Exploiting Rational Assembly to Map Distinct Roles of Regulatory Cues during Autoimmune Therapy

Induction of Antigen-Specific Tolerance in a Multiple Sclerosis Model without Broad Immunosuppression

Multiple sclerosis (MS) is a severe autoimmune disorder that wreaks havoc on the central nervous system, leading to a spectrum of motor and cognitive impairments. There is no cure, and current treatment strategies rely on broad immunosuppression, leaving patients vulnerable to infections. To address this problem, our approach aims to induce antigen-specific tolerance, a much-needed shift in MS therapy. We have engineered a tolerogenic therapy consisting of spray-dried particles made of a degradable biopolymer, acetalated dextran, and loaded with an antigenic peptide and tolerizing drug, rapamycin (Rapa). After initial characterization and optimization, particles were tested in a myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis model of MS. Representing the earliest possible time of diagnosis, mice were treated at symptom onset in an early therapeutic model, where particles containing MOG and particles containing Rapa+MOG evoked significant reductions in clinical score. Particles were then applied to a highly clinically relevant late therapeutic model during peak disease, where MOG particles and Rapa+MOG particles each elicited a dramatic therapeutic effect, reversing hind limb paralysis and restoring fully functional limbs. To confirm the antigen specificity of our therapy, we immunized mice against the influenza antigen hemagglutinin (HA) and treated them with MOG particles or Rapa+MOG particles. The particles did not suppress antibody responses against HA. Our findings underscore the potential of this particle-based therapy to reverse autoimmunity in disease-relevant models without compromising immune competence, setting it apart from existing treatments.

Engineered Immune Constructs Alter Antigen-Specific Immune Tolerance and Confer Durable Protection in Myelin-Driven Autoimmunity

Autoimmune diseases are broadly characterized as a failure in immune tolerance. In multiple sclerosis (MS), autoreactive immune cells attack the protective myelin sheath lining neurons in the central nervous system. Therapeutic strategies that selectively and durably restore immune tolerance without broad immunosuppression are urgently needed for MS. Our lab has developed assemblies of immune constructs built entirely from myelin antigen (MOG35-55 or PLP139-151) and regulatory innate immune cues (GpG) using layer-by-layer self-assembly. Here, we present mechanistic and translational data showing these assemblies confer therapeutic benefits in a range of clinically relevant disease contexts, including progressive disease in male mice and in relapsing-remitting disease that mimics the intermittent bouts of disease and remission most MS patients initially experience. Here, the antigen component in the complexes is matched to the disease-causing antigen, resulting in a decrease in paralysis in these models. We show that subcutaneous delivery of assemblies durably prevents diseases and drives tolerance by regulatory remodeling of the draining lymph node. Importantly, we show that subcutaneously delivered assemblies recruit and expand antigen-specific regulatory T cells (TREGS) in draining lymph nodes. Finally, we find a shift of these recruited TREGS from a resting to an activated phenotype. Taken together, these data inform the design of therapeutics for antigen-specific tolerance that could combat autoimmunity by exploiting the role of innate pathways in a disease.

Zeolitic imidazolate frameworks activate endosomal Toll-like receptors and potentiate immunogenicity of SARS-CoV-2 spike protein trimer

Nanomaterials offer unique opportunities to engineer immunomodulatory activity. In this work, we report the Toll-like receptor agonist activity of a nanoscale adjuvant zeolitic imidazolate framework-8 (ZIF-8). The accumulation of ZIF-8 in endosomes and the pH-responsive release of its subunits enable selective engagement with endosomal Toll-like receptors, minimizing the risk of off-target activation. The intrinsic adjuvant properties of ZIF-8, along with the efficient delivery and biomimetic presentation of a severe acute respiratory syndrome coronavirus 2 spike protein receptor-binding domain trimer, primed rapid humoral and cell-mediated immunity in a dose-sparing manner. Our study offers insights for next-generation adjuvants that can potentially impact future vaccine development.

Exploiting Unique Features of Microneedles to Modulate Immunity

Microneedle arrays (MNAs) are small patches containing hundreds of short projections that deliver signals directly to dermal layers without causing pain. These technologies are of special interest for immunotherapy and vaccine delivery because they directly target immune cells concentrated in the skin. The targeting abilities of MNAs result in efficient immune responses-often more protective or therapeutic-compared to conventional needle delivery. MNAs also offer logistical benefits, such as self-administration and transportation without refrigeration. Thus, numerous preclinical and clinical studies are exploring these technologies. Here the unique advantages of MNA, as well as critical challenges-such as manufacturing and sterility issues-the field faces to enable widespread deployment are discussed. How MNA design parameters can be exploited for controlled release of vaccines and immunotherapies, and the application to preclinical models of infection, cancer, autoimmunity, and allergies are explained. Specific strategies are also discussed to reduce off-target effects compared to conventional vaccine delivery routes, and novel chemical and manufacturing controls that enable cargo stability in MNAs across flexible intervals and temperatures. Clinical research using MNAs is then examined. Drawbacks of MNAs and the implications, and emerging opportunities to exploit MNAs for immune engineering and clinical use are concluded.

Engineered macromolecular Toll-like receptor agents and assemblies

Macromolecular Toll-like receptor (TLR) agents have been utilized as agonists and inhibitors in preclinical and clinical settings. These agents interface with the TLR class of innate immune receptors which recognize macromolecular ligands that are characteristic of pathogenic material. As such, many agents that have been historically investigated are derived from the natural macromolecules which activate or inhibit TLRs. This review covers recent research and clinically available TLR agents that are macromolecular or polymeric. Synthetic materials that have been found to interface with TLRs are also discussed. Assemblies of these materials are investigated in the context of improving stability or efficacy of ligands. Attention is given to strategies which modify or enhance the current agents and to future outlooks on the development of these agents.

Harnessing Biomaterials to Study and Direct Antigen-Specific Immunotherapy

Immunotherapies are an evolving treatment paradigm for addressing cancer, autoimmunity, and infection. While exciting, most of the existing therapies are limited by their specificity─unable to differentiate between healthy and diseased cells at an antigen-specific level. Biomaterials are a powerful tool that enable the development of next-generation immunotherapies due to their tunable synthesis properties. Our lab harnesses biomaterials as tools to study antigen-specific immunity and as technologies to enable new therapeutic vaccines and immunotherapies to combat cancer, autoimmunity, and infections. Our efforts have spanned the study of intrinsic immune profiles of biomaterials, development of novel nanotechnologies assembled entirely from immune cues, manipulation of innate immune signaling, and advanced technologies to direct and control specialized immune niches such as skin and lymph nodes.

Tuning innate immune function using microneedles containing multiple classes of toll-like receptor agonists

Microneedle arrays (MNAs) are patches displaying hundreds of micron-scale needles that can penetrate skin. As a result, these arrays efficiently and painlessly access this immune cell-rich niche, motivating significant clinical interest in MNA-based vaccines. Our lab has developed immune polyelectrolyte multilayers (iPEMs), nanostructures built entirely from immune signals employing electrostatic self-assembly. iPEMs consist of positively charged peptide antigen and negatively charged toll-like receptor agonists (TLRas) to assemble these components at ultra-high density since no carrier is needed. Here we used this technology to deliver MNAs with antigen and defined ratios of multiple classes of TLRa. Notably, this approach resulted in facile assembly and corresponding signal transduction through each respective TLR pathway. This control ultimately activated primary antigen presenting cells and drove proliferation of antigen-specific T cells. In related in vivo vaccine studies, application of MNAs resulted in distinct T cells response depending on the number of TLRa classes delivered with MNAs. These MNAs technologies create an opportunity to deliver nanostructured vaccine components at high density, and to probe integration of multiple TLRas in skin to tune immunity.

Delivery route considerations for designing antigen-specific biomaterial strategies to combat autoimmunity

Disease modifying drugs and biologics used to treat autoimmune diseases, although promising, are non-curative. As the field moves towards development of new approaches to treat autoimmune disease, antigen-specific therapies immunotherapies (ASITs) have emerged. Despite clinical approval of ASITs for allergies, clinical trials using soluble ASITs for autoimmunity have been largely unsuccessful. A major effort to address this shortcoming is the use of biomaterials to harness the features unique to specific delivery routes. This review focuses on biomaterials being developed for delivery route-specific strategies to induce antigen-specific responses in autoimmune diseases such as multiple sclerosis, type 1 diabetes, rheumatoid arthritis, and celiac disease. We first discuss the delivery strategies used in ongoing and completed clinical trials in autoimmune ASITs. Next, we highlight pre-clinical biomaterial approaches from the most recent 3 years in the context of these same delivery route considerations. Lastly, we provide discussion on the gaps remaining in biomaterials development and comment on the need to consider delivery routes in the process of designing biomaterials for ASITs.

Biomaterial Strategies for Selective Immune Tolerance: Advances and Gaps

Autoimmunity and allergies affect a large number of people across the globe. Current approaches to these diseases target cell types and pathways that drive disease, but these approaches are not cures and cannot differentiate between healthy cells and disease-causing cells. New immunotherapies that induce potent and selective antigen-specific tolerance is a transformative goal of emerging treatments for autoimmunity and serious allergies. These approaches offer the potential of halting-or even reversing-disease, without immunosuppressive side effects. However, translating successful induction of tolerance to patients is unsuccessful. Biomaterials offer strategies to direct and maximize immunological mechanisms of tolerance through unique capabilities such as codelivery of small molecules or signaling molecules, controlling signal density in key immune tissues, and targeting. While a growing body of work in this area demonstrates success in preclinical animal models, these therapies are only recently being evaluated in human trials. This review will highlight the most recent advances in the use of materials to achieve antigen-specific tolerance and provide commentary on the current state of the clinical development of these technologies.

Engineering the lymph node environment promotes antigen-specific efficacy in type 1 diabetes and islet transplantation

Antigen-specific tolerance is a key goal of experimental immunotherapies for autoimmune disease and allograft rejection. This outcome could selectively inhibit detrimental inflammatory immune responses without compromising functional protective immunity. A major challenge facing antigen-specific immunotherapies is ineffective control over immune signal targeting and integration, limiting efficacy and causing systemic non-specific suppression. Here we use intra-lymph node injection of diffusion-limited degradable microparticles that encapsulate self-antigens with the immunomodulatory small molecule, rapamycin. We show this strategy potently inhibits disease during pre-clinical type 1 diabetes and allogenic islet transplantation. Antigen and rapamycin are required for maximal efficacy, and tolerance is accompanied by expansion of antigen-specific regulatory T cells in treated and untreated lymph nodes. The antigen-specific tolerance in type 1 diabetes is systemic but avoids non-specific immune suppression. Further, microparticle treatment results in the development of tolerogenic structural microdomains in lymph nodes. Finally, these local structural and functional changes in lymph nodes promote memory markers among antigen-specific regulatory T cells, and tolerance that is durable. This work supports intra-lymph node injection of tolerogenic microparticles as a powerful platform to promote antigen-dependent efficacy in type 1 diabetes and allogenic islet transplantation.

Enhancing the functionality of self-assembled immune signals using chemical crosslinks

Multiple sclerosis (MS) is an autoimmune disease that develops when dysfunctional autoreactive lymphocytes attack the myelin sheath in the central nervous system. There are no cures for MS, and existing treatments are associated with unwanted side effects. One approach for treating MS is presenting distinct immune signals (i.e., self-antigen and immunomodulatory cues) to innate and adaptive immune cells to engage multiple signaling pathways involved in MS. We previously developed immune polyelectrolyte multilayer (iPEM) complexes built through layer-by-layer deposition of self-antigen - myelin oligodendrocyte glycoprotein (MOG) - and toll-like receptor antagonist, GpG to treat MS. Here, glutaraldehyde-mediated stable cross-links were integrated into iPEMs to load multiple classes of therapeutics. These cross-linked iPEMs maintain their immunological features, including the ability of GpG to blunt toll-like-receptor 9 signaling and MOG to expand T cells expressing myelin-specific T cell receptors. Lastly, we show that these functional assemblies can be loaded with a critical class of drug - mTOR inhibitors - associated with inducing regulatory T cells. These studies demonstrate the ability to incorporate small molecule drugs in reinforced self-assembled immune signals juxtaposed at high densities. This precision technology contributes new technologies that could drive antigen-specific immune response by simultaneously modulating innate and adaptive immunity.

Self-Assembly of Immune Signals to Program Innate Immunity through Rational Adjuvant Design

Recent clinical studies show activating multiple innate immune pathways drives robust responses in infection and cancer. Biomaterials offer useful features to deliver multiple cargos, but add translational complexity and intrinsic immune signatures that complicate rational design. Here a modular adjuvant platform is created using self-assembly to build nanostructured capsules comprised entirely of antigens and multiple classes of toll-like receptor agonists (TLRas). These assemblies sequester TLR to endolysosomes, allowing programmable control over the relative signaling levels transduced through these receptors. Strikingly, this combinatorial control of innate signaling can generate divergent antigen-specific responses against a particular antigen. These assemblies drive reorganization of lymph node stroma to a pro-immune microenvironment, expanding antigen-specific T cells. Excitingly, assemblies built from antigen and multiple TLRas enhance T cell function and antitumor efficacy compared to ad-mixed formulations or capsules with a single TLRa. Finally, capsules built from a clinically relevant human melanoma antigen and up to three TLRa classes enable simultaneous control of signal transduction across each pathway. This creates a facile adjuvant design platform to tailor signaling for vaccines and immunotherapies without using carrier components. The modular nature supports precision juxtaposition of antigen with agonists relevant for several innate receptor families, such as toll, STING, NOD, and RIG.

Mapping the Mechanical and Immunological Profiles of Polymeric Microneedles to Enable Vaccine and Immunotherapy Applications

Biomaterials hold great promise for vaccines and immunotherapy. One emerging biomaterials technology is microneedle (MNs) delivery. MNs are arrays of micrometer-sized needles that are painless and efficiently deliver cargo to the specialized immunological niche of the skin. MNs typically do not require cold storage and eliminate medical sharps. Nearly all materials exhibit intrinsic properties that can bias immune responses toward either pro-immune or inhibitory effects. Thus, because MNs are fabricated from degradable polymers to enable cargo loading and release, understanding the immunological profiles of these matrices is essential to enable new MN vaccines and immunotherapies. Additionally, understanding the mechanical properties is important because MNs must penetrate the skin and conform to a variety of skin or tissue geometries. Here we fabricated MNs from important polymer classes – including extracellular matrix biopolymers, naturally-derived polymers, and synthetic polymers – with both high- and low-molecular-weights (MW). We then characterized the mechanical properties and intrinsic immunological properties of these designs. The library of polymer MNs exhibited diverse mechanical properties, while causing only modest changes in innate signaling and antigen-specific T cell proliferation. These data help inform the selection of MN substrates based on the mechanical and immunological requirements needed for a specific vaccine or immunotherapy application.

Biomaterial-enabled induction of pancreatic-specific regulatory T cells through distinct signal transduction pathways

Autoimmune diseases-where the immune system mistakenly targets self-tissue-remain hindered by non-specific therapies. For example, even molecularly specific monoclonal antibodies fail to distinguish between healthy cells and self-reactive cells. An experimental therapeutic approach involves delivery of self-molecules targeted by autoimmunity, along with immune modulatory signals to produce regulatory T cells (TREG) that selectively stop attack of host tissue. Much has been done to increase the efficiency of signal delivery using biomaterials, including encapsulation in polymer microparticles (MPs) to allow for co-delivery and cargo protection. However, less research has compared particles encapsulating drugs that target different TREG inducing pathways. In this paper, we use poly (lactic-co-glycolide) (PLGA) to co-encapsulate type 1 diabetes (T1D)-relevant antigen and 3 distinct TREG-inducing molecules - rapamycin (Rapa), all-trans retinoic acid (atRA), and butyrate (Buty) - that target the mechanistic target of Rapa (mTOR), the retinoid pathway, and histone deacetylase (HDAC) inhibition, respectively. We show all formulations are effectively taken up by antigen presenting cells (APCs) and that antigen-containing formulations are able to induce proliferation in antigen-specific T cells. Further, atRA and Rapa MP formulations co-loaded with antigen decrease APC activation levels, induce TREG differentiation, and reduce inflammatory cytokines in pancreatic-reactive T cells.