Effect of in vivo Hydroxychloroquine and ex vivo Anti-BDCA2 mAb Treatment on pDC IFNα Production From Patients Affected With Cutaneous Lupus Erythematosus

Plasmacytoid Dendritic Cells Are Not Major Producers of Type 1 IFN in Cutaneous Lupus: An In-Depth Immunoprofile of Subacute and Discoid Lupus

The immunologic drivers of cutaneous lupus erythematosus (CLE) and its clinical subtypes remain poorly understood. We sought to characterize the immune landscape of discoid lupus erythematosus and subacute CLE using multiplexed immunophenotyping. We found no significant differences in immune cell percentages between discoid lupus erythematosus and subacute CLE (P > .05) with the exception of an increase in TBK1 in discoid lupus erythematosus (P < .05). Unbiased clustering grouped subjects into 2 major clusters without respect to clinical subtype. Subjects with a history of smoking had increased percentages of neutrophils, disease activity, and endothelial granzyme B compared with nonsmokers. Despite previous assumptions, plasmacytoid dendritic cells (pDCs) did not stain for IFN-1. Skin-eluted and circulating pDCs from subjects with CLE expressed significantly less IFNα than healthy control pDCs upon toll-like receptor 7 stimulation ex vivo (P < .0001). These data suggest that discoid lupus erythematosus and subacute CLE have similar immune microenvironments in a multiplexed investigation. Our aggregated analysis of CLE revealed that smoking may modulate disease activity in CLE through neutrophils and endothelial granzyme B. Notably, our data suggest that pDCs are not the major producers of IFN-1 in CLE. Future in vitro studies to investigate the role of pDCs in CLE are needed.

Platelet TLR7 is essential for the formation of platelet-neutrophil complexes and low-density neutrophils in lupus nephritis

OBJECTIVES

Platelets and low-density neutrophils (LDNs) are major players in the immunopathogenesis of SLE. Despite evidence showing the importance of platelet-neutrophil complexes (PNCs) in inflammation, little is known about the relationship between LDNs and platelets in SLE. We sought to characterize the role of LDNs and Toll-like receptor 7 (TLR7) in clinical disease.

METHODS

Flow cytometry was used to immunophenotype LDNs from SLE patients and controls. The association of LDNs with organ damage was investigated in a cohort of 290 SLE patients. TLR7 mRNA expression was assessed in LDNs and high-density neutrophils (HDNs) using publicly available mRNA sequencing datasets and our own cohort using RT-PCR. The role of TLR7 in platelet binding was evaluated in platelet-HDN mixing studies using TLR7-deficient mice and Klinefelter syndrome patients.

RESULTS

SLE patients with active disease have more LDNs, which are heterogeneous and more immature in patients with evidence of kidney dysfunction. LDNs are platelet bound, in contrast to HDNs. LDNs settle in the peripheral blood mononuclear cell (PBMC) layer due to the increased buoyancy and neutrophil degranulation from platelet binding. Mixing studies demonstrated that this PNC formation was dependent on platelet-TLR7 and that the association results in increased NETosis. The neutrophil:platelet ratio is a useful clinical correlate for LDNs, and a higher NPR is associated with past and current flares of LN.

CONCLUSIONS

LDNs sediment in the upper PBMC fraction due to PNC formation, which is dependent on the expression of TLR7 in platelets. Collectively, our results reveal a novel TLR7-dependent crosstalk between platelets and neutrophils that may be an important therapeutic opportunity for LN.

Emerging immunotherapeutic strategies for cutaneous lupus erythematosus: an overview of recent phase 2 and 3 clinical trials

INTRODUCTION

Cutaneous lupus erythematosus (CLE) is an autoimmune disease that is clinically heterogenous and may occur with or without the presence of systemic lupus erythematosus (SLE). While existing on a spectrum, CLE and SLE present differences in their underlying pathogenesis and therapeutic responses. No new therapies have been approved in recent decades by the U.S. Food and Drug Administration for CLE, although frequently refractory to conventional therapies. There is an unmet need to develop effective drugs for CLE as it significantly impacts patients' quality of life and may leave irreversible disfiguring damage.

AREAS COVERED

This review provides an update on the latest phase 2 and 3 clinical trials performed in CLE or SLE using skin-specific outcome measures. Emergent therapies are presented alongside their mechanism of action as recent translational studies have permitted identification of critical targets among immune cells and/or pathways involved in CLE.

EXPERT OPINION

While the recent literature has few trials for CLE, drugs targeting type I interferon, its downstream signaling and plasmacytoid dendritic cells have shown promising results. Further research is required to develop long-awaited effective therapies, and this review highlights the importance of implementing trials dedicated to CLE to fill the current gap in CLE therapeutics.

Mitochondrial DNA Sensing Pathogen Recognition Receptors in Systemic Sclerosis Associated Interstitial Lung Disease: A Review

Purpose of the review

Systemic sclerosis (SSc) is a condition of dermal and visceral scar formation characterized by immune dysregulation and inflammatory fibrosis. Approximately 90% of SSc patients develop interstitial lung disease (ILD), and it is the leading cause of morbidity and mortality. Further understanding of immune-mediated fibroproliferative mechanisms has the potential to catalyze novel treatment approaches in this difficult to treat disease.

Recent findings

Recent advances have demonstrated the critical role of aberrant innate immune activation mediated by mitochondrial DNA (mtDNA) through interactions with toll-like receptor 9 (TLR9) and cytosolic cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS).

Summary

In this review, we will discuss how the nature of the mtDNA, whether oxidized or mutated, and its mechanism of release, either intracellularly or extracellularly, can amplify fibrogenesis by activating TLR9 and cGAS, and the novel insights gained by interrogating these signaling pathways. Because the scope of this review is intended to generate hypotheses for future research, we conclude our discussion with several important unanswered questions.

Immunosuppression by hydroxychloroquine: mechanistic proof in in vitro experiments but limited systemic activity in a randomized placebo-controlled clinical pharmacology study

Based on its wide range of immunosuppressive properties, hydroxychloroquine (HCQ) is used for the treatment of several autoimmune diseases. Limited literature is available on the relationship between HCQ concentration and its immunosuppressive effect. To gain insight in this relationship, we performed in vitro experiments in human PBMCs and explored the effect of HCQ on T and B cell proliferation and Toll-like receptor (TLR)3/TLR7/TLR9/RIG-I-induced cytokine production. In a placebo-controlled clinical study, these same endpoints were evaluated in healthy volunteers that were treated with a cumulative dose of 2400 mg HCQ over 5 days. In vitro, HCQ inhibited TLR responses with IC50s > 100 ng/mL and reaching 100% inhibition. In the clinical study, maximal HCQ plasma concentrations ranged from 75 to 200 ng/mL. No ex vivo HCQ effects were found on RIG-I-mediated cytokine release, but there was significant suppression of TLR7 responses and mild suppression of TLR3 and TLR9 responses. Moreover, HCQ treatment did not affect B cell and T cell proliferation. These investigations show that HCQ has clear immunosuppressive effects on human PBMCs, but the effective concentrations exceed the circulating HCQ concentrations under conventional clinical use. Of note, based on HCQ's physicochemical properties, tissue drug concentrations may be higher, potentially resulting in significant local immunosuppression. This trial is registered in the International Clinical Trials Registry Platform (ICTRP) under study number NL8726.

Salivary gland LAMP3 mRNA expression is a possible predictive marker in the response to hydroxychloroquine in Sjögren's disease

Hydroxychloroquine (HCQ) is a lysosomotropic agent that is commonly used for treating Sjögren's disease (SjD). However, its efficacy is controversial because of the divergent response to the drug among patients. In a subgroup of SjD patients, lysosome-associated membrane protein 3 (LAMP3) is elevated in expression in the salivary glands and promotes lysosomal dysregulation and lysosome-dependent apoptotic cell death. In this study, chloroquine (CQ) and its derivative HCQ were tested for their ability to prevent LAMP3-induced apoptosis, in vitro and on a mouse model of SjD. In addition, efficacy of HCQ treatment was retrospectively compared between high LAMP3 mRNA expression in minor salivary glands and those with LAMP3 mRNA levels comparable with healthy controls. Study results show that CQ treatment stabilized the lysosomal membrane in LAMP3-overexpressing cells via deactivation of cathepsin B, resulting in decreased apoptotic cell death. In mice with established SjD-like phenotype, HCQ treatment also significantly decreased apoptotic cell death and ameliorated salivary gland hypofunction. Retrospective analysis of SjD patients found that HCQ tended to be more effective in improving disease activity index, symptom severity and hypergammaglobulinemia in patients with high LAMP3 expression compared those with normal LAMP3 expression. Taken together, these findings suggested that by determining salivary gland LAMP3 mRNA level, a patient's response to HCQ treatment could be predicted. This finding may provide a novel strategy for guiding the development of more personalized medicine for SjD.

First-in-Human Study of the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of E6742, a Dual Antagonist of Toll-like Receptors 7 and 8, in Healthy Volunteers

The first-in-human phase I study for E6742, a dual toll-like receptor (TLR) 7 and TLR8 antagonist, has been conducted to assess the safety, tolerability, and pharmacokinetics of E6742 in healthy volunteers. In a single ascending dose (SAD) study, 42 subjects received 10-800 mg of E6742 in the fasted state, as well as a 100-mg cohort in the fed state for evaluating the effect of food. In a multiple ascending dose (MAD) study, 18 subjects received 100-400 mg of E6742 twice daily for 7 days. E6742 was rapidly absorbed with a median t_max ranging from 1.50 to 2.50 hours across dose groups under the fasted condition, and eliminated with a median t_½ ranging from 2.37 to 14.4 hours. After multiple oral doses, a steady state was reached by day 7. In the SAD study, dose proportionality was observed for C_max , AUC_(0-t) , and AUC_(0-inf) values of E6742 up to 800 mg, but these values were slightly less than dose proportional at 10 mg. In the MAD study, the C_max and AUC_(0-12h)ss of E6742 appeared to be almost dose proportionally increased between 100 and 200 mg, while these parameters showed more than a dose proportional increase at 400 mg. In addition to safety and good tolerability, this study demonstrated cytokine concentrations in cultured peripheral blood in response to E6742 were suppressed in a dose-dependent manner. Further clinical studies targeting systemic lupus erythematosus patients are currently underway.

Correlation between Type I Interferon Associated Factors and COVID-19 Severity

Antiviral type I interferons (IFN) produced in the early phase of viral infections effectively inhibit viral replication, prevent virus-mediated tissue damages and promote innate and adaptive immune responses that are all essential to the successful elimination of viruses. As professional type I IFN producing cells, plasmacytoid dendritic cells (pDC) have the ability to rapidly produce waste amounts of type I IFNs. Therefore, their low frequency, dysfunction or decreased capacity to produce type I IFNs might increase the risk of severe viral infections. In accordance with that, declined pDC numbers and delayed or inadequate type I IFN responses could be observed in patients with severe coronavirus disease (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), as compared to individuals with mild or no symptoms. Thus, besides chronic diseases, all those conditions, which negatively affect the antiviral IFN responses lengthen the list of risk factors for severe COVID-19. In the current review, we would like to briefly discuss the role and dysregulation of pDC/type I IFN axis in COVID-19, and introduce those type I IFN-dependent factors, which account for an increased risk of COVID-19 severity and thus are responsible for the different magnitude of individual immune responses to SARS-CoV-2.

Trial of Anti-BDCA2 Antibody Litifilimab for Cutaneous Lupus Erythematosus

BACKGROUND

Blood dendritic cell antigen 2 (BDCA2) is a receptor that is exclusively expressed on plasmacytoid dendritic cells, which are implicated in the pathogenesis of lupus erythematosus. Whether treatment with litifilimab, a humanized monoclonal antibody against BDCA2, would be efficacious in reducing disease activity in patients with cutaneous lupus erythematosus has not been extensively studied.

METHODS

In this phase 2 trial, we randomly assigned adults with histologically confirmed cutaneous lupus erythematosus with or without systemic manifestations in a 1:1:1:1 ratio to receive subcutaneous litifilimab (at a dose of 50, 150, or 450 mg) or placebo at weeks 0, 2, 4, 8, and 12. We used a dose-response model to assess whether there was a response across the four groups on the basis of the primary end point, which was the percent change from baseline to 16 weeks in the Cutaneous Lupus Erythematosus Disease Area and Severity Index-Activity score (CLASI-A; scores range from 0 to 70, with higher scores indicating more widespread or severe skin involvement). Safety was also assessed.

RESULTS

A total of 132 participants were enrolled; 26 were assigned to the 50-mg litifilimab group, 25 to the 150-mg litifilimab group, 48 to the 450-mg litifilimab group, and 33 to the placebo group. Mean CLASI-A scores for the groups at baseline were 15.2, 18.4, 16.5, and 16.5, respectively. The difference from placebo in the change from baseline in CLASI-A score at week 16 was -24.3 percentage points (95% confidence interval [CI] -43.7 to -4.9) in the 50-mg litifilimab group, -33.4 percentage points (95% CI, -52.7 to -14.1) in the 150-mg group, and -28.0 percentage points (95% CI, -44.6 to -11.4) in the 450-mg group. The least squares mean changes were used in the primary analysis of a best-fitting dose-response model across the three drug-dose levels and placebo, which showed a significant effect. Most of the secondary end points did not support the results of the primary analysis. Litifilimab was associated with three cases each of hypersensitivity and oral herpes infection and one case of herpes zoster infection. One case of herpes zoster meningitis occurred 4 months after the participant received the last dose of litifilimab.

CONCLUSIONS

In a phase 2 trial involving participants with cutaneous lupus erythematosus, treatment with litifilimab was superior to placebo with regard to a measure of skin disease activity over a period of 16 weeks. Larger and longer trials are needed to determine the effect and safety of litifilimab for the treatment of cutaneous lupus erythematosus. (Funded by Biogen; LILAC ClinicalTrials.gov number, NCT02847598.).

Hydroxychloroquine in systemic lupus erythematosus: overview of current knowledge

The antimalarial hydroxychloroquine (HCQ) has demonstrated several crucial properties for the treatment of systemic lupus erythematosus (SLE). Herein, we reviewed the main HCQ pharmacologic features, detailed its mechanism of action, and summarized the existing guidelines and recommendations for HCQ use in rheumatology with a systematic literature search for the randomized controlled trials focused on lupus. HCQ has been shown to decrease SLE activity, especially in mild and moderate disease, to prevent disease flare and to lower the long-term glucocorticoid need. The numerous benefits of HCQ are extended to pregnancy and breastfeeding period. Based on cohort studies, antithrombotic and metabolic HCQ’s effects were shown, including lipid-lowering properties, which might contribute to an improved cardiovascular risk. Moreover, early HCQ use in antinuclear antibodies positive individuals might delay the progression to SLE. Finally, HCQ has a significant favorable impact on long-term outcomes such as damage accrual and mortality in SLE. Based on these multiple benefits, HCQ is now the mainstay long-term treatment in SLE, recommended by current guidelines in all patients unless contraindications or side effects. The daily dose associated with the best compromise between efficacy and safety is matter of debate. The concern regarding retinal toxicity rather than proper efficacy data is the one that dictated the daily dosage of ⩽5 mg/kg/day actual body weight currently agreed upon.

SIDT1 plays a key role in type I IFN responses to nucleic acids in plasmacytoid dendritic cells and mediates the pathogenesis of an imiquimod-induced psoriasis model

Background

Type I IFN (IFN-I) is a family of cytokines involved in the pathogenesis of autoimmune and autoinflammatory diseases such as psoriasis. SIDT1 is an ER-resident protein expressed in the lymphoid lineage, and involved in anti-viral IFN-I responses in vivo, through an unclear mechanism. Herein we have dissected the role of SIDT1 in the natural IFN-producing cells, the plasmacytoid dendritic cells (pDC).

Methods

The function of SIDT1 in pDC was determined by silencing its expression in human primary pDC and GEN2.2 cell line. SIDT1 role in vivo was assessed using the imiquimod-induced psoriasis model in the SIDT1-deficient mice (sidt1^−/−).

Findings

Silencing of SIDT1 in GEN2.2 led to a blockade of the IFN-I response after stimulation of TLR7 and TLR9, without affecting the pro-inflammatory responses or upregulation of maturation markers. We found that SIDT1 migrates from the ER to the endosomal and lysosomal compartments together with TLR9 after CpG stimulation, participating in the access of the TLR9-CpG complex to lysosome-related vesicles, and therefore mediating the activation of TBK1 and the nuclear migration of IRF7, but not of NF-κB. sidt1^−/− mice showed a significant decrease in severity parameters of the imiquimod-induced acute psoriasis-like model, associated with a decrease in the production of IFN-I and IFN-dependent chemokines.

Interpretation

Our findings indicate that SIDT1 is at the cross-road between the IFN-I and the proinflammatory pathways and constitutes a promising drug target for psoriasis and other diseases mediated by IFN-I responses.

Funding

This work was supported by the Consejería de Salud y Familias de la Junta de Andalucía (PIER_S1149 and C2_S0050) and Instituto de Salud Carlos III (PI18/00082 and PI21/01151), partly supported by European FEDER funds, and prior funding to MEAR from the Alliance for Lupus Research and the Swedish Research Council.

CD303 (BDCA-2) - a potential novel target for therapy in hematologic malignancies

Plasmacytoid dendritic cells (pDCs) serve as immunoregulatory antigen-presenting cells that play a role in various inflammatory, viral, and malignant conditions. Malignant proliferation of pDCs is implicated in the pathogenesis of certain hematologic cancers, specifically blastic plasmacytoid dendritic cell neoplasm (BPDCN) and acute myelogenous leukemia with clonal expansion of pDC (pDC-AML). In recent years, BPDCN and pDC-AML have been successfully treated with targeted therapy of pDC-specific surface marker, CD123. However, relapsed and refractory BPDCN remains an elusive cancer, with limited therapeutic options. CD303 is another specific surface marker of human pDCs, centrally involved in antigen presentation and immune tolerance. Monoclonal antibodies directed against CD303 have been studied in preclinical models and have achieved disease control in patients with cutaneous lupus erythematosus. We performed a comprehensive review of benign and malignant disorders in which CD303 have been studied, as there may be a potential future CD303-directed therapy for many of these conditions.

Type I Interferon Production of Plasmacytoid Dendritic Cells under Control

One of the most powerful and multifaceted cytokines produced by immune cells are type I interferons (IFNs), the basal secretion of which contributes to the maintenance of immune homeostasis, while their activation-induced production is essential to effective immune responses. Although, each cell is capable of producing type I IFNs, plasmacytoid dendritic cells (pDCs) possess a unique ability to rapidly produce large amounts of them. Importantly, type I IFNs have a prominent role in the pathomechanism of various pDC-associated diseases. Deficiency in type I IFN production increases the risk of more severe viral infections and the development of certain allergic reactions, and supports tumor resistance; nevertheless, its overproduction promotes autoimmune reactions. Therefore, the tight regulation of type I IFN responses of pDCs is essential to maintain an adequate level of immune response without causing adverse effects. Here, our goal was to summarize those endogenous factors that can influence the type I IFN responses of pDCs, and thus might serve as possible therapeutic targets in pDC-associated diseases. Furthermore, we briefly discuss the current therapeutic approaches targeting the pDC-type I IFN axis in viral infections, cancer, autoimmunity, and allergy, together with their limitations defined by the Janus-faced nature of pDC-derived type I IFNs.

Interventions for cutaneous disease in systemic lupus erythematosus

BACKGROUND

Lupus erythematosus is an autoimmune disease with significant morbidity and mortality. Cutaneous disease in systemic lupus erythematosus (SLE) is common. Many interventions are used to treat SLE with varying efficacy, risks, and benefits.

OBJECTIVES

To assess the effects of interventions for cutaneous disease in SLE.

SEARCH METHODS

We searched the following databases up to June 2019: the Cochrane Skin Specialised Register, CENTRAL, MEDLINE, Embase, Wiley Interscience Online Library, and Biblioteca Virtual em Saude (Virtual Health Library). We updated our search in September 2020, but these results have not yet been fully incorporated.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of interventions for cutaneous disease in SLE compared with placebo, another intervention, no treatment, or different doses of the same intervention. We did not evaluate trials of cutaneous lupus in people without a diagnosis of SLE.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. Primary outcomes were complete and partial clinical response. Secondary outcomes included reduction (or change) in number of clinical flares; and severe and minor adverse events. We used GRADE to assess the quality of evidence.

MAIN RESULTS

Sixty-one RCTs, involving 11,232 participants, reported 43 different interventions. Trials predominantly included women from outpatient clinics; the mean age range of participants was 20 to 40 years. Twenty-five studies reported baseline severity, and 22 studies included participants with moderate to severe cutaneous lupus erythematosus (CLE); duration of CLE was not well reported. Studies were conducted mainly in multi-centre settings. Most often treatment duration was 12 months. Risk of bias was highest for the domain of reporting bias, followed by performance/detection bias. We identified too few studies for meta-analysis for most comparisons. We limited this abstract to main comparisons (all administered orally) and outcomes. We did not identify clinical trials of other commonly used treatments, such as topical corticosteroids, that reported complete or partial clinical response or numbers of clinical flares. Complete clinical response Studies comparing oral hydroxychloroquine against placebo did not report complete clinical response. Chloroquine may increase complete clinical response at 12 months' follow-up compared with placebo (absence of skin lesions) (risk ratio (RR) 1.57, 95% confidence interval (CI) 0.95 to 2.61; 1 study, 24 participants; low-quality evidence). There may be little to no difference between methotrexate and chloroquine in complete clinical response (skin rash resolution) at 6 months' follow-up (RR 1.13, 95% CI 0.84 to 1.50; 1 study, 25 participants; low-quality evidence). Methotrexate may be superior to placebo with regard to complete clinical response (absence of malar/discoid rash) at 6 months' follow-up (RR 3.57, 95% CI 1.63 to 7.84; 1 study, 41 participants; low-quality evidence). At 12 months' follow-up, there may be little to no difference between azathioprine and ciclosporin in complete clinical response (malar rash resolution) (RR 0.83, 95% CI 0.46 to 1.52; 1 study, 89 participants; low-quality evidence). Partial clinical response Partial clinical response was reported for only one key comparison: hydroxychloroquine may increase partial clinical response at 12 months compared to placebo, but the 95% CI indicates that hydroxychloroquine may make no difference or may decrease response (RR 7.00, 95% CI 0.41 to 120.16; 20 pregnant participants, 1 trial; low-quality evidence). Clinical flares Clinical flares were reported for only two key comparisons: hydroxychloroquine is probably superior to placebo at 6 months' follow-up for reducing clinical flares (RR 0.49, 95% CI 0.28 to 0.89; 1 study, 47 participants; moderate-quality evidence). At 12 months' follow-up, there may be no difference between methotrexate and placebo, but the 95% CI indicates there may be more or fewer flares with methotrexate (RR 0.77, 95% CI 0.32 to 1.83; 1 study, 86 participants; moderate-quality evidence). Adverse events Data for adverse events were limited and were inconsistently reported, but hydroxychloroquine, chloroquine, and methotrexate have well-documented adverse effects including gastrointestinal symptoms, liver problems, and retinopathy for hydroxychloroquine and chloroquine and teratogenicity during pregnancy for methotrexate.

AUTHORS' CONCLUSIONS

Evidence supports the commonly-used treatment hydroxychloroquine, and there is also evidence supporting chloroquine and methotrexate for treating cutaneous disease in SLE. Evidence is limited due to the small number of studies reporting key outcomes. Evidence for most key outcomes was low or moderate quality, meaning findings should be interpreted with caution. Head-to-head intervention trials designed to detect differences in efficacy between treatments for specific CLE subtypes are needed. Thirteen further trials are awaiting classification and have not yet been incorporated in this review; they may alter the review conclusions.

Hydroxychloroquine Effects on TLR Signalling: Underexposed but Unneglectable in COVID-19

The main basis for hydroxychloroquine (HCQ) treatment in COVID-19 is the compound's ability to inhibit viral replication in vitro. HCQ also suppresses immunity, mainly by interference in TLR signalling, but reliable clinical data on the extent and nature of HCQ-induced immunosuppression are lacking. Here, we discuss the mechanistic basis for the use of HCQ against SARS-CoV-2 in a prophylactic setting and in a therapeutic setting, at different stages of the disease. We argue that the clinical effect of prophylactic or therapeutic HCQ treatment in COVID-19 depends on the balance between inhibition of viral replication, immunosuppression, and off-target side effects, and that the outcome is probably dependent on disease stage and disease severity. This is supported by the initial outcomes of the well-designed randomized controlled trials: so far, evidence for a beneficial effect of HCQ treatment for COVID-19 is weak and conflicting.

The Role of Cutaneous Type I IFNs in Autoimmune and Autoinflammatory Diseases

IFNs are well known as mediators of the antimicrobial response but also serve as important immunomodulatory cytokines in autoimmune and autoinflammatory diseases. An increasingly critical role for IFNs in evolution of skin inflammation in these patients has been recognized. IFNs are produced not only by infiltrating immune but also resident skin cells, with increased baseline IFN production priming for inflammatory cell activation, immune response amplification, and development of skin lesions. The IFN response differs by cell type and host factors and may be modified by other inflammatory pathway activation specific to individual diseases, leading to differing clinical phenotypes. Understanding the contribution of IFNs to skin and systemic disease pathogenesis is key to development of new therapeutics and improved patient outcomes. In this review, we summarize the immunomodulatory role of IFNs in skin, with a focus on type I, and provide insight into IFN dysregulation in autoimmune and autoinflammatory diseases.

Azithromycin and glucosamine may amplify the type 1 interferon response to RNA viruses in a complementary fashion

Previous research demonstrates that, in clinically relevant concentrations, azithromycin can boost the ability of RNA viruses to induce type 1 interferon by amplifying the expression and virally-mediated activation of MDA5. O-GlcNAcylation of MAVS, a down-stream target of MDA5, renders it more effective for type 1 interferon induction. High-dose glucosamine administration up-regulates O-GlcNAcylation by increasing the cellular pool of UDP-N-acetylglucosamine. Hence, it is proposed that joint administration of azithromycin and high-dose glucosamine, early in the course of RNA virus infections, may interact in a complementary fashion to aid their control by enhancing type 1 interferon induction.

Dendritic cells as predictive markers of responsiveness to hydroxychloroquine treatment in primary cicatricial alopecia patients

Primary cicatricial alopecia (PCA) encompasses a diverse group of inflammatory diseases characterized by the irreversible replacement of hair follicle structures by fibrous tissue. Although the pathogenesis of PCA remains not fully understood, the key to its understanding might be the location of dendritic cells (DCs) inflammatory infiltrate. One of the systemic therapy of choice in PCA patients is hydroxychloroquine (HCQ). We hypothesized that DCs are implicated in PCA pathogenesis and that they might constitute the biological target of HCQ treatment. For these reasons, we investigated whether DCs could affect the antimalarial responsiveness, and if DCs might be used as predictive factor of responsiveness to HCQ. In this retrospective cohort study, 65 patients diagnosed with PCA were grouped accordingly to their response to HCQ therapy. Skin biopsies had been taken before the treatment was started. Cell count was performed on immunohistochemistry by using characteristic monoclonal antibodies to specific subpopulations of DCs. In almost every second patient (47.7%), we observed remission of the disease during HCQ treatment. The number of plasmacytoid and myeloid DCs as well as Langerhans cells in lesional skin of HCQ responders was higher in comparison with HCQ nonresponders. Moreover, in a predictive model receiver operating characteristic (ROC curve) we showed that plasmacytoid DCs might be used as a predictive factor of responsiveness to HCQ. The results of this study are important as identifying biomarkers for responsiveness to a HCQ therapy will be helpful to individualize treatment and make it more effective.

Recent advances in understanding pathogenesis and therapeutic strategies of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a multi-system-involving autoimmune disorder mainly affecting young and middle-aged women. Autoantibodies formation and immune complex deposition as well as other immune mechanisms contribute to heterogeneous clinical presentation, which leads to challenges for diagnosis and management. Although the exact pathogenesis of SLE is highly complicated, the pathophysiological understanding of SLE is constantly evolving and relevant studies were continually published, providing a better understanding of the molecular mechanisms. Moreover, new therapeutic strategies and management plans targeting pivotal factors involved in the pathogenesis of SLE got well established recently. In this article, we reviewed recent studies to provide an update in understanding pathogenesis and therapeutic strategies of SLE.

The pathogenesis of cutaneous lupus erythematosus: The aberrant distribution and function of different cell types in skin lesions

Cutaneous lupus erythematosus (CLE) is an autoimmune disease with a broad range of cutaneous manifestations. In skin lesions of CLE, keratinocytes primarily undergo apoptosis. Interferon-κ(IFN-κ) is belonged to type I interferons (type I IFNs) and is selectively produced by keratinocytes. Recently, keratinocytes selectively produced IFN-κ is identified to be a key to trigger type I interferon responses in CLE. Other immune cells such as plasmacytoid dendritic cells (pDCs) are identified to be relevant origin of type I interferons (type I IFNs) which are central to the development of CLE lesions and responsible for mediating Th1 cell activity. Other types of cells such as neutrophils, B cells and Th17 cells also are involved in the development of this disease. The close interaction of those cells composes a comprehensive and complicated network in CLE. In this review, we discussed the aberrant distribution and function of different cells types involved in this disease and will offer a new direction for research and therapy in the near future.

Altered redox regulation by Nrf2-Keap1 system in dendritic cells of systemic lupus erythematosus patients

Systemic lupus erythematosus (SLE) is an autoimmune disorder associated with inflammation and multiple organ involvement. Individually, dendritic cells (DCs) and oxidative stress have been well discussed for their critical involvement in the pathogenesis of disease but the precise impact of oxidative stress on DCs in relation to SLE disease activity is yet to be scrutinized. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/Kelch-like ECH-associated protein 1 (Keap1) pathway is the cellular mechanism to combat increased reactive oxygen species (ROS). The current study was framed in order to understand redox regulation in DCs along with an argument in context to disease activity. Here, 23 SLE patients along with 10 healthy controls were enrolled and disease activity was calculated as the recent change in SLEDAI score. We found the percentage of circulating plasmacytoid DCs (pDCs) was increased with an increase in disease activity. Altered DCs functionality along with disease activity was further supported with the differential concentration of Type I IFNs. The disease activity was positively associated with increased levels of ROS. A relevant reason for increased ROS was further explained with the decreased levels of transcription factor Nrf2. Hence, the present study suggests that SLE specific DCs displayed elevation in ROS and this outcome might be due to impaired free radical clearance by Nrf2. Correlation studies further established an association of disease activity with increased ROS, Type I IFNs levels and decreased activity of oxidative stress regulating enzymes.

Neue Erkenntnisse zur Pathogenese des SLE und ihre Auswirkungen auf die Entwicklung neuer Therapie-Konzepte

Autoantikörper sind essentiell in der Pathogenese des SLE. Sie sind das Ergebnis einer Störung des erworbenen (adaptiven) Immunsystems mit fehlender Toleranz gegen Selbst. Eine Typ-I Interferon-Signatur, die im angeborenen (innaten) Immunsystem ihren Ursprung hat, ist ein wesentlicher Treiber dieser Störung. Autoantikörper können sowohl von kurzlebigen, proliferierenden Plasmablasten, die B-Zell-Hyperaktivität widerspiegeln, als auch von langlebigen, nicht-proliferierenden Gedächtnis-Plasmazellen sezerniert werden. Gedächtnis-Plasmazellen, die in Nischen im Knochenmark und im entzündeten Gewebe lokalisiert sind, lassen sich nicht durch konventionelle Immunsuppressiva und Therapien mit B-Zellen als Target eliminieren. Konzepte, die auf die Depletion von Gedächtnis-Plasmazellen abzielen, können im Zusammenspiel mit Targets, die eine Aktivierung von autoreaktiven B-Zellen verhindern, ein kuratives Potenzial haben.

Plasmacytoid dendritic cells in the eye

Plasmacytoid dendritic cells (pDCs) are a unique subpopulation of immune cells, distinct from classical dendritic cells. pDCs are generated in the bone marrow and following development, they typically home to secondary lymphoid tissues. While peripheral tissues are generally devoid of pDCs during steady state, few tissues, including the lung, kidney, vagina, and in particular ocular tissues harbor resident pDCs. pDCs were originally appreciated for their potential to produce large quantities of type I interferons in viral immunity. Subsequent studies have now unraveled their pivotal role in mediating immune responses, in particular in the induction of tolerance. In this review, we summarize our current knowledge on pDCs in ocular tissues in both mice and humans, in particular in the cornea, limbus, conjunctiva, choroid, retina, and lacrimal gland. Further, we will review our current understanding on the significance of pDCs in ameliorating inflammatory responses during herpes simplex virus keratitis, sterile inflammation, and corneal transplantation. Moreover, we describe their novel and pivotal neuroprotective role, their key function in preserving corneal angiogenic privilege, as well as their potential application as a cell-based therapy for ocular diseases.

Treatment of cutaneous lupus erythematosus: current approaches and future strategies

PURPOSE OF REVIEW

Cutaneous lupus erythematosus (CLE) is a highly heterogeneous autoimmune disease. No specific Federal Drug Administration-approved therapies for CLE-alone are available, and resistance to conventional treatments is common. This review will summarize current treatment approaches and pending treatment strategies.

RECENT FINDINGS

Research into the pathogenesis of CLE is accelerating. A skewed type I interferon production and response contribute to CLE lesions. The pathophysiology of lesions may be similar among the lesional subtypes, and patients with a more TLR9-driven disease mechanism may have more benefit from hydroxychloroquine. Case reports continue to support the use of dapsone for CLE, especially bullous lupus erythematosus. Rituximab and Belimumab have efficacy in patients with systemic lupus erythematosus and severe active CLE. The significant role for type I interferons in CLE and encouraging clinical data suggest anifrolumab as a very promising agent for CLE. Dapirolizumab, BIIB059, Ustekinumab and Janus kinase inhibitors also have supportive early data as promising new strategies for CLE treatment.

SUMMARY

Continued research to understand the mechanisms driving CLE will facilitate the development and approval of new targets. The pipeline for new treatments is rich.

Current Paradigms of Tolerogenic Dendritic Cells and Clinical Implications for Systemic Lupus Erythematosus

Tolerogenic dendritic cells (tolDCs) are central players in the initiation and maintenance of immune tolerance and subsequent prevention of autoimmunity. Recent advances in treatment of autoimmune diseases including systemic lupus erythematosus (SLE) have focused on inducing specific tolerance to avoid long-term use of immunosuppressive drugs. Therefore, DC-targeted therapies to either suppress DC immunogenicity or to promote DC tolerogenicity are of high interest. This review describes details of the typical characteristics of in vivo and ex vivo tolDC, which will help to select a protocol that can generate tolDC with high functional quality for clinical treatment of autoimmune disease in individual patients. In addition, we discuss the recent studies uncovering metabolic pathways and their interrelation intertwined with DC tolerogenicity. This review also highlights the clinical implications of tolDC-based therapy for SLE treatment, examines the current clinical therapeutics in patients with SLE, which can generate tolDC in vivo, and further discusses on possibility and limitation on each strategy. This synthesis provides new perspectives on development of novel therapeutic approaches for SLE and other autoimmune diseases.

IMMUNOINFLAMMATORY RHEUMATIC DISEASES ASSOCIATED WITH TYPE I INTERFERON: NEW EVIDENCE

Immunoinflammatory rheumatic diseases (IIRDs) are a large group of pathological conditions with impaired immunological tolerance to autogenous tissues, leading to inflammation and irreversible organ damage. The review discusses current ideas on the role of type I interferons in the immunopathogenesis of IIRDs, primarily systemic lupus erythematosus, and new possibilities for personalized therapy.