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Autoimmune diseases such as multiple sclerosis (MS), type I diabetes (T1D), inflammatory bowel diseases (IBD), and rheumatoid arthritis (RA) are chronic, incurable, incapacitating and at times even lethal conditions. Worldwide, millions of people are affected, predominantly women, and their number is steadily increasing. Currently, autoimmune patients require lifelong immunosuppressive therapy, often accompanied by severe adverse side effects and risks. Targeting the fundamental cause of autoimmunity, which is the loss of tolerance to self- or innocuous antigens, may be achieved via various mechanisms. Recently, tolerance-inducing cellular therapies, such as tolerogenic dendritic cells (tolDCs) and regulatory T cells (Tregs), have gained considerable interest. Their safety has already been evaluated in patients with MS, arthritis, T1D, and Crohn's disease, and clinical trials are underway to confirm their safety and therapeutic potential. Cell-based therapies are inevitably expensive and time-consuming, requiring laborious manufacturing. Therefore, direct targeting of tolerogenic cell types offers an attractive alternative, and several strategies are being explored. Type I IFN was the first disease-modifying therapy approved for MS patients, and approaches to endogenously induce IFN in autoimmune diseases are being pursued vigorously. We here review and discuss tolerogenic cellular therapies and targeted tolerance approaches and propose a novel strategy for cell-specific delivery of type I IFN signaling to a cell type of choice.

Type I Interferon (IFN) was the very first drug approved for the treatment of Multiple Sclerosis (MS), and is still frequently used as a first line therapy. However, systemic IFN also causes considerable side effects, affecting therapy adherence and dose escalation. In addition, the mechanism of action of IFN in MS is multifactorial and still not completely understood. Using AcTaferons (Activity-on-Target IFNs, AFNs), optimized IFN-based immunocytokines that allow cell-specific targeting, we have previously demonstrated that specific targeting of IFN activity to dendritic cells (DCs) can protect against experimental autoimmune encephalitis (EAE), inducing in vivo tolerogenic protective effects, evidenced by increased indoleamine-2,3-dioxygenase (IDO) and transforming growth factor β (TGFβ) release by plasmacytoid (p) DCs and improved immunosuppressive capacity of regulatory T and B cells. We here report that targeting type I IFN activity specifically towards B cells also provides strong protection against EAE, and that targeting pDCs using SiglecH-AFN can significantly add to this protective effect. The superior protection achieved by simultaneous targeting of both B lymphocytes and pDCs correlated with improved IL-10 responses in B cells and conventional cDCs, and with a previously unseen very robust IDO response in several cells, including all B and T lymphocytes, cDC1 and cDC2.

Sepsis is one of the leading causes of death around the world. The failure of clinical trials to treat sepsis demonstrates that the molecular mechanisms are multiple and are still insufficiently understood. To clarify the long disputed hierarchical contribution of several central inflammatory mediators (IL-1β, IL-18, caspase [CASP] 7, CASP1, and CASP11) in septic shock and to explore their therapeutic potential. LPS- and tumor necrosis factor (TNF)-induced lethal shock, and cecal ligation and puncture (CLP) were performed in genetically or pharmacologically targeted mice. Body temperature and survival were monitored closely, and plasma was analyzed for several markers of cellular disintegration and inflammation. Interestingly, deficiency of both IL-1β and IL-18 additively prevented LPS-induced mortality. The detrimental role of IL-1β and IL-18 was confirmed in mice subjected to a lethal dose of TNF, or to a lethal CLP procedure. Although their upstream activator, CASP1, and its amplifier, CASP11, are considered potential therapeutic targets because of their crucial involvement in endotoxin-induced toxicity, CASP11- or CASP1/11-deficient mice were not, or hardly, protected against a lethal TNF or CLP challenge. In line with our results obtained in genetically deficient mice, only the combined neutralization of IL-1 and IL-18, using the IL-1 receptor antagonist anakinra and anti-IL-18 antibodies, conferred complete protection against endotoxin-induced lethality. Our data point toward the therapeutic potential of neutralizing IL-1 and IL-18 simultaneously in sepsis, rather than inhibiting the upstream inflammatory caspases.

Background The activation of the immune system in neurodegeneration has detrimental as well as beneficial effects. Which aspects of this immune response aggravate the neurodegenerative breakdown and which stimulate regeneration remains an open question. To unravel the neuroprotective aspects of the immune system we focused on a model of acute peripheral nerve injury, in which the immune system was shown to be protective. Methods To determine the type of immune response triggered after axotomy of the sciatic nerve, a model for Wallerian degeneration in the peripheral nervous system, we evaluated markers representing the two extremes of a type I and type II immune response (classical vs. alternative) using real-time quantitative polymerase chain reaction (RT-qPCR), western blot, and immunohistochemistry. Results Our results showed that acute peripheral nerve injury triggers an anti-inflammatory and immunosuppressive response, rather than a pro-inflammatory response. This was reflected by the complete absence of classical macrophage markers (iNOS, IFNγ, and IL12p40), and the strong up-regulation of tissue repair markers (arginase-1, Ym1, and Trem2). The signal favoring the alternative macrophage environment was induced immediately after nerve damage and appeared to be established within the nerve, well before the infiltration of macrophages. In addition, negative regulators of the innate immune response, as well as the anti-inflammatory cytokine IL-10 were induced. The strict regulation of the immune system dampens the potential tissue damaging effects of an over-activated response. Conclusions We here demonstrate that acute peripheral nerve injury triggers an inherent protective environment by inducing the M2 phenotype of macrophages and the expression of arginase-1. We believe that the M2 phenotype, associated with a sterile inflammatory response and tissue repair, might explain their neuroprotective capacity. As such, shifting the neurodegeneration-induced immune responses towards an M2/Th2 response could be an important therapeutic strategy.

Despite major improvements in immunotherapeutic strategies, the immunosuppressive tumor microenvironment remains a major obstacle for the induction of efficient antitumor responses. In this study, we show that local delivery of a bispecific Clec9A-PD-L1 targeted type I interferon (AcTaferon, AFN) overcomes this hurdle by reshaping the tumor immune landscape. Treatment with the bispecific AFN resulted in the presence of pro-immunogenic tumor-associated macrophages and neutrophils, increased motility and maturation profile of cDC1 and presence of inflammatory cDC2. Moreover, we report empowered diversity in the CD8 + T cell repertoire and induction of a shift from naive, dysfunctional CD8 + T cells towards effector, plastic cytotoxic T lymphocytes together with increased presence of NK and NKT cells as well as decreased regulatory T cell levels. These dynamic changes were associated with potent antitumor activity. Tumor clearance and immunological memory, therapeutic immunity on large established tumors and blunted tumor growth at distant sites were obtained upon co-administration of a non-curative dose of chemotherapy. Overall, this study illuminates further application of type I interferon as a safe and efficient way to reshape the suppressive tumor microenvironment and induce potent antitumor immunity; features which are of major importance in overcoming the development of metastases and tumor cell resistance to immune attack. The strategy described here has potential for application across to a broad range of cancer types.

Systemic toxicities have severely limited the clinical application of tumor necrosis factor (TNF) as an anticancer agent. Activity‐on‐Target cytokines (AcTakines) are a novel class of immunocytokines with improved therapeutic index. A TNF‐based AcTakine targeted to CD13 enables selective activation of the tumor neovasculature without any detectable toxicity in vivo . Upregulation of adhesion markers supports enhanced T‐cell infiltration leading to control or elimination of solid tumors by, respectively, CAR T cells or a combination therapy with CD8‐targeted type I interferon AcTakine. Co‐treatment with a CD13‐targeted type II interferon AcTakine leads to very rapid destruction of the tumor neovasculature and complete regression of large, established tumors. As no tumor markers are needed, safe and efficacious elimination of a broad range of tumor types becomes feasible. Synopsis TNF and IFN‐γ are cytokines with great anticancer potential but with limited clinical application due to side‐effects. In the present study, the tumor endothelium is identified as target cell for their antitumor activity and new biologics that allow their safe targeting are developed. By using transgenic mouse technologies the tumor endothelium was identified as target for the antitumor effect of TNF and IFN‐γ. TNF and IFN‐γ AcTakines were developed by fusing inactivated cytokine mutants to a CD13 single domain antibody (resp. CD13‐AFR and CD13‐AFN‐II), allowing selective targeting of cytokine activity to the tumor endothelium. CD13‐AFR synergized with immunotherapies (CD8‐AFN or CAR T‐cells) for immune‐mediated killing of solid tumors, without side‐effects. Combined treatment with CD13‐AFR and CD13‐AFN‐II resulted in selective apoptosis of the tumor endothelium and complete tumor destruction, without side‐effects. Graphical Abstract TNF and IFN‐γ are cytokines with great anticancer potential but with limited clinical application due to side‐effects. In the present study, the tumor endothelium is identified as target cell for their antitumor activity and new biologics that allow their safe targeting are developed.

Type I interferon (IFN) is a potent antitumoral drug, with an important history in the treatment of hematologic malignancies. However, its pleiotropic nature leads to severe dose-limiting toxicities that blunt its therapeutic potential. To achieve selective targeting of specific immune or tumor cells, AcTakines (Activity-on-Target Cytokines), i.e., immunocytokines utilizing attenuated cytokines, and clinically optimized A-Kines™ were developed. In syngeneic murine models, the CD20-targeted murine IFNα2-based AcTaferons (AFNs) have demonstrated clear antitumoral effects, with excellent tolerability. The current study explores the antitumoral potential of the humanized huCD20-Fc-AFN in 5 different humanized patient derived xenograft (PDX) models of huCD20 + aggressive B non-Hodgkin lymphomas (B-NHLs). The huCD20-Fc-AFN consists of a huCD20-specific single-domain antibody (VHH) linked through a heterodimeric ‘knob-in-hole’ human IgG1 Fc molecule to an attenuated huIFNα2 sequence. An in vitro targeting efficacy of up to 1.000-fold could be obtained, without detectable in vivo toxicities, except for selective (on-target) and reversible B cell depletion. Treatment with huCD20-Fc-AFN significantly increased the median overall survival (mOS) in both non-humanized (mOS 31 to 45 days; HR = 0.26; p = 0.001), and humanized NSG/NOG mice (mOS 34 to 80 days; HR = 0.37; p < 0.0001). In humanized mice, there was a trend for increased survival when compared to equimolar rituximab (mOS 49 to 80 days; HR = 0.73; p = 0.09). The antitumoral effects of huCD20-Fc-AFN were partly due to direct effects of type I IFN on the tumor cells, but additional effects via the human immune system are essential to obtain long-term remissions. To conclude, huCD20-Fc-AFN could provide a novel therapeutic strategy for huCD20-expressing aggressive B-NHLs. Graphical Abstract Key points The A-Kine™-principle allows for up to 1.000-fold targeting efficacy, enabling reduced toxicities of IFNα2-based therapies. huCD20-Fc-AFN demonstrates significant antitumoral efficacy in 5 humanized PDX models of aggressive huCD20 + B-NHLs.

BackgroundClinical success of therapeutic cancer vaccines depends on the ability to mount strong and durable antitumor T cell responses. To achieve this, potent cellular adjuvants are highly needed. Interleukin-1β (IL-1β) acts on CD8+ T cells and promotes their expansion and effector differentiation, but toxicity and undesired tumor-promoting side effects hamper efficient clinical application of this cytokine.MethodsThis ‘cytokine problem’ can be solved by use of AcTakines (Activity-on-Target cytokines), which represent fusions between low-activity cytokine mutants and cell type-specific single-domain antibodies. AcTakines deliver cytokine activity to a priori selected cell types and as such evade toxicity and unwanted off-target side effects. Here, we employ subcutaneous melanoma and lung carcinoma models to evaluate the antitumor effects of AcTakines.ResultsIn this work, we use an IL-1β-based AcTakine to drive proliferation and effector functionality of antitumor CD8+ T cells without inducing measurable toxicity. AcTakine treatment enhances diversity of the T cell receptor repertoire and empowers adoptive T cell transfer. Combination treatment with a neovasculature-targeted tumor necrosis factor (TNF) AcTakine mediates full tumor eradication and establishes immunological memory that protects against secondary tumor challenge. Interferon-γ was found to empower this AcTakine synergy by sensitizing the tumor microenvironment to TNF.ConclusionsOur data illustrate that anticancer cellular immunity can be safely promoted with an IL-1β-based AcTakine, which synergizes with other immunotherapies for efficient tumor destruction.

BackgroundHigh dose IL-2 therapy induces complete and durable responses in a small subset of patients with metastatic melanoma and renal cell carcinoma. Severe toxicity, including capillary leak syndrome, limits its therapeutic use and requires inpatient treatment at specialized centers. High dose IL-2 therapy induces activation of regulatory T cells (Tregs), potentially limiting its efficacy. IL-2 variants engineered to avoid the high affinity IL-2 receptor on Tregs, and other cells involved in systemic toxicity, are in advanced clinical trials. However, monotherapy efficacy has been reported only in small numbers of patients. Other approaches limit the activity of IL-2 to the tumor microenvironment, ignoring the opportunity to directly stimulate immune responses in secondary lymphoid organs. We engineered a conditionally active IL-2 variant (A-Kine) that requires targeting to specific receptors expressed on selected immune cells. Herein, we evaluate the activity of IL-2 A-Kines targeted to CD8+ T cells (CD8-ALN2) in syngeneic and humanized mouse tumor models.MethodsMice were subcutaneously inoculated with MC38 or CT26 tumor cells. Once tumor growth was established, mice were treated with mouse CD8-ALN2 (mCD8-ALN2), untargeted-ALN2, or vehicle. CD34+ humanized NSG mice were subcutaneously inoculated with RL lymphoma or MDA-MB-231 breast tumor cells. Once tumor growth was established, mice were treated with human CD8-ALN2 (hCD8-ALN2), untargeted-ALN2, or vehicle. Tumor growth was measured, and tissues were analyzed by flow cytometry.ResultsmCD8-ALN2 treatment induced significant MC38 tumor growth inhibition and up to 80% complete responses (CRs), while tumors in mice treated with untargeted-ALN2 grew as rapidly as vehicle-treated controls. CD8 T cell activation and expansion was observed in blood, spleen, and tumors following mCD8-ALN2 treatment, but not in response to untargeted-ALN2. Immune-depletion studies demonstrate a critical role for CD8+ but not CD4+ T cells. mCD8-ALN2 treatment also resulted in CRs in the CT26 colon carcinoma model, and inhibited tumor growth in B16 melanoma and Panc carcinoma models. Tumor growth inhibition was also observed in CD34+ humanized mice implanted with RL lymphoma or MDA-MB-231 breast tumors following hCD8-ALN2 treatment but not in mice treated with untargeted-ALN2. Consistent with antitumor efficacy, CD8 T cell activation and expansion was observed in the blood of hCD8-ALN2 treated mice.ConclusionsSelective stimulation of CD8 T cells with conditionally active CD8-ALN2 resulted in significant antitumor efficacy in syngeneic and humanized mouse tumor models. These data warrant the further development of hCD8-ALN2 for cancer immunotherapy.Ethics ApprovalAll animal experiments followed the Federation of European Laboratory Animal Science Association guidelines and were approved by the Ethical Committee of Ghent University. Approval numbers: ECD 20–40 and ECD 18/40.