ALBERT

Description: The identification of molecules responsible for apoptotic cell (AC) uptake by dendritic cells (DCs) and induction of T-cell immunity against AC-associated antigens is a challenge in immunology. DCs differentiated in the presence of interferon-α (IFN-α–conditioned DCs) exhibit a marked phagocytic activity and a special attitude in inducing CD8+ T-cell response. In this study, we found marked overexpression of the scavenger receptor oxidized low-density lipoprotein receptor 1 (LOX-1) in IFN-α–conditioned DCs, which was associated with increased levels of genes belonging to immune response families and high competence in inducing T-cell immunity against antigens derived from allogeneic apoptotic lymphocytes. In particular, the capture of ACs by IFN-α DCs led to a substantial subcellular rearrangement of major histocompatibility complex class I and class II molecules, along with enhanced cross-priming of autologous CD8+ T cells and CD4+ T-cell activation. Remarkably, AC uptake, CD8+ T-cell cross-priming, and, to a lesser extent, priming of CD4+ T lymphocytes were inhibited by a neutralizing antibody to the scavenger receptor LOX-1 protein. These results unravel a novel LOX-1–dependent pathway by which IFN-α can, under both physiologic and pathologic conditions, render DCs fully competent for presenting AC-associated antigens for cross-priming CD8+ effector T cells, concomitantly with CD4+ T helper cell activation.

Description: Interferon consensus sequence-binding protein (ICSBP) is a transcription factor belonging to the interferon regulatory factor (IRF) family, recently shown to play a critical role in dendritic cell (DC) differentiation. Here, we analyzed the role of ICSBP in the development and trafficking of epidermal Langerhans cells (LCs) and dermal DCs and the implications for initiation of a competent immune response. ICSBP-/- mice exhibited a reduced frequency of LCs and a delayed mobility of DCs from skin that reflected a slower turnover rate in lymph nodes during steady-state conditions. Even under inflammatory changes, ICSBP-/- DCs displayed reduced mobility from skin to lymph nodes and, as a consequence, failed to induce a contact hypersensitivity (CHS) response, suggesting that these DCs were unable to initiate a competent antigen (Ag)–specific T-cell–mediated immunity. Moreover, bone marrow (BM)–derived DCs from ICSBP-/- mice exhibited an immature phenotype and a severe reduction of interleukin 12 (IL-12) expression. These BM DCs also showed a marked defect in their migratory response to macrophage inflammatory protein 3α (MIP-3α), MIP-3β, and the CC chemokine CCL21/6Ckine, which was paralleled by an impaired expression of the CC chemokine receptors, CCR6 and CCR7. Together, these results indicate that ICSBP is critically required for the development and trafficking of skin DCs, thus playing a critical role in the DC-mediated initiation of T-cell immunity.

Description: The migration capability of dendritic cells (DCs) is regulated by their response to factors, namely chemokines, that characterize maturation stage and shape their functional activities. This study examines the morphology, expression of chemokines/chemokine receptors, and migration properties of DCs generated after treatment of monocytes with type I interferon (IFN) and granulocyte-macrophage colony-stimulating factor (GM-CSF) (IFN-DCs). IFN-DCs showed phenotypical and morphologic features undetectable in DCs generated in the presence of interleukin 4 (IL-4) and GM-CSF, such as expression of CD83 and CD25 and the presence of CD44+, highly polarized, thin, and long dendrites. IFN-DCs markedly migrated in response to β-chemokines (especially MIP-1β) and expressed the Th-1 chemokine IP-10. Notably, IFN-DCs showed an up-regulation of CCR7 as well as of its natural ligand MIP-3β, characteristics typical of mature DCs. Of interest, IFN-DCs exhibited a marked chemotactic response to MIP-3β in vitro and strong migratory behavior in severe combined immunodeficient (SCID) mice. In SCID mice reconstituted with human peripheral blood leukocytes, IFN-DCs induced a potent primary human antibody response and IFN-γ production, indicative of a Th-1 immune response. These results define the highly specialized maturation state of IFN-DCs and point out the existence of a “natural alliance” between type I IFN and monocyte/DC development, instrumental for ensuring an efficient connection between innate and adaptive immunity.

Description: Purpose: We have developed a novel DC population differentiated from human monocytes in the presence of GM-CSF and IFN-alpha (IFN-DC), which is highly efficient in internalizing tumour cell antigens and in the cross-priming of CD8+T cells, promoting efficient anti-lymphoma response. Preclinical results prompted us to start a clinical trial of IFN-DC combined with low-dose Rituximab(RTX) in patients with Follicular lymphoma (FL), which is an indolent, immune-responsive, but still incurable cancer. Patients and Methods: In October 2014 we started a phase I clinical trial (EudraCT: 2013-003158-25) testing safety, immunogenicity and systemic clinical responses of low-dose RTX combined with autologous IFN-DC, administered by intra-nodal injections. Patients features: age 18-75y, indolent FL, relapsed or refractory (R/R), stage III-IV low tumour burden, with at least 1 superficial pathologic lymph node. One leukapheresis was scheduled at study entry for harvesting mononuclear cells. Eight cycles of RTX (5-20mg) and IFN-DC (30±10x106) were planned: the first 4 every two weeks, followed by other 4 cycles administered monthly. All injections were delivered with the aid of an ultrasound guide. Blood test for immune-responses and autoimmunity markers were scheduled at 0,+72d, +132 days ; +9; +18;+24 months. Results: as of the 31st July 2018, 8 patients have completed treatment and have been evaluated for response (median follow-up=24 months; range=8-45 mo). Median age of the study population was 60 years (range 27-76). All subjects had disseminated disease and enlarged lymph nodes or lesions greater than 1.5 cm at multiple sites available for local injections and monitoring for distant response. All patients were R/R after previous systemic therapy (median lines=2, range1-4) and 3/8 (37.5%) after auto-transplantation. The treatment was very well tolerated and manageable. No relevant adverse events were observed. Four out of 8 (50%) patients had objective response (OR) with 3/8(37.5%) attaining complete remission (CR); 2/8 (25%) are in stable disease at +8 and +25 months; 2/8 (25%), who did not achieve OR, progressed at +8 and +14 respectively. One patient progressed 4 months after achieving CR (Figure1). In all patients who achieved OR or who are in stable disease, induction of a tumour specific immune response was observed. Conclusions: local RTX and IFN-DC combined therapy was effective in eliciting in 50% of R/R FL with low tumour burden systemic and durable responses, which were associated with induction of specific anti-FL T cell responses. Disclosures No relevant conflicts of interest to declare.

Description: Cross-presentation allows antigen-presenting cells to present exogenous antigens to CD8+ T cells, playing an essential role in controlling infections and tumor development. IFN-α induces the rapid differentiation of human mono-cytes into dendritic cells, known as IFN-DCs, highly efficient in mediating cross-presentation, as well as the cross-priming of CD8+ T cells. Here, we have investigated the mechanisms underlying the cross-presentation ability of IFN-DCs by studying the intracellular sorting of soluble ovalbumin and nonstructural-3 protein of hepatitis C virus. Our results demonstrate that, independently from the route and mechanism of antigen entry, IFN-DCs are extraordinarily competent in preserving internalized proteins from early degradation and in routing antigens toward the MHC class-I processing pathway, allowing long-lasting, cross-priming capacity. In IFN-DCs, both early and recycling endosomes function as key compartments for the storage of both antigens and MHC-class I molecules and for proteasome- and transporter-associated with Ag processing–dependent auxiliary cross-presentation pathways. Because IFN-DCs closely resemble human DCs naturally occurring in vivo in response to infections and other danger signals, these findings may have important implications for the design of vaccination strategies in neoplastic or chronic infectious diseases.

Description: Chronic myelogenous leukemia (CML) is a malignant myeloproliferative disease arising from the clonal expansion of a stem cell expressing the bcr/abl oncogene. CML patients frequently respond to treatment with interferon-α (IFN-α), even though the mechanisms of the response remain unclear. In the present study, we evaluated the role of IFN-α in differentiation and activity of monocyte-derived dendritic cells (DCs) from CML patients as well as in modulation of the cell response to lipopolysaccharide (LPS). Treatment of CML monocytes with IFN-α and granulocyte-macrophage colony-stimulating factor (GM-CSF) resulted in the rapid generation of activated DCs (CML-IFN-DCs) expressing interleukin-15 (IL-15) and the antiapoptotic bcl-2 gene. These cells were fully competent to induce IFN-γ production by cocultured autologous T lymphocytes and expansion of CD8+ T cells. LPS treatment of CML-IFN-DCs, but not of immature DCs generated in the presence of IL-4/GM-CSF, induced the generation of CD8+ T cells reactive against autologous leukemic CD34+ cells. Altogether, these results suggest that (1) the generation of highly active monocyte-derived DCs could be important for the induction of an antitumor response in IFN-treated CML patients and (2) IFN-α can represent a valuable cytokine for the rapid generation of active monocyte-derived DCs to be utilized for vaccination strategies of CML patients. (Blood. 2004;103:980-987)

Description: Resting dendritic cells (DCs) are resident in most tissues and can be activated by environmental stimuli to mature into potent antigen-presenting cells. One important stimulus for DC activation is infection; DCs can be triggered through receptors that recognize microbial components directly or by contact with infection-induced cytokines. We show here that murine DCs undergo phenotypic maturation upon exposure to type I interferons (type I IFNs) in vivo or in vitro. Moreover, DCs either derived from bone marrow cells in vitro or isolated from the spleens of normal animals express IFN-α and IFN-β, suggesting that type I IFNs can act in an autocrine manner to activate DCs. Consistent with this idea, the ability to respond to type I IFN was required for the generation of fully activated DCs from bone marrow precursors, as DCs derived from the bone marrow of mice lacking a functional receptor for type I IFN had reduced expression of costimulatory and adhesion molecules and a diminished ability to stimulate naive T-cell proliferation compared with DCs derived from control bone marrow. Furthermore, the addition of neutralizing anti–IFN-α/β antibody to purified splenic DCs in vitro partially blocked the “spontaneous” activation of these cells, inhibiting the up-regulation of costimulatory molecules, secretion of IFN-γ, and T-cell stimulatory activity. These results show that DCs both secrete and respond to type I IFN, identifying type I interferons as autocrine DC activators.

Description: CCL2 (MCP-1) has been shown to enhance HIV-1 replication. The expression of this chemokine by macrophages is up-modulated as a consequence of viral infection or gp120 exposure. In this study, we show for the first time that the phosphatidylcholine-specific phospholipase C (PC-PLC) is required for the production of CCL2 triggered by gp120 in human monocyte-derived macrophages (MDMs). Using a combination of pharmacologic inhibition, confocal laser-scanner microscopy, and enzymatic activity assay, we demonstrate that R5 gp120 interaction with CCR5 activates PC-PLC, as assessed by a time-dependent modification of its subcellular distribution and a concentration-dependent increase of its enzymatic activity. Furthermore, PC-PLC is required for NF-kB–mediated CCL2 production triggered by R5 gp120. Notably, PC-PLC activation through CCR5 is specifically induced by gp120, since triggering CCR5 through its natural ligand CCL4 (MIP-1β) does not affect PC-PLC cellular distribution and enzymatic activity, as well as CCL2 secretion, thus suggesting that different signaling pathways can be activated through CCR5 interaction with HIV-1 or chemokine ligands. The identification of PC-PLC as a critical mediator of well-defined gp120-mediated effects in MDMs unravels a novel mechanism involved in bystander activation and may contribute to define potential therapeutic targets to block Env-triggered pathologic responses.

Description: INTRODUCTION Follicular lymphoma (FL) is considered a chronic, immune responsive and still incurable tumour. Recently two papers have shown the efficacy of active immunotherapy by repeated administration of autologous dendritic cells (DC) in Follicular Lymphoma (FL). Notably, in both studies a third of patients achieved long lasting remission. A novel DC population (IFN-DC), differentiated from human monocytes in the presence of GM-CSF and IFN-alpha has been developed in the laboratory of the Istituto Superiore di Sanità (ISS). IFN-DC have been demonstrated highly efficient in internalizing tumour-cell antigens, recovering "in vitro" T-cell responses from FL patients, as well as in mediating NK cell activation and enhanced cytotoxic effector function toward autologous FL cells. We have recently started a phase I study (approved by EC in 2014, EudraCT: 2013-003158-25) of intranodal immunotherapy based on sequential injection of low-dose anti-CD20 antibody (Ab) and IFN-D, in patients with advanced FL. Here we report early results of the ongoing trial. STUDY DESIGN IFN-DC Trial (EudraCT: 2013-003158-25) is a phase I trial aiming at evaluating safety and tolerability as well as immune and clinical responses of a IFN-DC based therapy in combination with rituximab for the treatment of patients with advanced FL. · The Primary endpoints are: I) Evaluation of safety and tolerability of treatment II) Evaluation of tumor-specific immune responses. by determining: i) Tumor-specific immune response in peripheral blood; ii) Intratumoral infiltration of immune cells; iii) DTH test. · The secondary endpoint is clinical response. The study population consists of patients with relapsed/refractory FL, aged 18-75 years, not needing immediate retreatment basing on the GELF Criteria. The · Treatment: the regimen foresees eight injection cycles, each consisting of the combined administration of rituximab and IFN-DC. The first four administered every two-weeks and the remaining four administered monthly. Rituximab (5-10mg) and low or high doses of IFN-DC (20±5 x106 or 40±5x106cells respectively), are administered by intranodal direct injection (IDI). RESULTS Five patients have been enrolled so far. The treatment proved to be safe, feasible and well tolerated. Three patients have completed treatment and two experienced complete remission with disappearance of both proximal and distal lesions, as confirmed by PET scan. Notably in both patients the distal lymph nodes, which had not been directly treated by intranodal injections, reduced to normal size earlier than those treated by IDI (abscopal effect). One of these two is still in durable complete clinical and molecular remission after 17 months while the latter patient, who had progressed after completing eight cycles of treatment, experienced a complete clinical remission after a second course of immunotherapy ( Fig.1). Two out of three patients performed the DHT test and, despite one of the two achieved remission, they both resulted non-responsive. The characterization of IFN-DC and lymphoma nodes in FL patients have shown high expression of PD-1 and PD-L1 in FL microenvironment and on IFN-DC respectively. Immunomonitoring is currently underway. However, quantification of NF-kB (p65) nuclear translocation by multispectral image flow cytometry, as a marker of NK cell activation, showed the persistence of higher percentages of activated NK cells in the two responding patients (Fig.2). CONCLUSION Currently no definitive data prove the benefit of IDI treatment, however the trial is ongoing and other patients are under screening. Notably both the responding patients showed the abscopal effect. The possible set-up of an effective and comparatively economic treatment, that exploits patients' immune system against this chronic and immune responsive tumour, is worth of exploring. Furthermore it can be envisaged that the combination of immune checkpoint inhibitor antibodies to DC-based therapies, might improve clinical activity of DC-based strategies. Disclosures No relevant conflicts of interest to declare.

Description: In a previous study, we reported that a single injection of cyclophosphamide (CTX) in tumor-bearing mice resulted in tumor eradication when the animals were subsequently injected with tumor-sensitized lymphocytes. Notably, CTX acted by inducing bystander effects on T cells, and the response to the combined CTX/adoptive immunotherapy regimen was inhibited in mice treated with antibodies to mouse interferon (IFN)–/β. In the present study, we have investigated whether CTX induced the expression of type I IFN, and we have characterized the CTX effects on the phenotype of T cells in normal mice. CTX injection resulted in an accumulation of type I IFN messenger RNA in the spleen of inoculated mice, at 24 to 48 hours, that was associated with IFN detection in the majority of the animals. CTX also enhanced the expression of the Ly-6C on spleen lymphocytes. This enhancement was inhibited in mice treated with anti–type I IFN antibodies. Moreover, CTX induced a long-lasting increase in in vivo lymphocyte proliferation and in the percentage of CD44hiCD4+ and CD44hiCD8+T lymphocytes. These results demonstrate that CTX is an inducer of type I IFN in vivo and enhances the number of T cells exhibiting the CD44hi memory phenotype. Since type I IFN has been recently recognized as the important cytokine for the in vivo expansion and long-term survival of memory T cells, we suggest that induction of this cytokine may explain at least part of the immunomodulatory effects observed after CTX treatment. Finally, these findings provide a new rationale for combined treatments with CTX and adoptive immunotherapy in cancer patients.