Immune responses to coiled coil supramolecular biomaterials

Engineering Antigen-Specific Tolerance to an Artificial Protein Hydrogel

Artificial protein hydrogels are an emerging class of biomaterials with numerous prospective applications in tissue engineering and regenerative medicine. These materials are likely to be immunogenic due to their frequent incorporation of novel amino acid sequence domains, which often serve a functional role within the material itself. We engineered injectable "self" and "nonself" artificial protein hydrogels, which were predicted to have divergent immune outcomes in vivo on the basis of their primary amino acid sequence. Following implantation in mouse, the nonself gels raised significantly higher antigel antibody titers than the corresponding self gels. Prophylactic administration of a fusion antibody targeting the nonself hydrogel epitopes to DEC-205, an endocytic receptor involved in Treg induction, fully suppressed the elevated antibody titer against the nonself gels. These results suggest that the clinical immune response to artificial protein biomaterials, including those that contain highly antigenic sequence domains, can be tuned through the induction of antigen-specific tolerance.

Peptides for Vaccine Development

This review discusses peptide epitopes used as antigens in the development of vaccines in clinical trials as well as future vaccine candidates. It covers peptides used in potential immunotherapies for infectious diseases including SARS-CoV-2, influenza, hepatitis B and C, HIV, malaria, and others. In addition, peptides for cancer vaccines that target examples of overexpressed proteins are summarized, including human epidermal growth factor receptor 2 (HER-2), mucin 1 (MUC1), folate receptor, and others. The uses of peptides to target cancers caused by infective agents, for example, cervical cancer caused by human papilloma virus (HPV), are also discussed. This review also provides an overview of model peptide epitopes used to stimulate non-specific immune responses, and of self-adjuvanting peptides, as well as the influence of other adjuvants on peptide formulations. As highlighted in this review, several peptide immunotherapies are in advanced clinical trials as vaccines, and there is great potential for future therapies due the specificity of the response that can be achieved using peptide epitopes.

Coiled Coil Crosslinked Alginate Hydrogels Dampen Macrophage-Driven Inflammation

Alginate hydrogels are widely used for tissue engineering and regenerative medicine due to their excellent biocompatibility. A facile and commonly used strategy to crosslink alginate is the addition of Ca²⁺ that leads to hydrogelation. However, extracellular Ca²⁺ is a secondary messenger in activating inflammasome pathways following physical injury or pathogenic insult, which carries the risk of persistent inflammation and scaffold rejection. Here, we present graft copolymers of charge complementary heterodimeric coiled coil (CC) peptides and alginate that undergo supramolecular self-assembly to form Ca²⁺ free alginate hydrogels. The formation of heterodimeric CCs was confirmed using circular dichroism spectroscopy, and scanning electron microscopy revealed a significant difference in crosslink density and homogeneity between Ca²⁺ and CC crosslinked gels. The resulting hydrogels were self-supporting and display shear-thinning and shear-recovery properties. In response to lipopolysaccharide (LPS) stimulation, peritoneal macrophages and bone marrow-derived dendritic cells cultured in the CC crosslinked gels exhibited a 10-fold reduction in secretion of the proinflammatory cytokine IL-1β compared to Ca²⁺ crosslinked gels. A similar response was also observed in vivo upon peritoneal delivery of Ca²⁺ or CC crosslinked gels. Analysis of peritoneal lavage showed that macrophages in mice injected with Ca²⁺ crosslinked gels display a more inflammatory phenotype compared to macrophages from mice injected with CC crosslinked gels. These results suggest that CC peptides by virtue of their tunable sequence-structure-function relationship and mild gelation conditions are promising alternative crosslinkers for alginate and other biopolymer scaffolds used in tissue engineering.

Self-Assembling Peptides as an Emerging Platform for the Treatment of Metabolic Syndrome

Metabolic syndrome comprises a cluster of comorbidities that represent a major risk of developing chronic diseases, such as type II diabetes, cardiovascular diseases, and stroke. Alarmingly, metabolic syndrome reaches epidemic proportions worldwide. Today, lifestyle changes and multiple drug-based therapies represent the gold standard to address metabolic syndrome. However, such approaches face two major limitations: complicated drug therapeutic regimes, which in most cases could lead to patient incompliance, and limited drug efficacy. This has encouraged scientists to search for novel routes to deal with metabolic syndrome and related diseases. Within such approaches, self-assembled peptide formulations have emerged as a promising alternative for treating metabolic syndrome. In particular, self-assembled peptide hydrogels, either as acellular or cell-load three-dimensional scaffoldings have reached significant relevance in the biomedical field to prevent and restore euglycemia, as well as for controlling cardiovascular diseases and obesity. This has been possible thanks to the physicochemical tunability of peptides, which are developed from a chemical toolbox of versatile amino acids enabling flexibility of designing a wide range of self-assembled/co-assembled nanostructures forming biocompatible viscoelastic hydrogels. Peptide hydrogels can be combined with several biological entities, such as extracellular matrix proteins, drugs or cells, forming functional biologics with therapeutic ability for treatment of metabolic syndrome-comorbidities. Additionally, self-assembly peptides combine safety, tolerability, and effectivity attributes; by this presenting a promising platform for the development of novel pharmaceuticals capable of addressing unmet therapeutic needs for diabetes, cardiovascular disorders and obesity. In this review, recent advances in developing self-assembly peptide nanostructures tailored for improving treatment of metabolic syndrome and related diseases will be discussed from basic research to preclinical research studies. Challenges facing the development of approved medicinal products based on self-assembling peptide nanomaterials will be discussed in light of regulatory requirement for clinical authorization.

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 T_H17 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.

Protein aggregation and immunogenicity of biotherapeutics

Recombinant proteins are the mainstay of biopharmaceuticals. A key challenge in the manufacturing and formulation of protein biologic products is the tendency for the active pharmaceutical ingredients to aggregate, resulting in irreversible drug loss, and an increase in immunogenicity risk. While the molecular mechanisms of protein aggregation have been discussed extensively in the literature, knowledge gaps remain in connecting the phenomenon in the context of immunogenicity of biotherapeutics. In this review, we discussed factors that drive aggregation of pharmaceutical recombinant proteins, and highlighted methods of prediction and mitigation that can be deployed through the development stages, from formulation to bioproduction. The purpose is to stimulate new dialogs that would bridge the interface between physical characterizations of protein aggregates in biotherapeutics and the functional attributes of the immune system.

Protein Supramolecular Structures: From Self-Assembly to Nanovaccine Design

Life-inspired protein supramolecular assemblies have recently attracted considerable attention for the development of next-generation vaccines to fight against infectious diseases, as well as autoimmune diseases and cancer. Protein self-assembly enables atomic scale precision over the final architecture, with a remarkable diversity of structures and functionalities. Self-assembling protein nanovaccines are associated with numerous advantages, including biocompatibility, stability, molecular specificity and multivalency. Owing to their nanoscale size, proteinaceous nature, symmetrical organization and repetitive antigen display, protein assemblies closely mimic most invading pathogens, serving as danger signals for the immune system. Elucidating how the structural and physicochemical properties of the assemblies modulate the potency and the polarization of the immune responses is critical for bottom-up design of vaccines. In this context, this review briefly covers the fundamentals of supramolecular interactions involved in protein self-assembly and presents the strategies to design and functionalize these assemblies. Examples of advanced nanovaccines are presented, and properties of protein supramolecular structures enabling modulation of the immune responses are discussed. Combining the understanding of the self-assembly process at the molecular level with knowledge regarding the activation of the innate and adaptive immune responses will support the design of safe and effective nanovaccines.

Rabies Vaccine Characterization by Nanoparticle Tracking Analysis

There are concerns that effectiveness and consistency of biopharmaceutical formulations, including vaccines, may be compromised by differences in size, concentration and shape of particles in suspension. Thus, a simple method that can help monitor and characterize these features is needed. Here, nanoparticle tracking analysis (NTA) was used to characterize particle concentration and size distribution of a highly-purified rabies vaccine (RABV), produced in Vero cells without raw materials of animal origin (RMAO). The NTA technique was qualified for characterization of RABV particles by assessing the stability profile of vaccine particles over 5-55 °C. Antigenicity of the viral particle was also monitored with the enzyme-linked immunosorbent assay (ELISA) and NTA. RABV particle size diameters were 100-250 nm (mean:150 nm), similar to sizes obtained when labelled with rabies anti-G D1-25 monoclonal antibody, suggesting mainly antigenic virus-like particles, also confirmed by transmission electron microscopy. Thermal stress at 55 °C decreased the concentration of anti-G D1-25-labelled particles from 144 hours, coherent with conformational changes leading to loss of G protein antigenicity without impacting aggregation. Results from RABV antigenicity assessment during the 24 months monitoring of stability showed good correlation between NTA and ELISA. NTA is a suitable approach for the characterization of biopharmaceutical suspensions.

Protein and Peptide Biomaterials for Engineered Subunit Vaccines and Immunotherapeutic Applications

Although vaccines have been the primary defense against widespread infectious disease for decades, there is a critical need for improvement to combat complex and variable diseases. More control and specificity over the immune response can be achieved by using only subunit components in vaccines. However, these often lack sufficient immunogenicity to fully protect, and conjugation or carrier materials are required. A variety of protein and peptide biomaterials have improved effectiveness and delivery of subunit vaccines for infectious, cancer, and autoimmune diseases. They are biodegradable and have control over both material structure and immune function. Many of these materials are built from naturally occurring self-assembling proteins, which have been engineered for incorporation of vaccine components. In contrast, others are de novo designs of structures with immune function. In this review, protein biomaterial design, engineering, and immune functionality as vaccines or immunotherapies are discussed.

Extracellular Matrix-Based Strategies for Immunomodulatory Biomaterials Engineering

The extracellular matrix (ECM) is a complex and dynamic structural scaffold for cells within tissues and plays an important role in regulating cell function. Recently it has become appreciated that the ECM contains bioactive motifs that can directly modulate immune responses. This review describes strategies for engineering immunomodulatory biomaterials that utilize natural ECM-derived molecules and have the potential to harness the immune system for applications ranging from tissue regeneration to drug delivery. A top-down approach utilizes full-length ECM proteins, including collagen, fibrin, or hyaluronic acid-based materials, as well as matrices derived from decellularized tissue. These materials have the benefit of maintaining natural conformation and structure but are often heterogeneous and encumber precise control. By contrast, a bottom-up approach leverages immunomodulatory domains, such as Arg-Gly-Asp (RGD), matrix metalloproteinase (MMP)-sensitive peptides, or leukocyte-associated immunoglobulin-like receptor-1(LAIR-1) ligands, by incorporating them into synthetic materials. These materials have tunable control over immune cell functions and allow for combinatorial approaches. However, the synthetic approach lacks the full natural context of the original ECM protein. These two approaches provide a broad range of engineering techniques for immunomodulation through material interactions and hold the potential for the development of future therapeutic applications.

Incorporation of ORF2 from Porcine Circovirus Type 2(PCV2) into genetically encoded nanoparticles as a novel vaccine using a self-aggregating peptide

Porcine Circovirus Type 2 (PCV2) is one of the most important pathogens in pigs around the world. PCV2 is a non-enveloped virus and its capsid is formed by a single protein known as open reading frame 2 (ORF2). The aim of this study was to evaluate the antigenicity and immunogenicity of genetically-encoded protein nanoparticles (NPs) containing ORF2 from PCV2 fused to the first 110 amino acids of the N-terminus of polyhedrin from the insect virus Autographa californica nucleopolyhedrovirus (PH(1 -1 1 0)). Our group has previously described that some polyhedrin fragments self-aggregate forming polyhedra-like particles. We identified a self-aggregating signal within the first 110 amino acids from polyhedrin (PH(1 -1 1 0)). Fusing the ORF2 from PCV2 to the carboxyl terminus from PH(1 -1 1 0) results in the formation of NPs which incorporate the antigen of interest. Using this system we synthesized NPs containing PH(1 -1 1 0) fused to ORF2 (PH(1 -1 1 0)PCV2) and purify them to immunize pigs and evaluate the humoral immune response generated by these NPs comparing them to a commercially available vaccine. Pigs immunized with PH(1 -1 1 0)PCV2 NPs produced antibodies against ORF2 from PCV2 as indicated by western blot and ELISA analysis. Antibodies obtained with PH(1 -1 1 0)PCV2 NPs were comparable to those obtained using a commercial PCV2 vaccine. These antibodies neutralized the infection of a recombinant PCV2 expressing the green fluorescent protein (GFP). These results together suggest that the self-aggregating peptide PH(1 -1 1 0) can be used for the synthesis of subunit vaccines against PCV2.

Ovalbumin Epitope SIINFEKL Self-Assembles into a Supramolecular Hydrogel

Here we show that the well-known ovalbumin epitope SIINFEKL that is routinely used to stimulate ovalbumin-specific T cells and to test new vaccine adjuvants can form a stable hydrogel. We investigate properties of this hydrogel by a range of spectroscopic and imaging techniques demonstrating that the hydrogel is stabilized by self-assembly of the peptide into nanofibres via stacking of β-sheets. As peptide hydrogels are known to stimulate an immune response as adjuvants, the immunoactive properties of the SIINFEKL peptide may also originate from its propensity to self-assemble into a hydrogel. This finding requires a re-evaluation of this epitope in adjuvant testing.

OVX836 a recombinant nucleoprotein vaccine inducing cellular responses and protective efficacy against multiple influenza A subtypes

Inactivated influenza vaccines (IIVs) lack broad efficacy. Cellular immunity to a conserved internal antigen, the nucleoprotein (NP), has been correlated to protection against pandemic and seasonal influenza and thus could have the potential to broaden vaccine efficacy. We developed OVX836, a recombinant protein vaccine based on an oligomerized NP, which shows increased uptake by dendritic cells and immunogenicity compared with NP. Intramuscular immunization in mice with OVX836 induced strong NP-specific CD4+ and CD8+ T-cell systemic responses and established CD8+ tissue memory T cells in the lung parenchyma. Strikingly, OVX836 protected mice against viral challenge with three different influenza A subtypes, isolated several decades apart and induced a reduction in viral load. When co-administered with IIV, OVX836 was even more effective in reducing lung viral load.

Circulating influenza A virus (IAV) strains differ in their surface proteins each year, and vaccines eliciting an immune response to these proteins are often only partially protective. Internal viral proteins, such as the nucleoprotein (NP), are highly conserved, and cellular immunity to NP has been correlated with protection from diverse strains. However, current IAV vaccines induce a poor immune response to NP. In this study, led by Fergal Hill from Osivax, researchers develop an oligomeric version of NP with improved immunogenicity. Vaccination of mice with oligomeric NP results in an improved NP-specific T-cell response, including CD8⁺ tissue memory T cells in the lung, and protects mice against three different IAV subtypes. Co-administration with the currently used inactivated influenza vaccine further improves protection against virus infection in mice. These results encourage further pre-clinical and clinical development for this vaccine candidate.

Stimuli-Responsive Supramolecular Hydrogels and Their Applications in Regenerative Medicine

Supramolecular hydrogels are a class of self-assembled network structures formed via non-covalent interactions of the hydrogelators. These hydrogels capable of responding to external stimuli are considered to be smart materials due to their ability to undergo sol-gel and/or gel-sol transition upon subtle changes in their surroundings. Such stimuli-responsive hydrogels are intriguing biomaterials with applications in tissue engineering, delivery of cells and drugs, modulating tissue environment to promote innate tissue repair, and imaging for medical diagnostics among others. This review summarizes the recent developments in stimuli-responsive supramolecular hydrogels and their potential applications in regenerative medicine. Specifically, various structural aspects of supramolecular hydrogelators involved in self-assembly, the role of external stimuli in tuning/controlling their phase transitions, and how these functions could be harnessed to advance applications in regenerative medicine are focused on. Finally, the key challenges and future prospects for these versatile materials are briefly described.

Nanoscale Peptide Self-assemblies Boost BCG-primed Cellular Immunity Against Mycobacterium tuberculosis

Bacillus Calmette-Guerin (BCG) is the only vaccine against TB and has limited protection efficacy, which wanes past adolescence. Multifunctional CD8+ T cells (IFN-γ+/TNF-α+/IL-2+) are associated with lower reactivation risk and enhanced control of active Mtb infection. Since boosting with BCG is contraindicated, booster vaccines that augment T cell immunity in the lungs of BCG-vaccinated individuals are urgently needed. We developed a vaccination strategy based on self-assembling peptide nanofibers presenting Mtb-specific CD8+ or CD4+ T cell epitopes that induce high frequency and antigen-specific effector memory T cells producing IFN-γ and IL-2. Intranasal immunization with peptide nanofibers was well tolerated in mice leading to increased antigen-specific CD8+ T cell population in the lungs. Co-assembled nanofibers of CD8+ T cell epitopes and toll-like receptor 2 (TLR2) agonists induced a 8-fold expansion in multifunctional CD8+ T cell populations in the lungs of vaccinated mice. Aerosol challenge with Mtb in BCG-primed and nanofiber-boosted mice provided an additional 0.5-log CFU reduction in lung bacterial load and indicating enhanced protection compared to BCG alone. Together, these data suggest that heterologous prime-boost with BCG and peptide nanofiber vaccines induces cell mediated immunity in the lung, reduces bacterial burden, and is a potentially safer alternative for boosting BCG-primed immunity.

Induction of adaptive immune response by self-aggregating peptides

INTRODUCTION

Recently, subunit vaccines are replacing some of the traditional vaccines because they offer a higher margin of safety. However, generally subunit vaccines have low antigenicity. Adjuvants are used in vaccine formulations to increase their immunogenicity, but current research suggests that adjuvants could induce serious side effects in susceptible individuals; therefore, the improvement of antigens and adjuvants is important.

AREAS COVERED

Here we reviewed some self-aggregating peptides (SAPs) used as antigen delivery systems. SAPs are based on a short sequence of amino acids, which have self-aggregating properties, inducing self-interaction among peptide molecules by means of non-covalent interactions to generate nanoparticles (NPs).

EXPERT COMMENTARY

SAPs increase the immunogenicity of fused/conjugated antigens because they can interact with antigen-presenting cells and induce adaptive immunity based on both humoral and cellular responses. As an example, we report an antigen delivery system based on SAPs forming NPs. These NPs are synthesized using a recombinant baculovirus. We fused the green fluorescent protein to the first 110 amino acids of polyhedrin protein from Autographa californica nucleopolyhedrovirus, which has self-aggregating properties. We showed that these NPs prompt high antibody levels without inducing inflammation, similarly to some SAPs reported here.

Biophysical virus particle specific characterization to sharpen the definition of virus stability

Vaccine thermostability is key to successful global immunization programs as it may have a significant impact on the continuous cold-chain maintenance logistics, as well as affect vaccine potency. Modern biological and biophysical techniques were combined to in-depth characterize the thermostability of a formulated rabies virus (RABV) in terms of antigenic and genomic titer, virus particle count and aggregation state. Tunable resistive pulse sensing (TRPS) and nanoparticle tracking analysis (NTA) were used to count virus particles while simultaneously determining their size distribution. RABV antigenicity was assessed by NTA using a monoclonal antibody that recognize a rabies glycoprotein (G protein) conformational epitope, enabling to specifically count antigenic rabies viruses. Agreement between antigenicity results from NTA and conventional method, as ELISA, was demonstrated. Additionally, NTA and ELISA showed mirrored loss of RABV antigenicity during forced degradation studies performed between 5 °C and 45 °C temperature exposure for one month. Concomitant with decreased antigenicity, emergence of RABV particle populations larger than those expected for rabies family viruses was observed, suggesting RABV aggregation induced by thermal stress. Finally, using a kinetic-based modeling approach to explore forced degradation antigenicity data (NTA, ELISA), a two-step model accurately describing antigenicity loss was identified. This model predicted a RABV shelf-life of more than 3 years at 5 °C; significant loss of antigenicity was predicted for samples maintained several months at ambient temperature. This thorough characterization of RABV forced degradation study originally provided a time-temperature mapping of RABV stability.

Microwave-Assisted Synthesis and Immunological Evaluation of Self-Assembling Peptide Vaccines

Self-assembling peptides spontaneously associate into functional supramolecular scaffolds, which have found numerous biomedical applications. These molecular assemblies have applications in nerve regeneration, wound healing, and both prophylactic and therapeutic vaccination. They can also be useful tools for proliferation assays, sustained culture of difficult cell lines, or activation of cell lines for immunoassays. This protocol will describe the basic peptide synthesis and purification of model self-assembling peptide immunogen and methods for vaccinating mice, collecting lymph nodes, and stimulating cells ex vivo.

Synthesis of sheet-coil-helix and coil-sheet-helix triblock copolymers by combining ROMP with palladium-mediated isocyanide polymerization

A new methodology towards architecturally well-defined covalent triblock copolymers is presented.

Biomaterials Made from Coiled-Coil Peptides

The development of biomaterials designed for specific applications is an important objective in personalized medicine. While the breadth and prominence of biomaterials have increased exponentially over the past decades, critical challenges remain to be addressed, particularly in the development of biomaterials that exhibit highly specific functions. These functional properties are often encoded within the molecular structure of the component molecules. Proteins, as a consequence of their structural specificity, represent useful substrates for the construction of functional biomaterials through rational design. This chapter provides an in-depth survey of biomaterials constructed from coiled-coils, one of the best-understood protein structural motifs. We discuss the utility of this structurally diverse and functionally tunable class of proteins for the creation of novel biomaterials. This discussion illustrates the progress that has been made in the development of coiled-coil biomaterials by showcasing studies that bridge the gap between the academic science and potential technological impact.

D-amino acid-containing supramolecular nanofibers for potential cancer therapeutics

Nanostructures formed by peptides that self-assemble in water through non-covalent interactions have attracted considerable attention because peptides possess several unique advantages, such as modular design and easiness of synthesis, convenient modification with known functional motifs, good biocompatibility, low immunogenicity and toxicity, inherent biodegradability, and fast responses to a wide range of external stimuli. After about two decades of development, peptide-based supramolecular nanostructures have already shown great potentials in the fields of biomedicine. Among a range of biomedical applications, using such nanostructures for cancer therapy has attracted increased interests since cancer remains the major threat for human health. Comparing with L-peptides, nanostructures containing peptides made of D-amino acid (i.e., D-peptides) bear a unique advantage, biostability (i.e., resistance towards most of endogenous enzymes). The exploration of nanostructures containing D-amino acids, especially their biomedical applications, is still in its infancy. Herein we review the recent progress of D-amino acid-containing supramolecular nanofibers as an emerging class of biomaterials that exhibit unique features for the development of cancer therapeutics. In addition, we give a brief perspective about the challenges and promises in this research direction.

Drug delivery by supramolecular design

Principles rooted in supramolecular chemistry have empowered new and highly functional therapeutics and drug delivery devices. This general approach offers elegant tools rooted in molecular and materials engineered to address the many challenges faced in treating disease.

Drug-Free Macromolecular Therapeutics--A New Paradigm in Polymeric Nanomedicines

This review highlights a unique research area in polymer-based nanomedicine designs. Drug-free macromolecular therapeutics induce apoptosis of malignant cells by the crosslinking of surface non-internalizing receptors. The receptor crosslinking is mediated by the biorecognition of high-fidelity natural binding motifs (such as antiparallel coiled-coil peptides or complementary oligonucleotides) that are grafted to the side chains of polymers or attached to targeting moieties against cell receptors. This approach features the absence of low-molecular-weight cytotoxic compounds. Here, we summarize the rationales, different designs, and advantages of drug-free macromolecular therapeutics. Recent developments of novel therapeutic systems for B-cell lymphomas are discussed, as well as relevant approaches for other diseases. We conclude by pointing out various potential future directions in this exciting new field.

α-Helical coiled-coil peptide materials for biomedical applications

Self-assembling coiled coils, which occur commonly in native proteins, have received significant interest for the design of new biomaterials-based medical therapies. Considerable effort over recent years has led to a detailed understanding of the self-assembly process of coiled coils, and a diverse collection of strategies have been developed for designing functional materials using this motif. The ability to engineer the interface between coiled coils allows one to achieve variously connected components, leading to precisely defined structures such as nanofibers, nanotubes, nanoparticles, networks, gels, and combinations of these. Currently these materials are being developed for a range of biotechnological and medical applications, including drug delivery systems for controlled release, targeted nanomaterials, 'drug-free' therapeutics, vaccine delivery systems, and others. WIREs Nanomed Nanobiotechnol 2017, 9:e1424. doi: 10.1002/wnan.1424 For further resources related to this article, please visit the WIREs website.

Relationship between the magnitude of IgE production in mice and conformational stability of the house dust mite allergen, Der p 2

BACKGROUND

Protein antigens are degraded by endosomal protease in antigen presentation cell. T cells recognize peptides derived from antigen proteins bound to class II major histocompatibility complex molecules. We previously reported that an increase in the conformational stability of an antigen depressed its immunogenicity. However, there is little information on antigens with differences in molecular properties such as net charges and molecular weight.

METHODS

Denaturation experiments against guanidine hydrochloride. The serum IgE levels to protein antigens at 35days after the first immunization analyzed using ELISA.

RESULTS

The Der p 2 mutations in which Ile13 is mutated to Ala (I13A) and Ala122 is mutated to Ile (A122I) were shown to have lower and higher conformational stability than the wild-type, respectively, by denaturation experiments. The amount of IgE production by the less stable I13A mutant was higher and that of the stable A122I mutant was lower than that of the wild-type.

CONCLUSION

Our results suggest that the increased conformational stability of Der p 2 depressed the IgE production in mice.

GENERAL SIGNIFICANCE

These findings should provide a milestone for the engineering of allergen vaccines.

Strain-transcending immune response generated by chimeras of the malaria vaccine candidate merozoite surface protein 2

MSP2 is an intrinsically disordered protein that is abundant on the merozoite surface and essential to the parasite Plasmodium falciparum. Naturally-acquired antibody responses to MSP2 are biased towards dimorphic sequences within the central variable region of MSP2 and have been linked to naturally-acquired protection from malaria. In a phase IIb study, an MSP2-containing vaccine induced an immune response that reduced parasitemias in a strain-specific manner. A subsequent phase I study of a vaccine that contained both dimorphic forms of MSP2 induced antibodies that exhibited functional activity in vitro. We have assessed the contribution of the conserved and variable regions of MSP2 to the generation of a strain-transcending antibody response by generating MSP2 chimeras that included conserved and variable regions of the 3D7 and FC27 alleles. Robust anti-MSP2 antibody responses targeting both conserved and variable regions were generated in mice, although the fine specificity and the balance of responses to these regions differed amongst the constructs tested. We observed significant differences in antibody subclass distribution in the responses to these chimeras. Our results suggest that chimeric MSP2 antigens can elicit a broad immune response suitable for protection against different strains of P. falciparum.

Assessing cellular response to functionalized α-helical peptide hydrogels

α-Helical peptide hydrogels are decorated with a cell-binding peptide motif (RGDS), which is shown to promote adhesion, proliferation, and differentiation of PC12 cells. Gel structure and integrity are maintained after functionalization. This opens possibilities for the bottom-up design and engineering of complex functional scaffolds for 2D and 3D cell cultures.

3-D self-assembling leucine zipper hydrogel with tunable properties for tissue engineering

Peptide-based engineered hydrogel scaffolds present several advantages over traditional protein or polymeric hydrogels by imparting more robust control over hydrogel properties. In this manuscript, we report the synthesis and characterization of a leucine zipper (LZ) based self-assembling hydrogel for use in tissue engineering applications. Although, LZ hydrogels posses several advantages, the stability of these hydrogels has always been elusive. In this study, we have standardized the procedure for creating a stable LZ hydrogel. Pore-size was tunable by altering the peptide concentration from 7% to 12% by weight. In order to create a microenvironment for cell adhesion, the LZ polypeptide was functionalized by the incorporation of the cell attachment RGD domain. In vivo implantation of the LZ scaffolds in a mouse model showed absence of foreign body reaction to the scaffold. In vivo experiments with human marrow stem cells (HMSCs) in immunocompromised mice showed the biological property of the hydrogel to promote cell attachment, proliferation and its ability to support neovascularization. Our results show for the first time, that it is possible to generate a functional and stable LZ scaffold that can be used in vivo for tissue engineering applications.

Sequence effects of self-assembling multidomain peptide hydrogels on encapsulated SHED cells

Here we report three new nanofibrous, self-assembling multidomain peptide (MDP) sequences and examine the effect of sequence on the morphology and expansion of encapsulated Stem cells from Human Exfoliated Deciduous teeth (SHED). We modified our previously reported set of serine-based MDPs, changing the serine residues in the amphiphilic region to threonine. The three new threonine-based sequences self-assemble into antiparallel β-sheet nanofibers, confirmed by CD and IR. AFM and negative-stained TEM show that the nanofibers formed by the new sequences are more curved than their serine-containing predecessors. Despite this change in nanofiber morphology, SEM illustrates that all three new sequences still form porous hydrogels. K(TL)2SLRG(TL)3KGRGDS, with a designed cleavage site, is able to be degraded by Matrix Metalloprotease 2. We then examine SHED cell response to these new sequences as well as their serine-based predecessors. We observe faster cell attachment and spreading in hydrogels formed by K2(SL)6K2GRGDS and K(SL)3RG(SL)3KGRGDS. By day 3, the SHEDs in all of the serine-based sequences exhibit a fibroblast-like morphology. Additionally, the SHED cells expand more rapidly in the serine-based gels while the cell number remains relatively constant in the threonine-based peptides. In hydrogels formed by K2(TL)6K2GRGDS and K(TL)2SLRG(TL)3KGRGDS, this low expansion rate is accompanied by changes in morphology where SHEDs exhibit a stellate morphology after 3 days in culture; however, by day 7 they appear more fibroblast-shaped. Throughout the duration of the experiment, the SHED cells encapsulated in the K2(TL)6K2 hydrogels remain rounded. These results suggest that the basic MDP structure easily accommodates modifications in sequence and, for SHED cells, the threonine-containing gels require the integrin-binding RGDS sequence for cell attachment to occur, while the serine-based gels are less selective and support an increase in cell number, regardless of the presence or absence of RGDS.

Immunogenicity of coiled-coil based drug-free macromolecular therapeutics

A two-component CD20 (non-internalizing) receptor crosslinking system based on the biorecognition of complementary coiled-coil forming peptides was evaluated. Exposure of B cells to Fab'-peptide1 conjugate decorates the cell surface with peptide1; further exposure of the decorated cells to P-(peptide2)x (P is the N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer backbone) results in the formation of coiled-coil heterodimers at the cell surface with concomitant induction of apoptosis. The aim of this study was to determine the potential immunogenicity of this therapeutic system that does not contain low molecular weight drugs. Enantiomeric peptides (L- and D-CCE and L- and D-CCK), HPMA copolymer-peptide conjugates, and Fab' fragment-peptide conjugates were synthesized and the immunological properties of peptide conjugates evaluated in vitro on RAW264.7 macrophages and in vivo on immunocompetent BALB/c mice. HPMA copolymer did not induce immune response in vitro and in vivo. Administration of P-peptide conjugates with strong adjuvant resulted in antibody response directed to the peptide. Fab' was responsible for macrophage activation of Fab'-peptide conjugates and a major factor in the antibody induction following i.v. administration of Fab'-conjugates. There was no substantial difference in the ability of conjugates of D-peptides and conjugates of L-peptides to induce Ab response.

Designing ECM-mimetic materials using protein engineering

The natural extracellular matrix (ECM), with its multitude of evolved cell-instructive and cell-responsive properties, provides inspiration and guidelines for the design of engineered biomaterials. One strategy to create ECM-mimetic materials is the modular design of protein-based engineered ECM (eECM) scaffolds. This modular design strategy involves combining multiple protein domains with different functionalities into a single, modular polymer sequence, resulting in a multifunctional matrix with independent tunability of the individual domain functions. These eECMs often enable decoupled control over multiple material properties for fundamental studies of cell-matrix interactions. In addition, since the eECMs are frequently composed entirely of bioresorbable amino acids, these matrices have immense clinical potential for a variety of regenerative medicine applications. This brief review demonstrates how fundamental knowledge gained from structure-function studies of native proteins can be exploited in the design of novel protein-engineered biomaterials. While the field of protein-engineered biomaterials has existed for over 20years, the community is only now beginning to fully explore the diversity of functional peptide modules that can be incorporated into these materials. We have chosen to highlight recent examples that either (i) demonstrate exemplary use as matrices with cell-instructive and cell-responsive properties or (ii) demonstrate outstanding creativity in terms of novel molecular-level design and macro-level functionality.

Insights into low molecular mass organic gelators: a focus on drug delivery and tissue engineering applications

In recent years low molecular mass organic gelators (LMOGs) have gained increasing interest as an alternative biomaterial to polymer derived gels, with potential applications in drug delivery and tissue engineering. LMOGs are small organic molecules which self-assemble in water or organic solvents forming a 3D network that entraps the liquid phase resulting in gel formation. In this review, we report the classification of LMOGs into hydrogelators and gelators of organic solvents and we discuss the techniques commonly used to characterise the gels of these gelators with particular reference to specific applications of LMOGs in drug delivery and tissue engineering.

Immunogenicity of therapeutic proteins: influence of aggregation

The elicitation of anti-drug antibodies (ADA) against biotherapeutics can have detrimental effects on drug safety, efficacy, and pharmacokinetics. The immunogenicity of biotherapeutics is, therefore, an important issue. There is evidence that protein aggregation can result in enhanced immunogenicity; however, the precise immunological and biochemical mechanisms responsible are poorly defined. In the context of biotherapeutic drug development and safety assessment, understanding the mechanisms underlying aggregate immunogenicity is of considerable interest. This review provides an overview of the phenomenon of protein aggregation, the production of unwanted aggregates during bioprocessing, and how the immune response to aggregated protein differs from that provoked by non-aggregated protein. Of particular interest is the nature of the interaction of aggregates with the immune system and how subsequent ADA responses are induced. Pathways considered here include 'classical' activation of the immune system involving antigen presenting cells and, alternatively, the breakdown of B-cell tolerance. Additionally, methods available to screen for aggregation and immunogenicity will be described. With an increased understanding of aggregation-enhanced immune responses, it may be possible to develop improved manufacturing and screening processes to avoid, or at least reduce, the problems associated with ADA.

Short-peptide-based molecular hydrogels: novel gelation strategies and applications for tissue engineering and drug delivery

Molecular hydrogels hold big potential for tissue engineering and controlled drug delivery. Our lab focuses on short-peptide-based molecular hydrogels formed by biocompatible methods and their applications in tissue engineering (especially, 3D cell culture) and controlled drug delivery. This feature article firstly describes our recent progresses of the development of novel methods to form hydrogels, including the strategy of disulfide bond reduction and assistance with specific protein-peptide interactions. We then introduce the applications of our hydrogels in fields of controlled stem cell differentiation, cell culture, surface modifications of polyester materials by molecular self-assembly, and anti-degradation of recombinant complex proteins. A novel molecular hydrogel system of hydrophobic compounds that are only formed by hydrolysis processes was also included in this article. The hydrogels of hydrophobic compounds, especially those of hydrophobic therapeutic agents, may be developed into a carrier-free delivery system for long term delivery of therapeutic agents. With the efforts in this field, we believe that molecular hydrogels formed by short peptides and hydrophobic therapeutic agents can be practically applied for 3D cell culture and long term drug delivery in near future, respectively.

Immunogenicity of protein aggregates--concerns and realities

Protein aggregation is one of the key challenges in the development of protein biotherapeutics. It is a critical product quality issue as well as a potential safety concern due to the increased immunogenicity potential of these aggregates. The overwhelming safety concern has led to an increased development effort and regulatory scrutiny in recent years. The main purposes of this review are to examine the literature data on the relationship between protein aggregates and immunogenicity, to highlight the linkage and existing inconsistencies/uncertainties, and to propose directions for future investigations/development.

Materials from peptide assembly: towards the treatment of cancer and transmittable disease

As the prevalence of cancer and transmittable disease persists, the development of new and more advanced therapies remains a priority in medical research. An emerging platform for the treatment of these illnesses is the use of materials formed via peptide assembly where the bulk material itself acts as the therapeutic. Higher ordered peptide structures with defined chemistry are capable of cellular targeting, recognition, and internalization. Recent design efforts are being made to exploit the nanoscale definition of the materials formed by assembling peptides to target cancer and microbial cells and to function as vaccines. This review focuses on assembled peptide materials that actively participate in the biological processes important to cancer and transmittable diseases to exert an anticipated functional outcome.