Co-delivery of autoantigen and b7 pathway modulators suppresses experimental autoimmune encephalomyelitis

Mechanistic contributions of Kupffer cells and liver sinusoidal endothelial cells in nanoparticle-induced antigen-specific immune tolerance

The intravenous delivery of disease-relevant antigens (Ag) by polymeric nanoparticles (NP-Ags) has demonstrated Ag-specific immune tolerance in autoimmune and allergic disorders as well as allogeneic transplant rejection. NP-Ags are observed to distribute to the spleen, which has an established role in the induction of immune tolerance. However, studies have shown that the spleen is dispensable for NP-Ag-induced tolerance, suggesting significant contributions from other immunological sites. Here, we investigated the tolerogenic contributions of Kupffer cells (KCs) and liver sinusoidal endothelial cells (LSECs) to NP-Ag-induced tolerance in a mouse model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). Intravenously delivered Ag-conjugated poly(lactide-co-glycolide) NPs (PLG-Ag) distributed largely to the liver, where they associated with both KCs and LSECs. This distribution was accompanied by CD4 T cell accumulation, clonal deletion, and PD-L1 expression by KCs and LSECs. Ex vivo co-cultures of PLG-Ag-treated KCs or LSECs with Ag-specific CD4 T cells resulted in PGE2 and IL-10 or PGE2 secretion, respectively. KC depletion and adoptive transfer experiments demonstrated that KCs were sufficient, but not necessary, to mediate PLG-Ag-induced tolerance in EAE. The durability of PLG-Ag-induced tolerance in the absence of KCs may be attributed to the distribution of PLG-Ags to LSECs, which demonstrated similar levels of PD-L1, PGE2, and T cell stimulatory ability. Collectively, these studies provide mechanistic support for the role of liver KCs and LSECs in Ag-specific tolerance for a biomaterial platform that is currently being evaluated in clinical trials.

Biomaterial-based approaches to engineering immune tolerance

The development of biomaterial-based therapeutics to induce immune tolerance holds great promise for the treatment of autoimmune diseases, allergy, and graft rejection in transplantation. Historical approaches to treat these immunological challenges have primarily relied on systemic delivery of broadly-acting immunosuppressive agents that confer undesirable, off-target effects. The evolution and expansion of biomaterial platforms has proven to be a powerful tool in engineering immunotherapeutics and enabled a great diversity of novel and targeted approaches in engineering immune tolerance, with the potential to eliminate side effects associated with systemic, non-specific immunosuppressive approaches. In this review, we summarize the technological advances within three broad biomaterials-based strategies to engineering immune tolerance: nonspecific tolerogenic agent delivery, antigen-specific tolerogenic therapy, and the emergent area of tolerogenic cell therapy.

Antigen-Specific Treatment Modalities in MS: The Past, the Present, and the Future

Antigen-specific therapy for multiple sclerosis may lead to a more effective therapy by induction of tolerance to a wide range of myelin-derived antigens without hampering the normal surveillance and effector function of the immune system. Numerous attempts to restore tolerance toward myelin-derived antigens have been made over the past decades, both in animal models of multiple sclerosis and in clinical trials for multiple sclerosis patients. In this review, we will give an overview of the current approaches for antigen-specific therapy that are in clinical development for multiple sclerosis as well provide an insight into the challenges for future antigen-specific treatment strategies for multiple sclerosis.

Recent Advances in Antigen-Specific Immunotherapies for the Treatment of Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system and is considered to be the leading non-traumatic cause of neurological disability in young adults. Current treatments for MS comprise long-term immunosuppressant drugs and disease-modifying therapies (DMTs) designed to alter its progress with the enhanced risk of severe side effects. The Holy Grail for the treatment of MS is to specifically suppress the disease while at the same time allow the immune system to be functionally active against infectious diseases and malignancy. This could be achieved via the development of immunotherapies designed to specifically suppress immune responses to self-antigens (e.g., myelin antigens). The present study attempts to highlight the various antigen-specific immunotherapies developed so far for the treatment of multiple sclerosis (e.g., vaccination with myelin-derived peptides/proteins, plasmid DNA encoding myelin epitopes, tolerogenic dendritic cells pulsed with encephalitogenic epitopes of myelin proteins, attenuated autologous T cells specific for myelin antigens, T cell receptor peptides, carriers loaded/conjugated with myelin immunodominant peptides, etc), focusing on the outcome of their recent preclinical and clinical evaluation, and to shed light on the mechanisms involved in the immunopathogenesis and treatment of multiple sclerosis.

Alcohol and multiple sclerosis: an immune system-based review

Multiple sclerosis is a chronic inflammatory disease of the central nervous system (CNS). Although the exact etiology of multiple sclerosis is unknown, researchers suggest that genetic, environmental, and microbial factors play a central role in causing multiple sclerosis. Pathology of multiple sclerosis is based on inflammation as T cells enter the brain via disruptions in the blood-brain barrier, recognizing myelin as foreign antigen; and as a result, the T cells attack myelin and start the inflammatory processes, enhancing inflammatory cytokines and antibodies. Since previous studies show ethanol can suppress the immune system such as innate, humoral, and cellular immunity and increases the production of anti-inflammatory cytokines, we hypothesized maybe ethanol also have ameliorating effects on multiple sclerosis symptoms. Although alcohol induces apoptosis in oligodendrocytes and neurons, causing demyelination and affects CNS directly, in this study we will investigate ethanol's effects on some aspects of the immune system in multiple sclerosis.

Designing inorganic nanomaterials for vaccines and immunotherapies

Vaccines and immunotherapies have changed the face of health care. Biomaterials offer the ability to improve upon these medical technologies through increased control of the types and concentrations of immune signals delivered. Further, these carriers enable targeting, stability, and delivery of poorly soluble cargos. Inorganic nanomaterials possess unique optical, electric, and magnetic properties, as well as defined chemistry, high surface-to-volume- ratio, and high avidity display that make this class of materials particularly advantageous for vaccine design, cancer immunotherapy, and autoimmune treatments. In this review we focus on this understudied area by highlighting recent work with inorganic materials - including gold nanoparticles, carbon nanotubes, and quantum dots. We discuss the intrinsic features of these materials that impact the interactions with immune cells and tissue, as well as recent reports using inorganic materials across a range of emerging immunological applications.

Soluble Antigen Arrays Displaying Mimotopes Direct the Response of Diabetogenic T Cells

Type 1 diabetes (T1D) is an autoimmune disorder which develops when insulin-producing, pancreatic beta cells are destroyed by an aberrant immune response. Current therapies for T1D either treat symptoms or cause global immunosuppression, which leave patients at risk of developing long-term complications or vulnerable to foreign pathogens. Antigen-specific immunotherapies have emerged as a selective approach for autoimmune diseases by inducing tolerance while mitigating global immunosuppression. We previously reported SAgAs with multiple copies of a multiple sclerosis (MS) autoantigen grafted onto hyaluronic acid (HA) as an efficacious therapy in experimental autoimmune encephalomyelitis. While the immune response of MS is distinct from that of T1D, the mechanism of SAgAs was hypothesized to be similar and via induction of immune tolerance to diabetes antigens. We synthesized SAgAs composed of HA polymer backbone conjugated with multiple copies of the T1D autoantigen mimotope p79 using aminooxy chemistry (SAgA_p79) or using copper-catalyzed alkyne-azide cycloaddition (cSAgA_p79) chemistry. SAgAs constructed using the hydrolyzable aminooxy linkage, thus capable of releasing p79, exhibited physicochemical properties similar to the triazole linkage. Both SAgA_p79 versions showed high specificity and efficacy in stimulating epitope-specific T cells. SAgAs can be taken up by most immune cell populations but do not induce their maturation, and conventional dendritic cells are responsible for the brunt of antigen presentation within splenocytes. cSAgA_p79 was more stimulatory than SAgA_p79 both in vitro and in vivo, an effect that was ascribed to the peptide modification rather than the type of linkage. In summary, we provide here the first proof-of-principle that SAgA therapy could also be applicable to T1D.

Engineering Biomaterials to Direct Innate Immunity

Small alterations during early stages of innate immune response can drive large changes in how adaptive immune cells develop and function during protective immunity or disease. Controlling these events creates exciting potential in development of immune engineered vaccines and therapeutics. This progress report discusses recent biomaterial technologies exploiting innate immunity to dissect immune function and to design new vaccines and immunotherapies for infectious diseases, cancer, and autoimmunity. Across these examples, an important idea is the possibility to co-opt innate immune mechanisms to enhance immunity during infection and cancer. During inflammatory or autoimmune disease, some of these same innate immune mechanisms can be manipulated in different ways to control excess inflammation by promotion of immunological tolerance.

Acute B-Cell Inhibition by Soluble Antigen Arrays Is Valency-Dependent and Predicts Immunomodulation in Splenocytes

Antigen valency plays a fundamental role in directing the nature of an immune response to be stimulatory or tolerogenic. Soluble antigen arrays (SAgAs) are an antigen-specific immunotherapy that combats autoimmunity through the multivalent display of autoantigen. Although mechanistic studies have shown SAgAs to induce T- and B-cell anergy, the effect of SAgA valency has never been experimentally tested. Here, SAgAs of discrete antigen valencies were synthesized by click chemistry and evaluated for acute B-cell signaling inhibition as well as downstream immunomodulatory effects in splenocytes. Initial studies using the Raji B-cell line demonstrated SAgA valency dictated the extent of calcium flux. Lower valency constructs elicited the largest reductions in B-cell activation. In splenocytes from mice with experimental autoimmune encephalomyelitis, the same valency-dependent effects were evident in the downregulation of the costimulatory marker CD86. The reduction of calcium flux observed in Raji B-cells correlated strongly with downregulation in splenocyte CD86 expression after 72 h. Here, a thorough analysis of SAgA antigenic valency illustrates that low, but not monovalent, presentation of autoantigen was ideal for eliciting the most potent immunomodulatory effects.

Soluble Antigen Arrays for Selective Desensitization of Insulin-Reactive B Cells

Autoimmune diseases are believed to be highly dependent on loss of immune tolerance to self-antigens. Currently, no treatments have been successful clinically in inducing autoantigen-specific tolerance, including efforts to utilize antigen-specific immunotherapy (ASIT) to selectively correct the aberrant autoimmunity. Soluble antigen arrays (SAgAs) represent a novel autoantigen delivery system composed of a linear polymer, hyaluronic acid (HA), displaying multiple copies of conjugated autoantigen. We have previously reported that soluble antigen arrays displaying proteolipid peptide (SAgA_PLP) induced tolerance to this specific multiple sclerosis (MS) autoantigen. Utilizing SAgA technology, we have developed a new ASIT as a possible type 1 diabetes (T1D) therapeutic by conjugating human insulin to HA, known as soluble antigen array insulin (SAgA_Ins). Three types were synthesized, low valency _lvSAgA_Ins (2 insulins per HA), medium valency _mvSAgA_Ins (4 insulins per HA), and, high valency _hvSAgA_Ins (9 insulins per HA), to determine if valency differentially modulates the ex vivo activity of insulin-binding B cells (IBCs). Extensive biophysical characterization was performed for the SAgA molecules. SAgA_Ins molecules were successfully used to affect the biologic activity of IBCs by inducing desensitization of the B cell antigen receptors (BCR). SAgA_Ins bound specifically to insulin-reactive B cells without blocking epitopes recognized by antibodies against the Fc regions of membrane immunoglobulin or CD79 transducer components of the BCR. Preincubation of IBCs (125Tg) with SAgA_Ins, but not HA alone, rendered the IBCs refractory to restimulation. SAgA_Ins induced a decrease in BCR expression and IP3R-mediated intracellular calcium release. Surprisingly, SAgA_Ins binding to BCR on the surface of IBCs induced the observed effects at both high and low SAgA_Ins valency. Future studies aim to test the effects of SAgA_Ins on disease progression in the VH125.NOD mouse model of T1D.

Tocopherol Emulsions as Functional Autoantigen Delivery Vehicles Evoke Therapeutic Efficacy in Experimental Autoimmune Encephalomyelitis

Contemporary approaches to treating autoimmune diseases like multiple sclerosis broadly modulate the immune system and leave patients susceptible to severe adverse effects. Antigen-specific immunotherapies (ASIT) offer a unique opportunity to selectively suppress autoreactive cell populations but have suffered from marginal efficacy even when employing traditional adjuvants to improve delivery. The development of immunologically active antigen delivery vehicles could potentially increase the clinical success of antigen-specific immunotherapies. An emulsion of the antioxidant tocopherol delivering an epitope of proteolipid protein autoantigen (PLP139-151) yielded significant efficacy in mice with experimental autoimmune encephalomyelitis (EAE). In vitro studies indicated tocopherol emulsions reduced oxidative stress in antigen-presenting cells. Ex vivo analysis revealed that tocopherol emulsions shifted cytokine responses in EAE splenocytes. In addition, IgG responses against PLP139-151 were increased in mice treated with tocopherol emulsions delivering the antigen, suggesting a possible skew in immunity. Overall, tocopherol emulsions provide a functional delivery vehicle for ASIT capable of ameliorating autoimmunity in a murine model.

Engineering Immune Tolerance with Biomaterials

Autoimmune diseases, rejection of transplanted organs and grafts, chronic inflammatory diseases, and immune-mediated rejection of biologic drugs impact a large number of people across the globe. New understanding of immune function is revealing exciting opportunities to help tackle these challenges by harnessing-or correcting-the specificity of immune function. However, realizing this potential requires precision control over the interaction between regulatory immune cues, antigens attacked during inflammation, and the tissues where these processes occur. Engineered materials-such as polymeric and lipid particles, scaffolds, and inorganic materials-offer powerful features that can help to selectively regulate immune function during disease without compromising healthy immune functions. This review highlights some of the exciting developments to leverage biomaterials as carriers, depots, scaffolds-and even as agents with intrinsic immunomodulatory features-to promote immunological tolerance.

Antigen-Specific Tolerization and Targeted Delivery as Therapeutic Strategies for Autoimmune Diseases

The prevalence of autoimmune disorders is increasing steadily and there is no permanent cure available. Immunomodulation through repeated exposure of antigens, known as antigen-specific immune tolerance or antigen-specific immunotherapy (ASI), is a promising approach to treat or prevent autoimmune disorders. Different optimization protocols (immunization routes, delivery systems, and approaches) are being developed to implement ASI against self-proteins. Including appropriate adjuvants, altered peptide ligand, and using multipeptides are approaches that can be used to specifically target autoimmunity. This review explores various ASI application methods, including different routes of antigen-specific sensitization, delivery systems, immunomodulators containing specific antigens, and other targeted approaches that have been successfully demonstrated to have therapeutic effects on autoimmune diseases.

Reprogramming the Local Lymph Node Microenvironment Promotes Tolerance that Is Systemic and Antigen Specific

Many experimental therapies for autoimmune diseases, such as multiple sclerosis (MS), aim to bias T cells toward tolerogenic phenotypes without broad suppression. However, the link between local signal integration in lymph nodes (LNs) and the specificity of systemic tolerance is not well understood. We used intra-LN injection of polymer particles to study tolerance as a function of signals in the LN microenvironment. In a mouse MS model, intra-LN introduction of encapsulated myelin self-antigen and a regulatory signal (rapamycin) permanently reversed paralysis after one treatment during peak disease. Therapeutic effects were myelin specific, required antigen encapsulation, and were less potent without rapamycin. This efficacy was accompanied by local LN reorganization, reduced inflammation, systemic expansion of regulatory T cells, and reduced T cell infiltration to the CNS. Our findings suggest that local control over signaling in distinct LNs can promote cell types and functions that drive tolerance that is systemic but antigen specific.

Co-delivery of autoantigen and dexamethasone in incomplete Freund's adjuvant ameliorates experimental autoimmune encephalomyelitis

Current therapies for autoimmune diseases focus on treating the symptoms rather than the underlying disease cause. A major setback in improving current therapeutics for autoimmunity is the lack of antigen specificity. Successful antigen-specific immunotherapy (ASIT) would allow for improved treatment of autoimmune diseases. In this work, dexamethasone was co-delivered with autoantigen (PLP) in vivo to create effective ASIT for the treatment of experimental autoimmune encephalomyelitis (EAE). Using an emulsion of incomplete Freund's adjuvant (IFA) as a co-delivery vehicle, it was discovered that the controlled release of autoantigen was important for the suppression of clinical disease symptoms. Analysis of the immune response via cytokines revealed that dexamethasone was important for shifting the immune response away from inflammation. Co-delivery of both autoantigen and dexamethasone increased B-cell populations and antibody production, signifying an increased humoral immune response. Overall, this data indicated that the co-delivery of PLP and dexamethasone with a water-in-oil emulsion is effective in treating a murine autoimmune model.

Pulmonary Administration of Soluble Antigen Arrays Is Superior to Antigen in Treatment of Experimental Autoimmune Encephalomyelitis

Antigen-specific immunotherapy has been used to hyposensitize patients to allergens and offers an enticing approach for attenuating autoimmune diseases. Applying antigen-specific immunotherapy to mucosal surfaces such as the lungs may engage unique immune response pathways to improve efficacy. Pulmonary delivery of soluble antigen arrays (SAgAs) was explored in mice with experimental autoimmune encephalomyelitis (EAE), a multiple sclerosis model. SAgAs were designed to impede immune response to autoantigen epitopes and are composed of a hyaluronan backbone with peptides PLP_139-151 (proteolipid protein) and LABL, a disease-causing proteolipid peptide epitope and an intracellular cell-adhesion molecule-1 ligand, respectively. Pulmonary instillation of SAgAs decreased disease score, improved weight gain, and decreased incidence of disease in EAE mice compared to pulmonary delivery of hyaluronic acid polymer, LABL, or PLP. Interestingly, treating with PLP alone also showed some improvement. Splenocytes from SAgA-treated animals showed increased interferon-gamma levels, and interleukin-6 (IL-6) and IL-17 were elevated in SAgA-treated animals compared to PLP treatments. IL-10, IL-2, and tumor necrosis factor-alpha levels showed no significant difference, yet trends across all cytokines suggested SAgAs induced a very different immune response compared to treatment with PLP alone. This work suggests that codelivery of peptide components is essential when treating EAE via pulmonary instillation, and the immune response may have shifted toward immune tolerance.

Multivalent Soluble Antigen Arrays Exhibit High Avidity Binding and Modulation of B Cell Receptor-Mediated Signaling to Drive Efficacy against Experimental Autoimmune Encephalomyelitis

A pressing need exists for antigen-specific immunotherapies (ASIT) that induce selective tolerance in autoimmune disease while avoiding deleterious global immunosuppression. Multivalent soluble antigen arrays (SAgA_PLP:LABL), consisting of a hyaluronic acid (HA) linear polymer backbone cografted with multiple copies of autoantigen (PLP) and cell adhesion inhibitor (LABL) peptides, are designed to induce tolerance to a specific multiple sclerosis (MS) autoantigen. Previous studies established that hydrolyzable SAgA_PLP:LABL, employing a degradable linker to codeliver PLP and LABL, was therapeutic in experimental autoimmune encephalomyelitis (EAE) in vivo and exhibited antigen-specific binding with B cells, targeted the B cell receptor (BCR), and dampened BCR-mediated signaling in vitro. Our results pointed to sustained BCR engagement as the SAgA_PLP:LABL therapeutic mechanism, so we developed a new version of the SAgA molecule using nonhydrolyzable conjugation chemistry, hypothesizing it would enhance and maintain the molecule's action at the cell surface to improve efficacy. "Click SAgA" (cSAgA_PLP:LABL) uses hydrolytically stable covalent conjugation chemistry (Copper-catalyzed Azide-Alkyne Cycloaddition (CuAAC)) rather than a hydrolyzable oxime bond to attach PLP and LABL to HA. We explored cSAgA_PLP:LABL B cell engagement and modulation of BCR-mediated signaling in vitro through flow cytometry binding and calcium flux signaling assays. Indeed, cSAgA_PLP:LABL exhibited higher avidity B cell binding and greater dampening of BCR-mediated signaling than hydrolyzable SAgA_PLP:LABL. Furthermore, cSAgA_PLP:LABL exhibited significantly enhanced in vivo efficacy compared to hydrolyzable SAgA_PLP:LABL, achieving equivalent efficacy at one-quarter of the dose. These results indicate that nonhydrolyzable conjugation increased the avidity of cSAgA_PLP:LABL to drive in vivo efficacy through modulated BCR-mediated signaling.

Conjugates of Cell Adhesion Peptides for Therapeutics and Diagnostics Against Cancer and Autoimmune Diseases

Overexpressed cell-surface receptors are hallmarks of many disease states and are often used as markers for targeting diseased cells over healthy counterparts. Cell adhesion peptides, which are often derived from interacting regions of these receptor-ligand proteins, mimic surfaces of intact proteins and, thus, have been studied as targeting agents for various payloads to certain cell targets for cancers and autoimmune diseases. Because many cytotoxic agents in the free form are often harmful to healthy cells, the use of cell adhesion peptides in targeting their delivery to diseased cells has been studied to potentially reduce required effective doses and associated harmful side-effects. In this review, multiple cell adhesion peptides from extracellular matrix and ICAM proteins were used to selectively direct drug payloads, signal-inhibitor peptides, and diagnostic molecules, to diseased cells over normal counterparts. RGD constructs have been used to improve the selectivity and efficacy of diagnostic and drug-peptide conjugates against cancer cells. From this precedent, novel conjugates of antigenic and cell adhesion peptides, called Bifunctional Peptide Inhibitors (BPIs), have been designed to selectively regulate immune cells and suppress harmful inflammatory responses in autoimmune diseases. Similar peptide conjugations with imaging agents have delivered promising diagnostic methods in animal models of rheumatoid arthritis. BPIs have also been shown to generate immune tolerance and suppress autoimmune diseases in animal models of type-1 diabetes, rheumatoid arthritis, and multiple sclerosis. Collectively, these studies show the potential of cell adhesion peptides in improving the delivery of drugs and diagnostic agents to diseased cells in clinical settings.

Polyplexes assembled from self-peptides and regulatory nucleic acids blunt toll-like receptor signaling to combat autoimmunity

Autoimmune diseases occur when the immune system incorrectly recognizes self-molecules as foreign; in the case of multiple sclerosis (MS), myelin is attacked. Intriguingly, new studies reveal toll-like receptors (TLRs), pathways usually involved in generating immune responses against pathogens, play a significant role in driving autoimmune disease in both humans and animal models. We reasoned polyplexes formed from myelin self-antigen and regulatory TLR antagonists might limit TLR signaling during differentiation of myelin-specific T cells, inducing tolerance by biasing T cells away from inflammatory phenotypes. Complexes were formed by modifying myelin peptide with cationic amino acids to create peptides able to condense the anionic nucleic-acid based TLR antagonist. These immunological polyplexes eliminate synthetic polymers commonly used to condense polyplexes and do not rely on gene expression; however, the complexes mimic key features of traditional polyplexes such as tunable loading and co-delivery. Using these materials and classic polyplex analysis techniques, we demonstrate condensation of both immune signals, protection from enzymatic degradation, and tunable physicochemical properties. We show polyplexes reduce TLR signaling, and in primary dendritic cell and T cell co-culture, reduce myelin-driven inflammation. During mouse models of MS, these tolerogenic polyplexes improve the progression, severity, and incidence of disease.

Combining antigen and immunomodulators: Emerging trends in antigen-specific immunotherapy for autoimmunity

A majority of current therapies for autoimmune diseases are general immunosuppressants, which can compromise patient response to opportunistic infection and lead to adverse events. Using antigen-specific immunotherapy (ASIT) to selectively disarm autoimmune diseases, without suppressing the global immune response, would be a transformative therapy for patients. ASIT has been used historically in allergy hyposensitization therapy to induce tolerance to an allergen. Similar strategies to induce immune tolerance toward autoantigens responsible for autoimmune disease have been attempted but have yielded limited clinical success. Recent studies of ASIT for autoimmunity have explored combination therapy, combining the disease-causing autoantigen with an immunomodulatory compound. ASIT combination therapy may direct the immune response in an antigen-specific manner, potentially reversing the root cause of autoimmunity while limiting side effects. This review analyzes recent advances in ASIT applied to autoimmune diseases, emphasizing current combination therapies and future strategies.

Immune Tolerance for Autoimmune Disease and Cell Transplantation

The undesired destruction of healthy cells, either endogenous or transplanted, by the immune system results in the loss of tissue function or limits strategies to restore tissue function. Current therapies typically involve nonspecific immunosuppression that may prevent the appropriate response to an antigen, thereby decreasing humoral immunity and increasing the risks of patient susceptibility to opportunistic infections, viral reactivation, and neoplasia. The induction of antigen-specific immunological tolerance to block undesired immune responses to self- or allogeneic antigens, while maintaining the integrity of the remaining immune system, has the potential to transform the current treatment of autoimmune disease and serve as a key enabling technology for therapies based on cell transplantation.

Antigen-Specific Binding of Multivalent Soluble Antigen Arrays Induces Receptor Clustering and Impedes B Cell Receptor Mediated Signaling

A pressing need exists for autoimmune disease therapies that act in an antigen-specific manner while avoiding global immunosuppression. Multivalent soluble antigen arrays (SAgAPLP:LABL), designed to induce tolerance to a specific multiple sclerosis autoantigen, consist of a flexible hyaluronic acid (HA) polymer backbone cografted with multiple copies of autoantigen peptide (PLP) and cell adhesion inhibitor peptide (LABL). Previous in vivo studies revealed copresentation of both signals on HA was necessary for therapeutic efficacy. To elucidate therapeutic cellular mechanisms, in vitro studies were performed in a model B cell system to evaluate binding and specificity. Compared to HA and HA arrays containing only grafted PLP or LABL, SAgAPLP:LABL displaying both PLP and LABL exhibited greatly enhanced B cell binding. Furthermore, the binding avidity of SAgAPLP:LABL was primarily driven by the PLP antigen, determined via flow cytometry competitive dissociation studies. Fluorescence microscopy showed SAgAPLP:LABL induced mature receptor clustering that was faster than other HA arrays with only one type of grafted peptide. SAgAPLP:LABL molecules also reduced and inhibited IgM-stimulated signaling as discerned by a calcium flux assay. The molecular mechanisms of enhanced antigen-specific binding, mature receptor clustering, and dampened signaling observed in B cells may contribute to SAgAPLP:LABL therapeutic efficacy.

Molecular Dynamics of Multivalent Soluble Antigen Arrays Support a Two-Signal Co-delivery Mechanism in the Treatment of Experimental Autoimmune Encephalomyelitis

Many current therapies for autoimmune diseases such as multiple sclerosis (MS) result in global immunosuppression, rendering insufficient efficacy with increased risk of adverse side effects. Multivalent soluble antigen arrays, nanomaterials presenting both autoantigen and secondary inhibitory signals on a flexible polymer backbone, are hypothesized to shift the immune response toward selective autoantigenic tolerance to repress autoimmune disease. Two-signal co-delivery of both autoantigen and secondary signal were deemed necessary for therapeutic efficacy against experimental autoimmune encephalomyelitis, a murine model of MS. Dynamic light scattering and in silico molecular dynamics simulations complemented these studies to illuminate the role of two-signal co-delivery in determining therapeutic potential. Physicochemical characteristics such as particle size and molecular affinity for intermolecular interactions and chain entanglement likely facilitated cotransport of two signals to produce efficacy. These findings elucidate potential mechanisms whereby soluble antigen arrays enact their therapeutic effect and help to guide the development of future multivalent antigen-specific immunotherapies.