Interferon signaling gene expression as a diagnostic biomarker for monogenic interferonopathies.

Interferon signaling gene (ISG) expression scores are potential markers of inflammation with significance from cancer to genetic syndromes. In Aicardi Goutières Syndrome (AGS), a disorder of abnormal DNA and RNA metabolism, this score has potential as a diagnostic biomarker, although the approach to ISG calculation has not been standardized or validated. To optimize ISG calculation and validate ISG as a diagnostic biomarker, mRNA levels of 36 type I interferon response genes were quantified from 997 samples (including 334 AGS), and samples were randomized into training and test datasets. An independent validation cohort (n = 122) was also collected. ISGs were calculated using all potential combinations up to 6 genes. A 4-gene approach (IFI44L, IFI27, USP18, IFI6) was the best-performing model [area under the curve (AUC) of 0.8872 (training dataset), 0.9245 (test dataset)]. The majority of top performing gene combinations included IFI44L. Performance of IFI44L-alone was 0.8762 (training dataset) and 0.9580 (test dataset) by AUC. The top approaches were able to discriminate cases of genetic interferonopathy from control samples. This study validates the context of use for the ISG score as a diagnostic biomarker and underscores the importance of IFI44L in diagnosis of genetic interferonopathies.

A case of mother and child with CANDLE syndrome: Diagnosis and subsequent treatment with baricitinib.

Chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperature (CANDLE) or proteasome-associated autoinflammatory syndrome is a rare autoinflammatory disorder that typically presents in infancy with characteristic symptoms, including recurrent fever, panniculitis, and progressive lipodystrophy, among other findings. We present a case of mother and child with CANDLE syndrome. The child was eventually started on baricitinib with normalization of rash and systemic findings.

The Role of Interferon-γ in Autoimmune Polyendocrine Syndrome Type 1.

BACKGROUND: Autoimmune polyendocrine syndrome type 1 (APS-1) is a life-threatening, autosomal recessive syndrome caused by autoimmune regulator (AIRE) deficiency. In APS-1, self-reactive T cells escape thymic negative selection, infiltrate organs, and drive autoimmune injury. The effector mechanisms governing T-cell-mediated damage in APS-1 remain poorly understood. METHODS: We examined whether APS-1 could be classified as a disease mediated by interferon-γ. We first assessed patients with APS-1 who were participating in a prospective natural history study and evaluated mRNA and protein expression in blood and tissues. We then examined the pathogenic role of interferon-γ using Aire-/-Ifng-/- mice and Aire-/- mice treated with the Janus kinase (JAK) inhibitor ruxolitinib. On the basis of our findings, we used ruxolitinib to treat five patients with APS-1 and assessed clinical, immunologic, histologic, transcriptional, and autoantibody responses. RESULTS: Patients with APS-1 had enhanced interferon-γ responses in blood and in all examined autoimmunity-affected tissues. Aire-/- mice had selectively increased interferon-γ production by T cells and enhanced interferon-γ, phosphorylated signal transducer and activator of transcription 1 (pSTAT1), and CXCL9 signals in multiple organs. Ifng ablation or ruxolitinib-induced JAK-STAT blockade in Aire-/- mice normalized interferon-γ responses and averted T-cell infiltration and damage in organs. Ruxolitinib treatment of five patients with APS-1 led to decreased levels of T-cell-derived interferon-γ, normalized interferon-γ and CXCL9 levels, and remission of alopecia, oral candidiasis, nail dystrophy, gastritis, enteritis, arthritis, Sjögren's-like syndrome, urticaria, and thyroiditis. No serious adverse effects from ruxolitinib were identified in these patients. CONCLUSIONS: Our findings indicate that APS-1, which is caused by AIRE deficiency, is characterized by excessive, multiorgan interferon-γ-mediated responses. JAK inhibition with ruxolitinib in five patients showed promising results. (Funded by the National Institute of Allergy and Infectious Diseases and others.).

Disease flares with baricitinib dose reductions and development of flare criteria in patients with CANDLE/PRAAS.

OBJECTIVES: Patients with chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperature/proteasome-associated autoinflammatory syndrome (CANDLE/PRAAS) respond to the janus kinase inhibitor 1/2 inhibition with baricitinib at exposures higher than in rheumatoid arthritis. Baricitinib dose reductions to minimise exposure triggered disease flares which we used to develop 'flare criteria'. METHODS: Of 10 patients with CANDLE/PRAAS treated with baricitinib in an open-label expanded-access programme, baricitinib doses were reduced 14 times in 9 patients between April 2014 and December 2019. Retrospective data analysis of daily diary scores and laboratory markers collected before and after the dose reductions were used to develop 'clinical' and 'subclinical' flare criteria. Disease flare rates were compared among patients with <25% and >25% dose reductions and during study visits when patients received recommended 'optimized' baricitinib doses (high-dose visits) versus lower than recommended baricitinib doses (low-dose visits) using two-sided χ2 tests. RESULTS: In the 9/10 patients with CANDLE with dose reduction, 7/14 (50%) times the dose was reduced resulted in a disease flare. All four dose reductions of >25% triggered a disease flare (p <0.05). Assessment of clinical and laboratory changes during disease flares allowed the development of disease flare criteria that were assessed during visits when patients received high or low doses of baricitinib. Disease flare criteria were reached during 43.14% of low-dose visits compared with 12.75% of high-dose visits (p <0.0001). Addition of an interferon score as an additional flare criterion increased the sensitivity to detect disease flares. CONCLUSION: We observed disease flares and rebound inflammation with baricitinib dose reductions and proposed flare criteria that can assist in monitoring disease activity and in designing clinical studies in CANDLE/PRAAS.

Anakinra-Associated Systemic Amyloidosis.

OBJECTIVE: To describe a 41-year-old woman with a history of neonatal onset multisystem inflammatory disease, on treatment with daily subcutaneous injections of 600 mg of recombinant interleukin-1 receptor antagonist (IL-1Ra) protein, anakinra, since the age of 28, who presented with golf-ball size nodules at the anakinra injection sites, early satiety, new onset nephrotic syndrome in the context of normal markers of systemic inflammation. METHODS: Clinical history and histologic evaluation of biopsies of skin, gastric mucosa, and kidney with Congo-red staining and proteomic evaluation of microdissected Congo red-positive amyloid deposits by liquid chromatography-tandem mass spectrometry. RESULTS: The skin, stomach, and kidney biopsies all showed the presence of Congo red-positive amyloid deposits. Mass spectrometry-based proteomics demonstrated that the amyloid deposits in all sites were of AIL1RAP (IL-1Ra protein)-type. These were characterized by high spectral counts of the amyloid signature proteins (apolipoprotein AIV, apolipoprotein E, and serum amyloid P-component) and the amyloidogenic IL-1Ra protein, which were present in Congo red-positive areas and absent in Congo red-negative areas. The amino acid sequence identified by mass spectrometry confirmed that the amyloid precursor protein was recombinant IL-1Ra (anakinra) and not endogenous wild-type IL-1Ra. CONCLUSION: This is the first report of iatrogenic systemic amyloidosis due to an injectable protein drug, which was caused by recombinant IL1Ra (anakinra).

Identification of eight novel proteasome variants in five unrelated cases of proteasome-associated autoinflammatory syndromes (PRAAS).

Mutations in genes coding for proteasome subunits and/or proteasome assembly helpers typically cause recurring autoinflammation referred to as chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperatures (CANDLE) or proteasome-associated autoinflammatory syndrome (PRAAS). Patients with CANDLE/PRAAS present with mostly chronically elevated type I interferon scores that emerge as a consequence of increased proteotoxic stress by mechanisms that are not fully understood. Here, we report on five unrelated patients with CANDLE/PRAAS carrying novel inherited proteasome missense and/or nonsense variants. Four patients were compound heterozygous for novel pathogenic variants in the known CANDLE/PRAAS associated genes, PSMB8 and PSMB10, whereas one patient showed additive loss-of-function mutations in PSMB8. Variants in two previously not associated proteasome genes, PSMA5 and PSMC5, were found in a patient who also carried the PSMB8 founder mutation, p.T75M. All newly identified mutations substantially impact the steady-state expression of the affected proteasome subunits and/or their incorporation into mature 26S proteasomes. Our observations expand the spectrum of PRAAS-associated genetic variants and improve a molecular diagnosis and genetic counseling of patients with sterile autoinflammation.

Constitutively active Lyn kinase causes a cutaneous small vessel vasculitis and liver fibrosis syndrome.

Neutrophilic inflammation is a hallmark of many monogenic autoinflammatory diseases; pathomechanisms that regulate extravasation of damaging immune cells into surrounding tissues are poorly understood. Here we identified three unrelated boys with perinatal-onset of neutrophilic cutaneous small vessel vasculitis and systemic inflammation. Two patients developed liver fibrosis in their first year of life. Next-generation sequencing identified two de novo truncating variants in the Src-family tyrosine kinase, LYN, p.Y508*, p.Q507* and a de novo missense variant, p.Y508F, that result in constitutive activation of Lyn kinase. Functional studies revealed increased expression of ICAM-1 on induced patient-derived endothelial cells (iECs) and of ß2-integrins on patient neutrophils that increase neutrophil adhesion and vascular transendothelial migration (TEM). Treatment with TNF inhibition improved systemic inflammation; and liver fibrosis resolved on treatment with the Src kinase inhibitor dasatinib. Our findings reveal a critical role for Lyn kinase in modulating inflammatory signals, regulating microvascular permeability and neutrophil recruitment, and in promoting hepatic fibrosis.

Establishing 20S Proteasome Genetic, Translational and Post-Translational Status from Precious Biological and Patient Samples with Top-Down MS.

The mammalian 20S catalytic core of the proteasome is made of 14 different subunits (α1-7 and ß1-7) but exists as different subtypes depending on the cell type. In immune cells, for instance, constitutive catalytic proteasome subunits can be replaced by the so-called immuno-catalytic subunits, giving rise to the immunoproteasome. Proteasome activity is also altered by post-translational modifications (PTMs) and by genetic variants. Immunochemical methods are commonly used to investigate these PTMs whereby protein-tagging is necessary to monitor their effect on 20S assembly. Here, we present a new miniaturized workflow combining top-down and bottom-up mass spectrometry of immunopurified 20S proteasomes that analyze the proteasome assembly status as well as the full proteoform footprint, revealing PTMs, mutations, single nucleotide polymorphisms (SNPs) and induction of immune-subunits in different biological samples, including organoids, biopsies and B-lymphoblastoid cell lines derived from patients with proteasome-associated autoinflammatory syndromes (PRAAS). We emphasize the benefits of using top-down mass spectrometry in preserving the endogenous conformation of protein modifications, while enabling a rapid turnaround (1 h run) and ensuring high sensitivity (1-2 pmol) and demonstrate its capacity to semi-quantify constitutive and immune proteasome subunits.

Case report: De novo SAMD9L truncation causes neonatal-onset autoinflammatory syndrome which was successfully treated with hematopoietic stem cell transplantation.

During recent years, the identification of monogenic mutations that cause sterile inflammation has expanded the spectrum of autoinflammatory diseases, clinical disorders characterized by uncontrolled systemic and organ-specific inflammation that, in some cases, can mirror infectious conditions. Early studies support the concept of innate immune dysregulation with a predominance of myeloid effector cell dysregulation, particularly neutrophils and macrophages, in causing tissue inflammation. However, recent discoveries have shown a complex overlap of features of autoinflammation and/or immunodeficiency contributing to severe disease phenotypes. Here, we describe the first Argentine patient with a newly described frameshift mutation in SAMD9L c.2666delT/p.F889Sfs*2 presenting with a complex phenotypic overlap of CANDLE-like features and severe infection-induced cytopenia and immunodeficiency. The patient underwent a fully matched unrelated HSCT and has since been in inflammatory remission 5 years post-HSCT.

Analysis of factors associated with the success of microimplant-assisted rapid palatal expansion.

INTRODUCTION: Success-related factors of microimplant-assisted rapid palatal expansion (MARPE) were evaluated, including age, palatal depth, suture, and parassutural bone thickness, suture density and maturation, and the relation to corticopuncture (CP) technique, as well as skeletal and dental effects. METHODS: Sixty-six cone-beam computed tomography scans were analyzed before and after rapid maxillary expansion procedures in 33 patients aged 18-52 years for both sexes. The scans were generated in digital imaging and communications in medicine file format and analyzed in the multiplanar reconstruction of the regions of interest. Palatal depth, suture thickness, density and maturation, age, and CP were assessed. To evaluate dental and skeletal effects, the sample was divided into 4 groups: successful MARPE (SM), SM + CP technique (SMCP), failure MARPE (FM), and FM + CP (FMCP). RESULTS: Successful groups presented more skeletal expansion and dental tipping than failure groups (P <0.05). The mean age of the FMCP group was significantly higher than the SM groups; suture and parassutural thickness significantly related to the success, and patients who received CP showed a success rate of 81.2% compared with 33.3% in the no CP group (P <0.05). Suture density and palatal depth did not show a difference between the success and failure groups. Suture maturation was higher in SMCP and FM groups (P <0.05). CONCLUSIONS: Older age, thin palatal bone, and higher stage of maturation can influence the success of MARPE. CP technique in these patients appears to have a positive impact, increasing the chance of treatment success.

Three-Dimensional Evaluation of Dental Arches in Individuals with Syndromic Craniosynostosis.

Objective: Individuals with syndromic craniosynostosis present alterations in the dental arches due to anomalies caused by the early fusion of the craniomaxillary sutures. This study aimed to compare intradental and interdental dimensions between individuals with Apert and Crouzon syndromes and nonsyndromic controls. Materials and Methods: Digital models were obtained from the archive of a public tertiary care hospital. The sample consisted of 34 patients (Apert n = 18, Crouzon n = 16) and 34 nonsyndromic controls matched for gender and age. Measurements of perimeter, length, intercanine and intermolar distances (upper and lower), overjet, and molar ratio were performed. Statistical comparisons were performed using ANOVA and Tukey tests (p < 0.05). Results: Patients with Apert and Crouzon syndromes have severely reduced maxillary transverse dimensions, perimeter, and length of the upper arch compared to the control group (p < 0.001). The lower arch is less impacted. Patients with Apert syndrome had an anterior crossbite (p < 0.001), while patients with Crouzon syndrome had an edge-to-edge bite (p < 0.011). Patients with Apert and Crouzon syndromes do not have serious transverse proportion problems when comparing the upper and lower arches. Conclusions: In this sample, both the Apert and Crouzon groups have severely compromised upper arches compared to the control group. Mild dentoalveolar expansion in the maxilla should be sufficient for the transverse adaptation of the dental arches before frontofacial advancement.

Biphasic JNK signaling reveals distinct MAP3K complexes licensing inflammasome formation and pyroptosis.

Kinase signaling in the tiered activation of inflammasomes and associated pyroptosis is a prime therapeutic target for inflammatory diseases. While MAPKs subsume pivotal roles during inflammasome priming, specifically the MAP3K7/JNK1/NLRP3 licensing axis, their involvement in successive steps of inflammasome activation is poorly defined. Using live-cell MAPK biosensors to focus on the inflammasome triggering event allowed us to identify a subsequent process of biphasic JNK activation. We find that this biphasic post-trigger JNK signaling initially facilitates the mitochondrial reactive oxygen species generation needed to support core inflammasome formation, then supports the gasdermin-mediated cell permeation required for release of active IL-1ß from human macrophages. We further identify and characterize a xanthine oxidase-ROS activated MAP3K5/JNK2 substrate licensing complex as a novel regulator of the GSDMD mobilization which precedes pyroptosis. We show that inhibitors targeting this MAP3K5 cascade alleviate morbidity in mouse models of colitis and dampen both augmented IL-1ß release and cell permeation in monocytes derived from patients with gain-of-function inflammasomopathies.

Antiviral innate immunity is diminished in the upper respiratory tract of severe COVID-19 patients.

Understanding early innate immune responses to coronavirus disease 2019 (COVID-19) is crucial to developing targeted therapies to mitigate disease severity. Severe acute respiratory syndrome coronavirus (SARS-CoV)-2 infection elicits interferon expression leading to transcription of IFN-stimulated genes (ISGs) to control viral replication and spread. SARS-CoV-2 infection also elicits NF-κB signaling which regulates inflammatory cytokine expression contributing to viral control and likely disease severity. Few studies have simultaneously characterized these two components of innate immunity to COVID-19. We designed a study to characterize the expression of interferon alpha-2 (IFNA2) and interferon beta-1 (IFNB1), both type-1 interferons (IFN-1), interferon-gamma (IFNG), a type-2 interferon (IFN-2), ISGs, and NF-κB response genes in the upper respiratory tract (URT) of patients with mild (outpatient) versus severe (hospitalized) COVID-19. Further, we characterized the weekly dynamics of these responses in the upper and lower respiratory tracts (LRTs) and blood of severe patients to evaluate for compartmental differences. We observed significantly increased ISG and NF-κB responses in the URT of mild compared with severe patients early during illness. This pattern was associated with increased IFNA2 and IFNG expression in the URT of mild patients, a trend toward increased IFNB1-expression and significantly increased STING/IRF3/cGAS expression in the URT of severe patients. Our by-week across-compartment analysis in severe patients revealed significantly higher ISG responses in the blood compared with the URT and LRT of these patients during the first week of illness, despite significantly lower expression of IFNA2, IFNB1, and IFNG in blood. NF-κB responses, however, were significantly elevated in the LRT compared with the URT and blood of severe patients during peak illness (week 2). Our data support that severe COVID-19 is associated with impaired interferon signaling in the URT during early illness and robust pro-inflammatory responses in the LRT during peak illness.

Anakinra-Associated Amyloidosis.

This case report describes 2 patients with iatrogenic amyloidosis secondary to subcutaneous injections of anakinra to manage neonatal-onset multisystem inflammatory disease.

The 2021 EULAR/American College of Rheumatology Points to Consider for Diagnosis, Management and Monitoring of the Interleukin-1 Mediated Autoinflammatory Diseases: Cryopyrin-Associated Periodic Syndromes, Tumour Necrosis Factor Receptor-Associated Periodic Syndrome, Mevalonate Kinase Deficiency, and Deficiency of the Interleukin-1 Receptor Antagonist.

BACKGROUND: The interleukin-1 (IL-1) mediated systemic autoinflammatory diseases, including the cryopyrin- associated periodic syndromes (CAPS), tumour necrosis factor receptor-associated periodic syndrome (TRAPS), mevalonate kinase deficiency (MKD) and deficiency of the IL-1 receptor antagonist (DIRA), belong to a group of rare immunodysregulatory diseases that primarily present in early childhood with variable multiorgan involvement. When untreated, patients with severe clinical phenotypes have a poor prognosis, and diagnosis and management of these patients can be challenging. However, approved treatments targeting the proinflammatory cytokine IL-1 have been life changing and have significantly improved patient outcomes. OBJECTIVE: To establish evidence-based recommendations for diagnosis, treatment and monitoring of patients with IL-1 mediated autoinflammatory diseases to standardise their management. METHODS: A multinational, multidisciplinary task force consisting of physician experts, including rheumatologists, patients or caregivers and allied healthcare professionals, was established. Evidence synthesis, including systematic literature review and expert consensus (Delphi) via surveys, was conducted. Consensus methodology was used to formulate and vote on statements to guide optimal patient care. RESULTS: The task force devised five overarching principles, 14 statements related to diagnosis, 10 on therapy, and nine focused on long-term monitoring that were evidence and/or consensus-based for patients with IL-1 mediated diseases. An outline was developed for disease-specific monitoring of inflammation-induced organ damage progression and reported treatments of CAPS, TRAPS, MKD and DIRA. CONCLUSION: The 2021 EULAR/American College of Rheumatology points to consider represent state-of-the-art knowledge based on published data and expert opinion to guide diagnostic evaluation, treatment and monitoring of patients with CAPS, TRAPS, MKD and DIRA, and to standardise and improve care, quality of life and disease outcomes.

Inborn Errors of Immunity With Fetal or Perinatal Clinical Manifestations.

In this article we revised the literature on Inborn Errors of Immunity (IEI) keeping our focus on those diseases presenting with intrauterine or perinatal clinical manifestations. We opted to describe our findings according to the IEI categories established by the International Union of Immunological Societies, predominantly addressing the immunological features of each condition or group of diseases. The main finding is that such precocious manifestations are largely concentrated in the group of primary immune regulatory disorders (PIRDs) and not in the group of classical immunodeficiencies. The IEI categories with higher number of immunological manifestations in utero or in perinatal period are: (i) diseases of immune dysregulation (HLH, IPEX and other Tregopathies, autosomal recessive ALPS with complete lack of FAS protein expression) and (ii) autoinflammatory diseases (NOMID/CINCA, DIRA and some interferonopathies, such as Aicardi-Goutières syndrome, AGS, and USP18 deficiency). Regarding the other IEI categories, some patients with Omenn syndrome (an atypical form of SCID), and a few X-linked CGD patients present with clinical manifestations at birth associated to immune dysregulation. The most frequent clinical features were hydrops fetalis, intrauterine growth retardation leading to fetal loss, stillbirths, and prematurity, as in HLH and IPEX. Additionally, pseudo-TORCH syndrome was observed in AGS and in USP18 deficiency. The main goal of our review was to contribute to increasing the medical awareness of IEI with intrauterine and perinatal onset, which has obvious implications for diagnosis, treatment, and genetic counseling.

The 2021 EULAR/American College of Rheumatology points to consider for diagnosis, management and monitoring of the interleukin-1 mediated autoinflammatory diseases: cryopyrin-associated periodic syndromes, tumour necrosis factor receptor-associated periodic syndrome, mevalonate kinase deficiency, and deficiency of the interleukin-1 receptor antagonist.

BACKGROUND: The interleukin-1 (IL-1) mediated systemic autoinflammatory diseases, including the cryopyrin-associated periodic syndromes (CAPS), tumour necrosis factor receptor-associated periodic syndrome (TRAPS), mevalonate kinase deficiency (MKD) and deficiency of the IL-1 receptor antagonist (DIRA), belong to a group of rare immunodysregulatory diseases that primarily present in early childhood with variable multiorgan involvement. When untreated, patients with severe clinical phenotypes have a poor prognosis, and diagnosis and management of these patients can be challenging. However, approved treatments targeting the proinflammatory cytokine IL-1 have been life changing and have significantly improved patient outcomes. OBJECTIVE: To establish evidence-based recommendations for diagnosis, treatment and monitoring of patients with IL-1 mediated autoinflammatory diseases to standardise their management. METHODS: A multinational, multidisciplinary task force consisting of physician experts, including rheumatologists, patients or caregivers and allied healthcare professionals, was established. Evidence synthesis, including systematic literature review and expert consensus (Delphi) via surveys, was conducted. Consensus methodology was used to formulate and vote on statements to guide optimal patient care. RESULTS: The task force devised five overarching principles, 14 statements related to diagnosis, 10 on therapy, and nine focused on long-term monitoring that were evidence and/or consensus-based for patients with IL-1 mediated diseases. An outline was developed for disease-specific monitoring of inflammation-induced organ damage progression and reported treatments of CAPS, TRAPS, MKD and DIRA. CONCLUSION: The 2021 EULAR/American College of Rheumatology points to consider represent state-of-the-art knowledge based on published data and expert opinion to guide diagnostic evaluation, treatment and monitoring of patients with CAPS, TRAPS, MKD and DIRA, and to standardise and improve care, quality of life and disease outcomes.

Genetically programmed alternative splicing of NEMO mediates an autoinflammatory disease phenotype.

Host defense and inflammation are regulated by the NF-κB essential modulator (NEMO), a scaffolding protein with a broad immune cell and tissue expression profile. Hypomorphic mutations in inhibitor of NF-κB kinase regulatory subunit gamma (IKBKG) encoding NEMO typically present with immunodeficiency. Here, we characterized a pediatric autoinflammatory syndrome in 3 unrelated male patients with distinct X-linked IKBKG germline mutations that led to overexpression of a NEMO protein isoform lacking the domain encoded by exon 5 (NEMO-Δex5). This isoform failed to associate with TANK binding kinase 1 (TBK1), and dermal fibroblasts from affected patients activated NF-κB in response to TNF but not TLR3 or RIG-I-like receptor (RLR) stimulation when isoform levels were high. By contrast, T cells, monocytes, and macrophages that expressed NEMO-Δex5 exhibited increased NF-κB activation and IFN production, and blood cells from these patients expressed a strong IFN and NF-κB transcriptional signature. Immune cells and TNF-stimulated dermal fibroblasts upregulated the inducible IKK protein (IKKi) that was stabilized by NEMO-Δex5, promoting type I IFN induction and antiviral responses. These data revealed how IKBKG mutations that lead to alternative splicing of skipping exon 5 cause a clinical phenotype we have named NEMO deleted exon 5 autoinflammatory syndrome (NDAS), distinct from the immune deficiency syndrome resulting from loss-of-function IKBKG mutations.

Protein kinase R is an innate immune sensor of proteotoxic stress via accumulation of cytoplasmic IL-24.

Proteasome dysfunction can lead to autoinflammatory disease associated with elevated type I interferon (IFN-αß) and NF-κB signaling; however, the innate immune pathway driving this is currently unknown. Here, we identified protein kinase R (PKR) as an innate immune sensor for proteotoxic stress. PKR activation was observed in cellular models of decreased proteasome function and in multiple cell types from patients with proteasome-associated autoinflammatory disease (PRAAS). Furthermore, genetic deletion or small-molecule inhibition of PKR in vitro ameliorated inflammation driven by proteasome deficiency. In vivo, proteasome inhibitor-induced inflammatory gene transcription was blunted in PKR-deficient mice compared with littermate controls. PKR also acted as a rheostat for proteotoxic stress by triggering phosphorylation of eIF2α, which can prevent the translation of new proteins to restore homeostasis. Although traditionally known as a sensor of RNA, under conditions of proteasome dysfunction, PKR sensed the cytoplasmic accumulation of a known interactor, interleukin-24 (IL-24). When misfolded IL-24 egress into the cytosol was blocked by inhibition of the endoplasmic reticulum-associated degradation pathway, PKR activation and subsequent inflammatory signaling were blunted. Cytokines such as IL-24 are normally secreted from cells; therefore, cytoplasmic accumulation of IL-24 represents an internal danger-associated molecular pattern. Thus, we have identified a mechanism by which proteotoxic stress is detected, causing inflammation observed in the disease PRAAS.