Dendritic Cells Cross-Present Immunogenic Lentivector-Encoded Antigen from Transduced Cells to Prime Functional T Cell Immunity

Systemic CD4 Immunity and PD-L1/PD-1 Blockade Immunotherapy

PD-L1/PD-1 blockade immunotherapy has changed the therapeutic approaches for the treatment of many cancers. Nevertheless, the mechanisms underlying its efficacy or treatment failure are still unclear. Proficient systemic immunity seems to be a prerequisite for efficacy, as recently shown in patients and in mouse models. It is widely accepted that expansion of anti-tumor CD8 T cell populations is principally responsible for anti-tumor responses. In contrast, the role of CD4 T cells has been less studied. Here we review and discuss the evidence supporting the contribution of CD4 T cells to anti-tumor immunity, especially recent advances linking CD4 T cell subsets to efficacious PD-L1/PD-1 blockade immunotherapy. We also discuss the role of CD4 T cell memory subsets present in peripheral blood before the start of immunotherapies, and their utility as predictors of response.

Intratumoral IL-12 delivery empowers CAR-T cell immunotherapy in a pre-clinical model of glioblastoma

Glioblastoma multiforme (GBM) is the most common and aggressive form of primary brain cancer, for which effective therapies are urgently needed. Chimeric antigen receptor (CAR)-based immunotherapy represents a promising therapeutic approach, but it is often impeded by highly immunosuppressive tumor microenvironments (TME). Here, in an immunocompetent, orthotopic GBM mouse model, we show that CAR-T cells targeting tumor-specific epidermal growth factor receptor variant III (EGFRvIII) alone fail to control fully established tumors but, when combined with a single, locally delivered dose of IL-12, achieve durable anti-tumor responses. IL-12 not only boosts cytotoxicity of CAR-T cells, but also reshapes the TME, driving increased infiltration of proinflammatory CD4+ T cells, decreased numbers of regulatory T cells (Treg), and activation of the myeloid compartment. Importantly, the immunotherapy-enabling benefits of IL-12 are achieved with minimal systemic effects. Our findings thus show that local delivery of IL-12 may be an effective adjuvant for CAR-T cell therapy for GBM.

Dual-Wavelength Photosensitive Nano-in-Micro Scaffold Regulates Innate and Adaptive Immune Responses for Osteogenesis

The immune response of a biomaterial determines its osteoinductive effect. Although the mechanisms by which some immune cells promote regeneration have been revealed, the biomaterial-induced immune response is a dynamic process involving multiple cells. Currently, it is challenging to accurately regulate the innate and adaptive immune responses to promote osteoinduction in biomaterials. Herein, we investigated the roles of macrophages and dendritic cells (DCs) during the osteoinduction of biphasic calcium phosphate (BCP) scaffolds. We found that osteoinductive BCP directed M2 macrophage polarization and inhibited DC maturation, resulting in low T cell response and efficient osteogenesis. Accordingly, a dual-targeting nano-in-micro scaffold (BCP loaded with gold nanocage, BCP-GNC) was designed to regulate the immune responses of macrophages and DCs. Through a dual-wavelength photosensitive switch, BCP-GNC releases interleukin-4 in the early stage of osteoinduction to target M2 macrophages and then releases dexamethasone in the later stage to target immature DCs, creating a desirable inflammatory environment for osteogenesis. This study demonstrates that biomaterials developed to have specific regulatory capacities for immune cells can be used to control the early inflammatory responses of implanted materials and induce osteogenesis.

ZVex™, a dendritic-cell-tropic lentivector, primes protective antitumor T cell responses that are significantly boosted using heterologous vaccine modalities

Therapeutic cancer vaccines must induce high levels of tumor-specific cytotoxic CD8 T cells to be effective. We show here that tumor-antigen specific effector and memory T cell responses primed with a non-integrating, dendritic-cell targeted lentiviral vector (ZVex™) could be boosted significantly by either adjuvanted recombinant protein, adenoviral vectors, or self-replicating RNA. These heterologous prime-boost regimens also provided significantly better protection in murine tumor models. In contrast, homologous prime-boost regimens, or using the lentiviral vector as a boost, resulted in lower T cell responses with limited therapeutic efficacy. Heterologous prime-boost regimens that utilize ZVex as the prime may be attractive modalities for therapeutic cancer vaccines.

Reprogramming the murine colon cancer microenvironment using lentivectors encoding shRNA against IL-10 as a component of a potent DC-based chemoimmunotherapy

Background

The excessive amounts of immunosuppressive factors present in a tumor microenvironment (TME) reduce the effectiveness of cancer vaccines. The main objective of our research was to improve the effectiveness of dendritic cell (DC)-based immunotherapy or chemoimmunotherapy composed of cyclophosphamide (CY) and DCs by application of lentivectors encoding shRNA specific to IL-10 (shIL10 LVs) in murine colon carcinoma MC38 model.

Methods

The efficacy of shIL10 LVs in silencing of IL-10 expression was measured both in vitro and in vivo using Real-Time PCR and ELISA assays. In addition, the influence of intratumorally inoculated lentivectors on MC38 tumor microenvironment was examined using flow cytometry method. The effect of applied therapeutic schemes was determined by measurement of tumor growth inhibition and activation state of local and systemic immune response.

Results

We observed that intratumorally inoculated shIL10 LVs transduced tumor and TME-infiltrating cells and reduced the secretion of IL-10. Application of shIL10 LVs for three consecutive weeks initiated tumor growth inhibition, whereas treatment with shIL10 LVs and BMDC/TAg did not enhance the antitumor effect. However, when pretreatment with CY was introduced to the proposed scheme, we noticed high MC38 tumor growth inhibition accompanied by reduction of MDSCs and Tregs in TME, as well as activation of potent local and systemic Th1-type antitumor response.

Conclusions

The obtained data shows that remodeling of TME by shIL10 LVs and CY enhances DC activity and supports them during regeneration and actuation of a potent antitumor response. Therefore, therapeutic strategies aimed at local IL-10 elimination using lentiviral vectors should be further investigated in context of combined chemoimmunotherapies.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0799-y) contains supplementary material, which is available to authorized users.

Tumor-Resident Dendritic Cells and Macrophages Modulate the Accumulation of TCR-Engineered T Cells in Melanoma

Ongoing clinical trials explore T cell receptor (TCR) gene therapy as a treatment option for cancer, but responses in solid tumors are hampered by the immunosuppressive microenvironment. The production of TCR gene-engineered T cells requires full T cell activation in vitro, and it is currently unknown whether in vivo interactions with conventional dendritic cells (cDCs) regulate the accumulation and function of engineered T cells in tumors. Using the B16 melanoma model and the inducible depletion of CD11c⁺ cells in CD11c.diphtheria toxin receptor (DTR) mice, we analyzed the interaction between tumor-resident cDCs and engineered T cells expressing the melanoma-specific TRP-2 TCR. We found that depletion of CD11c⁺ cells triggered the recruitment of cross-presenting cDC1 into the tumor and enhanced the accumulation of TCR-engineered T cells. We show that the recruited tumor cDCs present melanoma tumor antigen, leading to enhanced activation of TCR-engineered T cells. In addition, detailed analysis of the tumor myeloid compartment revealed that the depletion of a population of DT-sensitive macrophages can contribute to the accumulation of tumor-infiltrating T cells. Together, these data suggest that the relative frequency of tumor-resident cDCs and macrophages may impact the therapeutic efficacy of TCR gene therapy in solid tumors.

Intradermal Immunization with rAAV1 Vector Induces Robust Memory CD8+ T Cell Responses Independently of Transgene Expression in DCs

Recombinant adeno-associated viral (rAAV) vectors exhibit interesting properties as vaccine carriers for their ability to induce long-lasting antibody responses. However, rAAV-based vaccines have been suggested to trigger functionally impaired long-term memory CD8⁺ T cell responses, in part due to poor dendritic cell (DC) transduction. Such results, albeit limited to intramuscular immunization, undermined the use of rAAV as vaccine vehicles against intracellular pathogens. We report here that intradermal immunization with a model rAAV2/1-based vaccine drives the development of bona fide long-term memory CD8⁺ T cell responses. The intradermal route of immunization and the presence of potent major histocompatibility complex (MHC) class II responses showed synergistic effects on the overall quantity and quality of systemic long-term effector memory transgene-specific CD8⁺ T cells being generated against the transgene. Of key interest, we found that the induction of memory cytotoxic T lymphocytes (CTLs) following intradermal immunization was solely dependent on the cross-presentation of skin-expressed transgene products, which appeared highly enhanced as compared to muscle-expressed transgene products. Overall our results highlight key tissue-specific differences in transgene presentation pathway requirements of importance for the design of rAAV-based T cell-inducing vaccines.

Intratumoral Lentivector-Mediated TGF-β1 Gene Downregulation As a Potent Strategy for Enhancing the Antitumor Effect of Therapy Composed of Cyclophosphamide and Dendritic Cells

Vaccination with dendritic cells (DCs) stimulated with tumor antigens can induce specific cellular immune response that recognizes a high spectrum of tumor antigens. However, the ability of cancer cells to produce immunosuppressive factors drastically decreases the antitumor activity of DCs. The main purpose of the study was to improve the effectiveness of DC-based immunotherapy or chemoimmunotherapy composed of cyclophosphamide (CY) and DCs by application of lentivectors (LVs)-encoding short hairpin RNA specific for TGF-β1 (shTGFβ1 LVs). We observed that s.c. inoculation of both MC38 cells with silenced expression of TGF-β1 (MC38/shTGF-β1) and direct intratumoral application of shTGFβ1 LVs contributed to reduction of suppressor activity of myeloid cells and Tregs in tumor. Contrary to expectations, in mice bearing wild tumor, the application of shTGFβ1 LVs prior to vaccination with bone marrow-derived DC stimulated with tumor antigens (BMDC/TAg) did not influence myeloid-derived suppressor cell (MDSC) infiltration into tumor. As a result, we observed only minor MC38 tumor growth inhibition (TGI) accompanied by systemic antitumor response activation comparable to that obtained for negative control (shN). However, when the proposed scheme was complemented by pretreatment with a low dose of CY, we noticed high MC38 TGI together with decreased number of MDSCs in tumor and induction of Th1-type response. Moreover, in both schemes of treatment, LVs (shTGFβ1 as well as shN) induced high influx of CTLs into tumor associated probably with the viral antigen introduction into tumor microenvironment. Concluding, the application of shTGFβ1 LVs alone or in combination with DC-based vaccines is not sufficient for long-lasting elimination of suppression in tumor. However, simultaneous reduction of TGF-β1 in tumor microenvironment and its remodeling by pretreatment with a low dose of CY facilitates the settlement of peritumorally inoculated DCs and supports them in restoration and activation of a potent antitumor response.