Type I and II interferons (IFNs) stimulate pro-inflammatory programs that are critical for immune activation, but also induce immune-suppressive feedback circuits that impede control of cancer growth. Here, we sought to determine how these opposing programs are differentially induced. We demonstrated that the transcription factor interferon regulatory factor 2 (IRF2) was expressed by many immune cells in the tumor in response to sustained IFN signaling. CD8+ T cell-specific deletion of IRF2 prevented acquisition of the T cell exhaustion program within the tumor and instead enabled sustained effector functions that promoted long-term tumor control and increased responsiveness to immune checkpoint and adoptive cell therapies. The long-term tumor control by IRF2-deficient CD8+ T cells required continuous integration of both IFN-I and IFN-II signals. Thus, IRF2 is a foundational feedback molecule that redirects IFN signals to suppress T cell responses and represents a potential target to enhance cancer control.
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Gene therapy represents a promising treatment alternative for patients with malignant gliomas. Nevertheless, in the setting of these highly infiltrative tumors, transgene delivery remains a challenge. Indeed, viral vehicles tested in clinical trials often target only those tumor cells that are adjacent to the injection site. In this study, we examined the feasibility of using human mesenchymal stem cells (hMSC) to deliver a replication-competent oncolytic adenovirus (CRAd) in a model of intracranial malignant glioma. To do so, CRAds with a chimeric 5/3 fiber or RGD backbone with or without CXCR4 promoter driving E1A were examined with respect to replication and toxicity in hMSC, human astrocytes, and the human glioma cell line U87MG by quantitative polymerase chain reaction and membrane integrity assay. CRAd delivery by virus-loaded hMSC was then evaluated in vitro and in an in vivo model of mice bearing intracranial U87MG xenografts. Our results show that hMSC are effectively infected by CRAds that use the CXCR4 promoter. CRAd-CXCR4-RGD had the highest replication, followed by CRAd-CXCR4-5/3, in hMSC, with comparable levels of toxicity. In U87MG tumor cells, CRAd-CXCR4-5/3 showed the highest replication and toxicity. Virus-loaded hMSC effectively migrated in vitro and released CRAds that infected U87MG glioma cells. When injected away from the tumor site in vivo, hMSC migrated to the tumor and delivered 46-fold more viral copies than injection of CRAd-CXCR4-5/3 alone. Taken together, these results indicate that hMSC migrate and deliver CRAd to distant glioma cells. This delivery strategy should be explored further, as it could improve the outcome of oncolytic virotherapy for glioma.

Skin dendritic cells (DC) are professional APC critical for initiation and control of adaptive immunity. In the present work we have analyzed the CD4+ T cell stimulatory function of different subsets of DC that migrate spontaneously from human skin explants, including CD1a+CD14- Langerhans' cells (LC), CD1a-CD14- dermal DC (DDC), and CD1a-CD14+ LC precursors. Skin migratory DC consisted of APC at different stages of maturation-activation that produced IL-10, TGF-beta1, IL-23p19, and IL-12p40, but did not release IL-12p70 even after exposure to DC1-driving stimuli. LC and DDC migrated as mature/activated APC able to stimulate allogeneic naive CD4+ T cells and to induce memory Th1 cells in the absence of IL-12p70. The potent CD4+ T cell stimulatory function of LC and DDC correlated with their high levels of expression of MHC class II, adhesion, and costimulatory molecules. The Th1-biasing function of LC and DDC depended on their ability to produce IL-23. By contrast, CD1a-CD14+ LC precursors migrated as immature-semimature APC and were weak stimulators of allogeneic naive CD4+ T cells. However, and opposite of a potential tolerogenic role of immature DC, the T cell allostimulatory and Th1-biasing function of CD14+ LC precursors increased significantly by augmenting their cell number, prolonging the time of interaction with responding T cells, or addition of recombinant human IL-23 in MLC. The data presented in this study provide insight into the function of the complex network of skin-resident DC that migrate out of the epidermis and dermis after cutaneous immunizations, pathogen infections, or allograft transplantation.

CD34+ cell-derived hematopoietic precursors amplified with FLT3-ligand, thrombopoietin and stem cell factor became, after a 6-day induction with GM-CSF, IL-4 and TGF-beta1, HLA-DR+, CD1a+, CD83-, CD86-, CD80- cells. A fraction of them expressed Langerin, Lag, and E-cadherin, resembling epidermal Langerhans cells (LC). TNF-alpha added for the last 3 days only marginally induced CD83 expression, but strikingly increased the proportion of immature Langerin+CD83- LC. Langerin+CD83+ and Langerin+CD83- cells were functionally distinct, the former internalizing less efficiently Langerin than the latter. Both CD1a-CD14- and CD1a-CD14+ cells sorted from FLT3-ligand, thrombopoietin and stem cell factor cultures responded to TNF-alpha by an increase of Langerin+ cells. Thus, TNF-alpha rescued LC precursors irrespective of their commitment to the monocytic lineage. When added to GM-CSF, IL-4 and TGF-beta1 containing-cultures, LPS or IL-1beta also induced significant numbers of Langerin+CD83- immature cells displaying a low allostimulatory activity, while CD40-ligand largely promoted highly allostimulatory Langerin-CD83+ cells. Altogether, these data show that in contrast to CD40-ligand, which induced LC maturation even in presence of TGF-beta1, nonspecific proinflammatory factors such as TNF-alpha, IL-1 or LPS, essentially induced immature LC generation, and little cell activation in the presence of TGF-beta1.

Multiple sclerosis (MS) is assumed to result from autoaggressive T cell-mediated immune responses, in which T helper type 1 (Th1) cells producing cytokines, e.g. IFN-gamma and lymphotoxin promote damage of oligodendrocyte-myelin units. Dendritic cells (DCs) as potent antigen presenting cells initiate and orchestrate immune responses. Whether phenotype and function of DCs with respect to Th1 cell promotion are altered in MS, are not known. This study revealed that blood-derived DCs from MS patients expressed low levels of the costimulatory molecule CD86. In addition, production of IFN-gamma by blood mononuclear cells (MNCs) was strongly enhanced by DCs derived from MS patients. IFN-beta and IL-10 inhibited the costimulatory capacity of DCs in mixed lymphocyte reaction (MLR) and showed additive effects on suppression of IL-12 production by DCs. Correspondingly, DCs pretreated with IFN-beta and IL-10 significantly suppressed IFN-gamma production by MNCs. IFN-beta in vitro also upregulated CD80 and, in particular, CD86 expression on DCs. In vitro, anti-CD80 antibody remarkably increased, while anti-CD86 antibody inhibited DC-induced IL-4 production in MLR. We conclude that DC phenotype and function are altered in MS, implying Th1-biased responses with enhanced capacity to induce Th1 cytokine production. In vitro modification of MS patients' DCs by IFN-beta and IL-10 could represent a novel way of immunomodulation and of possible usefulness for future immunotherapy of MS.