Amelioration of experimental autoimmune encephalomyelitis by in vivo reprogramming of macrophages using pro-resolving factors.

BACKGROUND: Reinstating inflammation resolution represents an innovative concept to regain inflammation control in diseases marked by chronic inflammation. While most therapeutics target inflammatory molecules and inflammatory effector cells and mediators, targeting macrophages to initiate inflammation resolution to control neuroinflammation has not yet been attempted. Resolution-phase macrophages are critical in the resolution process to regain tissue homeostasis, and are programmed through the presence and elimination of apoptotic leukocytes. Hence, inducing resolution-phase macrophages might represent an innovative therapeutic approach to control and terminate dysregulated neuroinflammation. METHODS: Here, we investigated if the factors released by in vitro induced resolution-phase macrophages (their secretome) are able to therapeutically reprogram macrophages to control neuroinflammation in the model of experimental autoimmune encephalomyelitis (EAE). RESULTS: We found that injection of the pro-resolutive secretome reduced demyelination and decreased inflammatory cell infiltration in the CNS, notably through the in vivo reprogramming of macrophages at the epigenetic level. Adoptive transfer experiments with in vivo or in vitro reprogrammed macrophages using such pro-resolutive secretome confirmed the stability and transferability of this acquired therapeutic activity. CONCLUSIONS: Overall, our data confirm the therapeutic activity of a pro-resolution secretome in the treatment of ongoing CNS inflammation, via the epigenetic reprogramming of macrophages and open with that a new therapeutic avenue for diseases marked by neuroinflammation.

Photopheresis efficacy in the treatment of rheumatoid arthritis: a pre-clinical proof of concept.

BACKGROUND: Despite major advances in rheumatoid arthritis outcome, not all patients achieve remission, and there is still an unmet need for new therapeutic approaches. This study aimed at evaluating in a pre-clinical murine model the efficacy of extracorporeal photopheresis (ECP) in the treatment of rheumatoid arthritis, and to provide a relevant study model for dissecting ECP mechanism of action in autoimmune diseases. METHODS: DBA/1 mice were immunized by subcutaneous injection of bovine collagen type II, in order to initiate the development of collagen-induced arthritis (CIA). Arthritic mice received 3 ECP treatments every other day, with psoralen + UVA-treated (PUVA) spleen cells obtained from arthritic mice. Arthritis score was measured, and immune cell subsets were monitored. RESULTS: ECP-treated mice recovered from arthritis as evidenced by a decreasing arthritic score over time. Significant decrease in the frequency of Th17 cells in the spleen of treated mice was observed. Interestingly, while PUVA-treated spleen cells from healthy mouse had no effect, PUVA-treated arthritic mouse derived-spleen cells were able to induce control of arthritis development. CONCLUSIONS: Our results demonstrate that ECP can control arthritis in CIA-mice, and clarifies ECP mechanisms of action, showing ECP efficacy and Th17 decrease only when arthritogenic T cells are contained within the treated sample. These data represent a pre-clinical proof of concept supporting the use of ECP in the treatment of RA in Human.

LXR agonist treatment of blastic plasmacytoid dendritic cell neoplasm restores cholesterol efflux and triggers apoptosis.

Blastic plasmacytoid dendritic cell (PDC) neoplasm (BPDCN) is an aggressive hematological malignancy with a poor prognosis that derives from PDCs. No consensus for optimal treatment modalities is available today and the full characterization of this leukemia is still emerging. We identified here a BPDCN-specific transcriptomic profile when compared with those of acute myeloid leukemia and T-acute lymphoblastic leukemia, as well as the transcriptomic signature of primary PDCs. This BPDCN gene signature identified a dysregulation of genes involved in cholesterol homeostasis, some of them being liver X receptor (LXR) target genes. LXR agonist treatment of primary BPDCN cells and BPDCN cell lines restored LXR target gene expression and increased cholesterol efflux via the upregulation of adenosine triphosphate-binding cassette (ABC) transporters, ABCA1 and ABCG1. LXR agonist treatment was responsible for limiting BPDCN cell proliferation and inducing intrinsic apoptotic cell death. LXR activation in BPDCN cells was shown to interfere with 3 signaling pathways associated with leukemic cell survival, namely: NF-κB activation, as well as Akt and STAT5 phosphorylation in response to the BPDCN growth/survival factor interleukin-3. These effects were increased by the stimulation of cholesterol efflux through a lipid acceptor, the apolipoprotein A1. In vivo experiments using a mouse model of BPDCN cell xenograft revealed a decrease of leukemic cell infiltration and BPDCN-induced cytopenia associated with increased survival after LXR agonist treatment. This demonstrates that cholesterol homeostasis is modified in BPDCN and can be normalized by treatment with LXR agonists which can be proposed as a new therapeutic approach.

Plasmacytoid Dendritic Cells Die by the CD8 T Cell-Dependent Perforin Pathway during Acute Nonviral Inflammation.

Regulation of the inflammatory response involves the control of dendritic cell survival. To our knowledge, nothing is known about the survival of plasmacytoid dendritic cells (pDC) in such situation. pDC are specialized in type I IFN (IFN-I) secretion to control viral infections, and IFN-I also negatively regulate pDC survival during the course of viral infections. In this study, we asked about pDC behavior in the setting of virus-free inflammation. We report that pDC survival was profoundly reduced during different nonviral inflammatory situations in the mouse, through a mechanism independent of IFN-I and TLR signaling. Indeed, we demonstrated that during inflammation, CD8(+) T cells induced pDC apoptosis through the perforin pathway. The data suggest, therefore, that pDC have to be turned down during ongoing acute inflammation to not initiate autoimmunity. Manipulating CD8(+) T cell response may therefore represent a new therapeutic opportunity for the treatment of pDC-associated autoimmune diseases, such as lupus or psoriasis.

Bortezomib as a new therapeutic approach for blastic plasmacytoid dendritic cell neoplasm.

Blastic plasmacytoid dendritic cell neoplasm is an aggressive hematologic malignancy with a poor prognosis. No consensus regarding optimal treatment modalities is currently available. Targeting the nuclear factor-kappa B pathway is considered a promising approach since blastic plasmacytoid dendritic cell neoplasm has been reported to exhibit constitutive activation of this pathway. Moreover, nuclear factor-kappa B inhibition in blastic plasmacytoid dendritic cell neoplasm cell lines, achieved using either an experimental specific inhibitor JSH23 or the clinical drug bortezomib, interferes in vitro with leukemic cell proliferation and survival. Here we extended these data by showing that primary blastic plasmacytoid dendritic cell neoplasm cells from seven patients were sensitive to bortezomib-induced cell death. We confirmed that bortezomib efficiently inhibits the phosphorylation of the RelA nuclear factor-kappa B subunit in blastic plasmacytoid dendritic cell neoplasm cell lines and primary cells from patients in vitro and in vivo in a mouse model. We then demonstrated that bortezomib can be associated with other drugs used in different chemotherapy regimens to improve its impact on leukemic cell death. Indeed, when primary blastic plasmacytoid dendritic cell neoplasm cells from a patient were grafted into mice, bortezomib treatment significantly increased the animals' survival, and was associated with a significant decrease of circulating leukemic cells and RelA nuclear factor-kappa B subunit expression. Overall, our results provide a rationale for the use of bortezomib in combination with other chemotherapy for the treatment of patients with blastic plasmacytoid dendritic cell neoplasm. Based on our data, a prospective clinical trial combining proteasome inhibitor with classical drugs could be envisaged.

Human monocyte-derived suppressor cells control graft-versus-host disease by inducing regulatory forkhead box protein 3-positive CD8+ T lymphocytes.

BACKGROUND: Adoptive transfer of immunosuppressive cells has emerged as a promising strategy for the treatment of immune-mediated disorders. However, only a limited number of such cells can be isolated from in vivo specimens. Therefore efficient ex vivo differentiation and expansion procedures are critically needed to produce a clinically relevant amount of these suppressive cells. OBJECTIVE: We sought to develop a novel, clinically relevant, and feasible approach to generate ex vivo a subpopulation of human suppressor cells of monocytic origin, referred to as human monocyte-derived suppressive cells (HuMoSCs), which can be used as an efficient therapeutic tool to treat inflammatory disorders. METHODS: HuMoSCs were generated from human monocytes cultured for 7 days with GM-CSF and IL-6. The immune-regulatory properties of HuMoSCs were investigated in vitro and in vivo. The therapeutic efficacy of HuMoSCs was evaluated by using a graft-versus-host disease (GvHD) model of humanized mice (NOD/SCID/IL-2Rγc(-/-) [NSG] mice). RESULTS: CD33+ HuMoSCs are highly potent at inhibiting the proliferation and activation of autologous and allogeneic effector T lymphocytes in vitro and in vivo. The suppressive activity of these cells depends on signal transducer and activator of transcription 3 activation. Of therapeutic relevance, HuMoSCs induce long-lasting memory forkhead box protein 3-positive CD8+ regulatory T lymphocytes and significantly reduce GvHD induced with human PBMCs in NSG mice. CONCLUSION: Ex vivo-generated HuMoSCs inhibit effector T lymphocytes, promote the expansion of immunosuppressive forkhead box protein 3-positive CD8+ regulatory T cells, and can be used as an efficient therapeutic tool to prevent GvHD.

Transforming growth factor-ß released by apoptotic white blood cells during red blood cell storage promotes transfusion-induced alloimmunomodulation.

BACKGROUND: Red blood cell (RBC) alloimmunization is a major immunologic risk of transfusion. However, RBC storage facilitates white blood cell (WBC) apoptosis and apoptotic cells have immunomodulatory properties. We investigated the behavior of WBCs, and apoptosis in particular, in RBC units during storage and then studied the impact of WBC apoptosis on the modulation of posttransfusion alloimmunization in RBC products stored short term. STUDY DESIGN AND METHODS: We used a mouse model of alloimmunization to transfused HEL-ovalbumin-Duffy (HOD) surface antigen expressed specifically on RBCs. The presence of circulating anti-HOD immunoglobulin G detected by flow cytometry confirmed immunization to HOD+ RBCs. WBC apoptosis and factors released by apoptotic WBCs during storage were determined and in particular the role of transforming growth factor (TGF)-ß was assessed on RBC alloimmunization. RESULTS: In blood stored 72 hours, 30% of WBCs were apoptotic, and transfusion of short-term-stored blood resulted in lesser immunization than did fresh blood or stored leukoreduced (LR) RBCs. WBCs undergoing apoptosis released during short-term storage factors modulating RBC alloimmunization. Indeed apoptotic cell-released factors modulate alloimmunization whereas exogenous apoptotic cells directly transfused with LR RBCs did not. While microparticles released during RBC storage had no immunomodulatory role, TGF-ß found in the supernatant of stored blood demonstrated the capacity to favor Treg polarization of naïve CD4+CD25- T cells in vitro and limited RBC alloimmunization in vivo. Indeed, addition of recombinant TGF-ß to stored LR RBC transfusion strongly limited posttransfusion RBC alloimmunization. CONCLUSION: Our findings show that short-term storage of non-LR blood facilitates WBC apoptosis therefore releasing TGF-ß that modulates posttransfusion RBC alloimmunization.

Characterization of atypical T cells generated during ex vivo expansion process for T cell-based adoptive immunotherapy.

Engineered T cell-based adoptive immunotherapies met promising success for the treatment of hematological malignancies. Nevertheless, major hurdles remain to be overcome regarding the management of relapses and the translation to solid tumor settings. Properties of T cell-based final product should be appropriately controlled to fine-tune the analysis of clinical trial results, to draw relevant conclusions, and finally to improve the efficacy of these immunotherapies. For this purpose, we addressed the existence of atypical T cell subsets and deciphered their phenotypic and functional features in an HPV16-E7 specific and MHC II-restricted transgenic-TCR-engineered T cell setting. To note, atypical T cell subsets include mismatched MHC/co-receptor CD8 or CD4 and miscommitted CD8+ or CD4+ T cells. We generated both mismatched and appropriately matched MHC II-restricted transgenic TCR on CD8 and CD4-expressing T cells, respectively. We established that CD4+ cultured T cells exhibited miscommitted phenotypic cytotoxic pattern and that both interleukin (IL)-2 or IL-7/IL-15 supplementation allowed for the development of this cytotoxic phenotype. Both CD4+ and CD8+ T cell subsets, transduced with HPV16-E7 specific transgenic TCR, demonstrated cytotoxic features after exposure to HPV-16 E7-derived antigen. Ultimately, the presence of such atypical T cells, either mismatched MHC II-restricted TCR/CD8+ T cells or cytotoxic CD4+ T cells, is likely to influence the fate of patient-infused T cell product and would need further investigation.

Impact of scFv on Functionality and Safety of Third-Generation CD123 CAR T Cells.

Chimeric antigen receptor (CAR) T cells express an extracellular domain consisting of a single-chain fragment variable (scFv) targeting a surface tumor-associated antigen. scFv selection should involve safety profiling with evaluation of the efficacy/toxicity balance, especially when the target antigen also is expressed on healthy cells. Here, to assess differences in terms of efficacy and on-target/off-tumor effects, we generated five different CARs targeting CD123 by substituting only the scFv. In in vitro models, T cells engineered to express three of these five CD123 CARs were effectively cytotoxic on leukemic cells without increasing lysis of monocytes or endothelial cells. Using the IncuCyte system, we confirmed the low cytotoxicity of CD123 CAR T cells on endothelial cells. Hematotoxicity evaluation using progenitor culture and CD34 cell lysis showed that two of the five CD123 CAR T cells were less cytotoxic on hematopoietic stem cells. Using a humanized mouse model, we confirmed that CD123- cells were not eliminated by the CD123 CAR T cells. Two CD123 CAR T cells reduced tumor infiltration and increased the overall survival of mice in three in vivo models of blastic plasmacytoid dendritic cell neoplasm. In an aggressive version of this model, bulk RNA sequencing analysis showed that these CD123 CAR T cells upregulated genes associated with cytotoxicity and activation/exhaustion a few days after the injection. Together, these results emphasize the importance of screening different scFvs for the development of CAR constructs to support selection of cells with the optimal risk-benefit ratio for clinical development.

Plasmacytoid dendritic cells play a major role in apoptotic leukocyte-induced immune modulation.

Several APCs participate in apoptotic cell-induced immune modulation. Whether plasmacytoid dendritic cells (PDCs) are involved in this process has not yet been characterized. Using a mouse model of allogeneic bone marrow engraftment, we demonstrated that donor bone marrow PDCs are required for both donor apoptotic cell-induced engraftment and regulatory T cell (Treg) increase. We confirmed in naive mice receiving i.v. syngeneic apoptotic cell infusion that PDCs from the spleen induce ex vivo Treg commitment. We showed that PDCs did not interact directly with apoptotic cells. In contrast, in vivo macrophage depletion experiments using clodronate-loaded liposome infusion and coculture experiments with supernatant from macrophages incubated with apoptotic cells showed that PDCs required macrophage-derived soluble factors--including TGF-ß--to exert their immunomodulatory functions. Overall, PDCs may be considered as the major APC involved in Treg stimulation/generation in the setting of an immunosuppressive environment obtained by apoptotic cell infusion. These findings show that like other APCs, PDC functions are influenced, at least indirectly, by exposure to blood-borne apoptotic cells. This might correspond with an additional mechanism preventing unwanted immune responses against self-antigens clustered at the cell surface of apoptotic cells occurring during normal cell turnover.

TGF-beta-exposed plasmacytoid dendritic cells participate in Th17 commitment.

TGF-ß is required for both Foxp3(+) regulatory T cell (Treg) and Th17 commitment. Plasmacytoid DCs (pDC) have been shown to participate to both Treg and Th17 commitment as well. However, few studies have evaluated the direct effect of TGF-ß on pDC, and to our knowledge, no study has assessed the capacity of TGF-ß-exposed pDC to polarize naive CD4(+) T cells. In this paper, we show that TGF-ß-treated pDC favor Th17 but not Treg commitment. This process involves a TGF-ß/Smad signal, because TGF-ß treatment induced Smad2 phosphorylation in pDC and blockade of TGF-ß signaling with the SD208 TGF-ßRI kinase inhibitor abrogated Th17 commitment induced by TGF-ß-treated pDC. Moreover, TGF-ß mRNA synthesis and active TGF-ß release were induced in TGF-ß-treated pDC and anti-TGF-ß Ab blocked Th17 commitment. Unexpectedly, TGF-ß treatment also induced increased IL-6 production by pDC, which serves as the other arm for Th17 commitment driven by TGF-ß-exposed pDC, because elimination of IL-6-mediated signal with either IL-6- or IL-6Rα-specific Abs prevented Th17 commitment. The in vivo pathogenic role of TGF-ß-treated pDC was further confirmed in the Th17-dependent collagen-induced arthritis model in which TGF-ß-treated pDC injection significantly increased arthritis severity and pathogenic Th17 cell accumulation in the draining lymph nodes. Thus, our data reveal a previously unrecognized effect of TGF-ß-rich environment on pDC ability to trigger Th17 commitment. Such findings have implications in the pathogenesis of autoimmune diseases or immune responses against mucosal extracellular pathogens.

Resolution therapy: Harnessing efferocytic macrophages to trigger the resolution of inflammation.

Several chronic inflammatory diseases are associated with non-resolving inflammation. Conventional anti-inflammatory drugs fail to completely cure these diseases. Resolution pharmacology is a new therapeutic approach based on the use of pro-resolving mediators that accelerate the resolution phase of inflammation by targeting the productive phase of inflammation. Indeed, pro-resolving mediators prevent leukocyte recruitment and induce apoptosis of accumulated leukocytes. This approach is now called resolution therapy with the introduction of complex biological drugs and cell-based therapies. The main objective of resolution therapy is to specifically reduce the duration of the resolution phase to accelerate the return to homeostasis. Under physiological conditions, macrophages play a critical role in the resolution of inflammation. Indeed, after the removal of apoptotic cells (a process called efferocytosis), macrophages display anti-inflammatory reprogramming and subsequently secrete multiple pro-resolving factors. These factors can be used as resolution therapy. Here, we review the different mechanisms leading to anti-inflammatory reprogramming of macrophages after efferocytosis and the pro-resolving factors released by these efferocytic macrophages. We classify these mechanisms in three different categories: macrophage reprogramming induced by apoptotic cell-derived factors, by molecules expressed by apoptotic cells (i.e., "eat-me" signals), and induced by the digestion of apoptotic cell-derived materials. We also evoke that macrophage reprogramming may result from cooperative mechanisms, for instance, implicating the apoptotic cell-induced microenvironment (including cellular metabolites, specific cytokines or immune cells). Then, we describe a new drug candidate belonging to this resolution therapy. This candidate, called SuperMApo, corresponds to the secretome of efferocytic macrophages. We discuss its production, the pro-resolving factors present in this drug, as well as the results obtained in experimental models of chronic (e.g., arthritis, colitis) and acute (e.g., peritonitis or xenogeneic graft-versus-host disease) inflammatory diseases.

Mini-Review: The Administration of Apoptotic Cells for Treating Rheumatoid Arthritis: Current Knowledge and Clinical Perspectives.

Rheumatoid arthritis (RA) is a chronic immune-mediated disease managed by conventional synthetic drugs, such as methotrexate (MTX), and targeted drugs including biological agents. Cell-based therapeutic approaches are currently developed in RA, mainly mesenchymal stroma cell-based approaches. Early-stage apoptotic cells possess direct and indirect anti-inflammatory properties. During the elimination of dying cells (a process called efferocytosis), specific mechanisms operate to control immune responses. There are compelling evidences in experimental models of arthritis indicating that apoptotic cell administration may benefit joint inflammation, and may even have therapeutic effects on arthritis. Additionally, it has been demonstrated that apoptotic cells could be administered with standard treatments of RA, such as MTX or TNF inhibitors (TNFi), given even a synergistic response with TNFi. Interestingly, apoptotic cell infusion has been successfully experienced to prevent acute graft-vs.-host disease after hematopoietic cell transplantation in patients with hematologic malignancies, with a good safety profile. In this mini-review, the apoptotic cell-based therapy development in arthritis is discussed, as well as its transfer in the short-term to an innovative treatment for patients with RA. The use of apoptotic cell-derived factors, including secretome or phosphatidylserine-containing liposomes, in RA are also discussed.

Pro-Resolving Factors Released by Macrophages After Efferocytosis Promote Mucosal Wound Healing in Inflammatory Bowel Disease.

Nonresolving inflammation is a critical driver of several chronic inflammatory diseases, including inflammatory bowel diseases (IBD). This unresolved inflammation may result from the persistence of an initiating stimulus or from the alteration of the resolution phase of inflammation. Elimination of apoptotic cells by macrophages (a process called efferocytosis) is a critical step in the resolution phase of inflammation. Efferocytosis participates in macrophage reprogramming and favors the release of numerous pro-resolving factors. These pro-resolving factors exert therapeutic effects in experimental autoimmune arthritis. Here, we propose to evaluate the efficacy of pro-resolving factors produced by macrophages after efferocytosis, a secretome called SuperMApo, in two IBD models, namely dextran sodium sulfate (DSS)-induced and T cell transfer-induced colitis. Reintroducing these pro-resolving factors was sufficient to decrease clinical, endoscopic and histological colitis scores in ongoing naive T cell-transfer-induced colitis and in DSS-induced colitis. Mouse primary fibroblasts isolated from the colon demonstrated enhanced healing properties in the presence of SuperMApo, as attested by their increased migratory, proliferative and contractive properties. This was confirmed by the use of human fibroblasts isolated from patients with IBD. Exposure of an intestinal epithelial cell (IEC) line to these pro-resolving factors increased their proliferative properties and IEC acquired the capacity to capture apoptotic cells. The improvement of wound healing properties induced by SuperMApo was confirmed in vivo in a biopsy forceps-wound colonic mucosa model. Further in vivo analysis in naive T cell transfer-induced colitis model demonstrated an improvement of intestinal barrier permeability after administration of SuperMApo, an intestinal cell proliferation and an increase of α-SMA expression by fibroblasts, as well as a reduction of the transcript coding for fibronectin (Fn1). Finally, we identified TGF-ß, IGF-I and VEGF among SuperMApo as necessary to favor mucosal healing and confirmed their role both in vitro (using neutralizing antibodies) and in vivo by depleting these factors from efferocytic macrophage secretome using antibody-coated microbeads. These growth factors only explained some of the beneficial effects induced by factors released by efferocytic macrophages. Overall, the administration of pro-resolving factors released by efferocytic macrophages limits intestinal inflammation and enhance tissue repair, which represents an innovative treatment of IBD.

Pro-Resolving Factor Administration Limits Cancer Progression by Enhancing Immune Response Against Cancer Cells.

Cancers are consequences of cellular dysfunction leading to an aberrant cellular multiplication and proliferation, subsequently yielding metastasis formation. Inflammatory reaction, with immune cell recruitment, is the main defense against precancerous lesions. However, an inflammatory environment also favors cancer cell progression, with cancer cell evasion from immune surveillance, leading to cancer development. Current therapeutic strategies enhance this natural immune response in order to restore immunosurveillance. The variety of these strategies is a predominant source of inflammatory mediators used by cancer cells to grow, differentiate, and migrate, therefore encouraging metastasis formation. For this reason, during cancer progression, limiting inflammation appears to be an innovative strategy to avoid the escape of cancer cells and potentially enhance the efficacy of antitumor therapies. Thus, this study aims to investigate the impact of administering pro-resolving factors (SuperMApo® drug candidate), which are inducers of inflammation resolution, in the framework of cancer treatment. We have observed that administering pro-resolving mediators issued from apoptotic cell efferocytosis by macrophages controlled peritoneal cancer progression by limiting cancer cell dissemination to the blood and mesenteric lymph nodes. This observation has been linked to an increase of macrophage mobilization in both peritoneal cavity and mesenteric lymph nodes. This control is associated to a restricted immunosuppressive myeloid cell circulation and to an IFN-γ-specific anti-tumor T-cell response. Altogether, these results suggest that administering proresolving factors could provide a new additional therapeutic alternative to control cancer progression.

BPDCN: When polychemotherapy does not compromise allogeneic CD123 CAR-T cell cytotoxicity.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematological malignancy with poor prognosis and no treatment consensus. Combining chemotherapy and immunotherapy is a promising strategy to enhance therapeutic effect. Before combining these therapies, the influence of one on the other has to be explored. We set up a model to test the combination of polychemotherapy - named methotrexate, idarubicine, dexamethasone, and L-asparaginase (MIDA) - and CD123 CAR-T cell therapy. We showed that CD123 CAR-T cells exert the same effect on BPDCN models alone, or after MIDA regimen. These data support a preclinical rationale to use immunotherapy after a treatment with polychemotherapy for BPDCN patients.

Chemoradiation triggers antitumor Th1 and tissue resident memory-polarized immune responses to improve immune checkpoint inhibitors therapy.

BACKGROUND: Multiple synergistic combination approaches with cancer drugs are developed to overcome primary resistance to immunotherapy; however, the mechanistic rationale to combine chemoradiotherapy (CRT) with immune checkpoint inhibitors remains elusive. METHODS: This study described the immunological landscape of tumor microenvironment (TME) exposed to CRT. Tumor samples from patients with rectal cancer (n=43) treated with neoadjuvant CRT or radiotherapy were analyzed by nanostring and immunohistochemistry. Studies in mice were performed using three syngeneic tumors (TC1, CT26 and MC38). Tumor-bearing mice were treated either with platinum-based CRT, radiotherapy or chemotherapy. Anti-CTLA-4 and/or anti-Programmed Cell Death Receptor-1 (PD-1) therapy was used in combination with CRT. The therapy-exposed TME was screened by RNA sequencing and flow cytometry and tumor-infiltrating T lymphocyte functionality was evaluated by interferon (IFN)-γ ELIspot and intracellular cytokine staining. RESULTS: Front-to-front comparison analysis revealed the synergistic effect of CRT to establish a highly inflamed and Th1-polarized immune signature in the TME of patients and mice. In both settings, CRT-exposed TMEs were highly enriched in newly-infiltrated tumor-specific CD8+ T cells as well as tissue resident memory CD103+CD8+ T cells. In mice, CD8 T cells were involved in the antitumor response mediated by CRT and were primed by CRT-activated CD103+ dendritic cells. In the three tumor models, we showed that concurrent combination of CRT with a dual CTLA-4 and PD-1 blockade was required to achieve an optimal antitumor effect and to establish a broad and long-lasting protective antitumor T cell immunity. CONCLUSIONS: Our results highlight the ability of CRT to stimulate strong antitumor T-cell-mediated immunity and tissue resident memory T activation in TME, to foster immune checkpoint inhibitors action. These findings have implications in clinic for the design clinical trials combining chemoradiation with immunotherapy.

CD28/4-1BB CD123 CAR T cells in blastic plasmacytoid dendritic cell neoplasm.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is associated with a remarkably poor prognosis and with no treatment consensus. The identification of relevant therapeutic targets is challenging. Here, we investigated the immune functions, antileukemia efficacy and safety of CD28/4-1BB CAR T cells targeting CD123 the interleukin (IL)-3 receptor alpha chain which is overexpressed on BPDCN. We demonstrated that both retroviral and lentiviral engineering CD28/4-1BB CD123 CAR T cells exhibit effector functions against BPDCN cells through CD123 antigen recognition and that they efficiently kill BPDCN cell lines and BPDCN-derived PDX cells. In vivo, CD28/4-1BB CD123 CAR T-cell therapy displayed strong efficacy by promoting a decrease of BPDCN blast burden. Furthermore we showed that T cells from BPDCN patient transduced with CD28/4-1BB CD123 CAR successfully eliminate autologous BPDCN blasts in vitro. Finally, we demonstrated in humanized mouse models that these effector CAR T cells exert low or no cytotoxicity against various subsets of normal cells with low CD123 expression, indicating a potentially low on-target/off-tumor toxicity effect. Collectively, our data support the further evaluation for clinical assessment of CD28/4-1BB CD123 CAR T cells in BPDCN neoplasm.

Factors Produced by Macrophages Eliminating Apoptotic Cells Demonstrate Pro-Resolutive Properties and Terminate Ongoing Inflammation.

Unresolved inflammation is a common feature in the pathogenesis of chronic inflammatory/autoimmune diseases. The factors produced by macrophages eliminating apoptotic cells during resolution are crucial to terminate inflammation, and for subsequent tissue healing. We demonstrated here that the factors produced by macrophages eliminating apoptotic cells were sufficient to reboot the resolution of inflammation in vivo, and thus definitively terminated ongoing chronic inflammation. These factors were called SuperMApo and revealed pro-resolutive properties and accelerated acute inflammation resolution, as attested by both increased phagocytic capacities of macrophages and enhanced thioglycollate-induced peritonitis resolution. Activated antigen-presenting cells exposed to SuperMApo accelerated their return to homeostasis and demonstrated pro-regulatory T cell properties. In mice with ongoing collagen-induced arthritis, SuperMApo injection resolved and definitively terminated chronic inflammation. The same pro-resolving properties were observed in human settings in addition to xenogeneic colitis and graft-vs.-host disease modulation, highlighting SuperMApo as a new therapeutic opportunity to circumvent inflammatory diseases.

Mediators involved in the immunomodulatory effects of apoptotic cells.

Immunomodulatory properties are attributed to apoptotic cells. These properties have been used to modulate allogeneic immune responses in experimental transplantation settings. In independent studies, apoptotic cell infusion has been shown to favor hematopoietic cell engraftment, to increase heart graft survival, and to delay the lethal onset of graft-versus-host disease (GVHD). The goal of this review was to discuss how apoptotic cell infusion interferes with graft rejection or host rejection (i.e., GVHD) and to focus on the potential mediators or "perpetuators" involved in apoptotic cell-induced immunomodulation. Particular emphasis on apoptotic cell phagocytosis, transforming growth factor (TGF)-beta secretion, and regulatory T cell induction was performed. Stimulating "naturally" immunosuppressive molecules (i.e., TGF-beta) or immunomodulatory cells ("alternatively-activated" macrophages, certain dendritic cell subsets, or regulatory T cells) in a physiological manner by using apoptotic cell infusion can be a promising way to induce tolerance.