Helminth egg derivatives as proregenerative immunotherapies.

The immune system is increasingly recognized as an important regulator of tissue repair. We developed a regenerative immunotherapy from the helminth Schistosoma mansoni soluble egg antigen (SEA) to stimulate production of interleukin (IL)-4 and other type 2-associated cytokines without negative infection-related sequelae. The regenerative SEA (rSEA) applied to a murine muscle injury induced accumulation of IL-4-expressing T helper cells, eosinophils, and regulatory T cells and decreased expression of IL-17A in gamma delta (γδ) T cells, resulting in improved repair and decreased fibrosis. Encapsulation and controlled release of rSEA in a hydrogel further enhanced type 2 immunity and larger volumes of tissue repair. The broad regenerative capacity of rSEA was validated in articular joint and corneal injury models. These results introduce a regenerative immunotherapy approach using natural helminth derivatives.

A sublingual nanofiber vaccine to prevent urinary tract infections.

Urinary tract infections (UTIs) are a major public health problem affecting millions of individuals each year. Recurrent UTIs are managed by long-term antibiotic use, making the alarming rise of antibiotic resistance a substantial threat to future UTI treatment. Extended antibiotic regimens may also have adverse effects on the microbiome. Here, we report the use of a supramolecular vaccine to provide long-term protection against uropathogenic Escherichia coli, which cause 80% of uncomplicated UTIs. We designed mucus-penetrating peptide-polymer nanofibers to enable sublingual (under the tongue) vaccine delivery and elicit antibody responses systemically and in the urogenital tract. In a mouse model of UTI, we demonstrate equivalent efficacy to high-dose oral antibiotics but with significantly less perturbation of the gut microbiome. We also formulate our vaccine as a rapid-dissolving sublingual tablet that raises response in mice and rabbits. Our approach represents a promising alternative to antibiotics for the treatment and prevention of UTIs.

Stoichiometric Post-Modification of Hydrogel Microparticles Dictates Neural Stem Cell Fate in Microporous Annealed Particle Scaffolds.

Microporous annealed particle (MAP) scaffolds are generated from assembled hydrogel microparticles (microgels). It has been previously demonstrated that MAP scaffold are porous, biocompatible, and recruit neural progenitor cells (NPCs) to the stroke cavity after injection into the stroke core. Here, the goal is to study NPC fate inside MAP scaffolds in vitro. To create plain microgels that can later be converted to contain different types of bioactivities, the inverse electron-demand Diels-Alder reaction between tetrazine and norbornene is utilized, which allows the post-modification of plain microgels stoichiometrically. As a result of adhesive peptide attachment, NPC spreading leads to contractile force generation which can be recorded by tracking microgel displacement. Alternatively, non-adhesive peptide integration results in neurosphere formation that grows within the void space of MAP scaffolds. Although the formed neurospheres do not impose a contractile force on the scaffolds, they are seen to continuously transverse the scaffolds. It is concluded that MAP scaffolds  can be engineered to either promote neurogenesis or enhance stemness depending on the chosen post-modifications of the microgels, which can be key in modulating their phenotypes in various applications in vivo.

Biomaterials direct functional B cell response in a material-specific manner.

B cells are an adaptive immune target of biomaterials development in vaccine research but, despite their role in wound healing, have not been extensively studied in regenerative medicine. To probe the role of B cells in biomaterial scaffold response, we evaluated the B cell response to biomaterial materials implanted in a muscle wound using a biological extracellular matrix (ECM), as a reference for a naturally derived material, and synthetic polyester polycaprolactone (PCL), as a reference for a synthetic material. In the local muscle tissue, small numbers of B cells are present in response to tissue injury and biomaterial implantation. The ECM materials induced mature B cells in lymph nodes and antigen presentation in the spleen. The synthetic PCL implants resulted in prolonged B cell presence in the wound and induced an antigen-presenting phenotype. In summary, the adaptive B cell immune response to biomaterial induces local, regional, and systemic immunological changes.

Modular complement assemblies for mitigating inflammatory conditions.

Complement protein C3dg, a key linkage between innate and adaptive immunity, is capable of stimulating both humoral and cell-mediated immune responses, leading to considerable interest in its use as a molecular adjuvant. However, the potential of C3dg as an adjuvant is limited without ways of controllably assembling multiple copies of it into vaccine platforms. Here, we report a strategy to assemble C3dg into supramolecular nanofibers with excellent compositional control, using ß-tail fusion tags. These assemblies were investigated as therapeutic active immunotherapies, which may offer advantages over existing biologics, particularly toward chronic inflammatory diseases. Supramolecular assemblies based on the Q11 peptide system containing ß-tail-tagged C3dg, B cell epitopes from TNF, and the universal T cell epitope PADRE raised strong antibody responses against both TNF and C3dg, and prophylactic immunization with these materials significantly improved protection in a lethal TNF-mediated inflammation model. Additionally, in a murine model of psoriasis induced by imiquimod, the C3dg-adjuvanted nanofiber vaccine performed as well as anti-TNF monoclonal antibodies. Nanofibers containing only ß-tail-C3dg and lacking the TNF B cell epitope also showed improvements in both models, suggesting that supramolecular C3dg, by itself, played an important therapeutic role. We observed that immunization with ß-tail-C3dg caused the expansion of an autoreactive C3dg-specific T cell population, which may act to dampen the immune response, preventing excessive inflammation. These findings indicate that molecular assemblies displaying C3dg warrant further development as active immunotherapies.

Titrating Polyarginine into Nanofibers Enhances Cyclic-Dinucleotide Adjuvanticity in Vitro and after Sublingual Immunization.

Effective sublingual peptide immunization requires overcoming challenges of both delivery and immunogenicity. Mucosal adjuvants, such as cyclic-dinucleotides (CDN), can promote sublingual immune responses but must be codelivered with the antigen to the epithelium for maximum effect. We designed peptide-polymer nanofibers (PEG-Q11) displaying nona-arginine (R9) at a high density to promote complexation with CDNs via bidentate hydrogen-bonding with arginine side chains. We coassembled PEG-Q11 and PEG-Q11R9 peptides to titrate the concentration of R9 within nanofibers. In vitro, PEG-Q11R9 fibers and cyclic-di-GMP or cyclic-di-AMP adjuvants had a synergistic effect on enhancing dendritic cell activation that was STING-dependent and increased monotonically with increasing R9 concentration. The polyvalent display of R9 on assembled nanofibers was significantly more effective at promoting CDN-mediated DC activation in vitro than mixing nanofibers with an equimolar concentration of unassembled R9 peptide. The sublingual administration of nanofibers revealed a bell-shaped trend between increasing R9 concentration and enhancements to antigen trafficking and the activation of DCs in the draining lymph nodes. Intermediate levels of R9 within sublingually administered PEG-Q11 fibers were optimal for immunization, suggesting a balance between polyarginine's ability to sequester CDNs along the nanofiber and its potentially detrimental mucoadhesive interactions. These findings present a potentially generalizable biomaterial strategy for enhancing the potency of CDN adjuvants and reveal important design considerations for the nascent field of sublingual biomaterial immunization.

Tabletized Supramolecular Assemblies for Sublingual Peptide Immunization.

Widespread vaccination is essential to global health. Significant barriers exist to improving vaccine coverage in lower- and middle-income countries, including the costly requirements for cold-chain distribution and trained medical personnel to administer the vaccines. A heat-stable and highly porous tablet vaccine that can be administered sublingually via simple dissolution under the tongue is described. SIMPL tablet vaccines (Supramolecular IMmunization with Peptides subLingually) are produced by freeze-drying a mixture of self-assembling peptide-polymer nanofibers, sugars, and adjuvant. Sublingual immunization with SIMPL tablets raises antibody responses against both a model epitope from ovalbumin and a clinically relevant epitope from Mycobacterium tuberculosis. Further, sublingual antibody responses are not diminished after heating the tablets for 1 week at 45 °C, in contrast to a more conventional carrier vaccine (KLH). This approach directly addresses the need for a heat-stable and easily deliverable vaccine to improve equity in global vaccine coverage.

Intranasal Subunit Vaccination Strategies Employing Nanomaterials and Biomaterials.

Intranasal vaccines offer key advantages over traditional needle-based vaccines. They are simple to administer and painless and establish local immunity at mucosal surfaces. Owing to these advantages, they are particularly attractive for use in resource-limited locations of the world. Subunit vaccines also have advantages for global distribution, as they can be engineered to be more stable to fluctuations in environmental conditions than live-attenuated or inactivated vaccines, but they tend to be poorly immunogenic intranasally. Toward realizing the potential of intranasal subunit vaccination, biomaterial-based technologies are emerging. This review provides an overview of recent progress in the preclinical development of biomaterial-based intranasal vaccines against subunit antigens and should serve as an effective introduction to the current state of this exciting field. We provide a brief overview of the obstacles facing intranasal vaccine development and identify key design criteria for consideration when designing biomaterials for intranasal subunit vaccine delivery. Promising strategies are discussed across a wide array of biomaterial classes, with a focus on selected exemplary works that highlight the considerable potential of intranasal vaccines and the biomaterial-based technologies that enable them.

Multifactorial Design of a Supramolecular Peptide Anti-IL-17 Vaccine Toward the Treatment of Psoriasis.

Current treatments for chronic immune-mediated diseases such as psoriasis, rheumatoid arthritis, or Crohn's disease commonly rely on cytokine neutralization using monoclonal antibodies; however, such approaches have drawbacks. Frequent repeated dosing can lead to the formation of anti-drug antibodies and patient compliance issues, and it is difficult to identify a single antibody that is broadly efficacious across diverse patient populations. As an alternative to monoclonal antibody therapy, anti-cytokine immunization is a potential means for long-term therapeutic control of chronic inflammatory diseases. Here we report a supramolecular peptide-based approach for raising antibodies against IL-17 and demonstrate its efficacy in a murine model of psoriasis. B-cell epitopes from IL-17 were co-assembled with the universal T-cell epitope PADRE using the Q11 self-assembling peptide nanofiber system. These materials, with or without adjuvants, raised antibody responses against IL-17. Exploiting the modularity of the system, multifactorial experimental designs were used to select formulations maximizing titer and avidity. In a mouse model of psoriasis induced by imiquimod, unadjuvanted nanofibers had therapeutic efficacy, which could be enhanced with alum adjuvant but reversed with CpG adjuvant. Measurements of antibody subclass induced by adjuvanted and unadjuvanted formulations revealed strong correlations between therapeutic efficacy and titers of IgG1 (improved efficacy) or IgG2b (worsened efficacy). These findings have important implications for the development of anti-cytokine active immunotherapies and suggest that immune phenotype is an important metric for eliciting therapeutic anti-cytokine antibody responses.

Adjuvant-free nanofiber vaccine induces in situ lung dendritic cell activation and TH17 responses.

The current paradigm that subunit vaccines require adjuvants to optimally activate innate immunity implies that increased vaccine reactogenicity will invariably be linked to improved immunogenicity. Countering this paradigm, nanoparticulate vaccines have been reported to act as delivery systems for vaccine antigens and induce immunity without the need for exogenous adjuvants or local inflammation; however, the mechanisms underlying the immunogenicity of nanoparticle vaccines are incompletely identified. Here, we show that antigens displayed on self-assembling nanofiber scaffolds and delivered intranasally are presented by CD103+ and CD11b+ lung dendritic cells that up-regulate CD80 and migrate into the draining lymph node (LN). This was accompanied by a nearly exclusive priming and accumulation of antigen-specific TH17 cells occurring independently in both LN and lung. Thus, self-assembling peptide nanofiber vaccines may represent a novel, needle- and adjuvant-free means of eliciting protective immunity against fungal and bacterial infections at skin and mucosal barrier surfaces.

Controlled Lengthwise Assembly of Helical Peptide Nanofibers to Modulate CD8+ T-Cell Responses.

Peptide nanofibers are useful for many biological applications, including immunotherapy, tissue engineering, and drug delivery. The robust lengthwise assembly of these peptides into nanofibers is typically difficult to control, resulting in polydisperse fiber lengths and an incomplete understanding of how nanofiber length affects biological responses. Here, rationally designed capping peptides control the length of helical peptide nanofibers with unique precision. These designed peptides bind the tips of elongated nanofibers to shorten and narrow their length distributions. Demonstrating their use as immunotherapies, capped nanofibers are preferentially cross-presented by dendritic cells compared to uncapped nanofibers. Due to increased cross-presentation, these capped nanofibers trigger stronger CD8+ T-cell responses in mice than uncapped nanofibers. This strategy illustrates a means for controlling the length of supramolecular peptide nanofibers to modulate their immunogenicity in the context of immunotherapies.

Comparative study of α-helical and ß-sheet self-assembled peptide nanofiber vaccine platforms: influence of integrated T-cell epitopes.

Several different self-assembling peptide systems that form nanofibers have been investigated as vaccine platforms, but design principles for adjusting the character of the immune responses they raise have yet to be well articulated. Here we compared the immune responses raised by two structurally dissimilar peptide nanofibers, one a ß-sheet fibrillar system (Q11), and one an α-helical nanofiber system (Coil29), hypothesizing that integrated T-cell epitopes within the latter would promote T follicular helper (Tfh) cell engagement and lead to improved antibody titers and quality. Despite significantly different internal structures, nanofibers of the two peptides exhibited surprisingly similar nanoscale morphologies, and both were capable of raising strong antibody responses to conjugated peptide epitopes in mice without adjuvant. Both were minimally inflammatory, but as hypothesized Coil29 nanofibers elicited antibody responses with higher titers and avidities against a conjugated model epitope (OVA323-339) and a candidate peptide epitope for vaccination against S. aureus. Subsequent investigation indicated that Coil29 nanofibers possessed internal CD4+ T cell epitopes: whereas Q11 nanofibers required co-assembly of additional CD4+ T cell epitopes to be immunogenic, Coil29 nanofibers did not. Coil29 nanofibers also raised stronger germinal center B cell responses and follicular helper T cell (Tfh) responses relative to Q11 nanofibers, likely facilitating the improvement of the antibody response. These findings illustrate design strategies for improving humoral responses raised by self-assembled peptide nanofibers.

Enabling sublingual peptide immunization with molecular self-assemblies.

Short peptides are poorly immunogenic when delivered sublingually - under the tongue. Nanomaterial delivery of peptides could be utilized to improve immunogenicity towards designed sublingual vaccines, but nanomaterials have not been widely successful in sublingual vaccines owing to the challenges of transport through the sublingual mucosa. Here, we report that the sublingual immunogenicity of peptides is negligible, even in the presence of sublingual adjuvants or when PEGylated, but can be dramatically enhanced by assembly into supramolecular polymer-peptide nanofibers bearing low-molecular weight PEG, optimally between 2000 and 3000 Da. Neither PEGylation nor a sublingual adjuvant were capable of rendering peptides immunogenic without assembly into nanofibers. We found that PEG decreased nanofiber interactions with mucin and promoted longer residence time at the sublingual immunization site. Parallel investigations with shortened nanofibers indicated that the size of the assemblies had a surprisingly negligible influence over sublingual immunogenicity. In mice, optimized formulations were capable of raising strong and highly durable systemic antibody responses, antibodies in the upper respiratory and reproductive tracts, and systemic antigen-specific T-cell responses. These nanofiber-based sublingual vaccines were effective with both protein and nucleotide adjuvants and raised responses against both a model peptide epitope and a peptide epitope from M. tuberculosis. Further, PASylation (modification of nanofibers with peptide sequences rich in Pro, Ala, and Ser) could be substituted for PEGylation to also achieve sublingual immunogenicity. These findings indicated that surface properties supersede nanomaterial size in modulating sublingual nanomaterial immunogenicity, having important implications for the design of synthetic sublingual vaccines.

Intranasal delivery of adjuvant-free peptide nanofibers elicits resident CD8+ T cell responses.

Influenza vaccines that can be administered intranasally or by other needle-free delivery routes have potential advantages over injected formulations in terms of patient compliance, cost, and ease of global distribution. Supramolecular peptide nanofibers have been investigated previously as platforms for vaccines and immunotherapies and have been shown to raise immune responses in the absence of exogenous adjuvants and without measurable inflammation. However, at present it has not been tested whether the immunogenicity of these materials extends to the intranasal route. Here we investigated the extent to which self-assembled peptide nanofibers bearing an influenza peptide epitope elicit antigen-specific CD8+ T cell responses when delivered intranasally, and we compared these responses with those elicited by subcutaneous immunization. Peptides containing an epitope from influenza acid polymerase (PA) and the Q11 self-assembly domain formed nanofibers that were avidly taken up by dendritic cells in lung-draining mediastinal lymph nodes after intranasal immunization. Intranasally delivered nanofibers generated greater antigen-specific CD8+ T cell responses in the lung-draining lymph nodes than subcutaneous immunizations while retaining the non-inflammatory character of the materials observed in other delivery sites. The CD8+ T cells elicited systemically were functional as assessed by their ability to produce IFN-γ ex vivo, lyse epitope-pulsed target cells in vivo, and diminish viral loads in infected mice. Compared to subcutaneously delivered nanofibers, intranasally delivered peptide nanofibers significantly increased the number of persisting antigen-specific tissue resident memory CD8+ T cells in the lung, allowing for a more rapid response to infection at 6 weeks post-vaccination. These results indicate that intranasally delivered self-assembled peptide nanofibers are immunogenic when delivering CD8+ epitopes without adjuvant or CD4+ epitopes, are non-inflammatory, and promote more lung-resident memory CD8+ T cells compared to subcutaneous immunization.

Biomaterial strategies for generating therapeutic immune responses.

Biomaterials employed to raise therapeutic immune responses have become a complex and active field. Historically, vaccines have been developed primarily to fight infectious diseases, but recent years have seen the development of immunologically active biomaterials towards an expanding list of non-infectious diseases and conditions including inflammation, autoimmunity, wounds, cancer, and others. This review structures its discussion of these approaches around a progression from single-target strategies to those that engage increasingly complex and multifactorial immune responses. First, the targeting of specific individual cytokines is discussed, both in terms of delivering the cytokines or blocking agents, and in terms of active immunotherapies that raise neutralizing immune responses against such single cytokine targets. Next, non-biological complex drugs such as randomized polyamino acid copolymers are discussed in terms of their ability to raise multiple different therapeutic immune responses, particularly in the context of autoimmunity. Last, biologically derived matrices and materials are discussed in terms of their ability to raise complex immune responses in the context of tissue repair. Collectively, these examples reflect the tremendous diversity of existing approaches and the breadth of opportunities that remain for generating therapeutic immune responses using biomaterials.

A Supramolecular Vaccine Platform Based on α-Helical Peptide Nanofibers.

A supramolecular peptide vaccine system was designed in which epitope-bearing peptides self-assemble into elongated nanofibers composed almost entirely of alpha-helical structure. The nanofibers were readily internalized by antigen presenting cells and produced robust antibody, CD4+ T-cell, and CD8+ T-cell responses without supplemental adjuvants in mice. Epitopes studied included a cancer B-cell epitope from the epidermal growth factor receptor class III variant (EGFRvIII), the universal CD4+ T-cell epitope PADRE, and the model CD8+ T-cell epitope SIINFEKL, each of which could be incorporated into supramolecular multi-epitope nanofibers in a modular fashion.