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Enrich and Expand Rare Antigen-specific T Cells with Magnetic Nanoparticles

We have developed a tool to both enrich and expand antigen-specific T cells. This can be helpful in cases such as to A) detect the existence of ...

Johns Hopkins University

As nanoparticle (NP)-mediated drug delivery research continues to expand, understanding parameters that govern NP interactions with the biological environment becomes paramount. The principles identified from the study of these parameters can be used to engineer new NPs, impart unique functionalities, identify novel utilities, and improve the clinical translation of NP formulations. One key design parameter is NP size. New methods have been developed to produce NPs with increased control of NP size between 10 and 200nm, a size range most relevant to physical and biochemical targeting through both intravascular and site-specific deliveries. Three notable techniques best suited for generating polymeric NPs with narrow size distributions are highlighted in this review: self-assembly, microfluidics-based preparation, and flash nanoprecipitation. Furthermore, the effect of NP size on the biological fate and transport properties at the molecular scale (protein-NP interactions) and the tissue and systemic scale (convective and diffusive transport of NPs) are analyzed here. These analyses underscore the importance of NP size control in considering clinical translation and assessment of therapeutic outcomes of NP delivery vehicles. 

Control of polymeric nanoparticle size to improve therapeutic delivery.

Particles engineered to engage and interact with cell surface ligands and to modulate cells can be harnessed to explore basic biological questions as well as to devise cellular therapies. Biology has inspired the design of these particles, such as artificial antigen-presenting cells (aAPCs) for use in immunotherapy. While much has been learned about mimicking antigen presenting cell biology, as we decrease the size of aAPCs to the nanometer scale, we need to extend biomimetic design to include considerations of T cell biology-including T-cell receptor (TCR) organization. Here we describe the first quantitative analysis of particle size effect on aAPCs with both Signals 1 and 2 based on T cell biology. We show that aAPCs, larger than 300 nm, activate T cells more efficiently than smaller aAPCs, 50 nm. The 50 nm aAPCs require saturating doses or require artificial magnetic clustering to activate T cells. Increasing ligand density alone on the 50 nm aAPCs did not increase their ability to stimulate CD8+ T cells, confirming the size-dependent phenomenon. These data support the need for multireceptor ligation and activation of T-cell receptor (TCR) nanoclusters of similar sizes to 300 nm aAPCs. Quantitative analysis and modeling of a nanoparticle system provides insight into engineering constraints of aAPCs for T cell immunotherapy applications and offers a case study for other cell-modulating particles.

Biologically Inspired Design of Nanoparticle Artificial Antigen-Presenting Cells for Immunomodulation.

T cells are crucial contributors to mounting an effective immune response and increasingly the focus of therapeutic interventions in cancer, infectious disease, and autoimmunity. Translation of current T cell immunotherapies has been hindered by off-target toxicities, limited efficacy, biological variability, and high costs. As T cell therapeutics continue to develop, the application of engineering concepts to control their delivery and presentation will be critical for their success. Here, we outline the engineer's toolbox and contextualize it with the biology of T cells. We focus on the design principles of T cell modulation platforms regarding size, shape, material, and ligand choice. Furthermore, we review how application of these design principles has already impacted T cell immunotherapies and our understanding of T cell biology. Recent, salient examples from protein engineering, synthetic particles, cellular and genetic engineering, and scaffolds and surfaces are provided to reinforce the importance of design considerations. Our aim is to provide a guide for immunologists, engineers, clinicians, and the pharmaceutical sector for the design of T cell-targeting platforms.

Engineering Platforms for T Cell Modulation.

Magnetic particles can enrich desired cell populations to aid in understanding cell-type functions and mechanisms, diagnosis, and therapy. As cells are heterogeneous in ligand type, location, expression, and density, careful consideration of magnetic particle design for positive isolation is necessary. Antigen-specific immune cells have low frequencies, which has made studying, identifying, and utilizing these cells for therapy a challenge. Here we demonstrate the importance of magnetic particle design based on the biology of T cells. We create magnetic particles which recognize rare antigen-specific T cells and quantitatively investigate important particle properties including size, concentration, ligand density, and ligand choice in enriching these rare cells. We observe competing optima among particle parameters, with 300 nm particles functionalized with a high density of antigen-specific ligand achieving the highest enrichment and recovery of target cells. In enriching and then activating an endogenous response, 300 nm aAPCs generate nearly 65% antigen-specific T cells with at least 450-fold expansion from endogenous precursors and a 5-fold increase in numbers of antigen-specific cells after only seven days. This systematic study of particle properties in magnetic enrichment provides a case study for the engineering design principles of particles for the isolation of rare cells through biological ligands.

John W. Hickey

Johns Hopkins University

Enrich and Expand Rare Antigen-specific T Cells with Magnetic Nanoparticles