Biomimetic Protein Nanoparticles Facilitate Enhanced Dendritic Cell Activation and Cross-Presentation

Abstract

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 non-viral 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 co-delivering peptide epitopes and CpG activator in a particle of optimal DC-uptake size, we demonstrate the ability of a non-infectious protein nanoparticle to mimic viral properties and facilitate enhanced DC activation and cross-presentation.

Viral-mimicking protein nanoparticle vaccine for eliciting anti-tumor responses

“…The D381C E2 protein nanoparticle (E2) was prepared and characterized as previously described [26,30]. D381C is an E2 mutant with a non-native cysteine introduced to the internal cavity of the nanoparticle at amino acid location 381 for site-specific conjugation.…”

“…Final protein preparations were stored in 50 mM potassium phosphate at pH 7.4 with 100 mM NaCl (phosphate buffer) at 4 °C for short-term and −80 °C for long-term storage. Residual LPS was removed using Triton X-114, and endotoxin levels were checked as previously described [30]. …”

“…It is also of non-viral origin and has been shown to be amenable to functionalization in biomedical applications [26–29]. Our research group has previously demonstrated significantly enhanced activation and cross-presentation of a model antigen using the E2 nanoparticle for delivery to and activation of DCs [30]. This increased activation, mediated by virus-mimicking E2 nanoparticles, may allow the immune system to overcome the low immunogenicity or tolerance to tumor antigens.…”

Protein nanoparticles as multifunctional biocatalysts and health assessment sensors

“…Chemical conjugation methods are often used to attach inorganic, non-proteinaceous components such as chemical dyes for imaging [28,35], targeting ligands for drug delivery [36], and peptides for immune activation [37]. Typically, well-characterized chemistries can be employed to couple substances to reactive side chains that are either surface exposed or genetically incorporated into the protein monomer backbone.…”

Emerging nanotechnologies for cancer immunotherapy

“…110 Such crosspresentation of cancer antigens have been demonstrated for a wide range of distinct nanoparticles and new strategies are being developed to improve the efficiency of such cross-presentation. [111][112][113] These include strategies employed for cytosolic drug delivery of membrane-impermeable molecules such as via endolysosomal disruption through the proton sponge effect using biodegradable nanogels, 114 endolysosomolytic and pH-responsive micelles, 115 as well as endoplasmic reticulum (ER) targeting approaches where nanoparticles shuttle to cytosol following endosome-ER fusion. 116 A significant advantage of nanoformulations is the control over their transport kinetics that facilitates tissue-specific delivery of antigens.…”