In Situ Tumor Vaccination with Calcium-Linked Degradable Coacervate Nanocomplex Co-Delivering Photosensitizer and TLR7/8 Agonist to Trigger Effective Anti-Tumor Immune Responses

Engineered mitochondria exert potent antitumor immunity as a cancer vaccine platform

The preferable antigen delivery profile accompanied by sufficient adjuvants favors vaccine efficiency. Mitochondria, which feature prokaryotic characteristics and contain various damage-associated molecular patterns (DAMPs), are easily taken up by phagocytes and simultaneously activate innate immunity. In the current study, we established a mitochondria engineering platform for generating antigen-enriched mitochondria as cancer vaccine. Ovalbumin (OVA) and tyrosinase-related protein 2 (TRP2) were used as model antigens to synthesize fusion proteins with mitochondria-localized signal peptides. The lentiviral infection system was then employed to produce mitochondrial vaccines containing either OVA or TRP2. Engineered OVA- and TRP2-containing mitochondria (OVA-MITO and TRP2-MITO) were extracted and evaluated as potential cancer vaccines. Impressively, the engineered mitochondria vaccine demonstrated efficient antitumor effects when used as both prophylactic and therapeutic vaccines in murine tumor models. Mechanistically, OVA-MITO and TRP2-MITO potently recruited and activated dendritic cells (DCs) and induced a tumor-specific cell-mediated immunity. Moreover, DC activation by mitochondria vaccine critically involves TLR2 pathway and its lipid agonist, namely, cardiolipin derived from the mitochondrial membrane. The results demonstrated that engineered mitochondria are natively well-orchestrated carriers full of immune stimulants for antigen delivery, which could preferably target local dendritic cells and exert strong adaptive cellular immunity. This proof-of-concept study established a universal platform for vaccine construction with engineered mitochondria bearing alterable antigens for cancers as well as other diseases.

Mannan-Decorated Lipid Calcium Phosphate Nanoparticle Vaccine Increased the Antitumor Immune Response by Modulating the Tumor Microenvironment

With the rapid development of tumor immunotherapy, nanoparticle vaccines have attracted much attention as potential therapeutic strategies. A systematic review and analysis must be carried out to investigate the effect of mannose modification on the immune response to nanoparticles in regulating the tumor microenvironment, as well as to explore its potential clinical application in tumor therapy. Despite the potential advantages of nanoparticle vaccines in immunotherapy, achieving an effective immune response in the tumor microenvironment remains a challenge. Tumor immune escape and the overexpression of immunosuppressive factors limit its clinical application. Therefore, our review explored how to intervene in the immunosuppressive mechanism in the tumor microenvironment through the use of mannan-decorated lipid calcium phosphate nanoparticle vaccines to improve the efficacy of immunotherapy in patients with tumors and to provide new ideas and strategies for the field of tumor therapy.

Nanoplatform-enhanced photodynamic therapy for the induction of immunogenic cell death

As an efficient, non-invasive, low-side-effect, and highly selective cancer therapy, photodynamic therapy (PDT) is used to treat various malignant tumors. However, the inefficiency of dealing with deep tumors and metastatic lesions highly limits the use of PDT. Immunogenic cell death (ICD) is a particular form of tumor cell death that could elicit a tumor-special immune response, leading to a systemic anti-tumor effect and providing therapeutic benefits for metastatic lesions. In this regard, it is crucial to enhance the ability of PDT to induce ICD. Luckily, advanced nanotechnology created many promising ways to improve the immunogenicity of PDT and achieve photoimmunotherapy. This review summarizes the emerging strategies for triggering immunogenic cell death via nanoplatform-enhanced PDT, with particular emphasis on their advantages in photoimmunotherapy. We highlight the nanoplatforms classified according to the basic principles of photodynamic therapy and immunogenic cell death, which provides a valuable reference for the design of nanoplatform for photoimmunotherapy. In addition, we also discuss the current situation and prospect of nano-based photoimmunotherapy in clinical studies.

"Closed-Loop" O2-Economizer Induced In Situ Therapeutic Vaccine against Hypoxic Tumors

Therapeutic tumor vaccines, which use tumor antigens to stimulate a cancer patient's immune system to eventually kill the tumor tissues, have emerged as one of the most attractive strategies in anticancer research. Especially, exploring in situ vaccines has become a potential field in cancer immunotherapy. However, due to the hypoxic tumor microenvironment, the generation of tumor antigens is always mild and not sufficient. Hence, in this study, we designed a closed-loop mitochondrial oxygen-economizer (TPCA) to induce enhanced phototherapy-driven in situ vaccines. The O2-economizer was developed by the integration of the photosensitizer CyI and the mitochondrial inhibitor atovaquone into the PAMAM dendrimer. In vitro and in vivo studies showed that TPCA could enter the mitochondria through (3-propylcarboxyl) triphenylphosphine bromide (TPP) and effectively restrict the respiration of tumor cells to reduce tumor hypoxia, thus providing continuous oxygen for enhanced iodinated cyanine dye mediated photodynamic therapy, which could further induce in situ vaccines for ablating the primary tumor directly and inhibiting the tumor metastasis and recurrence. Furthermore, the antitumor mechanism revealed that O2-economizer-based oxygen-boosted PDT elicited immunogenic cancer cell death with enhanced exposure and release of DAMPs and altered the immunosuppressive tumor microenvironment with increased recruitment of T cells in tumors, thereby inducing in situ vaccines and provoking the systematic antitumor responses against CT26 tumors. This study will provide innovative approaches for local, abscopal, and metastatic tumor treatment.

Vaccination of TLR7/8 Agonist-Conjugated Antigen Nanoparticles for Cancer Immunotherapy

Nanovaccine-based immunotherapy can initiate strong immune responses and establish a long-term immune memory to prevent tumor invasion and recurrence. Herein, the assembly of redox-responsive antigen nanoparticles (NPs) conjugated with imidazoquinoline-based TLR7/8 agonists for lymph node-targeted immune activation is reported, which can potentiate tumor therapy and prevention. Antigen NPs are assembled via the templating of zeolitic imidazolate framework-8 NPs to cross-link ovalbumin with disulfide bonds, which enables the NPs with redox-responsiveness for improved antigen cross-presentation and dendritic cell activation. The formulated nanovaccines promote the lymphatic co-delivery of antigens and agonists, which can trigger immune responses of cytotoxic T lymphocytes and strong immunological memory. Notably, nanovaccines demonstrate their superiority for tumor prevention owing to the elicited robust antitumor immunity. The reported strategy provides a rational design of nanovaccines for enhanced cancer immunotherapy.

Site-specific nanoswitch circumventing immune resistance via activating TLR and inhibiting PD-L1/PD-1 axis

Immunotherapy has fundamentally altered cancer treatment; however, its effectiveness is clinically hampered by insufficient intratumoral T lymphocyte infiltration and failed T lymphocyte priming. Additionally, inducing cancer-specific immune responses while sparing normal cells remains challenging. Herein, we developed a redox-activatable polymeric nanoswitch (c-N@IM/JQ) that remained 'off' status in circulation but rapidly switched 'on' after entering the tumor. Toll-like receptor (TLR) 7/8 agonist (imidazoquinoline, IMQ) and bromodomain and extraterminal inhibitor (JQ1) are locked in c-N@IM/JQ with a redox-cleavable linker (switch off). Upon systemic administration, c-N@IM/JQ with c-RGD peptide modification preferentially accumulated at tumor sites and responded to the high glutathione levels to release native IMQ for fully mobilizing T lymphocyte army, and JQ1 for removing the programmed death ligand (PD-L)-1 protection on tumor cells (switch on). These strengthened T lymphocyte armies are easily accessible to these de-protected tumor cells, revitalizing the immune response against tumors.

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.

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.

Multicompartment Nanoparticles by Crystallization-Driven Self-Assembly of Star Polymers: Combining High Stability and Loading Capacity

Herein novel multicompartment nanoparticles (MCNs) that combine high stability and cargo loading capacity are developed. The MCNs are fabricated by crystallization-driven self-assembly (CDSA) of a tailor-made 21 arm star polymer, poly(L-lactide)[poly(tert-butyl acrylate)-block-poly(ethylene glycol)]₂₀ [PLLA(PtBA-b-PEG)₂₀ ]. Platelet-like or spherical MCNs containing a crystalline PLLA core and hydrophobic PtBA subdomains are formed and stabilized by PEG. Hydrophobic cargos, such as Nile Red and chemotherapeutic drug doxorubicin, can be successfully encapsulated into the collapsed PtBA subdomains with loading capacity two orders of magnitude higher than traditional CDSA nanoparticles. Depolarized fluorescence measurements of the Nile Red loaded MCNs suggest that the free volume of the hydrophobic chains in the nanoparticles may be the key for regulating their drug loading capacity. In vitro study of the MCNs suggests excellent cytocompatibility of the blank nanoparticles as well as a dose-dependent cellular uptake and cytotoxicity of the drug-loaded MCNs.

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.

The Role of Toll-like Receptor Agonists and Their Nanomedicines for Tumor Immunotherapy

Toll-like receptors (TLRs) are a class of pattern recognition receptors that play a critical role in innate and adaptive immunity. Toll-like receptor agonists (TLRa) as vaccine adjuvant candidates have become one of the recent research hotspots in the cancer immunomodulatory field. Nevertheless, numerous current systemic deliveries of TLRa are inappropriate for clinical adoption due to their low efficiency and systemic adverse reactions. TLRa-loaded nanoparticles are capable of ameliorating the risk of immune-related toxicity and of strengthening tumor suppression and eradication. Herein, we first briefly depict the patterns of TLRa, followed by the mechanism of agonists at those targets. Second, we summarize the emerging applications of TLRa-loaded nanomedicines as state-of-the-art strategies to advance cancer immunotherapy. Additionally, we outline perspectives related to the development of nanomedicine-based TLRa combined with other therapeutic modalities for malignancies immunotherapy.