A novel antigen delivery system induces strong humoral and CTL immune responses

RBC-hitchhiking PLGA nanoparticles loading β-glucan as a delivery system to enhance in vitro and in vivo immune responses in mice

Red blood cells (RBCs) naturally trap some bacterial pathogens in the circulation and kill them by oxidative stress. Following neutralization, the bacteria are presented to antigen-presenting cells in the spleen by the RBCs. This ability of RBCs has been harnessed to develop a system where they play a crucial role in enhancing the immune response, offering a novel approach to enhance the body's immunity. In this work, a conjugate, G-OVA, was formed by connecting β-glucan and OVA through a disulfide bond. Poly (lactic-co-glycolic acid) (PLGA) was then employed to encapsulate G-OVA, yielding G-OVA-PLGA. Finally, the nanoparticles were adsorbed onto RBCs to develop G-OVA-PLGA@RBC. The results demonstrated that the delivery of nanoparticles by RBCs enhanced the antibody response to antigens both in vitro and in vivo. The objective of this study was to investigate the increased immune activity of G-OVA-PLGA nanoparticles facilitated by RBCs transportation and to elucidate some of its underlying mechanisms. These findings are anticipated to contribute valuable insights for the development of efficient and safe immune enhancers.

A Bionic Yeast Tumor Vaccine Using the Co-Loading Strategy to Prevent Post-Operative Tumor Recurrence

Immunotherapy is an effective adjunct to surgery for preventing tumor recurrence and metastasis in postoperative tumor patients. Although mimicking microbial invasion and immune activation pathways can effectively stimulate the immune system, the limited capacity of microbial components to bind antigens and adjuvants restricts the development of this system. Here, we construct bionic yeast carriers (BYCs) by in situ polymerization of mesoporous silica nanoparticles (MSNs) within the yeast capsules (YCs). BYCs can mimic the yeast infection pathway while utilizing the loading capacity of MSNs for multiple substances. Pore size and hydrophobicity-modified BYC can be loaded with both antigen and adjuvant R848. Oral or subcutaneous injection uptake of coloaded BYCs demonstrated positive therapeutic effects as a tumor therapeutic vaccine in both the transplantation tumor model and the metastasis tumor model. 57% of initial 400 mm3 tumor recurrence models are completely cured with coloaded BYCs via combination therapy with surgery, utilizing surgically resected tumors as antigens. The BYCs construction and coloading strategy will provide insights and optimistic approaches for the development of effective and controllable cancer vaccine carriers.

A vaccine delivery system promotes strong immune responses against SARS-CoV-2 variants

Global coronavirus disease 2019 (COVID-19) pandemics highlight the need of developing vaccines with universal and durable protection against emerging SARS-CoV-2 variants. Here we developed an extended-release vaccine delivery system (GP-diABZI-RBD), consisting the original SARS-CoV-2 WA1 strain receptor-binding domain (RBD) as the antigen and diABZI stimulator of interferon genes (STING) agonist in conjunction with yeast β-glucan particles (GP-diABZI) as the platform. GP-diABZI-RBD could activate STING pathway and inhibit SARS-CoV-2 replication. Compared to diABZI-RBD, intraperitoneal injection of GP-diABZI-RBD elicited robust cellular and humoral immune responses in mice. Using SARS-CoV-2 GFP/ΔN transcription and replication-competent virus-like particle system (trVLP), we demonstrated that GP-diABZI-RBD-prototype vaccine exhibited the strongest and durable humoral immune responses and antiviral protection; whereas GP-diABZI-RBD-Omicron displayed minimum neutralization responses against trVLP. By using pseudotype virus (PsVs) neutralization assay, we found that GP-diABZI-RBD-Prototype, GP-diABZI-RBD-Delta, and GP-diABZI-RBD-Gamma immunized mice sera could efficiently neutralize Delta and Gamma PsVs, but had weak protection against Omicron PsVs. In contrast, GP-diABZI-RBD-Omicron immunized mice sera displayed the strongest neutralization response to Omicron PsVs. Taken together, the results suggest that GP-diABZI can serve as a promising vaccine delivery system for enhancing durable humoral and cellular immunity against broad SARS-CoV-2 variants. Our study provides important scientific basis for developing SARS-CoV-2 VOC-specific vaccines.

A Potent Micron Neoantigen Tumor Vaccine GP-Neoantigen Induces Robust Antitumor Activity in Multiple Tumor Models

Therapeutic tumor neoantigen vaccines have been widely studied given their good safety profile and ability to avoid central thymic tolerance. However, targeting antigen-presenting cells (APCs) and inducing robust neoantigen-specific cellular immunity remain challenges. Here, a safe and broad-spectrum neoantigen vaccine delivery system is proposed (GP-Neoantigen) based on β-1,3-glucan particles (GPs) derived from Saccharomyces cerevisiae and coupling peptide antigens with GPs through convenient click chemistry. The prepared system has a highly uniform particle size and high APC targeting specificity. In mice, the vaccine system induced a robust specific CD8⁺ T cell immune response and humoral immune response against various conjugated peptide antigens and showed strong tumor growth inhibitory activity in EG7·OVA lymphoma, B16F10 melanoma, 4T1 breast cancer, and CT26 colon cancer models. The combination of the toll-like receptors (TLRs) agonist PolyI:C and CpG 2395 further enhanced the antitumor response of the particle system, achieving complete tumor clearance in multiple mouse models and inducing long-term rejection of reinoculated tumors. These results provide the broad possibility for its further clinical promotion and personalized vaccine treatment.

Polyethyleneimine-complexed charge-reversed yeast cell walls for the enhanced oral delivery of pseudovirus-based antigens

Oral vaccination has wide applicability in poor areas, particularly during the epidemic periods of infectious diseases. However, successful oral antigen delivery and immune activation remain highly challenging due to the instability of vaccines in gastric acid and the low capture of antigens in the intestine. Here, we present a facile approach for the preparation of a robust oral delivery system via encapsulating antigen-carrying pseudoviruses inside positively charged polyethyleneimine-modified yeast capsules (P-YC). By virtue of the physical barrier role and surface β-glucan of YC, encapsulated pseudoviruses can be protected from gastric insult and delivered into Peyer's patches via uptake mediated by microfold cells located in the intestinal epithelium. Given the ability to carry diverse antigens, the enhanced oral delivery of pseudoviruses achieved by P-YC provides a versatile platform for the development of various oral vaccines.

Yeast Shells Encapsulating Adjuvant AS04 as an Antigen Delivery System for a Novel Vaccine against Toxoplasma Gondii

Toxoplasma gondii (T. gondii) infection causes severe zoonotic toxoplasmosis, which threatens the safety of almost one-third of the human population globally. However, there is no effective protective vaccine against human toxoplasmosis. This necessitates anti-T. gondii vaccine development, which is a main priority of public health. In this study, we optimized the adjuvant system 04 (AS04), a vaccine adjuvant constituted by 3-O-desacyl-4'-monophosphoryl lipid A (a TLR4 agonist) and aluminum salts, by packing it within natural extracts of β-glucan particles (GPs) from Saccharomyces cerevisiae to form a GP-AS04 hybrid adjuvant system. Through a simple mixing procedure, we loaded GP-AS04 particles with the total extract (TE) of T. gondii lysate, forming a novel anti-T. gondii vaccine GP-AS04-TE. Results indicated that the hybrid adjuvant can efficiently and stably load antigens, mediate antigen delivery, facilitate the dendritic uptake of antigens, boost dendritic cell maturation and stimulation, and increase the secretion of pro-inflammatory cytokines. In the mouse inoculation model, GP-AS04-TE significantly stimulated the function of dendritic cells, induced a very strong TE-specific humoral and cellular immune response, and finally showed a strong and effective protection against toxoplasma chronic and acute infections. This work proves the potential of GP-AS04 for exploitation as a vaccine against a range of pathogens.

Preparation of a water soluble aminated β-1,3-D-glucan for gene carrier: The in vitro study of the anti-inflammatory activity and transfection efficiency

β-1,3-D-glucan has been reported to have a series of bioactivities including antitumor, antimicrobial, anti-inflammatory and antioxidative effects; however, its insolubility in neutral aqueous solution significantly restricts the potential application in biological and medicine fields. Herein, a water-soluble aminated β-1,3-D-glucan (AG) was synthesized and the anti-inflammatory effect, cytotoxicity and plasmid DNA (pDNA) binding capacity of AG, serum stability, the particle sizes and zeta potentials of AG/pDNA nanocomposites, and the transfection efficiency and mechanism of action were studied. AG shows no obvious cytotoxicity within the range of working concentration (1-64 μg/ml) and it exerts potent anti-inflammatory effect independent on Dectin-1 and TLR2. AG/pDNA nanocomposites prepared by electrostatic interaction possess an appropriate particle size ranged from 192.8 to 118.4 nm and zeta potentials ranged from 20.880 to 27.16 mV with the N/P ratios from 5 to 100. AG/pDNA nanocomposites at the N/P ratios of 10 and 20 were able to show superior transfection efficiencies in RAW 264.7 cells as a result of their suitable particle size, zeta potential, anti-inflammatory effect, and the specific interaction with pattern recognition receptors (Dectin-1 and TLR2). These results indicate that AG is a potential candidate for DNA delivery system due to its potent anti-inflammatory effect and high transfection efficiency.

Robust Immune Responses Elicited by a Hybrid Adjuvant Based on β-Glucan Particles from Yeast for the Hepatitis B Vaccine

The use of particulate adjuvants offers an interesting method for enhancing and modulating the immune responses elicited by vaccines. Aluminum salt (Alum) is one of the most important immune adjuvants approved by the Food and Drug Administration for use in humans because of its safety and efficacy, but it lacks the capacity to induce strong cellular and mucosal immune responses. In this study, we designed an antigen delivery system that combines aluminum salts with β-glucan particles. The β-glucan-aluminum particles (GP-Al) exhibited a highly uniform size of 2-4 μm and could highly specifically target antigen-presenting cells (APCs) and strongly induce dendritic cell (DC) maturation and cytokine secretion. In vivo studies showed that both WT mice and HBV-Tg mice immunized with hepatitis B surface antigen (HBsAg)-containing GP-Al displayed high anti-HBsAg IgG titers in the serum. Furthermore, in contrast to mice receiving the antigen alone, mice immunized with the particulate adjuvant exhibited IgG2a antibody titers and higher antigen-specific IFN-γ levels in splenocytes. In conclusion, we developed GP-Al microspheres to serve as a hepatitis B vaccine to enhance both humoral and cellular immune responses, representing a safe and promising system for antigen delivery.

Carboxymethyl-β-glucan/chitosan nanoparticles: new thermostable and efficient carriers for antigen delivery

In the last few decades, nanotechnology has emerged as an important tool aimed at enhancing the immune response against modern antigens. Nanocarriers designed specifically for this purpose have been shown to provide protection, stability, and controlled release properties to proteins, peptides, and polynucleotide-based antigens. Polysaccharides are particularly interesting biomaterials for the construction of these nanocarriers given their wide distribution among pathogens, which facilitates their recognition by antigen-presenting cells (APCs). In this work, we focused on an immunostimulant beta-glucan derivative, carboxymethyl-β-glucan, to prepare a novel nanocarrier in combination with chitosan. The resulting carboxymethyl-β-glucan/chitosan nanoparticles exhibited adequate physicochemical properties and an important protein association efficiency, with ovalbumin as a model compound. Moreover, thermostability was achieved through the optimization of a lyophilized form of the antigen-loaded nanoparticles, which remained stable for up to 1 month at 40 ºC. Biodistribution studies in mice showed an efficient drainage of the nanoparticles to the nearest lymph node following subcutaneous injection, and a significant co-localization with dendritic cells. Additionally, subcutaneous immunization of mice with a single dose of the ovalbumin-loaded nanoparticles led to induced T cell proliferation and antibody responses, comparable to those achieved with alum-adsorbed ovalbumin. These results illustrate the potential of these novel nanocarriers in vaccination.

Cell-derived vesicles for delivery of cancer immunotherapy

In recent years, cancer immunotherapy has received unprecedented attention due to the clinical achievements. The applications of biomedical engineering and materials science to cancer immunotherapy have solved the challenges caused by immunotherapy to a certain extent. Among them, cell-derived vesicles are natural biomaterials chosen as carriers or immune-engineering in view of their many unique advantages. This review will briefly introduce the recent applications of cell-derived vesicles for cancer immunotherapy.

Cell-derived vesicles for delivery of cancer immunotherapy

In recent years, cancer immunotherapy has received unprecedented attention due to the clinical achievements. The applications of biomedical engineering and materials science to cancer immunotherapy have solved the challenges caused by immunotherapy to a certain extent. Among them, cell-derived vesicles are natural biomaterials chosen as carriers or immune-engineering in view of their many unique advantages. This review will briefly introduce the recent applications of cell-derived vesicles for cancer immunotherapy.

Yeast microcapsule-mediated oral delivery of IL-1β shRNA for post-traumatic osteoarthritis therapy

Post-traumatic osteoarthritis is a prevalent debilitating joint disease. However, there is no FDA-approved disease-modifying osteoarthritis drug currently. Gene therapy can improve disease progression but lacks an effective delivery system. Here, we constructed an oral drug delivery system by non-virus-mediated interleukin-1β (IL-1β) short hairpin RNA (shRNA) and non-pathogenic yeast to evaluate its effect on osteoarthritis therapy. After recombinant IL-1β shRNA/yeast therapy, yeast microcapsule-mediated oral delivery of IL-1β shRNA greatly reduced the IL-1β expression in intestine macrophage, bone marrow macrophage, and articular cartilage, systematically regulate the inflammatory response. The degeneration of articular cartilage was significantly inhibited in the medial femoral condyle and medial tibial plateau of the knee joint. And the expression of osteoarthritis markers Col X and MMP13 was reduced in the knee joint. Thus, yeast microcapsule-mediated oral delivery of IL-1β shRNA may serve as a novel gene therapy strategy for treating joint degeneration through immunomodulation of the mononuclear phagocyte system from the intestine to subchondral bone marrow and ultimately preserving the articular cartilage joint.

A biomimetic yeast shell vaccine coated with layered double hydroxides induces a robust humoral and cellular immune response against tumors

Enhancing both the humoral and cellular immune response for tumor vaccination remains a challenge. Inspired by natural pathogen structures, we took β-glucan particles derived from a baker's yeast cell shell (YS) as a vaccine carrier and danger signal for dendritic cells (DCs), and coated the YS with catanionic layered double hydroxides (LDH) by electrostatic adsorption to form a biomimetic yeast cell particle (YSL). Our experimental results showed that the YSL vaccine efficiently targeted antigen-presenting cells (APCs) and remarkably enhanced antigen cross-presentation, and strongly improved the activation and maturation of DCs. Moreover, the YSL vaccine elicited an extremely high antibody titer and strong antigen-specific cytotoxic T lymphocyte together with mixed Th1/Th17 cellular immune responses and induced marked prophylactic and therapeutic effects against E.G7-OVA tumors in mouse models. These results suggest that YSL, integrating a yeast shell to mimic natural pathogens and LDH with high antigen-loading capacity and lysosome escape, is a promising tumor vaccine platform for rapid, effective and strong induction of both humoral and cellular immune responses.

Carbohydrate Conjugates in Vaccine Developments

Vaccines are powerful tools that can activate the immune system for protection against various diseases. As carbohydrates can play important roles in immune recognition, they have been widely applied in vaccine development. Carbohydrate antigens have been investigated in vaccines against various pathogenic microbes and cancer. Polysaccharides such as dextran and β-glucan can serve as smart vaccine carriers for efficient antigen delivery to immune cells. Some glycolipids, such as galactosylceramide and monophosphoryl lipid A, are strong immune stimulators, which have been studied as vaccine adjuvants. In this review, we focus on the current advances in applying carbohydrates as vaccine delivery carriers and adjuvants. We will discuss the examples that involve chemical modifications of the carbohydrates for effective antigen delivery, as well as covalent antigen-carbohydrate conjugates for enhanced immune responses.

β-glucan as a new tool in vaccine development

Vaccination constitutes one of the major breakthroughs in human medicine. At the same time, development of more immunogenic vaccine alternatives to using aluminium-based adjuvants is one of the most important phases of vaccination development. Among different sources of carbohydrate polymers, including plants, microbes and synthetic sources tested, glucans were found to be the most promising vaccine adjuvant, as they alone stimulate various immune reactions including antibody production without any negative side effects. The use of glucan particles as a delivery system is a viable option based on the documented efficient antigen loading and receptor-targeted uptake in antigen-presenting cells. In addition to particles, soluble glucans can be used as novel hydrogels or as direct immunocyte-targeting delivery systems employing novel complexes with oligodeoxynucleotides. This review focuses on recent advances in glucan-based vaccine development from glucan-based conjugates to a glucan-based delivery and adjuvant platform.

Biomimetic and bioinspired strategies for oral drug delivery

Oral drug delivery remains the most preferred approach due to its multiple advantages. Recently there has been increasing interest in the development of advanced vehicles for oral delivery of different therapeutics. Among them, biomimetic and bioinspired strategies are emerging as novel approaches that are promising for addressing biological barriers encountered by traditional drug delivery systems. Herein we provide a state-of-the-art review on the current progress of biomimetic particulate oral delivery systems. Different biomimetic nanoparticles used for oral drug delivery are first discussed, mainly including ligand/antibody-functionalized nanoparticles, transporter-mediated nanoplatforms, and nanoscale extracellular vesicles. Then we describe bacteria-derived biomimetic systems, with respect to oral delivery of therapeutic proteins or antigens. Subsequently, yeast-derived oral delivery systems, based on either chemical engineering or bioengineering approaches are discussed, with emphasis on the treatment of inflammatory diseases and cancer as well as oral vaccination. Finally, bioengineered plant cells are introduced for oral delivery of biological agents. A future perspective is also provided to highlight the existing challenges and possible resolution toward clinical translation of currently developed biomimetic oral therapies.

Glucan Particles Are a Powerful Adjuvant for the HBsAg, Favoring Antiviral Immunity

The lack of vaccine adjuvants that are able to induce robust T cell responses fosters the search for more powerful options. Pathogen-like particles are a promising approach. The adjuvant activity of pathogen-like particles is highly influenced by size and surface composition. This study aimed to evaluate the adjuvant potential of two different β-glucan-based particles, blend chitosan/β-glucan particles (ChiGluPs), which are positively charged and have mean size of 1276 nm, and neutral yeast-derived glucan particles (GPs), with a mean size of 3 μm. Additionally, chitosan particles (ChiPs) were used to understand the effect of β-glucan addition (ChiGluPs). Mouse spleen cells responded through the production of either TNF-α or RANTES, following in vitro stimulation with particles containing either β-glucan (ChiGluPs and GPs) or chitosan (ChiGluPs and ChiPs). Human monocytes responded to all particles through TNF-α secretion. Subcutaneous vaccination of mice with the hepatitis B surface antigen (HBsAg) showed increased serum IgG for all particles compared to HBsAg alone (435-, 4500-, or 2500-fold increase for either ChiPs, ChiGluPs, or GPs). Interestingly, only GPs elicited the secretion of HBsAg-specific Th1, Th2, Th9, Th17, Th22, and Treg-related cytokines. This study demonstrates, for the first time, that GPs can have a significant role against the hepatitis B virus by favoring antiviral immunity.

Supramolecular Nanofibers of Drug-Peptide Amphiphile and Affibody Suppress HER2+ Tumor Growth

Antibody-based medicines and nanomedicines are very promising for cancer therapy due to the high specificity and efficacy of antibodies. However, antibody-drug conjugates and antibody-modified nanomaterials frequently suffer from low drug loading and loss of functions due to the covalent modification of the antibody. A novel and versatile strategy to prepare supramolecular nanomaterials by the coassembly of an affibody (antiHER2) and drug-peptide amphiphiles is reported here. During the enzyme-instructed self-assembly process, the drug-peptide amphiphile can coassemble with the affibody, resulting in supramolecular nanofibers in hydrogels. The drug loading in the supramolecular nanofibers is high (>30 wt%), and the stability of antiHER2 is significantly improved in the nanofibers at 37 °C (>15 d in vitro). The supramolecular nanofibers exhibit high affinity for HER2+ cancer cells and can be efficiently taken up by these cells. In a mouse tumor model, the supramolecular nanofibers abolish HER2+ NCI-N87 tumor growth due to the good accumulation and retention of nanofibers in tumor. This study provides a novel strategy to prepare nanomedicines with high drug loading and high specificity.

A novel absorption spectrometric method, based on graphene nanomaterials, for detection of hepatocellular carcinoma-specific T lymphocyte cells

Introduction

Detection of antigen-specific cytotoxic T lymphocytes (CTLs) is the foundation for understanding hepatocellular carcinoma immune pathology and hepatocellular carcinoma immunotherapy. However, the classical method for labeling CTLs, major histocompatibility complex (MHC)–peptide tetramer, has drawbacks and needs further improvement.

Materials and methods

Here, as a new detection probe, a graphene-based MHC–peptide multimer was developed for sensitively and selectively identifying hepatocellular carcinoma-specific T-cells. To assess its detection efficiency, reduced graphene oxide (RGO) was functionalized with hemin and streptavidin to prepare a functionalized HRGO–streptavidin complex. Biotinylated MHC–peptide monomer was subsequently constructed onto HRGO to generate a detection probe for CTL labeling. The number of T-cells was detected through the reaction between HRGO and tetramethylbenzidine.

Results

Using HRGO/MHC–peptide multimers, the number of T-cells was efficiently detected in both the induction system in vitro and in peripheral blood of patients.

Conclusion

HRGO/MHC-peptide multimers methodology has application prospects in the detection of antigen peptide-specific T cells.

Discovery of a self-assembling and self-adjuvant lipopeptide as a saccharide-free peptide vaccine targeting EGFRvIII positive cutaneous melanoma

Recently, tumor immunotherapy has achieved great progress in the treatment of hematological and solid neoplasms. The DC vaccines, KLH-conjugated vaccines or glycosylated peptide vaccines can efficiently induce immune responses against tumors. In the current study, we have discovered cholesteryl PADRE-EGFRvIII epitope-conjugated lipopeptide self-assembled micelles as a potential self-adjuvant vaccine against cutaneous melanoma. The lipopeptide vaccines were synthesized using a standard solid phase peptide synthesis method, and these vaccines could elicit both a humoral and a cellular immune response to EGFRvIII positive melanoma cells. Their high humoral immunoreaction stimulation properties in combination with their cytotoxic T-cell eliciting properties provide them with potent tumor inhibitory capacity. In therapeutic and preventive xenograft models of B16-EGFRvIII melanoma cells, the self-adjuvant lipopeptide vaccine micelles efficiently prevented tumor growth as well as tumorigenesis. Our results provide a novel platform for eliciting immune responses to non-antigenic cancer-related epitopes in peptide cancer vaccine discovery and development.

Synergistic effect of dual targeting vaccine adjuvant with aminated β-glucan and CpG-oligodeoxynucleotides for both humoral and cellular immune responses

Presently, clinically approved adjuvants (such as aluminum salts) fail to induce cellular immune responses, which is crucial to defend against intracellular pathogens (including HIV, malaria, tuberculosis and Ebola) and cancer. However, Freund's complete adjuvant potently stimulates both humoral and cellular immune responses, accompanying by high toxicity and severe side reactions. Here in this work, a CpG-oligodeoxynucleotides (CpG-OND) crosslinked aminated β-glucan-Ovalbumin dual targeting nanoparticle (CpG-OND-AG-OVA) is prepared through a simple and mild ionic complexation method. The aminated β-glucan plays dual roles as antigen presenting cells (APCs) targeted carrier and immunopotentiator (targeting and activating dectin-1 on APCs). Meanwhile, CpG-OND also plays dual roles as ionic crosslinker and immunopotentiator (targeting and activating Toll-like receptor 9 in APCs). The adjuvant activity of the particles is evaluated through in vitro and in vivo experiments. The particles significantly enhance uptake and sustained proteolytic processing of antigens, and result in APCs maturation, inducing robust Th1 and Th2-type immune responses comparable to Freund's adjuvant without obvious toxicity. The potent adjuvant activity of the nanoparticles may originate from dual targeting synergistic effects between aminated β-glucan and CpG-OND. Accordingly, the dual targeting nanoparticles may be a promising vaccine adjuvant for inducing robust humoral and cellular immune responses against infectious diseases and cancers.

STATEMENT OF SIGNIFICANCE

An ideal adjuvant for subunit vaccine should act as both a carrier to enhance the uptake, sustained processing and cytosolic delivery of antigens, and an immunopotentiator to stimulate antigen presenting cells (APCs) for activation of naive T cells. Additionally, it should be easy to obtain and safe with negligible toxicity. Unfortunately, both synthetic and natural polymers that have been developed into antigen delivery system cannot completely fulfill the requirements. In the present study, the authors design nanoparticles with aminated β-glucan and CpG-oligodeoxynucleotides (CpG-OND) through a simple and mild method. β-Glucan (a dectin-1 and TLR2 targeted PAMP) and CpG-OND (a TLR9 targeted PAMP) are readily accessible. Aminated β-glucan plays dual roles in the nanoparticle as APCs targeted carrier and immunopotentiator. Meanwhile, CpG-OND also plays dual roles as crosslinker and APCs targeted immunopotentiator. By making use of synergistic effect of the dual targeting vaccine adjuvant with aminated β-glucan and CpG-OND, the nanoparticles induce robust antigen specific immune responses comparable to Freund's adjuvant without obvious toxicity.

Dendritic Cells in the Cross Hair for the Generation of Tailored Vaccines

Vaccines represent the discovery of utmost importance for global health, due to both prophylactic action to prevent infections and therapeutic intervention in neoplastic diseases. Despite this, current vaccination strategies need to be refined to successfully generate robust protective antigen-specific memory immune responses. To address this issue, one possibility is to exploit the high efficiency of dendritic cells (DCs) as antigen-presenting cells for T cell priming. DCs functional plasticity allows shaping the outcome of immune responses to achieve the required type of immunity. Therefore, the choice of adjuvants to guide and sustain DCs maturation, the design of multifaceted vehicles, and the choice of surface molecules to specifically target DCs represent the key issues currently explored in both preclinical and clinical settings. Here, we review advances in DCs-based vaccination approaches, which exploit direct in vivo DCs targeting and activation options. We also discuss the recent findings for efficient antitumor DCs-based vaccinations and combination strategies to reduce the immune tolerance promoted by the tumor microenvironment.

Aluminum hydroxide colloid vaccine encapsulated in yeast shells with enhanced humoral and cellular immune responses

Aluminum salt (Alum) is one of the most important immune adjuvants approved for use in humans, however it is not suitable for vaccination against various chronic infectious diseases and cancers for not being able to induce cell-mediated (Th1) immunity. Here, we encapsulated an Alum colloid inside β-glucan particles (GPs), which are a type of natural particles derived from the yeast glucan shells, to prepare hybrid GP-Alum (GP-Al) adjuvant particles with a very uniform size of 2-4 μm. These hybrid particles can be used to load antigen proteins through a simple mixing procedure, and can be highly specifically targeted to antigen-presenting cells (APCs) and strongly activate dendritic cells (DCs) maturation and cytokine secretion. In an animal model, they elicit a strong Th1-biased immune response and extremely high antibody titer, and cause marked prophylactic and therapeutic effects against tumors. As Alum has been proven to be a safe adjuvant to induce strong humoral responses and β-glucans are safe for human use, this very uniform hybrid Alum particulate system could have important application as a vaccine carrier to stimulate humoral and cellular immune responses at the same time.

Synthetic Polymeric Mixed Micelles Targeting Lymph Nodes Trigger Enhanced Cellular and Humoral Immune Responses

It has been widely accepted that lymph nodes (LNs) are critical targets of cancer vaccines because antigen presentation and initiation of T-cell-mediated immune responses occur primarily at these locations. In this study, amphiphilic diblock copolymer poly(2-ethyl-2-oxazoline)-poly(d,l-lactide) (PEOz-PLA) combined with carboxylterminated-Pluronic F127 was used to construct mixed micelles [carboxylated-nanoparticles (NPs)] for codelivery of antigen ovalbumin (OVA) and Toll-like receptor-7 agonist CL264 (carboxylated-NPs/OVA/CL264) to the LN-resident dendritic cells (DCs). The results showed that the small, sub-60 nm size of the self-assembled mixed micelles enables them to rapidly penetrate into lymphatic vessels and reach draining lymph nodes after subcutaneous injection. Furthermore, the surface modification with carboxylic groups imparted the carboxylated-NPs with endocytic receptor-targeting ability, allowing for DC internalization of carboxylated-NPs/OVA/CL264 via the scavenger receptor-mediated pathway. Because stimulation of CL264 in early endosomes will lead to a more effective immune response than that in late endo/lysosomes, the mass ratio of PEOz-PLA to carboxylated-Pluronic F127 in the mixed micelles was adjusted to release the encapsulated CL264 to the early endosome, resulting in increased expression of costimulatory molecules and secretion of stimulated cytokines by DCs. Moreover, the incorporation of PEOz outside the micellar shell effectively augmented MHC I antigen presentation through facilitating endosome escape and cytosolic release of antigens. This in turn evoked potent immune responses in vivo, including activation of antigen-specific T-cell responses, production of antigen-specific IgG antibodies, and generation of cytotoxic T-lymphocyte responses. Finally, immunization with the codelivery system in E.G7-OVA tumor-bearing mice could not only significantly inhibit tumor growth but also markedly prolong the survival of tumor-bearing mice. Taken together, carboxylated-NPs/OVA/CL264 have demonstrated great potential for clinical applications as an effective antitumor vaccine for further immunotherapy.