Reduction Sensitive PEG Hydrogels for Codelivery of Antigen and Adjuvant To Induce Potent CTLs

Boosting antigen-specific T cell activation with lipid-stabilized protein nanoaggregates

Vaccines based on protein antigens have numerous advantages over inactivated pathogens, including easier manufacturing and improved safety. However, purified antigens are weakly immunogenic, as they lack the spatial organization and the associated 'danger signals' of the pathogen. Formulating vaccines as nanoparticles enhances the recognition by antigen presenting cells, boosting the cell-mediated immune response. This study describes a nano-precipitation method to obtain stable protein nanoaggregates with uniform size distribution without using covalent cross-linkers. Nanoaggregates were formed via microfluidic mixing of ovalbumin (OVA) and lipids in the presence of high methanol concentrations. A purification protocol was set up to separate the nanoaggregates from OVA and liposomes, obtained as byproducts of the mixing. The nanoaggregates were characterized in terms of morphology, ζ-potential and protein content, and their interaction with immune cells was assessed in vitro. Antigen-specific T cell activation was over 6-fold higher for nanoaggregates compared to OVA, due in part to the enhanced uptake by immune cells. Lastly, a two-dose immunization with nanoaggregates in mice induced a significant increase in OVA-specific CD8+ T splenocytes compared to soluble OVA. Overall, this work presents for the first time the microfluidic production of lipid-stabilized protein nanoaggregates and provides a proof-of-concept of their potential for vaccination.

Humoral Response to the Acetalated Dextran M2e Vaccine is Enhanced by Antigen Surface Conjugation

The influenza A virus causes substantial morbidity and mortality worldwide every year and poses a constant threat of an emergent pandemic. Seasonal influenza vaccination strategies fail to provide complete protection against infection due to antigenic drift and shift. A universal vaccine targeting a conserved influenza epitope could substantially improve current vaccination strategies. The ectodomain of the matrix 2 protein (M2e) of influenza is a highly conserved epitope between virus strains but is also poorly immunogenic. Administration of M2e and the immunostimulatory stimulator of interferon genes (STING) agonist 3'3'-cyclic guanosine-adenosine monophosphate (cGAMP) encapsulated in microparticles made of acetalated dextran (Ace-DEX) has previously been shown to be effective for increasing the immunogenicity of M2e, primarily through T-cell-mediated responses. Here, the immunogenicity of Ace-DEX MPs delivering M2e was further improved by conjugating the M2e peptide to the particle surface in an effort to affect B-cell responses more directly. Conjugated or encapsulated M2e co-administered with Ace-DEX MPs containing cGAMP were used to vaccinate mice, and it was shown that two or three vaccinations could fully protect against a lethal influenza challenge, while only the surface-conjugated antigen constructs could provide some protection against lethal challenge with only one vaccination. Additionally, the use of a reducible linker augmented the T-cell response to the antigen. These results show the utility of conjugating M2e to the surface of a particle carrier to increase its immunogenicity for use as the antigen in a universal influenza vaccine.

Poly Ethylene Glycol (PEG)-Based Hydrogels for Drug Delivery in Cancer Therapy: A Comprehensive Review

Hydrogel-based drug delivery systems (DDSs) can leverage therapeutically beneficial outcomes in cancer therapy. In this domain, polyethylene glycol (PEG) has become increasingly popular as a biomedical polymer and has found clinical use. Owing to their excellent biocompatibility, facile modifiability, and high drug encapsulation rate, PEG hydrogels have shown great promise as drug delivery platforms. Here, the progress in emerging novel designs of PEG-hydrogels as DDSs for anti-cancer therapy is reviewed and discussed, focusing on underpinning multiscale release mechanisms categorized under stimuli-responsive and non-responsive drug release. The responsive drug delivery approaches are discussed, and the underpinning release mechanisms are elucidated, covering the systems functioning based on either exogenous stimuli-response, such as photo- and magnetic-sensitive PEG hydrogels, or endogenous stimuli-response, such as enzyme-, pH-, reduction-, and temperature-sensitive PEG hydrogels. Special attention is paid to the commercial potential of PEG-based hydrogels in cancer therapy, highlighting the limitations that need to be addressed in future research for their clinical translation.

Phenylboronic ester-modified polymeric nanoparticles for promoting TRP2 peptide antigen delivery in cancer immunotherapy

The tremendous development of peptide-based cancer vaccine has attracted incremental interest as a powerful approach in cancer management, prevention and treatment. As successful as tumor vaccine has been, major challenges associated with achieving efficient immune response against cancer are (1) drainage to and retention in lymph nodes; (2) uptake by dendritic cells (DCs); (3) activation of DCs. In order to overcome these barriers, here we construct PBE-modified TRP2 nanovaccine, which comprises TRP2 peptide tumor antigen and diblock copolymer PEG-b-PAsp grafted with phenylboronic ester (PBE). We confirmed that this TRP2 nanovaccine can be effectively trapped into lymph node, uptake by dendritic cells and induce DC maturation, relying on increased negative charge, ROS response and pH response. Consistently, this vehicle loaded with TRP2 peptide could boost the strongest T cell immune response against melanoma in vivo and potentiate antitumor efficacy both in tumor prevention and tumor treatment without any exogenous adjuvant. Furthermore, the TRP2 nanovaccine can suppress the tumor growth and prolong animal survival time, which may result from its synergistic effect of inhibiting tumor immunosuppression and increasing cytotoxic lymphocyte (CTL) response. Hence this type of PBE-modified nanovaccine would be widely used as a simple, safe and robust platform to deliver other antigen in cancer immunotherapy.

Hydrogel-guided strategies to stimulate an effective immune response for vaccine-based cancer immunotherapy

Cancer vaccines have attracted widespread interest in tumor therapy because of the potential to induce an effective antitumor immune response. However, many challenges including weak immunogenicity, off-target effects, and immunosuppressive microenvironments have prevented their broad clinical translation. To overcome these difficulties, effective delivery systems have been designed for cancer vaccines. As carriers in cancer vaccine delivery systems, hydrogels have gained substantial attention because they can encapsulate a variety of antigens/immunomodulators and protect them from degradation. This enables hydrogels to simultaneously reverse immunosuppression and stimulate the immune response. Meanwhile, the controlled release properties of hydrogels allow for precise temporal and spatial release of loads in situ to further enhance the immune response of cancer vaccines. Therefore, this review summarizes the classification of cancer vaccines, highlights the strategies of hydrogel-based cancer vaccines, and provides some insights into the future development of hydrogel-based cancer vaccines.

Lymph node-targeting nanovaccines for cancer immunotherapy

Cancer immunotherapies such as tumor vaccines, chimeric antigen receptor T cells and immune checkpoint blockades, have attracted tremendous attention. Among them, tumor vaccines prime immune response by delivering antigens and adjuvants to the antigen presenting cells (APCs), thus enhancing antitumor immunotherapy. Despite tumor vaccines have made considerable achievements in tumor immunotherapy, it remains challenging to efficiently deliver tumor vaccines to activate the dendritic cells (DCs) in lymph nodes (LNs). Rational design of nanovaccines on the basis of biomedical nanotechnology has emerged as one of the most promising strategies for boosting the outcomes of cancer immunotherapy. In recent years, great efforts have been made in exploiting various nanocarrier-based LNs-targeting tumor nanovaccines. In view of the rapid advances in this field, we here aim to summarize the latest progression in LNs-targeting nanovaccines for cancer immunotherapy, with special attention to various nano-vehicles developed for LNs-targeting delivery of tumor vaccines, including lipid-based nanoparticles, polymeric nanocarriers, inorganic nanocarriers and biomimetic nanosystems. Moreover, the recent trends in nanovaccines-based combination cancer immunotherapy are provided. Finally, the rationality, advantages and challenges of LNs-targeting nanovaccines for clinical translation and application are spotlighted.

A nanovaccine for enhancing cellular immunity via cytosolic co-delivery of antigen and polyIC RNA

Traditional approaches to cancer vaccines elicit weak CD8+ T cell responses and have largely failed to meet clinical expectations. This is in part due to inefficient antigen cross-presentation, inappropriate selection of adjuvant and its formulation, poor vaccine pharmacokinetics, and/or suboptimal coordination of antigen and adjuvant delivery. Here, we describe a nanoparticle vaccine platform for facile co-loading and dual-delivery of antigens and nucleic acid adjuvants that elicits robust antigen-specific cellular immune responses. The nanovaccine design is based on diblock copolymers comprising a poly(ethylene glycol)-rich first block that is functionalized with reactive moieties for covalent conjugation of antigen via disulfide linkages, and a pH-responsive second block for electrostatic packaging of nucleic acids that also facilitates endosomal escape of associated vaccine cargo to the cytosol. Using polyIC, a clinically-advanced nucleic acid adjuvant, we demonstrated that endosomolytic nanoparticles promoted the cytosolic co-delivery of polyIC and protein antigen, which acted synergistically to enhance antigen cross-presentation, co-stimulatory molecule expression, and cytokine production by dendritic cells. We also found that the vaccine platform increased the accumulation of antigen and polyIC in the local draining lymph nodes. Consequently, dual-delivery of antigen and polyIC with endsomolytic nanoparticles significantly enhanced the magnitude and functionality of CD8+ T cell responses relative to a mixture of antigen and polyIC, resulting in inhibition of tumor growth in a mouse tumor model. Collectively, this work provides a proof-of-principle for a new cancer vaccine platform that strongly augments anti-tumor cellular immunity via cytosolic co-delivery of antigen and nucleic acid adjuvant.

A novel self-assembled epitope peptide nanoemulsion vaccine targeting nasal mucosal epithelial cell for reinvigorating CD8+ T cell immune activity and inhibiting tumor progression

Epitope peptides are not suitable for nasal administration immunity due to their poor immunogenicity and low delivery efficiency. Here, we reported an intranasal self-assembled nanovaccine (I-OVA NE), which was loaded with the peptides IKVAV-OVA_257-264 (I-OVA), a laminin peptide (Ile-Lys-Val-ala-Val, IKVAV) and OVA_257-264 epitope conjugated peptide. This nanovaccine with I-OVA at a concentration of 4 mg/mL showed the average particle size of 30.37 ± 2.49 nm, zeta potential of -16.67 ± 1.76 mV, and encapsulation rate of 84.07 ± 7.59%. Moreover, the mucin did not alter its stability (size, PdI and zeta potential). And it also had no obvious acute pathological changes neither in the nasal mucosa nor lung tissues after nasal administration. Meanwhile, the antigen uptake of I-OVA NE was promoted, and the nasal residence time was also prolonged in vivo. Besides, the uptake rate of this nanovaccine was obviously higher than that of free I-OVA (P < 0.001) after blocking by the integrin antibody, suggesting that the binding of IKVAV to integrin is involved in the epitope peptide uptake. Importantly, this nanovaccine enhanced peptide-specific CD8⁺T cells exhibiting OVA_257-264-specific CTL activity and Th1 immune response, leading to the induction of the protective immunity in E.G7-OVA tumor-bearing mice. Overall, these data indicate that I-OVA NE can be an applicable strategy of tumor vaccine development.

An in-depth analysis of novel combinatorial drug therapy via nanocarriers against HIV/AIDS infection and their clinical perspectives: a systematic review

Introduction: Conventional antiretroviral therapy against HIV infections is threatening to become outdated due to the low chemical, physical, biological, and pharmacokinetic characteristics of therapeutic molecules, followed by the high chance of emergence of drug resistance. Considering the co-encapsulation of multi-infection agents in a single nanocarrier is emerging to offer various benefits such as synergistic action, improved therapeutic efficacy, reduced drug resistance development, patient compliance, and economical therapy.Areas covered: A systematic review of nano-based combinatorial drug therapy was performed using various databases including Scopus, PubMed, Google Scholar, and Science Direct between 2000 and 2020. The search set was screened as per the inclusion and exclusion criteria, followed by 46 scientific articles and seven clinical studies selected for in-depth analysis.Expert opinion: There has been an immense effort to analyze the mechanism of HIV infection to develop a promising therapeutic approach, although the aim of complete prevention has not been succeeded yet. The key finding is to overcome the challenges associated with conventional therapy by the combinatorial drug in a single nanoformulation, which holds great potential for impact in the management of HIV infection.

Sequential and Timely Combination of a Cancer Nanovaccine with Immune Checkpoint Blockade Effectively Inhibits Tumor Growth and Relapse

We describe a small lipid nanoparticle (SLNP)-based nanovaccine platform and a new combination treatment regimen. Tumor antigen-displaying, CpG adjuvant-embedded SLNPs (OVA_PEP -SLNP@CpG) were prepared from biocompatible phospholipids and a cationic cholesterol derivative. The resulting nanovaccine showed highly potent antitumor efficacy in both prophylactic and therapeutic E.G7 tumor models. However, this vaccine induced T cell exhaustion by elevating PD-L1 expression, leading to tumor recurrence. Thus, the nanovaccine was combined with simultaneous anti-PD-1 antibody treatment, but the therapeutic efficacy of this regimen was comparable to that of the nanovaccine alone. Finally, mice that showed a good therapeutic response after the first cycle of immunization with the nanovaccine underwent a second cycle together with anti-PD-1 therapy, resulting in suppression of tumor relapse. This suggests that the antitumor efficacy of combinations of nanovaccines with immune checkpoint blockade therapy is dependent on treatment sequence and the timing of each modality.

Pulmonary Delivery of Nanoparticle-Bound Toll-like Receptor 9 Agonist for the Treatment of Metastatic Lung Cancer

CpG oligodeoxynucleotides are potent toll-like receptor (TLR) 9 agonists and have shown promise as anticancer agents in preclinical studies and clinical trials. Binding of CpG to TLR9 initiates a cascade of innate and adaptive immune responses, beginning with activation of dendritic cells and resulting in a range of secondary effects that include the secretion of pro-inflammatory cytokines, activation of natural killer cells, and expansion of T cell populations. Recent literature suggests that local delivery of CpG in tumors results in superior antitumor effects as compared to systemic delivery. In this study, we utilized PRINT (particle replication in nonwetting templates) nanoparticles as a vehicle to deliver CpG into murine lungs through orotracheal instillations. In two murine orthotopic metastasis models of non-small-cell lung cancer-344SQ (lung adenocarcinoma) and KAL-LN2E1 (lung squamous carcinoma), local delivery of PRINT-CpG into the lungs effectively promoted substantial tumor regression and also limited systemic toxicities associated with soluble CpG. Furthermore, cured mice were completely resistant to tumor rechallenge. Additionally, nanodelivery showed extended retention of CpG within the lungs as well as prolonged elevation of antitumor cytokines in the lungs, but no elevated levels of proinflammatory cytokines in the serum. These results demonstrate that PRINT-CpG is a potent nanoplatform for local treatment of lung cancer that has collateral therapeutic effects on systemic disease and an encouraging toxicity profile and may have the potential to treat lung metastasis of other cancer types.

Nonspherical Nanoparticle Shape Stability Is Affected by Complex Manufacturing Aspects: Its Implications for Drug Delivery and Targeting

The shape of nanoparticles is known recently as an important design parameter influencing considerably the fate of nanoparticles with and in biological systems. Several manufacturing techniques to generate nonspherical nanoparticles as well as studies on in vitro and in vivo effects thereof have been described. However, nonspherical nanoparticle shape stability in physiological-related conditions and the impact of formulation parameters on nonspherical nanoparticle resistance still need to be investigated. To address these issues, different nanoparticle fabrication methods using biodegradable polymers are explored to produce nonspherical nanoparticles via the prevailing film-stretching method. In addition, systematic comparisons to other nanoparticle systems prepared by different manufacturing techniques and less biodegradable materials (but still commonly utilized for drug delivery and targeting) are conducted. The study evinces that the strong interplay from multiple nanoparticle properties (i.e., internal structure, Young's modulus, surface roughness, liquefaction temperature [glass transition (T_g ) or melting (T_m )], porosity, and surface hydrophobicity) is present. It is not possible to predict the nonsphericity longevity by merely one or two factor(s). The most influential features in preserving the nonsphericity of nanoparticles are existence of internal structure and low surface hydrophobicity (i.e., surface-free energy (SFE) > ≈55 mN m^-1 , material-water interfacial tension <6 mN m^-1 ), especially if the nanoparticles are soft (<1 GPa), rough (R_rms > 10 nm), porous (>1 m² g^-1 ), and in possession of low bulk liquefaction temperature (<100 °C). Interestingly, low surface hydrophobicity of nanoparticles can be obtained indirectly by the significant presence of residual stabilizers. Therefore, it is strongly suggested that nonsphericity of particle systems is highly dependent on surface chemistry but cannot be appraised separately from other factors. These results and reviews allot valuable guidelines for the design and manufacturing of nonspherical nanoparticles having adequate shape stability, thereby appropriate with their usage purposes. Furthermore, they can assist in understanding and explaining the possible mechanisms of nonspherical nanoparticles effectivity loss and distinctive material behavior at the nanoscale.

Nanoparticle-Based Nanomedicines to Promote Cancer Immunotherapy: Recent Advances and Future Directions

Cancer immunotherapy is a promising cancer terminator by directing the patient's own immune system in the fight against this challenging disorder. Despite the monumental therapeutic potential of several immunotherapy strategies in clinical applications, the efficacious responses of a wide range of immunotherapeutic agents are limited in virtue of their inadequate accumulation in the tumor tissue and fatal side effects. In the last decades, increasing evidences disclose that nanotechnology acts as an appealing solution to address these technical barriers via conferring rational physicochemical properties to nanomaterials. In this Review, an imperative emphasis will be drawn from the current understanding of the effect of a nanosystem's structure characteristics (e.g., size, shape, surface charge, elasticity) and its chemical modification on its transport and biodistribution behavior. Subsequently, rapid-moving advances of nanoparticle-based cancer immunotherapies are summarized from traditional vaccine strategies to recent novel approaches, including delivery of immunotherapeutics (such as whole cancer cell vaccines, immune checkpoint blockade, and immunogenic cell death) and engineered immune cells, to regulate tumor microenvironment and activate cellular immunity. The future prospects may involve in the rational combination of a few immunotherapies for more efficient cancer inhibition and elimination.

Protein Transduction Domain Mimics Facilitate Rapid Antigen Delivery into Monocytes

Delivering peptides and proteins with intracellular function represents a promising avenue for therapeutics, but remains a challenge due to the selective permeability of the plasma membrane. The successful delivery of cytosolically active proteins would enable many opportunities, including improved vaccine development through major histocompatibility complex (MHC) class I antigen display. Extended research using cell-penetrating peptides (CPPs) has aimed to facilitate intracellular delivery of exogenous proteins with some success. A new class of polymer-based mimics termed protein transduction domain mimics (PTDMs), which maintain the positive charge and amphiphilic nature displayed by many CPPs, was developed using a poly-norbornene-based backbone. Herein, we use a previously characterized PTDM to investigate delivery of the model antigen SIINFEKL into leukocytes. Peptide delivery into over 90% of CD14+ monocytes was detected in less than 15 min with nominal inflammatory cytokine response and high cell viability. The co-delivery of a TLR9 agonist and antigen using the PTDM into antigen-presenting cells in vitro showed presentation of SIINFEKL in association with MHC class I molecules, in addition to upregulation of classical differentiation markers revealing the ability of the PTDM to successfully deliver cargo intracellularly and show application in the field of immunotherapy.

Role of Linker Length and Antigen Density in Nanoparticle Peptide Vaccine

Multiple studies have been published emphasizing the significant role of nanoparticle (NP) carriers in antigenic peptide-based subunit vaccines for the induction of potent humoral and cellular responses. Various design parameters of nanoparticle subunit vaccines such as linker chemistry, the proximity of antigenic peptide to NPs, and the density of antigenic peptides on the surface of NPs play an important role in antigen presentation to dendritic cells (DCs) and in subsequent induction of CD8+ T cell response. In this current study, we evaluated the role of peptide antigen proximity and density on DC uptake, antigen cross-presentation, in vitro T cell proliferation, and in vivo induction of CD8+ T cells. To evaluate the role of antigen proximity, CSIINFEKL peptides were systematically conjugated to poly(ethylene glycol) (PEG) hydrogels through N-hydroxysuccinimide-PEG-maleimide linkers of varying molecular weights: 2k, 5k, and 10k. We observed that the peptides conjugated to NPs via the 2k and 5k PEG linkers resulted in higher uptake in bone marrow-derived DCs (BMDCs) and increased p-MHC-I formation on the surface of bone marrow-derived DCs (BMDCs) as compared to the 10k PEG linker formulation. However, no significant differences in vitro T cell proliferation and induction of in vivo CD8+ T cells were found among linker lengths. To study the effect of antigen density, CSIINFEKL peptides were conjugated to PEG hydrogels via 5k PEG linkers at various densities. We found that high antigen density NPs presented the highest p-MHC-I on the surface of BMDCs and induced higher proliferation of T cells, whereas NPs with low peptide density resulted in higher DC cell uptake and elevated frequency of IFN-γ producing CD8+ T cells in mice as compared to the medium- and high-density formulations. Altogether, findings for these experiments highlighted the importance of linker length and peptide antigen density on DC cell uptake, antigen presentation, and induction of in vivo CD8+ T cell response.

Nanoparticle-Mediated Remodeling of the Tumor Microenvironment to Enhance Immunotherapy

Nanoscience has long been lauded as a method through which tumor-associated barriers could be overcome. As successful as cancer immunotherapy has been, limitations associated with the tumor microenvironment or side effects of systemic treatment have become more apparent. In this Review, we seek to lay out the therapeutic challenges associated with the tumor microenvironment and the ways in which nanoscience is being applied to remodel the tumor microenvironment and increase the susceptibility of many cancer types to immunotherapy. We detail the nanomedicines on the cutting edge of cancer immunotherapy and how their interactions with the tumor microenvironment make them more effective than systemically administered immunotherapies.

The choice of linker for conjugating R848 to inactivated influenza virus determines the stimulatory capacity for innate immune cells

Inactivated influenza vaccines are not approved for use in infants less than 6 months of age due to poor immunogenicity in that population. While the live attenuated influenza vaccine has the potential to be more immunogenic, it is not an option for infants and other vulnerable populations, including the elderly and immunocompromised individuals due to safety concerns. In an effort to improve the immunogenicity of the inactivated vaccine for use in vulnerable populations, we have used an approach of chemically crosslinking the Toll-like receptor (TLR) 7/8 agonist R848 directly to virus particles. We have reported previously that an R848-conjugated, inactivated vaccine is more effective at inducing adaptive immune responses and protecting against lung pathology in influenza challenged neonatal African green monkeys than is the unmodified counterpart. In the current study, we describe a second generation vaccine that utilizes an amide-sulfhydryl crosslinker with different spacer chemistry and length to couple R848 to virions. The new vaccine has significantly enhanced immunostimulatory activity for murine macrophages and importantly for monocyte derived human dendritic cells. Demonstration of the significant differences in stimulatory activity afforded by modest changes in linker impacts our fundamental view of the design of TLR agonist-antigen vaccines.

Reduction-Responsive Codelivery System Based on a Metal-Organic Framework for Eliciting Potent Cellular Immune Response

Utilizing nanoparticles to deliver subunit vaccines can be viewed as a promising strategy for enhancing the immune response, especially with regard to cellular immunity to fight against infectious viruses and malignant cancer. Nevertheless, its applications are still far from practicality because of some limitations such as high cost, non-biocompatibility, non-biodegradability, and the inefficient stimulation of cytotoxic T lymphocyte (CTL) response. In this study, we use metal-organic framework (MOF) MIL-101-Fe-NH₂ nanoparticles as carriers to fabricate an innovative reduction-responsive antigen delivery system for cotransporting the antigen model ovalbumin (OVA) and an immune adjuvant, unmethylated cytosine-phosphate-guanine (CpG) oligonucleotide. In vitro cellular tests show that the MOF nanoparticles can not only greatly improve the uptake of OVA by the antigen-presenting cells but also smartly deliver both OVA and CpG into the same cell. By feat of the reductively controllable release of OVA and the promoting function of CpG, the delivery system can elicit strong cellular immunity and CTL response in mice. Moreover, the increased frequencies of effector memory T cells inspired by the delivery system indicate that it can induce a potent immune memory response. These results demonstrate that MOF nanoparticles are excellent vehicles for codelivering antigen and immune adjuvant and may find wider applications in biomedical fields.

Perspectives in allergen immunotherapy: 2017 and beyond

The Future of the Allergists and Specific Immunotherapy (FASIT) workshop provides a regular platform for global experts from academia, allergy clinics, regulatory authorities and industry to review developments in the field of allergen immunotherapy (AIT). The most recent meeting, held in February 2017, had two main themes: advances in AIT and hot topics in AIT from the regulatory point of view. The first theme covered opportunities for personalized AIT, advances in adjuvants and delivery systems, and the development of new molecules and future vaccines for AIT. Key topics in the second part of the meeting were the effects of the enactment of European Directive 2001/83 on the availability of allergens for therapy and diagnosis across the EU, the challenges of conducting Phase 3 studies in the field, the future role of allergen exposure chambers in AIT studies and specific considerations in performing AIT studies in the paediatric population. Finally, the group highlighted the forthcoming EAACI guidelines and their particular importance for the standardization of practice in the treatment of allergies. This review presents a comprehensive insight into those panel discussions and highlights unmet needs and also possible solutions to them for the future.

Extending antigen release from particulate vaccines results in enhanced antitumor immune response

Tumor-specific CD8⁺ cytotoxic T lymphocytes (CTLs) play a critical role in an anti-tumor immune response. However, vaccination intended to elicit a potent CD8⁺ T cell responses employing tumor-associated peptide antigens, are typically ineffective due to poor immunogenicity. Previously, we engineered a polyethylene glycol (PEG) hydrogel-based subunit vaccine for the delivery of an antigenic peptide and CpG (adjuvant) to elicit potent CTLs. In this study, we further examined the effect of antigen release kinetics on their induced immune responses. A CD8⁺ T cell epitope peptide from OVA (CSIINFEKL) and CpG were co-conjugated to nanoparticles utilizing either a disulfide or a thioether linkage. Subsequent studies comparing peptide release rates as a function of linker, determined that the thioether linkage provided sustained release of peptide over 72h. Ability to control the release of peptide resulted in both higher and prolonged antigen presentation when compared to disulfide-linked peptide. Both NP vaccine formulations resulted in activation and maturation of bone marrow derived dendritic cells (BMDCs) and induced potent CD8⁺ T cell responses when compared to soluble antigen and soluble CpG. Immunization with either disulfide or thioether linked vaccine constructs effectively inhibited EG7-OVA tumor growth in mice, however only treatment with the thioether linked vaccine construct resulted in enhanced survival.

Self-Assembling Peptide Epitopes as Novel Platform for Anticancer Vaccination

The aim of the present study was to improve the immunogenicity of peptide epitope vaccines using novel nanocarriers based on self-assembling materials. Several studies demonstrated that peptide antigens in nanoparticulate form induce stronger immune responses than their soluble forms. However, several issues such as poor loading and risk of inducing T cell anergy due to premature release of antigenic epitopes have challenged the clinical success of such systems. In the present study, we developed two vaccine delivery systems by appending a self-assembling peptide (Ac-AAVVLLLW-COOH) or a thermosensitive polymer poly(N-isopropylacrylamide (pNIPAm) to the N-terminus of different peptide antigens (OVA250-264, HPV-E743-57) to generate self-assembling peptide epitopes (SAPEs). The obtained results showed that the SAPEs were able to form nanostructures with a diameter from 20 to 200 nm. The SAPEs adjuvanted with CpG induced and expanded antigen-specific CD8+ T cells in mice. Furthermore, tumor-bearing mice vaccinated with SAPEs harboring the HPV E743-57 peptide showed a delayed tumor growth and an increased survival compared to sham-treated mice. In conclusion, self-assembling peptide based systems increase the immunogenicity of peptide epitope vaccines and therefore warrants further development toward clinical use.

pH Sensitive phosphorylated chitosan hydrogel as vaccine delivery system for intramuscular immunization

In the field of immunotherapy, immune vaccinations have received more and more attention for disease prevention and treatment. In immune vaccination, efficient vaccine adjuvants are necessary due to the weak immunogenicity of vaccines. Some traditional vaccine adjuvants have been widely used but have shown obvious limitations such as poor biosafety. Therefore, researchers make a great effort to develop more functional novel immune adjuvants such as chitosan-based immune adjuvants. However, chitosan is poorly water soluble, which greatly limits its application as immune adjuvants, regardless of its good biocompatibility, biodegradability, and other biological activities. In this work, we prepared a water-soluble chitosan derivative phosphorylated chitosan (PCS) and evaluated its potential as a novel immune adjuvant. PCS was found to be pH sensitive: specifically, it was water soluble at pH < 7.0 but began to gel at pH >7.0. By virtue of this, neutral PCS aqueous solutions containing ovalbumin (OVA) antigen was intramuscularly injected into test mice, which would transform to an OVA-containing gel network for OVA immunization. The results showed that the use of 30 mg/mL PCS-based hydrogel as vaccine delivery system contributed to significantly higher level of antigen-specific immune responses, including higher level of antigen-specific IgG antibodies, IFN-γ and IL-4 cytokines secretion by splenocytes, as well as memory CD4+ and CD8+ T cells. In vivo imaging and immunohistochemistry assays suggest that the improved immunization efficacy may be attributed to the controlled release of antigen from injection site by PCS gel network, and then prolonged antigen stimuli to the immune system. From the results, PCS could be developed as a promising vaccine delivery system for immunotherapy.

TIPS pentacene loaded PEO-PDLLA core-shell nanoparticles have similar cellular uptake dynamics in M1 and M2 macrophages and in corresponding in vivo microenvironments

Nanoparticle based drug delivery platforms have the potential to transform disease treatment paradigms and therapeutic strategies, especially in the context of pulmonary medicine. Once administered, nanoparticles disperse throughout the lung and many are phagocytosed by macrophages. However, there is a paucity of knowledge regarding cellular up-take dynamics of nanoparticles due largely to macrophage heterogeneity. To address this issue, we sought to better define nanoparticle up-take using polarized M1 and M2 macrophages and novel TIPS-pentacene loaded PEO-PDLLA nanoparticles. Our data reveal that primary macrophages polarized to either M1 or M2 phenotypes have similar levels of nanoparticle phagocytosis. Similarly, M1 and M2 polarized macrophages isolated from the lungs of mice following either acute (Th1) or allergic (Th2) airway inflammation also demonstrated equivalent levels of nanoparticle up-take. Together, these studies provide critical benchmark information pertaining to cellular up-take dynamics and biodistribution of nanoparticles in the context of clinically relevant inflammatory microenvironments.

Potential applications of nanoparticles in cancer immunotherapy

In recent years considerable progress has been made in the field of cancer immunotherapy whereby treatments that modulate the body's own immune system are used to combat cancer. This has the potential to not only elicit strong anti-cancer immune responses which can break pre-existing tolerance and help promote tumor regression, but could also induce immunological memory which may help prevent tumor recurrence. In order to ensure effective delivery of immunotherapeutic agents, such as vaccines, checkpoint inhibitors, chemotherapeutic agents and nucleic acids, a safe and effective delivery system is often required. One such approach is the use of multifunctional nanoparticles (NPs), such as liposomes, polymers, micelles, dendrimers, inorganic NPs, and hybrid NPs, which have the potential to combine the delivery of a diverse range of therapeutic immunomodulators thereby increasing the efficacy of tumor cell killing. This review focuses on recent progress in NP-mediated immunotherapy for the treatment of cancer.