Overcoming challenges in treating autoimmuntity: Development of tolerogenic immune-modifying nanoparticles

Impact of antigen loading in tolerogenic nanoparticles to mitigate Th2-mediated allergic lung inflammation

Allergic disease is a major global health concern that imposes significant life-altering and economic burdens on affected individuals. However, there is still no cure. Polymer-based nanoparticles (NP) have shown the potential to induce antigen (Ag)-specific immune tolerance in various Th1/17 and Th2-mediated immune disorders including autoimmunity and allergy. Common methods by which Ags are associated with NPs are through surface conjugation or encapsulation. However, these Ag delivery strategies can be associated with several caveats that dampen their effectiveness such as uncontrolled Ag loading, a high Ag burst release, and an increased immune recognition profile. We previously developed Ag-polymer conjugate NPs (acNPs) to overcome those noted limitations, while allowing for controlled delivery of precise quantities of Ag to innate immune cells for Ag-specific CD4 T cell modulation. Here, we utilized ovalbumin (OVA) protein-poly(lactic-co-glycolic acid) (PLGA) conjugate NPs (acNP-OVA) to elucidate the impact of Ag loading on the induction of Th2 tolerance using a prophylactic and therapeutic OVA/ALUM-induced mouse model of allergic lung inflammation (ALI) in comparison to Ag-encapsulated PLGA NPs (NP(Ag)). We demonstrate that acNP-OVA formulations reduced OVA-specific IgE and inhibited Th2 cytokine secretions in an Ag loading-dependent manner when administered prophylactically. Administration of acNP-OVA to pre-sensitized mice did not affect OVA-specific IgE and Th2 cytokines tended to be reduced, however, there was no clear Ag loading dependency. acNP-OVA with medium-to-low Ag loadings were well tolerated, while formulations with high Ag loadings, including NP(Ag) resulted in anaphylaxis. Overall, our results clarify the relationship between Ag loading and Ag-specific IgE and Th2 cytokine responses in a murine model of ALI, which provides insight useful for future design of tolerogenic NP-based immunotherapies.

Lipid-Polymer Hybrid Nanoparticles Utilize B Cells and Dendritic Cells to Elicit Distinct Antigen-Specific CD4+ and CD8+ T Cell Responses

Antigen-presenting cells (APCs) are widely studied for treating immune-mediated diseases, and dendritic cells (DCs) are potent APCs that uptake and present antigens (Ags). However, DCs face several challenges that hinder their clinical translation due to their inability to control Ag dosing and low abundance in peripheral blood. B cells are a potential alternative to DCs, but their poor nonspecific Ag uptake capabilities compromise controllable priming of T cells. Here, we developed phospholipid-conjugated Ags (L-Ags) and lipid-polymer hybrid nanoparticles (L/P-Ag NPs) as delivery platforms to expand the range of accessible APCs for use in T cell priming. These delivery platforms were evaluated using DCs, CD40-activated B cells, and resting B cells to understand the impacts of various Ag delivery mechanisms for generation of Ag-specific T cell responses. L-Ag delivery (termed depoting) of MHC class I- and II-restricted Ags successfully loaded all APC types in a tunable manner and primed both Ag-specific CD8+ and CD4+ T cells, respectively. Incorporating L-Ags and polymer-conjugated Ags (P-Ag) into NPs can direct Ags to different uptake pathways to engineer the dynamics of presentation and shape T cell responses. DCs were capable of processing and presenting Ag delivered from both L- and P-Ag NPs, yet B cells could only utilize Ag delivered from L-Ag NPs, which led to differential cytokine secretion profiles in coculture studies. Altogether, we show that L-Ags and P-Ags can be rationally paired within a single NP to leverage distinct delivery mechanisms to access multiple Ag processing pathways in two APC types, offering a modular delivery platform for engineering Ag-specific immunotherapies.

How Future Pharmacologic Therapies for Celiac Disease Will Complement the Gluten-Free Diet

The only proven treatment for celiac disease is adherence to a strict, lifelong, gluten-free diet. However, complete dietary gluten avoidance is challenging and a substantial number of patients do not respond fully, clinically, or histologically, despite their best efforts. As celiac disease is common and its central pathophysiology is well elucidated, it has become attractive for drug development to address the limitations of dietary treatment. Most efforts address nonresponsive celiac disease, defined as continued symptoms and/or signs of disease activity despite a gluten-free diet, and the more severe forms of refractory celiac disease, types I and II. An increasing spectrum of therapeutic approaches target defined mechanisms in celiac disease pathogenesis and some have advanced to current phase 2 and 3 clinical studies. We discuss these approaches in terms of potential efficiency, practicability, safety, and need, as defined by patients, regulatory authorities, health care providers, and payors.

Engineering nanoparticle therapeutics for food allergy

Food allergy is a growing public health issue among children and adults that can lead to life-threatening anaphylaxis following allergen exposure. The criterion standard for disease management includes food avoidance and emergency epinephrine administration because current allergen-specific immunotherapy treatments are limited by adverse events and unsustained desensitization. A promising approach to remedy these shortcomings is the use of nanoparticle-based therapies that disrupt disease-driving immune mechanisms and induce more sustained tolerogenic immune pathways. The pathophysiology of food allergy includes multifaceted interactions between effector immune cells, including lymphocytes, antigen-presenting cells, mast cells, and basophils, mainly characterized by a TH2 cell response. Regulatory T cells, TH1 cell responses, and suppression of other major allergic effector cells have been found to be major drivers of beneficial outcomes in these nanoparticle therapies. Engineered nanoparticle formulations that have shown efficacy at reducing allergic responses and revealed new mechanisms of tolerance include polymeric-, lipid-, and emulsion-based nanotherapeutics. This review highlights the recent engineering design of these nanoparticles, the mechanisms induced by them, and their future potential therapeutic targets.

Tolerogenic Nano-/Microparticle Vaccines for Immunotherapy

Autoimmune diseases, allergies, transplant rejections, generation of antidrug antibodies, and chronic inflammatory diseases have impacted a large group of people across the globe. Conventional treatments and therapies often use systemic or broad immunosuppression with serious efficacy and safety issues. Tolerogenic vaccines represent a concept that has been extended from their traditional immune-modulating function to induction of antigen-specific tolerance through the generation of regulatory T cells. Without impairing immune homeostasis, tolerogenic vaccines dampen inflammation and induce tolerogenic regulation. However, achieving the desired potency of tolerogenic vaccines as preventive and therapeutic modalities calls for precise manipulation of the immune microenvironment and control over the tolerogenic responses against the autoantigens, allergens, and/or alloantigens. Engineered nano-/microparticles possess desirable design features that can bolster targeted immune regulation and enhance the induction of antigen-specific tolerance. Thus, particle-based tolerogenic vaccines hold great promise in clinical translation for future treatment of aforementioned immune disorders. In this review, we highlight the main strategies to employ particles as exciting tolerogenic vaccines, with a focus on the particles' role in facilitating the induction of antigen-specific tolerance. We describe the particle design features that facilitate their usage and discuss the challenges and opportunities for designing next-generation particle-based tolerogenic vaccines with robust efficacy to promote antigen-specific tolerance for immunotherapy.

Nanomedicine-mediated drug delivery for potential treatment of inflammatory bowel disease: a narrative review

Background & aims: Inflammatory bowel disease (IBD) is a condition characterized by chronic inflammation of the gastrointestinal tract, manifesting as either Crohn's disease (CrD) or ulcerative colitis (UC). Current treatment options for CrD and UC primarily focus on symptom management. In recent years, advancements in nanotechnology have increased the clinical applicability of nanoparticles (NPs) in treating IBD. This review explores the current research on NP-mediated drug-delivery systems for IBD treatment and assesses its advantages and limitations. Results: The authors examine diverse nanomedicine applications for IBD and address the current challenges and prospects in the field to advance nanomediated therapies in the future. Conclusion: Innovative NP-based treatment strategies promise a reliable and effective approach to IBD management.

Development of protein-polymer conjugate nanoparticles for modulation of dendritic cell phenotype and antigen-specific CD4 T cell responses

Polymeric nanoparticles (NPs) comprised of poly(lactic-co-glycolic acid) (PLGA) have found success in modulating antigen (Ag)-specific T cell responses for the treatment multiple immunological diseases. Common methods by which Ags are associated with NPs are through encapsulation and surface conjugation; however, these methods suffer from several limitations, including uncontrolled Ag loading, burst release, and potential immune recognition. To overcome these limitations and study the relationship between NP design parameters and modulation of innate and Ag-specific adaptive immune cell responses, we developed ovalbumin (OVA) protein-PLGA bioconjugate NPs (acNP-OVA). OVA was first modified by conjugation with multiple PLGA polymers to synthesize OVA-PLGA conjugates, followed by precise combination with unmodified PLGA to form acNP-OVA with well-defined Ag loadings, reduced burst release, and reduced antibody recognition. Expression of MHC II, CD80, and CD86 on bone marrow-derived dendritic cells (BMDCs) increased as a function of acNP-OVA Ag loading. NanoString studies using BMDCs showed that PLGA NPs generally induced anti-inflammatory gene expression profiles independent of the Ag delivery method, where S100a9, Sell, and Ppbp were most significantly reduced. Co-culture studies using acNP-OVA-treated BMDCs and OT-II CD4+ T cells revealed that Ag-specific T cell activation, expansion, and differentiation were dependent on Ag loading and formulation parameters. CD25 expression was induced using acNP-OVA with the lowest Ag loading; however, the induction of robust CD4+ T cell proliferative and cytokine responses required acNP-OVA formulations with higher Ag loading, which was supported using a regulatory T cell (Treg) induction assay. The distinct differences in Ag loading required to achieve various T cell responses supported the concept of an Ag loading threshold for Ag-specific immunotherapy. We anticipate this work will help guide NP designs and aid in the future development of NP-based immunotherapies for Ag-specific immunomodulation.

Biosynthesis of Co3O4 nanomedicine by using Mollugo oppositifolia L. aqueous leaf extract and its antimicrobial, mosquito larvicidal activities

Nanotechnology is a relatively revolutionary area that generates day-to-day advancement. It makes a significant impact on our daily life. For example, in parasitology, catalysis and cosmetics, nanoparticles possess distinctive possessions that make it possible for them in a broad range of areas. We utilized Mollugo oppositifolia L. aqueous leaf extract assisted chemical reduction method to synthesize Co₃O₄ nanoparticles. Biosynthesized Co₃O₄ Nps were confirmed via UV-Vis spectroscopy, scanning electron microscope, X-ray diffraction, EDX, Fourier-transform infrared, and HR-TEM analysis. The crystallite size from XRD studies revealed around 22.7 nm. The biosynthesized Co₃O₄ nanoparticle was further assessed for mosquito larvicidal activity against south-urban mosquito larvae Culex quinquefasciatus, and antimicrobial activities. The synthesized Co₃O₄ particle (2) displayed significant larvicidal activity towards mosquito larvae Culex quinquefasciatus with the LD₅₀ value of 34.96 µg/mL than aqueous plant extract (1) and control Permethrin with the LD₅₀ value of 82.41 and 72.44 µg/mL. When compared to the standard antibacterial treatment, Ciprofloxacin, the Co₃O₄ nanoparticle (2) produced demonstrates significantly enhanced antibacterial action against the pathogens E. coli and B. cereus. The MIC for Co₃O₄ nanoparticles 2 against C. albicans was under 1 μg/mL, which was much lower than the MIC for the control drug, clotrimale, which was 2 µg per milliliter. Co₃O₄ nanoparticles 2, with a MIC of 2 μg/mL, has much higher antifungal activity than clotrimale, whose MIC is 4 μg/mL, against M. audouinii.

Roadmap for understanding mechanisms on how Epstein-Barr virus triggers multiple sclerosis and for translating these discoveries in clinical trials

Here, we offer a roadmap for what might be studied next in understanding how EBV triggers MS. We focus on two areas: The first area concerns the molecular mechanisms underlying how clonal antibody in the CSF emanates in widespread molecular mimicry to key antigens in the nervous system including GlialCAM, a protein associated with chloride channels. A second and equally high priority in the roadmap concerns various therapeutic approaches that are related to blocking the mechanisms whereby EBV triggers MS. Therapies deserving of attention include clinical trials with antivirals and the development of 'inverse' vaccines based on nucleic acid technologies to control or to eradicate the consequences of EBV infection. High enthusiasm is given to continuation of ongoing clinical trials of cellular adoptive therapy to attack EBV-infected cells. Clinical trials of vaccines to EBV are another area deserving attention. These suggested topics involving research on mechanism, and the design, implementation and performance of well-designed trials are not intended to be an exhaustive list. We have splendid tools available to our community of medical scientists to tackle how EBV triggers MS and then to perhaps change the world with new therapies to potentially eradicate MS, as we have done with nearly complete success for poliomyelitis.

Nanoparticle dose and antigen loading attenuate antigen-specific T-cell responses

Immune-mediated hypersensitivities such as autoimmunity, allergy, and allogeneic graft rejection are treated with therapeutics that suppress the immune system, and the lack of specificity is associated with significant side effects. The delivery of disease-relevant antigens (Ags) by carrier systems such as poly(lactide-co-glycolide) nanoparticles (PLG-Ag) and carbodiimide (ECDI)-fixed splenocytes (SP-Ag) has demonstrated Ag-specific tolerance induction in model systems of these diseases. Despite therapeutic outcomes by both platforms, tolerance is conferred with different efficacy. This investigation evaluated Ag loading and total particle dose of PLG-Ag on Ag presentation in a coculture system of dendritic cells (DCs) and Ag-restricted T cells, with SP-Ag employed as a control. CD25 expression was observed in nearly all T cells even at low concentrations of PLG-Ag, indicating efficient presentation of Ag by dendritic cells. However, the secretion of IL-2, Th1, and Th2 cytokines (IFNγ and IL-4, respectively) varied depending on PLG-Ag concentration and Ag loading. Concentration escalation of soluble Ag resulted in an increase in IL-2 and IFNγ and a decrease in IL-4. Treatment with PLG-Ag followed a similar trend but with lower levels of IL-2 and IFNγ secreted. Transcriptional Activity CEll ARrays (TRACER) were employed to measure the real-time transcription factor (TF) activity in Ag-presenting DCs. The kinetics and magnitude of TF activity was dependent on the Ag delivery method, concentration, and Ag loading. Ag positively regulated IRF1 activity and, as carriers, NPs and ECDI-treated SP negatively regulated this signaling. The effect of Ag loading and dose on tolerance induction were corroborated in vivo using the delayed-type hypersensitivity (DTH) and experimental autoimmune encephalomyelitis (EAE) mouse models where a threshold of 8 μg/mg Ag loading and 0.5 mg PLG-Ag dose were required for tolerance. Together, the effect of Ag loading and dosing on in vitro and in vivo immune regulation provide useful insights for translating Ag-carrier systems for the clinical treatment of immune disorders.

Design and characterization of lipid nanocarriers for oral delivery of immunotherapeutic peptides

The use of therapeutic proteins and peptides is of great interest for the treatment of many diseases, and advances in nanotechnology offer a path toward their stable delivery via preferred routes of administration. In this study, we sought to design and formulate a nanostructured lipid carrier (NLC) containing a nominal antigen (insulin peptide) for oral delivery. We utilized the design of experiments (DOE) statistical method to determine the dependencies of formulation variables on physicochemical particle characteristics including particle size, polydispersity (PDI), melting point, and latent heat of melting. The particles were determined to be non-toxic in vitro, readily taken up by primary immune cells, and found to accumulate in regional lymph nodes following oral administration. We believe that this platform technology could be broadly useful for the treatment of autoimmune diseases by supporting the development of oral delivery-based antigen specific immunotherapies.

A predictive mechanistic model of drug release from surface eroding polymeric nanoparticles

Effective drug delivery requires ample dosing at the target tissue while minimizing negative side effects. Drug delivery vehicles such as polymeric nanoparticles (NPs) are often employed to accomplish this challenge. In this work, drug release of numerous drugs from surface eroding polymeric NPs was evaluated in vitro in physiologically relevant pH 5 and neutral buffers. NPs were loaded with paclitaxel, rapamycin, resiquimod, or doxorubicin and made from an FDA approved polyanhydride or from acetalated dextran (Ace-DEX), which has tunable degradation rates based on cyclic acetal coverage (CAC). By varying encapsulate, pH condition, and polymer, a range of distinct drug release profiles were achieved. To model the obtained drug release curves, a mechanistic mathematical model was constructed based on drug diffusion and polymer degradation. The resulting diffusion-erosion model accurately described drug release from the variety of surface eroding NPs. For drug release from varied CAC Ace-DEX NPs, the goodness of fit of the developed diffusion-erosion model was compared to several conventional drug release models. The diffusion-erosion model maintained optimal fit compared to conventional models across a range of conditions. Machine learning was then employed to estimate effective diffusion coefficients for the diffusion-erosion model, resulting in accurate prediction of in vitro release of dexamethasone and 3'3'-cyclic guanosine monophosphate-adenosine monophosphate from Ace-DEX NPs. This predictive modeling has potential to aid in the design of future Ace-DEX formulations where optimized drug release kinetics can lead to a desired therapeutic effect.

Repurposing the cardiac glycoside digoxin to stimulate myelin regeneration in chemically-induced and immune-mediated mouse models of multiple sclerosis

Multiple sclerosis (MS) is a central nervous system (CNS) autoimmune disease characterized by inflammation, demyelination, and neurodegeneration. The ideal MS therapy would both specifically inhibit the underlying autoimmune response and promote repair/regeneration of myelin as well as maintenance of axonal integrity. Currently approved MS therapies consist of non-specific immunosuppressive molecules/antibodies which block activation or CNS homing of autoreactive T cells, but there are no approved therapies for stimulation of remyelination nor maintenance of axonal integrity. In an effort to repurpose an FDA-approved medication for myelin repair, we chose to examine the effectiveness of digoxin, a cardiac glycoside (Na+ /K+ ATPase inhibitor), originally identified as pro-myelinating in an in vitro screen. We found that digoxin regulated multiple genes in oligodendrocyte progenitor cells (OPCs) essential for oligodendrocyte (OL) differentiation in vitro, promoted OL differentiation both in vitro and in vivo in female naïve C57BL/6J (B6) mice, and stimulated recovery of myelinated axons in B6 mice following demyelination in the corpus callosum induced by cuprizone and spinal cord demyelination induced by lysophosphatidylcholine (LPC), respectively. More relevant to treatment of MS, we show that digoxin treatment of mice with established MOG35-55 -induced Th1/Th17-mediated chronic EAE combined with tolerance induced by the i.v. infusion of biodegradable poly(lactide-co-glycolide) nanoparticles coupled with MOG35-55 (PLG-MOG35-55 ) completely ameliorated clinical disease symptoms and stimulated recovery of OL lineage cell numbers. These findings provide critical pre-clinical evidence supporting future clinical trials of myelin-specific tolerance with myelin repair/regeneration drugs, such as digoxin, in MS patients.

Development of PLGA Nanoparticles with a Glycosylated Myelin Oligodendrocyte Glycoprotein Epitope (MOG35-55) against Experimental Autoimmune Encephalomyelitis (EAE)

Multiple sclerosis (MS) is one of the most common neurodegenerative diseases in young adults, with early clinical symptoms seen in the central nervous system (CNS) myelin sheaths due to an attack caused by the patient's immune system. Activation of the immune system is mediated by the induction of an antigen-specific immune response involving the interaction of multiple T-cell types with antigen-presenting cells (APCs), such as dendritic cells (DCs). Antigen-specific therapeutic approaches focus on immune cells and autoantigens involved in the onset of disease symptoms, which are the main components of myelin proteins. The ability of such therapeutics to bind strongly to DCs could lead to immune system tolerance to the disease. Many modern approaches are based on peptide-based research, as, in recent years, they have been of particular interest in the development of new pharmaceuticals. The characteristics of peptides, such as short lifespan in the body and rapid hydrolysis, can be overcome by their entrapment in nanospheres, providing better pharmacokinetics and bioavailability. The present study describes the development of polymeric nanoparticles with encapsulated myelin peptide analogues involved in the development of MS, along with their biological evaluation as inhibitors of MS development and progression. In particular, particles of poly(lactic-co-glycolic) acid (PLGA) loaded with peptides based on mouse/rat (rMOG) epitope 35-55 of myelin oligodendrocyte glycoprotein (MOG) conjugated with saccharide residues were developed. More specifically, the MOG_35-55 peptide was conjugated with glucosamine to promote the interaction with mannose receptors (MRs) expressed by DCs. In addition, a study of slow release (dissolution) and quantification on both initially encapsulated peptide and daily release in saline in vitro was performed, followed by an evaluation of in vivo activity of the formulation on mouse experimental autoimmune encephalomyelitis (EAE), an animal model of MS, using both prophylactic and therapeutic protocols. Our results showed that the therapeutic protocol was effective in reducing EAE clinical scores and inflammation of the central nervous system and could be an alternative and promising approach against MS inducing tolerance against the disease.

Tolerogenic Immune-Modifying Nanoparticles Encapsulating Multiple Recombinant Pancreatic β Cell Proteins Prevent Onset and Progression of Type 1 Diabetes in Nonobese Diabetic Mice

Type 1 diabetes (T1D) is an autoimmune disease characterized by T and B cell responses to proteins expressed by insulin-producing pancreatic β cells, inflammatory lesions within islets (insulitis), and β cell loss. We previously showed that Ag-specific tolerance targeting single β cell protein epitopes is effective in preventing T1D induced by transfer of monospecific diabetogenic CD4 and CD8 transgenic T cells to NOD.scid mice. However, tolerance induction to individual diabetogenic proteins, for example, GAD65 (glutamic acid decarboxylase 65) or insulin, has failed to ameliorate T1D both in wild-type NOD mice and in the clinic. Initiation and progression of T1D is likely due to activation of T cells specific for multiple diabetogenic epitopes. To test this hypothesis, recombinant insulin, GAD65, and chromogranin A proteins were encapsulated within poly(d,l-lactic-co-glycolic acid) (PLGA) nanoparticles (COUR CNPs) to assess regulatory T cell induction, inhibition of Ag-specific T cell responses, and blockade of T1D induction/progression in NOD mice. Whereas treatment of NOD mice with CNPs containing a single protein inhibited the corresponding Ag-specific T cell response, inhibition of overt T1D development only occurred when all three diabetogenic proteins were included within the CNPs (CNP-T1D). Blockade of T1D following CNP-T1D tolerization was characterized by regulatory T cell induction and a significant decrease in both peri-insulitis and immune cell infiltration into pancreatic islets. As we have recently published that CNP treatment is both safe and induced Ag-specific tolerance in a phase 1/2a celiac disease clinical trial, Ag-specific tolerance induced by nanoparticles encapsulating multiple diabetogenic proteins is a promising approach to T1D treatment.

Targeting Fibronectin to Overcome Remyelination Failure in Multiple Sclerosis: The Need for Brain- and Lesion-Targeted Drug Delivery

Multiple sclerosis (MS) is a neuroinflammatory and neurodegenerative disease with unknown etiology that can be characterized by the presence of demyelinated lesions. Prevailing treatment protocols in MS rely on the modulation of the inflammatory process but do not impact disease progression. Remyelination is an essential factor for both axonal survival and functional neurological recovery but is often insufficient. The extracellular matrix protein fibronectin contributes to the inhibitory environment created in MS lesions and likely plays a causative role in remyelination failure. The presence of the blood-brain barrier (BBB) hinders the delivery of remyelination therapeutics to lesions. Therefore, therapeutic interventions to normalize the pathogenic MS lesion environment need to be able to cross the BBB. In this review, we outline the multifaceted roles of fibronectin in MS pathogenesis and discuss promising therapeutic targets and agents to overcome fibronectin-mediated inhibition of remyelination. In addition, to pave the way for clinical use, we reflect on opportunities to deliver MS therapeutics to lesions through the utilization of nanomedicine and discuss strategies to deliver fibronectin-directed therapeutics across the BBB. The use of well-designed nanocarriers with appropriate surface functionalization to cross the BBB and target the lesion sites is recommended.

Nanoparticle-Based Drug Delivery Systems for Induction of Tolerance and Treatment of Autoimmune Diseases

Autoimmune disease is a chronic inflammatory disease caused by disorders of immune regulation. Antigen-specific immunotherapy has the potential to inhibit the autoreactivity of inflammatory T cells and induce antigen-specific immune suppression without impairing normal immune function, offering an ideal strategy for autoimmune disease treatment. Tolerogenic dendritic cells (Tol DCs) with immunoregulatory functions play important roles in inducing immune tolerance. However, the effective generation of tolerogenic DCs in vivo remains a great challenge. The application of nanoparticle-based drug delivery systems in autoimmune disease treatment can increase the efficiency of inducing antigen-specific tolerance in vivo. In this review, we discuss multiple nanoparticles, with a focus on their potential in treatment of autoimmune diseases. We also discuss how the physical properties of nanoparticles influence their therapeutic efficacy.

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.

Recent advancements in nanoparticle-mediated approaches for restoration of multiple sclerosis

Multiple Sclerosis (MS) is an autoimmune disease with complicated immunopathology which necessitates considering multifactorial aspects for its management. Nano-sized pharmaceutical carriers named nanoparticles (NPs) can support impressive management of disease not only in early detection and prognosis level but also in a therapeutic manner. The most prominent initiator of MS is the domination of cellular immunity to humoral immunity and increment of inflammatory cytokines. The administration of several platforms of NPs for MS management holds great promise so far. The efforts for MS management through in vitro and in vivo (experimental animal models) evaluations, pave a new way to a highly efficient therapeutic means and aiding its translation to the clinic in the near future.

Masked Delivery of Allergen in Nanoparticles Safely Attenuates Anaphylactic Response in Murine Models of Peanut Allergy

Food allergy is a growing health concern worldwide. Current allergen-specific immunotherapy (AIT) approaches require frequent dosing over extended periods of time and may induce anaphylaxis due to allergen-effector cell interactions. A critical need remains to develop novel approaches that refine AIT for the treatment of food allergies. Previous studies show that poly(lactide-co-glycolide) (PLG) nanoscale particles (NP) effectively suppress Th1- and Th17-driven immune pathologies. However, their ability to suppress the distinct Th2-polarized immune responses driving food allergy are unknown. Herein, we describe the safety and efficacy of NPs containing encapsulated peanut allergen in desensitizing murine models of peanut allergy. Peanut extract encapsulation allowed for the safe intravenous delivery of allergen relative to non-encapsulated approaches. Application of 2–3 doses, without the need for dose escalation, was sufficient to achieve prophylactic and therapeutic efficacy, which correlated with suppression of Th2-mediated disease and reduced mast cell degranulation. Efficacy was associated with strong reductions in a broad panel of Th1, Th2, and Th17 cytokines. These results demonstrate the ability of PLG NPs to suppress allergen-specific immune responses to induce a more tolerogenic phenotype, conferring protection from intragastric allergen challenge. These promising studies represent a step forward in the development of improved immunotherapies for food allergy.

Antigen-specific nanomedicines for the treatment of autoimmune disease: target cell types, mechanisms and outcomes

Nanoparticle (NP)-based delivery of autoantigenic ligands represents a promising approach to modulate autoimmune responses in vivo. Over the last 15 years, a growing number of compounds have been tested in animal models of various experimental and/or spontaneous autoimmune diseases. Based on the underlying design principles and mechanistic underpinnings, these compounds can be categorized into three broad groups: NPs (or microparticles, MPs) as vehicles for targeted delivery of antigens to tolerogenic antigen-presenting cells (APCs); NPs as scaffolds for targeted delivery of both antigen and immunomodulatory molecules to professional APCs; and NPs as multimerization platforms for direct cognate T-cell targeting via recombinant peptide-major histocompatibility complex molecules (pMHCs). These various compounds operate through different mechanisms of action, eliciting pharmacodynamic effects that range from antigen-specific clonal deletion to induction of comprehensive, yet disease-specific, bystander immunoregulation. Here, we review the outcomes of the various approaches tested to date and discuss their translational significance in the context of mode of action vis-à-vis immunologically complex human autoimmune diseases.

Can Immune Tolerance Be Re-established in Neuromyelitis Optica?

Neuromyelitis optica (NMO) is a chronic inflammatory disease of the central nervous system that primarily affects the optic nerves and spinal cord of patients, and in some instances their brainstem, diencephalon or cerebrum as spectrum disorders (NMOSD). Clinical and basic science knowledge of NMO has dramatically increased over the last two decades and it has changed the perception of the disease as being inevitably disabling or fatal. Nonetheless, there is still no cure for NMO and all the disease-modifying therapies (DMTs) are only partially effective. Furthermore, DMTs are not disease- or antigen-specific and alter all immune responses including those protective against infections and cancer and are often associated with significant adverse reactions. In this review, we discuss the pathogenic mechanisms of NMO as they pertain to its DMTs and immune tolerance. We also examine novel research therapeutic strategies focused on induction of antigen-specific immune tolerance by administrating tolerogenic immune-modifying nanoparticles (TIMP). Development and implementation of immune tolerance-based therapies in NMO is likely to be an important step toward improving the treatment outcomes of the disease. The antigen-specificity of these therapies will likely ameliorate the disease safely and effectively, and will also eliminate the clinical challenges associated with chronic immunosuppressive therapies.

Immunomodulatory and immunoregulatory nanomedicines for autoimmunity

Autoimmune diseases, caused by cellularly and molecularly complex immune responses against self-antigens, are largely treated with broad-acting, non-disease-specific anti-inflammatory drugs. These compounds can attenuate autoimmune inflammation, but tend to impair normal immunity against infection and cancer, cannot restore normal immune homeostasis and are not curative. Nanoparticle (NP)- and microparticle (MP)-based delivery of immunotherapeutic agents affords a unique opportunity to not only increase the specificity and potency of broad-acting immunomodulators, but also to elicit the formation of organ-specific immunoregulatory cell networks capable of inducing bystander immunoregulation. Here, we review the various NP/MP-based strategies that have so far been tested in models of experimental and/or spontaneous autoimmunity, with a focus on mechanisms of action.

Microfluidic-Generated Immunomodulatory Nanoparticles and Formulation-Dependent Effects on Lipopolysaccharide-Induced Macrophage Inflammation

Nanoparticles (NPs) have emerged as a highly useful and clinically translatable drug delivery platform for vast therapeutic payloads. Through the precise tuning of their physicochemical properties, NPs can be engineered to exhibit controlled drug release properties, enhanced circulation times, improved cellular uptake and targeting, and reduced toxicity profiles. Conventional bulk methods for the production of polymeric NPs suffer from the ability to control their size and polydispersity, batch-to-batch variability, significant preparation times, and low recovery. Here, we describe the development and optimization of a high-throughput microfluidic method to produce cargo-less immunomodulatory nanoparticles (iNPs) and their formulation-dependent anti-inflammatory properties for the modulation of lipopolysaccharide (LPS)-induced macrophage responses. Using poly(lactic acid) (PLA) as the core-forming polymer, a rapid and tunable microfluidic hydrodynamic flow-focusing method was developed and optimized to systematically evaluate the role of polymer and surfactant concentration, surfactant chemistry, and flow rate ratio (FRR) on the formation of iNPs. A set of iNPs with 6 different surface chemistries and 2 FRRs was then prepared to evaluate their inherent anti-inflammatory effects using bone marrow-derived macrophages stimulated with the Toll-like receptor 4 agonist, LPS. Finally, a lyophilization study was performed using various cryoprotectants and combinations to identify preferable conditions for iNP storage. Overall, we demonstrate a highly controlled and reproducible method for the formulation of iNPs using microfluidics and their formulation-dependent inherent anti-inflammatory immunomodulatory properties, which represents a potentially promising strategy for the management of inflammation.

The impact of nanocarriers in the induction of antigen-specific immunotolerance in autoimmune diseases

Immunotolerance induction in an antigen-specific manner is the long-term goal of immunotherapy to treat autoimmune diseases. Nanocarriers (NCs) can be designed as a new generation of delivery systems to modulate the immune responses through targeted delivery of antigens and immunomodulators to antigen presenting cells (APCs). In this manuscript, several formulation factors in the preparation of NCs which affect their uptake using APCs and generation of tolerance have been reviewed. The physicochemical properties and composition of NCs have been shown to play essential roles in achieving the desired immunological outcome. Also, targeting of dendritic cells and macrophages as APCs and direct targeting of the autoreactive lymphocytes have been presented as two main ways for induction of antigen-specific tolerance by these tolerogenic nanocarriers (tNCs). These particles herald a promising approach to treat or even prevent unwanted immune reactions in humans specifically.

Immunomodulatory Nanoparticles Mitigate Macrophage Inflammation via Inhibition of PAMP Interactions and Lactate-Mediated Functional Reprogramming of NF-κB and p38 MAPK

Inflammation is a key homeostatic process involved in the body's response to a multitude of disease states including infection, autoimmune disorders, cancer, and other chronic conditions. When the initiating event is poorly controlled, severe inflammation and globally dysregulated immune responses can occur. To address the lack of therapies that efficaciously address the multiple aspects of the dysregulated immune response, we developed cargo-less immunomodulatory nanoparticles (iNPs) comprised of poly(lactic acid) (PLA) with either poly(vinyl alcohol) (PVA) or poly(ethylene-alt-maleic acid) (PEMA) as stabilizing surfactants and investigated the mechanisms by which they exert their inherent anti-inflammatory effects. We identified that iNPs leverage a multimodal mechanism of action by physically interfering with the interactions between pathogen-associated molecular patterns (PAMPs) and bone marrow-derived macrophages (BMMΦs). Additionally, we showed that iNPs mitigate proinflammatory cytokine secretions induced by LPS via a time- and composition-dependent abrogation of NF-κB p65 and p38 MAPK activation. Lastly, inhibition studies were performed to establish the role of a pH-sensing G-protein-coupled receptor, GPR68, on contributing to the activity of iNPs. These data provide evidence for the multimodal mechanism of action of iNPs and establish their potential use as a novel therapeutic for the treatment of severe inflammation.

Biologia Futura: Emerging antigen-specific therapies for autoimmune diseases

Autoimmune diseases are caused by breaking the central and/or peripheral tolerance against self, leading to uncontrolled immune response to autoantigens. The incidences of autoimmune diseases have increased significantly worldwide over the last decades; nearly 5% of the world's population is affected. The current treatments aim to reduce pain and inflammation to prevent organ damage and have a general immunosuppressive effect, but they cannot cure the disease. There is a huge unmet need for autoantigen-specific therapy, without affecting the immune response against pathogens. This goal can be achieved by targeting autoantigen-specific T or B cells and by restoring self-tolerance by inducing tolerogenic antigen-presenting cells (APC) and the development of regulatory T (Treg) cells, for example, by using autoantigenic peptides bound to nanoparticles. Transferring in vitro manipulated autologous tolerogenic APC or autologous autoantigen-specific Treg cells to patients is the promising approach to develop cellular therapeutics. Most recently, chimeric autoantibody receptor T cells have been designed to specifically deplete autoreactive B cells. Limitations of these novel autoantigen-specific therapies will also be discussed.

Prevention of EAE by tolerogenic vaccination with PEGylated antigenic peptides

BACKGROUND

Therapeutic treatment options for chronic autoimmune disorders such as multiple sclerosis (MS) rely largely on the use of non-specific immunosuppressive drugs, which are not able to cure the disease. Presently, approaches to induce antigen-specific tolerance as a therapeutic approach; for example, by peptide-based tolerogenic 'inverse' vaccines have regained great interest. We have previously shown that coupling of peptides to carriers can enhance their capacity to induce regulatory T cells in vivo.

METHOD

In this present study, we investigated whether the tolerogenic potential of immunodominant myelin T-cell epitopes can be improved by conjugation to the synthetic carrier polyethylene glycol (PEG) in an experimental autoimmune encephalomyelitis (EAE) mouse model for chronic MS (MOG C57BL/6).

RESULTS

Preventive administration of the PEGylated antigenic peptide could strongly suppress the development of EAE, accompanied by reduced immune cell infiltration in the central nervous system (CNS). Depletion of regulatory T cells (Tregs) abrogated the protective effect indicating that Tregs play a crucial role in induction of antigen-specific tolerance in EAE. Treatment during the acute phase of disease was safe and did not induce immune activation. However, treatment at the peak of disease did not affect the disease course, suggesting that either induction of Tregs does not occur in the highly inflamed situation, or that the immune system is refractory to regulation in this condition.

CONCLUSION

PEGylation of antigenic peptides is an effective and feasible strategy to improve tolerogenic (Treg-inducing) peptide-based vaccines, but application for immunotherapy of overt disease might require modifications or combination therapies that simultaneously suppress effector mechanisms.

Oligodendrocyte-derived extracellular vesicles as antigen-specific therapy for autoimmune neuroinflammation in mice

Autoimmune diseases such as multiple sclerosis (MS) develop because of failed peripheral immune tolerance for a specific self-antigen (Ag). Numerous approaches for Ag-specific suppression of autoimmune neuroinflammation have been proven effective in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. One such approach is intravenous tolerance induction by injecting a myelin Ag used for triggering EAE. However, the translation of this and similar experimental strategies into therapy for MS has been hampered by uncertainty regarding relevant myelin Ags in MS patients. To address this issue, we developed a therapeutic strategy that relies on oligodendrocyte (Ol)-derived extracellular vesicles (Ol-EVs), which naturally contain multiple myelin Ags. Intravenous Ol-EV injection reduced disease pathophysiology in a myelin Ag-dependent manner, both prophylactically and therapeutically, in several EAE models. The treatment was safe and restored immune tolerance by inducing immunosuppressive monocytes and apoptosis of autoreactive CD4⁺ T cells. Furthermore, we showed that human Ols also released EVs containing most relevant myelin Ags, providing a basis for their use in MS therapy. These findings introduce an approach for suppressing central nervous system (CNS) autoimmunity in a myelin Ag-specific manner, without the need to identify the target Ag.

Clinical Management of Primary Biliary Cholangitis-Strategies and Evolving Trends

PBC is a chronic progressive autoimmune disorder involving the destruction of intrahepatic small bile ducts, cholestasis, fibrosis, and ultimately cirrhosis if left untreated. It is largely driven by the autoimmune response, but bile acids and the intestinal microbiota are implicated in disease progression as well. The only drugs licensed for PBC are UDCA and OCA. UDCA as a first-line and OCA as a second-line therapy are safe and effective, but the lack of response in a significant portion of patients and inadequate control of symptoms such as fatigue and pruritus remain as concerns. Liver transplantation is an end-stage therapy for many patients refractory to UDCA, which gives excellent survival rates but also moderate to high recurrence rates. The limited options for FDA-approved PBC therapies necessitate the development of alternative approaches. Currently, a wide variety of experimental drugs exist targeting immunological and physiological aspects of PBC to suppress inflammation. Immunological therapies include drugs targeting immune molecules in the B cell and T cell response, and specific cytokines and chemokines implicated in inflammation. Drugs targeting bile acids are also noteworthy as bile acids can perpetuate hepatic inflammation and lead to fibrosis over time. These include FXR agonists, ASBT inhibitors, and PPAR agonists such as bezafibrate and fenofibrate. Nonetheless, many of these drugs can only delay disease progression and fail to enhance patients' quality of life. Nanomedicine shows great potential for treatment of autoimmune diseases, as it provides a new approach that focuses on tolerance induction rather than immunosuppression. Tolerogenic nanoparticles carrying immune-modifying agents can be engineered to safely and effectively target the antigen-specific immune response in autoimmune diseases. These may work well with PBC especially, given the anatomical features and immunological specificity of the disease. Nanobiological therapy is thus an area of highly promising research for future treatment of PBC.

Recent progress in targeted delivery vectors based on biomimetic nanoparticles

Over the past decades, great interest has been given to biomimetic nanoparticles (BNPs) since the rise of targeted drug delivery systems and biomimetic nanotechnology. Biological vectors including cell membranes, extracellular vesicles (EVs), and viruses are considered promising candidates for targeted delivery owing to their biocompatibility and biodegradability. BNPs, the integration of biological vectors and functional agents, are anticipated to load cargos or camouflage synthetic nanoparticles to achieve targeted delivery. Despite their excellent intrinsic properties, natural vectors are deliberately modified to endow multiple functions such as good permeability, improved loading capability, and high specificity. Through structural modification and transformation of the vectors, they are pervasively utilized as more effective vehicles that can deliver contrast agents, chemotherapy drugs, nucleic acids, and genes to target sites for refractory disease therapy. This review summarizes recent advances in targeted delivery vectors based on cell membranes, EVs, and viruses, highlighting the potential applications of BNPs in the fields of biomedical imaging and therapy industry, as well as discussing the possibility of clinical translation and exploitation trend of these BNPs.

Intestinal Microbiota in Common Chronic Inflammatory Disorders Affecting Children

The incidence and prevalence rate of chronic inflammatory disorders is on the rise in the pediatric population. Recent research indicates the crucial role of interactions between the altered intestinal microbiome and the immune system in the pathogenesis of several chronic inflammatory disorders in children, such as inflammatory bowel disease (IBD) and autoimmune diseases, such as type 1 diabetes mellitus (T1DM) and celiac disease (CeD). Here, we review recent knowledge concerning the pathogenic mechanisms underlying these disorders, and summarize the facts suggesting that the initiation and progression of IBD, T1DM, and CeD can be partially attributed to disturbances in the patterns of composition and abundance of the gut microbiota. The standard available therapies for chronic inflammatory disorders in children largely aim to treat symptoms. Although constant efforts are being made to maximize the quality of life for children in the long-term, sustained improvements are still difficult to achieve. Additional challenges are the changing physiology associated with growth and development of children, a population that is particularly susceptible to medication-related adverse effects. In this review, we explore new promising therapeutic approaches aimed at modulation of either gut microbiota or the activity of the immune system to induce a long-lasting remission of chronic inflammatory disorders. Recent preclinical studies and clinical trials have evaluated new approaches, for instance the adoptive transfer of immune cells, with genetically engineered regulatory T cells expressing antigen-specific chimeric antigen receptors. These approaches have revolutionized cancer treatments and have the potential for the protection of high-risk children from developing autoimmune diseases and effective management of inflammatory disorders. The review also focuses on the findings of studies that indicate that the responses to a variety of immunotherapies can be enhanced by strategic manipulation of gut microbiota, thus emphasizing on the importance of proper interaction between the gut microbiota and immune system for sustained health benefits and improvement of the quality of life of pediatric patients.

Novel approaches for vaccine development

Vaccines are critical tools for maintaining global health. Traditional vaccine technologies have been used across a wide range of bacterial and viral pathogens, yet there are a number of examples where they have not been successful, such as for persistent infections, rapidly evolving pathogens with high sequence variability, complex viral antigens, and emerging pathogens. Novel technologies such as nucleic acid and viral vector vaccines offer the potential to revolutionize vaccine development as they are well-suited to address existing technology limitations. In this review, we discuss the current state of RNA vaccines, recombinant adenovirus vector-based vaccines, and advances from biomaterials and engineering that address these important public health challenges.

Nanomedicine for Gene Delivery and Drug Repurposing in the Treatment of Muscular Dystrophies

Muscular Dystrophies (MDs) are a group of rare inherited genetic muscular pathologies encompassing a variety of clinical phenotypes, gene mutations and mechanisms of disease. MDs undergo progressive skeletal muscle degeneration causing severe health problems that lead to poor life quality, disability and premature death. There are no available therapies to counteract the causes of these diseases and conventional treatments are administered only to mitigate symptoms. Recent understanding on the pathogenetic mechanisms allowed the development of novel therapeutic strategies based on gene therapy, genome editing CRISPR/Cas9 and drug repurposing approaches. Despite the therapeutic potential of these treatments, once the actives are administered, their instability, susceptibility to degradation and toxicity limit their applications. In this frame, the design of delivery strategies based on nanomedicines holds great promise for MD treatments. This review focuses on nanomedicine approaches able to encapsulate therapeutic agents such as small chemical molecules and oligonucleotides to target the most common MDs such as Duchenne Muscular Dystrophy and the Myotonic Dystrophies. The challenge related to in vitro and in vivo testing of nanosystems in appropriate animal models is also addressed. Finally, the most promising nanomedicine-based strategies are highlighted and a critical view in future developments of nanomedicine for neuromuscular diseases is provided.

Nanoparticle-mediated targeting of autoantigen peptide to cross-presenting liver sinusoidal endothelial cells protects from CD8 T-cell-driven autoimmune cholangitis

Autoimmune diseases are caused by adaptive immune responses to self‐antigens. The development of antigen‐specific therapies that suppress disease‐related, but not unrelated immune responses in general, is an important goal of biomedical research. We have previously shown that delivery of myelin peptides to liver sinusoidal endothelial cells (LSECs) using LSEC‐targeting nanoparticles provides effective protection from CD4 T‐cell‐driven autoimmune encephalomyelitis. Here, we investigated whether this methodology might also serve antigen‐specific treatment of a CD8 T‐cell‐driven autoimmune disease. As a model for CD8 T‐cell‐mediated autoimmunity, we used OT‐1 T‐cell‐driven cholangitis in K14‐OVAp mice expressing the cognate MHC I‐restricted SIINFEKL peptide in cholangiocytes. To study whether peptide delivery to LSECs could modulate cholangitis, SIINFEKL peptide‐conjugated nanoparticles were administered intravenously one day before transfer of OT‐1 T cells; five days after cell transfer, liver pathology and hepatic infiltrates were analysed. SIINFEKL peptide‐conjugated nanoparticles were rapidly taken up by LSECs in vivo, which effectively cross‐presented the delivered peptide on MHC I molecules. Intriguingly, K14‐OVAp mice receiving SIINFEKL‐loaded nanoparticles manifested significantly reduced liver damage compared with vehicle‐treated K14‐OVAp mice. Mechanistically, treatment with LSEC‐targeting SIINFEKL‐loaded nanoparticles significantly reduced the number of liver‐infiltrating OT‐1 T cells, which up‐regulated expression of the co‐inhibitory receptor PD‐1 and down‐regulated cytotoxic effector function and inflammatory cytokine production. These findings show that tolerogenic LSECs can effectively internalize circulating nanoparticles and cross‐present nanoparticle‐bound peptides on MHC I molecules. Therefore, nanoparticle‐mediated autoantigen peptide delivery to LSECs might serve the antigen‐specific treatment of CD8 T‐cell‐driven autoimmune disease.

Nanomedicine-driven molecular targeting, drug delivery, and therapeutic approaches to cancer chemoresistance

Cancer cell resistance to chemotherapeutics (chemoresistance) poses a significant clinical challenge that oncology research seeks to understand and overcome. Multiple anticancer drugs and targeting agents can be incorporated in nanomedicines, in addition to different treatment modalities, forming a single nanoplatform that can be used to address tumor chemoresistance. Nanomedicine-driven molecular assemblies using nucleic acids, small interfering (si)RNAs, miRNAs, and aptamers in combination with stimuli-responsive therapy improve the pharmacokinetic (PK) profile of the drugs and enhance their accumulation in tumors and, thus, therapeutic outcomes. In this review, we highlight nanomedicine-driven molecular targeting and therapy combination used to improve the 3Rs (right place, right time, and right dose) for chemoresistant tumor therapies.

Perspective: The Lung, Particles, Fibers, Nanomaterials, and Autoimmunity

Studies have shown that a wide range of factors including drugs, chemicals, microbes, and other environmental agents can induce pre-clinical autoimmunity. However, only a few have been confidently linked to autoimmune diseases. Among these are exposures to inhaled particulates that are known to be associated with autoimmune diseases such as lupus and rheumatoid arthritis. In this article, the potential of particle, fiber, and nanomaterial exposures to induce autoimmunity is discussed. It is hypothesized that inhalation of particulate material known to be associated with human autoimmune diseases, such as cigarette smoke and crystalline silica, results in a complex interplay of a number of pathological processes, including, toxicity, oxidative stress, cell and tissue damage, chronic inflammation, post-translational modification of self-antigens, and the formation of lymphoid follicles that provide a milieu for the accumulation of autoreactive B and T cells necessary for the development and persistence of autoimmune responses, leading to disease. Although experimental studies show nanomaterials are capable of inducing several of the above features, there is no evidence that this matures to autoimmune disease. The procession of events hypothesized here provides a foundation from which to pursue experimental studies to determine the potential of other environmental exposures to induce autoimmunity and autoimmune disease.

Pre-clinical and Clinical Implications of "Inside-Out" vs. "Outside-In" Paradigms in Multiple Sclerosis Etiopathogenesis

Multiple Sclerosis (MS) is an immune-mediated neurological disorder, characterized by central nervous system (CNS) inflammation, oligodendrocyte loss, demyelination, and axonal degeneration. Although autoimmunity, inflammatory demyelination and neurodegeneration underlie MS, the initiating event has yet to be clarified. Effective disease modifying therapies need to both regulate the immune system and promote restoration of neuronal function, including remyelination. The challenge in developing an effective long-lived therapy for MS requires that three disease-associated targets be addressed: (1) self-tolerance must be re-established to specifically inhibit the underlying myelin-directed autoimmune pathogenic mechanisms; (2) neurons must be protected from inflammatory injury and degeneration; (3) myelin repair must be engendered by stimulating oligodendrocyte progenitors to remyelinate CNS neuronal axons. The combined use of chronic and relapsing remitting experimental autoimmune encephalomyelitis (C-EAE, R-EAE) (“outside-in”) as well as progressive diphtheria toxin A chain (DTA) and cuprizone autoimmune encephalitis (CAE) (“inside-out”) mouse models allow for the investigation and specific targeting of all three of these MS-associated disease parameters. The “outside-in” EAE models initiated by myelin-specific autoreactive CD4⁺ T cells allow for the evaluation of both myelin-specific tolerance in the absence or presence of neuroprotective and/or remyelinating agents. The “inside-out” mouse models of secondary inflammatory demyelination are triggered by toxin-induced oligodendrocyte loss or subtle myelin damage, which allows evaluation of novel therapeutics that could promote remyelination and neuroprotection in the CNS. Overall, utilizing these complementary pre-clinical MS models will open new avenues for developing therapeutic interventions, tackling MS from the “outside-in” and/or “inside-out”.

Tolerogenic Immunomodulation by PEGylated Antigenic Peptides

Current treatments for autoimmune disorders rely on non-specific immunomodulatory and global immunosuppressive drugs, which show a variable degree of efficiency and are often accompanied by side effects. In contrast, strategies aiming at inducing antigen-specific tolerance promise an exclusive specificity of the immunomodulation. However, although successful in experimental models, peptide-based tolerogenic "inverse" vaccines have largely failed to show efficacy in clinical trials. Recent studies showed that repetitive T cell epitopes, coupling of peptides to autologous cells, or peptides coupled to nanoparticles can improve the tolerogenic efficacy of peptides, suggesting that size and biophysical properties of antigen constructs affect the induction of tolerance. As these materials bear hurdles with respect to preparation or regulatory aspects, we wondered whether conjugation of peptides to the well-established and clinically proven synthetic material polyethylene glycol (PEG) might also work. We here coupled the T cell epitope OVA323-339 to polyethylene glycols of different size and structure and tested the impact of these nano-sized constructs on regulatory (Treg) and effector T cells in the DO11.10 adoptive transfer mouse model. Systemic vaccination with PEGylated peptides resulted in highly increased frequencies of Foxp3+ Tregs and reduced frequencies of antigen-specific T cells producing pro-inflammatory TNF compared to vaccination with the native peptide. PEGylation was found to extend the bioavailability of the model peptide. Both tolerogenicity and bioavailability were dependent on PEG size and structure. In conclusion, PEGylation of antigenic peptides is an effective and feasible strategy to improve Treg-inducing, peptide-based vaccines with potential use for the treatment of autoimmune diseases, allergies, and transplant rejection.

Induction of Antigen-Specific Tolerance in T Cell Mediated Diseases

The development of novel approaches to control unwanted immune responses represents an ambitious goal in the management of a number of clinical conditions, including autoimmunity, autoinflammatory diseases, allergies and replacement therapies, in which the T cell response to self or non-harmful antigens threatens the physiological function of tissues and organs. Current treatments for these conditions rely on the use of non-specific immunosuppressive agents and supportive therapies, which may efficiently dampen inflammation and compensate for organ dysfunction, but they require lifelong treatments not devoid of side effects. These limitations induced researchers to undertake the development of definitive and specific solutions to these disorders: the underlying principle of the novel approaches relies on the idea that empowering the tolerogenic arm of the immune system would restore the immune homeostasis and control the disease. Researchers effort resulted in the development of cell-free strategies, including gene vaccination, protein-based approaches and nanoparticles, and an increasing number of clinical trials tested the ability of adoptive transfer of regulatory cells, including T and myeloid cells. Here we will provide an overview of the most promising approaches currently under development, and we will discuss their potential advantages and limitations. The field is teaching us that the success of these strategies depends primarily on our ability to dampen antigen-specific responses without impairing protective immunity, and to manipulate directly or indirectly the immunomodulatory properties of antigen presenting cells, the ultimate in vivo mediators of tolerance.

Targeted Activation of T Cells with IL-2-Coupled Nanoparticles

Interleukin-2 (IL-2) is a T cell growth factor particularly required in regulatory T cell maintenance and memory T cell responses. High-dose IL-2 treatment was the first FDA-approved immunotherapy for cancer, while low-dose IL-2 administration has shown promise in allograft rejection and autoimmune and inflammatory diseases. However, its pleiotropic nature and the existence of IL-2 receptors with different binding affinity limit its therapeutic application. For an improved clinical applicability of the cytokine, a targeted receptor assignment must, therefore, be achieved. Nanoparticles allow controlling the location and dose of immunomodulating compounds and to specifically address specific receptors through targeted drug binding. In this review article we discuss the IL-2 biology and current clinical application with regard to nanoparticle-based IL-2-mediated manipulation of T cell responses in autoimmunity, chronic inflammation, and cancer.

Old Dog New Tricks: PLGA Microparticles as an Adjuvant for Insulin Peptide Fragment-Induced Immune Tolerance against Type 1 Diabetes

Poly[lactic-co-(glycolic acid)] (PLGA) is arguably one of the most versatile synthetic copolymers used for biomedical applications. In vivo delivery of multiple substances including cells, pharmaceutical compounds, and antigens has been achieved by using PLGA-based micro-/nanoparticles although, presently, the exact biological impact of PLGA particles on the immune system remains controversial. Type 1 diabetes (T1D) is one subtype of diabetes characterized by the attack of immune cells against self-insulin-producing pancreatic islet cells. Considering the autoimmune etiology of T1D and the recent use of PLGA particles for eliciting desired immune responses in various aspects of immunotherapy, for the present study, a combination of Ins2_9-23 peptide (a known autoantigen of T1D) and PLGA microparticles was selected for T1D prevention assessment in nonobese diabetic (NOD) mice, a well-known animal model with spontaneous development of T1D. Thus, inoculation of PLGA microparticles + Ins2_9-23 completely prevented T1D development, significantly better than untreated controls and mice treated by either PLGA microparticles or Ins2_9-23 per se. Subsequent mechanistic investigation further revealed a facilitative role of PLGA microparticles in immune tolerance induction. In summary, our data demonstrate an adjuvant potential of PLGA microparticles in tolerance induction and immune remodulation for effective prevention of autoimmune diseases such as T1D.

Biomaterial-Driven Immunomodulation: Cell Biology-Based Strategies to Mitigate Severe Inflammation and Sepsis

Inflammation is an essential component of a wide variety of disease processes and oftentimes can increase the deleterious effects of a disease. Finding ways to modulate this essential immune process is the basis for many therapeutics under development and is a burgeoning area of research for both basic and translational immunology. In addition to developing therapeutics for cellular and molecular targets, the use of biomaterials to modify innate and adaptive immune responses is an area that has recently sparked significant interest. In particular, immunomodulatory activity can be engineered into biomaterials to elicit heightened or dampened immune responses for use in vaccines, immune tolerance, or anti-inflammatory applications. Importantly, the inherent physicochemical properties of the biomaterials play a significant role in determining the observed effects. Properties including composition, molecular weight, size, surface charge, and others affect interactions with immune cells (i.e., nano-bio interactions) and allow for differential biological responses such as activation or inhibition of inflammatory signaling pathways, surface molecule expression, and antigen presentation to be encoded. Numerous opportunities to open new avenues of research to understand the ways in which immune cells interact with and integrate information from their environment may provide critical solutions needed to treat a variety of disorders and diseases where immune dysregulation is a key inciting event. However, to elicit predictable immune responses there is a great need for a thorough understanding of how the biomaterial properties can be tuned to harness a designed immunological outcome. This review aims to systematically describe the biological effects of nanoparticle properties-separate from additional small molecule or biologic delivery-on modulating innate immune cell responses in the context of severe inflammation and sepsis. We propose that nanoparticles represent a potential polypharmacological strategy to simultaneously modify multiple aspects of dysregulated immune responses where single target therapies have fallen short for these applications. This review intends to serve as a resource for immunology labs and other associated fields that would like to apply the growing field of rationally designed biomaterials into their work.

Tissue-Engineered Stromal Reticula to Study Lymph Node Fibroblastic Reticular Cells in Type I Diabetes

Introduction

Fibroblastic reticular cells (FRCs) support and remodel the lymph node (LN), express and present self-antigens to T cells to promote tolerance. In Type 1 diabetes (T1D), decrease in FRC frequency and in their expression of T1D-related self-antigens may hinder tolerogenic engagement of autoreactive T cells. FRC reticular organization in LNs is critical for adaptive immunity. Thus, we engineered LN-like FRC reticula to determine if FRC reticular properties were altered in T1D and to study engagement of autoreactive T cells in vitro.

Methods

We characterized FRC networks in pancreatic and skin-draining LNs of 4- and 12-week old non-obese diabetic (NOD) and diabetes resistant NOR mice by immunofluorescence. Murine FRCs isolated from NOR, NOD or human pancreatic LNs were cultured in collagen sponges for up to 21 days before immunofluorescence and flow cytometry analysis. NOD FRCs expressing T1D antigens were co-cultured with CellTrace-labeled specific T cells in 2D or in scaffolds. T cell engagement was quantified by CD25 upregulation, CellTrace dilution and by T cell tracking.

Results

FRC networks in both 4- and 12-week old NOD LNs displayed larger reticular pores than NOR controls. NOD FRCs had delayed scaffold remodeling compared to NOR FRCs. Expression of the gp38 FRC marker in NOD FRCs was lower than in NOR but improved in 3D. FRC reticula expressing T1D antigens promoted higher engagement of specific T cells than 2D.

Conclusion

We engineered LN-like FRC reticula that recapitulate FRC organization and phenotype of T1D LNs for studying tolerogenic autoreactive T cell engagement in T1D.

Nanoparticle-based immunotherapy: state of the art and future perspectives

INTRODUCTION

For several years now, medicine has been benefiting from the contribution of nanoparticles (NPs) technology for both diagnosis and therapy. They can be used as adjuvants, being capable per se of immune-modulating activity, or as carriers for molecules to be transported to a specific target, eventually loaded with specific ligands favoring specific uptake.

AREAS COVERED

The review focuses on experimental use of NPs as adjuvants/carriers for allergen immunotherapy (AIT). Human clinical trials conducted so far are discussed.

EXPERT OPINION

Results of experimental studies and recent clinical trials support the use of NPs as carrier/adjuvant in AIT. Comparisons between NP-based and classical AIT are needed, to show the usefulness of the NP-based approach. However, there are still unsolved problems: the persistence of non-degradable NPs with possible toxicological consequences, and the formation of the protein corona around the NPs, which could alter their activity and fate. Virus-like particles seem the most promising NPs for allergy treatment, as for other vaccines. Over the next decade, NP-based AIT will be largely used to treat allergic disorders.

Development of ImmTOR Tolerogenic Nanoparticles for the Mitigation of Anti-drug Antibodies

The development of anti-drug antibodies (ADAs) is a common cause for treatment failure and hypersensitivity reactions for many biologics. The focus of this review is the development of ImmTOR, a platform technology designed to prevent the formation of ADAs that can be applied broadly across a wide variety of biologics by inducing immunological tolerance with ImmTOR nanoparticles encapsulating rapamycin. The induction of tolerance is antigen-specific and dependent on the incorporation of rapamycin in nanoparticles and the presence of the antigen at the time of administration of ImmTOR. Evidence for the induction of specific immune tolerance vs. general immune suppression is supported by the findings that: (1) ImmTOR induces regulatory T cells specific to the co-administered antigen; (2) tolerance can be transferred by adoptive transfer of splenocytes from treated animals to naïve recipients; (3) the tolerance is durable to subsequent challenge with antigen alone; and (4) animals tolerized to a specific antigen are capable of responding to an unrelated antigen. ImmTOR nanoparticles can be added to new or existing biologics without the need to modify or reformulate the biologic drug. The ability of ImmTOR to mitigate the formation of ADAs has been demonstrated for coagulation factor VIII in a mouse model of hemophilia A, an anti-TNFα monoclonal antibody in a mouse model of inflammatory arthritis, pegylated uricase in hyperuricemic mice and in non-human primates, acid alpha-glucosidase in a mouse model of Pompe disease, recombinant immunotoxin in a mouse model of mesothelioma, and adeno-associated vectors in a model of repeat dosing of gene therapy vectors in mice and in non-human primates. Human proof-of concept for the mitigation of ADAs has been demonstrated with SEL-212, a combination product consisting of ImmTOR + pegadricase, a highly immunogenic enzyme therapy for the treatment of gout. ImmTOR represents a promising approach to preventing the formation of ADAs to a broad range of biologic drugs.

Multiplex T Cell Stimulation Assay Utilizing a T Cell Activation Reporter-Based Detection System

Recent advancements in single cell sequencing technologies allow for identification of numerous immune-receptors expressed by T cells such as tumor-specific and autoimmune T cells. Determining antigen specificity of those cells holds immense therapeutic promise. Therefore, the purpose of this study was to develop a method that can efficiently test antigen reactivity of multiple T cell receptors (TCRs) with limited cost, time, and labor. Nuclear factor of activated T cells (NFAT) is a transcription factor involved in producing cytokines and is often utilized as a reporter system for T cell activation. Using a NFAT-based fluorescent reporter system, we generated T-hybridoma cell lines that express intensely fluorescent proteins in response to antigen stimulation and constitutively express additional fluorescent proteins, which serve as identifiers of each T-hybridoma expressing a unique TCR. This allows for the combination of multiple T-hybridoma lines within a single reaction. Sensitivity to stimulation is not decreased by adding fluorescent proteins or multiplexing T cells. In multiplexed reactions, response by one cell line does not induce response in others, thus preserving specificity. This multiplex assay system will be a useful tool for antigen discovery research in a variety of contexts, including using combinatorial peptide libraries to determine T cell epitopes.