Engineering lentiviral vectors for modulation of dendritic cell apoptotic pathways

The potential of mRNA vaccines in cancer nanomedicine and immunotherapy

Owing to their outstanding performance against COVID-19, mRNA vaccines have brought great hope for combating various incurable diseases, including cancer. Differences in the encoded proteins result in different molecular and cellular mechanisms of mRNA vaccines. With the rapid development of nanotechnology and molecular medicine, personalized antigen-encoding mRNA vaccines that enhance antigen presentation can trigger effective immune responses and prevent off-target toxicities. Herein, we review new insights into the influence of encoded antigens, cytokines, and other functional proteins on the mechanisms of mRNA vaccines. We also highlight the importance of delivery systems and chemical modifications for mRNA translation efficiency, stability, and targeting, and we discuss the potential problems and application prospects of mRNA vaccines as versatile tools for combating cancer.

Anti-hepatoma Effect of DC2.4 Cells Transfected with Tumor-Associated Antigen Cdc25C In Vitro

OBJECTIVE

Cell division cyclin 25 homolog C (Cdc25C) is a tumor-associated antigen candidate gene, and this may be used as an effective target in cancer treatment. The present study aims to evaluate the lysis effect of cytotoxic T lymphocytes (CTLs) induced by dendritic cell line DC2.4 overexpressing Cdc25C, and the feasibility of Cdc25C as a component in hepatoma immunotherapy.

METHODS

The mouse Cdc25C gene was ligated into a lentiviral vector, and transfected into DC2.4 cells. The DC2.4 cell phenotype and cytokine secretion were determined by flow cytometry and ELISA, respectively. CD8⁺ T cells were sorted from the spleens of C57BL/6 mice using a magnetic bead sorting kit obtained from Miltenyi Biotech, Germany, and co-cultured with DC2.4 cells for one week as effector cells. Then, IL-2, granzyme B and perforin were detected in the CTL culture medium by ELISA. Next, time-resolved fluorescence immunoassay was used to detect the immune killing effect of Cdc25C-specific CTLs on target cells. Meanwhile, the effect of blocking MHC-I sites on target cells with a monoclonal anti-MHC-I antibody was evaluated.

RESULTS

The results revealed that Cdc25C could be stably overexpressed in DC2.4 cells by LV-Cdc25C infection. DC2.4 cells transfected with LV-Cdc25C secreted more IL-6, IL-12, TNF-α and IFN-γ, and had higher expression levels of CD40, CD86, CCR7 and MHC-II than unaltered DC2.4 cells. The elevated Cdc25C in dendritic cells also further increased the secretion of IL-2, granzyme B and perforin to elicit Cdc25C-specific CTLs, and induced the higher cytotoxicity in Hepa1-6 cell lines (P<0.05), but this had no effect on the target cells when MHC-I monoclonal antibodies were blocked.

CONCLUSION

DC2.4 cells transfected with LV-Cdc25C can induce specific CTLs, and result in a strong cellular immune response. The dendritic cells that overexpress Cdc25C may be useful for hepatoma immunotherapy.

Cancer vaccines as a targeted immunotherapy approach for breast cancer: an update of clinical evidence

INTRODUCTION

Breast cancer (BC) is the first common neoplastic malignancy and the second leading cause of death in women worldwide. Conventional treatments for BC are often associated with severe side effects and may even lead to late recurrence. For this reason, in recent years, cancer immunotherapy (e.g., cancer vaccines), a novel approach based on the specificity and amplification of acquired immune responses, has been considered as a potential candidate in particular to treat metastatic BC.

AREAS COVERED

In this review, we summarize and discuss the recent development of therapeutic vaccines for BC, use of specific BC cellular antigens, antigen selection, and probable causes for their insufficient effectiveness.

EXPERT OPINION

Despite development of several different BC vaccines strategies including protein/peptide, dendritic cell, and genetic vaccines, until now, no BC vaccine has been approved for clinical use. Most of the current BC vaccines themselves fail to bring clinical benefit to BC patients and are applied in combination with radiotherapy, chemotherapy, or targeted therapy. It is hoped that with advances in our knowledge about tumor microenvironment and the development of novel combination strategies, the tumor immunosuppressive mechanisms can be overcome and prolonged immunologic and effective anti-tumor response can be developed in patients.

Evaluation of transduced dendritic cells expressing HIV-1 p24-Nef antigens in HIV-specific cytotoxic T cells induction as a therapeutic candidate vaccine

Various approaches have been investigated to prevent or eliminate HIV-1 since 1981. However, the virus has been affecting human population worldwide with no effective vaccine yet. The conserved regions among the viral genes are suitable targets in mutable viruses to induce the immune responses via an effective delivery platform. In this study, we aimed at evaluation of p24 and nef in two forms of full and truncated genes as two fusion antigenic forms according to our previous bioinformatics analysis. The designed antigens were then transferred through ex vivo generated dendritic cells and also proteins in BALB/c to assess and compare immunogenicity. p24 and Nef amino acid sequences were aligned, then, the most conserved regions were selected and two fusion forms as the truncated (p24:80-231aa-Nef:120-150aa) and the full from (p24-Nef) were cloned and expressed in prokaryotic and eukaryotic systems. Lentiviral vectors were applied to generate recombinant virions harboring the genes of interest to transduce generated murine dendritic cells. BALB/c mice received the recombinant DCs or recombinant proteins according to the defined schedule. IgG development was assessed to determine humoral immune activity and cellular immune responses were evaluated by IL-5 and IFN-y induction. Granzyme B secretion was also investigated to determine CTL activity in different immunized groups. The data showed high induction of cellular immune responses in dendritic cell immunization specifically in immunized mice with the truncated form of the p24 and Nef by high secretion of IFN-y and strong CTL activity. Moreover, protein/ DC prime-boost formulation led to stronger Th1 pathway and strong CTL activation in comparison with other formulations. The generated recombinant dendritic cells expressing p24-Nef induced humoral and cellular immunity in a Th1 pathway specifically with the in silico predicted truncated antigen which could be of high value as a dendritic cell therapeutic vaccine candidate against HIV-1.

Engineering Hematopoietic Cells for Cancer Immunotherapy: Strategies to Address Safety and Toxicity Concerns

Advances in cancer immunotherapies utilizing engineered hematopoietic cells have recently generated significant clinical successes. Of great promise are immunotherapies based on chimeric antigen receptor-engineered T (CAR-T) cells that are targeted toward malignant cells expressing defined tumor-associated antigens. CAR-T cells harness the effector function of the adaptive arm of the immune system and redirect it against cancer cells, overcoming the major challenges of immunotherapy, such as breaking tolerance to self-antigens and beating cancer immune system-evasion mechanisms. In early clinical trials, CAR-T cell-based therapies achieved complete and durable responses in a significant proportion of patients. Despite clinical successes and given the side effect profiles of immunotherapies based on engineered cells, potential concerns with the safety and toxicity of various therapeutic modalities remain. We discuss the concerns associated with the safety and stability of the gene delivery vehicles for cell engineering and with toxicities due to off-target and on-target, off-tumor effector functions of the engineered cells. We then overview the various strategies aimed at improving the safety of and resolving toxicities associated with cell-based immunotherapies. Integrating failsafe switches based on different suicide gene therapy systems into engineered cells engenders promising strategies toward ensuring the safety of cancer immunotherapies in the clinic.

Lentivector Iterations and Pre-Clinical Scale-Up/Toxicity Testing: Targeting Mobilized CD34+ Cells for Correction of Fabry Disease

Fabry disease is a rare lysosomal storage disorder (LSD). We designed multiple recombinant lentivirus vectors (LVs) and tested their ability to engineer expression of human α-galactosidase A (α-gal A) in transduced Fabry patient CD34⁺ hematopoietic cells. We further investigated the safety and efficacy of a clinically directed vector, LV/AGA, in both ex vivo cell culture studies and animal models. Fabry mice transplanted with LV/AGA-transduced hematopoietic cells demonstrated α-gal A activity increases and lipid reductions in multiple tissues at 6 months after transplantation. Next we found that LV/AGA-transduced Fabry patient CD34⁺ hematopoietic cells produced even higher levels of α-gal A activity than normal CD34⁺ hematopoietic cells. We successfully transduced Fabry patient CD34⁺ hematopoietic cells with “near-clinical grade” LV/AGA in small-scale cultures and then validated a clinically directed scale-up transduction process in a GMP-compliant cell processing facility. LV-transduced Fabry patient CD34⁺ hematopoietic cells were subsequently infused into NOD/SCID/Fabry (NSF) mice; α-gal A activity corrections and lipid reductions were observed in several tissues 12 weeks after the xenotransplantation. Additional toxicology studies employing NSF mice xenotransplanted with the therapeutic cell product demonstrated minimal untoward effects. These data supported our successful clinical trial application (CTA) to Health Canada and opening of a “first-in-the-world” gene therapy trial for Fabry disease.

Preclinical validation: LV/IL-12 transduction of patient leukemia cells for immunotherapy of AML

Interleukin-12 (IL-12) is a potent cytokine that may be harnessed to treat cancer. To date, nearly 100 IL-12-based clinical trials have been initiated worldwide. Yet systemic administration of IL-12 is toxic. Different strategies are being developed to reduce such toxicities by restricting IL-12 distribution. Our previous studies employed lentivector-mediated expression of murine IL-12 in tumor cells and demonstrated effective protection in both mouse leukemia and solid tumor challenge models. In this study, we carried out preclinical validation studies using a novel lentivector to engineer expression of human IL-12 in acute myeloid leukemia blast cells isolated from 21 patients. Acute myeloid leukemia cells were transduced with a bicistronic lentivector that encodes the human IL-12 cDNA as a fusion, as well as a LNGFR (ΔLNGFR)/mutant thymidylate kinase cassette as a marking and cell-fate control element. A range of 20-70% functional transduction efficiencies was achieved. Transduced acute myeloid leukemia cells produced bioactive IL-12 protein and displayed dose-dependent sensitivity to the prodrug 3'-azido-3'-deoxythymidine. In vitro immortalization assays using transduced mouse hematopoietic stem cells demonstrated minimal genotoxic risk from our IL-12 vector. Scale-up transduction and cell processing was subsequently validated in a GMP facility to support our (now approved) Clinical Trial Application (CTA).

Lentiviral vectors in cancer immunotherapy

Basic science advances in cancer immunotherapy have resulted in various treatments that have recently shown success in the clinic. Many of these therapies require the insertion of genes into cells to directly kill them or to redirect the host's cells to induce potent immune responses. Other analogous therapies work by modifying effector cells for improved targeting and enhanced killing of tumor cells. Initial studies done using γ-retroviruses were promising, but safety concerns centered on the potential for insertional mutagenesis have highlighted the desire to develop other options for gene delivery. Lentiviral vectors (LVs) have been identified as potentially more effective and safer alternative delivery vehicles. LVs are now in use in clinical trials for many different types of inherited and acquired disorders, including cancer. This review will discuss current knowledge of LVs and the applications of this viral vector-based delivery vehicle to cancer immunotherapy.