Engineered Microgel Technologies for Modulation and Assessment of Immune Response

Advances in the field of immunology have created many avenues for the development of novel immunotherapies for conditions from autoimmune disorders and tissue defects to vaccine development. Immune system involvement in health maintenance is multifaceted and generally highly localized. Most of the recently developed treatments, however, are applied systemically which leads to hyperactivation or suppression of the immune system at non-target sites. Development of biomaterial scaffolds that can recruit relevant subclasses of the immune system cells and locally modify their phenotype in a controlled manner can reduce the side effects of immunotherapeutics and improve their efficacy.For biomaterials to be successful as local immunomodulatory scaffolds, they should be biodegradable and biocompatible, evading the foreign body response, yet encourage rapid immune cell infiltration, by providing immediate macroporosity. They should also synergize with other developing therapeutics by providing a large cargo capacity and mechanism for tunable controlled release. Finally, such biomaterials should be injectable and have a long shelf-life for ease of clinical application. Many biomaterials have been developed to possess these features; however, all fall short in one aspect or another. Our group has previously developed a novel biomaterial, microporous annealed particle gels, an injectable hydrogel scaffold, that provides immediate porosity to enable cell infiltration and improved wound closure. Here I introduce two novel immunomodulatory hydrogels based on the MAP technology with their applications in tissue regeneration and vaccination. For the first hydrogel technology, I present data on incorporating a minor change in MAP, by crosslinking hydrogels with unnatural D-chirality peptides (D-MAP) which made MAP immunogenic, resulting in type 2 response with IL33 producing macrophages, leading to regenerative healing of the skin. Notably, I show that this response was dependent on the adaptive immunity, without use of immunomodulatory agents or growth factors, highlighting utility of biomaterials in regenerative healing through activation of adaptive immunity. For the second hydrogel technology, I show that incorporation of antigens in the microfluidic fabrication of MAP (VaxMAP) can lead to a robust germinal center development and humoral response. Furthermore, by incorporation of polymeric nanoparticles carrying CpG ODN adjuvants in MAP, I was able to induce class switching of the antibodies to a T-helper 1 dependent isotype. Finally, I showed MAP’s unique capability of inducing different immune responses to two antigens within one vaccination. Together, these studies showcase the utility of MAP in immunomodulatory applications ranging from tissue regeneration to vaccination. At the other end of the spectrum for development of immunotherapeutics, is the in vitro study of immune cells for development of biologic immunotherapies, such as monoclonal antibodies. Phenotypic study of immune cells with single cell resolution is essential for development of such therapeutics. Microscale approaches to study antibody producing cells (APCs) with single cell resolution have been developed but none provide a widely accessible method to isolate target cells at high throughput, and generally require complicated assay formats for phenotypic studies. As such, labor intensive, time consuming, and costly techniques such as hybridoma technology remain the mainstream methods for development of therapeutics. Microgel technologies combined with microfluidic techniques hold promise to resolve these limitations. In the last chapter, I introduce the utility of a novel microparticle platform, nanovials, for performing plate-based secretion assays at single cell level. The nanovials are hydrogel-based cup shaped microparticles which play the role of nanoliter-sizes well plates and can be loaded with individual APCs to capture and assess antigen-specificity of their secreted antibodies. The nanovials are compatible with commercial fluorescence-assisted flowcytometry systems and can be used to sort APCs with a throughput of more than two million APCs in one day. The APCs are sorted alive and can be used for downstream work such as sequencing for antibody discovery, and further functional analysis for study of their biology

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Supplemental figures and table

Improved Humoral Immunity and Protection against Influenza Virus Infection with a 3d Porous Biomaterial Vaccine.

New vaccine platforms that activate humoral immunity and generate neutralizing antibodies are required to combat emerging pathogens, including influenza virus. A slurry of antigen-loaded hydrogel microparticles that anneal to form a porous scaffold with high surface area for antigen uptake by infiltrating immune cells as the biomaterial degrades is demonstrated to enhance humoral immunity. Antigen-loaded-microgels elicited a robust cellular humoral immune response, with increased CD4+ T follicular helper (Tfh) cells and prolonged germinal center (GC) B cells comparable to the commonly used adjuvant, aluminum hydroxide (Alum). Increasing the weight fraction of polymer material led to increased material stiffness and antigen-specific antibody titers superior to Alum. Vaccinating mice with inactivated influenza virus loaded into this more highly cross-linked formulation elicited a strong antibody response and provided protection against a high dose viral challenge. By tuning physical and chemical properties, adjuvanticity can be enhanced leading to humoral immunity and protection against a pathogen, leveraging two different types of antigenic material: individual protein antigen and inactivated virus. The flexibility of the platform may enable design of new vaccines to enhance innate and adaptive immune cell programming to generate and tune high affinity antibodies, a promising approach to generate long-lasting immunity

Cell Delivery: Enhanced In Vivo Delivery of Stem Cells using Microporous Annealed Particle Scaffolds (Small 39/2019)

Delivery to the proper tissue compartment is a major obstacle hampering the potential of cellular therapeutics for medical conditions. Delivery of cells within biomaterials may improve localization, but traditional and newer void-forming hydrogels must be made in advance with cells being added into the scaffold during the manufacturing process. Injectable, in situ cross-linking microporous scaffolds are recently developed that demonstrate a remarkable ability to provide a matrix for cellular proliferation and growth in vitro in three dimensions. The ability of these scaffolds to deliver cells in vivo is currently unknown. Herein, it is shown that mesenchymal stem cells (MSCs) can be co-injected locally with microparticle scaffolds assembled in situ immediately following injection. MSC delivery within a microporous scaffold enhances MSC retention subcutaneously when compared to cell delivery alone or delivery within traditional in situ cross-linked nanoporous hydrogels. After two weeks, endothelial cells forming blood vessels are recruited to the scaffold and cells retaining the MSC marker CD29 remain viable within the scaffold. These findings highlight the utility of this approach in achieving localized delivery of stem cells through an injectable porous matrix while limiting obstacles of introducing cells within the scaffold manufacturing process

A Non-integrating Lentiviral Approach Overcomes Cas9-Induced Immune Rejection to Establish an Immunocompetent Metastatic Renal Cancer Model.

The CRISPR-based technology has revolutionized genome editing in recent years. This technique allows for gene knockout and evaluation of function in cell lines in a manner that is far easier and more accessible than anything previously available. Unfortunately, the ability to extend these studies to in vivo syngeneic murine cell line implantation is limited by an immune response against cells transduced to stably express Cas9. In this study, we demonstrate that a non-integrating lentiviral vector approach can overcome this immune rejection and allow for the growth of transduced cells in an immunocompetent host. This technique enables the establishment of a von Hippel-Lindau (VHL) gene knockout RENCA cell line in BALB/c mice, generating an improved model of immunocompetent, metastatic renal cell carcinoma (RCC)

A Non-integrating Lentiviral Approach Overcomes Cas9-Induced Immune Rejection to Establish an Immunocompetent Metastatic Renal Cancer Model

The CRISPR-based technology has revolutionized genome editing in recent years. This technique allows for gene knockout and evaluation of function in cell lines in a manner that is far easier and more accessible than anything previously available. Unfortunately, the ability to extend these studies to in vivo syngeneic murine cell line implantation is limited by an immune response against cells transduced to stably express Cas9. In this study, we demonstrate that a non-integrating lentiviral vector approach can overcome this immune rejection and allow for the growth of transduced cells in an immunocompetent host. This technique enables the establishment of a von Hippel-Lindau (VHL) gene knockout RENCA cell line in BALB/c mice, generating an improved model of immunocompetent, metastatic renal cell carcinoma (RCC)

High-throughput selection of cells based on accumulated growth and division using PicoShell particles.

Production of high-energy lipids by microalgae may provide a sustainable energy source that can help tackle climate change. However, microalgae engineered to produce more lipids usually grow slowly, leading to reduced overall yields. Unfortunately, culture vessels used to select cells based on growth while maintaining high biomass production, such as well plates, water-in-oil droplet emulsions, and nanowell arrays, do not provide production-relevant environments that cells experience in scaled-up cultures (e.g., bioreactors or outdoor cultivation farms). As a result, strains that are developed in the laboratory may not exhibit the same beneficial phenotypic behavior when transferred to industrial production. Here, we introduce PicoShells, picoliter-scale porous hydrogel compartments, that enable >100,000 individual cells to be compartmentalized, cultured in production-relevant environments, and selected based on growth and bioproduct accumulation traits using standard flow cytometers. PicoShells consist of a hollow inner cavity where cells are encapsulated and a porous outer shell that allows for continuous solution exchange with the external environment. PicoShells allow for cell growth directly in culture environments, such as shaking flasks and bioreactors. We experimentally demonstrate that Chlorella sp., Saccharomyces cerevisiae, and Chinese hamster ovary cells, used for bioproduction, grow to significantly larger colony sizes in PicoShells than in water-in-oil droplet emulsions (P < 0.05). We also demonstrate that PicoShells containing faster dividing and growing Chlorella clonal colonies can be selected using a fluorescence-activated cell sorter and regrown. Using the PicoShell process, we select a Chlorella population that accumulates chlorophyll 8% faster than does an unselected population after a single selection cycle

Improved Humoral Immunity and Protection against Influenza Virus Infection with a 3d Porous Biomaterial Vaccine

Abstract New vaccine platforms that activate humoral immunity and generate neutralizing antibodies are required to combat emerging pathogens, including influenza virus. A slurry of antigen‐loaded hydrogel microparticles that anneal to form a porous scaffold with high surface area for antigen uptake by infiltrating immune cells as the biomaterial degrades is demonstrated to enhance humoral immunity. Antigen‐loaded‐microgels elicited a robust cellular humoral immune response, with increased CD4+ T follicular helper (Tfh) cells and prolonged germinal center (GC) B cells comparable to the commonly used adjuvant, aluminum hydroxide (Alum). Increasing the weight fraction of polymer material led to increased material stiffness and antigen‐specific antibody titers superior to Alum. Vaccinating mice with inactivated influenza virus loaded into this more highly cross‐linked formulation elicited a strong antibody response and provided protection against a high dose viral challenge. By tuning physical and chemical properties, adjuvanticity can be enhanced leading to humoral immunity and protection against a pathogen, leveraging two different types of antigenic material: individual protein antigen and inactivated virus. The flexibility of the platform may enable design of new vaccines to enhance innate and adaptive immune cell programming to generate and tune high affinity antibodies, a promising approach to generate long‐lasting immunity

Injectable Drug‐Releasing Microporous Annealed Particle Scaffolds for Treating Myocardial Infarction

Intramyocardial injection of hydrogels offers great potential for treating myocardial infarction (MI) in a minimally invasive manner. However, traditional bulk hydrogels generally lack microporous structures to support rapid tissue ingrowth and biochemical signals to prevent fibrotic remodeling toward heart failure. To address such challenges, a novel drug-releasing microporous annealed particle (drugMAP) system is developed by encapsulating hydrophobic drug-loaded nanoparticles into microgel building blocks via microfluidic manufacturing. By modulating nanoparticle hydrophilicity and pregel solution viscosity, drugMAP building blocks are generated with consistent and homogeneous encapsulation of nanoparticles. In addition, the complementary effects of forskolin (F) and Repsox (R) on the functional modulations of cardiomyocytes, fibroblasts, and endothelial cells in vitro are demonstrated. After that, both hydrophobic drugs (F and R) are loaded into drugMAP to generate FR/drugMAP for MI therapy in a rat model. The intramyocardial injection of MAP gel improves left ventricular functions, which are further enhanced by FR/drugMAP treatment with increased angiogenesis and reduced fibrosis and inflammatory response. This drugMAP platform represents a new generation of microgel particles for MI therapy and will have broad applications in regenerative medicine and disease therapy

Activating an adaptive immune response from a hydrogel scaffold imparts regenerative wound healing.

Microporous annealed particle (MAP) scaffolds are flowable, in situ crosslinked, microporous scaffolds composed of microgel building blocks and were previously shown to accelerate wound healing. To promote more extensive tissue ingrowth before scaffold degradation, we aimed to slow MAP degradation by switching the chirality of the crosslinking peptides from L- to D-amino acids. Unexpectedly, despite showing the predicted slower enzymatic degradation in vitro, D-peptide crosslinked MAP hydrogel (D-MAP) hastened material degradation in vivo and imparted significant tissue regeneration to healed cutaneous wounds, including increased tensile strength and hair neogenesis. MAP scaffolds recruit IL-33 type 2 myeloid cells, which is amplified in the presence of D-peptides. Remarkably, D-MAP elicited significant antigen-specific immunity against the D-chiral peptides, and an intact adaptive immune system was required for the hydrogel-induced skin regeneration. These findings demonstrate that the generation of an adaptive immune response from a biomaterial is sufficient to induce cutaneous regenerative healing despite faster scaffold degradation