Heterozygous OAS1 gain-of-function variants cause an autoinflammatory immunodeficiency

Structural basis for OAS2 regulation and its antiviral function

Oligoadenylate synthetase (OAS) proteins are immune sensors for double-stranded RNA and are critical for restricting viruses. OAS2 comprises two OAS domains, only one of which can synthesize 2'-5'-oligoadenylates for RNase L activation. Existing structures of OAS1 provide a model for enzyme activation, but they do not explain how multiple OAS domains discriminate RNA length. Here, we discover that human OAS2 exists in an auto-inhibited state as a zinc-mediated dimer and present a mechanism for RNA length discrimination: the catalytically deficient domain acts as a molecular ruler that prevents autoreactivity to short RNAs. We demonstrate that dimerization and myristoylation localize OAS2 to Golgi membranes and that this is required for OAS2 activation and the restriction of viruses that exploit the endomembrane system for replication, e.g., coronaviruses. Finally, our results highlight the non-redundant role of OAS proteins and emphasize the clinical relevance of OAS2 by identifying a patient with a loss-of-function mutation associated with autoimmune disease.

Multicystic Interstitial Lung Disease Due to a Novel Biallelic C-C Chemokine Receptor Type 2 Variant

OBJECTIVE

We are presenting two individuals with biallelic C-C chemokine receptor type 2 (CCR2) deficiency carrying the novel c.644C>T p.L215P variant, who presented with chronic respiratory symptoms during infancy and developed multiple diffuse cystic lesions during childhood.

METHODS

The patients were diagnosed by means of whole exome sequencing and functional validation of the variant was performed in primary patient cells.

RESULTS

While size and extent of the cysts were stable over years, progressive lung function decline was noted in adolescence and adulthood respectively. The CCR2 p.L215P variant was found to be loss-of-expression and patient monocytes displayed a migration defect upon stimulation with the CCR2 ligand C-C motif ligand 2 (CCL2).

CONCLUSION

With a follow-up of up to 25 years, this report expands our understanding of lung disease in CCR2 deficiency and offers another monogenic cause of cystic lung disease. Early genetic diagnosis of affected individuals might allow potentially curative treatment by haematopoietic stem cell transplantation.

Cell-Autonomous Immunity: From Cytosolic Sensing to Self-Defense

As an evolutionarily conserved and ubiquitous mechanism of host defense, non-immune cells in vertebrates possess the intrinsic ability to autonomously detect and combat intracellular pathogens. This process, termed cell-autonomous immunity, is distinct from classical innate immunity. In this review, we comprehensively examine the defense mechanisms employed by non-immune cells in response to intracellular pathogen invasion. We provide a detailed analysis of the cytosolic sensors that recognize aberrant nucleic acids, lipopolysaccharide (LPS), and other pathogen-associated molecular patterns (PAMPs). Specifically, we elucidate the molecular mechanisms underlying key signaling pathways, including the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway, the retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs)-mitochondrial antiviral signaling (MAVS) axis, and the guanylate-binding proteins (GBPs)-mediated pathway. Furthermore, we critically evaluate the involvement of these pathways in the pathogenesis of various diseases, including autoimmune disorders, inflammatory conditions, and malignancies, while highlighting their potential as therapeutic targets.

OAS cross-activates RNase L intercellularly through cell-to-cell transfer of 2-5A to spread innate immunity

The 2',5'-oligoadenylate synthetase (OAS)-RNase L pathway is a classical antiviral innate immune pathway. Upon sensing dsRNA, OAS produces 2',5'-oligoadenylate (2-5A) as a second messenger to activate RNase L. Whether 2-5A can be transported to extend the reach of innate immune signaling has not been established. Here, we showed that 2-5A was transferred from cell to cell through connexin (CX43/CX45) gap junctions. 2-5A was also transferred through importers and exporters, allowing OAS to remotely activate RNase L and protect neighboring cells from viral infection. We identified ABCC10 as a 2-5A exporter. Loss of ABCC10 had no effect on 2-5A production but reduced 2-5A export and protection of neighboring cells. Furthermore, OAShi tumors such as MC38 naturally produced 2-5A in vivo, which was secreted via ABCC10 to activate host-not tumor-RNase L-mediated antitumor response. Therefore, 2-5A is an immunotransmitter that mediates short-range communication between cells in infection and cancer.

2-5A is an immunotransmitter that fuels RNase L immunity

cGAS-cGAMP-STING and OAS-2-5A-RNase L are evolutionarily convergent innate immune pathways. cGAMP acts as an immunotransmitter; what about 2-5A? In this issue of Immunity, Huai et al. map the transfer of 2-5A between cells, establishing it as a bona fide immunotransmitter.

An update on diagnosis and treatments of childhood interstitial lung diseases

Childhood interstitial lung diseases (chILDs) are rare and heterogeneous disorders associated with significant morbidity and mortality. The clinical presentation of chILD typically includes chronic or recurrent respiratory signs and symptoms with diffuse radiographic abnormalities on chest imaging. Diagnosis requires a structured, multi-step approach. Treatment options are limited, with disease-specific therapies available only in selected cases and management relying primarily on supportive care. Awareness of chILDs has been steadily increasing. New diagnoses, advanced diagnostic tests, and novel treatments are emerging each year, highlighting the importance of collaborative, multidisciplinary teams in providing comprehensive care for children and families affected by these complex conditions. On behalf of the European Respiratory Society Clinical Research Collaboration for chILD (ERS CRC chILD-EU), this review provides an updated overview of the diagnostic approach and management strategies for chILDs.

Systematic Identification of Mitochondrial Signatures in Alzheimer's Disease and Inflammatory Bowel Disease

Mitochondrial dysfunction is increasingly recognized as a shared feature of Alzheimer's disease (AD) and inflammatory bowel disease (IBD), linked through overlapping pathways of hypoxia and immune dysregulation. Our study integrated transcriptomic and genetic analyses to uncover mitochondria-related mechanisms underlying these diseases. By analyzing multiple AD and IBD datasets through differential expression gene (DEG) analyses, biological pathway enrichment, and co-expression module construction, we identified hypoxia-induced mitochondrial dysfunction as a central risk factor for both conditions. Key findings revealed several mitochondrial-related genes shared between AD and IBD, including BCL6, PFKFB3, NDUFS3, and COX5B, which serve as critical regulators bridging mitochondrial and immune pathways. Drug enrichment analyses using Drug Signatures Database (DsigDB) and the Connectivity Map (cMAP) identified promising therapeutic candidates, including decitabine, DMOG, and estradiol, targeting shared regulators such as BCL6, PFKFB3, MAFF, and TGFBI. These drugs demonstrated potential to modulate mitochondrial autophagy and oxidative phosphorylation (OXPHOS), pathways enriched in the constructed interaction network with BCL6 and PFKFB3 as central nodes. Mendelian randomization (MR) analysis further identified MAP1LC3A as significantly associated with increased risk for both AD and IBD, while NME1 emerged as strongly protective, suggesting their roles as therapeutic targets. Our findings underscore hypoxia-induced mitochondrial dysfunction as a unifying mechanism in AD and IBD, mediated by hypoxia-inducible factor-1α (HIF-1α). By identifying key mitochondria-associated genes and pathways, this study highlights innovative therapeutic targets and contributes to a deeper understanding of the gut-brain interplay in neurodegeneration and chronic inflammation. These insights pave the way for precision medicine strategies targeting mitochondrial dysfunction in AD and IBD.

Large-scale cross-trait genetic analysis highlights shared genetic backgrounds of autoimmune diseases

Disorders associated with the immune system burden multiple organs, although the shared biology exists across the diseases. Preceding family-based studies reveal that immune diseases are heritable to varying degrees, providing the basis for immunogenomics. The recent cost reduction in genetic analysis intensively promotes biobank-scale studies and the development of frameworks for statistical genetics. The accumulating multi-layer omics data, including genome-wide association studies (GWAS) and RNA-sequencing at single-cell resolution, enable us to dissect the genetic backgrounds of immune-related disorders. Although autoimmune and allergic diseases are generally categorized into different disease categories, epidemiological studies reveal the high incidence of autoimmune and allergic disease complications, suggesting the shared genetics and biology between the disease categories. Biobank resources and consortia cover multiple immune-related disorders to accumulate phenome-wide associations of genetic variants and enhance researchers to analyze the shared and heterogeneous genetic backgrounds. The emerging post-GWAS and integrative multi-omics analyses provide genetic and biological insights into the multicategorical disease associations.

The Unusual Role of Ribonuclease L in Innate Immunity

Ribonuclease L is an endonuclease that is activated as part of the dsRNA-driven innate immune response. Active RNase L cleaves pathogenic RNAs as a way to eliminate infections. However, there are additional and unexpected ways that RNase L causes changes in the host that promote an immune response and contribute to its role in host defense. Central to these unconventional mechanisms is the observation that RNase L also degrades the mRNA of the host. In turn, mRNA fragments that RNase L generates can be translated. This causes activation of a ribosome collision sensor that leads to downstream signaling and cell death. Additionally, the liberation of RNA binding proteins after RNA decay appears to affect gene expression. In this review, we discuss these and other recent advances that focus on novel and unusual ways RNase L contributes to innate immunity.

Prognostic value and molecular mechanisms of OAS1 in lung adenocarcinoma

BACKGROUND

The expression of 2'-5'-oligoadenylate synthetase 1 (OAS1) in lung cancer has been validated in numerous studies. However, the prognostic value of OAS1 expression in lung adenocarcinoma (LUAD) still remains unclear. This study aimed to reveal the prognostic value and associated molecular mechanisms of OAS1 expression in LUAD.

METHODS

Gene expression data of LUAD were extracted from online databases. Gene and protein expression levels of OAS1 in LUAD and normal samples were revealed, followed by prognostic analysis of OAS1. Next, we conducted a thorough bioinformatics analysis to examine the enrichment of key functional and biological signaling pathways and their correlation with the abundance of immune cells. The independent prognoses, drug responses, and PPI networks associated with OAS1 were analyzed. OAS1 expression was evaluated in LUAD tissues and cell lines. OAS1 was knocked down by siRNA transfection, followed by CCK8, colony formation, and wound-healing assays.

RESULTS

Gene and protein expression levels of OAS1 in LUAD samples were significantly higher than those in normal samples (all P < 0.05). OAS1 stimulation were correlated with poor prognosis, lymph node metastasis, advanced tumor stage, immune cells, and immunomodulators. The prognostic value of OAS1 in LUAD was determined via univariate regression analysis. In total, 10 OAS1-associated genes were revealed via PPI analysis of OAS1, which were primarily enriched in functions, such as the negative regulation of viral genome replication. Transcriptional analysis revealed several OAS1-related interactions, including STAT3-miR-21-OAS1. STAT3 was overexpressed and miR-21 was expressed in LUAD cells. Upregulation of OAS1 protein was determined in LUAD tissues and cell lines. OAS1 knockdown significantly reduced proliferation and migration of LUAD cells.

CONCLUSIONS

OAS1 overexpression influenced survival and immune cell infiltration in patients with LUAD, which might be a potential prognostic gene for LUAD. Moreover, OAS1 contributed to LUAD progression by participating in STAT3-miR-21-OAS1 axis.

RNA helicase SKIV2L limits antiviral defense and autoinflammation elicited by the OAS-RNase L pathway

The OAS-RNase L pathway is one of the oldest innate RNA sensing pathways that leads to interferon (IFN) signaling and cell death. OAS recognizes viral RNA and then activates RNase L, which subsequently cleaves both cellular and viral RNA, creating "processed RNA" as an endogenous ligand that further triggers RIG-I-like receptor signaling. However, the IFN response and antiviral activity of the OAS-RNase L pathway are weak compared to other RNA-sensing pathways. Here, we discover that the SKIV2L RNA exosome limits the antiviral capacity of the OAS-RNase L pathway. SKIV2L-deficient cells exhibit remarkably increased interferon responses to RNase L-processed RNA, resulting in heightened antiviral activity. The helicase activity of SKIV2L is indispensable for this function, acting downstream of RNase L. SKIV2L depletion increases the antiviral capacity of OAS-RNase L against RNA virus infection. Furthermore, SKIV2L loss exacerbates autoinflammation caused by human OAS1 gain-of-function mutations. Taken together, our results identify SKIV2L as a critical barrier to OAS-RNase L-mediated antiviral immunity that could be therapeutically targeted to enhance the activity of a basic antiviral pathway.

New discoveries in the genetics and genomics of systemic juvenile idiopathic arthritis

INTRODUCTION

Systemic juvenile idiopathic arthritis (sJIA) is a severe inflammatory condition with onset in childhood. It is sporadic, but elements of its stereotypical innate immune responses are likely genetically encoded by both common variants with small effect sizes and rare variants with larger effects.

AREAS COVERED

Genomic investigations have defined the unique genetic architecture of sJIA. Identification of the class II HLA locus as the strongest sJIA risk factor for the first time brought attention to T lymphocytes and adaptive immune mechanisms in sJIA. The importance of the human leukocyte antigen (HLA) locus was reinforced by recognition that HLA-DRB1*15 alleles are strongly associated with development of drug reactions and sJIA-associated lung disease (sJIA-LD). At the IL1RN locus, genetic variation relates to both risk of sJIA and may also predict non-response to anakinra. Finally, rare genetic variants may have critical roles in disease complications, such as homozygous LACC1 mutations in families with an sJIA-like illness, and hemophagocytic lymphohistiocytosis (HLH) gene variants in some children with macrophage activation syndrome (MAS).

EXPERT OPINION

Genetic and genomic analysis of sJIA holds great promise for both basic discovery of the course and complications of sJIA, and may help guide personalized medicine and therapeutic decision-making.

Next-generation phenotyping integrated in a national framework for patients with ultrarare disorders improves genetic diagnostics and yields new molecular findings

Individuals with ultrarare disorders pose a structural challenge for healthcare systems since expert clinical knowledge is required to establish diagnoses. In TRANSLATE NAMSE, a 3-year prospective study, we evaluated a novel diagnostic concept based on multidisciplinary expertise in Germany. Here we present the systematic investigation of the phenotypic and molecular genetic data of 1,577 patients who had undergone exome sequencing and were partially analyzed with next-generation phenotyping approaches. Molecular genetic diagnoses were established in 32% of the patients totaling 370 distinct molecular genetic causes, most with prevalence below 1:50,000. During the diagnostic process, 34 novel and 23 candidate genotype-phenotype associations were identified, mainly in individuals with neurodevelopmental disorders. Sequencing data of the subcohort that consented to computer-assisted analysis of their facial images with GestaltMatcher could be prioritized more efficiently compared with approaches based solely on clinical features and molecular scores. Our study demonstrates the synergy of using next-generation sequencing and phenotyping for diagnosing ultrarare diseases in routine healthcare and discovering novel etiologies by multidisciplinary teams.

Human life within a narrow range: The lethal ups and downs of type I interferons

The past 20 years have seen the definition of human monogenic disorders and their autoimmune phenocopies underlying either defective or enhanced type I interferon (IFN) activity. These disorders delineate the impact of type I IFNs in natural conditions and demonstrate that only a narrow window of type I IFN activity is beneficial. Insufficient type I IFN predisposes humans to life-threatening viral diseases (albeit unexpectedly few) with a central role in immunity to respiratory and cerebral viral infection. Excessive type I IFN, perhaps counterintuitively, appears to underlie a greater number of autoinflammatory and/or autoimmune conditions known as type I interferonopathies, whose study has revealed multiple molecular programs involved in the induction of type I IFN signaling. These observations suggest that the manipulation of type I IFN activity to within a physiological range may be clinically relevant for the prevention and treatment of viral and inflammatory diseases.

Endonucleolytic RNA cleavage drives changes in gene expression during the innate immune response

Viral infection triggers several double-stranded RNA (dsRNA) sensors that lead to changes in gene expression in the cell. One of these sensors activates an endonuclease, ribonuclease L (RNase L), that cleaves single-stranded RNA. However, how the resultant widespread RNA fragmentation affects gene expression is not fully understood. Here, we show that this fragmentation induces the ribotoxic stress response via ZAKα, potentially through stalled ribosomes and/or ribosome collisions. The p38 and JNK pathways that are activated as part of this response promote outcomes that inhibit the virus, such as programmed cell death. We also show that RNase L limits the translation of stress-responsive genes. Intriguingly, we found that the activity of the generic endonuclease, RNase A, recapitulates many of the same molecular phenotypes as activated RNase L, demonstrating how widespread RNA cleavage can evoke an antiviral program.

A roadmap to precision treatments for familial pulmonary fibrosis

Interstitial lung diseases (ILDs) in adults and children (chILD) are a heterogeneous group of lung disorders leading to inflammation, abnormal tissue repair and scarring of the lung parenchyma often resulting in respiratory failure and death. Inherited factors directly cause, or contribute significantly to the risk of developing ILD, so called familial pulmonary fibrosis (FPF), and monogenic forms may have a poor prognosis and respond poorly to current treatments. Specific, variant-targeted or precision treatments are lacking. Clinical trials of repurposed drugs, anti-fibrotic medications and specific treatments are emerging but for many patients no interventions exist. We convened an expert working group to develop an overarching framework to address the existing research gaps in basic, translational, and clinical research and identified areas for future development of preclinical models, candidate medications and innovative clinical trials. In this Position Paper, we summarise working group discussions, recommendations, and unresolved questions concerning precision treatments for FPF.

Innate immune responses to RNA: sensing and signaling

Nucleic acids are among the most essential PAMPs (pathogen-associated molecular patterns). Animals have evolved numerous sensors to recognize nucleic acids and trigger immune signaling against pathogen replication, cellular stress and cancer. Many sensor proteins (e.g., cGAS, AIM2, and TLR9) recognize the molecular signature of infection or stress and are responsible for the innate immune response to DNA. Remarkably, recent evidence demonstrates that cGAS-like receptors acquire the ability to sense RNA in some forms of life. Compared with the nucleic-acid sensing by cGAS, innate immune responses to RNA are based on various RNA sensors, including RIG-I, MDA5, ADAR1, TLR3/7/8, OAS1, PKR, NLRP1/6, and ZBP1, via a broad-spectrum signaling axis. Importantly, new advances have brought to light the potential clinical application of targeting these signaling pathways. Here, we highlight the latest discoveries in the field. We also summarize the activation and regulatory mechanisms of RNA-sensing signaling. In addition, we discuss how RNA sensing is tightly controlled in cells and why the disruption of immune homeostasis is linked to disease.

Cellular models in autoinflammatory disease research

Systemic autoinflammatory diseases are a heterogeneous group of rare genetic disorders caused by dysregulation of the innate immune system. Understanding the complex mechanisms underlying these conditions is critical for developing effective treatments. Cellular models are essential for identifying new conditions and studying their pathogenesis. Traditionally, these studies have used primary cells and cell lines of disease-relevant cell types, although newer induced pluripotent stem cell (iPSC)-based models might have unique advantages. In this review, we discuss the three cellular models used in autoinflammatory disease research, their strengths and weaknesses, and their applications to inform future research in the field.

[Lung involvement in autoinflammatory diseases]

Genetic autoinflammatory diseases are now a recognized and rapidly expanding group. The lung involvement historically associated with autoinflammatory diseases is inflammatory seritis, primarily seen in familial Mediterranean fever and other interleukin-1 mediated diseases. Over the last ten years, pulmonary involvement has been the core presentation of two autoinflammatory diseases associated with constitutive type I interferon activation, i.e. SAVI and COPA syndrome. Most patients with these diseases usually develop early progression to pulmonary fibrosis, which is responsible for high rates of morbidity and mortality. Other rare autoinflammatory diseases are associated with alveolar proteinosis, particularly when related to MARS mutations. Additionally, in adults, VEXAS is frequently associated with pulmonary involvement, albeit without prognosis effect. A molecular approach to autoinflammatory diseases enables not only the definition of biomarkers for diagnosis, but also the identification of targeted treatments. Examples include JAK inhibitors in SAVI and COPA syndrome, even though this therapy does not prevent progression to pulmonary fibrosis. Another illustrative example is the efficacy of methionine supplementation in alveolar proteinosis linked to MARS mutations. Overall, in autoinflammatory diseases the lung is now emerging as a possible affected organ. Continuing discovery of new autoinflammatory diseases is likely to uncover further pathologies involving the lung. Such advances are expected to lead to the development of novel therapeutic perspectives.

How to Build a Fire: The Genetics of Autoinflammatory Diseases

Systemic autoinflammatory diseases (SAIDs) are a heterogeneous group of disorders caused by excess activation of the innate immune system in an antigen-independent manner. Starting with the discovery of the causal gene for familial Mediterranean fever, more than 50 monogenic SAIDs have been described. These discoveries, paired with advances in immunology and genomics, have allowed our understanding of these diseases to improve drastically in the last decade. The genetic causes of SAIDs are complex and include both germline and somatic pathogenic variants that affect various inflammatory signaling pathways. We provide an overview of the acquired SAIDs from a genetic perspective and summarize the clinical phenotypes and mechanism(s) of inflammation, aiming to provide a comprehensive understanding of the pathogenesis of autoinflammatory diseases.

C-terminal variants in CDC42 drive type I interferon-dependent autoinflammation in NOCARH syndrome reversible by ruxolitinib

C-terminal variants in CDC42 encoding cell division control protein 42 homolog underlie neonatal-onset cytopenia, autoinflammation, rash, and hemophagocytic lymphohistiocytosis (NOCARH). Pyrin inflammasome hyperactivation has been shown to contribute to disease pathophysiology. However, mortality of NOCARH patients remains high despite inflammasome-focused treatments. Here, we demonstrate in four NOCARH patients from three families that cell-intrinsic activation of type I interferon (IFN) is a previously unrecognized driver of autoinflammation in NOCARH. Our data show that aberrant innate immune activation is caused by sensing of cytosolic nucleic acids released from mitochondria, which exhibit disturbances in integrity and dynamics due to CDC42 dysfunction. In one of our patients, treatment with the Janus kinase inhibitor ruxolitinib led to complete remission, indicating that inhibition of type I IFN signaling may have an important role in the management of autoinflammation in patients with NOCARH.

Investigation of immune-related diseases using patient-derived induced pluripotent stem cells

The precise pathogenesis of immune-related diseases remains unclear, and new effective therapeutic choices are required for the induction of remission or cure in these diseases. Basic research utilizing immune-related disease patient-derived induced pluripotent stem (iPS) cells is expected to be a promising platform for elucidating the pathogenesis of the diseases and for drug discovery. Since autoinflammatory diseases are usually monogenic, genetic mutations affect the cell function and patient-derived iPS cells tend to exhibit disease-specific phenotypes. In particular, iPS cell-derived monocytic cells and macrophages can be used for functional experiments, such as inflammatory cytokine production, and are often employed in research on patients with autoinflammatory diseases.On the other hand, the utilization of disease-specific iPS cells is less successful for research on autoimmune diseases. One reason for this is that autoimmune diseases are usually polygenic, which makes it challenging to determine which factors cause the phenotypes of patient-derived iPS cells are caused by. Another reason is that protocols for differentiating some lymphocytes associated with autoimmunity, such as CD4+T cells or B cells, from iPS cells have not been well established. Nevertheless, several groups have reported studies utilizing autoimmune disease patient-derived iPS cells, including patients with rheumatoid arthritis, systemic lupus erythematosus (SLE), and systemic sclerosis. Particularly, non-hematopoietic cells, such as fibroblasts and cardiomyocytes, differentiated from autoimmune patient-derived iPS cells have shown promising results for further research into the pathogenesis. Recently, our groups established a method for differentiating dendritic cells that produce interferon-alpha, which can be applied as an SLE pathological model. In summary, patient-derived iPS cells can provide a promising platform for pathological research and new drug discovery in the field of immune-related diseases.

Multi-omics analysis reveals interferon-stimulated gene OAS1 as a prognostic and immunological biomarker in pan-cancer

Introduction

OAS1(2'-5'-oligoadenylate synthetase 1) is a member of the Interferon-Stimulated Genes which plays an important role in the antiviral process. In recent years, the role of OAS1 in tumors has attracted attention, and it was found to be associated with prognosis in several tumors. However, the mechanism by which OAS1 affects tumors is unclear and pan-cancer study of OAS1 is necessary to better understand its implication in cancers.

Methods

The expression, prognostic value, genetic alteration, alternative splicing events of OAS1 in pan-cancers were analyzed using TCGA, GTEx, HPA, GEPIA and OncoSplicing databases. OAS1 associated immune cell infiltration was evaluated using the ESTIMATE, xCell, CIBERSORT and QUANTISEQ algorithm. Single cell transcriptome data download using TISH database. Finally, the roles of the OAS1 on apoptosis, migration and invasion were investigated in two pancreatic cancer cells.

Results

Our results revealed significant differences in OAS1 expression among various tumors, which had prognostic implications. In addition, we investigated the impact of OAS1 on genomic stability, methylation status, and other factors across different types of cancer, and the effects of these factors on prognosis. Notably, our study also demonstrated that OAS1 overexpression can contribute to CTL dysfunction and macrophage M2 polarization. In addition, cell experiments showed that the knockdown of OAS1 could reduce the invasive ability and increased the apoptosis rate of PAAD cells.

Discussion

These results confirmed that OAS1 could be a prognostic biomarker and therapeutic target for its potential role in CTL dysfunction and macrophage M2 polarization.

Endonucleolytic RNA cleavage drives changes in gene expression during the innate immune response

Viral infection triggers several dsRNA sensors that lead to changes in gene expression in the cell. One of these sensors activates an endonuclease, RNase L, that cleaves single stranded RNA. However, how the resultant widespread RNA fragmentation affects gene expression is not fully understood. Here we show that this fragmentation induces the Ribotoxic Stress Response via ZAKα, potentially through ribosome collisions. The p38 and JNK pathways that are activated as part of this response promote outcomes that inhibit the virus, such as programmed cell death. We also show that RNase L limits the translation of stress-responsive genes, including antiviral IFIT mRNAs and GADD34 that encodes an antagonist of the Integrated Stress Response. Intriguingly, we found the activity of the generic endonuclease, RNase A, recapitulates many of the same molecular phenotypes as activated RNase L, demonstrating how widespread RNA cleavage can evoke an antiviral program.

Pan-cancer analysis identified OAS1 as a potential prognostic biomarker for multiple tumor types

Background

2',5'-oligoadenylate synthetase 1 (OAS1), has been reported as a tumor driver gene in breast carcinoma and pancreatic carcinoma. However, the role of OAS1 in most tumors has not been reported.

Methods

The original data of 35 tumor types were down load from the TCGA (The Cancer Genome Atlas) database and Human Protein Atlas (HPA) database. TIMER2, Kmplot, UALCAN, and TISIDB tools were used to investigate the expression and function of OAS1, and the role of OAS1 in prognosis, diagnostic value, and immune characteristics of pan-cancer. LUAD and PRAD cell lines, A549, H1975, PC-3 and C4-2 were utilized to perform cell function tests.

Results

OAS1 expression was up-regulated in 12 tumor types and down-regulated in 2 tumor types. High OAS1 expression was correlated with poor prognosis in 6 tumor types, while high OAS1 expression was correlated with good prognosis in 2 tumor types. OAS1 was correlated with molecular subtypes in 8 tumor types and immune subtypes in 12 tumor types. OAS1 was positively associated with the expression of numerous immune checkpoint genes and tumor mutational burden (TMB). OAS1 had potential diagnostic value in 15 tumor types. Silence of OAS1 significantly inhibited the cell proliferation ability, and promoted G2/M cell cycle arrest of LUAD and PRAD cells. Meanwhile, silence of OAS1 enhanced cisplatin-induced apoptosis of LUAD and PRAD cells, but weakened cell migration.

Conclusion

This pan-cancer study suggests that OAS1can be used as a molecular biomarker for prognosis in pan-cancer and may play an important role in tumor immune response.

Human genetic and immunological determinants of SARS-CoV-2 and Epstein-Barr virus diseases in childhood: Insightful contrasts

There is growing evidence to suggest that severe disease in children infected with common viruses that are typically benign in other children can result from inborn errors of immunity or their phenocopies. Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a cytolytic respiratory RNA virus, can lead to acute hypoxemic COVID-19 pneumonia in children with inborn errors of type I interferon (IFN) immunity or autoantibodies against IFNs. These patients do not appear to be prone to severe disease during infection with Epstein-Barr virus (EBV), a leukocyte-tropic DNA virus that can establish latency. By contrast, various forms of severe EBV disease, ranging from acute hemophagocytosis to chronic or long-term illnesses, such as agammaglobulinemia and lymphoma, can manifest in children with inborn errors disrupting specific molecular bridges involved in the control of EBV-infected B cells by cytotoxic T cells. The patients with these disorders do not seem to be prone to severe COVID-19 pneumonia. These experiments of nature reveal surprising levels of redundancy of two different arms of immunity, with type I IFN being essential for host defense against SARS-CoV-2 in respiratory epithelial cells, and certain surface molecules on cytotoxic T cells essential for host defense against EBV in B lymphocytes.

Multi-phasic gene profiling using candidate gene approach predict the capacity of specific antibody production and maintenance following COVID-19 vaccination in Japanese population

Background

Vaccination against severe acute respiratory syndrome coronavirus type 2 is highly effective in preventing infection and reducing the severity of coronavirus disease (COVID-19). However, acquired humoral immunity wanes within six months. Focusing on the different tempo of acquisition and attenuation of specific antibody titers in individuals, we investigated the impact of genetic polymorphisms on antibody production after COVID-19 vaccination.

Methods

In total 236 healthcare workers from a Japanese municipal hospital, who received two doses of the vaccine were recruited. We employed a candidate gene approach to identify the target genetic polymorphisms affecting antibody production after vaccination. DNA samples from the study populations were genotyped for 33 polymorphisms in 15 distinct candidate genes encoding proteins involved in antigen-presenting cell activation, T cell activation, T-B interaction, and B cell survival. We measured total anti-SARS-Cov2 spike IgG antibody titers and analyzed the association with genetic polymorphisms at several time points after vaccination using an unbiased statistical method, and stepwise logistic regression following multivariate regression.

Results

Significant associations were observed between seven SNPs in NLRP3, OAS1, IL12B, CTLA4, and IL4, and antibody titers at 3 weeks after the first vaccination as an initial response. Six SNPs in NLRP3, TNF, OAS1, IL12B, and CTLA4 were associated with high responders with serum antibody titer > 4000 BAU/ml as boosting effect at 3 weeks after the second vaccination. Analysis of long-term maintenance showed the significance of the three SNPs in IL12B, IL7R, and MIF for the maintenance of antibody titers and that in BAFF for attenuation of neutralizing antibodies. Finally, we proposed a predictive model composed of gene profiles to identify the individuals with rapid antibody attenuation by receiver operating characteristic (ROC) analysis (area under the curve (AUC)= 0.76, sensitivity = 82.5%, specificity=67.8%).

Conclusions

The candidate gene approach successfully showed shifting responsible gene profiles and initial and boosting effect mainly related to the priming phase into antibody maintenance including B cell survival, which traces the phase of immune reactions. These gene profiles provide valuable information for further investigation of humoral immunity against COVID-19 and for building a strategy for personalized vaccine schedules.

Inborn Errors of Immunity and Autoimmune Disease

Autoimmunity may be a manifestation of inborn errors of immunity, specifically as part of the subgroup of primary immunodeficiency known as primary immune regulatory disorders. However, although making a single gene diagnosis can have important implications for prognosis and management, picking patients to screen can be difficult, against a background of a high prevalence of autoimmune disease in the population. This review compares the genetics of common polygenic and rare monogenic autoimmunity, and explores the molecular mechanisms, phenotypes, and inheritance of autoimmunity associated with primary immune regulatory disorders, highlighting the emerging importance of gain-of-function and non-germline somatic mutations. A novel framework for identifying rare monogenic cases of common diseases in children is presented, highlighting important clinical and immunologic features that favor single gene disease and guides clinicians in selecting appropriate patients for genomic screening. In addition, there will be a review of autoimmunity in non-genetically defined primary immunodeficiency such as common variable immunodeficiency, and of instances where primary autoimmunity can result in clinical phenocopies of inborn errors of immunity.

Activation of cytosolic RNA sensors by endogenous ligands: roles in disease pathogenesis

Early detection of infection is a central and critical component of our innate immune system. Mammalian cells have developed specialized receptors that detect RNA with unusual structures or of foreign origin - a hallmark of many virus infections. Activation of these receptors induces inflammatory responses and an antiviral state. However, it is increasingly appreciated that these RNA sensors can also be activated in the absence of infection, and that this 'self-activation' can be pathogenic and promote disease. Here, we review recent discoveries in sterile activation of the cytosolic innate immune receptors that bind RNA. We focus on new aspects of endogenous ligand recognition uncovered in these studies, and their roles in disease pathogenesis.

Humans with inherited MyD88 and IRAK-4 deficiencies are predisposed to hypoxemic COVID-19 pneumonia

X-linked recessive deficiency of TLR7, a MyD88- and IRAK-4-dependent endosomal ssRNA sensor, impairs SARS-CoV-2 recognition and type I IFN production in plasmacytoid dendritic cells (pDCs), thereby underlying hypoxemic COVID-19 pneumonia with high penetrance. We report 22 unvaccinated patients with autosomal recessive MyD88 or IRAK-4 deficiency infected with SARS-CoV-2 (mean age: 10.9 yr; 2 mo to 24 yr), originating from 17 kindreds from eight countries on three continents. 16 patients were hospitalized: six with moderate, four with severe, and six with critical pneumonia, one of whom died. The risk of hypoxemic pneumonia increased with age. The risk of invasive mechanical ventilation was also much greater than in age-matched controls from the general population (OR: 74.7, 95% CI: 26.8-207.8, P < 0.001). The patients' susceptibility to SARS-CoV-2 can be attributed to impaired TLR7-dependent type I IFN production by pDCs, which do not sense SARS-CoV-2 correctly. Patients with inherited MyD88 or IRAK-4 deficiency were long thought to be selectively vulnerable to pyogenic bacteria, but also have a high risk of hypoxemic COVID-19 pneumonia.

Triple immune modulator therapy for aberrant hyperinflammatory responses in severe COVID-19

A dysregulated hyperinflammatory response is a key pathogenesis of severe COVID-19, but optimal immune modulator treatment has not been established. To evaluate the clinical effectiveness of double (glucocorticoids and tocilizumab) and triple (plus baricitinib) immune modulator therapy for severe COVID-19, a retrospective cohort study was conducted. For the immunologic investigation, a single-cell RNA sequencing analysis was performed in serially collected PBMCs and neutrophil specimens. Triple immune modulator therapy was a significant factor in a multivariable analysis for 30-day recovery. In the scRNA-seq analysis, type I and II IFN response-related pathways were suppressed by GC, and the IL-6-associated signature was additionally downregulated by TOC. Adding BAR to GC and TOC distinctly downregulated the ISGF3 cluster. Adding BAR also regulated the pathologically activated monocyte and neutrophil subpopulation induced by aberrant IFN signals. Triple immune modulator therapy in severe COVID-19 improved 30-day recovery through additional regulation of the aberrant hyperinflammatory immune response.

Diagnostic workup of childhood interstitial lung disease

Childhood interstitial lung diseases (chILDs) are rare and heterogeneous diseases with significant morbidity and mortality. An accurate and quick aetiological diagnosis may contribute to better management and personalised treatment. On behalf of the European Respiratory Society Clinical Research Collaboration for chILD (ERS CRC chILD-EU), this review summarises the roles of the general paediatrician, paediatric pulmonologists and expert centres in the complex diagnostic workup. Each patient's aetiological chILD diagnosis must be reached without prolonged delays in a stepwise approach from medical history, signs, symptoms, clinical tests and imaging, to advanced genetic analysis and specialised procedures including bronchoalveolar lavage and biopsy, if necessary. Finally, as medical progress is fast, the need to revisit a diagnosis of "undefined chILD" is stressed.

Inborn errors of OAS-RNase L in SARS-CoV-2-related multisystem inflammatory syndrome in children

Multisystem inflammatory syndrome in children (MIS-C) is a rare and severe condition that follows benign COVID-19. We report autosomal recessive deficiencies of OAS1, OAS2, or RNASEL in five unrelated children with MIS-C. The cytosolic double-stranded RNA (dsRNA)-sensing OAS1 and OAS2 generate 2'-5'-linked oligoadenylates (2-5A) that activate the single-stranded RNA-degrading ribonuclease L (RNase L). Monocytic cell lines and primary myeloid cells with OAS1, OAS2, or RNase L deficiencies produce excessive amounts of inflammatory cytokines upon dsRNA or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) stimulation. Exogenous 2-5A suppresses cytokine production in OAS1-deficient but not RNase L-deficient cells. Cytokine production in RNase L-deficient cells is impaired by MDA5 or RIG-I deficiency and abolished by mitochondrial antiviral-signaling protein (MAVS) deficiency. Recessive OAS-RNase L deficiencies in these patients unleash the production of SARS-CoV-2-triggered, MAVS-mediated inflammatory cytokines by mononuclear phagocytes, thereby underlying MIS-C.

Human CARMIL2 deficiency underlies a broader immunological and clinical phenotype than CD28 deficiency

Patients with inherited CARMIL2 or CD28 deficiency have defective T cell CD28 signaling, but their immunological and clinical phenotypes remain largely unknown. We show that only one of three CARMIL2 isoforms is produced and functional across leukocyte subsets. Tested mutant CARMIL2 alleles from 89 patients and 52 families impair canonical NF-κB but not AP-1 and NFAT activation in T cells stimulated via CD28. Like CD28-deficient patients, CARMIL2-deficient patients display recalcitrant warts and low blood counts of CD4+ and CD8+ memory T cells and CD4+ TREGs. Unlike CD28-deficient patients, they have low counts of NK cells and memory B cells, and their antibody responses are weak. CARMIL2 deficiency is fully penetrant by the age of 10 yr and is characterized by numerous infections, EBV+ smooth muscle tumors, and mucocutaneous inflammation, including inflammatory bowel disease. Patients with somatic reversions of a mutant allele in CD4+ T cells have milder phenotypes. Our study suggests that CARMIL2 governs immunological pathways beyond CD28.

Isolation and characterization of the mink interferon-epsilon gene and its antiviral activity

The interferon (IFN) response is the first line of defense against viral invasion and thus plays a central role in the regulation of the immune response. IFN-epsilon (IFN-ε) is a newly discovered type I IFN that does not require viral induction, unlike other type I IFNs. IFN-ε is constitutively expressed in epithelial cells and plays an important role in mucosal immunity. In this study, we evaluated the biological activity of the mink-IFN (MiIFN)-ε gene in prokaryotic cells. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to evaluate IFN-ε expression in different mink tissues. MiIFN-ε was highly expressed in brain, lung, tracheal, kidney, intestinal, bladder, ovarian, and testis tissues. There was no significant difference in MiIFN-ε expression between female and male minks, except in the reproductive system. Expression of the small ubiquitin-like modifier (SUMO3)-MiIFN-ε fusion gene was induced by isopropylβ-d-thiogalactoside, and MiIFN-ε was collected after SUMO-specific protease digestion. We tested the antiviral activity of MiIFN-ε against vesicular stomatitis virus (VSV) in epithelial cells of feline kidney 81 (F81). We used qRT-PCR to analyze the expression of several IFN-stimulated genes (ISGs), including ISG15, 2'-5' oligoadenylate synthetase (2'-5'OAS1), and myxovirus resistance protein 1 (Mx1). Recombinant IFN-ε induced high ISG expression in F81 cells. Compared with those in the cell control group, expressions of ISG15, Mx1, and 2'-5' OAS1 in the VSV-GFP control, IFN-ε, and MiIFN-ε-inhibited VSV-GFP groups were significantly increased. Compared with those in the VSV-GFP control group, expressions of ISG15 and 2'-5' OAS1 in the IFN-ε and MiIFN-ε-inhibited VSV-GFP groups were significantly increased, and the differences were highly significant (p < 0.0001). IFN-ε played an indirect antiviral role. These findings lay the foundation for detailed investigation of IFN-ε in the future.

Break down the barriers of auto-inflammation: How to deal with a monogenic auto-inflammatory disease and immuno-haematological features in 2022?

In the past few years, the spectrum of monogenic systemic auto-inflammatory diseases (MSAID) has widely expanded beyond the typical recurrent fever. Immuno-haematological features, as cytopenias, hypogammaglobulinemia, hypereosinophilia, lymphoproliferation and immunodeficiency, have been described in association of several MSAID. The objective of this review was to describe these particular MSAID. MSAID must be suspected in front of immuno-haematological features associated with non-infectious recurrent fever, chronic systemic inflammation, inflammatory cutaneous manifestations, arthritis or inflammatory bowel disease. Genes and cellular mechanisms involved are various but some of them are of special interest. Defects in actine regulation pathway are notably associated with cytopenia and immune deficiency. Because of their frequency, ADA2 deficiency and Vacuoles, E1-Enzyme, X-linked, auto-inflammatory, Somatic (VEXAS) syndrome deserve to be noticed. ADA2 deficiency results in polyarteritis nodosa-like presentation with a wide panel of manifestations including cytopenia(s), lymphoproliferation and immune deficiency. Neutrophilic dermatosis or chondritis associated with macrocytic anaemia or myelodysplasia should lead to screen for VEXAS. Of note, most of MSAID are associated with inflammatory anaemia. We proposed here a clinical and pragmatic approach of MSAID associated with immuno-haematological features.

Interstitial Lung Disease in Immunocompromised Children

BACKGROUND

The range of pulmonary complications beyond infections in pediatric immunocompromised patients is broad but not well characterized. Our goal was to assess the spectrum of disorders with a focus on interstitial lung diseases (ILD) in immunodeficient patients.

METHODS

We reviewed 217 immunocompromised children attending a specialized pneumology service during a period of 23 years. We assigned molecular diagnoses where possible and categorized the underlying immunological conditions into inborn errors of immunity or secondary immunodeficiencies according to the IUIS and the pulmonary conditions according to the chILD-EU classification system.

RESULTS

Among a wide array of conditions, opportunistic and chronic infections were the most frequent. ILD had a 40% prevalence. Of these children, 89% had a CT available, and 66% had a lung biopsy, which supported the diagnosis of ILD in 95% of cases. Histology was often lymphocyte predominant with the histo-pattern of granulomatous and lymphocytic interstitial lung disease (GLILD), follicular bronchiolitis or lymphocytic interstitial pneumonitis. Of interest, DIP, PAP and NSIP were also diagnosed. ILD was detected in several immunological disorders not yet associated with ILD.

CONCLUSIONS

Specialized pneumological expertise is necessary to manage the full spectrum of respiratory complications in pediatric immunocompromised patients.

The shared biomarkers and pathways of systemic lupus erythematosus and metabolic syndrome analyzed by bioinformatics combining machine learning algorithm and single-cell sequencing analysis

Background

Systemic lupus erythematosus (SLE) is one of the most prevalent systemic autoimmune diseases, and metabolic syndrome (MetS) is the most common metabolic disorder that contains hypertension, dyslipidemia, and obesity. Despite clinical evidence suggested potential associations between SLE and MetS, the underlying pathogenesis is yet unclear.

Methods

The microarray data sets of SLE and MetS were obtained from the Gene Expression Omnibus (GEO) database. To identify the shared genes between SLE and MetS, the Differentially Expressed Genes (DEGs) analysis and the weighted gene co-expression network analysis (WGCNA) were conducted. Then, the GO and KEGG analyses were performed, and the protein-protein interaction (PPI) network was constructed. Next, Random Forest and LASSO algorithms were used to screen shared hub genes, and a diagnostic model was built using the machine learning technique XG-Boost. Subsequently, CIBERSORT and GSVA were used to estimate the correlation between shared hub genes and immune infiltration as well as metabolic pathways. Finally, the significant hub genes were verified using single-cell RNA sequencing (scRNA-seq) data.

Results

Using limma and WGCNA, we identified 153 shared feature genes, which were enriched in immune- and metabolic-related pathways. Further, 20 shared hub genes were screened and successfully used to build a prognostic model. Those shared hub genes were associated with immunological and metabolic processes in peripheral blood. The scRNA-seq results verified that TNFSF13B and OAS1, possessing the highest diagnostic efficacy, were mainly expressed by monocytes. Additionally, they showed positive correlations with the pathways for the metabolism of xenobiotics and cholesterol, both of which were proven to be active in this comorbidity, and shown to be concentrated in monocytes.

Conclusion

This study identified shared hub genes and constructed an effective diagnostic model in SLE and MetS. TNFSF13B and OAS1 had a positive correlation with cholesterol and xenobiotic metabolism. Both of these two biomarkers and metabolic pathways were potentially linked to monocytes, which provides novel insights into the pathogenesis and combined therapy of SLE comorbidity with MetS.

2-5A-Mediated decay (2-5AMD): from antiviral defense to control of host RNA

Mammalian cells are exquisitely sensitive to the presence of double-stranded RNA (dsRNA), a molecule that they interpret as a signal of viral presence requiring immediate attention. Upon sensing dsRNA cells activate the innate immune response, which involves transcriptional mechanisms driving inflammation and secretion of interferons (IFNs) and interferon-stimulated genes (ISGs), as well as synthesis of RNA-like signaling molecules comprised of three or more 2'-5'-linked adenylates (2-5As). 2-5As were discovered some forty years ago and described as IFN-induced inhibitors of protein synthesis. The efforts of many laboratories, aimed at elucidating the molecular mechanism and function of these mysterious RNA-like signaling oligonucleotides, revealed that 2-5A is a specific ligand for the kinase-family endonuclease RNase L. RNase L decays single-stranded RNA (ssRNA) from viruses and mRNAs (as well as other RNAs) from hosts in a process we proposed to call 2-5A-mediated decay (2-5AMD). During recent years it has become increasingly recognized that 2-5AMD is more than a blunt tool of viral RNA destruction, but a pathway deeply integrated into sensing and regulation of endogenous RNAs. Here we present an overview of recently emerged roles of 2-5AMD in host RNA regulation.

Implicating effector genes at COVID-19 GWAS loci using promoter-focused Capture-C in disease-relevant immune cell types

BACKGROUND

SARS-CoV-2 infection results in a broad spectrum of COVID-19 disease, from mild or no symptoms to hospitalization and death. COVID-19 disease severity has been associated with some pre-existing conditions and the magnitude of the adaptive immune response to SARS-CoV-2, and a recent genome-wide association study (GWAS) of the risk of critical illness revealed a significant genetic component. To gain insight into how human genetic variation attenuates or exacerbates disease following SARS-CoV-2 infection, we implicated putatively functional COVID risk variants in the cis-regulatory landscapes of human immune cell types with established roles in disease severity and used high-resolution chromatin conformation capture to map these disease-associated elements to their effector genes.

RESULTS

This functional genomic approach implicates 16 genes involved in viral replication, the interferon response, and inflammation. Several of these genes (PAXBP1, IFNAR2, OAS1, OAS3, TNFAIP8L1, GART) were differentially expressed in immune cells from patients with severe versus moderate COVID-19 disease, and we demonstrate a previously unappreciated role for GART in T cell-dependent antibody-producing B cell differentiation in a human tonsillar organoid model.

CONCLUSIONS

This study offers immunogenetic insight into the basis of COVID-19 disease severity and implicates new targets for therapeutics that limit SARS-CoV-2 infection and its resultant life-threatening inflammation.

COVID-19 2022 update: transition of the pandemic to the endemic phase

COVID-19, which is caused by the SARS-CoV-2, has ravaged the world for the past 2 years. Here, we review the current state of research into the disease with focus on its history, human genetics and genomics and the transition from the pandemic to the endemic phase. We are particularly concerned by the lack of solid information from the initial phases of the pandemic that highlighted the necessity for better preparation to face similar future threats. On the other hand, we are gratified by the progress into human genetic susceptibility investigations and we believe now is the time to explore the transition from the pandemic to the endemic phase. The latter will require worldwide vigilance and cooperation, especially in emerging countries. In the transition to the endemic phase, vaccination rates have lagged and developed countries should assist, as warranted, in bolstering vaccination rates worldwide. We also discuss the current status of vaccines and the outlook for COVID-19.

Induced Pluripotent Stem Cell-Derived Monocytes/Macrophages in Autoinflammatory Diseases

The concept of autoinflammation, first proposed in 1999, refers to a seemingly unprovoked episode of sterile inflammation manifesting as unexplained fever, skin rashes, and arthralgia. Autoinflammatory diseases are caused mainly by hereditary abnormalities of innate immunity, without the production of autoantibodies or autoreactive T cells. The revolutionary discovery of induced pluripotent stem cells (iPSCs), whereby a patient’s somatic cells can be reprogrammed into an embryonic pluripotent state by forced expression of a defined set of transcription factors, has the transformative potential to enable in vitro disease modeling and drug candidate screening, as well as to provide a resource for cell replacement therapy. Recent reports demonstrate that recapitulating a disease phenotype in vitro is feasible for numerous monogenic diseases, including autoinflammatory diseases. In this review, we provide a comprehensive overview of current advances in research into autoinflammatory diseases involving iPSC-derived monocytes/macrophages. This review may aid in the planning of new studies of autoinflammatory diseases.

Role of helical structure and dynamics in oligoadenylate synthetase 1 (OAS1) mismatch tolerance and activation by short dsRNAs

The 2'-5'-oligoadenylate synthetases (OAS) are innate immune sensors of cytosolic double-stranded RNA (dsRNA) that play a critical role in limiting viral infection. How these proteins are able to avoid aberrant activation by cellular RNAs is not fully understood, but adenosine-to-inosine (A-to-I) editing has been proposed to limit accumulation of endogenous RNAs that might otherwise cause stimulation of the OAS/RNase L pathway. Here, we aim to uncover whether and how such sequence modifications can restrict the ability of short, defined dsRNAs to activate the single-domain form of OAS, OAS1. Unexpectedly, we find that all tested inosine-containing dsRNAs have an increased capacity to activate OAS1, whether in a destabilizing (I•U) or standard Watson-Crick-like base pairing (I-C) context. Additional variants with strongly destabilizing A•C mismatches or stabilizing G-C pairs also exhibit increased capacity to activate OAS1, eliminating helical stability as a factor in the relative ability of the dsRNAs to activate OAS1. Using thermal difference spectra and molecular dynamics simulations, we identify both increased helical dynamics and specific local changes in helical structure as important factors in the capacity of short dsRNAs to activate OAS1. These helical features may facilitate more ready adoption of the distorted OAS1-bound conformation or stabilize important structures to predispose the dsRNA for optimal binding and activation of OAS1. These studies thus reveal the molecular basis for the greater capacity of some short dsRNAs to activate OAS1 in a sequence-independent manner.

Pulmonary alveolar proteinosis due to heterozygous mutation in OAS1: Whole lung lavages for long-term bridging to hematopoietic stem cell transplantation

INTRODUCTION

Pulmonary alveolar proteinosis (PAP) is defined by increased accumulation of surfactant in the alveolar space. PAP has been reported to be associated with a large number of clinical conditions and diseases. Whole lung lavages (WLLs) can be helpful to stabilize the clinical course of PAP until the underlying condition is identified, which may enable more specific treatment. Recently, heterozygous OAS1 gain-of-function variants were described as cause in patients with infantile-onset PAP combined with hypogammaglobulinemia.

CASE PRESENTATION

At age 4 months, a female infant born to term was diagnosed with hypogammaglobulinemia and treated with monthly immunoglobulin injections. At age 15 months, the girl needed supplemental oxygen at night, and at age 18 months, also during the day. At age 2 years, PAP of unknown etiology was diagnosed by computed tomography scan and open lung biopsy. Subsequently, monthly WLLs were started, which stabilized the clinical course for over 2 years until a disease-causing OAS1 variant was diagnosed and the patient was successfully treated by hematopoietic stem cell transplantation (HSCT).

CONCLUSION

Here, we describe the successful management of a female patient with severe PAP caused by a heterozygous OAS1 gain-of-function variant until a definitive diagnosis was made and cured by HSCT.

Early-onset, fatal interstitial lung disease in STAT3 gain-of-function patients

Gain-of-function variants in STAT3 are known to cause severe, multifaceted autoimmunity. Here we report three individuals with de-novo STAT3 GOF alleles and early-onset, severe interstitial lung disease manifesting during the first 3 years of life. Imaging and histology revealed different forms of interstitial pneumonia alongside fibrotic and cystic tissue destruction. Definitive diagnosis was established by postmortem whole exome sequencing and functional validation of two new STAT3 variants. Such lung-predominant forms of STAT3 GOF disease expand the phenotypic spectrum of diseases associated with activating STAT3 variants and add to our understanding of this life-threatening inborn error of immunity.