Peptide and protein-based cancer vaccines usually fail to elicit efficient immune responses against tumors. However, delivery of these peptides and proteins as components within caged protein ...nanoparticles has shown promising improvements in vaccine efficacy. Advantages of protein nanoparticles over other vaccine platforms include their highly organized structures and symmetry, biodegradability, ability to be specifically functionalized at three different interfaces (inside and outside the protein cage, and between subunits in macromolecular assembly), and ideal size for vaccine delivery. In this review, we discuss different classes of virus-like particles and caged protein nanoparticles that have been used as vehicles to transport and increase the interaction of cancer vaccine components with the immune system. We review the effectiveness of these protein nanoparticles towards inducing and elevating specific immune responses, which are needed to overcome the low immunogenicity of the tumor microenvironment.
In this review, we discuss several different protein-based nanoparticles as delivery vehicles to increase the interaction of cancer vaccine components (e.g., adjuvants, tumor-associated antigens) with the immune system. These important components can be efficiently internalized and processed by dendritic cells, which then present the antigen to the T cells for specific T cell responses that lead to specific tumor lysis and elimination. The elevated immune responses that are elicited by these nanoparticle vaccines are advantageous to overcome the low immunogenicity of the tumor microenvironment. Display omitted
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.
This review describes strategies for engineering immunomodulatory biomaterials that utilize natural extracellular matrix (ECM) derived molecules and have the potential to harness the immune system for applications ranging from tissue regeneration to drug delivery. The incorporation of full‐length ECM proteins, ECM‐derived peptides, or a mixture of both, into biomaterials provides a broad range of engineering techniques for immunomodulation through material interactions.
Infectious diseases are a major threat to global human health, yet prophylactic treatment options can be limited, as safe and efficacious vaccines exist only for a fraction of all diseases. Notably, ...devastating diseases such as acquired immunodeficiency syndrome (AIDS) and coronavirus disease of 2019 (COVID‐19) currently do not have vaccine therapies. Conventional vaccine platforms, such as live attenuated vaccines and whole inactivated vaccines, can be difficult to manufacture, may cause severe side effects, and can potentially induce severe infection. Subunit vaccines carry far fewer safety concerns due to their inability to cause vaccine‐based infections. The applicability of protein nanoparticles (NPs) as vaccine scaffolds is promising to prevent infectious diseases, and they have been explored for a number of viral, bacterial, fungal, and parasitic diseases. Many types of protein NPs exist, including self‐assembling NPs, bacteriophage‐derived NPs, plant virus‐derived NPs, and human virus‐based vectors, and these particular categories will be covered in this review. These vaccines can elicit strong humoral and cellular immune responses against specific pathogens, as well as provide protection against infection in a number of animal models. Furthermore, published clinical trials demonstrate the promise of applying these NP vaccine platforms, which include bacteriophage‐derived NPs, in addition to multiple viral vectors that are currently used in the clinic. The continued investigations of protein NP vaccine platforms are critical to generate safer alternatives to current vaccines, advance vaccines for diseases that currently lack effective prophylactic therapies, and prepare for the rapid development of new vaccines against emerging infectious diseases.
This article is categorized under:
Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease
Biology‐Inspired Nanomaterials > Protein and Virus‐Based Structures
Various protein nanoparticles (NPs) have been utilized as scaffolds to display antigens for vaccination against infectious agents. NPs can stimulate humoral immune responses, cellular immune responses, or a combination of both.
The E2 component of pyruvate dehydrogenase is engineered to form a caged, hollow dodecahedral protein assembly, and the feasibility of this scaffold to be used as a drug delivery system is examined ...by introducing cysteines to the internal cavity (D381C). The fluorescent dye Alexa Fluor 532 (AF532M) and the antitumor drug doxorubicin are coupled to this internal cavity through maleimides on the guest molecules. The viruslike particle’s structure and stability remain intact after binding of the molecules within the interior of the nanocapsule. The pH‐dependent hydrolysis of a hydrazone linkage to doxorubicin allows 90% drug release from the D381C scaffold within 72 h at pH 5.0. Fluorescence microscopy of MDA‐MB‐231 breast cancer cells indicates significant uptake of the D381C scaffold incorporating AF532M and doxorubicin, and suggests internalization of the nanoparticles through endocytosis. It is observed that the protein scaffold does not induce cell death, but doxorubicin encapsulated in D381C is indeed cytotoxic, yielding an IC50 of 1.3 ± 0.3 μM. While the majority of particulate‐based drug delivery strategies encapsulates drugs within polymeric nanoparticles, these results show the potential for using macromolecular protein assemblies. This approach yields a promising new opportunity for designing highly defined nanomaterials for therapeutic delivery.
Cells incubated with free doxorubicin and protein nanoparticle‐conjugated doxorubicin are imaged using confocal laser scanning microscopy, showing different internalization mechanisms and drug distributions.
•We fabricated biomimetic protein-based nanoparticles with both molecular encapsulation and cell-targeting capabilities using recombinant technology and chemical synthesis.•Functionalization of the ...protein nanoparticles’ external surface with folic acid increased their cellular uptake into cancer cells that overexpressed folate receptors.•Nanoparticles demonstrated acid-responsive drug release and were cytotoxic to cancer cells.•Our investigation demonstrates the potential of using biofabrication strategies to generate functional nanomaterials.
Nanomaterials that are used in therapeutic applications need a high degree of uniformity and functionality which can be difficult to attain. One strategy for fabrication is to utilize the biological precision afforded by recombinant synthesis. Through protein engineering, we have produced ∼27-nm dodecahedral protein nanoparticles using the thermostable E2 subunit of pyruvate dehydrogenase as a scaffold and added optical imaging, drug delivery, and tumor targeting capabilities. Cysteines in the internal cavity of the engineered caged protein scaffold (E2 variant D381C) were conjugated with maleimide-bearing Alexa Fluor 532 (AF532) and doxorubicin (DOX). The external surface was functionalized with polyethylene glycol (PEG) alone or with the tumor-targeting ligand folic acid (FA) through a PEG linker. The resulting bi-functional nanoparticles remained intact and correctly assembled. The uptake of FA-displaying nanoparticles (D381C-AF532-PEG-FA) by cells overexpressing the folate receptor was approximately six times greater than of non-targeting nanoparticles (D381C-AF532-PEG) and was confirmed to be FA-specific. Nanoparticles containing DOX were all cytotoxic in the low micromolar range. To our knowledge, this work is the first time that acid-labile drug release and folate receptor targeting have been simultaneously integrated onto recombinant protein nanoparticles, and it demonstrates the potential of using biofabrication strategies to generate functional nanomaterials.
Many current cancer vaccine strategies suffer from the inability to mount a CD8 T cell response that is strong enough to overcome the low immunogenicity of tumors. Viruses naturally possess the ...sizes, geometries, and physical properties for which the immune system has evolved to recognize, and mimicking those properties with nanoparticles can produce robust platforms for vaccine design. Using the nonviral E2 core of pyruvate dehydrogenase, we have engineered a viral-mimicking vaccine platform capable of encapsulating dendritic cell (DC)-activating CpG molecules in an acid-releasable manner and displaying MHC I-restricted SIINFEKL peptide epitopes. Encapsulated CpG activated bone marrow-derived DCs at a 25-fold lower concentration in vitro when delivered with the E2 nanoparticle than with unbound CpG alone. Combining CpG and SIINFEKL within a single multifunctional particle induced ∼3-fold greater SIINFEKL display on MHC I by DCs over unbound peptide. Importantly, combining CpG and SIINFEKL to the E2 nanoparticle for simultaneous temporal and spatial delivery to DCs showed increased and prolonged CD8 T cell activation, relative to free peptide or peptide-bound E2. By codelivering peptide epitopes and CpG activator in a particle of optimal DC-uptake size, we demonstrate the ability of a noninfectious protein nanoparticle to mimic viral properties and facilitate enhanced DC activation and cross-presentation.
We report here a new strategy to enable fast, covalent, and site-directed functionalization of protein nanoparticles using Sortase A-mediated ligation using functional proteins ranging from monomeric ...to large tetrameric structures. Easy purification of the modified E2 nanoparticles is achieved by functionalization with a thermo-responsive elastin-like-peptide. The resulting protein nanoparticles remained intact and active even after repeated phase transitions, suggesting their use in biocatalysis, biosensing, and imaging applications.
Since the outbreak of Severe Acute Respiratory Syndrome Virus-2 (SARS-CoV-2) in 2019, more than 15 million spike protein sequences have been identified, raising a new challenge for the development of ...a broadly protective vaccine against the various emerging variants. We found that the virus, like most other human viruses, depends on host-made glycans to shield the conserved epitopes on spike protein from immune response and demonstrated that deletion of the glycan shields exposed highly conserved epitopes and elicited broadly protective immune responses. In this study, we identified 17 conserved epitopes from 14 million spike protein sequences and 11 of the conserved epitopes are in the S2 domain, including the six most conserved epitopes in the stem region. We also demonstrated that deletion of the glycosites in the spike messenger RNA (mRNA) S2 domain or the stem region exposed the highly conserved epitopes and elicited broadly protective immune responses, particularly CD-8
T cell response against various SARS-CoV-2 variants, and other human coronaviruses including MERS, SARS viruses, and those causing common cold.
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