The commensal skin microbiota triggers type I IFN-dependent innate repair responses in injured skin.

Skin wounds heal by coordinated induction of inflammation and tissue repair, but the initiating events are poorly defined. Here we uncover a fundamental role of commensal skin microbiota in this process and show that it is mediated by the recruitment and the activation of type I interferon (IFN)-producing plasmacytoid DC (pDC). Commensal bacteria colonizing skin wounds trigger activation of neutrophils to express the chemokine CXCL10, which recruits pDC and acts as an antimicrobial protein to kill exposed microbiota, leading to the formation of CXCL10-bacterial DNA complexes. These complexes and not complexes with host-derived DNA activate pDC to produce type I IFNs, which accelerate wound closure by triggering skin inflammation and early T cell-independent wound repair responses, mediated by macrophages and fibroblasts that produce major growth factors required for healing. These findings identify a key function of commensal microbiota in driving a central innate wound healing response of the skin.

Association of COVID-19 inflammation with activation of the C5a-C5aR1 axis.

Coronavirus disease 2019 (COVID-19) is a disease caused by infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and has resulted in a pandemic1. The C5a complement factor and its receptor C5aR1 (also known as CD88) have a key role in the initiation and maintenance of several inflammatory responses by recruiting and activating neutrophils and monocytes1. Here we provide a longitudinal analysis of immune responses, including phenotypic analyses of immune cells and assessments of the soluble factors that are present in the blood and bronchoalveolar lavage fluid of patients at various stages of COVID-19 severity, including those who were paucisymptomatic or had pneumonia or acute respiratory distress syndrome. The levels of soluble C5a were increased in proportion to the severity of COVID-19 and high expression levels of C5aR1 receptors were found in blood and pulmonary myeloid cells, which supports a role for the C5a-C5aR1 axis in the pathophysiology of acute respiratory distress syndrome. Anti-C5aR1 therapeutic monoclonal antibodies prevented the C5a-mediated recruitment and activation of human myeloid cells, and inhibited acute lung injury in human C5aR1 knock-in mice. These results suggest that blockade of the C5a-C5aR1 axis could be used to limit the infiltration of myeloid cells in damaged organs and prevent the excessive lung inflammation and endothelialitis that are associated with acute respiratory distress syndrome in patients with COVID-19.

Publisher Correction: Harnessing innate immunity in cancer therapy.

An Amendment to this paper has been published and can be accessed via a link at the top of the paper.

Harnessing innate immunity in cancer therapy.

New therapies that promote antitumour immunity have been recently developed. Most of these immunomodulatory approaches have focused on enhancing T-cell responses, either by targeting inhibitory pathways with immune checkpoint inhibitors, or by targeting activating pathways, as with chimeric antigen receptor T cells or bispecific antibodies. Although these therapies have led to unprecedented successes, only a minority of patients with cancer benefit from these treatments, highlighting the need to identify new cells and molecules that could be exploited in the next generation of immunotherapy. Given the crucial role of innate immune responses in immunity, harnessing these responses opens up new possibilities for long-lasting, multilayered tumour control.

Homeostatic NF-κB Signaling in Steady-State Migratory Dendritic Cells Regulates Immune Homeostasis and Tolerance.

Migratory non-lymphoid tissue dendritic cells (NLT-DCs) transport antigens to lymph nodes (LNs) and are required for protective immune responses in the context of inflammation and to promote tolerance to self-antigens in steady-state. However, the molecular mechanisms that elicit steady-state NLT-DC maturation and migration are unknown. By comparing the transcriptome of NLT-DCs in the skin with their migratory counterparts in draining LNs, we have identified a novel NF-κB-regulated gene network specific to migratory DCs. We show that targeted deletion of IKKß in DCs, a major activator of NF-κB, prevents NLT-DC accumulation in LNs and compromises regulatory T cell conversion in vivo. This was associated with impaired tolerance and autoimmunity. NF-κB is generally considered the prototypical pro-inflammatory transcription factor, but this study describes a role for NF-κB signaling in DCs for immune homeostasis and tolerance that could have implications in autoimmune diseases and immunity.

Natural killer cell engagers in cancer immunotherapy: Next generation of immuno-oncology treatments.

Immuno-oncology is revolutionizing the treatment of cancers, by inducing the recognition and elimination of tumor cells by the immune system. Recent advances have focused on generating or unleashing tumor antigen-specific T-cell responses, leading to alternative treatment paradigms for many cancers. Despite these successes, the clinical benefit has been limited to a subset of patients and certain tumor types, highlighting the need for alternative strategies. One innovative approach is to broaden and amplify antitumoral immune responses by targeting innate immunity. Particularly, the aim has been to develop new antibody formats capable of stimulating the antitumor activity of innate immune cells, boosting not only their direct role in tumor elimination, but also their function in eliciting multicellular immune responses ultimately resulting in long-lasting tumor control by adaptive immunity. This review covers the development of a new class of synthetic molecules, natural killer cell engagers (NKCEs), which are built from fragments of monoclonal antibodies (mAbs) and are designed to harness the immune functions of NK cells in cancer. As currently shown in preclinical studies and clinical trials, NKCEs are promising candidates for the next generation of tumor immunotherapies.

Avdoralimab (Anti-C5aR1 mAb) Versus Placebo in Patients With Severe COVID-19: Results From a Randomized Controlled Trial (FOR COVID Elimination [FORCE]).

OBJECTIVES: Severe COVID-19 is associated with exaggerated complement activation. We assessed the efficacy and safety of avdoralimab (an anti-C5aR1 mAb) in severe COVID-19. DESIGN: FOR COVID Elimination (FORCE) was a double-blind, placebo-controlled study. SETTING: Twelve clinical sites in France (ICU and general hospitals). PATIENTS: Patients receiving greater than or equal to 5 L oxygen/min to maintain Sp o2 greater than 93% (World Health Organization scale ≥ 5). Patients received conventional oxygen therapy or high-flow oxygen (HFO)/noninvasive ventilation (NIV) in cohort 1; HFO, NIV, or invasive mechanical ventilation (IMV) in cohort 2; and IMV in cohort 3. INTERVENTIONS: Patients were randomly assigned, in a 1:1 ratio, to receive avdoralimab or placebo. The primary outcome was clinical status on the World Health Organization ordinal scale at days 14 and 28 for cohorts 1 and 3, and the number of ventilator-free days at day 28 (VFD28) for cohort 2. MEASUREMENTS AND MAIN RESULTS: We randomized 207 patients: 99 in cohort 1, 49 in cohort 2, and 59 in cohort 3. During hospitalization, 95% of patients received glucocorticoids. Avdoralimab did not improve World Health Organization clinical scale score on days 14 and 28 (between-group difference on day 28 of -0.26 (95% CI, -1.2 to 0.7; p = 0.7) in cohort 1 and -0.28 (95% CI, -1.8 to 1.2; p = 0.6) in cohort 3). Avdoralimab did not improve VFD28 in cohort 2 (between-group difference of -6.3 (95% CI, -13.2 to 0.7; p = 0.96) or secondary outcomes in any cohort. No subgroup of interest was identified. CONCLUSIONS: In this randomized trial in hospitalized patients with severe COVID-19 pneumonia, avdoralimab did not significantly improve clinical status at days 14 and 28 (funded by Innate Pharma, ClinicalTrials.gov number, NCT04371367).

Netting Neutrophils Activate Autoreactive B Cells in Lupus.

Lupus erythematosus (LE) patients develop autoantibodies that form circulating immune complexes (ICs) with extracellular self-nucleic acids. These ICs are deposited into peripheral tissues, where they trigger detrimental organ inflammation. Recent evidence suggests that ICs contain LL37-DNA complexes derived from neutrophil extracellular traps (NETs) and that LE patients develop pathogenic autoantibodies against these structures, including Abs to LL37. However, the mechanism that leads to the generation of these Abs is unknown. In this study, we show that NETs directly trigger Ab production by human memory B cells. This occurs via LL37-DNA complexes present in NETs, which have the unique ability to gain access to endosomal compartments of B cells and to trigger TLR9 activation. In LE patients, NET-derived LL37-DNA complexes trigger polyclonal B cell activation via TLR9, but also specifically expand self-reactive memory B cells producing anti-LL37 Abs in an Ag-dependent manner. These findings suggest a unique link between neutrophils and B cells in which NETs trigger a concerted activation of TLR9 and BCR leading to anti-NET autoantibody production in lupus.

Impairment of both IRE1 expression and XBP1 activation is a hallmark of GCB DLBCL and contributes to tumor growth.

The endoplasmic reticulum kinase inositol-requiring enzyme 1 (IRE1) and its downstream target X-box-binding protein 1 (XBP1) drive B-cell differentiation toward plasma cells and have been shown to contribute to multiple myeloma development; yet, little is known of the role of this pathway in diffuse large B-cell lymphoma (DLBCL). Here, we show that in the germinal center B-cell-like (GCB) DLBCL subtype, IRE1 expression is reduced to a level that prevents XBP1 activation. Gene expression profiles indicated that, in GCB DLBCL cancer samples, expression of IRE1 messenger RNA was inversely correlated with the levels and activity of the epigenetic repressor, histone methyltransferase enhancer of zeste homolog 2 (EZH2). Correspondingly, in GCB-derived cell lines, the IRE1 promoter carried increased levels of the repressive epigenetic mark histone 3 lysine 27 trimethylation. Pharmacological inhibition of EZH2 erased those marks and restored IRE1 expression and function in vitro and in vivo. Moreover, reconstitution of the IRE1-signaling pathway, by expression of the XBP1-active form, compromised GCB DLBCL tumor growth in a mouse xenograft cancer model. These findings indicate that IRE1-XBP1 downregulation distinguishes GCB DLBCL from other DLBCL subtypes and contributes to tumor growth.

Drug Repurposing Approach Identifies a Synergistic Drug Combination of an Antifungal Agent and an Experimental Organometallic Drug for Melanoma Treatment.

By screening a drug library comprising FDA approved compounds, we discovered a potent interaction between the antifungal agent haloprogin and the experimental organometallic drug RAPTA-T, to synergistically induce cancer cell killing. The combination of these two small molecules, even at low doses, elicited an improved therapeutic response on tumor growth over either agent alone or the current treatment used in the clinic in the highly aggressive syngeneic B16F10 melanoma tumor model, where classical cytotoxic chemotherapeutic agents show little efficacy. The combination with the repurposed chemodrug haloprogin provides the basis for a new powerful treatment option for cutaneous melanoma. Importantly, because synergistic induction of tumor cell death is achieved with low individual drug doses, and cellular targets for RAPTA-T are different from those of classical chemotherapeutic drugs, a therapeutic strategy based on this approach could avoid toxicities and potentially resistance mechanisms, and could even inhibit metastatic progression.

Pharmacological eEF2K activation promotes cell death and inhibits cancer progression.

Activation of the elongation factor 2 kinase (eEF2K) leads to the phosphorylation and inhibition of the elongation factor eEF2, reducing mRNA translation rates. Emerging evidence indicates that the regulation of factors involved in protein synthesis may be critical for controlling diverse biological processes including cancer progression. Here we show that inhibitors of the HIV aspartyl protease (HIV-PIs), nelfinavir in particular, trigger a robust activation of eEF2K leading to the phosphorylation of eEF2. Beyond its anti-viral effects, nelfinavir has antitumoral activity and promotes cell death. We show that nelfinavir-resistant cells specifically evade eEF2 inhibition. Decreased cell viability induced by nelfinavir is impaired in cells lacking eEF2K. Moreover, nelfinavir-mediated anti-tumoral activity is severely compromised in eEF2K-deficient engrafted tumors in vivo Our findings imply that exacerbated activation of eEF2K is detrimental for tumor survival and describe a mechanism explaining the anti-tumoral properties of HIV-PIs.

STING activation of tumor endothelial cells initiates spontaneous and therapeutic antitumor immunity.

Spontaneous CD8 T-cell responses occur in growing tumors but are usually poorly effective. Understanding the molecular and cellular mechanisms that drive these responses is of major interest as they could be exploited to generate a more efficacious antitumor immunity. As such, stimulator of IFN genes (STING), an adaptor molecule involved in cytosolic DNA sensing, is required for the induction of antitumor CD8 T responses in mouse models of cancer. Here, we find that enforced activation of STING by intratumoral injection of cyclic dinucleotide GMP-AMP (cGAMP), potently enhanced antitumor CD8 T responses leading to growth control of injected and contralateral tumors in mouse models of melanoma and colon cancer. The ability of cGAMP to trigger antitumor immunity was further enhanced by the blockade of both PD1 and CTLA4. The STING-dependent antitumor immunity, either induced spontaneously in growing tumors or induced by intratumoral cGAMP injection was dependent on type I IFNs produced in the tumor microenvironment. In response to cGAMP injection, both in the mouse melanoma model and an ex vivo model of cultured human melanoma explants, the principal source of type I IFN was not dendritic cells, but instead endothelial cells. Similarly, endothelial cells but not dendritic cells were found to be the principal source of spontaneously induced type I IFNs in growing tumors. These data identify an unexpected role of the tumor vasculature in the initiation of CD8 T-cell antitumor immunity and demonstrate that tumor endothelial cells can be targeted for immunotherapy of melanoma.

TLR8 on dendritic cells and TLR9 on B cells restrain TLR7-mediated spontaneous autoimmunity in C57BL/6 mice.

Systemic lupus erythematosus (SLE) is a complex autoimmune disease with diverse clinical presentations characterized by the presence of autoantibodies to nuclear components. Toll-like receptor (TLR)7, TLR8, and TLR9 sense microbial or endogenous nucleic acids and are implicated in the development of SLE. In mice TLR7-deficiency ameliorates SLE, but TLR8- or TLR9-deficiency exacerbates the disease because of increased TLR7 response. Thus, both TLR8 and TLR9 control TLR7 function, but whether TLR8 and TLR9 act in parallel or in series in the same or different cell types in controlling TLR7-mediated lupus remains unknown. Here, we reveal that double TLR8/9-deficient (TLR8/9(-/-)) mice on the C57BL/6 background showed increased abnormalities characteristic of SLE, including splenomegaly, autoantibody production, frequencies of marginal zone and B1 B cells, and renal pathology compared with single TLR8(-/-) or TLR9(-/-) mice. On the cellular level, TLR8(-/-) and TLR8/9(-/-) dendritic cells were hyperesponsive to TLR7 ligand R848, but TLR9(-/-) cells responded normally. Moreover, B cells from TLR9(-/-) and TLR8/9(-/-) mice were hyperesponsive to R848, but TLR8(-/-) B cells were not. These results reveal that TLR8 and TLR9 have an additive effect on controlling TLR7 function and TLR7-mediated lupus; however, they act on different cell types. TLR8 controls TLR7 function on dendritic cells, and TLR9 restrains TLR7 response on B cells.

IL-17 receptor A and adenosine deaminase 2 deficiency in siblings with recurrent infections and chronic inflammation.

BACKGROUND: Data on patients affected by chronic mucocutaneous candidiasis underscore the preponderant role of IL-17 receptor A (IL-17RA) in preserving mucocutaneous immunity. Little is known about the role of adenosine deaminase (ADA) 2 in regulation of immune responses, although recent reports linked ADA2 deficiency with inflammation and vasculitis. OBJECTIVE: We sought to investigate the mechanisms of chronic inflammation and vasculitis in a child lacking IL-17RA and ADA2 to identify therapeutic targets. METHODS: We report a family with 2 siblings who have had recurrent mucocutaneous infections with Candida albicans and Staphylococcus aureus and chronic inflammatory disease and vasculitis since early childhood, which were refractory to classical treatments. Array-based comparative genomic hybridization analysis showed that both siblings are homozygous for a 770-kb deletion on chr22q11.1 encompassing both IL17RA and cat eye critical region 1 (CECR1). Immunologic studies were carried out by means of flow cytometry, ELISA, and RIA. RESULTS: As expected, in the affected child we found a lack of IL-17RA expression, which implies a severe malfunction in the IL-17 signaling pathway, conferring susceptibility to recurrent mucocutaneous infections. Surprisingly, we detected an in vitro and in vivo upregulation of proinflammatory cytokines, notably IL-1ß and TNF-α, which is consistent with the persistent systemic inflammation. CONCLUSIONS: This work emphasizes the utility of whole-genome analyses combined with immunologic investigation in patients with unresolved immunodeficiency. This approach is likely to provide an insight into immunologic pathways and mechanisms of disease. It also provides molecular evidence for more targeted therapies. In addition, our report further corroborates a potential role of ADA2 in modulating immunity and inflammation.

Cationic antimicrobial peptides in psoriatic skin cooperate to break innate tolerance to self-DNA.

Psoriasis is a T-cell-mediated skin autoimmune disease characterized by the aberrant activation of dermal dendritic cells (DCs) and the sustained epidermal expression of antimicrobial peptides. We have previously identified a link between these two events by showing that the cathelicidin antimicrobial peptide LL37 has the ability to trigger self-nucleic acid mediated activation of plasmacytoid DCs (pDCs) in psoriatic skin. Whether other cationic antimicrobial peptides exert similar activities is unknown. By analyzing heparin-binding HPLC fractions of psoriatic scales, we found that human beta-defensin (hBD)2, hBD3, and lysozyme are additional triggers of pDC activation in psoriatic skin lesions. Like LL37, hBD2, hBD3, and lysozyme are able to condense self-DNA into particles that are endocytosed by pDCs, leading to activation of TLR9. In contrast, other antimicrobial peptides expressed in psoriatic skin including elafin, hBD1, and psoriasin (S100A7) did not show similar activities. hBD2, hBD3, and lysozyme were detected in psoriatic skin lesions in the vicinity of pDCs and found to cooperate with LL37 to induce high levels of IFN production by pDCs, suggesting their concerted role in the pathogenesis of psoriasis.

New immune cell engagers for cancer immunotherapy.

There have been major advances in the immunotherapy of cancer in recent years, including the development of T cell engagers - antibodies engineered to redirect T cells to recognize and kill cancer cells - for the treatment of haematological malignancies. However, the field still faces several challenges to develop agents that are consistently effective in a majority of patients and cancer types, such as optimizing drug dose, overcoming treatment resistance and improving efficacy in solid tumours. A new generation of T cell-targeted molecules was developed to tackle these issues that are potentially more effective and safer. In addition, agents designed to engage the antitumour activities of other immune cells, including natural killer cells and myeloid cells, are showing promise and have the potential to treat a broader range of cancers.

Type I IFNs link skin-associated dysbiotic commensal bacteria to pathogenic inflammation and angiogenesis in rosacea.

Rosacea is a common chronic inflammatory skin disease with a fluctuating course of excessive inflammation and apparent neovascularization. Microbial dysbiosis with a high density of Bacillus oleronius and increased activity of kallikrein 5, which cleaves cathelicidin antimicrobial peptide, are key pathogenic triggers in rosacea. However, how these events are linked to the disease remains unknown. Here, we show that type I IFNs produced by plasmacytoid DCs represent the pivotal link between dysbiosis, the aberrant immune response, and neovascularization. Compared with other commensal bacteria, B. oleronius is highly susceptible and preferentially killed by cathelicidin antimicrobial peptides, leading to enhanced generation of complexes with bacterial DNA. These bacterial DNA complexes but not DNA complexes derived from host cells are required for cathelicidin-induced activation of plasmacytoid DCs and type I IFN production. Moreover, kallikrein 5 cleaves cathelicidin into peptides with heightened DNA binding and type I IFN-inducing capacities. In turn, excessive type I IFN expression drives neoangiogenesis via IL-22 induction and upregulation of the IL-22 receptor on endothelial cells. These findings unravel a potentially novel pathomechanism that directly links hallmarks of rosacea to the killing of dysbiotic commensal bacteria with induction of a pathogenic type I IFN-driven and IL-22-mediated angiogenesis.

TLR3 and Rig-like receptor on myeloid dendritic cells and Rig-like receptor on human NK cells are both mandatory for production of IFN-gamma in response to double-stranded RNA.

Cross-talk between NK cells and dendritic cells (DCs) is critical for the potent therapeutic response to dsRNA, but the receptors involved remained controversial. We show in this paper that two dsRNAs, polyadenylic-polyuridylic acid and polyinosinic-polycytidylic acid [poly(I:C)], similarly engaged human TLR3, whereas only poly(I:C) triggered human RIG-I and MDA5. Both dsRNA enhanced NK cell activation within PBMCs but only poly(I:C) induced IFN-gamma. Although myeloid DCs (mDCs) were required for NK cell activation, induction of cytolytic potential and IFN-gamma production did not require contact with mDCs but was dependent on type I IFN and IL-12, respectively. Poly(I:C) but not polyadenylic-polyuridylic acid synergized with mDC-derived IL-12 for IFN-gamma production by acting directly on NK cells. Finally, the requirement of both TLR3 and Rig-like receptor (RLR) on mDCs and RLRs but not TLR3 on NK cells for IFN-gamma production was demonstrated using TLR3- and Cardif-deficient mice and human RIG-I-specific activator. Thus, we report the requirement of cotriggering TLR3 and RLR on mDCs and RLRs on NK cells for a pathogen product to induce potent innate cell activation.

[Toll-like receptor 8: the awkward TLR]. / Le récepteur Toll-like 8 - Un TLR pas comme les autres.

Toll-like receptors (TLR) sense a variety of microbial products and play an important role in the mounting of innate and adaptive immune responses. TLR1 to TLR9 are common in mice and humans and recognize similar ligands in both species, with the exception of TLR8. Human TLR7 and TLR8 and mouse TLR7 detect viral single-stranded RNA and imidazoquinoline compounds, while mouse TLR8 not. Based on this discrepancy, for long time it was believed that mouse TLR8 is not functional and as a consequence the contribution of TLR8 to innate immunity remained poorly understood. Our recent studies revealed an important role for TLR8 in the regulation of TLR7-mediated autoimmunity in the mouse. This review illustrates our current understanding regarding the function of TLR8 and its potential for future clinical use for the treatment and/or prevention of various pathological conditions.

Antitumor immunity induced by antibody-based natural killer cell engager therapeutics armed with not-alpha IL-2 variant.

Harnessing innate immunity is emerging as a promising therapeutic approach in cancer. We report here the design of tetraspecific molecules engaging natural killer (NK) cell-activating receptors NKp46 and CD16a, the ß-chain of the interleukin-2 receptor (IL-2R), and a tumor-associated antigen (TAA). In vitro, these tetraspecific antibody-based natural killer cell engager therapeutics (ANKETs) induce a preferential activation and proliferation of NK cells, and the binding to the targeted TAA triggers NK cell cytotoxicity and cytokine and chemokine production. In vivo, tetraspecific ANKETs induce NK cell proliferation and their accumulation at the tumor bed, as well as the control of local and disseminated tumors. Treatment of non-human primates with CD20-directed tetraspecific ANKET leads to CD20+ circulating B cell depletion, with minimal systemic cytokine release and no sign of toxicity. Tetraspecific ANKETs, thus, constitute a technological platform for harnessing NK cells as next-generation cancer immunotherapies.