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

Tuning Helical Peptide Nanofibers as a Sublingual Vaccine Platform for a Variety of Peptide Epitopes

Mucosal immune responses to vaccination are essential for achieving full protection against pathogens entering their host at mucosal sites. However, traditional parenteral immunization routes commonly fail to raise significant mucosal immunity. Sublingual immunization is a promising alternative delivery route to raise robust immune responses both systemically and at mucosal sites, and nanomaterial-based subunit vaccine platforms offer opportunities for raising epitope-specific responses. Here, sublingual immunization is reported using the Coil29 platform of coiled-coil self-assembling peptide nanofibers. The successful immunization with epitopes of varying physicochemical properties by including mucus-modulating components - namely sequences of proline, alanine, and serine (PAS) is demonstrated. PASylation is shown to decrease mucin complexation and increase epithelial penetration in vitro, enabling sublingual immunization against a variety of selected peptide epitopes in vivo. Coil29 fibers are also readily formed into tablets for solid-state dosing formulations and maintain their immunogenicity in this state. Previous sublingual peptide nanofiber immunotherapies have been based on different structures, such as highly stable β-sheets. The present work demonstrates that alternatively folded structures such as α-helical nanofibers can also be rendered sublingually immunogenic, enabling immunization with a variety of peptide epitopes and offering additional ways to specify mucus interactions, delivery state, dosing, and formulation.

Supramolecular Peptide Self-Assemblies Facilitate Oral Immunization

Oral immunization is a promising strategy for preventing and treating gastrointestinal (GI) infections and diseases, as it allows for direct access to the disease site. To elicit immune responses within the GI tract, however, there are many obstacles that oral vaccines must surmount, including proteolytic degradation and thick mucus barriers. Here, we employed a modular self-assembling peptide nanofiber platform to facilitate oral immunization against both peptide and small molecule epitopes. Synthesizing nanofibers with d-amino acids rendered them resistant to proteases in vitro, whereas l-amino acid nanofibers were rapidly degraded. Additionally, the inclusion of peptide sequences rich in proline, alanine, and serine (PAS), increased nanofiber muco-penetration, and accelerated nanofiber transport through the GI tract. Oral immunization with PASylated nanofibers and mucosal adjuvant generated local and systemic immune responses to a peptide epitope but only for l-amino acid nanofibers. Further, we were able to apply this design to also enable oral immunization against a small molecule epitope and illustrated the therapeutic and prophylactic effectiveness of these immunizations in mouse models of colitis. These findings demonstrate that supramolecular peptide self-assemblies have promise as oral vaccines and immunotherapies.

Self-adjuvanted L-arginine-modified dextran-based nanogels for sustained local antigenic protein delivery to antigen-presenting cells and enhanced cellular and humoral immune responses

In the development of cancer vaccines, antigens are delivered to elicit potent and specific T-cell responses to eradicate tumour cells. Nonetheless, successful vaccines are often hampered by the poor immunogenicity of tumour antigens, rapid clearance by the innate immunity, and limited cross-presentation on MHC-I to activate CD8+ T-cells arm. To address these issues, we developed dextran-based nanogels to promote antigen uptake, storage, and cross-presentation on MHC-I, while directing immunogenic maturation of the antigen-presenting cells (APCs). To promote the nanocarriers interaction with cells, we modified DX with L-arginine (Arg), whose immunomodulatory activities have been well documented. The ArgDX nanogel performance was compared with the nanogel modified with L-histidine (His) and L-glutamate (Glut). Moreover, we introduced pH-sensitive hydrazone crosslinking during the nanogel formation for the conjugation and controlled release of antigen ovalbumin (OVA). The OVA-laden nanogels have an average size of 325 nm. We demonstrated that the nanogels could rapidly release cargoes upon a pH change from 7 to 5 within 8 days, indicating the controlled release of antigens in the acidic cellular compartments upon internalization. Our results revealed that the ArgDX nanogel could promote greater antigen uptake and storage in DCs in vitro and promoted a stronger immunogenic maturation of DCs and M1 polarization of the macrophages. The OVA signals were co-localized with lysosomal compartments up till 96 hours post-treatment and washing, suggesting the nanogels could facilitate prolonged antigen storage and supply from endo-lysosomal compartments. Furthermore, all the tested nanogel formulations retained antigens at the skin injection sites until day 21. Such delayed clearance could be due to the formation of micron-sized aggregates of OVA-laden nanogels, extending the interactions with the resident DCs. Amongst the amino acid modifications, ArgDX nanogels promoted the highest level of lymph node homing signal CCR7 on DCs. The nanogels also showed higher antigen presentation on both MHC-I and II than DX in vitro. In the in vivo immune studies, ArgDX nanogels were more superior in inducing cellular and humoral immunity than the other treatment groups on day 21 post-treatment. These results suggested that ArgDX nanogel is a promising self-adjuvanted nanocarrier for vaccine delivery.

Self-Assembling Allergen Vaccine Platform Raises Therapeutic Allergen-Specific IgG Responses without Induction of Systemic Allergic Responses

Allergen immunotherapies are often successful at desensitizing allergic patients but can require life-long dosing and suffer from frequent adverse events including instances of systemic anaphylaxis, leading to poor patient compliance and high cost. Allergen vaccines, in turn, can generate more durable immunological allergen desensitization with far fewer doses. However, like immunotherapies, allergen vaccines are often highly reactogenic in allergic patients, hampering their use in therapeutic settings. In this work, we utilize a peptide-based self-assembling nanofiber platform to design allergen vaccines against allergen B-cell epitopes that do not elicit systemic anaphylaxis when administered subcutaneously to allergic mice. We show that, in contrast to protein vaccines, nanofiber vaccines prevent leakage of allergen material into the vascular compartment, a feature that likely underpins their reduced systemic reactogenicity. Further, we show that our allergen vaccine platform elicits therapeutic IgG antibody responses capable of desensitizing allergic mice to allergen-induced Type I hypersensitivity reactions. Finally, we have demonstrated a proof-of-concept for the therapeutic potential of nanofiber-based peanut allergen vaccines directed against peanut allergen-derived epitopes.

A novel self-assembled nucleobase-nanofiber platform of CDN to activate the STING pathway for synergistic cancer immunotherapy

2', 3'-cGAMP (CDN) as cGAS-STING pathway agonist is extensively used in tumor treatment. However, due to its negatively charged nature (containing two phosphate groups) and high hydrophilicity, CDN faces challenges in crossing cell membranes, resulting in reduced efficiency of its use. Additionally, CDN is susceptible to inactivation through phosphodiesterase hydrolysis. Therefore, the development of a new drug delivery system for CDN is necessary to prevent hydrolysis and enhance targeted accumulation in tumors, as well as improve cellular uptake for STING activation. In this study, we have developed peptide-polymer nanofibers (PEG-Q11) that incorporate thymine (T) and arginine (R) residues to facilitate complexation with CDN through the principles of Watson-Crick base pairing with thymine and favorable electrostatic interactions and bidentate hydrogen bonding with arginine side chains. The entrapment efficiency (EE) of PEG-Q11T3R4@CDN was found to be 51% higher than that of PEG-Q11@CDN. Due to its favorable biocompatibility, PEG-Q11T3R4@CDN was employed for immunotherapy in mouse CT26 tumors. In local tumor treatment, the administration of PEG-Q11T3R4@CDN at a low dose and through a single injection exhibited inhibitory effects. Furthermore, the local injection of PEG-Q11T3R4@CDN resulted in systemic therapeutic responses, effectively suppressing tumor metastasis by activating CD8 + T cells to target distant tumors. This research not only underscores the potential of PEG-Q11T3R4@CDN as an efficient therapeutic agent but also highlights its ability to achieve long-lasting systemic therapeutic outcomes following local treatment. Consequently, PEG-Q11T3R4@CDN represents a promising strategy for immunization.

Peptide Hydrogels as Immunomaterials and Their Use in Cancer Immunotherapy Delivery

Peptide-based hydrogel biomaterials have emerged as an excellent strategy for immune system modulation. Peptide-based hydrogels are supramolecular materials that self-assemble into various nanostructures through various interactive forces (i.e., hydrogen bonding and hydrophobic interactions) and respond to microenvironmental stimuli (i.e., pH, temperature). While they have been reported in numerous biomedical applications, they have recently been deemed promising candidates to improve the efficacy of cancer immunotherapies and treatments. Immunotherapies seek to harness the body's immune system to preemptively protect against and treat various diseases, such as cancer. However, their low efficacy rates result in limited patient responses to treatment. Here, the immunomaterial's potential to improve these efficacy rates by either functioning as immune stimulators through direct immune system interactions and/or delivering a range of immune agents is highlighted. The chemical and physical properties of these peptide-based materials that lead to immuno modulation and how one may design a system to achieve desired immune responses in a controllable manner are discussed. Works in the literature that reports peptide hydrogels as adjuvant systems and for the delivery of immunotherapies are highlighted. Finally, the future trends and possible developments based on peptide hydrogels for cancer immunotherapy applications are discussed.

Expanding opportunities to engineer mucosal vaccination with biomaterials

Mucosal vaccines are receiving increasing interest both for protecting against infectious diseases and for inducing therapeutic immune responses to treat non-infectious diseases. However, the mucosal barriers of the lungs, gastrointestinal tract, genitourinary tract, nasal, and oral tissues each present unique challenges for constructing efficacious vaccines. Vaccination through each of these mucosae requires transport through the mucus and across specialized epithelia to reach tissue-specific immune cells and lymphoid structures, necessitating finely tuned and multifunctional strategies. Serving as inspiration for mucosal vaccine design, pathogens have evolved elaborate, diverse, and multipronged approaches to penetrate and infect mucosae. This review is focused on biomaterials-based strategies, many inspired by pathogens, for designing mucosal vaccine platforms. Passive and active technologies are discussed, along with the microbial processes that they seek to mimic.

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.

Immunostimulatory Polymers as Adjuvants, Immunotherapies, and Delivery Systems

Activating innate immunity in a controlled manner is necessary for the development of next-generation therapeutics. Adjuvants, or molecules that modulate the immune response, are critical components of vaccines and immunotherapies. While small molecules and biologics dominate the adjuvant market, emerging evidence supports the use of immunostimulatory polymers in therapeutics. Such polymers can stabilize and deliver cargo while stimulating the immune system by functioning as pattern recognition receptor (PRR) agonists. At the same time, in designing polymers that engage the immune system, it is important to consider any unintended initiation of an immune response that results in adverse immune-related events. Here, we highlight biologically derived and synthetic polymer scaffolds, as well as polymer–adjuvant systems and stimuli-responsive polymers loaded with adjuvants, that can invoke an immune response. We present synthetic considerations for the design of such immunostimulatory polymers, outline methods to target their delivery, and discuss their application in therapeutics. Finally, we conclude with our opinions on the design of next-generation immunostimulatory polymers, new applications of immunostimulatory polymers, and the development of improved preclinical immunocompatibility tests for new polymers.

Nanofiber Carriers of Therapeutic Load: Current Trends

The fast advancement in nanotechnology has prompted the improvement of numerous methods for the creation of various nanoscale composites of which nanofibers have gotten extensive consideration. Nanofibers are polymeric/composite fibers which have a nanoscale diameter. They vary in porous structure and have an extensive area. Material choice is of crucial importance for the assembly of nanofibers and their function as efficient drug and biomedicine carriers. A broad scope of active pharmaceutical ingredients can be incorporated within the nanofibers or bound to their surface. The ability to deliver small molecular drugs such as antibiotics or anticancer medications, proteins, peptides, cells, DNA and RNAs has led to the biomedical application in disease therapy and tissue engineering. Although nanofibers have shown incredible potential for drug and biomedicine applications, there are still difficulties which should be resolved before they can be utilized in clinical practice. This review intends to give an outline of the recent advances in nanofibers, contemplating the preparation methods, the therapeutic loading and release and the various therapeutic applications.

Untangling Mucosal Drug Delivery: Engineering, Designing, and Testing Nanoparticles to Overcome the Mucus Barrier

Mucus is a complex viscoelastic gel and acts as a barrier covering much of the soft tissue in the human body. High vascularization and accessibility have motivated drug delivery to various mucosal surfaces; however, these benefits are hindered by the mucus layer. To overcome the mucus barrier, many nanomedicines have been developed, with the goal of improving the efficacy and bioavailability of drug payloads. Two major nanoparticle-based strategies have emerged to facilitate mucosal drug delivery, namely, mucoadhesion and mucopenetration. Generally, mucoadhesive nanoparticles promote interactions with mucus for immobilization and sustained drug release, whereas mucopenetrating nanoparticles diffuse through the mucus and enhance drug uptake. The choice of strategy depends on many factors pertaining to the structural and compositional characteristics of the target mucus and mucosa. While there have been promising results in preclinical studies, mucus-nanoparticle interactions remain poorly understood, thus limiting effective clinical translation. This article reviews nanomedicines designed with mucoadhesive or mucopenetrating properties for mucosal delivery, explores the influence of site-dependent physiological variation among mucosal surfaces on efficacy, transport, and bioavailability, and discusses the techniques and models used to investigate mucus-nanoparticle interactions. The effects of non-homeostatic perturbations on protein corona formation, mucus composition, and nanoparticle performance are discussed in the context of mucosal delivery. The complexity of the mucosal barrier necessitates consideration of the interplay between nanoparticle design, tissue-specific differences in mucus structure and composition, and homeostatic or disease-related changes to the mucus barrier to develop effective nanomedicines for mucosal delivery.

The Promise and Challenges of Cyclic Dinucleotides as Molecular Adjuvants for Vaccine Development

Cyclic dinucleotides (CDNs), originally discovered as bacterial second messengers, play critical roles in bacterial signal transduction, cellular processes, biofilm formation, and virulence. The finding that CDNs can trigger the innate immune response in eukaryotic cells through the stimulator of interferon genes (STING) signalling pathway has prompted the extensive research and development of CDNs as potential immunostimulators and novel molecular adjuvants for induction of systemic and mucosal innate and adaptive immune responses. In this review, we summarize the chemical structure, biosynthesis regulation, and the role of CDNs in enhancing the crosstalk between host innate and adaptive immune responses. We also discuss the strategies to improve the efficient delivery of CDNs and the recent advance and future challenges in the development of CDNs as potential adjuvants in prophylactic vaccines against infectious diseases and in therapeutic vaccines against cancers.