Activated STING in a vascular and pulmonary syndrome

Sensing of dangerous DNA

The presence of damaged and microbial DNA can pose a threat to the survival of organisms. Cells express various sensors that recognize specific aspects of such potentially dangerous DNA. Recognition of damaged or microbial DNA by sensors induces cellular processes that are important for DNA repair and inflammation. Here, we review recent evidence that the cellular response to DNA damage and microbial DNA are tightly intertwined. We also discuss insights into the parameters that enable DNA sensors to distinguish damaged and microbial DNA from DNA present in healthy cells.

Immunotherapeutic Biologic Agents in Autoimmune and Autoinflammatory Diseases

In recent decades, innovative strategies to treat patients with inflammatory, immunologically based diseases have advanced in concert with our increased understanding of molecular immunology. Recognition of the spectrum and pathophysiology of autoimmune and autoinflammatory disorders has allowed for the development of cutting-edge therapies for such patients. In this review, key immunotherapeutic approaches for treating inflammatory autoimmune disorders, such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), as well as genetic autoinflammatory diseases, such as cryopyrin associated periodic syndromes, are addressed. Indications, risks and additional considerations in the use of these agents are reviewed.

Exploring Autoimmunity in a Cohort of Children with Genetically Confirmed Aicardi-Goutières Syndrome

PURPOSE

The purpose of this study was to explore the presence of autoimmune manifestations and characterize the autoantibody production in a cohort of patients with Aicardi-Goutières syndrome (AGS).

METHODS

Seventeen patients with a genetically-confirmed diagnosis of AGS were recruited. At the time of enrollment, past medical and family history was reviewed, looking for possible signs or symptoms of autoimmune disorders. Blood samples were taken, for the detection of a panel of autoantibodies: anti-nuclear, anti-double-stranded-DNA, anti-nucleosome, anti-extractable nuclear antigens, anti-cardiolipin IgG/IgM, anti-β2glycoprotein I IgG/IgM, and anti-neutrophil cytoplasmic. We also measured complement levels determined as C3 and C4 quantification and total complement activity, measured as CH50.

RESULTS

Nine of seventeen patients presented with at least one first- or second-degree relative with a history of autoimmune diseases (the childrens' mother or grand-mother in the majority of cases). A specific autoimmune disease was present in only one AGS patient, namely an autoimmune thyroiditis. Autoantibodies were present in 9/17 patients, with different patterns of positivity. Complement levels were normal in all the patients. There was no correlation between auto-antibody production and personal or family history of autoimmune diseases.

CONCLUSIONS

Definite autoimmune diseases are not common in patients with AGS. Autoantibodies are mainly directed towards nucleic acids-containing elements but seem not to be pathogenic and, rather, may represent an epiphenomenon of the enhanced interferon production.

Taking the STING out of TLR-driven autoimmune diseases: good, bad, or indifferent?

Both endosomal and cytosolic-nucleic acid-sensing receptors can detect endogenous ligands and promote autoimmunity and autoinflammation. These responses involve a complex interplay among and between the cytosolic and endosomal sensors involving both hematopoietic and radioresistant cells. Cytosolic sensors directly promote inflammatory responses through the production of type I IFNs and proinflammatory cytokines. Inflammation-associated tissue damage can further promote autoimmune responses indirectly, as receptor-mediated internalization of the resulting cell debris can activate endosomal Toll-like receptors (TLR). Both endosomal and cytosolic receptors can also negatively regulate inflammatory responses. A better understanding of the factors and pathways that promote and constrain autoimmune diseases will have important implications for the development of agonists and antagonists that modulate these pathways.

The autoimmune conundrum in common variable immunodeficiency disorders

PURPOSE OF REVIEW

Autoimmune and inflammatory manifestations are the biggest clinical challenge in the care of patients with common variable immunodeficiency (CVID). The increasing pathogenic knowledge and potential therapeutic implications require a new evaluation of the status quo. (Figure is included in full-text article.)

RECENT FINDINGS

The conundrum of the simultaneous manifestation of primary immunodeficiency and autoimmune disease (AID) is increasingly elucidated by newly discovered genetic defects. Thus, cytotoxic T lymphocyte-associated antigen 4 or caspase-9 deficiency presenting with CVID-like phenotypes reiterate concepts of immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome and autoimmune lymphoproliferative syndrome. Activating signaling defects downstream of antigen or cytokine receptors are often associated with loss-of-tolerance in the affected patients. Increasingly, forms of combined immunodeficiency are discovered among CVID-like patients. Although different autoimmune manifestations often coincide in the same patient their immunopathology varies. Treatment of AID in CVID remains a challenge, but based on a better definition of the immunopathology first attempts of targeted treatment have been made.

SUMMARY

The increasing comprehension of immunological concepts promoting AID in CVID will allow better and in some cases possibly even targeted treatment. A genetic diagnosis therefore becomes important information in this group of patients, especially in light of the fact that some patients might require hematopoietic stem cell transplantation because of their underlying immunodeficiency.

Brief Report: First Identification of Intrafamilial Recurrence of Blau Syndrome due to Gonosomal NOD2 Mosaicism

OBJECTIVE

Blau syndrome is characterized by noncaseating granulomatous arthritis, dermatitis, and uveitis, and results from gain-of-function NOD2 mutations. This study was undertaken to identify the genetic cause of the disease in a family with 3 members with Blau syndrome.

METHODS

We studied a family with 3 affected members across 2 consecutive generations. The children's symptoms started early (at 6 and 7 months of age) and included polyarthritis, dermatitis, uveitis, and fever. In contrast, the father's symptoms started later (at 22 years of age) and included noncaseating granulomatous dermatitis and uveitis. We analyzed the NOD2 gene in all patients by both the Sanger method of DNA sequencing and amplicon-based deep sequencing using an Ion Torrent PGM platform.

RESULTS

Sanger chromatograms revealed the heterozygous c.1001G>A transition in both children, which resulted in the p.Arg334Gln mutation that causes Blau syndrome. In contrast, the father's chromatograms revealed a small peak of adenine at the c.1001 position, suggesting the presence of a somatic NOD2 mutation. To evaluate this hypothesis, we performed amplicon-based deep sequencing using DNA from different tissues, which confirmed a variable degree (0.9-12.9%) of somatic NOD2 mosaicism. The previous detection of the NOD2 mutation in his daughters strongly suggests the presence of gonosomal (somatic plus gonadal) NOD2 mosaicism in the father. Comparative analyses with Blau syndrome patients carrying the germline p.Arg334Gln NOD2 mutation revealed late onset of the disease, a mild inflammatory phenotype, and an absence of complications in patients with NOD2 mosaicism.

CONCLUSION

This is the first description of gonosomal NOD2 mosaicism as the cause of intrafamilial recurrence of Blau syndrome. Our findings also indicate that Blau syndrome includes more diverse and milder phenotypes than previously described.

The proteasome - victim or culprit in autoimmunity

The ubiquitin proteasome system is closely connected to apoptosis, autophagy, signaling of inflammatory cytokines and generation of ligands for MHC class I antigen presentation. Proteasome function in the innate immune response becomes particularly evident in patients with proteasome-associated autoinflammatory syndromes (PRAAS), where disease causing mutations result in reduced proteasome activity. PRAAS can be classified as a novel type of interferonopathy, however the molecular mechanism and signaling pathways leading from impaired proteasome capacity, the accumulation of damaged proteins, and the induction of type I IFN-genes remain to be determined. In contrast, several studies have confirmed an up-regulation of inducible subunits of the proteasome in systemic autoimmune diseases. Since proteasome inhibition was shown to be efficacious in several in-vitro studies and animal models of autoimmune diseases, it is justified to investigate the application of proteasome inhibitors in human disease. In this context, a number of available proteasome inhibitors has been characterized as potent immune-suppressants. The mode of action of proteasome inhibition interferes with the quality control of the huge amounts of synthetized antibodies causing an unfolded protein response. Further effects of proteasome inhibition includes inhibition of NFκB activation as well as direct activation of intrinsic and extrinsic pathways of apoptosis. The preliminary clinical work on proteasome inhibition in autoimmune diseases comprises only few studies in small cohorts with promising effects, which needs to be confirmed in controlled clinical trials.

Discriminating self from non-self in nucleic acid sensing

Immune sensing of foreign nucleic acids among abundant self nucleic acids is a hallmark of virus detection and antiviral defence.

Efficient antiviral defence requires a balanced process of sensing foreign nucleic acids and ignoring self nucleic acids. This balance is accomplished by a multilevel, fail-safe system which combines immune sensing of pathogen-specific nucleic acid structures with specific labelling of self nucleic acids and nuclease-mediated degradation.

Cellular localization of nucleic acids, nucleic acid secondary structure, nucleic acid sequence and chemical modification all contribute to selective recognition of foreign nucleic acids.

Nucleic acid sensing occurs in immune cells and non-immune cells and results in antiviral responses that include the induction of antiviral effector proteins, the secretion of cytokines alarming neighbouring cells, the secretion of chemokines, which attract immune cells, and the induction of cell death.

Vertebrate cells cannot completely avoid the occurrence of endogenous self nucleic acid structures with immunostimulatory properties. Therefore, additional mechanisms involving self-nucleic acid modification and nuclease-mediated degradation are necessary to diminish uncontrolled immune activation.

Viruses have established sophisticated mechanisms to exploit and adopt endogenous tolerance mechanisms or to avoid the presentation of characteristic molecular features recognized by nucleic acid sensing receptors.

The detection of viruses by the immune system is mediated predominantly by the sensing of nucleic acids. Here, the authors review our current understanding of how this complex immune sensory system discriminates self from non-self nucleic acids to reliably detect pathogenic viruses, and discuss the future perspectives and implications for human disease.

Innate immunity against pathogens relies on an array of immune receptors to detect molecular patterns that are characteristic of the pathogens, including receptors that are specialized in the detection of foreign nucleic acids. In vertebrates, nucleic acid sensing is the dominant antiviral defence pathway. Stimulation of nucleic acid receptors results in antiviral immune responses with the production of type I interferon (IFN), as well as the expression of IFN-stimulated genes, which encode molecules such as cell-autonomous antiviral effector proteins. This Review summarizes the tremendous progress that has been made in understanding how this sophisticated immune sensory system discriminates self from non-self nucleic acids in order to reliably detect pathogenic viruses.

The expanding regulatory network of STING-mediated signaling

The identification and characterization of DNA-sensing pathways has been a subject of intensive investigation for the last decade. This interest, in part, is supported by the fact that the main outcome of DNA-responses is production of type I interferon (IFN-I), which, if produced in excessive amounts, leads to various pathologies. STING (stimulator of interferon genes) is positioned in the center of these responses and is activated either via direct sensing of second messengers or via interaction with upstream sensors of dsDNA. STING mediates responses to pathogens as well as host-derived DNA and is, therefore, linked to various autoimmune diseases, cancer predisposition and ageing. Recent mouse models of DNA damage showed the adaptor STING to be crucial for heightened resting levels of IFN-I. In this review, we will focus on recent advances in understanding the regulation of STING-signaling and identification of its novel components.

Newly recognized Mendelian disorders with rheumatic manifestations

PURPOSE OF REVIEW

We review newly discovered monogenic immune-dysregulatory disorders that were reported in Pubmed over the last year.

RECENT FINDINGS

Fourteen novel monogenic immune-dysregulatory disorders that present with innate and acquired/adaptive immune dysregulation and inflammatory clinical phenotypes were identified. These include autosomal-dominant gain-of function mutations in viral innate immune sensors or their adaptors, TMEM173/STING IFIH1/MDA5 and DDX58/RIG-I that cause complex clinical syndromes distinct from IL-1-mediated diseases and present with a chronic type I interferon (IFN Type I) signature in peripheral blood. Gain-of-function mutations in NLRC4 add a novel inflammasome disorder associated with predisposition to macrophage-activation syndrome and highly elevated IL-18 levels. Mutations in ADA2, TRNT1 and COPA, AP1S3, and TNFRSF11A cause complex syndromes; loss-of-function mutations in enzymes and molecules are linked to the generation of 'cellular stress' and the release of inflammatory mediators that likely cause the inflammatory disease manifestations. A monogenic form of systemic-onset juvenile idiopathic arthritis is caused by homozygous mutations in LACC1. Lastly, mutations in PRKDC (recessive), STAT3, CTLA4, and PIK3R1 (all dominant) lead to impaired central and peripheral T-cell tolerance and present with variable disease manifestations of immunodeficiency and immune dysregulation/autoimmunity.

SUMMARY

A number of novel monogenic diseases that present with innate and/or acquired immune dysregulation reveal novel immune pathways that cause human inflammatory diseases and suggest potential novel targets for treatment.

Advances in lupus genetics

PURPOSE OF REVIEW

The field of systemic lupus erythematosus (SLE) genetics has been advancing rapidly in recent years. This review will summarize recent advances in SLE genetics.

RECENT FINDINGS

Genome-wide-association and follow-up studies have greatly expanded the list of associated polymorphisms, and much current work strives to integrate these polymorphisms into immune system biology and the pathogenic mediators involved in the disease. This review covers some current areas of interest, including genetic studies in non-European SLE patient populations, studies of pathogenic immune system subphenotypes such as type I interferon and autoantibodies, and a rapidly growing body of work investigating the functional consequences of the genetic polymorphisms associated with SLE.

SUMMARY

These studies provide a fascinating window into human SLE disease biology. As the work proceeds from genetic association signal to altered human biology, we move closer to tailoring interventions based upon an individual's genetic substrate.

Severe Early-Onset Combined Immunodeficiency due to Heterozygous Gain-of-Function Mutations in STAT1

PURPOSE

Loss and gain-of-function (GOF) mutations in human signal transducer and activator of transcription 1 (STAT1) lead to distinct phenotypes. Although recurrent infections are common to both types of STAT1 mutations, GOF mutations are distinguished by chronic mucocutaneous candidiasis and autoimmunity. However, the clinical spectra of STAT1 GOF mutations continue to expand. We here describe two patients with STAT1 GOF mutations presenting early in life with combined immunodeficiency (CID).

METHODS

Clinical data and laboratory findings including immunophenotyping, level of interferon (IFN)-γ/IL-17(+) T cells, interferon-induced STAT1 phosphorylation, and JAK inhibitor assays were evaluated. Sequencing of STAT1 gene was performed by Sanger sequencer.

RESULTS

Patient 1 (P1) had persistent oral candidiasis and cytomegalovirus (CMV) infection since 2 months of age and later developed cavitary lung lesions due to Mycobacterium tuberculosis. Patient 2 (P2) presented with oral candidiasis and recurrent pneumonia at 4 months of age and subsequently developed CMV pneumonitis. Both patients suffered heterozygous missense mutations in STAT1, leading to deleterious amino acid substitutions in the DNA binding domain (P1: c.1154C > T; p.T385M; P2. c.971G > T; p.C324F). Circulating CD4(+) T cells of both patients exhibited increased interferon-γ and decreased IL-17 expression as compared to controls. They also exhibited increased IFN-β and -γ-induced STAT1 phosphorylation that was reversed upon treatment with the JAK kinase inhibitor ruxolitinib.

CONCLUSION

STAT1 GOF mutations may present early in life with CID, consistent with the clinical heterogeneity of the disease. JAK kinase inhibitors may potentially be useful in some patients as adjunct therapy pending definitive treatment with bone marrow transplantation.

Enho Mutations Causing Low Adropin: A Possible Pathomechanism of MPO-ANCA Associated Lung Injury

BACKGROUND

Myeloperoxidase (MPO) anti-neutrophil cytoplasm autoantibody (ANCA)-associated vasculitis commonly causes life-threatening pulmonary alveolar hemorrhage or fibrosis. Only a limited number of candidate gene variants have been explored, but hitherto, are not widely confirmed. In the present study, we investigated the importance of energy homeostasis associated gene (Enho) mutations and adropin deficiency in the development of MPO-ANCA associated lung injury.

METHODS

We analyzed the peripheral blood mononuclear cells from 152 unrelated patients and 220 population-matched healthy individuals for genetic variations in Enho. Functional studies with adropin knockout (AdrKO) on C57BL/6J mice were also performed.

FINDINGS

Sequencing revealed six patients with p.Ser43Thr and that five patients shared Cys56Trp amino acid substitution in Enho. Serum concentration of adropin was significantly lower in patients than that of the healthy subjects (P<0.0001), especially those with Enho mutations. In vivo, homo- and heterozygous carriers of the null adropin allele exhibited MPO-ANCA associated pulmonary alveolar hemorrhage as compared to wild-type mice. AdrKO mice exhibit reduced eNOS (Ser1177) and Akt1 (Ser473) phosphorylation and loss of Treg cells.

INTERPRETATION

Our findings indicate that the presence of Enho mutations or adropin-deficiency is a probable molecular basis for the initial events triggered in MPO-ANCA associated lung injury.

Nucleic acid sensing and innate immunity: signaling pathways controlling viral pathogenesis and autoimmunity

Innate immunity refers to the body's initial response to curb infection upon exposure to invading organisms. While the detection of pathogen-associated molecules is an ancient form of host defense, if dysfunctional, autoimmune disease may result. The innate immune response during pathogenic infection is initiated through the activation of receptors recognizing conserved molecular patterns, such as nucleic acids from a virus' genome or replicative cycle. Additionally, the host's own nucleic acids are capable of activating an immune response. Therefore, it follows that the nucleic acid-sensing pathways must be tightly controlled to avoid an autoimmune response from recognition of self, yet still be unimpeded to respond to viral infections. In this review, we will describe the nucleic acid sensing pathways and how they respond to virus infection. Moreover, we will discuss autoimmune diseases that develop when these pathways fail to signal properly and identify knowledge gaps that are prime for interrogation.

Activation of STING requires palmitoylation at the Golgi

Stimulator of interferon genes (STING) is essential for the type I interferon response against DNA pathogens. In response to the presence of DNA and/or cyclic dinucleotides, STING translocates from the endoplasmic reticulum to perinuclear compartments. However, the role of this subcellular translocation remains poorly defined. Here we show that palmitoylation of STING at the Golgi is essential for activation of STING. Treatment with palmitoylation inhibitor 2-bromopalmitate (2-BP) suppresses palmitoylation of STING and abolishes the type I interferon response. Mutation of two membrane-proximal Cys residues (Cys88/91) suppresses palmitoylation, and this STING mutant cannot induce STING-dependent host defense genes. STING variants that constitutively induce the type I interferon response were found in patients with autoimmune diseases. The response elicited by these STING variants is effectively inhibited by 2-BP or an introduction of Cys88/91Ser mutation. Our results may lead to new treatments for cytosolic DNA-triggered autoinflammatory diseases.

STING is essential for the type I interferon immune response to foreign DNA. Here, the authors show that palmitoylation of STING at the Golgi is required for activating downstream signalling, and increased Golgi localization of certain STING variants may cause autoimmune disease in some cases.

Human USP18 deficiency underlies type 1 interferonopathy leading to severe pseudo-TORCH syndrome

Meuwissen and collaborators define a novel genetic cause of pseudo-TORCH syndrome, which resembles the sequelae of congenital infection and represents a novel type I interferonopathy.

Pseudo-TORCH syndrome (PTS) is characterized by microcephaly, enlarged ventricles, cerebral calcification, and, occasionally, by systemic features at birth resembling the sequelae of congenital infection but in the absence of an infectious agent. Genetic defects resulting in activation of type 1 interferon (IFN) responses have been documented to cause Aicardi-Goutières syndrome, which is a cause of PTS. Ubiquitin-specific peptidase 18 (USP18) is a key negative regulator of type I IFN signaling. In this study, we identified loss-of-function recessive mutations of USP18 in five PTS patients from two unrelated families. Ex vivo brain autopsy material demonstrated innate immune inflammation with calcification and polymicrogyria. In vitro, patient fibroblasts displayed severely enhanced IFN-induced inflammation, which was completely rescued by lentiviral transduction of USP18. These findings add USP18 deficiency to the list of genetic disorders collectively termed type I interferonopathies. Moreover, USP18 deficiency represents the first genetic disorder of PTS caused by dysregulation of the response to type I IFNs. Therapeutically, this places USP18 as a promising target not only for genetic but also acquired IFN-mediated CNS disorders.

Type I interferonopathies in pediatric rheumatology

Defective regulation of type I interferon response is associated with severe inflammatory phenotypes and autoimmunity. Type I interferonopathies are a clinically heterogenic group of Mendelian diseases with a constitutive activation of this pathway that might present as atypical, severe, early onset rheumatic diseases. Skin vasculopathy with chilblains and livedo reticularis, interstitial lung disease, and panniculitis are common. Recent studies have implicated abnormal responses to nucleic acid stimuli or defective regulation of downstream effector molecules in disease pathogenesis. As observed for IL1-β and autoinflammatory diseases, knowledge of the defects responsible for type I interferonopathies will likely promote the development of targeted therapy.

Type I interferonopathies in pediatric rheumatology

Defective regulation of type I interferon response is associated with severe inflammatory phenotypes and autoimmunity. Type I interferonopathies are a clinically heterogenic group of Mendelian diseases with a constitutive activation of this pathway that might present as atypical, severe, early onset rheumatic diseases. Skin vasculopathy with chilblains and livedo reticularis, interstitial lung disease, and panniculitis are common. Recent studies have implicated abnormal responses to nucleic acid stimuli or defective regulation of downstream effector molecules in disease pathogenesis. As observed for IL1-β and autoinflammatory diseases, knowledge of the defects responsible for type I interferonopathies will likely promote the development of targeted therapy.

Therapeutic options for cutaneous lupus erythematosus: recent advances and future prospects

INTRODUCTION

Treatment and prevention are of critical importance in patients with cutaneous lupus erythematosus (CLE), as the disease can have a devastating effect on patient well-being and quality of life.

AREAS COVERED

We conducted a selective search of the PubMed database for articles published between December 2010 and November 2015. This review encompasses both non-pharmaceutical (photoprotection, smoking cessation, drug withdrawal, and vitamin D replacement) and pharmaceutical (topicals, antimalarials, immunosuppressives, biologics, etc.) interventions used in the treatment of CLE. Expert Commentary: Recent work has expanded our understanding of established therapies as well as introduced new treatments for consideration, though existing medications still prove inadequate for a subset of patients. Changes in trial design may help to alleviate this issue.

Stimulator of interferon genes (STING): A "new chapter" in virus-associated cancer research. Lessons from wild-derived mouse models of innate immunity

Thanks to the numerous studies that have been carried out recently in the field of cytosolic DNA sensing, STING (Stimulator of Interferon Genes) is now recognized as a key mediator of innate immune signaling. A substantial body of evidence derived from in vivo mouse models demonstrates that STING-regulated pathways underlie the pathogenesis of many diseases including infectious diseases and cancers. It has also become evident from these studies that STING is a promising therapeutic target for the treatment of cancer. However, mouse strains commonly used for modelling innate immune response against infections or tumors do not allow investigators to accurately reproduce certain specific characteristics of immune response observed in human cells. In this review, we will discuss recent data demonstrating that the use of wild-derived genetically distinct inbred mice as a model for investigation into the innate immunity signaling networks may provide valuable insight into the STING-regulated pathways specific for human cells. The maximum complexity of STING-mediated mechanisms can probably be seen in case of DNA virus-induced carcinogenesis in which STING may perform unexpected biological activities. Therefore, in another part of this review we will summarize emerging data on the role of STING in human DNA virus-related oncopathologies, with particular attention to HPV-associated cervical cancer, aiming to demonstrate that STING indeed "starts a new chapter" in research on this issue and that wild-derived mouse models of STING-mediated response to infections will probably be helpful in finding out molecular basis for clinical observations.

Autoimmunity and Primary Immunodeficiency Disorders

Advances in DNA sequencing technologies have led to a quickening in the pace at which new genetic immunodeficiency disorders have been identified. Among the newly identified defects are a number of disorders that present primarily with autoimmunity as opposed to recurrent infections. These "immune dysregulation" disorders have begun to cluster together to form an increased understanding of some of the basic molecular mechanisms that underlie the establishment and maintenance of immune tolerance and the development of autoimmunity. This review will present three major themes that have emerged in our understanding of the mechanisms that underlie autoimmunity and immune dysregulation in humans.

Rare autoimmune disorders with Mendelian inheritance

Autoimmune diseases represent a heterogeneous group of common disorders defined by complex trait genetics and environmental effects. The genetic variants usually align in immune and metabolic pathways that affect cell survival or apoptosis and modulate leukocyte function. Nevertheless, the exact triggers of disease development remain poorly understood and the current therapeutic interventions only modify the disease course. Both the prevention and the cure of autoimmune disorders are beyond our present medical capabilities. In contrast, a growing number of single gene autoimmune disorders have also been identified and characterized in the last few decades. Mutations and other gene alterations exert significant effects in these conditions, and often affect genes involved in central or peripheral immunologic tolerance induction. Even though a single genetic abnormality may be the disease trigger, it usually upsets a number of interactions among immune cells, and the biological developments of these monogenic disorders are also complex. Nevertheless, identification of the triggering molecular abnormalities greatly contributes to our understanding of the pathogenesis of autoimmunity and facilitates the development of newer and more effective treatment strategies.

STING Signaling the enERGIC Way

The effector proteins IpaJ and VirA, from the bacterium Shigella flexneri, block the general secretory pathway (GSP) at different stages. In this issue of Cell Host & Microbe, Dobbs et al. (2015) use these proteins as a tool to pinpoint STING trafficking and signaling to the ER-Golgi intermediate compartment (ERGIC).

Targeted therapeutics in SLE: emerging strategies to modulate the interferon pathway

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease characterized by impaired immune tolerance, resulting in the generation of pathogenic autoantibodies and immune complexes. Although autoreactive B lymphocytes have been the first targets for biologic therapies in SLE, the importance of the innate immune system, and in particular, pathways involved in interferon (IFN) signaling, has emerged. There are now data supporting a central role for a plasmacytoid dendritic cell-derived type I IFN pathway in SLE, with a number of biologic therapeutics and small-molecule inhibitors undergoing clinical trials. Monoclonal antibodies targeting IFN-α have completed phase II clinical trials, and an antibody against the type I IFN receptor is entering a phase III trial. However, other IFNs, such as IFN gamma, and the more recently discovered type III IFNs, are also emerging as targets in SLE; and blockade of upstream components of the IFN signaling pathway may enable inhibition of more than one IFN subtype. In this review, we discuss the current understanding of IFNs in SLE, focusing on emerging therapies.

Copa Syndrome: a Novel Autosomal Dominant Immune Dysregulatory Disease

Inherently defective immunity typically results in either ineffective host defense, immune regulation, or both. As a category of primary immunodeficiency diseases, those that impair immune regulation can lead to autoimmunity and/or autoinflammation. In this review we focus on one of the most recently discovered primary immunodeficiencies that leads to immune dysregulation: "Copa syndrome". Copa syndrome is named for the gene mutated in the disease, which encodes the alpha subunit of the coatomer complex-I that, in aggregate, is devoted to transiting molecular cargo from the Golgi complex to the endoplasmic reticulum (ER). Copa syndrome is autosomal dominant with variable expressivity and results from mutations affecting a narrow amino acid stretch in the COPA gene-encoding COPα protein. Patients with these mutations typically develop arthritis and interstitial lung disease with pulmonary hemorrhage representing a striking feature. Immunologically Copa syndrome is associated with autoantibody development, increased Th17 cells and pro-inflammatory cytokine expression including IL-1β and IL-6. Insights have also been gained into the underlying mechanism of Copa syndrome, which include excessive ER stress owing to the impaired return of proteins from the Golgi, and presumably resulting aberrant cellular autophagy. As such it represents a novel cellular disorder of intracellular trafficking associated with a specific clinical presentation and phenotype.

Therapeutic advances in the treatment of vasculitis

Considerable therapeutic advances for the treatment of vasculitis of the young have been made in the past 10 years, including the development of outcome measures that facilitate clinical trial design. Notably, these include: a recognition that some patients with Kawasaki Disease require corticosteroids as primary treatment combined with IVIG; implementation of rare disease trial design for polyarteritis nodosa to deliver the first randomised controlled trial for children; first clinical trials involving children for anti-neutrophil cytoplasmic antibody (ANCA) vasculitis; and identification of monogenic forms of vasculitis that provide an understanding of pathogenesis, thus facilitating more targeted treatment. Robust randomised controlled trials for Henoch Schönlein Purpura nephritis and Takayasu arteritis are needed; there is also an over-arching need for trials examining new agents that facilitate corticosteroid sparing, of particular importance in the paediatric population since glucocorticoid toxicity is a major concern.

Recurrent Fevers for the Pediatric Immunologist: It's Not All Immunodeficiency

Autoinflammatory diseases are disorders of the innate immune system, characterized by systemic inflammation independent of infection and autoreactive antibodies or antigen-specific T cells. Similar to immunodeficiencies, these immune dysregulatory diseases have unique presentations, genetics, and available therapies. Given the presentation of fevers, rashes, and mucosal symptoms in many of the disorders, the allergist/immunologist is the appropriate medical home for these patients: to appropriately rule out immunodeficiencies, evaluate for allergic disease, and diagnose and treat recurrent fever disorders. However, many practicing physicians are unfamiliar with the clinical presentation, diagnosis, and treatment of autoinflammatory disorders. This review will focus on understanding the signs and symptoms of classic autoinflammatory disorders, introduce newly described monogenic and polygenic disorders, and address the approach to the patient with recurrent fevers to distinguish autoinflammation from immunodeficiency and autoimmunity.

Genetically defined autoinflammatory diseases

Autoinflammatory diseases are hyperinflammatory, immune dysregulatory conditions that typically present in early childhood with fever and rashes and disease-specific patterns of organ inflammation. This review provides a historic background of autoinflammatory disease research, an overview of the currently genetically defined autoinflammatory diseases, and insights into treatment strategies derived from understanding of the disease pathogenesis. The integrative assessment of autoinflammatory conditions led to the identification of innate pro-inflammatory cytokine 'amplification loops' as the cause of the systemic and organ-specific disease manifestations, which initially centered around increased IL-1 production and signaling. More recently, additional innate pro-inflammatory cytokine amplification loops resulting in increased Type I IFN, IL-17, IL-18, or IL-36 signaling or production have led to the successful use of targeted therapies in some of these conditions. Clinical findings such as fever patterns, type of skin lesions, genetic mutation testing, and the prevalent cytokine abnormalities can be used to group autoinflammatory diseases.

STING: infection, inflammation and cancer

Stimulator of interferon genes (STING) is activated by binding to cyclic dinucleotides (CDNs), which results in potent cytokine production. CDNs are produced by certain intracellular bacteria and are generated by the cyclic GMP–AMP synthase (cGAS) following binding to cytosolic DNA species, such as viral DNA.

STING-inducible innate immune molecules are essential for protection of the host against pathogens and are important for the stimulation of adaptive immunity.

Self-DNA, for example from the nucleus or mitochondria, can leak into the cytosolic compartment and stimulate STING activity to cause autoinflammatory disease. Certain mutations in the gene encoding STING can cause the protein to become permanently active and similarly induce autoinflammatory responses.

STING can be activated in phagocytes by DNA released from engulfed tumour cells and drive the production of cytokines necessary for generating robust antitumour T cell responses.

DNA-damaging agents can cause the release of nuclear DNA into the cytosol that stimulates STING-dependent cytokine production and phagocyte infiltration. This may be essential for eliminating damaged cells and generating antitumour T cell responses, but chronic stimulation may also promote inflammation-aggravated cancer.

STING agonists exert potent antitumour activity and may be effective, novel adjuvants in vaccine formulations. In contrast, inhibitors of STING signalling may be beneficial for the treatment of autoinflammatory disease, such as systemic lupus erythematosus (SLE), Aicardi–Goutières syndrome (AGS) and STING-associated vasculopathy with onset in infancy (SAVI).

Activation of STING (stimulator of interferon genes) by cytosolic aberrant DNA species or cyclic dinucleotides triggers transcription of numerous innate immune genes. In this Review, the author summarizes recent insights into the regulation of STING signalling and its role in autoinflammatory disease and cancer.

The rapid detection of microbial agents is essential for the effective initiation of host defence mechanisms against infection. Understanding how cells detect cytosolic DNA to trigger innate immune gene transcription has important implications — not only for comprehending the immune response to pathogens but also for elucidating the causes of autoinflammatory disease involving the sensing of self-DNA and the generation of effective antitumour adaptive immunity. The discovery of the STING (stimulator of interferon genes)-controlled innate immune pathway, which mediates cytosolic DNA-induced signalling events, has recently provided important insights into these processes, opening the way for the development of novel immunization regimes, as well as therapies to treat autoinflammatory disease and cancer.

Dendritic Cells in Systemic Lupus Erythematosus: From Pathogenic Players to Therapeutic Tools

System lupus erythematosus (SLE) is a multifactorial systemic autoimmune disease with a wide variety of presenting features. SLE is believed to result from dysregulated immune responses, loss of tolerance of CD4 T cells and B cells to ubiquitous self-antigens, and the subsequent production of anti-nuclear and other autoreactive antibodies. Recent research has associated lupus development with changes in the dendritic cell (DC) compartment, including altered DC subset frequency and localization, overactivation of mDCs and pDCs, and functional defects in DCs. Here we discuss the current knowledge on the role of DC dysfunction in SLE pathogenesis, with the focus on DCs as targets for interventional therapies.

Mitochondrial DNA sensing by STING signaling participates in inflammation, cancer and beyond

Recent studies have revealed the diverse pathophysiological functions of mitochondria beyond traditional energetic metabolism in cells. Mitochondria-released damage-associated molecular patterns, particularly mitochondrial deoxyribonucleic acid (mtDNA), play a central role in host immune defenses against foreign pathogens. Newly discovered cGAS-STING signaling is responsible for microbial DNA recognition, and potentially participates in mitochondrial DNA sensing. Inappropriate inflammatory signaling mediated by mtDNA is implicated in various human diseases, especially infectious/inflammatory disease and cancer. In addition, mtDNA horizontal transfer between tumor cells and surrounding somatic cells has been recently observed and been associated with tumorigenesis and cancer progression. In this review, we will summarize the molecular signaling of mtDNA recognition (especially STING signaling), and discuss the underlying mechanism by which mtDNA transfer triggers cancer progression in human. Besides, we will highlight the central role of mtDNA in host immunity, with particular emphasis on mtDNA-induced NETs (neutrophil extracellular traps) formation, apoptosis and autophagy.

Idiopathic inflammatory myopathies and the lung

Idiopathic inflammatory myositis (IIM) is a group of rare connective tissue diseases (CTDs) characterised by muscular and extramuscular signs, in which lung involvement is a challenging issue. Interstitial lung disease (ILD) is the hallmark of pulmonary involvement in IIM, and causes morbidity and mortality, resulting in an estimated excess mortality of 50% in some series. Except for inclusion body myositis, these extrapulmonary disorders are associated with the general and visceral involvement frequently found in other CTDs including fever, Raynaud's phenomenon, arthralgia, nonspecific cutaneous modifications and ILD, for which the prevalence is estimated to be up to 65%. Substantial heterogeneity exists within the spectrum of IIMs, and each condition is associated with various frequencies and subtypes of pulmonary involvement. This heterogeneity is partly related to the presence of various autoantibodies encompassing anti-synthetase, anti-MDA5 and anti-PM/Scl. ILD is present in all subsets of IIM including juvenile myositis, but is more frequent in dermatomyositis and overlap myositis. IIM can also be associated with other presentations of respiratory involvement, namely pulmonary arterial hypertension, pleural disease, infections, drug-induced toxicity, malignancy and respiratory muscle weakness. Here, we critically review the current knowledge about adult and juvenile myositis-associated lung disease with a detailed description of therapeutics for chronic and rapidly progressive ILD.

Spondyloenchondrodysplasia Due to Mutations in ACP5: A Comprehensive Survey

Purpose

Spondyloenchondrodysplasia is a rare immuno-osseous dysplasia caused by biallelic mutations in ACP5. We aimed to provide a survey of the skeletal, neurological and immune manifestations of this disease in a cohort of molecularly confirmed cases.

Methods

We compiled clinical, genetic and serological data from a total of 26 patients from 18 pedigrees, all with biallelic ACP5 mutations.

Results

We observed a variability in skeletal, neurological and immune phenotypes, which was sometimes marked even between affected siblings. In total, 22 of 26 patients manifested autoimmune disease, most frequently autoimmune thrombocytopenia and systemic lupus erythematosus. Four patients were considered to demonstrate no clinical autoimmune disease, although two were positive for autoantibodies. In the majority of patients tested we detected upregulated expression of interferon-stimulated genes (ISGs), in keeping with the autoimmune phenotype and the likely immune-regulatory function of the deficient protein tartrate resistant acid phosphatase (TRAP). Two mutation positive patients did not demonstrate an upregulation of ISGs, including one patient with significant autoimmune disease controlled by immunosuppressive therapy.

Conclusions

Our data expand the known phenotype of SPENCD. We propose that the OMIM differentiation between spondyloenchondrodysplasia and spondyloenchondrodysplasia with immune dysregulation is no longer appropriate, since the molecular evidence that we provide suggests that these phenotypes represent a continuum of the same disorder. In addition, the absence of an interferon signature following immunomodulatory treatments in a patient with significant autoimmune disease may indicate a therapeutic response important for the immune manifestations of spondyloenchondrodysplasia.

Microbial pathogenesis and type III interferons

The innate immune system possesses a multitude of pathways to sense and respond to microbial pathogens. One such family are the interferons (IFNs), a family of cytokines that are involved in several cellular functions. Type I IFNs are appreciated to be important in several viral and bacterial diseases, while the recently identified type III IFNs (IFNL1, IFNL2, IFNL3, IFNL4) have been studied primarily in the context of viral infection. Viral and bacterial infections however are not mutually exclusive, and often the presence of a viral pathogen increases the pathogenesis of bacterial infection. The role of type III IFN in bacterial and viral-bacterial co-infections has just begun to be explored. In this mini review we discuss type III IFN signaling and its role in microbial pathogenesis with an emphasis on the work that has been conducted with bacterial pathogens.

Shaping the spectrum - From autoinflammation to autoimmunity

Historically, autoimmune-inflammatory disorders were subdivided into autoinflammatory vs. autoimmune diseases. About a decade ago, an immunological continuum was proposed, placing "classical" autoinflammatory disorders, characterized by systemic inflammation in the absence of high-titer autoantibodies or autoreactive T lymphocytes, at the one end, and autoimmune disorders at the other end. We provide an overview of recent developments and observations, filling in some of the gaps and showing strong interconnections between innate and adaptive immune mechanisms, indicating that disorders from both ends of the immunological spectrum indeed share key pathomechanisms. We focus on three exemplary disorders: i) systemic juvenile idiopathic arthritis representing "classical" autoinflammatory disorders; ii) psoriasis, a mixed pattern disease; and iii) systemic lupus erythematosus, a prototypical autoimmune disease. We summarize scientific observations suggesting that, depending on disease stages and/or duration, individualized treatment targeting innate or adaptive immune mechanisms in disorders from either end of the immunological spectrum may control disease activity.

Influenza A virus targets a cGAS-independent STING pathway that controls enveloped RNA viruses

Stimulator of interferon genes (STING) is known be involved in control of DNA viruses but has an unexplored role in control of RNA viruses. During infection with DNA viruses STING is activated downstream of cGAMP synthase (cGAS) to induce type I interferon. Here we identify a STING-dependent, cGAS-independent pathway important for full interferon production and antiviral control of enveloped RNA viruses, including influenza A virus (IAV). Further, IAV interacts with STING through its conserved hemagglutinin fusion peptide (FP). Interestingly, FP antagonizes interferon production induced by membrane fusion or IAV but not by cGAMP or DNA. Similar to the enveloped RNA viruses, membrane fusion stimulates interferon production in a STING-dependent but cGAS-independent manner. Abolishment of this pathway led to reduced interferon production and impaired control of enveloped RNA viruses. Thus, enveloped RNA viruses stimulate a cGAS-independent STING pathway, which is targeted by IAV.

Synergy between Hematopoietic and Radioresistant Stromal Cells Is Required for Autoimmune Manifestations of DNase II-/-IFNaR-/- Mice

Detection of endogenous nucleic acids by cytosolic receptors, dependent on STING, and endosomal sensors, dependent on Unc93b1, can provoke inflammatory responses that contribute to a variety of autoimmune and autoinflammatory diseases. In DNase II-deficient mice, the excessive accrual of undegraded DNA leads to both a STING-dependent inflammatory arthritis and additional Unc93b1-dependent autoimmune manifestations, including splenomegaly, extramedullary hematopoiesis, and autoantibody production. In this study, we use bone marrow chimeras to show that clinical and histological inflammation in the joint depends upon DNase II deficiency in both donor hematopoietic cells and host radioresistant cells. Additional features of autoimmunity in these mice, known to depend on Unc93b1 and therefore endosomal TLRs, also require DNase II deficiency in both donor and host compartments, but only require functional TLRs in the hematopoietic cells. Collectively, our data demonstrate a major role of both stromal and hematopoietic cells in all aspects of DNA-driven autoimmunity. These findings further point to the importance of cytosolic nucleic acid sensors in creating an inflammatory environment that facilitates the development of Unc93b1-dependent autoimmunity.

Failure to thrive, interstitial lung disease, and progressive digital necrosis with onset in infancy

Key teaching points • SAVI is a recently described interferonopathy resulting from constitutive action of STING and up-regulation of IFN-β signaling. • SAVI is characterized by facial erythema with telangiectasia, acral/cold-sensitive tissue ulceration and amputations, and interstitial lung disease. It has overlapping features with Aicardi-Goutières syndrome and familial chilblain lupus. • Traditional immunosuppressive medications and biologic therapies appear to be of limited benefit, but JAK inhibitors may impact disease progression.

Submicron-sized hydrogels incorporating cyclic dinucleotides for selective delivery and elevated cytokine release in macrophages

Despite the emerging evidences supporting the potential of cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) as a vaccine adjuvant, few properly designed micro-/nanocarriers for the delivery of cyclic dinucleotides have been developed. In this study, we formulated cGAMP within linear polyethyleneimine (LPEI)/hyaluronic acid (HA) hydrogels via inverse water-in-oil (W/O) emulsion/crosslinking. Spherical and cationic LPEI/HA hydrogels (LH gels) with a size of 455.3±3.1nm and a surface charge of 48.7±3.7mV were selectively and efficiently delivered into phagocytic macrophage cells, which are one type of antigen-presenting cells (APCs), but not into non-phagocytic fibroblast cells. LH gels incorporating cGAMP (LH/cGAMP gels) elicited excellent induction of the cytokines interferon-β (IFN-β) and interleukin-6 (IL-6). In particular, the amount of IFN-β released by LH hydrogels was significantly increased by 2.5-fold compared to that released by conventional cationic liposomes, such as Lipofectamine. In addition, fabricated LH gels showed superior biocompatibility in phagocytic cell lines and primary bone marrow-derived macrophages (BMDMs). After intramuscular injection with ovalbumin into C57BL/6 mice, LH/cGAMP gels exhibited significantly elevated levels of anti-ovalbumin total IgG in serum and IFN-β mRNA in spleens. Thus, the newly designed cGAMP-incorporating hydrogels can serve as safe and potent adjuvants for vaccination and immunotherapy.

STATEMENT OF SIGNIFICANCE

Since cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) was first found as a second messenger of immune signaling in human systems in February 2013 (Science, 15, 826), several scientific studies have been reported related to the potential of cGAMP as a vaccine adjuvant or additive for immunotherapy. However, only naked cGAMP without carriers were studied via intramuscular or intranasal administration so far. In our study, we first investigated the feasibility of polymeric hydrogels incorporating cGAMP in terms of selective uptake into phagocytic antigen presenting cells (APCs), induction of cytokines, production of target antibodies, and biocompatibility for vaccination and immunotherapy in vitro and in vivo. Therefore, we believe this manuscript would be of great interest to the biomaterial communities especially who are studying immunotherapy.

Type I/II cytokines, JAKs, and new strategies for treating autoimmune diseases

Cytokines are major drivers of autoimmunity, and biologic agents targeting cytokines have revolutionized the treatment of immune-mediated diseases. Despite the effectiveness of these drugs, they do not induce complete remission in all patients, prompting the development of alternative strategies - including targeting of intracellular signal transduction pathways downstream of cytokines. Many cytokines that bind type I and type II cytokine receptors are critical regulators of immune-mediated diseases and employ the Janus kinase (JAK) and signal transducer and activator of transcription (STAT) pathway to exert their effect. Pharmacological inhibition of JAKs blocks the actions of type I/II cytokines, and within the past 3 years therapeutic JAK inhibitors, or Jakinibs, have become available to rheumatologists. Jakinibs have proven effective for the treatment of rheumatoid arthritis and other inflammatory diseases. Adverse effects of these agents are largely related to their mode of action and include infections and hyperlipidemia. Jakinibs are currently being investigated for a number of new indications, and second-generation selective Jakinibs are being developed and tested. Targeting STATs could be a future avenue for the treatment of rheumatologic diseases, although substantial challenges remain. Nonetheless, the ability to therapeutically target intracellular signalling pathways has already created a new paradigm for the treatment of rheumatologic disease.