Systemically Administered TLR7/8 Agonist and Antigen-Conjugated Nanogels Govern Immune Responses against Tumors

Polyphenol-mediated assembly of toll-like receptor 7/8 agonist nanoparticles for effective tumor immunotherapy

Toll-like receptor (TLR) 7/8 agonists have shown significant potential in tumor immunotherapy. However, the limited pharmacokinetic properties and systemic toxicity resulting from off-target effects limits their biomedical applications. We here report the polyphenol-mediated assembly of resiquimod (R848, a TLR7/8 agonist) nanoparticles (RTP NPs) to achieve tumor-selective immunotherapy while avoiding systemic adverse effects. Upon intravenous administration, the prepared RTP NPs are effectively accumulated at tumor sites, which increase their bioavailability and reduce systemic inflammation. RTP NPs can trigger a potent antitumor immune response in a mouse tumor model to inhibit tumor growth. Additionally, after subcutaneous injection at the tail base, RTP NPs efficiently migrate to the lymph nodes, where they elicit immune memory to prevent tumorigenesis. This study underscores the potential application of polyphenol-mediated assembly in developing nanomedicines with reduced toxicity for tumor-specific immunotherapy. STATEMENT OF SIGNIFICANCE: Toll-like receptor agonist (R848) nanoparticles for tumor-selective immunotherapy were synthesized through polyphenol-mediated assembly, a method that simplifies preparation process and minimizes potential side effects. Intravenously administered these nanoparticles effectively extended circulation time, enhanced tumor enrichment, and reduced systemic inflammation, thus augmenting the bioavailability and minimizing the side effects of R848. The nanoparticles significantly inhibited tumor growth by triggering a potent antitumor immune response, including dendritic cell maturation, macrophage polarization, T-cell infiltration, and cytokine secretion. Moreover, after subcutaneous injection at the tail base, they can elicit immune memory to prevent tumorigenesis.

Toll-like receptor agonists as cancer vaccine adjuvants

Cancer immunotherapy has emerged as a promising strategy to treat cancer patients. Among the wide range of immunological approaches, cancer vaccines have been investigated to activate and expand tumor-reactive T cells. However, most cancer vaccines have not shown significant clinical benefit as monotherapies. This is likely due to the antigen targets of vaccines, "self" proteins to which there is tolerance, as well as to the immunosuppressive tumor microenvironment. To help circumvent immune tolerance and generate effective immune responses, adjuvants for cancer vaccines are necessary. One representative adjuvant family is Toll-Like receptor (TLR) agonists, synthetic molecules that stimulate TLRs. TLRs are the largest family of pattern recognition receptors (PRRs) that serve as the sensors of pathogens or cellular damage. They recognize conserved foreign molecules from pathogens or internal molecules from cellular damage and propel innate immune responses. When used with vaccines, activation of TLRs signals an innate damage response that can facilitate the development of a strong adaptive immune response against the target antigen. The ability of TLR agonists to modulate innate immune responses has positioned them to serve as adjuvants for vaccines targeting infectious diseases and cancers. This review provides a summary of various TLRs, including their expression patterns, their functions in the immune system, as well as their ligands and synthetic molecules developed as TLR agonists. In addition, it presents a comprehensive overview of recent strategies employing different TLR agonists as adjuvants in cancer vaccine development, both in pre-clinical models and ongoing clinical trials.

Multimodal targeting chimeras enable integrated immunotherapy leveraging tumor-immune microenvironment

Although immunotherapy has revolutionized cancer treatment, its efficacy is affected by multiple factors, particularly those derived from the complexity and heterogeneity of the tumor-immune microenvironment (TIME). Strategies that simultaneously and synergistically engage multiple immune cells in TIME remain highly desirable but challenging. Herein, we report a multimodal and programmable platform that enables the integration of multiple therapeutic modules into single agents for tumor-targeted co-engagement of multiple immune cells within TIME. We developed the triple orthogonal linker (T-Linker) technology to integrate various therapeutic small molecules and biomolecules as multimodal targeting chimeras (Multi-TACs). The EGFR-CD3-PDL1 Multi-TAC facilitated T-dendritic cell co-engagement to target solid tumors with excellent efficacy, as demonstrated in vitro, in several humanized mouse models and in patient-derived tumor models. Furthermore, Multi-TACs were constructed to coordinate T cells with other immune cell types. The highly modular and programmable feature of our Multi-TACs may find broad applications in immunotherapy and beyond.

Toward Intracellular Delivery: Aliphatic Polycarbonates with Pendant Thiol-Reactive Thiosulfonates for Reversible Postpolymerization Modification

Postpolymerization modifications are valuable techniques for creating functional polymers that are challenging to synthesize directly. This study presents aliphatic polycarbonates with pendant thiol-reactive groups for disulfide formation with mercaptans. The reductive responsive nature of this reaction allows for reversible postpolymerization modifications on biodegradable scaffolds. Six-membered cyclic carbonate monomers with pendant thiosulfonate groups were synthesized and polymerized using controlled organocatalytic ring-opening polymerization, yielding polymers with narrow molecular weight dispersities (Đ = 1.2) and intact reactive thiosulfonate side chains. Reversible modification with benzyl mercaptans achieved high degrees of disulfide modification. Additionally, thiol-reactive carbonate monomers were block-copolymerized onto polyethylene glycol (mPEG113) and then converted into benzyl disulfides, while the block copolymers' hydroxyl end groups remained available for fluorescent dye labeling. The amphiphilic block copolymers self-assembled in water into micelles (∼33 nm diameter), capable of encapsulating hydrophobic molecules. These micelles successfully delivered hydrophobic dyes into macrophages, indicating the potential for intracellular drug delivery.

PH-Triggered, Lymph Node Focused Immunodrug Release by Polymeric 2-Propionic-3-Methyl-maleic Anhydrides with Cholesteryl End Groups

Gaining spatial control over innate immune activation is of great relevance during vaccine delivery and anticancer therapy, where one aims at activating immune cells at draining lymphoid tissue while avoiding systemic off-target innate immune activation. Lipid-polymer amphiphiles show high tendency to drain to lymphoid tissue upon local administration. Here, pH-sensitive, cholesteryl end group functionalized polymers as stimuli-responsive carriers are introduced for controlled immunoactivation of draining lymph nodes. Methacrylamide-based monomers bearing pendant 2-propionic-3-methylmaleic anhydride groups are polymerized by Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization using a cholesterol chain-transfer agent (chol-CTA). The amine-reactive anhydrides are conjugated with various amines, however, while primary amines afforded irreversible imides, secondary amines provided pH-responsive conjugates that are released upon acidification. This can be applied to fluorescent dyes for irreversibly carrier labeling or immunostimulatory Toll-like receptor (TLR) 7/8 agonists as cargos for pH-responsive delivery. Hydrophilization of remaining anhydride repeating units with short PEG-chains yielded cholesteryl-polymer amphiphiles that showed efficient cellular uptake and increased drug release at endosomal pH. Moreover, reversibly conjugated TLR 7/8 agonist amphiphiles efficiently drained to lymph nodes and increased the number of effectively maturated antigen-presenting cells after subcutaneous injection in vivo. Consequently, cholesteryl-linked methacrylamide-based polymers with pH-sensitive 2-propionic-3-methylmaleic anhydride side groups provide ideal features for immunodrug delivery.

Aliphatic polycarbonates with acid degradable ketal side groups as multi-pH-responsive immunodrug nanocarriers

Pharmacokinetics and biodistribution profiles of active substances are crucial aspects for their safe and successful administration. Since many immunogenic compounds do not meet all requirements for safe and effective administration, well-defined drug nanocarrier systems are necessary with a stimuli-responsive drug-release profile. For this purpose, a novel pH-responsive aliphatic cyclic carbonate is introduced with benzyl ketal side chains and polymerized onto a poly(ethylene glycol) macroinitiator. The resulting block copolymers could be formulated via a solvent-evaporation method into well-defined polymeric micelles. The hydrophobic carbonate block was equipped with an acid degradable ketal side group that served as an acid-responsive functional group. Already subtle pH alternations led to micelle disassembly and the release of the active cargo. Furthermore, basic carbonate backbone degradation assured the pH responsiveness of the nanocarriers in both acidic and basic conditions. To investigate the delivery capacity of polymeric micelles, the model small molecule compound CL075, which serves as an immunotherapeutic TLR7/8 agonist, was encapsulated. Incubation studies with human blood plasma revealed the absence of undesirable protein adsorption on the drug-loaded nanoparticles. Furthermore, in vitro applications confirmed cell uptake of the nanodrug formulations by macrophages and the induction of payload-mediated immune stimulation. Altogether, these results underline the huge potential of the developed multi-pH-responsive polymeric nanocarrier for immunodrug delivery.

Discovery and Evaluation of TLR-Targeted Immune Agonists

Toll-like receptor (TLR) activation converts immunologically inactive tumors into immunologically active tumors by activating tumor residing antigen-presenting cells and recruitment of cytotoxic T lymphocytes. Targeted immune agonists (TIAs) are antibody drug conjugates with small-molecule TLR agonist payloads. The mechanism of action of TIAs involves tumor antigen recognition, Fcγ-receptor-dependent phagocytosis, and TLR-mediated activation to drive tumor killing by myeloid cells. Several new low DAR anti-HER2 TIAs conjugated with novel TLR7 or dual-TLR7/8 agonists with cleavable and noncleavable linkers were synthesized and profiled. In vitro studies demonstrated that these TIAs activate myeloid cells only in the presence of antigen-expressing cancer cells. Evaluation in ELISpot-based assays confirmed the low immunogenicity of these constructs. Systemic administration of the novel TIAs in tumor-bearing mice resulted in tumor reduction at low doses. These results provide a strong rationale for further development of the TIAs as a novel class of immunotherapeutics.

Concepts and Approaches to Reduce or Avoid Protein Corona Formation on Nanoparticles: Challenges and Opportunities

This review describes the formation of a protein corona (or its absence) on different classes of nanoparticles, its basic principles, and its consequences for nanomedicine. For this purpose, it describes general concepts to control (guide/minimize) the interaction between artificial nanoparticles and plasma proteins to reduce protein corona formation. Thereafter, methods for the qualitative or quantitative determination of protein corona formation are presented, as well as the properties of nanoparticle surfaces, which are relevant for protein corona prevention (or formation). Thereby especially the role of grafting density of hydrophilic polymers on the surface of the nanoparticle is discussed to prevent the formation of a protein corona. In this context also the potential of detergents (surfactants) for a temporary modification as well as grafting-to and grafting-from approaches for a permanent modification of the surface are discussed. The review concludes by highlighting several promising avenues. This includes (i) the use of nanoparticles without protein corona for active targeting, (ii) the use of synthetic nanoparticles without protein corona formation to address the immune system, (iii) the recollection of nanoparticles with a defined protein corona after in vivo application to sample the blood proteome and (iv) further concepts to reduce protein corona formation.

Engineering customized nanovaccines for enhanced cancer immunotherapy

Nanovaccines have gathered significant attention for their potential to elicit tumor-specific immunological responses. Despite notable progress in tumor immunotherapy, nanovaccines still encounter considerable challenges such as low delivery efficiency, limited targeting ability, and suboptimal efficacy. With an aim of addressing these issues, engineering customized nanovaccines through modification or functionalization has emerged as a promising approach. These tailored nanovaccines not only enhance antigen presentation, but also effectively modulate immunosuppression within the tumor microenvironment. Specifically, they are distinguished by their diverse sizes, shapes, charges, structures, and unique physicochemical properties, along with targeting ligands. These features of nanovaccines facilitate lymph node accumulation and activation/regulation of immune cells. This overview of bespoke nanovaccines underscores their potential in both prophylactic and therapeutic applications, offering insights into their future development and role in cancer immunotherapy.

Therapeutic Applications of Nanomedicine: Recent Developments and Future Perspectives

The concept of nanomedicine has evolved significantly in recent decades, leveraging the unique phenomenon known as the enhanced permeability and retention (EPR) effect. This has facilitated major advancements in targeted drug delivery, imaging, and individualized therapy through the integration of nanotechnology principles into medicine. Numerous nanomedicines have been developed and applied for disease treatment, with a particular focus on cancer therapy. Recently, nanomedicine has been utilized in various advanced fields, including diagnosis, vaccines, immunotherapy, gene delivery, and tissue engineering. Multifunctional nanomedicines facilitate concurrent medication delivery, therapeutic monitoring, and imaging, allowing for immediate responses and personalized treatment plans. This review concerns the major advancement of nanomaterials and their potential applications in the biological and medical fields. Along with this, we also mention the various clinical translations of nanomedicine and the major challenges that nanomedicine is currently facing to overcome the clinical translation barrier.

A Programmable Peptidic Hydrogel Adjuvant for Personalized Immunotherapy in Resected Stage Tumors

Adjuvant treatment after surgical resection usually plays an important role in delaying disease recurrence. Immunotherapy displays encouraging results in increasing patients' chances of staying cancer-free after surgery, as reported by recent clinical trials. However, the clinical outcomes of current immunotherapy need to be improved due to the limited responses, patient heterogeneity, nontargeted distribution, and immune-related adverse effects. This work describes a programmable hydrogel adjuvant for personalized immunotherapy after surgical resection. By filling the hydrogel in the cavity, this system aims to address the limited secretion of granzyme B (GrB) during immunotherapy and improve the low immunotherapy responses typically observed, while minimizing immune-related side effects. The TLR7/8 agonist imidazoquinoline (IMDQ) is linked to the self-assembling peptide backbone through a GrB-responsive linkage. Its release could enhance the activation and function of immune cells, which will lead to increased secretion of GrB and enhance the effectiveness of immunotherapy together. The hydrogel adjuvant recruits immune cells, initiates dendritic cell maturation, and induces M1 polarized macrophages to reverse the immunosuppressive tumor microenvironment in situ. In multiple murine tumor models, the hydrogel adjuvant suppresses tumor growth, increases animal survival and long-term immunological memory, and protects mice against tumor rechallenge, leading to effective prophylactic and therapeutic responses. This work provides a potential chemical strategy to overcome the limitations associated with immunotherapy.

Co-Delivery of a Novel Lipidated TLR7/8 Agonist and Hemagglutinin-Based Influenza Antigen Using Silica Nanoparticles Promotes Enhanced Immune Responses

Co-delivery of antigens and adjuvants to the same antigen-presenting cells (APCs) can significantly improve the efficacy and safety profiles of vaccines. Here, we report amine-grafted silica nanoparticles (A-SNP) as a tunable vaccine co-delivery platform for TLR7/8 agonists along with the recombinant influenza antigen hemagglutinin H7 (H7) to APCs. A-SNP of two different sizes (50 and 200 nm) were prepared and coated with INI-4001 at different coating densities, followed by co-adsorption of H7. Both INI-4001 and H7 showed >90% adsorption to the tested A-SNP formulations. TNF-α and IFN-α cytokine release by human peripheral blood mononuclear cells as well as TNF-α, IL-6, and IL-12 release by mouse bone marrow-derived dendritic cells revealed that the potency of the INI-4001-adsorbed A-SNP (INI-4001/A-SNP) formulations was improved relative to aqueous formulation control. This improved potency was dependent on particle size and ligand coating density. In addition, slow-release profiles of INI-4001 were measured from INI-4001/A-SNP formulations in plasma with 30-50% INI-4001 released after 7 days. In vivo murine immunization studies demonstrated significantly improved H7-specific humoral and Th1/Th17-polarized T cell immune responses with no observed adverse reactions. Low-density 50 nm INI-4001/A-SNP elicited significantly higher IFN-γ and IL-17 induction over that of the H7 antigen-only group and INI-4001 aqueous formulation controls. In summary, this work introduces an effective and biocompatible SNP-based co-delivery platform that enhances the immunogenicity of TLR7/8 agonist-adjuvanted subunit influenza vaccines.

Facile Preparation of Carbohydrate-Containing Adjuvants Based on Self-Assembling Glycopeptide Conjugates

Carbohydrates are intriguing biomolecules possessing diverse biological activities, including immune stimulating capability. However, their biomedical applications have been limited by their complex and heterogeneous structures. In this study, we have utilized a self-assembling glycopeptide conjugate (GPC) system to produce uniform nanoribbons appending homogeneous oligosaccharides with multivalency. This system successfully translates the nontrivial structural differences of oligomannoses into varied binding affinities to C-type lectin receptors (CLRs). We have shown that GPCs could promote the CLR-mediated endocytosis of ovalbumin (OVA) antigen, and two mannotriose-modified peptides F3m2 and F3m5 exhibit potent activity in inducing antigen-presenting cell maturation, as indicated by increased CD86 and MHCII expression. In vivo studies demonstrated that GPCs, combined with OVA antigen, significantly enhanced OVA-specific antibody production. Specifically, F3m2 and F3m5 exhibited the highest immunostimulatory effects, eliciting both Th1- and Th2-biased immune responses and promoting differentiation of CD4+ and CD8+  T cells. These findings highlight the potential of GPCs as vaccine adjuvants, and showcase their versatility in exploiting the biological functions of carbohydrates.

Exploring the Potential of Nanogels: From Drug Carriers to Radiopharmaceutical Agents

Nanogels open up access to a wide range of applications and offer among others hopeful approaches for use in the field of biomedicine. This review provides a brief overview of current developments of nanogels in general, particularly in the fields of drug delivery, therapeutic applications, tissue engineering, and sensor systems. Specifically, cyclodextrin (CD)-based nanogels are important because they have exceptional complexation properties and are highly biocompatible. Nanogels as a whole and CD-based nanogels in particular can be customized in a wide range of sizes and equipped with a desired surface charge as well as containing additional molecules inside and outside, such as dyes, solubility-mediating groups or even biological vector molecules for pharmaceutical targeting. Currently, biological investigations are mainly carried out in vitro, but more and more in vivo applications are gaining importance. Modern molecular imaging methods are increasingly being used for the latter. Due to an extremely high sensitivity and the possibility of obtaining quantitative data on pharmacokinetic and pharmacodynamic properties, nuclear methods such as single photon emission computed tomography (SPECT) and positron emission tomography (PET) using radiolabeled compounds are particularly suitable here. The use of radiolabeled nanogels for imaging, but also for therapy, is being discussed.

Polymerizable 2-Propionic-3-methylmaleic Anhydrides as a Macromolecular Carrier Platform for pH-Responsive Immunodrug Delivery

The design of functional polymers coupled with stimuli-triggered drug release mechanisms is a promising achievement to overcome various biological barriers. pH trigger methods yield significant potential for controlled targeting and release of therapeutics due to their simplicity and relevance, especially upon cell internalization. Here, we introduce reactive polymers that conjugate primary or secondary amines and release potential drugs under acidic conditions. For that purpose, we introduced methacrylamide-based monomers with pendant 2-propionic-3-methylmaleic anhydride groups. Such groups allow the conjugation of primary and secondary amines but are resistant to radical polymerization conditions. We, therefore, polymerized 2-propionic-3-methylmaleic anhydride amide-based methacrylates via reversible addition-fragmentation chain transfer (RAFT) polymerization. Their amine-reactive anhydrides could sequentially be derivatized by primary or secondary amines into hydrophilic polymers. Acidic pH-triggered drug release from the polymeric systems was fine-tuned by comparing different amines. Thereby, the conjugation of primary amines led to the formation of irreversible imide bonds in dimethyl sulfoxide, while secondary amines could quantitatively be released upon acidification. In vitro, this installed pH-responsiveness can contribute to an effective release of conjugated immune stimulatory drugs under endosomal pH conditions. Interestingly, the amine-modified polymers generally showed no toxicity and a high cellular uptake. Furthermore, secondary amine-modified immune stimulatory drugs conjugated to the polymers yielded better receptor activity and immune cell maturation than their primary amine derivatives due to their pH-sensitive drug release mechanism. Consequently, 2-propionic-3-methylmaleic anhydride-based polymers can be considered as a versatile platform for pH-triggered delivery of various (immuno)drugs, thus enabling new strategies in macromolecule-assisted immunotherapy.

Polymer-Protein Nanovaccine Synthesized via Reactive Self-Assembly with Potential Application in Cancer Immunotherapy: Physicochemical and Biological Characterization In Vitro and In Vivo

Nanovaccines composed of polymeric nanocarriers and protein-based antigens have attracted much attention in recent years because of their enormous potential in the prevention and treatment of diseases such as viral infections and cancer. While surface-conjugated protein antigens are known to be more immunoactive than encapsulated antigens, current surface conjugation methods often result in low and insufficient protein loading. Herein, reactive self-assembly is used to prepare nanovaccine from poly(ε-caprolactone) (PCL) and ovalbumin (OVA)-a model antigen. A rapid thiol-disulfide exchange reaction between PCL with pendant pyridyl disulfide groups and thiolated OVA results in the formation of nanoparticles with narrow size distribution. High OVA loading (≈70-80 wt%) is achieved, and the native secondary structure of OVA is preserved. Compared to free OVA, the nanovaccine is much superior in enhancing antigen uptake by bone marrow-derived dendritic cells (BMDCs), promoting BMDC maturation and antigen presentation via the MHC I pathway, persisting at the injection site and draining lymph nodes, activating both Th1 and Th2 T cell immunity, and ultimately, resisting tumor challenge in mice. This is the first demonstration of reactive self-assembly for the construction of a polymer-protein nanovaccine with clear potential in advancing cancer immunotherapy.

Potentiating cancer vaccination by adjuvant-loaded cryo-shocked tumor cells

Cancer vaccine holds vast promise in potentiating tumor immunotherapy. Here, we developed a simple cancer vaccine based on the liquid nitrogen-treated cells (LNT cells) that engineered by one-shot shocking of the live tumor cells in liquid nitrogen. In this vaccine, the obtained LNT cells served as both tumor antigens and delivery vehicles to load the adjuvant imiquimod (R837). This design could achieve efficient co-uptake of antigen/adjuvant by antigen presenting cells (APCs) and prolong in vivo retention of tumor antigens and adjuvants. This adjuvant-loaded LNT cells augmented in vivo antitumor responses and enhanced survival in melanoma-bearing mouse model compared with conventional whole-cell vaccine of the mixture of tumor lysis and adjuvant.

Peptide-Decorated Degradable Polycarbonate Nanogels for Eliciting Antigen-Specific Immune Responses

For successful therapeutic interventions in cancer immunotherapy, strong antigen-specific immune responses are required. To this end, immunostimulating cues must be combined with antigens to simultaneously arrive at antigen-presenting cells and initiate cellular immune responses. Recently, imidazoquinolines have shown their vast potential as small molecular Toll-like receptor 7/8 (TLR7/8) agonists for immunostimulation when delivered by nanocarriers. At the same time, peptide antigens are promising antigen candidates but require combination with immune-stimulating adjuvants to boost their immunogenicity and exploit their full potential. Consequently, we herein present biodegradable polycarbonate nanogels as versatile delivery system for adjuvants within the particles' core as well as for peptide antigens by surface decoration. For that purpose, orthogonally addressable multifunctional polycarbonate block copolymers were synthesized, enabling adjuvant conjugation through reactive ester chemistry and peptide decoration by strain-promoted alkyne-azide cycloaddition (SPAAC). In preparation for SPAAC, CD4+-specific peptide sequences of the model protein antigen ovalbumin were equipped with DBCO-moieties by site-selective modification at their N-terminal cysteine. With their azide groups exposed on their surface, the adjuvant-loaded nanogels were then efficiently decorated with DBCO-functional CD4+-peptides by SPAAC. In vitro evaluation of the adjuvant-loaded peptide-decorated gels then confirmed their strong immunostimulating properties as well as their high biocompatibility. Despite their covalent conjugation, the CD4+-peptide-decorated nanogels led to maturation of primary antigen-presenting cells and the downstream priming of CD4+-T cells. Subsequently, the peptide-decorated nanogels loaded with TLR7/8 agonist were successfully processed by antigen-presenting cells, enabling potent immune responses for future application in antigen-specific cancer immunotherapy.

Tumor-infiltrating CCR2+ inflammatory monocytes counteract specific immunotherapy

Tumor development and progression is shaped by the tumor microenvironment (TME), a heterogeneous assembly of infiltrating and resident host cells, their secreted mediators and intercellular matrix. In this context, tumors are infiltrated by various immune cells with either pro-tumoral or anti-tumoral functions. Recently, we published our non-invasive immunization platform DIVA suitable as a therapeutic vaccination method, further optimized by repeated application (DIVA2). In our present work, we revealed the therapeutic effect of DIVA2 in an MC38 tumor model and specifically focused on the mechanisms induced in the TME after immunization. DIVA2 resulted in transient tumor control followed by an immune evasion phase within three weeks after the initial tumor inoculation. High-dimensional flow cytometry analysis and single-cell mRNA-sequencing of tumor-infiltrating leukocytes revealed cytotoxic CD8+ T cells as key players in the immune control phase. In the immune evasion phase, inflammatory CCR2+ PDL-1+ monocytes with immunosuppressive properties were recruited into the tumor leading to suppression of DIVA2-induced tumor-reactive T cells. Depletion of CCR2+ cells with specific antibodies resulted in prolonged survival revealing CCR2+ monocytes as important for tumor immune escape in the TME. In summary, the present work provides a platform for generating a strong antigen-specific primary and memory T cell immune response using the optimized transcutaneous immunization method DIVA2. This enables protection against tumors by therapeutic immune control of solid tumors and highlights the immunosuppressive influence of tumor infiltrating CCR2+ monocytes that need to be inactivated in addition for successful cancer immunotherapy.

Improving the efficacy of peptide vaccines in cancer immunotherapy

Peptide vaccines have shown great potential in cancer immunotherapy by targeting tumor antigens and activating the patient's immune system to mount a specific response against cancer cells. However, the efficacy of peptide vaccines in inducing a sustained immune response and achieving clinical benefit remains a major challenge. In this review, we discuss the current status of peptide vaccines in cancer immunotherapy and strategies to improve their efficacy. We summarize the recent advancements in the development of peptide vaccines in pre-clinical and clinical settings, including the use of novel adjuvants, neoantigens, nano-delivery systems, and combination therapies. We also highlight the importance of personalized cancer vaccines, which consider the unique genetic and immunological profiles of individual patients. We also discuss the strategies to enhance the immunogenicity of peptide vaccines such as multivalent peptides, conjugated peptides, fusion proteins, and self-assembled peptides. Although, peptide vaccines alone are weak immunogens, combining peptide vaccines with other immunotherapeutic approaches and developing novel approaches such as personalized vaccines can be promising methods to significantly enhance their efficacy and improve the clinical outcomes for cancer patients.

Research progress of nanovaccine in anti-tumor immunotherapy

Tumor vaccines aim to activate dormant or unresponsive tumor-specific T lymphocytes by using tumor-specific or tumor-associated antigens, thus enhancing the body's natural defense against cancer. However, the effectiveness of tumor vaccines is limited by the presence of tumor heterogeneity, low immunogenicity, and immune evasion mechanisms. Fortunately, multifunctional nanoparticles offer a unique chance to address these issues. With the advantages of their small size, high stability, efficient drug delivery, and controlled surface chemistry, nanomaterials can precisely target tumor sites, improve the delivery of tumor antigens and immune adjuvants, reshape the immunosuppressive tumor microenvironment, and enhance the body's anti-tumor immune response, resulting in improved efficacy and reduced side effects. Nanovaccine, a type of vaccine that uses nanotechnology to deliver antigens and adjuvants to immune cells, has emerged as a promising strategy for cancer immunotherapy due to its ability to stimulate immune responses and induce tumor-specific immunity. In this review, we discussed the compositions and types of nanovaccine, and the mechanisms behind their anti-tumor effects based on the latest research. We hope that this will provide a more scientific basis for designing tumor vaccines and enhancing the effectiveness of tumor immunotherapy.

Influence of the Composition of Cationic Liposomes on the Performance of Cargo Immunostimulatory RNA

In this study, the impact of different delivery systems on the cytokine-inducing, antiproliferative, and antitumor activities of short immunostimulatory double-stranded RNA (isRNA) was investigated. The delivery systems, consisting of the polycationic amphiphile 1,26-bis(cholest-5-en-3-yloxycarbonylamino)-7,11,16,20 tetraazahexacosan tetrahydrochloride (2X3), and the lipid-helper dioleoylphosphatidylethanolamine (DOPE), were equipped with polyethylene glycol lipoconjugates differing in molecular weight and structure. The main findings of this work are as follows: (i) significant activation of MCP-1 and INF-α, β, and γ production in CBA mice occurs under the action of isRNA complexes with liposomes containing lipoconjugates with long PEG chains, while activation of MCP-1 and INF-γ, but not INF-α or β, was observed under the action of isRNA lipoplexes containing lipoconjugates with short PEG chains; (ii) a pronounced antiproliferative effect on B16 melanoma cells in vitro, as well as an antitumor and hepatoprotective effect in vivo, was induced by isRNA pre-complexes with non-pegylated liposomes, while complexes containing lipoconjugates with long-chain liposomes were inactive; (iii) the antitumor activity of isRNA correlated with the efficiency of its accumulation in the cells and did not explicitly depend on the activation of cytokine and interferon production. Thus, the structure of the delivery system plays a vital role in determining the response to isRNA and allows for the choice of a delivery system depending on the desired effect.

Caveolin-mediated cytosolic delivery of spike nanoparticle enhances antitumor immunity of neoantigen vaccine for hepatocellular carcinoma

Rationale: Although neoantigen-based cancer vaccines have shown promise in various solid tumors, limited immune responses and clinical outcomes have been reported in patients with advanced disease. Cytosolic transport of neoantigen and adjuvant is required for the activation of intracellular Toll-like receptors (TLRs) and cross-presentation to prime neoantigen-specific CD8+T cells but remains a significant challenge. Methods: In this study, we aimed to develop a virus-like silicon vaccine (V-scVLPs) with a unique spike topological structure, capable of efficiently co-delivering a hepatocellular carcinoma (HCC)-specific neoantigen and a TLR9 agonist to dendritic cells (DCs) to induce a robust CD8+T cell response to prevent orthotopic tumor growth. We evaluated the antitumor efficacy of V-scVLPs by examining tumor growth and survival time in animal models, as well as analyzing tumor-infiltrating CD8+T cells and cytokine responses in the tumor microenvironment (TME). To evaluate the synergistic efficacy of V-scVLPs in combination with α-TIM-3 in HCC, we used an orthotopic HCC mouse model, a lung metastasis model, and a tumor rechallenge model after hepatectomy. Results: We found that V-scVLPs can efficiently co-deliver the hepatocellular carcinoma (HCC)-specific neoantigen and the TLR9 agonist to DCs via caveolin-mediated endocytosis. This advanced delivery strategy results in efficient lymph node draining of V-scVLPs to activate lymphoid DC maturation for promoting robust CD8+T cells and central memory T cells responses, which effectively prevents orthotopic HCC tumor growth. However, in the established orthotopic liver tumor models, the inhibitory receptor of TIM-3 was significantly upregulated in tumor-infiltrating CD8+T cells after immunization with V-scVLPs. Blocking the TIM-3 signaling further restored the antitumor activity of V-scVLPs-induced CD8+T cells, reduced the proportion of regulatory T cells, and increased the levels of cytokines to alter the tumor microenvironment to efficiently suppress established orthotopic HCC tumor growth, and inhibit lung metastasis as well as recurrence after hepatectomy. Conclusion: Overall, the developed novel spike nanoparticles with efficient neoantigen and adjuvant intracellular delivery capability holds great promise for future clinical translation to improve HCC immunotherapy.

Stimuli-Responsive Polymeric Nanovaccines Toward Next-Generation Immunotherapy

The development of nanovaccines that employ polymeric delivery carriers has garnered substantial interest in therapeutic treatment of cancer and a variety of infectious diseases due to their superior biocompatibility, lower toxicity and reduced immunogenicity. Particularly, stimuli-responsive polymeric nanocarriers show great promise for delivering antigens and adjuvants to targeted immune cells, preventing antigen degradation and clearance, and increasing the uptake of specific antigen-presenting cells, thereby sustaining adaptive immune responses and improving immunotherapy for certain diseases. In this review, the most recent advances in the utilization of stimulus-responsive polymer-based nanovaccines for immunotherapeutic applications are presented. These sophisticated polymeric nanovaccines with diverse functions, aimed at therapeutic administration for disease prevention and immunotherapy, are further classified into several active domains, including pH, temperature, redox, light and ultrasound-sensitive intelligent nanodelivery systems. Finally, the potential strategies for the future design of multifunctional next-generation polymeric nanovaccines by integrating materials science with biological interface are proposed.

Efficient Self-Immolative RAFT End Group Modification for Macromolecular Immunodrug Delivery

The reversible addition-fragmentation chain-transfer (RAFT) polymerization provides access to a broad variety of biocompatible and functional macromolecules for diverse polymer-drug conjugates. Due to thiocarbonylthio groups at the ends of each growing polymer chain, they can straightforwardly be converted into disufilde-containing self-immolative motives for reversible drug conjugation by traceless linkers. This may be relevant for RAFT-polymerized poly(N,N-dimethylacrylamide) (pDMA), which has been demonstrated to provide similar properties as poly(ethylene glycol) (PEG) in terms of improving the drug's poor pharmacokinetic profile or enhancing its bioavailability. For that purpose, we established a highly efficient one-pot reaction procedure for introducing various functionalities including both primary and secondary amines and primary alcohols and demonstrated their reversible conjugation and traceless release from pDMA's polymer chain end. Next, a first polymer-drug conjugate with a Toll-like receptor agonist exhibited significantly increased activity in vitro compared to conventional irreversibly covalently fixed variants. Finally, α-ω-bifunctional dye or drug conjugates could be generated by a cholesterol-modified RAFT chain-transfer agent. It facilitated the polymer-drug conjugate's internalization at the cellular level monitored by flow cytometry and confocal imaging. This approach provides the basis for a variety of potentially impactful polymer-drug conjugates by combining versatile small molecular drugs with a plethora of available RAFT polymers through reductive-responsive self-immolative linkers.

Photoactivatable nanoagonists chemically programmed for pharmacokinetic tuning and in situ cancer vaccination

Immunotherapy holds great promise for the treatment of aggressive and metastatic cancers; however, currently available immunotherapeutics, such as immune checkpoint blockade, benefit only a small subset of patients. A photoactivatable toll-like receptor 7/8 (TLR7/8) nanoagonist (PNA) system that imparts near-infrared (NIR) light-induced immunogenic cell death (ICD) in dying tumor cells in synchrony with the spontaneous release of a potent immunoadjuvant is developed here. The PNA consists of polymer-derived proimmunoadjuvants ligated via a reactive oxygen species (ROS)-cleavable linker and polymer-derived photosensitizers, which are further encapsulated in amphiphilic matrices for systemic injection. In particular, conjugation of the TLR7/8 agonist resiquimod to biodegradable macromolecular moieties with different molecular weights enabled pharmacokinetic tuning of small-molecule agonists and optimized delivery efficiency in mice. Upon NIR photoirradiation, PNA effectively generated ROS not only to ablate tumors and induce the ICD cascade but also to trigger the on-demand release of TLR agonists. In several preclinical cancer models, intravenous PNA administration followed by NIR tumor irradiation resulted in remarkable tumor regression and suppressed postsurgical tumor recurrence and metastasis. Furthermore, this treatment profoundly shifted the tumor immune landscape to a tumoricidal one, eliciting robust tumor-specific T cell priming in vivo. This work highlights a simple and cost-effective approach to generate in situ cancer vaccines for synergistic photodynamic immunotherapy of metastatic cancers.

Engineering magnetic nano-manipulators for boosting cancer immunotherapy

Cancer immunotherapy has shown promising therapeutic results in the clinic, albeit only in a limited number of cancer types, and its efficacy remains less than satisfactory. Nanoparticle-based approaches have been shown to increase the response to immunotherapies to address this limitation. In particular, magnetic nanoparticles (MNPs) as a powerful manipulator are an appealing option for comprehensively regulating the immune system in vivo due to their unique magnetically responsive properties and high biocompatibility. This review focuses on assessing the potential applications of MNPs in enhancing tumor accumulation of immunotherapeutic agents and immunogenicity, improving immune cell infiltration, and creating an immunotherapy-sensitive environment. We summarize recent progress in the application of MNP-based manipulators to augment the efficacy of immunotherapy, by MNPs and their multiple magnetically responsive effects under different types of external magnetic field. Furthermore, we highlight the mechanisms underlying the promotion of antitumor immunity, including magnetically actuated delivery and controlled release of immunotherapeutic agents, tracking and visualization of immune response in real time, and magnetic regulation of innate/adaptive immune cells. Finally, we consider perspectives and challenges in MNP-based immunotherapy.

Tumor-Selective Activation of Toll-Like Receptor 7/8 Agonist Nano-Immunomodulator Generates Safe Anti-Tumor Immune Responses upon Systemic Administration

Agonists of innate pattern recognition receptors such as toll-like receptors (TLRs) prime adaptive anti-tumor immunity and hold promise for cancer immunotherapy. However, small-molecule TLR agonists cause immune-related adverse effects (irAEs) after systemic administration. Herein, we report a polymeric nano-immunomodulator (cN@SS-IMQ) that is inactive until it is selectively metabolized to an active immunostimulant within the tumor. cN@SS-IMQ was obtained via self-assembly of a cyclo(Arg-Gly-Asp-D-Phe-Lys)-modified amphiphilic copolymeric prodrug. Upon systemic administration, cN@SS-IMQ preferentially accumulated at tumor sites and responded to high intracellular glutathione levels to release native imidazoquinolines for dendritic cell maturation, thereby enhancing the infiltration of T lymphocytes. Collectively, cN@SS-IMQ tends to activate the immune system without irAEs, thus suggesting its promising potential for safe systemic targeting delivery.

Pairing Nanoparticles Geometry with TLR Agonists to Modulate Immune Responses for Vaccine Development

Nanotechnology-based vaccine development necessitates understanding the crucial biophysical properties of nanostructures that alter immune responses. In this study, we demonstrate the synergistic effect of gold nanoparticles (AuNPs) shapes with toll-like receptor (TLR) agonists in immune modulation activity. Our results showed that CpG- and imidazoquinoline-conjugated rod-shaped AuNPs display relatively fast uptake by bone marrow-derived macrophage cells but exhibit poor immunogenic responses compared to their spherical and star-shaped AuNP counterparts. Surprisingly, star-shaped AuNPs exhibited intense pro-inflammatory cytokine secretion. Further mechanistic studies showed that star-shaped AuNPs were abundantly localized in the late endosome and lysosomal regions, whereas rod-shaped AuNPs were majorly sequestered in the mitochondrial region. These findings reveal that the shape of the nanostructures plays a pivotal role in driving the adjuvant molecules toward their receptors and altering immune responses.

Recent Advances in the Biomedical Applications of Functionalized Nanogels

Nanomaterials have been extensively used in several applications in the past few decades related to biomedicine and healthcare. Among them, nanogels (NGs) have emerged as an important nanoplatform with the properties of both hydrogels and nanoparticles for the controlled/sustained delivery of chemo drugs, nucleic acids, or other bioactive molecules for therapeutic or diagnostic purposes. In the recent past, significant research efforts have been invested in synthesizing NGs through various synthetic methodologies such as free radical polymerization, reversible addition-fragmentation chain-transfer method (RAFT) and atom transfer radical polymerization (ATRP), as well as emulsion techniques. With further polymeric functionalizations using activated esters, thiol-ene/yne processes, imines/oximes formation, cycloadditions, nucleophilic addition reactions of isocyanates, ring-opening, and multicomponent reactions were used to obtain functionalized NGs for targeted delivery of drug and other compounds. NGs are particularly intriguing for use in the areas of diagnosis, analytics, and biomedicine due to their nanodimensionality, material characteristics, physiological stability, tunable multi-functionality, and biocompatibility. Numerous NGs with a wide range of functionalities and various external/internal stimuli-responsive modalities have been possible with novel synthetic reliable methodologies. Such continuous development of innovative, intelligent materials with novel characteristics is crucial for nanomedicine for next-generation biomedical applications. This paper reviews the synthesis and various functionalization strategies of NGs with a focus on the recent advances in different biomedical applications of these surface modified/functionalized single-/dual-/multi-responsive NGs, with various active targeting moieties, in the fields of cancer theranostics, immunotherapy, antimicrobial/antiviral, antigen presentation for the vaccine, sensing, wound healing, thrombolysis, tissue engineering, and regenerative medicine.

Nanovaccines: Merits, and diverse roles in boosting antitumor immune responses

An attractive type of cancer immunotherapy is cancer therapeutic vaccines that induce antitumor immunity effectively. Although supportive results in the recent vaccine studies, there are still numerous drawbacks, such as poor stability, weak immunogenicity and strong toxicity, to be tackled for promoting the potency and durability of antitumor efficacy. NPs (Nanoparticles)-based vaccines offer unique opportunities to breakthrough the current bottleneck. As a rule, nanovaccines are new the generations of vaccines that use NPs as carriers and/or adjuvants. Several advantages of nanovaccines are constantly explored, including optimal nanometer size, high stability, plenty of antigen loading, enhanced immunogenicity, tunable antigen presentation, more retention in lymph nodes and promote patient compliance by a lower frequency of dosing. Here, we summarized the merits and highlight the diverse role nanovaccines play in improving antitumor responses.

Bioengineered nanogels for cancer immunotherapy

Recent years have witnessed increasingly rapid advances in nanocarrier-based biomedicine aimed at improving treatment paradigms for cancer. Nanogels serve as multipurpose and constructed vectors formed via intramolecular cross-linking to generate drug delivery systems, which is attributed predominantly to their satisfactory biocompatibility, bio-responsiveness, high stability, and low toxicity. Recently, immunotherapy has experienced unprecedented growth and has become the preferred strategy for cancer treatment, and mainly involves the mobilisation of the immune system and an enhanced anti-tumour immunity of the tumour microenvironment. Despite the inspiring success, immunotherapeutic strategies are limited due to the low response rates and immune-related adverse events. Like other nanomedicines, nanogels are comparably limited by lower focal enrichment rates upon introduction into the organism via injection. Because nanogels are three-dimensional cross-linked aqueous materials that exhibit similar properties to natural tissues and are structurally stable, they can comfortably cope with shear forces and serum proteins in the bloodstream, and the longer circulation life increases the chance of nanogel accumulation in the tumour, conferring deep tumour penetration. The large specific surface area can reduce or eliminate off-target effects by introducing stimuli-responsive functional groups, allowing multiple physical and chemical modifications for specific purposes to improve targeting to specific immune cell subpopulations or immune organs, increasing the bioavailability of the drug, and conferring a low immune-related adverse events on nanogel therapies. The slow release upon reaching the tumour site facilitates long-term awakening of the host's immune system, ultimately achieving enhanced therapeutic effects. As an effective candidate for cancer immunotherapy, nanogel-based immunotherapy has been widely used. In this review, we mainly summarize the recent advances of nanogel-based immunotherapy to deliver immunomodulatory small molecule drugs, antibodies, genes and cytokines, to target antigen presenting cells, form cancer vaccines, and enable chimeric antigen receptor (CAR)-T cell therapy. Future challenges as well as expected and feasible prospects for clinical treatment are also highlighted.

End Group Dye-labeled Polycarbonate Block Copolymers for Micellar (immuno-)Drug Delivery

Defined conjugation of functional molecules to block copolymer end groups is a powerful strategy to enhance the scope of micellar carriers for drug delivery. In this study, we have established an approach to access well-defined polycarbonate-based block copolymers by labeling their end groups with single fluorescent dye molecules. Following controlled polymerization conditions, the block copolymers' primary hydroxy end group can be converted into activated pentafluorophenyl ester carbonates and subsequently aminolyzed with fluorescent dyes that are equipped with primary amines. During a solvent evaporation process, the resulting end group dye-labeled block copolymers self-assemble into narrowly dispersed 26 nm sized micelles and simultaneously encapsulate hydrophobic (immuno-)drugs. The covalently attached fluorescent tracer can be used to monitor both uptake into cells and stability under biologically relevant conditions, including incubation with blood plasma or during blood circulation in zebrafish embryos. By encapsulation of the TLR7/8 agonist CL075, immune stimulatory polymeric micelles are generated that get internalized by various antigen presenting dendritic cells and promote their maturation. Generally, such end group dye-labeled polycarbonate block copolymers display ideal features to permit targeted delivery of hydrophobic drugs to key immune cells for vaccination and cancer immunotherapy. This article is protected by copyright. All rights reserved.