Spontaneous Activation of Antigen-presenting Cells by Genes Encoding Truncated Homo-Oligomerizing Derivatives of CD40

Leonurine promotes the maturation of healthy donors and multiple myeloma patients derived-dendritic cells via the regulation on arachidonic acid metabolism

Objective: Leonurine is a bioactive alkaloid compound extracted from Leonurus japonicus Houtt, which potentially has immunomodulatory effects. The immunomodulatory effect and mechanism of leonurine on monocyte derived dendritic cells (moDCs) from healthy donors (HDs) and multiple myeloma (MM) patients were investigated for the first time. Methods: Peripheral blood from HDs and MM patients was isolated for peripheral blood mononuclear cells (PBMCs). The generation of moDCs was conducted by the incubation of monocytes from PBMCs in the medium consisting of RPMI 1640 medium, 2 mmol/L L-glutamine, 5% human serum, 800 U/mL GM-CSF, 500 U/mL IL-4, 100 U/mL penicillin and 0.1 mg/mL streptomycin. During the incubation of 7 days, the cells were administrated with 1 μM leonurine or 1 × PBS as the control group. On the 8th day, cells were harvested. The expression of maturation associated surface markers CD40, CD83, and HLA-DR on moDCs was analyzed by flow cytometry. Moreover, moDCs with or without 1 μM leonurine administration were evaluated by LC-MS/MS for metabolomics which was further analyzed for the potential mechanism of leonurine on moDCs. Results: The proportion of moDCs in the harvested cells was significantly higher in the HD group (n = 14) than in the MM patient group (n = 11) (p = 0.000). Leonurine significantly enhanced the median fluorescence intensity of CD83, HLA-DR and CD40 expression on HD-moDCs (n = 14; p = 0.042, p = 0.013, p = 0.084) as well as MM paitent-moDCs (n = 11; p = 0.020, p = 0.006, p = 0.025). The metabolomics data showed that in moDCs (HD, n = 15), 18 metabolites in the pathway of arachidonic acid metabolism showed significant differences between the leonurine group and the control group (VIP all >1 and P all <0.05). To be specific, 6-Keto-PGE1, 8,9-DHET, 11 (R)-HETE, 12-Keto-LTB4, 12-OxoETE, 15 (S)-HETE, 15-Deoxy-Delta12,14-PGJ2, 15-Keto-PGF2a, 20-COOH-LTB4, Lecithin, PGA2, PGB2, PGE2, PGF2a, PGG2, Prostacyclin were significantly upregulated in the leonurine group than in the control group, while Arachidonic Acid and TXB2 were significantly downregulated in the leonurine group than in the control group. Conclusion: Leonurine significantly promotes the maturation of moDCs derived from HDs and MM patients, the mechanism of which is related to arachidonic acid metabolism.

Membrane anchored IL-18 linked to constitutively active TLR4 and CD40 improves human T cell antitumor capacities for adoptive cell therapy

Background

Adoptive transfer of tumor-infiltrating lymphocytes (TILs) or blood T cells genetically redirected by an antitumor TCR or CAR induces a strong antitumor response in a proportion of patients with cancer; however, the therapeutic efficacy is often limited by rapid decline in T cell functions. Coadministering supportive cytokines frequently provokes systemic side effects preventing their broad clinical application. We recently showed that cytokines can be anchored to the cell membrane in a functional fashion and that cytokine receptor signaling can synergize with TLR4 and CD40 signaling. Here, we aimed at augmenting T cell activation by simultaneous signaling through the cytokine receptor, toll-like receptor and TNF-type receptor using IL-18, TLR4 and CD40 as prototypes.

Methods

Genes were expressed on electroporation of in vitro-transcribed mRNA in CD4+ and CD8+ T cells from healthy donors redirected against melanoma cells with an anti-melanotransferrin CAR and in TILs derived from melanoma patients. Functional assays included the activation of signaling pathways, expression of activation and differentiation markers, cytokine secretion and killing of melanoma target cells.

Results

To provide IL-18 costimulation to T cells in-cis while avoiding systemic effects, we genetically anchored IL-18 to the T cell membrane, either alone (memIL-18) or fused with constitutively active (ca)TLR4 and caCD40 signaling domains arranged in tandem, creating a synthetic ‘all-in-one’ memIL-18-TLR4-CD40 receptor. MemIL-18-TLR4-CD40, but not memIL-18, triggered strong NF-κB activation in cells lacking the IL-18 receptor, attesting to functionality of the TLR-CD40 moiety. While the membrane-anchored cytokine was found to act mainly in-cis, some T cell activation in-trans was also observed. The electroporated T cells exhibited spontaneous T-bet upregulation and IFN-γ and TNF-α secretion. Melanoma-induced activation of CAR-T cells and TILs as manifested by cytokine secretion and cytolytic activity was substantially augmented by both constructs, with memIL-18-TLR4-CD40 exerting stronger effects than memIL-18 alone.

Conclusions

Linking membrane anchored IL-18 with caTLR4 and caCD40 signaling in one hybrid transmembrane protein provides simultaneous activation of three T cell costimulatory pathways through one genetically engineered membrane molecule, strongly amplifying T cell functions for adoptive T cell therapy of cancer.

mRNA-based therapies: Preclinical and clinical applications

At the fundamental level, messenger RNA (mRNA)-based therapeutics involves the delivery of in vitro-transcribed (IVT) mRNA into the cytoplasm of a target cell, where it is translated into the desired protein. IVT mRNA presents various advantages compared to DNA and recombinant protein-based approaches that make it ideal for a broad range of therapeutic applications. IVT mRNA, which is translated in the cytoplasm after transfection into cells, can encode virtually any target protein. Notably, it does not enter the nucleus, which avoids its integration into the genome and the risk of insertional mutagenesis. The large-scale production of IVT mRNA is less complex than production of recombinant proteins, and Good Manufacturing Practice-compliant mRNA production is easily scalable, ideally poising mRNA for not only off-the-shelf, but more personalized treatment approaches. IVT mRNA's safety profile, pharmacokinetics, and pharmacodynamics, including its inherent immunostimulatory capacity, can be optimized for different therapeutic applications by harnessing a wide array of optimized sequence elements, chemical modifications, purification techniques, and delivery methods. The value of IVT mRNA was recently proved during the COVID-19 pandemic when mRNA-based vaccines outperformed the efficacy of established technologies, and millions of doses were rapidly deployed. In this review, we will discuss chemical modifications of IVT mRNA and highlight numerous preclinical and clinical applications including vaccines for cancer and infectious diseases, cancer immunotherapy, protein replacement, gene editing, and cell reprogramming.

The Intracellular Domain of CD40 is a Potent Costimulatory Element in Chimeric Antigen Receptors

The costimulatory domains incorporated into second-generation and third-generation chimeric antigen receptors (CARs) strongly influence CAR-T-cell function. Here, we explored second-generation and third-generation CARs harboring the signaling domain of the CD40 receptor as a new costimulatory element in comparison with similar CARs carrying the 4-1BB domain. In CARs of both generations, CD40 was more potent than 4-1BB in triggering the NF-κB signaling pathway. In human T cells from 2 donors, CD40 was comparable to 4-1BB in upregulating costimulatory and activation markers, inducing proinflammatory cytokine secretion and mediating target cell killing. Interestingly, differences in the response pattern of T cells from the 2 donors with respect to CD40 and 4-1BB were evident. We conclude that in human T cells, the CD40 signaling domain is a potent costimulatory element in both second-generation and third-generation CARs.

mRNA therapeutics in cancer immunotherapy

Synthetic mRNA provides a template for the synthesis of any given protein, protein fragment or peptide and lends itself to a broad range of pharmaceutical applications, including different modalities of cancer immunotherapy. With the ease of rapid, large scale Good Manufacturing Practice-grade mRNA production, mRNA is ideally poised not only for off-the shelf cancer vaccines but also for personalized neoantigen vaccination. The ability to stimulate pattern recognition receptors and thus an anti-viral type of innate immune response equips mRNA-based vaccines with inherent adjuvanticity. Nucleoside modification and elimination of double-stranded RNA can reduce the immunomodulatory activity of mRNA and increase and prolong protein production. In combination with nanoparticle-based formulations that increase transfection efficiency and facilitate lymphatic system targeting, nucleoside-modified mRNA enables efficient delivery of cytokines, costimulatory receptors, or therapeutic antibodies. Steady but transient production of the encoded bioactive molecule from the mRNA template can improve the pharmacokinetic, pharmacodynamic and safety properties as compared to the respective recombinant proteins. This may be harnessed for applications that benefit from a higher level of expression control, such as chimeric antigen receptor (CAR)-modified adoptive T-cell therapies. This review highlights the advancements in the field of mRNA-based cancer therapeutics, providing insights into key preclinical developments and the evolving clinical landscape.

Genetic Modification of Tumor-Infiltrating Lymphocytes via Retroviral Transduction

Adoptive T cell therapy (ACT) holds great promise for cancer treatment. One approach, which has regained wide interest in recent years, employs antitumor T cells isolated from tumor lesions ("tumor-infiltrating lymphocytes" or TIL). It is now appreciated that a considerable proportion of anti-melanoma TIL recognize new HLA-binding peptides resulting from somatic mutations, which occurred during tumor progression. The clinical efficacy of TIL can potentially be improved via their genetic modification, designed to enhance their survival, homing capacity, resistance to suppression, tumor killing ability and additional properties of clinical relevance. Successful implementation of such gene-based strategies critically depends on efficient and reproducible protocols for gene delivery into clinical TIL preparations. Here we describe an optimized protocol for the retroviral transduction of TIL. As the experimental system we employed anti-melanoma TIL cultures prepared from four patients, recombinant retrovirus encoding an anti-CD19 chimeric antigen receptor (CAR) as a model gene of interest and CD19+ and CD19- human cell lines serving as target cells. Transduction on day 7 of the rapid expansion protocol (REP) resulted in 69 ± 8% CAR positive TIL. Transduced, but not untransduced TIL, from the four patients responded robustly to CD19+, but not CD19- cell lines, as judged by substantial secretion of IFN-γ following co-culture. In light of the rekindled interest in antitumor TIL, this protocol can be incorporated into a broad range of gene-based approaches for improving the in-vivo survival and functionality of TIL in the clinical setting.

Endowing human CD8 T cells with a veto-like recognition capacity via the electroporation of MHC-I/CD3ζ mRNA

Graft-versus-host disease (GVHD) and transplant rejection as a result of host-versus-graft (HVG) response have remained two major complications of allogeneic hematopoietic stem cell transplantation (allo-HSCT). When donors are partially HLA-mismatched unrelated or haploidentical related, their severity correlates with the degree of HLA disparity. Specific elimination of alloreactive donor or recipient T cells targeting the mismatched HLA products could markedly alleviate both complications while only minimally affecting graft-versus-tumor (GVT) response or engraftment. To redirect human CD8 T cells against alloreactive CD8 T cells we electroporate these cells with in-vitro-transcribed mRNA encoding MHC-I heavy chains fused with the signaling portion of CD3ζ. Here we show that peripheral blood human CD8 T cells expressing H-2K^b/CD3ζ or H-2K^d/CD3ζ respond to anti-MHC-I stimuli in a strictly specific manner. This study paves the way for further advancing this approach as a means to dampen GVHD and HVG that are caused by HLA disparity in allo-HSCT.

Potent Activation of Human T Cells by mRNA Encoding Constitutively Active CD40

New strategies for augmenting the actual performance of therapeutic T cells in vivo are needed for improving clinical outcome of adoptive cell therapy. Cumulative findings suggest that CD40 plays an intrinsic role in T cell costimulation. Recently, we demonstrated the ability of truncated, auto-oligomerizing CD40 derivatives to induce strong activation of APCs in a ligand-independent manner. We reasoned that constitutively active CD40 (caCD40) can similarly exert enhancing effects on human antitumor T cells. To test this assumption, we transfected human T cells with in vitro-transcribed caCD40 mRNA. In polyclonal T cells, caCD40 triggered IFN-γ secretion and upregulated CD25 and 4-1BB. In antimelanoma tumor-infiltrating lymphocytes (TILs), caCD40 induced massive production of IFN-γ, exerting a pronounced synergistic effect when coexpressed with constitutively active TLR4 devoid of its extracellular ligand binding. In unselected "young" TILs, caCD40 reproducibly increased surface expression of CD25, OX40, 4-1BB, CD127, and CD28. Three days post-mRNA electroporation of CD8 TILs, caCD40 elevated IFN-γ and TNF-α production and cytolytic activity in the presence of autologous but not HLA-I-mismatched melanoma. Enhanced killing of autologous melanoma by young TILs was observed 4 d posttransfection. These findings suggest that caCD40 can function as a potent T cell adjuvant and provide essential guidelines for similar manipulation of other key members of the TNFR family.

Immunological effects of hypomethylating agents

INTRODUCTION

Epigenetic changes resulting from aberrant methylation patterns are a recurrent observation in hematologic malignancies. Hypomethylating agents have a well-established role in the management of patients with high-risk myelodysplastic syndrome or acute myeloid leukemia. In addition to the direct effects of hypomethylating agents on cancer cells, there are several lines of evidence indicating a role for immune-mediated anti-tumor benefits from hypomethylating therapy. Areas covered: We reviewed the clinical and basic science literature for the effects of hypomethylating agents, including the most commonly utilized therapeutics azacitidine and decitabine, on immune cell subsets. We summarized the effects of hypomethylating agents on the frequency and function of natural killer cells, T cells, and dendritic cells. In particular, we highlight the effects of hypomethylating agents on expression of immune checkpoint inhibitors, leukemia-associated antigens, and endogenous retroviral elements. Expert commentary: In vitro and ex vivo studies indicate mixed effects on the function of natural killer, dendritic cells and T cells following treatment with hypomethylating agents. Clinical correlates of immune function have suggested that hypomethylating agents have immunomodulatory functions with the potential to synergize with immune checkpoint therapy for the treatment of hematologic malignancy, and has become an active area of clinical research.