapidly generate anisotropic particles synthesized from a variety of biodegradable polymers, stretched to a desired aspect ratio in one or two dimensions15.
Based on our previous work, we developed a biodegradable particle-based approach combined with scalable thin-film stretching technology to rapidly generate aAPC with tunable size and shape in a standardized fashion for T cell expansion ex vivo or in vivo. Our protein conjugation strategy can be used to couple any protein(s) of interest to carboxyl groups on the particle surface at a desired density, giving this aAPC system a high degree of flexibility. We also describe methods to characterize the size, morphology, and surface protein content of aAPC, and to evaluate their functionality in vitro. This protocol can be easily adapted to expand immune cells ex vivo or in vivo for a variety of immunotherapeutic applications.
All methods described here have been approved by the Institutional Animal Care and Use Committee (IACUC) of Johns Hopkins University.
1. Fabrication of Spherical PLGA Particles of Tunable Size
2. Fabrication of Polymeric Particles of Tunable Shape
3. Surface Protein Conjugation to Create Artificial Antigen Presenting Cells
4. Characterization and Evaluation of aAPC
A schematic for the automated 2D thin film stretching device is given in Figure 1. A schematic and description for a 1D thin film stretching device is given in Ho et al.17 The stretcher is constructed from aluminum parts using standard milling and machining techniques. Similar to the 1D stretcher, the 2D stretcher consists of metallic grips and guide rails. Bidirectional lead screws are used to translate linear to rotational motion. Th...
This protocol details a versatile method for the precise generation of anisotropic polymeric particles. The thin film stretching technique described here is scalable, highly reproducible and inexpensive. Alternative techniques for generating anisotropic particles suffer from many limitations, including high cost, low throughput, and limited particle size. The thin film stretching approach is also advantageous because the particles are modified to be anisotropic after synthesis, and, as a result, is compatible with a wide...
The authors have nothing to disclose.
EBA (DGE-1746891) and KRR (DGE-1232825) thank the NSF Graduate Research Fellowship program for support. RAM thanks the National Research Service Award NIH NCI F31 (F31CA214147) and the Achievement Rewards for College Scientists Fellowship for support. The authors thank the NIH (R01EB016721 and R01CA195503), the Research to Prevent Blindness James and Carole Free Catalyst Award, and the JHU Bloomberg-Kimmel Institute for Cancer Immunotherapy for support.
Name | Company | Catalog Number | Comments |
Poly(vinyl alcohol), MW 25000, 88% hydrolyzed | Polysciences, Inc. | 02975-500 | |
Glycerol | Sigma-Aldrich | G9012 | |
Digital Thermometer | Fluke | N/A | Model name: Fluke 52 II |
Immersion Temperature Probe | Fluke | N/A | Model name: Fluke 80PK 22 |
Digital Hotplate & Stirrer | Benchmark Scientific | H3760-HS | |
Multipoint stirrer | Thermo Fisher Scientific | 50093538 | |
Resomer RG 504 H, Poly(D,L-lactide-co-glycolide) | Sigma-Aldrich | 719900 | |
Dichloromethane | Sigma-Aldrich | D65100 | |
Homogenizer | IKA | 0003725001 | |
Sonicator | Sonics & Materials, Inc. | N/A | Model number: VC 505 |
Sonicator sound abating enclosure | Sonics & Materials, Inc. | N/A | Part number: 630-0427 |
Sonicator probe | Sonics & Materials, Inc. | N/A | Part number: 630-0220 |
Sonicator microtip | Sonics & Materials, Inc. | N/A | Part number: 630-0423 |
High speed centrifuge | Beckman Coulter | N/A | Model number: J-20XP (discontinued), alternative model: J-26XP |
High speed centrifuge rotor | Beckman Coulter | 369691 | Model number: JA-17 |
High speed polycarbonate centrifuge tubes | Thermo Fisher Scientific | 3118-0050 | 50 mL, screw cap |
Rectangular disposable petri dish | VWR International | 25384-322 | 75 x 50 x 10 mm |
Square disposable petri dish | VWR International | 10799-140 | 100 mm x 100 mm |
LEAF Purified anti-mouse CD3ε Antibody | Biolegend | 100314 | |
InVivoMab anti-mouse CD28, clone 37.51 | Bio X Cell | BE0015-1 | |
N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride | Sigma-Aldrich | E6383 | |
N-Hydroxysulfosuccinimide sodium salt | Sigma-Aldrich | 56485 | |
MES | Sigma-Aldrich | M3671 | |
Alexa Fluor 488 anti-mouse CD3 Antibody | Biolegend | 100212 | |
APC anti-mouse CD28 Antibody | Biolegend | 102109 | |
Corning 96 Well Solid Polystyrene Microplate | Sigma-Aldrich | CLS3915 | flat bottom, black polystyrene |
Protein LoBind Tubes, 1.5 mL | Eppendorf | 22431081 | |
RPMI 1640 Medium (+ L-Glutamine) | ThermoFisher Scientific | 11875093 | |
Fetal Bovine Serum | Sigma-Aldrich | F4135 | Heat Inactivated, sterile-filtered |
Ciprofloxacin | Sigma-Aldrich | 17850 | |
2-Mercaptoethanol | Sigma-Aldrich | M6250 | |
Recombinant Human IL-2 (carrier-free) | Biolegend | 589102 | |
Sodium Pyruvate (100 mM) | ThermoFisher Scientific | 11360070 | |
MEM Non-Essential Amino Acids Solution (100X) | ThermoFisher Scientific | 11140050 | |
MEM Vitamin Solution (100X) | ThermoFisher Scientific | 11120052 | |
CD8a+ T Cell Isolation Kit, mouse | Miltenyi Biotech | 130-104-075 | |
CellTrace CFSE Cell Proliferation Kit | ThermoFisher Scientific | C34554 | |
LS Columns | Miltenyi Biotech | 130-042-401 | |
MidiMACS Separator | Miltenyi Biotech | 130-042-302 | |
MACS Multistand | Miltenyi Biotech | 130-042-303 | |
Flow Cytometer | Accuri C6 | ||
Synergy 2 Multi-Detection Microplate Reader | BioTek | ||
autoMACS Running Buffer | Miltenyi BIotech | 130-091-221 | |
Cell Strainer | ThermoFisher Scientific | 22363548 | Sterile, 70 µm nylon mesh |
ACK Lysing Buffer | ThermoFisher Scientific | A1049201 | |
C57BL/6J (Black 6) Mouse | The Jackson Laboratory | 000664 | Male, at least 7 weeks old |
U-Bottom Tissue Culture Plates | VWR | 353227 | Sterile, 96-well tissue culture treated polystyrene plates |
40 V DC Power Supply | Probotix | LPSK-4010 | |
PTFE Coated Wire | Mouser | 602-5858-100-01 | This is for a 100 ft. spool but an equivalent wire will work |
Stepper Motor Driver | Probotix | MondoStep5.6 | |
IDC Connector Kit | Probotix | IDCM-10-12 | |
Microcontroller | Probotix | PBX-RF | |
4A Fuses | Radio Shack | 2701026 | Equivalent fuses will work as well |
DB25 Male to Male Cable | Probotix | DB25-6 | |
USB-A to USB-B Cable | Staples | 2094915 | Equivalent cable will work as well |
8-Pin Amphenol Connectors Male and Female | Mouser | 654-97-3100A-20-7P and 654-97-3106A20-7S | |
Stepper Motor | Probotix | HT23-420-8 | |
Right Hand Lead Screw | Roton | 60722 | |
Left Hand Lead Screw | Roton | 60723 | |
Screws | McMaster Carr | 92196A151 | |
Neoprene Rubber | McMaster Carr | 8698K51 | |
Right Handed Flanged Lead Nut | Roton | 91962 | |
Left Handed Flanged Lead Nut | Roton | 91963 | |
Linux Control Computer | Probotix | LCNC-PC | Any computer with matching specification and Linux operating system will work |
Corning bottle-top vacuum filter system | Sigma-Aldrich | CLS431097 | |
Trypan Blue Solution, 0.4 % | ThermoFisher Scientific | 15250061 |
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