Oncolytic bacteria can trigger innate immune activity. However, the antitumour efficacy of inactivated bacteria is poor, and attenuated live bacteria pose substantial safety risks. Here we show that intratumourally injected paraformaldehyde-fixed bacteria coated with manganese dioxide potently activate innate immune activity, modulate the immunosuppressive tumour microenvironment and trigger tumour-specific immune responses and abscopal antitumour responses. A single intratumoural administration of mineralized Salmonella typhimurium suppressed the growth of multiple types of subcutaneous and orthotopic tumours in mice, rabbits and tree shrews and protected the cured animals against tumour rechallenge. We also show that mineralized bacteria can be administered via arterial embolization to treat orthotopic liver cancer in rabbits. Our findings support the further translational testing of oncolytic mineralized bacteria as potent and safe antitumour immunotherapeutics.

By coating manganese dioxide on the surface of fixed bacteria, we obtained mineralized bacteria with the ability to potently activate multiple immune signalling pathways. Immunotherapy with mineralized bacteria suppressed various types of cancer in multiple animal models, eliciting both immune memory and abscopal antitumour effects.

Aluminum adjuvants remain the most commonly used vaccine adjuvants. Being rather effective in triggering humoral immunity, however, aluminum adjuvants usually show limited abilities in activating cellular immunities. Herein, by adding manganese ions during the preparation of aluminum adjuvant, a manganese-modified aluminum (Mn-Al) adjuvant is obtained, which can effectively stimulate both humoral and cellular immune responses. Such Mn-Al adjuvant can enhance antigen adsorption and promote antigen internalization by dendritic cells (DCs). Subsequently, the released Mn2+ can activate the cyclic guanosine monophosphate-adenosine monophosphate synthase-stimulator of interferon genes pathway to further promote DC activation. When combines with the model antigen ovalbumin (OVA), the Mn-Al-adjuvantes vaccine can induce high levels of antigen-specific antibody titers and high proportions of antigen-specific cytotoxic T cells in vivo. Moreover, the Mn-Al-adjuvanted vaccine elicited stronger antigen-specific humoral and cellular immune responses than high-dose of the aluminum-based adjuvant. Additionally, immunization of mice with OVA in the presence of the Mn-Al adjuvant significantly inhibited the growth of B16-OVA tumors. Furthermore, when formulated with human papillomavirus antigens, Mn-Al-adjuvanted vaccines show better in vivo vaccination performance than aluminum-adjuvanted vaccines. Therefore, the manganese-modified aluminum adjuvant may thus become a new vaccine adjuvant with the potential to replace conventional aluminum adjuvants.

Interleukin 2 (IL2) is the first approved immunotherapeutic agent in cancer treatment. However, high-dose IL2 administrated through intratumoral injection still spreads all over the body, causing serious systemic toxicity. Herein, an injectable nickel-alginate hydrogel microsphere (Ni-ALGMS) to allow effective loading of IL2 and its sustained release after intratumoral administration is reported. In this design, histidine (his)-tagged IL2 is assembled into the Ni-ALGMS via the coordination bonds between his-tag and Ni2+. After injecting IL2-loaded Ni-ALGMSs (IL2@Ni-ALGMSs) into the tumor, IL2 slowly releases over long periods, thereby avoiding the risk of cytokine storm happening in IL2 systemic administration. Applying such IL2@Ni-ALGMSs for tumor model treatment can significantly increase the tumor infiltration of T lymphocytes, and effectively inhibit tumor growth, especially in combination with immune checkpoint inhibitors. This study presents a novel IL2 sustained-releasing platform for tumor immunotherapy, which can also be conveniently applied in other cytokines-based immunotherapies.

BACKGROUND AIMS:Adoptive cell therapy (ACT) with tumor-infiltrating lymphocytes (TILs) has shown great success in clinical trials. Programmed cell death 1 (PD-1)-expressing TILs show high specificity to autologous tumor cells. However, limited therapeutic efficiency is observed as a result of the tumor immune microenvironment (TIME). METHODS:Coupling PD-1+ex vivo-derived TILs with a monoclonal antibody against anti-PD-1 (aPD-1) reinvigorated the anti-tumor response of TILs against solid tumor without altering their high tumor targeting ability. RESULTS:Using a melanoma-bearing mouse model, PD-1+ TILs blocked with aPD-1 (PD-1+ TILs-aPD-1) exhibited a high capability for tumor targeting as well as improved anti-tumor response in TIME. Tumor growth was substantially delayed in the mice treated with PD-1+ TILs-aPD-1. CONCLUSIONS:The strategy utilizing TIL therapy coupled with immune checkpoint antibodies may extend to other therapeutic targets of ACT.

The emergence of drug-resistant bacteria and easy recurrence has been challenging in the clinical treatment of skin abscesses resulting from bacterial infections (e.g., by Staphylococcus aureus (S. aureus)). Herein, an antibacterial nanoagent capable of modulating the abscess microenvironment is designed to enhance photodynamic treatment of skin abscesses, and subsequently activate the immune system to effectively prevent abscess recurrence. In the system, manganese dioxide nanoparticles (MnO2 NPs) with high catalytic reactivity toward H2 O2 are modified with photosensitizer chlorine e6 (Ce6) and coated with polyethylene glycol (PEG). The obtained Ce6@MnO2 -PEG NPs, by triggering the decomposition of lesion endogenous H2 O2 , are able to effectively relieve the hypoxic abscess microenvironment during S. aureus infection. The light-triggered photodynamic bacterial killing effect could thus be remarkably enhanced, resulting in effective in vivo therapy of S. aureus-induced skin abscesses. Interestingly, a notable pathogen-specific immunological memory effect against future infection by the same species of bacteria is elicited after such treatment, owing to the release of bacterial antigens post photodynamic therapy (PDT) together with the adjuvant-like function of manganese ions to activate the host immune system. This work thus presents a new type of photodynamic nanoagent particularly promising for highly effective light-triggered abscess treatment and prevention of abscess recurrence.

The spread of antibiotic-resistance poses a great threat, making it a growing need to develop other antibacterial strategies and therapeutics. Recently, owing to their excellent physicochemical properties, copper chalcogenides have received extensive attention as photothermal agents. However, most reports are focused on Cu2-xS nanoparticles, whereas very few water-dispersible Cu2-xSe nanomaterials have been reported due to their difficult preparation process. Herein, water-dispersible and biocompatible cuprous selenide nanosheets (Cu2Se NSs) were synthesized by a simple anion exchange method starting from cuprous oxide nanorods (Cu2O NRs), which could also help avoid any environmental pollution caused by the organic solvent used during synthesis. The obtained Cu2Se NSs showed strong absorption in the second near-infrared window (NIR II) with a good photothermal conversion efficiency as high as ∼61.16%, outstanding among the previously reported NIR II photothermal agents. Interestingly, using Staphylococcus aureus and Escherichia coli as model pathogens, these Cu2Se NSs possess an intrinsic bacteriostatic effect and could inhibit the growth of both bacteria species. Furthermore, both the fluorescent-based microscopy and the bacterial morphology analysis using a scanning electron microscope have demonstrated that incubation of both species of bacteria with Cu2Se NSs under laser irradiation (1064 nm) would lead to complete disruption of the bacterial cell wall. Our work presents a facile method to prepare water-dispersible Cu2Se NSs-, which could serve as highly efficient dual-functional antibacterial agents.

Cancer metastases and recurrence after surgical resection remain an important cause of treatment failure. Here we demonstrate a general strategy to fabricate personalized nanovaccines based on a cationic fluoropolymer for post-surgical cancer immunotherapy. Nanoparticles formed by mixing the fluoropolymer with a model antigen ovalbumin, induce dendritic cell maturation via the Toll-like receptor 4 (TLR4)-mediated signalling pathway, and promote antigen transportation into the cytosol of dendritic cells, which leads to an effective antigen cross-presentation. Such a nanovaccine inhibits established ovalbumin-expressing B16-OVA melanoma. More importantly, a mix of the fluoropolymer with cell membranes from resected autologous primary tumours synergizes with checkpoint blockade therapy to inhibit post-surgical tumour recurrence and metastases in two subcutaneous tumour models and an orthotopic breast cancer tumour. Furthermore, in the orthotopic tumour model, we observed a strong immune memory against tumour rechallenge. Our work offers a simple and general strategy for the preparation of personalized cancer vaccines to prevent post-operative cancer recurrence and metastasis.

The development of effective cancer vaccines is an important direction in the area of cancer immunotherapy. Although certain types of preventive cancer vaccines have already been used in the clinic, therapeutic cancer vaccines for treatment of already established tumors are still in high demand. In this study, we develop a new type of cancer vaccine by mixing cell-penetrating peptide (CPP) conjugated antigen as the enhanced antigen, together with CpG as the immune adjuvant. A special CPP, cytosol-localizing internalization peptide 6 (CLIP6), which has the ability to enter cells exclusively via a nonendosomal mechanism, i.e., direct translocation across the cell membrane, is conjugated with model antigen ovalbumin (OVA). Compared to naked OVA, the obtained CLIP6-OVA conjugates show greatly increased uptake by dendritic cells (DCs) and, more importantly, remarkably enhanced antigen cross-presentation, eliciting stronger cytotoxic T lymphocyte (CTL) mediated immune responses with the help of CpG. This CLIP6-OVA/CpG formulation offers effective protection for mice against challenged B16-OVA tumors, and is able to further function as a therapeutic vaccine, which, in combination with immune checkpoint blockade therapy, can significantly suppress the already-established tumors. Such a CLIP6-based cancer vaccine developing strategy shows promising potential toward clinical practice owing to its features of easy preparation, low cost, and remarkable biocompatibility.

Cancer vaccines for prevention and treatment of tumors have attracted tremendous interests as a type of cancer immunotherapy strategy. A major challenge in achieving robust T-cell responses to destruct tumor cells after vaccination is the abilities of antigen cross-presentation for antigen-presenting cells (APCs) such as dendritic cells (DCs). Herein, we demonstrate that a polyamidoamine dendrimer modified with guanidinobenzoic acid (DGBA) could serve as an effective protein carrier to enable delivery of protein antigen, thereby leading to effective antigen cross-presentation by DCs. With ovalbumin (OVA) as the model antigen and unmethylated cytosine-guanine dinucleotides (CpG) as the adjuvant, a unique type of tumor vaccine is formulated. Importantly, such DGBA-OVA-CpG nanovaccine can induce robust antigen-specific cellular immunities and further demonstrates outstanding prophylactic efficacy against B16-OVA melanoma. More significantly, the nanovaccine shows excellent therapeutic effect to treat established B16-OVA melanoma when used in combination with the programmed cell death protein 1 (PD-1) checkpoint-blockade immunotherapy. This study presents the great promises of employing rationally engineered cytosolic protein carriers for the development of tumor vaccines to achieve effective cancer immunotherapy.

While immunotherapy has become a highly promising paradigm for cancer treatment in recent years, it has long been recognized that photodynamic therapy (PDT) has the ability to trigger antitumor immune responses. However, conventional PDT triggered by visible light has limited penetration depth, and its generated immune responses may not be robust enough to eliminate tumors. Herein, upconversion nanoparticles (UCNPs) are simultaneously loaded with chlorin e6 (Ce6), a photosensitizer, and imiquimod (R837), a Toll-like-receptor-7 agonist. The obtained multitasking UCNP-Ce6-R837 nanoparticles under near-infrared (NIR) irradiation with enhanced tissue penetration depth would enable effective photodynamic destruction of tumors to generate a pool of tumor-associated antigens, which in the presence of those R837-containing nanoparticles as the adjuvant are able to promote strong antitumor immune responses. More significantly, PDT with UCNP-Ce6-R837 in combination with the cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) checkpoint blockade not only shows excellent efficacy in eliminating tumors exposed to the NIR laser but also results in strong antitumor immunities to inhibit the growth of distant tumors left behind after PDT treatment. Furthermore, such a cancer immunotherapy strategy has a long-term immune memory function to protect treated mice from tumor cell rechallenge. This work presents an immune-stimulating UCNP-based PDT strategy in combination with CTLA-4 checkpoint blockade to effectively destroy primary tumors under light exposure, inhibit distant tumors that can hardly be reached by light, and prevent tumor reoccurrence via the immune memory effect.