Type I interferon and systemic lupus erythematosus

EGFR-ErbB2 dual kinase inhibitor lapatinib decreases autoantibody levels and worsens renal disease in Interferon α-accelerated murine lupus

Glomerulonephritis remains a major cause of morbidity and mortality in systemic lupus erythematosus (SLE). We have reported that expression of HER2/ErbB2, a member of the EGFR family, is increased in kidneys of patients and mice with lupus nephritis. We therefore asked if EGFR-family inhibition could ameliorate murine lupus nephritis. We used lapatinib, an EGFR-ErbB2 dual kinase inhibitor in female lupus-prone NZBxW/F1 mice, in which lupus onset was accelerated by injecting an IFN-α-expressing adenovirus. Mice received lapatinib (75 mg/Kg) or vehicle from the beginning of the acceleration or after the mice developed severe proteinuria (>300 mg/dL). Autoantibodies, kidney disease and markers of fibrosis and wound healing were analyzed. Exposure to IFNα induced ErbB2 expression in the kidney of lupus prone mice. Lapatinib, administered before but not after renal disease onset, lowered autoantibody titers and lessened immune complex deposition in the kidney. However, lapatinib increased proteinuria, kidney fibrosis and mouse mortality. Lapatinib also inhibited an in vitro wound healing assay testing renal cells. Our results suggest that EGFR-ErbB2 dual kinase inhibitor lapatinib decreases autoimmunity but worsens renal disease in IFNα-accelerated lupus, by increasing fibrosis and inhibiting wound healing. Type I Interferons are highlighted as important regulators of HER2/ErbB2 expression in the kidney. Further studies are required to parse the beneficial aspects of EGFR inhibition on autoimmunity from its negative effects on wound healing in lupus nephritis.

Basic Investigations in Pediatric Rheumatology

The spectrum of pediatric rheumatological disorders is diverse and they are important differential diagnoses in a variety of clinical scenarios. Basic investigations not only provide supporting evidence for the diagnosis of a rheumatological illness but also help in exclusion of other diseases as well as for monitoring the activity of disease. Among these, complete blood count, biochemical assays including tests for inflammatory response, urine analysis, and various autoantibodies are often used. In addition, depending on the clinical features, imaging and tissue biopsies are used to confirm the diagnosis.

Type I interferon governs immunometabolic checkpoints that coordinate inflammation during Staphylococcal infection

Macrophage metabolic plasticity is central to inflammatory programming, yet mechanisms of coordinating metabolic and inflammatory programs during infection are poorly defined. Here, we show that type I interferon (IFN) temporally guides metabolic control of inflammation during methicillin-resistant Staphylococcus aureus (MRSA) infection. We find that staggered Toll-like receptor and type I IFN signaling in macrophages permit a transient energetic state of combined oxidative phosphorylation (OXPHOS) and aerobic glycolysis followed by inducible nitric oxide synthase (iNOS)-mediated OXPHOS disruption. This disruption promotes type I IFN, suppressing other pro-inflammatory cytokines, notably interleukin-1β. Upon infection, iNOS expression peaks at 24 h, followed by lactate-driven Nos2 repression via histone lactylation. Type I IFN pre-conditioning prolongs infection-induced iNOS expression, amplifying type I IFN. Cutaneous MRSA infection in mice constitutively expressing epidermal type I IFN results in elevated iNOS levels, impaired wound healing, vasculopathy, and lung infection. Thus, kinetically regulated type I IFN signaling coordinates immunometabolic checkpoints that control infection-induced inflammation.

MAVS Cys508 palmitoylation promotes its aggregation on the mitochondrial outer membrane and antiviral innate immunity

Cysteine palmitoylation or S-palmitoylation catalyzed by the ZDHHC family of acyltransferases regulates the biological function of numerous mammalian proteins as well as viral proteins. However, understanding of the role of S-palmitoylation in antiviral immunity against RNA viruses remains very limited. The adaptor protein MAVS forms functionally essential prion-like aggregates upon activation by viral RNA-sensing RIG-I-like receptors. Here, we identify that MAVS, a C-terminal tail-anchored mitochondrial outer membrane protein, is S-palmitoylated by ZDHHC7 at Cys508, a residue adjacent to the tail-anchor transmembrane helix. Using superresolution microscopy and other biochemical techniques, we found that the mitochondrial localization of MAVS at resting state mainly depends on its transmembrane tail-anchor, without regulation by Cys508 S-palmitoylation. However, upon viral infection, MAVS S-palmitoylation stabilizes its aggregation on the mitochondrial outer membrane and thus promotes subsequent propagation of antiviral signaling. We further show that inhibition of MAVS S-palmitoylation increases the host susceptibility to RNA virus infection, highlighting the importance of S-palmitoylation in the antiviral innate immunity. Also, our results indicate ZDHHC7 as a potential therapeutic target for MAVS-related autoimmune diseases.

Lupus IgA1 autoantibodies synergize with IgG to enhance plasmacytoid dendritic cell responses to RNA-containing immune complexes

Autoantibodies to nuclear antigens are hallmarks of systemic lupus erythematosus (SLE) where they contribute to pathogenesis. However, there remains a gap in our knowledge regarding how different isotypes of autoantibodies contribute to this autoimmune disease, including the production of the critical type I interferon (IFN) cytokines by plasmacytoid dendritic cells (pDCs) in response to immune complexes (ICs). We focused on IgA, which is the second-most prevalent isotype in serum and, along with IgG, is deposited in glomeruli in individuals with lupus nephritis. We show that individuals with SLE have serum IgA autoantibodies against most nuclear antigens, correlating with IgG against the same antigen. We investigated whether IgA autoantibodies against a major SLE autoantigen, Smith ribonucleoprotein (Sm/RNP), played a role in IC activation of pDCs. We found that pDCs expressed the IgA-specific Fc receptor, FcαR, and IgA1 autoantibodies synergized with IgG in RNA-containing ICs to generate robust primary blood pDC IFN-α responses in vitro. pDC responses to these ICs required both FcαR and FcγRIIa, showing synergy between these Fc receptors. Sm/RNP IC binding to and internalization by pDCs were greater when ICs contained both IgA1 and IgG. Circulating pDCs from individuals with SLE had higher binding of IgA1-containing ICs and higher expression of FcαR than pDCs from healthy control individuals. Although pDC FcαR expression correlated with the blood IFN-stimulated gene signature in SLE, Toll-like receptor 7 agonists, but not IFN-α, up-regulated pDC FcαR expression in vitro. Together, we show a mechanism by which IgA1 autoantibodies contribute to SLE pathogenesis.

Coordinated immune dysregulation in juvenile dermatomyositis revealed by single-cell genomics

Juvenile dermatomyositis (JDM) is one of several childhood-onset autoimmune disorders characterized by a type I IFN response and autoantibodies. Treatment options are limited due to an incomplete understanding of how the disease emerges from dysregulated cell states across the immune system. We therefore investigated the blood of patients with JDM at different stages of disease activity using single-cell transcriptomics paired with surface protein expression. By immunophenotyping peripheral blood mononuclear cells, we observed skewing of the B cell compartment toward an immature naive state as a hallmark of JDM at diagnosis. Furthermore, we find that these changes in B cells are paralleled by T cell signatures suggestive of Th2-mediated inflammation that persist despite disease quiescence. We applied network analysis to reveal that hyperactivation of the type I IFN response in all immune populations is coordinated with previously masked cell states including dysfunctional protein processing in CD4+ T cells and regulation of cell death programming in NK cells, CD8+ T cells, and γδ T cells. Together, these findings unveil the coordinated immune dysregulation underpinning JDM and provide insight into strategies for restoring balance in immune function.

Lupus IgA1 autoantibodies synergize with IgG to enhance pDC responses to RNA-containing immune complexes

Autoantibodies to nuclear antigens are hallmarks of the autoimmune disease systemic lupus erythematosus (SLE) where they contribute to pathogenesis. However, there remains a gap in our knowledge regarding how different isotypes of autoantibodies contribute to disease, including the production of the critical type I interferon (IFN) cytokines by plasmacytoid dendritic cells (pDCs) in response to immune complexes (ICs). We focused on IgA, which is the second most prevalent isotype in serum, and along with IgG is deposited in glomeruli in lupus nephritis. Here, we show that individuals with SLE have IgA autoantibodies against most nuclear antigens, correlating with IgG against the same antigen. We investigated whether IgA autoantibodies against a major SLE autoantigen, Smith ribonucleoproteins (Sm/RNPs), play a role in IC activation of pDCs. We found that pDCs express the IgA-specific Fc receptor, FcαR, and there was a striking ability of IgA1 autoantibodies to synergize with IgG in RNA-containing ICs to generate robust pDC IFNα responses. pDC responses to these ICs required both FcαR and FcγRIIa, showing a potent synergy between these Fc receptors. Sm/RNP IC binding to and internalization by pDCs were greater when ICs contained both IgA1 and IgG. pDCs from individuals with SLE had higher binding of IgA1-containing ICs and higher expression of FcαR than pDCs from healthy control individuals. Whereas pDC FcαR expression correlated with blood ISG signature in SLE, TLR7 agonists, but not IFNα, upregulated pDC FcαR expression in vitro. Together, we show a new mechanism by which IgA1 autoantibodies contribute to SLE pathogenesis.

Mitf regulates gene expression networks implicated in B cell homeostasis, germinal center responses, and tolerance

Introduction

The microphthalmia transcription factor Mitf has been shown to regulate B cell activation and tolerance. However, the underlying B cell-specific mechanisms responsible, and those that distinguish Mitf from closely related Mitf/TFE (MiT) transcription factors Tfe3, Tfeb, and Tfec, remain obscure.

Methods

Two complementary mouse models of Mitf and MiT deficiency were used: the Mitfmi-vga9/mi-vga9 systemic loss-of-function mutation, and B-cell specific MiT family inactivation via transgenic expression of a trans-dominant negative (TDN) protein (TDN-B). These models were employed to identify MiT family candidate target genes and pathways.

Results

Both models displayed spontaneous splenomegaly coincident with elevated plasma cell numbers, autoantibody titers, and proteinuria. These abnormalities appeared dependent on T helper cells, but independent of other non-B cell intrinsic effects of systemic Mitf inactivation. MiT inactivation in B cells augmented aspects of lupus-like autoimmune disease on the C57BL/6-Faslpr/lpr background. In both models, RNAseq of ex vivo resting B cells showed transcriptional upregulation of genes that control cell cycle, germinal center responses, and plasma cell differentiation. Among the genes strongly upregulated in both models were Socs6, Isp53 (Baiap1), S1pR2, and IgG2b/c. Mitf null B cells, but not TDN-B cells, showed evidence of type I interferon dysregulation.

Discussion

These studies clarify Mitf's role as 1) a key regulator of a B cell intrinsic germinal center program that influences self-tolerance through novel target genes, and 2) a regulator of systemic inflammatory processes that can impact the B cell microenvironment. This distinction of Mitf's function from that of related MiT transcription factors advances our understanding of B cell regulation and autoimmunity.

Complement and MHC patterns can provide the diagnostic framework for inflammatory neuromuscular diseases

Histopathological analysis stands as the gold standard for the identification and differentiation of inflammatory neuromuscular diseases. These disorders continue to constitute a diagnostic challenge due to their clinical heterogeneity, rarity and overlapping features. To establish standardized protocols for the diagnosis of inflammatory neuromuscular diseases, the development of cost-effective and widely applicable tools is crucial, especially in settings constrained by limited resources. The focus of this review is to emphasize the diagnostic value of major histocompatibility complex (MHC) and complement patterns in the immunohistochemical analysis of these diseases. We explore the immunological background of MHC and complement signatures that characterize inflammatory features, with a specific focus on idiopathic inflammatory myopathies. With this approach, we aim to provide a diagnostic algorithm that may improve and simplify the diagnostic workup based on a limited panel of stainings. Our approach acknowledges the current limitations in the field of inflammatory neuromuscular diseases, particularly the scarcity of large-scale, prospective studies that validate the diagnostic potential of these markers. Further efforts are needed to establish a consensus on the diagnostic protocol to effectively distinguish these diseases.

Glucocorticoids, their uses, sexual dimorphisms, and diseases: new concepts, mechanisms, and discoveries

The normal stress response in humans is governed by the hypothalamic-pituitary-adrenal (HPA) axis through heightened mechanisms during stress, raising blood levels of the glucocorticoid hormone cortisol. Glucocorticoids are quintessential compounds that balance the proper functioning of numerous systems in the mammalian body. They are also generated synthetically and are the preeminent therapy for inflammatory diseases. They act by binding to the nuclear receptor transcription factor glucocorticoid receptor (GR), which has two main isoforms (GRα and GRβ). Our classical understanding of glucocorticoid signaling is from the GRα isoform, which binds the hormone, whereas GRβ has no known ligands. With glucocorticoids being involved in many physiological and cellular processes, even small disruptions in their release via the HPA axis, or changes in GR isoform expression, can have dire ramifications on health. Long-term chronic glucocorticoid therapy can lead to a glucocorticoid-resistant state, and we deliberate how this impacts disease treatment. Chronic glucocorticoid treatment can lead to noticeable side effects such as weight gain, adiposity, diabetes, and others that we discuss in detail. There are sexually dimorphic responses to glucocorticoids, and women tend to have a more hyperresponsive HPA axis than men. This review summarizes our understanding of glucocorticoids and critically analyzes the GR isoforms and their beneficial and deleterious mechanisms and the sexual differences that cause a dichotomy in responses. We also discuss the future of glucocorticoid therapy and propose a new concept of dual GR isoform agonist and postulate why activating both isoforms may prevent glucocorticoid resistance.

Single cell spatial transcriptomic profiling of childhood-onset lupus nephritis reveals complex interactions between kidney stroma and infiltrating immune cells

Children with systemic lupus erythematosus (SLE) are at increased risk of developing kidney disease, termed childhood-onset lupus nephritis (cLN). Single cell transcriptomics of dissociated kidney tissue has advanced our understanding of LN pathogenesis, but loss of spatial resolution prevents interrogation of in situ cellular interactions. Using a technical advance in spatial transcriptomics, we generated a spatially resolved, single cell resolution atlas of kidney tissue (>400,000 cells) from eight cLN patients and two controls. Annotated cells were assigned to 35 reference cell types, including major kidney subsets and infiltrating immune cells. Analysis of spatial distribution demonstrated that individual immune lineages localize to specific regions in cLN kidneys, including myeloid cells trafficking to inflamed glomeruli and B cells clustering within tubulointerstitial immune hotspots. Notably, gene expression varied as a function of tissue location, demonstrating how incorporation of spatial data can provide new insights into the immunopathogenesis of SLE. Alterations in immune phenotypes were accompanied by parallel changes in gene expression by resident kidney stromal cells. However, there was little correlation between histologic scoring of cLN disease activity and glomerular cell transcriptional signatures at the level of individual glomeruli. Finally, we identified modules of spatially-correlated gene expression with predicted roles in induction of inflammation and the development of tubulointerstitial fibrosis. In summary, single cell spatial transcriptomics allows unprecedented insights into the molecular heterogeneity of cLN, paving the way towards more targeted and personalized treatment approaches.

Coordinated immune dysregulation in Juvenile Dermatomyositis revealed by single-cell genomics

Juvenile Dermatomyositis (JDM) is one of several childhood-onset autoimmune disorders characterized by a type I interferon response and autoantibodies. Treatment options are limited due to incomplete understanding of how the disease emerges from dysregulated cell states across the immune system. We therefore investigated the blood of JDM patients at different stages of disease activity using single-cell transcriptomics paired with surface protein expression. By immunophenotyping peripheral blood mononuclear cells, we observed skewing of the B cell compartment towards an immature naive state as a hallmark of JDM. Furthermore, we find that these changes in B cells are paralleled by signatures of Th2-mediated inflammation. Additionally, our work identified SIGLEC-1 expression in monocytes as a composite measure of heterogeneous type I interferon activity in disease. We applied network analysis to reveal that hyperactivation of the type I interferon response in all immune populations is coordinated with dysfunctional protein processing and regulation of cell death programming. This analysis separated the ubiquitously expressed type I interferon response into a central hub and revealed previously masked cell states. Together, these findings reveal the coordinated immune dysregulation underpinning JDM and provide novel insight into strategies for restoring balance in immune function.

Type I Interferonopathies: A Clinical Review

This review will discuss when clinicians should consider evaluating for Type I interferonopathies, review clinical phenotypes and molecular defects of Type I interferonopathies, and discuss current treatments.

An interpretable machine learning pipeline based on transcriptomics predicts phenotypes of lupus patients

Machine learning (ML) has the potential to identify subsets of patients with distinct phenotypes from gene expression data. However, phenotype prediction using ML has often relied on identifying important genes without a systems biology context. To address this, we created an interpretable ML approach based on blood transcriptomics to predict phenotype in systemic lupus erythematosus (SLE), a heterogeneous autoimmune disease. We employed a sequential grouped feature importance algorithm to assess the performance of gene sets, including immune and metabolic pathways and cell types, known to be abnormal in SLE in predicting disease activity and organ involvement. Gene sets related to interferon, tumor necrosis factor, the mitoribosome, and T cell activation were the best predictors of phenotype with excellent performance. These results suggest potential relationships between the molecular pathways identified in each model and manifestations of SLE. This ML approach to phenotype prediction can be applied to other diseases and tissues.

Restoration of aberrant gene expression of monocytes in systemic lupus erythematosus via a combined transcriptome-reversal and network-based drug repurposing strategy

BACKGROUND

Monocytes -key regulators of the innate immune response- are actively involved in the pathogenesis of systemic lupus erythematosus (SLE). We sought to identify novel compounds that might serve as monocyte-directed targeted therapies in SLE.

RESULTS

We performed mRNA sequencing in monocytes from 15 patients with active SLE and 10 healthy individuals. Disease activity was assessed with the Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2 K). Leveraging the drug repurposing platforms iLINCS, CLUE and L1000CDS², we identified perturbagens capable of reversing the SLE monocyte signature. We identified transcription factors and microRNAs (miRNAs) that regulate the transcriptome of SLE monocytes, using the TRRUST and miRWalk databases, respectively. A gene regulatory network, integrating implicated transcription factors and miRNAs was constructed, and drugs targeting central components of the network were retrieved from the DGIDb database. Inhibitors of the NF-κB pathway, compounds targeting the heat shock protein 90 (HSP90), as well as a small molecule disrupting the Pim-1/NFATc1/NLRP3 signaling axis were predicted to efficiently counteract the aberrant monocyte gene signature in SLE. An additional analysis was conducted, to enhance the specificity of our drug repurposing approach on monocytes, using the iLINCS, CLUE and L1000CDS² platforms on publicly available datasets from circulating B-lymphocytes, CD4⁺ and CD8⁺ T-cells, derived from SLE patients. Through this approach we identified, small molecule compounds, that could potentially affect more selectively the transcriptome of SLE monocytes, such as, certain NF-κB pathway inhibitors, Pim-1 and SYK kinase inhibitors. Furthermore, according to our network-based drug repurposing approach, an IL-12/23 inhibitor and an EGFR inhibitor may represent potential drug candidates in SLE.

CONCLUSIONS

Application of two independent - a transcriptome-reversal and a network-based -drug repurposing strategies uncovered novel agents that might remedy transcriptional disturbances of monocytes in SLE.

Autophagy pathways in autoimmune diseases

Autophagy comprises a growing range of cellular pathways, which occupy central roles in response to energy deprivation, organelle turnover and proteostasis. Over the years, autophagy has been increasingly linked to governing several aspects of immunity, including host defence against various pathogens, unconventional secretion of cytokines and antigen presentation. While canonical autophagy-mediated antigen processing in thymic epithelial cells supports the generation of a self-tolerant CD4+ T cell repertoire, mounting evidence suggests that deregulated autophagy pathways contribute to or sustain autoimmune responses. In animal models of multiple sclerosis (MS), non-canonical autophagy pathways such as microtubule-associated protein 1 A/1 B-light chain 3 (LC3)-associated phagocytosis can contribute to major histocompatibility complex (MHC) class II presentation of autoantigen, thereby amplifying autoreactive CD4+ T cell responses. In systemic lupus erythematosus (SLE), increased type 1 interferon production is linked to excessive autophagy in plasmacytoid dendritic cells (DCs). In rheumatoid arthritis (RA), autophagy proteins contribute to pathological citrullination of autoantigen. Immunotherapies effective in autoimmune diseases modulate autophagy functions, and strategies harnessing autophagy pathways to restrain autoimmune responses have been developed. This review illustrates recent insights in how autophagy, distinct autophagy pathways and autophagy protein functions intersect with the evolution and progression of autoimmune diseases, focusing on MS, SLE and RA.

Sex bias in lymphocytes: Implications for autoimmune diseases

Autoimmune diseases are characterized by a significant sex dimorphism, with women showing increased susceptibility to disease. This is, at least in part, due to sex-dependent differences in the immune system that are influenced by the complex interplay between sex hormones and sex chromosomes, with contribution from sociological factors, diet and gut microbiota. Sex differences are evident in the number and function of lymphocyte populations. Women mount a stronger pro-inflammatory response than males, with increased lymphocyte proliferation, activation and pro-inflammatory cytokine production, whereas men display expanded regulatory cell subsets. Ageing alters the immune landscape of men and women in differing ways, resulting in changes in autoimmune disease susceptibility. Here we review the current literature on sex differences in lymphocyte function, the factors that influence this, and the implications for autoimmune disease. We propose that improved understanding of sex bias in lymphocyte function can provide sex-specific tailoring of treatment strategies for better management of autoimmune diseases.

Obesity Exacerbates Lupus Activity in Fc Gamma Receptor IIb Deficient Lupus Mice Partly through Saturated Fatty Acid-Induced Gut Barrier Defect and Systemic Inflammation

The prevalence of obesity is increasing, and the coexistence of obesity and systemic lupus erythematosus (lupus) is possible. A high-fat diet (HFD) was orally administered for 6 months in female 8-week-old Fc gamma receptor IIb deficient (FcgRIIb-/-) lupus or age and gender-matched wild-type (WT) mice. Lupus nephritis (anti-dsDNA, proteinuria, and increased creatinine), gut barrier defect (fluorescein isothiocyanate dextran), serum lipopolysaccharide (LPS), serum interleukin (IL)-6, liver injury (alanine transaminase), organ fibrosis (liver and kidney pathology), spleen apoptosis (activated caspase 3), and aorta thickness (but not weight gain and lipid profiles) were more prominent in HFD-administered FcgRIIb-/- mice than the obese WT, without injury in regular diet-administered mice (both FcgRIIb-/- and WT). In parallel, combined palmitic acid (PA; a saturated fatty acid) with LPS (PA + LPS) induced higher tumor necrotic factor-α, IL-6, and IL-10 in the supernatant, inflammatory genes (inducible nitric oxide synthase and IL-1β), reactive oxygen species (dihydroethidium), and glycolysis with reduced mitochondrial activity (extracellular flux analysis) when compared with the activation by each molecule alone in both FcgRIIb-/- and WT macrophages. However, the alterations of these parameters were more prominent in PA + LPS-administered FcgRIIb-/- than in the WT cells. In conclusion, obesity accelerated inflammation in FcgRIIb-/- mice, partly due to the more potent responses from the loss of inhibitory FcgRIIb against PA + LPS with obesity-induced gut barrier defect.

The Cdkn2a gene product p19 alternative reading frame (p19ARF) is a critical regulator of IFNβ-mediated Lyme arthritis

Type I interferon (IFN) has been identified in patients with Lyme disease, and its abundant expression in joint tissues of C3H mice precedes development of Lyme arthritis. Forward genetics using C3H mice with severe Lyme arthritis and C57BL/6 (B6) mice with mild Lyme arthritis identified the Borrelia burgdorferi arthritis-associated locus 1 (Bbaa1) on chromosome 4 (Chr4) as a regulator of B. burgdorferi-induced IFNβ expression and Lyme arthritis severity. B6 mice introgressed with the C3H allele for Bbaa1 (B6.C3-Bbaa1 mice) displayed increased severity of arthritis, which is initiated by myeloid lineage cells in joints. Using advanced congenic lines, the physical size of the Bbaa1 interval has been reduced to 2 Mbp, allowing for identification of potential genetic regulators. Small interfering RNA (siRNA)-mediated silencing identified Cdkn2a as the gene responsible for Bbaa1 allele-regulated induction of IFNβ and IFN-stimulated genes (ISGs) in bone marrow-derived macrophages (BMDMs). The Cdkn2a-encoded p19 alternative reading frame (p19ARF) protein regulates IFNβ induction in BMDMs as shown by siRNA silencing and overexpression of ARF. In vivo studies demonstrated that p19ARF contributes to joint-specific induction of IFNβ and arthritis severity in B. burgdorferi-infected mice. p19ARF regulates B. burgdorferi-induced IFNβ in BMDMs by stabilizing the tumor suppressor p53 and sequestering the transcriptional repressor BCL6. Our findings link p19ARF regulation of p53 and BCL6 to the severity of IFNβ-induced Lyme arthritis in vivo and indicate potential novel roles for p19ARF, p53, and BCL6 in Lyme disease and other IFN hyperproduction syndromes.

Lyme disease is caused by infection with the tick-transmitted bacterium Borrelia burgdorferi. Although different isolates of B. burgdorferi have distinct potential for dissemination and tissue invasion, factors intrinsic to the infected host also play an important role in directing the severity of Lyme disease. In the animal model, infected C3H mice develop severe Lyme arthritis following elevation of type I IFN in joint tissue, while in C57BL/6 (B6) mice arthritis is mild and not associated with type I IFN. We demonstrated that the Borrelia burgdorferi arthritis-associated locus 1 (Bbaa1) on chromosome 4 (Chr4) intrinsically controls the magnitude of IFNβ production and the severity of Lyme arthritis in C3H vs B6 mice. The Cdkn2a gene was positionally identified as the regulator of IFNβ within Bbaa1, and determined to function through its protein product p19 alternative reading frame (p19ARF). ARF regulates IFNβ expression and Lyme arthritis severity by modulating the activities of the tumor suppressor p53 and transcriptional repressor BCL6. Our study provides new insight and potential therapeutic targets for the investigation of type I IFN-dependent Lyme arthritis and other IFN-driven diseases.

Chemical reagents modulate nucleic acid-activated toll-like receptors

Nucleic acid-mediated interferon signaling plays a pivotal role in defense against microorganisms, especially during viral infection. Receptors sensing exogenous nucleic acid molecules are localized in the cytosol and endosomes. Cytosolic sensors, including cGAS, RIG-I, and MDA5, and endosome-anchored receptors are toll-like receptors (TLR3, TLR7, TLR8, and TLR9). These TLRs share the same domain architecture and have similar structures, facing the interior of endosomes so their binding to nucleic acids of invading pathogens via endocytosis is possible. The correct function of these receptors is crucial for cell homeostasis and effective response against pathogen invasion. A variety of endogenous mechanisms modulates their activities. Nevertheless, naturally occurring mutations lead to aberrant TLR-mediated interferon (IFN) signaling. Furthermore, certain pathogens require a more robust defense against control. Thus, manipulating these TLR activities has a profound impact. High-throughput virtual screening followed by experimental validation led to the discovery of numerous chemicals that can change these TLR-mediated IFN signaling activities. Many of them are unique in selectivity, while others regulate more than one TLR due to commonalities in these receptors. We summarized these nucleic acid-sensing TLR-mediated IFN signaling pathways and the corresponding chemicals activating or deactivating their signaling.

OUP accepted manuscript

Background

Heterozygous loss-of-function mutations in the tumour necrosis factor alpha induced protein 3 (TNFAIP3) gene cause an early-onset auto-inflammatory disease named haploinsufficiency of A20 (HA20). Here we describe three unrelated patients with autoimmune lupus nephritis (LN) phenotypes carrying three novel mutations in the TNFAIP3 gene.

Methods

Whole-exome sequencing (WES) was used to identify the causative mutations in three biopsy-proven LN patients. Sanger sequencing and quantitative polymerase chain reaction (qPCR) were used to validate the mutations identified by WES. RNA sequencing, qPCR and cytometric bead array was used to detect inflammatory signatures in the patients.

Results

The patients predominantly presented with an autoimmune phenotype, including autoimmune haemolytic anaemia, multipositive autoantibodies and LN. Additionally, novel phenotypes of allergy and pericardial effusion were first reported. WES identified three novel heterozygous mutations in the TNFAIP3 gene, including a novel splicing mutation located in the canonical splicing site (c.634+2T>C) resulting in an intron 4 insertion containing a premature stop codon, a de novo novel copy number variation (exon 7–8 deletion) and a novel nonsense mutation c.1300_1301delinsTA causing a premature stop codon. We further identified hyperactivation signatures of nuclear factor- kappa B and type I IFN signalling and overproduction of pro-inflammatory cytokines in the blood. This report expanded the phenotype to a later age, as two girls were diagnosed at age 3 years and one man at age 29 years.

Conclusions

Kidney involvement may be the main feature of the clinical spectrum of HA20, even in adults. Genetic screening should be considered for early-onset LN patients.

Deconvoluting virome-wide antibody epitope reactivity profiles

BACKGROUND

Comprehensive characterization of exposures and immune responses to viral infections is critical to a basic understanding of human health and disease. We previously developed the VirScan system, a programmable phage-display technology for profiling antibody binding to a library of peptides designed to span the human virome. Previous VirScan analytical approaches did not carefully account for antibody cross-reactivity among sequences shared by related viruses or for the disproportionate representation of individual viruses in the library.

METHODS

Here we present the AntiViral Antibody Response Deconvolution Algorithm (AVARDA), a multi-module software package for analyzing VirScan datasets. AVARDA provides a probabilistic assessment of infection with species-level resolution by considering sequence alignment of all library peptides to each other and to all human viruses. We employed AVARDA to analyze VirScan data from a cohort of encephalitis patients with either known viral infections or undiagnosed etiologies. We further assessed AVARDA's utility in associating viral infection with type 1 diabetes and lupus.

FINDINGS

By comparing acute and convalescent sera, AVARDA successfully confirmed or detected encephalitis-associated responses to human herpesviruses 1, 3, 4, 5, and 6, improving the rate of diagnosing viral encephalitis in this cohort by 44%. AVARDA analyses of VirScan data from the type 1 diabetes and lupus cohorts implicated enterovirus and herpesvirus infections, respectively.

INTERPRETATION

AVARDA, in combination with VirScan and other pan-pathogen serological techniques, is likely to find broad utility in the epidemiology and diagnosis of infectious diseases.

FUNDING

This work was made possible by support from the National Institutes of Health (NIH), the US Army Research Office, the Singapore Infectious Diseases Initiative (SIDI), the Singapore Ministry of Health's National Medical Research Council (NMRC) and the Singapore National Research Foundation (NRF).

Abnormalities of the type I interferon signaling pathway in lupus autoimmunity

Type I interferons (IFNs), mostly IFNα and IFNβ, and the type I IFN Signature are important in the pathogenesis of Systemic Lupus Erythematosus (SLE), an autoimmune chronic condition linked to inflammation. Both IFNα and IFNβ trigger a signaling cascade that, through the activation of JAK1, TYK2, STAT1 and STAT2, initiates gene transcription of IFN stimulated genes (ISGs). Noteworthy, other STAT family members and IFN Responsive Factors (IRFs) can also contribute to the activation of the IFN response. Aberrant type I IFN signaling, therefore, can exacerbate SLE by deregulated homeostasis leading to unnecessary persistence of the biological effects of type I IFNs. The etiopathogenesis of SLE is partially known and considered multifactorial. Family-based and genome wide association studies (GWAS) have identified genetic and transcriptional abnormalities in key molecules directly involved in the type I IFN signaling pathway, namely TYK2, STAT1 and STAT4, and IRF5. Gain-of-function mutations that heighten IFNα/β production, which in turn maintains type I IFN signaling, are found in other pathologies like the interferonopathies. However, the distinctive characteristics have yet to be determined. Signaling molecules activated in response to type I IFNs are upregulated in immune cell subsets and affected tissues of SLE patients. Moreover, Type I IFNs induce chromatin remodeling leading to a state permissive to transcription, and SLE patients have increased global and gene-specific epigenetic modifications, such as hypomethylation of DNA and histone acetylation. Epigenome wide association studies (EWAS) highlight important differences between SLE patients and healthy controls in Interferon Stimulated Genes (ISGs). The combination of environmental and genetic factors may stimulate type I IFN signaling transiently and produce long-lasting detrimental effects through epigenetic alterations. Substantial evidence for the pathogenic role of type I IFNs in SLE advocates the clinical use of neutralizing anti-type I IFN receptor antibodies as a therapeutic strategy, with clinical studies already showing promising results. Current and future clinical trials will determine whether drugs targeting molecules of the type I IFN signaling pathway, like non-selective JAK inhibitors or specific TYK2 inhibitors, may benefit people living with lupus.

Type I Interferonopathies in Children: An Overview

Notable advances in gene sequencing methods in recent years have permitted enormous progress in the phenotypic and genotypic characterization of autoinflammatory syndromes. Interferonopathies are a recent group of inherited autoinflammatory diseases, characterized by a dysregulation of the interferon pathway, leading to constitutive upregulation of its activation mechanisms or downregulation of negative regulatory systems. They are clinically heterogeneous, but some peculiar clinical features may lead to suspicion: a familial "idiopathic" juvenile arthritis resistant to conventional treatments, an early necrotizing vasculitis, a non-infectious interstitial lung disease, and a panniculitis associated or not with a lipodystrophy may represent the "interferon alarm bells." The awareness of this group of diseases represents a challenge for pediatricians because, despite being rare, a differential diagnosis with the most common childhood rheumatological and immunological disorders is mandatory. Furthermore, the characterization of interferonopathy molecular pathogenetic mechanisms is allowing important steps forward in other immune dysregulation diseases, such as systemic lupus erythematosus and inflammatory myositis, implementing the opportunity of a more effective target therapy.

First-in-Human study of JNJ-55920839 in healthy volunteers and patients with systemic lupus erythematosus: a randomised placebo-controlled phase 1 trial

BACKGROUND

Activation of the type I interferon (IFN) pathway is associated with systemic lupus erythematosus (SLE). We assessed the safety and tolerability of JNJ-55920839, a human monoclonal antibody that selectively neutralises most human IFNα subtypes and IFNω, in healthy participants and those with SLE.

METHODS

This was a two-part, first-in-human, phase 1, randomised, double-blind, placebo-controlled, multicentre study of single-ascending intravenous doses of 0·3-15 mg/kg or a single subcutaneous dose of 1 mg/kg JNJ-55920839 administered to healthy participants (part A) and multiple intravenous doses of 10 mg/kg JNJ-55920839 administered to participants with SLE (part B). Healthy men and women (women had to be postmenopausal or surgically sterile) aged 18-55 years; bodyweight of 50-90 kg; and body-mass index (BMI) of 18-30 kg/m2 were eligible for inclusion in part A. Men and women with SLE were recruited to part B, fertile female participants were required to have a negative pregnancy test result before and during the study and be using two highly effective methods of birth control. The inclusion criteria for participants with SLE in part B matched part A, except for bodyweight (40-100 kg). In both parts, participants were randomly assigned (3:1) to receive JNJ-55920839 or placebo; a computer-generated randomisation schedule was used in part A, and randomisation was stratified by racial and ethnic subpopulation and elevated levels of serological disease activity in part B. The primary outcome was evaluation of safety and tolerability of the study regimen assessed using clinical and laboratory tests compared with placebo. This study is registered with ClinicalTrials.gov, NCT02609789.

FINDINGS

Between Dec 11, 2015, and Sept 20, 2018, 48 healthy participants from a single site and 28 participants with mild-to-moderate SLE from 19 participating centres in seven countries were enrolled in the study. 12 healthy volunteers in part A and eight participants with SLE in part B received placebo. The most common treatment-emergent adverse events in both part A and B were in the system organ class of infections and infestations with a higher percentage of participants administered JNJ-55920839 with infections (ten [28%] of 36 in part A and nine [50%] of 18 in part B) than those exposed to placebo (two [17%] of 12 in part A and one [13%] of eight in part B). Particpants in part B were permitted to continue on defined ongoing standard of care medications. In two participants with SLE, locally disseminated herpes zoster of the skin was reported. No other clinically significant safety or tolerability issues were identified beyond the infections observed in participants treated with JNJ-55920839.

INTERPRETATION

JNJ-55920839 was well tolerated and safe. Additional studies are warranted to determine optimal dosing of patients and further explore safety.

FUNDING

Janssen.

Rare genetic variants in systemic autoimmunity

Autoimmune disease is a substantial cause of morbidity and is strongly influenced by genetic risk. Extensive efforts have characterized the overall genetic basis of many autoimmune diseases, typically by investigation of common variants. While these common variants have modest effects and may cumulatively predispose to disease, it is also increasingly apparent that rare variants have significantly greater effect on phenotype and are likely to contribute to autoimmune disease. Recent advances have illustrated the next fundamental step in elucidating the genetic basis of autoimmunity, moving beyond association to demonstrate the functional consequences of these variants.

The early local and systemic Type I interferon responses to ultraviolet B light exposure are cGAS dependent

Most systemic lupus erythematosus (SLE) patients are photosensitive and ultraviolet B light (UVB) exposure worsens cutaneous disease and precipitates systemic flares of disease. The pathogenic link between skin disease and systemic exacerbations in SLE remains elusive. In an acute model of UVB-triggered inflammation, we observed that a single UV exposure triggered a striking IFN-I signature not only in the skin, but also in the blood and kidneys. The early IFN-I signature was significantly higher in female compared to male mice. The early IFN-I response in the skin was almost entirely, and in the blood partly, dependent on the presence of cGAS, as was skin inflammatory cell infiltration. Inhibition of cGAMP hydrolysis augmented the UVB-triggered IFN-I response. UVB skin exposure leads to cGAS-activation and both local and systemic IFN-I signature and could contribute to acute flares of disease in susceptible subjects such as patients with SLE.

T Cells Produce IFN-α in the TREX1 D18N Model of Lupus-like Autoimmunity

Autoimmunity can result when cells fail to properly dispose of DNA. Mutations in the three-prime repair exonuclease 1 (TREX1) cause a spectrum of human autoimmune diseases resembling systemic lupus erythematosus. The cytosolic dsDNA sensor, cyclic GMP-AMP synthase (cGAS), and the stimulator of IFN genes (STING) are required for pathogenesis, but specific cells in which DNA sensing and subsequent type I IFN (IFN-I) production occur remain elusive. In this study, we demonstrate that TREX1 D18N catalytic deficiency causes dysregulated IFN-I signaling and autoimmunity in mice. Moreover, we show that bone marrow-derived cells drive this process. We identify both innate immune and, surprisingly, activated T cells as sources of pathological IFN-α production. These findings demonstrate that TREX1 enzymatic activity is crucial to prevent inappropriate DNA sensing and IFN-I production in immune cells, including normally low-level IFN-α-producing cells. These results expand our understanding of DNA sensing and innate immunity in T cells and may have relevance to the pathogenesis of human disease caused by TREX1 mutation.

Clinical significance of reduced expression of lncRNA TUG1 in the peripheral blood of systemic lupus erythematosus patients

OBJECTIVE

To investigate the expression and clinical significance of long non-coding RNA taurine up-regulated gene 1 (lncRNA TUG1) in the peripheral blood of systemic lupus erythematosus (SLE) patients.

METHODS

With the peripheral blood mononuclear cells (PBMCs: T-cells, B-cells and monocytes) collected from SLE patients and healthy controls, TUG1 expression was determined to identify the correlation with the clinicopathological features of SLE patients. Thereby, the diagnostic value of TUG1 expression in diagnosis of SLE was evaluated by receiver operating characteristic (ROC) curve analysis.

RESULTS

As compared to healthy controls, SLE patients manifested a lower expression of TUG1 in PBMCs, which was further decreased in SLE patients with lupus nephritis (P < .05). The lowest level of TUG1 was found in monocytes, rather than T-cells or B-cells (P < .05). Negative correlations were identified between TUG1 levels and SLE Disease Activity Index score (r = -.904, P < .001), erythrocyte sedimentation rate (r = -.779, P < .001), disease duration (r = -.503, P < .001) and 24-hour urinary protein (r = -.807, P < .001). Complement C3 levels were positively associated with TUG1 expression (r = .817, P < .001). In addition, the area under the ROC curve of diagnostic efficiency for SLE based on TUG1 was 0.982, and 0.930 for SLE with lupus nephritis.

CONCLUSIONS

The levels of lncRNA TUG1 was markedly lower in the SLE patients, which was more obvious in SLE patients with lupus nephritis, and thus, it could be a promising clinical diagnostic tool for SLE patients or SLE patients with lupus nephritis.

Dysregulated Fcγ receptor IIa-induced cytokine production in dendritic cells of lupus nephritis patients

Systemic lupus erythematosus (SLE) is an autoimmune disease of unknown etiology. One of the key factors associated with SLE pathogenesis is excessive production of type I interferons (IFNs). This could result from increased activation of type I IFN-stimulating pathways, but also from decreased activation of type I IFN-inhibitory pathways. Recently, we have identified that immunoglobulin (Ig)G immune complexes strongly inhibit type I IFN production in healthy individuals by inhibitory signaling through Fcγ receptor IIa (FcγRIIa) on dendritic cells (DCs). Because, in SLE patients, immune complexes are characteristically present, we assessed whether FcγR-induced suppression of type I IFN is functional in DCs of SLE patients. We divided the SLE patients into one group without, and one group with, previous major organ involvement, for which we chose nephritis as a prototypical example. We show that DCs of lupus nephritis patients displayed impaired FcγR-mediated type I IFN inhibition compared to SLE patients without major organ involvement or healthy controls. We verified that this impaired type I IFN inhibition was not related to differences in disease activity, medication, FcγRIIa expression or expression of IFN regulatory transcription factors (IRF)1 and IRF5. In addition, we identified that DCs of lupus nephritis patients show increased FcγR-induced interleukin (IL)-1β production, which is another important cytokine that promotes kidney inflammation. Taken together, these data indicate that DCs of lupus nephritis patients display altered FcγR-mediated regulation of cytokine production, resulting in elevated levels of type I IFN and IL-1β. This dysregulation may contribute to the development of nephritis in SLE patients.

Inflammatory markers in systemic lupus erythematosus

While systemic lupus erythematosus (SLE) is an autoantibody and immune complex disease by nature, most of its organ manifestations are in fact inflammatory. SLE activity scores thus heavily rely on assessing inflammation in the various organs. This focus on clinical items demonstrates that routine laboratory markers of inflammation are still limited in their impact. The erythrocyte sedimentation rate (ESR) is used, but represents a rather crude overall measure. Anemia and diminished serum albumin play a role in estimating inflammatory activity, but both are reflecting more than one mechanism, and the association with inflammation is complex. C-reactive protein (CRP) is a better marker for infections than for SLE activity, where there is only a limited association, and procalcitonin (PCT) is also mainly used for detecting severe bacterial infection. Of the cytokines directly induced by immune complexes, type I interferons, interleukin-18 (IL-18) and tumor necrosis factor (TNF) are correlated with inflammatory disease activity. Still, precise and timely measurement is an issue, which is why they are not currently used for routine purposes. While somewhat more robust in the assays, IL-18 binding protein (IL-18BP) and soluble TNF-receptor 2 (TNF-R2), which are related to the respective cytokines, have not yet made it into clinical routine. The same is true for several chemokines that are increased with activity and relatively easy to measure, but still experimental parameters. In the urine, proteinuria leads and is essential for assessing kidney involvement, but may also result from damage. Similar to the situation in serum and plasma, several cytokines and chemokines perform reasonably well in scientific studies, but are not routine parameters. Cellular elements in the urine are more difficult to assess in the routine laboratory, where sufficient routine is not always available. Therefore, the analysis of urinary T cells may have potential for better monitoring renal inflammation.

Type I interferon gene signature test–low and –high patients with systemic lupus erythematosus have distinct gene expression signatures

Objectives

Type I interferon (IFN) is implicated in systemic lupus erythematosus (SLE) pathogenesis. We aimed to identify type I IFN signaling-dependent and -independent molecular pathways in a large population of patients with SLE.

Methods

Baseline blood samples from adult patients with moderate to severe SLE from two Phase IIb studies (NCT01438489, n = 265; NCT01283139, n = 416) were profiled using whole transcriptome array analyses. Type I IFN gene signature (IFNGS) test status (high or low) was determined using a validated qualitative polymerase chain reaction–based test. IFN-type-specific signatures were developed by stimulating healthy blood with IFN-β, IFN-γ, IFN-λ, IFN-ω, or pooled IFN-α. These, and multiple literature-derived cell type and cytokine pathway signatures, were evaluated in individual and pooled study populations. A Fisher’s exact test was used for associations, adjusted for false discovery rate.

Results

Whole blood samples from IFNGS test–high patients were enriched versus IFNGS test–low patients for CD40L signaling ( Q < 0.001), CXC cytokine ( Q < 0.001), TLR8-mediated monocyte activation ( Q < 0.001), IgG ( Q < 0.001), major histocompatibility complex class I ( Q < 0.001), and plasma cell ( Q < 0.001) gene expression signatures. IFNGS test–low patients had significant enrichment of eosinophil ( Q < 0.001), IFN-γ-specific ( Q = 0.005), and T-cell or B-cell ( Q < 0.001) signatures. Similar enrichment profiles were demonstrated in patients with primary Sjögren’s syndrome, systemic sclerosis, and dermatomyositis.

Conclusions

IFNGS test–high patients overexpressed many gene signatures associated with SLE pathogenesis compared with IFNGS test–low patients, reflecting broad immune activation. These results provide new insights into the molecular heterogeneity underlying SLE pathogenesis, highlighting shared mechanisms beyond type I IFN, across several autoimmune diseases.

Trial registration

Clinicaltrials.gov: NCT01438489 and NCT01283139.

Biologics in the Treatment of Lupus Erythematosus: A Critical Literature Review

Systemic lupus erythematosus (SLE) is a chronic autoimmune inflammatory disease affecting multiple organ systems that runs an unpredictable course and may present with a wide variety of clinical manifestations. Advances in treatment over the last decades, such as use of corticosteroids and conventional immunosuppressive drugs, have improved life expectancy of SLE sufferers. Unfortunately, in many cases effective management of SLE is still related to severe drug-induced toxicity and contributes to organ function deterioration and infective complications, particularly among patients with refractory disease and/or lupus nephritis. Consequently, there is an unmet need for drugs with a better efficacy and safety profile. A range of different biologic agents have been proposed and subjected to clinical trials, particularly dedicated to this subset of patients whose disease is inadequately controlled by conventional treatment regimes. Unfortunately, most of these trials have given unsatisfactory results, with belimumab being the only targeted therapy approved for the treatment of SLE so far. Despite these pitfalls, several novel biologic agents targeting B cells, T cells, or cytokines are constantly being evaluated in clinical trials. It seems that they may enhance the therapeutic efficacy when combined with standard therapies. These efforts raise the hope that novel drugs for patients with refractory SLE may be available in the near future. This article reviews the current biological therapies being tested in the treatment of SLE.

The cytokine network type I IFN-IL-27-IL-10 is augmented in murine and human lupus

IL-10 is elevated in the autoimmune disease systemic lupus erythematosus (SLE). Here, we show that conventional dendritic cells (cDCs) from predisease lupus-prone B6.NZM Sle1/Sle2/Sle3 triple congenic (TCSle) mice produce more IL-10 than wild-type congenic cDCs upon TLR stimulation, and this overproduction is prevented by blocking the type I IFN receptor (IFNAR) with specific Abs. Priming wild-type cDCs with type I IFN mimics the IL-10 overproduction of TCSle cDCs. The MAPK ERK is more phosphorylated in lupus cDCs, partially contributing to IL-10 overproduction. Moreover, we found that TCSle cDCs express higher levels of IL-27 upon TLR7/TLR9 stimulation, and IFNAR blockade reduced IL-27 levels in TCSle cDCs. These results suggest that dysregulated type I IFNs in cDCs contribute to the increased IL-10 and IL-27 in SLE. Since IL-27 neutralization did not inhibit TLR-induced IL-10 production, we propose that type I IFNs enhanced IL-10 in TCSle cDCs independently from IL-27. Moreover, RNA sequencing analysis of a cohort of SLE patients reveals higher gene expression of these cytokines in SLE patients expressing a high IFN signature. Since IL-27 and IL-10 have both pro- and anti-inflammatory effects, our results also suggest that these cytokines can be modulated by the therapeutic IFN blockade in trials in SLE patients and have complex effects on the autoimmune response.

Tubular cell and keratinocyte single-cell transcriptomics applied to lupus nephritis reveal type I IFN and fibrosis relevant pathways

The molecular and cellular processes that lead to renal damage and to the heterogeneity of lupus nephritis (LN) are not well understood. We applied single-cell RNA sequencing (scRNA-seq) to renal biopsies from patients with LN and evaluated skin biopsies as a potential source of diagnostic and prognostic markers of renal disease. Type I interferon (IFN) response signatures in tubular cells and in keratinocytes distinguished patients with LN from healthy control subjects. Moreover, a high IFN response signature and fibrotic signature in tubular cells were each associated with failure to respond to treatment. Analysis of tubular cells from patients with proliferative, membranous, and mixed LN indicated pathways relevant to inflammation and fibrosis, which offer insight into their histological differences. In summary, we applied scRNA-seq to LN to deconstruct its heterogeneity and identify novel targets for personalized approaches to therapy.

Unmet need in rheumatology: reports from the Targeted Therapies meeting 2018

To develop a comprehensive listing of the greatest unmet scientific and clinical needs in rheumatology. The 20th annual international Targeted Therapies meeting brought more than 100 leading basic scientists and clinical researchers in rheumatology, immunology, epidemiology, molecular biology and other specialties. During the meeting, breakout sessions were convened, consisting of five disease-specific groups with 20-30 experts assigned to each group based on expertise. Specific groups included rheumatoid arthritis, psoriatic arthritis, axial spondyloarthritis, systemic lupus erythematosus, connective tissue diseases and a basic science immunology group spanning all of these clinical domains. In each group, experts were asked to consider recent accomplishments within their clinical domain in the last year and update the unmet needs in three categorical areas: basic/translational science, clinical science and therapeutic development, and clinical care. While progress was noted among some of previously identified needs, both new needs were identified and themes from prior meetings were re-iterated: the need for better understanding the heterogeneity within each disease, and for identifying preclinical states of disease allowing treatment and prevention of disease in those at risk, and the elusive ability to cure disease. Within the clinical care realm, improved comorbidity management and patient-centred care continue to be unmet needs, and the need for new and affordable therapeutics was highlighted. Unmet needs for new and accessible targeted therapies, disease prevention and ultimately cure remain a priority in rheumatology.

Curli-Containing Enteric Biofilms Inside and Out: Matrix Composition, Immune Recognition, and Disease Implications

Biofilms of enteric bacteria are highly complex, with multiple components that interact to fortify the biofilm matrix. Within biofilms of enteric bacteria such as Escherichia coli and Salmonella species, the main component of the biofilm is amyloid curli. Other constituents include cellulose, extracellular DNA, O antigen, and various surface proteins, including BapA. Only recently, the roles of these components in the formation of the enteric biofilm individually and in consortium have been evaluated. In addition to enhancing the stability and strength of the matrix, the components of the enteric biofilm influence bacterial virulence and transmission. Most notably, certain components of the matrix are recognized as pathogen-associated molecular patterns. Systemic recognition of enteric biofilms leads to the activation of several proinflammatory innate immune receptors, including the Toll-like receptor 2 (TLR2)/TLR1/CD14 heterocomplex, TLR9, and NLRP3. In the model of Salmonella enterica serovar Typhimurium, the immune response to curli is site specific. Although a proinflammatory response is generated upon systemic presentation of curli, oral administration of curli ameliorates the damaged intestinal epithelial barrier and reduces the severity of colitis. Furthermore, curli (and extracellular DNA) of enteric biofilms potentiate the autoimmune disease systemic lupus erythematosus (SLE) and promote the fibrillization of the pathogenic amyloid α-synuclein, which is implicated in Parkinson's disease. Homologues of curli-encoding genes are found in four additional bacterial phyla, suggesting that the biomedical implications involved with enteric biofilms are applicable to numerous bacterial species.

Conventional DCs from Male and Female Lupus-Prone B6.NZM Sle1/Sle2/Sle3 Mice Express an IFN Signature and Have a Higher Immunometabolism That Are Enhanced by Estrogen

Type I interferons (IFN) are pathogenic in systemic lupus erythematosus (SLE) and were proposed to control the immunometabolism of dendritic cells (DCs). We previously reported that DCs from female lupus-prone mice constitutively overexpress IFN-responsive genes resembling the IFN signature found in SLE patients. As SLE has higher incidence in women than men, more so in women of reproductive age, estrogens are suggested to affect lupus pathogenesis. We investigated the effects of sex and estrogens on the IFN signature in conventional GM-CSF-bone marrow-derived DCs (cDCs), from male and female Triple Congenic B6.NZM.Sle1/Sle2/Sle3 (TCSle) lupus-prone mice or from wild-type C57BL/6 mice, generated with titrations of 17-beta-estradiol (E2). We found that cDCs from prediseased TCSle male mice express the IFN signature as female TCSle cDCs do. Estrogens are necessary but not sufficient to express this IFN signature, but high doses of E2 can compensate for other steroidal components. E2 stimulation, regardless of sex, modulates type I IFN-dependent and type I IFN-independent activation of cDCs in response to TLR stimulation. Finally, we found that TCSle cDCs from both sexes have elevated markers of immunometabolism and estrogens enhance the metabolic pathways in cDCs, suggesting a mechanistic link between estrogens, immunometabolism, and the IFN signature in lupus.

Longitudinal association of type 1 interferon-induced chemokines with disease activity in systemic lupus erythematosus

Type I interferon (IFN) pathways are significant in SLE pathogenesis. Less is known about the utility of measuring markers of IFN activity in patients, or whether patient subsets with different profiles exist. We explored the longitudinal associations of IFN-induced chemokines with disease activity in a cohort of SLE patients. We calculated a validated composite score (IFN-CK) of three type I IFN-inducible chemokines (CCL2/CXCL10/CCL19) measured in 109 SLE patients (median 7 occasions over 3.2 years). Longitudinal associations of IFN-CK score with disease activity (SLEDAI-2K) and other variables were assessed using general estimating equation (GEE) methods. IFN-CK was detectable in all patients. SLEDAI-2K was significantly associated with IFN-CK, damage score and prednisolone dose. SLEDAI-2K remained significantly associated with IFN-CK over time after adjustment of covariates. Patients with high time-adjusted mean IFN-CK had lower complement and higher time-adjusted disease activity. Concordance between IFN-CK and SLEDAI-2K varied widely among patients, with some individuals having none, others weak, and a subset very high concordance. In summary in our cohort of SLE patients, serum IFN-CK varied over time with disease activity, but with wide variation in concordance. Differing relationships between IFN pathway activation and disease activity may be valuable in assigning patients to emerging IFN-pathway targeting treatments.

Autoimmunity and primary immunodeficiency: two sides of the same coin?

Autoimmunity and immunodeficiency were previously considered to be mutually exclusive conditions; however, increased understanding of the complex immune regulatory and signalling mechanisms involved, coupled with the application of genetic analysis, is revealing the complex relationships between primary immunodeficiency syndromes and autoimmune diseases. Single-gene defects can cause rare diseases that predominantly present with autoimmune symptoms. Such genetic defects also predispose individuals to recurrent infections (a hallmark of immunodeficiency) and can cause primary immunodeficiencies, which can also lead to immune dysregulation and autoimmunity. Moreover, risk factors for polygenic rheumatic diseases often exist in the same genes as the mutations that give rise to primary immunodeficiency syndromes. In this Review, various primary immunodeficiency syndromes are presented, along with their pathogenetic mechanisms and relationship to autoimmune diseases, in an effort to increase awareness of immunodeficiencies that occur concurrently with autoimmune diseases and to highlight the need to initiate appropriate genetic tests. The growing knowledge of various genetically determined pathologic mechanisms in patients with immunodeficiencies who have autoimmune symptoms opens up new avenues for personalized molecular therapies that could potentially treat immunodeficiency and autoimmunity at the same time, and that could be further explored in the context of autoimmune rheumatic diseases.

Single cell RNA sequencing to dissect the molecular heterogeneity in lupus nephritis

Lupus nephritis is a leading cause of mortality among systemic lupus erythematosus (SLE) patients, and its heterogeneous nature poses a significant challenge to the development of effective diagnostics and treatments. Single cell RNA sequencing (scRNA-seq) offers a potential solution to dissect the heterogeneity of the disease and enables the study of similar cell types distant from the site of renal injury to identify novel biomarkers. We applied scRNA-seq to human renal and skin biopsy tissues and demonstrated that scRNA-seq can be performed on samples obtained during routine care. Chronicity index, IgG deposition, and quantity of proteinuria correlated with a transcriptomic-based score composed of IFN-inducible genes in renal tubular cells. Furthermore, analysis of cumulative expression profiles of single cell keratinocytes dissociated from nonlesional, non-sun-exposed skin of patients with lupus nephritis also revealed upregulation of IFN-inducible genes compared with keratinocytes isolated from healthy controls. This indicates the possible use of scRNA-seq analysis of skin biopsies as a biomarker of renal disease. These data support the potential utility of scRNA-seq to provide new insights into the pathogenesis of lupus nephritis and pave the way for exploiting a readily accessible tissue to reflect injury in the kidney.

TSG-6 Downregulates IFN-Alpha and TNF-Alpha Expression by Suppressing IRF7 Phosphorylation in Human Plasmacytoid Dendritic Cells

Proinflammatory cytokines such as TNF-α and type I interferons (IFN) are pathogenic signatures of systemic lupus erythematosus, and plasmacytoid dendritic cells (pDCs) play a major role by predominantly producing IFN-α. Given the rise of importance in identifying tumor necrosis stimulated gene 6 (TSG-6) as a key anti-inflammatory regulator, we investigate its function and its ability to counteract proinflammatory cytokine secretion by pDCs in vitro. CpG-A and R837 induced significant endogenous TSG-6 expression in the pDC cell-line GEN2.2. Following recombinant human TSG-6 treatment and CpG-A or R837 stimulation, significant reduction in IFN-α and TNF-α was observed in healthy donors' pDCs, and the same phenomenon was confirmed in GEN2.2. By CD44 blocking assay, we deduced that the suppressive effect of TSG-6 is mediated by CD44, by reducing IRF-7 phosphorylation. Our findings suggest that TSG-6 and its downstream signalling pathway could potentially be targeted to modulate proinflammatory cytokine expression in pDCs.

Long-term Effects of Intravenous Cyclophosphamide in Combination with Mesna Provided Intravenously and via Bladder Perfusion in a Patient with Severe Multifocal Motor Neuropathy

A 25-year-old woman presenting with progressive muscle weakness in the distal extremities in the absence of sensory involvement for 2 years was diagnosed with multifocal motor neuropathy (MMN). Her disease was difficult to manage with various immunosuppressants, and the muscle weakness eventually progressed to involve the respiratory muscles, necessitating mechanical ventilation. Intravenous cyclophosphamide (CY) dramatically improved her symptoms, and she has since maintained her ambulatory status for 18 years with intermittent CY therapy. Because the patient presented with hemorrhagic cystitis due to CY, we also implemented mesna administration by bladder perfusion. The administration of CY should therefore be considered in patients with severe MMN that is unresponsive to standard therapy.

Targeting the interferon pathway with sifalimumab for the treatment of systemic lupus erythematosus

Dysregulation of the type I interferon (IFN) system is associated with various immunologic diseases, such as systemic lupus erythematosus (SLE). Targeting this dysregulation presents an attractive approach for SLE therapy. Sifalimumab, a fully human immunoglobulin G1 κ monoclonal antibody that binds to and neutralizes most IFN-α subtypes, has been recently evaluated in a Phase IIb study in patients with moderate to severe SLE. Insights gained from earlier studies were used to inform design of the Phase IIb study, to provide a more comprehensive evaluation of sifalimumab. Sifalimumab demonstrated broad efficacy across composite and organ-specific end points, suggesting that targeting of IFN-α is a promising treatment option for SLE, particularly for those patients whose disease is refractory to current standard of care.