Self protection from anti-viral responses--Ro52 promotes degradation of the transcription factor IRF7 downstream of the viral Toll-Like receptors

Clinical features of patients with systemic sclerosis positive for anti-SS-A antibody: a cohort study of 156 patients

BACKGROUND

Anti-SS-A/Ro antibody (anti-SSA), the diagnostic marker of Sjögren's syndrome (SS), is often detected in systemic sclerosis (SSc). Some patients are diagnosed with SSc/SS overlap syndromes, while there are anti-SSA-positive SSc cases without SS. In this study, we investigated the clinical characteristics of SSc with anti-SSA and clarified the clinical impact of this antibody in SSc.

METHODS

A retrospective chart review was conducted of 156 patients with SSc at Yokohama City University Hospital from 2018 to 2021. Clinical data, laboratory data, imaging, and autoantibody positivity status were collected and analysed to assess the association between these variables and anti-SSA using multivariable logistic regression analysis.

RESULTS

This cohort included 18 men and 138 women with SSc (median age, 69.0 years). Thirty-nine patients had diffuse cutaneous SSc (dcSSc) (25%), and 117 patients had limited cutaneous SSc (75%). Forty-four patients were anti-SSA-positive. Among them, 24 fulfilled the SS criteria. Multivariable logistic regression revealed that anti-SSA was statistically associated with interstitial lung disease (ILD; odds ratio [OR] = 2.67; 95% confidence interval [CI], 1.14-6.3; P = 0.024). Meanwhile, anti-SSA positivity tended to increase the development of digital ulcer (OR = 2.18; 95% CI, 0.99-4.82, P = 0.054). In the comparative analysis of the autoantibody single-positive and anti-SSA/SSc-specific autoantibody double-positive groups, the anti-SSA single-positive group showed a significantly increased risk of ILD (OR = 12.1; 95% CI, 2.13-140.57; P = 0.003). Furthermore, patients with SSc and anti-SSA indicated that anti-SSA-positive SSc without SS was strongly associated with dcSSc when compared to that in patients with SS (OR = 6.45; 95% CI, 1.23-32.60; P = 0.024).

CONCLUSIONS

Anti-SSA positivity increases the risk of organ involvement, such as ILD, in patients with SSc. Additionally, the anti-SSA-positive SSc without SS population may have more severe skin fibrosis than others. Anti-SSA may be a potential marker of ILD and skin severity in SSc.

Insight into the role of IRF7 in skin and connective tissue diseases

Interferons (IFNs) are signalling proteins primarily involved in initiating innate immune responses against pathogens and promoting the maturation of immune cells. Interferon Regulatory Factor 7 (IRF7) plays a pivotal role in the IFNs signalling pathway. The activation process of IRF7 is incited by exogenous or abnormal nucleic acids, which is followed by the identification via pattern recognition receptors (PRRs) and the ensuing signalling cascades. Upon activation, IRF7 modulates the expression of both IFNs and inflammatory gene regulation. As a multifunctional transcription factor, IRF7 is mainly expressed in immune cells, yet its presence is also detected in keratinocytes, fibroblasts, and various dermal cell types. In these cells, IRF7 is critical for skin immunity, inflammation, and fibrosis. IRF7 dysregulation may lead to autoimmune and inflammatory skin conditions, including systemic scleroderma (SSc), systemic lupus erythematosus (SLE), Atopic dermatitis (AD) and Psoriasis. This comprehensive review aims to extensively elucidate the role of IRF7 and its signalling pathways in immune cells and keratinocytes, highlighting its significance in skin-related and connective tissue diseases.

A Interacting Model: How TRIM21 Orchestrates with Proteins in Intracellular Immunity

Tripartite motif-containing protein 21 (TRIM21), identified as both a cytosolic E3 ubiquitin ligase and FcR (Fragment crystallizable receptor), primarily interacts with proteins via its PRY/SPRY domains and promotes their proteasomal degradation to regulate intracellular immunity. But how TRIM21 involves in intracellular immunity still lacks systematical understanding. Herein, it is probed into the TRIM21-related literature and raises an interacting model about how TRIM21 orchestrates proteins in cytosol. In this novel model, TRIM21 generally interacts with miscellaneous protein in intracellular immunity in two ways: For one, TRIM21 solely plays as an E3, ubiquitylating a glut of proteins that contain specific interferon-regulatory factor, nuclear transcription factor kappaB, virus sensors and others, and involving inflammatory responses. For another, TRIM21 serves as both E3 and specific FcR that detects antibody-complexes and facilitates antibody destroying target proteins. Correspondingly delineated as Fc-independent signaling and Fc-dependent signaling in this review, how TRIM21's interactions contribute to intracellular immunity, expecting to provide a systematical understanding of this important protein and invest enlightenment for further research on the pathogenesis of related diseases and its prospective application is elaborated.

Dissociating Autoantibody Responses against Ro52 Antigen in Patients with Anti-Synthetase or Anti-MDA5 Antibodies

We aimed to dissociate the autoantibody response against the Ro52 protein in patients with anti-synthetase or anti-melanoma differentiation-associated gene 5 (MDA5) antibodies to explore the potential roles of different anti-Ro52 autoantibody responses in disease subclassification. This study used a single-center, prospective myositis cohort involving 122 consecutive patients with anti-synthetase antibodies identified by RNA immunoprecipitation (RNA-IP) and 34 patients with anti-MDA5 antibodies detected using enzyme immunoassay (EIA). Anti-Ro52 antibodies were measured using commercial EIA kits, while anti-Ro/SSA antibodies were identified using RNA-IP. Clinical features and outcomes were stratified according to two different patterns of autoantibody responses against Ro52, including "isolated anti-Ro52", defined by positive anti-Ro52 and negative anti-Ro/SSA antibodies, and "anti-SSA-Ro52", defined by positive anti-Ro52 and anti-Ro/SSA antibodies. Isolated anti-Ro52 positivity was the most prevalent autoantibody response in patients with both anti-synthetase (40/122; 32.8%) and anti-MDA5 antibodies (8/34; 23.5%). Isolated anti-Ro52 or anti-SSA-Ro52 positivity was associated with Gottron's sign in patients with anti-synthetase antibodies, while in patients with anti-MDA5 antibodies, isolated anti-Ro52 positivity was associated with respiratory insufficiency at initial presentation and poor overall survival. Isolated anti-Ro52 positivity could be a potential biomarker for patient stratification; however, the clinical significance of dissociating isolated anti-Ro52 positivity from overall anti-Ro52 positivity was not evident.

The interconnected roles of TRIM21/Ro52 in systemic lupus erythematosus, primary Sjögren's syndrome, cancers, and cancer metabolism

Protein tripartite motif-containing 21 (TRIM21/Ro52), an E3 ubiquitin ligase, is an essential regulator of innate immunity, and its dysregulation is closely associated with the development of autoimmune diseases, predominantly systemic lupus erythematosus (SLE) and primary Sjögren's syndrome (pSS). TRIM21 /Ro52 also features anti-cancer and carcinogenic functions according to different malignancies. The interconnected role of TRIM21/Ro52 in regulating autoimmunity and cell metabolism in autoimmune diseases and malignancies is implicated. In this review, we summarize current findings on how TRIM21/Ro52 affects inflammation and tumorigenesis, and investigate the relationship between TRIM21/Ro52 expression and the formation of lymphoma and breast cancer in SLE and pSS populations.

Ro52/TRIM21 - From host defense to autoimmunity

Ro52 (TRIM21) belongs to the ubiquitin ligase family. This protein plays a crucial role in many immunological processes, including antibody-dependent intracellular neutralization, synergy with the complement system, antiviral response, death mediation, oxidative stress response, and protein ubiquitination. Abnormal expression of TRIM21 can break immunological tolerance and lead to the production of autoantibodies against TRIM21. Antibodies against TRIM21 are detected in various autoimmune diseases, including Sjögren's syndrome (SS), systemic lupus erythematosus (SLE), or myositis. However, anti-TRIM21 presence is not limited to autoimmune connective tissue disorders. It was observed in patients with malignancies, various cancerous processes, infectious diseases, and idiopathic interstitial pneumonia. The occurrence of TRIM21 autoantibodies is also associated with clinical features, such as the prevalence of interstitial lung diseases and cardiac or haematological involvement in connective tissue disorders. The purpose of this review was to summarize current knowledge of the immunological functions of TRIM21 and analyze the clinical implications of anti-TRIM21 antibodies in the disease course.

TRIM55 promotes noncanonical NF-κB signaling and B cell-mediated immune responses by coordinating p100 ubiquitination and processing

The ubiquitination-dependent processing of NF-κB2 (also known as p100) is a critical step in the activation of the noncanonical NF-κB pathway. We investigated the molecular mechanisms regulating this process and showed that TRIM55 was the E3 ubiquitin ligase that mediated the ubiquitination of p100 and coordinated its processing. TRIM55 deficiency impaired noncanonical NF-κB activation and B cell function. Mice with a B cell-specific Trim55 deficiency exhibited reduced germinal center formation and antibody production. These mice showed less severe symptoms than those of control mice upon the induction of a systemic lupus-like disease, suggesting B cell-intrinsic functions of TRIM55 in humoral immune responses and autoimmunity. Mechanistically, the ubiquitination of p100 mediated by TRIM55 was crucial for p100 processing by VCP, an ATPase that mediates ubiquitin-dependent protein degradation by the proteasome. Furthermore, we found that TRIM55 facilitated the interaction between TRIM21 and VCP as well as TRIM21-mediated K63-ubiquitination of VCP, both of which were indispensable for the formation of the VCP-UFD1-NPL4 complex and p100 processing. Together, our results reveal a mechanism by which TRIM55 fine-tunes p100 processing and regulates B cell-dependent immune responses in vivo, highlighting TRIM55 as a potential therapeutic target for lupus-like disease.

TRIM21 Promotes Rabies Virus Production by Degrading IRF7 through Ubiquitination

Rabies, a highly fatal zoonotic disease, is a significant global public health threat. Currently, the pathogenic mechanism of rabies has not been fully elucidated, and no effective treatment for rabies is available. Increasing evidence shows that the tripartite-motif protein (TRIM) family of proteins participates in the host's regulation of viral replication. Studies have demonstrated the upregulated expression of tripartite-motif protein 21 (TRIM21) in the brain tissue of mice infected with the rabies virus. Related studies have shown that TRIM21 knockdown inhibits RABV replication, while overexpression of TRIM21 exerted the opposite effect. Knockdown of interferon-alpha and interferon-beta modulates the inhibition of RABV replication caused by TRIM21 knockdown and promotes the replication of the virus. Furthermore, our previous study revealed that TRIM21 regulates the secretion of type I interferon during RABV infection by targeting interferon regulatory factor 7 (IRF7). IRF7 knockdown reduced the inhibition of RABV replication caused by the knockdown of TRIM21 and promoted viral replication. TRIM21 regulates RABV replication via the IRF7-IFN axis. Our study identified TRIM21 as a novel host factor required by RABV for replication. Thus, TRIM21 is a potential target for rabies treatment or management.

The Toll-like Receptor 7-Mediated Ro52 Antigen-Presenting Pathway in the Salivary Gland Epithelial Cells of Sjögren's Syndrome

OBJECTIVE

To investigate whether stimulation with toll-like receptor (TLR) 7 leads to pathways that proceed to tripartite motif-containing protein 21 (TRIM21) or Ro52/SS-A antigen presentation through major histocompatibility complex (MHC) class I in salivary gland epithelial cells (SGECs) from Sjögren's syndrome (SS) patients.

DESIGN AND METHODS

Cultured SGECs from SS patients were stimulated with TLR7 agonist, loxoribine, and interferon-β. Cell lysates immunoprecipitated by anti-MHC class I antibody were analyzed by Western blotting. The immunofluorescence of salivary gland tissue from SS and non-SS subjects and cultured TLR7-stimulated SGECs was examined.

RESULTS

Significantly increased MHC class I expression was observed in SS patients' ducts versus non-SS ducts; no significant difference was detected for ubiquitin. Upregulated MHC class I in the cell membrane and cytoplasm and augmented Ro52 expression were observed in SGECs stimulated with TLR7. The formation of peptide-loading complex (PLC), including tapasin, calreticulin, transporter associated with antigen processing 1, and endoplasmic reticulum-resident protein 57 in labial salivary glands (LSGs) from SS patients, was dominantly observed and colocalized with MHC class I, which was confirmed in TLR7-stimulated SGEC samples.

CONCLUSION

These findings suggest that the TLR7 stimulation of SS patients' SGECs advances the process toward the antigen presentation of TRIM21/Ro52-SS-A via MHC class I.

Interferon regulatory factor 7 in inflammation, cancer and infection

Interferon regulatory factor 7 (IRF7), a member of the interferon regulatory factors (IRFs) family, is located downstream of the pattern recognition receptors (PRRs)-mediated signaling pathway and is essential for the production of type I interferon (IFN-I). Activation of IRF7 inhibits various viral and bacterial infections and suppresses the growth and metastasis of some cancers, but it may also affect the tumor microenvironment and promote the development of other cancers. Here, we summarize recent advances in the role of IRF7 as a multifunctional transcription factor in inflammation, cancer and infection by regulating IFN-I production or IFN-I-independent signaling pathways.

Renal involvement in Sjőgren's syndrome: predictors and impact on patient outcomes

Renal disease in primary Sjogren's Syndrome(pSS) occurs as tubulointerstitial nephritis(TIN) or glomerulonephritis(GN). Data from India on pSS are sparse and even less on nephritis.We studied the prevalence and impact of renal disease on patient outcomes. We reviewed 179 (F:M 12.7:1, age 41.7 ± 12.9 years) patients of pSS from records at a single centre from 2000 to 2020. Data on nephritis, clinical and laboratory variables were collected from baseline visit. Outcomes studied were chronic kidney disease(CKD) and death. We identified predictors of nephritis and rising creatinine on follow-up.Fifty-four (30.17%) patients had nephritis. Their mean age was 40.19 ± 13.28 years with 157.3 person-years follow-up. Vasculitis (OR 2.33, 1.02-5.3), fatigue (OR 3.29, 1.63-6.65), ANA positivity (OR 7.79, 1-60.62), anti-Ro52 (OR 2.74, 1.18-6.39), anti-La (OR 2.13, 1.1-4.14), both Ro and La (OR 2.4, 1.23-4.69) and lymphopenia (OR 2.27, 1.16-4.41) predicted nephritis on univariate analysis. On multivariate analysis, only fatigue (OR 2.83, 1.22-6.57) and an interaction between polyarthritis and vasculitis (OR 9.17, 1.15-72.96) was associated with nephritis. Creatinine at one (1.6 ± 1.17 mg/dL vs. 0.8 ± 0.2 mg/dL) and 2 years (1.62 ± 1.19 mg/dL vs. 0.8 ± 0.2 mg/dL) follow-up was higher in the nephritis group. Baseline haematuria, leukocyturia, 24 h urinary protein and thrombocytopenia were independent predictors of rising creatinine. Six patients died and 10 developed CKD. Event-free (death or CKD) survival was 89.1% at 5 years. Patients with nephritis had worse event-free survival.Our cohort had a younger age of onset of Sjogren's syndrome and a higher prevalence of nephritis than previously reported. Fatigue, polyarthritis and vasculitis at baseline predicted the development of nephritis. Nephritis was associated with a higher probability of death or CKD.

Longitudinal proteomic profiling of the inflammatory response in dengue patients

BACKGROUND

The immunopathogenesis of dengue virus (DENV) infection remains incompletely understood. To increase our understanding of inflammatory response in non-severe dengue, we assessed longitudinal changes in the inflammatory proteome in patients with an acute DENV infection.

METHODS

Using a multiplex proximity extension assay (PEA), we measured relative levels of 368 inflammatory markers in plasma samples from hospitalized patients with non-severe DENV infection in the acute (n = 43) and convalescence (n = 35) phase of the infection and samples of healthy controls (n = 10).

RESULTS

We identified 203 upregulated and 39 downregulated proteins in acute versus convalescent plasma samples. The upregulated proteins had a strong representation of interferon (IFN) and IFN-inducible effector proteins, cytokines (e.g. IL-10, IL-33) and cytokine receptors, chemokines, pro-apoptotic proteins (e.g. granzymes) and endothelial markers. A number of differentially expressed proteins (DEPs) have not been reported in previous studies. Functional network analysis highlighted a central role for IFNγ, IL-10, IL-33 and chemokines. We identified different novel associations between inflammatory proteins and circulating concentrations of the endothelial glycocalyx disruption surrogate marker syndecan-1. Conclusion: This unbiased proteome analysis provides a comprehensive insight in the inflammatory response in DENV infection and its association with glycocalyx disruption.

AGO4 suppresses tumor growth by modulating autophagy and apoptosis via enhancing TRIM21-mediated ubiquitination of GRP78 in a p53-independent manner

Argonaute proteins, which consist of AGO1, AGO2, AGO3 and AGO4, are key players in microRNA-mediated gene silencing. So far, few non-microRNA related biological roles of AGO4 have been reported. Here, we first found that AGO4 had low expression in non-small cell lung cancer (NSCLC) patient tumor tissues and could suppress NSCLC cell proliferation and metastasis. Subsequent studies on the mechanism showed that AGO4 could interact with the tripartite motif-containing protein 21 (TRIM21) and the glucose-regulated protein 78 (GRP78). AGO4 promoted ubiquitination of GRP78 by stabilizing TRIM21, a new specific ubiquitin E3 ligase for promoting K48-linked polyubiquitination of GRP78 confirmed in this paper, which resulted in induced cell apoptosis and inhibited autophagy by activating mTOR signal pathway. Further studies showed that p53 had dominant effects on TRIM21-GRP78 axis by directly increasing the expression of TRIM21 in p53 wild-type cells and AGO4 may alternatively regulate TRIM21-GRP78 axis in p53-deficient cells. We also found that overexpression of AGO4 results in suppression of multiple p53-deficient cell growth both in vivo and vitro. Together, we showed for the first time that the AGO4-TRIM21-GRP78 axis, as a new regulatory pathway, may be a novel potential therapeutic target for p53-deficient tumor treatment.

Recent advances in cutaneous lupus

Cutaneous lupus erythematosus (CLE) is an inflammatory and autoimmune skin condition that affects patients with systemic lupus erythematosus (SLE) and exists as an isolated entity without associated SLE. Flares of CLE, often triggered by exposure to ultraviolet (UV) light result in lost productivity and poor quality of life for patients and can be associated with trigger of systemic inflammation. In the past 10 years, the knowledge of CLE etiopathogenesis has grown, leading to promising targets for better therapies. Development of lesions likely begins in a pro-inflammatory epidermis, conditioned by excess type I interferon (IFN) production to undergo increased cell death and inflammatory cytokine production after UV light exposure. The reasons for this inflammatory predisposition are not well-understood, but may be an early event, as ANA + patients without criteria for autoimmune disease exhibit similar (although less robust) findings. Non-lesional skin of SLE patients also exhibits increased innate immune cell infiltration, conditioned by excess IFNs to release pro-inflammatory cytokines, and potentially increase activation of the adaptive immune system. Plasmacytoid dendritic cells are also found in non-lesional skin and may contribute to type I IFN production, although this finding is now being questioned by new data. Once the inflammatory cycle begins, lesional infiltration by numerous other cell populations ensues, including IFN-educated T cells. The heterogeneity amongst lesional CLE subtypes isn't fully understood, but B cells appear to discriminate discoid lupus erythematosus from other subtypes. Continued discovery will provide novel targets for additional therapeutic pursuits. This review will comprehensively discuss the contributions of tissue-specific and immune cell populations to the initiation and propagation of disease.

Duck Tembusu Virus Inhibits Type I Interferon Production through the JOSD1-SOCS1-IRF7 Negative-Feedback Regulation Pathway

Duck Tembusu virus (DTMUV) is an emerging pathogenic flavivirus that mainly causes a decrease in egg production in infected waterfowl. Similar to other members of the Flaviviridae family, it can proliferate in most mammalian cells and may also pose a potential threat to nonavian animals. In previous studies, we found that DTMUV infection can upregulate suppressor of cytokine signaling 1 (SOCS1) to inhibit type I interferon (IFN) production and promote virus replication, but the specific mechanism is unclear. Furthermore, little is known about the regulatory role of ubiquitination during flavivirus infection. In this study, we found that activation of Toll-like receptor 3 (TLR3) signaling rather than type I IFN stimulation led to the upregulation of SOCS1 during DTMUV infection. Further studies revealed that JOSD1 stabilized SOCS1 expression by binding to the SH2 domain of SOCS1 and mediating its deubiquitination. In addition, JOSD1 also inhibited type I IFN production through SOCS1. Finally, SOCS1 acts as an E3 ubiquitin ligase that binds to IFN regulatory factor 7 (IRF7) through its SH2 domain and mediates K48-linked ubiquitination and proteasomal degradation of IRF7, ultimately inhibiting type I IFN production mediated by IRF7 and promoting viral proliferation. These results will enrich and deepen our understanding of the mechanism by which DTMUV antagonizes the host interferon system. IMPORTANCE DTMUV is a newly discovered flavivirus that seriously harms the poultry industry. In recent years, there have been numerous studies on the involvement of ubiquitination in the regulation of innate immunity. However, little is known about the involvement of ubiquitination in the regulation of flavivirus-induced type I IFN signaling. In this study, we found that SOCS1 was induced by TLR3 signaling during DTMUV infection. Furthermore, we found for the first time that duck SOCS1 protein was also modified by K48-linked polyubiquitination, whereas our previous study found that SOCS1 was upregulated during DTMUV infection. Further studies showed that JOSD1 stabilized SOCS1 expression by mediating the deubiquitination of SOCS1. While SOCS1 acts as a negative regulator of cytokines, we found that DTMUV utilized SOCS1 to mediate the ubiquitination and proteasomal degradation of IRF7 and ultimately inhibit type I IFN production, thereby promoting its proliferation.

Early innate immune response triggered by the human respiratory syncytial virus and its regulation by ubiquitination/deubiquitination processes

The human respiratory syncytial virus (HRSV) causes severe lower respiratory tract infections in infants and the elderly. An exuberant inadequate immune response is behind most of the pathology caused by the HRSV. The main targets of HRSV infection are the epithelial cells of the respiratory tract, where the immune response against the virus begins. This early innate immune response consists of the expression of hundreds of pro-inflammatory and anti-viral genes that stimulates subsequent innate and adaptive immunity. The early innate response in infected cells is mediated by intracellular signaling pathways composed of pattern recognition receptors (PRRs), adapters, kinases, and transcriptions factors. These pathways are tightly regulated by complex networks of post-translational modifications, including ubiquitination. Numerous ubiquitinases and deubiquitinases make these modifications reversible and highly dynamic. The intricate nature of the signaling pathways and their regulation offers the opportunity for fine-tuning the innate immune response against HRSV to control virus replication and immunopathology.

Autoantibodies in Sjögren's syndrome and its classification criteria

Sjögren's syndrome (SS) is a systemic autoimmune disease characterized by immune-mediated injury of exocrine glands. Extensive lymphocytic infiltrates may contribute to the destruction and loss of secretory function of glands. B-cell hyperactivity is a key feature of the disease resulting in the production of a diverse array of autoantibodies in these patients. Although not specific for SS, anti-Ro/SSA and anti-La/SSB antibodies have been useful biomarkers for disease classification and diagnosis. During recent years, novel autoantibodies have been discovered in SS. In this review, we summarize the historical role and clinical relevance that autoantibodies have played in the classification criteria of Sjögren's syndrome, discuss laboratory aspects in antibody detection and review the role of novel autoantibodies in predicting particular stages of the disease, clinical phenotypes and long-term complications.

Anti-Ro/SS-A Antibody is Associated with Worse Pulmonary Outcome and Reduced Overall Survival in Systemic Sclerosis

OBJECTIVE

We sought to determine the association of anti-Ro/SS-A antibody with organ involvement and disease outcome, in patients with systemic sclerosis (SSc).

METHODS

A retrospective, long-term study of a cohort of incident patients diagnosed with SSc, and continuously followed at our rheumatology clinic during 1990-2018.

RESULTS

Included were 105 patients with known anti-Ro/SS-A antibody status, 92.4% female, mean age at diagnosis 52.0±15.6 years, and median follow-up 10 years; 64% were diagnosed with limited cutaneous SSc, 18% with diffuse cutaneous SSc, and 18% had SSc siné scleroderma or undetermined disease type. Anti-Ro/SS-A antibody tested positive in 21% of patients. In univariate analysis, anti-Ro/SS-A antibody-positivity was significantly associated with SSc overlap with Sjogren's syndrome (p <0.001). Pulmonary function tests (PFT) deterioration at last encounter was significantly associated with anti-Ro/SS-A antibody-positivity. In multivariate regression for anti-Ro/SS-A antibody-positive SSc patients and disease outcome (adjusted for age>50 years, smoking, and baseline predicted forced vital capacity (pFVC) < 80%), positive anti-Ro/SS-A antibody was significantly associated with higher all-cause mortality rate (HR 5.17, CI 95% 1.18-22.67, p=0.029), and greater deterioration of pFVC defined as decrement of last available pFVC compared to first available pFVC of ≥10% (HR 3.65, CI 95% 1.07-12.38, p=0.038).

CONCLUSIONS

Anti-Ro/SS-A antibody is an independent risk factor for worse pulmonary outcome and higher all-cause mortality in patients with SSc, independent of SSc clinical and/or serological subtype.

Proteomic profiling of MIS-C patients indicates heterogeneity relating to interferon gamma dysregulation and vascular endothelial dysfunction

Multi-system Inflammatory Syndrome in Children (MIS-C) is a major complication of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection in pediatric patients. Weeks after an often mild or asymptomatic initial infection with SARS-CoV-2 children may present with a severe shock-like picture and marked inflammation. Children with MIS-C present with varying degrees of cardiovascular and hyperinflammatory symptoms. Here we perform a comprehensive analysis of the plasma proteome of more than 1400 proteins in children with SARS-CoV-2. We hypothesize that the proteome would reflect heterogeneity in hyperinflammation and vascular injury, and further identify pathogenic mediators of disease. We show that protein signatures demonstrate overlap between MIS-C, and the inflammatory syndromes macrophage activation syndrome (MAS) and thrombotic microangiopathy (TMA). We demonstrate that PLA2G2A is an important marker of MIS-C that associates with TMA. We find that IFNγ responses are dysregulated in MIS-C patients, and that IFNγ levels delineate clinical heterogeneity.

An updated review of anti-Ro52 (TRIM21) antibodies impact in connective tissue diseases clinical management

Anti-Ro52 (or anti-TRIM21) antibodies are part of the family of anti-Ro/SSA antibodies, historically markers of Sjögren syndrome and systemic lupus erythematosus. Anti-Ro52 antibodies represent one the most frequently encountered autoantibodies in patients with connective tissue disease (primary Sjögren syndrome, systemic lupus erythematosus, systemic sclerosis and idiopathic inflammatory myopathies). Because of their lack of specificity and detection in patients with non-autoimmune disorders, the usefulness of anti-Ro52 testing in connective tissue diseases is still matter of debate among clinicians and immunologists. Autoantibodies are mainly diagnostic markers for autoimmune diseases but some of them can also be directly involved in the generation of tissue damage. Over the past decade several authors reported associations of anti-Ro52 antibodies with some clinical features - especially interstitial lung disease - and survival in patients with connective tissue diseases. There is also a growing evidence of the role of anti-Ro52 antibodies in the pathogenesis of connective tissue diseases. In this review, we comprehensively discuss the clinical associations of anti-Ro52 antibodies in the different connective tissue diseases and the recent advances on their potential role in the inflammatory response.

Regulation of antiviral innate immune signaling and viral evasion following viral genome sensing

A harmonized balance between positive and negative regulation of pattern recognition receptor (PRR)-initiated immune responses is required to achieve the most favorable outcome for the host. This balance is crucial because it must not only ensure activation of the first line of defense against viral infection but also prevent inappropriate immune activation, which results in autoimmune diseases. Recent studies have shown how signal transduction pathways initiated by PRRs are positively and negatively regulated by diverse modulators to maintain host immune homeostasis. However, viruses have developed strategies to subvert the host antiviral response and establish infection. Viruses have evolved numerous genes encoding immunomodulatory proteins that antagonize the host immune system. This review focuses on the current state of knowledge regarding key host factors that regulate innate immune signaling molecules upon viral infection and discusses evidence showing how specific viral proteins counteract antiviral responses via immunomodulatory strategies.

Anti-TRIM21 antibody is associated with aberrant B-cell function and type I interferon production in systemic lupus erythematosus

BACKGROUND

TRIM21 is a member of the tripartite motif family proteins and is one of the autoantigens which react with anti-SS-A antibody (Ab) present in sera of patients with systemic lupus erythematosus (SLE) and Sjögren's syndrome. Previous studies have shown that TRIM21 dysfunction promotes aberrant B-cell differentiation and Ab production in SLE, and anti-TRIM21 Ab may be related to the TRIM21 dysfunction in human SLE pathogenesis. Here, we examined the relationship between anti-TRIM21 Ab and clinical and immunological characteristics in SLE patients.

METHODS

Twenty-seven patients with SLE (23 women and four men) before immunosuppressive therapies, who fulfilled the revised 1997 American College of Rheumatology criteria for SLE, and four healthy controls (3 women and one man) were enrolled in the study. SLE patients were divided into two groups according to the seropositivity for anti-TRIM21 Ab. Serum anti-TRIM21 Ab levels were measured using enzyme-linked immunosorbent assays. The serum levels of cytokines and immunoglobulins were measured by cytometer beads arrays. The expression levels of TRIM21 protein in peripheral mononuclear cells (PBMCs) from SLE patients were evaluated by Western blotting.

RESULTS

Sixteen and 9 patients showed seronegativity and seropositivity for anti-TRIM21 Ab, respectively. There were no significant differences in the background parameters, including female ratio, age, disease duration, SLE activity, and laboratory data between the two groups. The serum levels of interferon (IFN)-β were significantly higher in patients with anti-TRIM21 Ab as compared with those without anti-TRIM21 Ab (P = .043). The levels of IgG1 and IgA were significantly higher in SLE patients with anti-TRIM21 Ab as compared with those without anti-TRIM21 Ab (P = .0022 and .032, respectively). The PBMCs of patients with anti-TRIM21 Ab showed a significantly lower expression of TRIM21 protein as compared with those of patients without anti-TRIM21 Ab (P = .014).

CONCLUSIONS

Anti-TRIM21 Ab seropositivity was related to B-cell abnormalities and type I IFN overproduction in SLE patients. These findings suggest that anti-TRIM21 Ab may have an inhibitory effect on TRIM21 functions and be a novel biomarker for the level of dependence on type I IFN overproduction and B-cell abnormalities.

TRIM21/Ro52 - Roles in Innate Immunity and Autoimmune Disease

TRIM21 (Ro52/SSA1) is an E3 ubiquitin ligase with key roles in immune host defence, signal transduction, and possibly cell cycle regulation. It is also an autoantibody target in Sjögren's syndrome, systemic lupus erythematosus, and other rheumatic autoimmune diseases. Here, we summarise the structure and function of this enzyme, its roles in innate immunity, adaptive immunity and cellular homeostasis, the pathogenesis of autoimmunity against TRIM21, and the potential impacts of autoantibodies to this intracellular protein.

NMI Facilitates Influenza A Virus Infection by Promoting Degradation of IRF7 through TRIM21

Acute respiratory infections caused by influenza A virus (IAV) spread widely and lead to substantial morbidity and mortality. Host cell induction of type I interferon (IFN-I) plays a fundamental role in eliminating the virus during the innate antiviral response. The potential role of N-myc and STAT interactor (NMI) and its underlying mechanisms of action during IAV infection, however, remain elusive. In this study, we found that the expression of NMI increased after IAV infection. Nmi-knockout mice infected with IAV displayed increased survival rate, decreased weight loss, lower viral replication, and attenuated lung inflammation when compared with wild-type mice. Deficiency of NMI promoted the production of IFN-I and IFN-stimulated genes in vivo and in vitro. Reduced levels of NMI also resulted in an increase of the expression of IFN regulator factor (IRF) 7. Further studies have revealed that NMI could interact with IRF7 after IAV infection, and this interaction involved its NID1 and NID2 domain. In addition, NMI facilitated ubiquitination and proteasome-dependent degradation of IRF7 through recruitment of the E3 ubiquitin ligase TRIM21 (tripartite motif-containing 21) to limit the IAV-triggered innate immunity. Our findings reveal a clearer understanding of the role of NMI in regulating the host innate antiviral response and provide a potential therapeutic target for controlling IAV infection.

Epithelial-immune cell interplay in primary Sjögren syndrome salivary gland pathogenesis

In primary Sjögren syndrome (pSS), the function of the salivary glands is often considerably reduced. Multiple innate immune pathways are likely dysregulated in the salivary gland epithelium in pSS, including the nuclear factor-κB pathway, the inflammasome and interferon signalling. The ductal cells of the salivary gland in pSS are characteristically surrounded by a CD4⁺ T cell-rich and B cell-rich infiltrate, implying a degree of communication between epithelial cells and immune cells. B cell infiltrates within the ducts can initiate the development of lymphoepithelial lesions, including basal ductal cell hyperplasia. Vice versa, the epithelium provides chronic activation signals to the glandular B cell fraction. This continuous stimulation might ultimately drive the development of mucosa-associated lymphoid tissue lymphoma. This Review discusses changes in the cells of the salivary gland epithelium in pSS (including acinar, ductal and progenitor cells), and the proposed interplay of these cells with environmental stimuli and the immune system. Current therapeutic options are insufficient to address both lymphocytic infiltration and salivary gland dysfunction. Successful rescue of salivary gland function in pSS will probably demand a multimodal therapeutic approach and an appreciation of the complicity of the salivary gland epithelium in the development of pSS.

Proteomic Profiling of MIS-C Patients Reveals Heterogeneity Relating to Interferon Gamma Dysregulation and Vascular Endothelial Dysfunction

Multi-system Inflammatory Syndrome in Children (MIS-C) is a major complication of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic in pediatric patients. Weeks after an often mild or asymptomatic initial infection with SARS-CoV-2 children may present with a severe shock-like picture and marked inflammation. Children with MIS-C present with varying degrees of cardiovascular and hyperinflammatory symptoms. We performed a comprehensive analysis of the plasma proteome of more than 1400 proteins in children with SARS-CoV-2. We hypothesized that the proteome would reflect heterogeneity in hyperinflammation and vascular injury, and further identify pathogenic mediators of disease. Protein signatures demonstrated overlap between MIS-C, and the inflammatory syndromes macrophage activation syndrome (MAS) and thrombotic microangiopathy (TMA). We demonstrate that PLA2G2A is a key marker of MIS-C that associates with TMA. We found that IFNγ responses are dysregulated in MIS-C patients, and that IFNγ levels delineate clinical heterogeneity.

Negative Regulation of the Innate Immune Response through Proteasomal Degradation and Deubiquitination

The rapid and dynamic activation of the innate immune system is achieved through complex signaling networks regulated by post-translational modifications modulating the subcellular localization, activity, and abundance of signaling molecules. Many constitutively expressed signaling molecules are present in the cell in inactive forms, and become functionally activated once they are modified with ubiquitin, and, in turn, inactivated by removal of the same post-translational mark. Moreover, upon infection resolution a rapid remodeling of the proteome needs to occur, ensuring the removal of induced response proteins to prevent hyperactivation. This review discusses the current knowledge on the negative regulation of innate immune signaling pathways by deubiquitinating enzymes, and through degradative ubiquitination. It focusses on spatiotemporal regulation of deubiquitinase and E3 ligase activities, mechanisms for re-establishing proteostasis, and degradation through immune-specific feedback mechanisms vs. general protein quality control pathways.

TRIMming Type I Interferon-Mediated Innate Immune Response in Antiviral and Antitumor Defense

The tripartite motif (TRIM) family comprises at least 80 members in humans, with most having ubiquitin or SUMO E3 ligase activity conferred by their N-terminal RING domain. TRIMs regulate a wide range of processes in ubiquitination- or sumoylation-dependent manners in most cases, and fewer as adaptors. Their roles in the regulation of viral infections, autophagy, cell cycle progression, DNA damage and other stress responses, and carcinogenesis are being increasingly appreciated, and their E3 ligase activities are attractive targets for developing specific immunotherapeutic strategies for immune diseases and cancers. Given their importance in antiviral immune response, viruses have evolved sophisticated immune escape strategies to subvert TRIM-mediated mechanisms. In this review, we focus on their regulation of IFN-I-mediated innate immune response, which plays key roles in antiviral and antitumor defense.

Ubiquitination modification: critical regulation of IRF family stability and activity

Interferon regulatory factors (IRFs) play pivotal and critical roles in innate and adaptive immune responses; thus, precise and stringent regulation of the stability and activation of IRFs in physiological processes is necessary. The stability and activities of IRFs are directly or indirectly targeted by endogenous and exogenous proteins in an ubiquitin-dependent manner. However, few reviews have summarized how host E3 ligases/DUBs or viral proteins regulate IRF stability and activity. Additionally, with recent technological developments, details about the ubiquitination of IRFs have been continuously revealed. As knowledge of how these proteins function and interact with IRFs may facilitate a better understanding of the regulation of IRFs in immune responses or other biological processes, we summarized current studies on the direct ubiquitination of IRFs, with an emphasis on how these proteins interact with IRFs and affect their activities, which may provide exciting targets for drug development by regulating the functions of specific E3 ligases.

A Broader Perspective on Anti-Ro Antibodies and Their Fetal Consequences-A Case Report and Literature Review

The presence of maternal Anti-Ro/Anti-La antibodies causes a passively acquired autoimmunity that may be associated with serious fetal complications. The classic example is the autoimmune-mediated congenital heart block (CHB) which is due in most cases to the transplacental passage of Anti-Ro/Anti-La antibodies. The exact mechanisms through which these pathologic events arise are linked to disturbances in calcium channels function, impairment of calcium homeostasis and ultimately apoptosis, inflammation and fibrosis. CHB still represents a challenging diagnosis and a source of debate regarding the best management. As the third-degree block is usually irreversible, the best strategy is risk awareness and prevention. Although CHB is a rare occurrence, it affects one in 20,000 live births, with a high overall mortality rate (up to 20%, with 70% of in utero deaths). There is also concern over the lifelong consequences, as most babies need a pacemaker. This review aims to offer, apart from the data needed for a better understanding of the issue at hand, a broader perspective of the specialists directly involved in managing this pathology: the rheumatologist, the maternal-fetal specialist and the cardiologist. To better illustrate the theoretical facts presented, we also include a representative clinical case.

TRIM21 Dysfunction Enhances Aberrant B-Cell Differentiation in Autoimmune Pathogenesis

TRIM21 is one of the autoantigens that reacts with an anti-SS-A antibody (Ab) present in patients with systemic lupus erythematosus (SLE) and Sjögren's syndrome. TRIM21 is thought to play a role in B-cell proliferation and apoptosis, among other activities. Here we examined a pathological role of TRIM21 in SLE. Trim21-deficient MRL/lpr mice were generated by backcrossing Trim21-deficient C57BL/6 mice to MRL/lpr mice. The levels of serum anti-dsDNA Ab and urine protein at 28 weeks of age were significantly higher in Trim21-deficient MRL/lpr mice as compared to wild-type MRL/lpr mice (p = 0.029 and 0.003, respectively). Resting B cells from Trim21-deficient mice showed significantly higher abilities to differentiate into plasmablasts and to produce Ab as compared with control mice. Due to the reduction of TRIM21-mediated ubiquitylation, IRF5 protein expression was increased in Trim21-deficient MRL/lpr mice (p = 0.021), which correlated with increased plasmablast generation and immunoglobulin production. B cells from SLE patients with anti-TRIM21 Ab seropositivity also showed a significantly higher ability to differentiate into plasmablasts as compared with those without anti-TRIM21 Ab or healthy controls. These results suggest that TRIM21 dysfunction contributes to SLE pathogenesis by promoting B-cell differentiation, for which anti-TRIM21 Ab may be partly responsible.

To TRIM the Immunity: From Innate to Adaptive Immunity

The tripartite motif (TRIM) proteins have been intensively studied as essential modulators in various biological processes, especially in regulating a wide range of signaling pathways involved in immune responses. Most TRIM proteins have E3 ubiquitin ligase activity, mediating polyubiquitination of target proteins. Emerging evidence demonstrates that TRIM proteins play important roles in innate immunity by regulating pattern recognition receptors, vital adaptor proteins, kinases, and transcription factors in innate immune signaling pathways. Additionally, the critical roles of TRIM proteins in adaptive immunity, especially in T cell development and activation, are increasingly appreciated. In this review, we aim to summarize the studies on TRIMs in both innate and adaptive immunity, focusing on their E3 ubiquitin ligase functions in pattern recognition receptor signaling pathways and T cell functions, shedding light on the developing new strategies for modulating innate and adaptive immune responses against invading pathogens and avoiding autoimmunity.

TRIM21 Mitigates Human Lung Microvascular Endothelial Cells' Inflammatory Responses to LPS

Endothelial cell (EC) inflammation is regarded as an important pathogenic feature of many inflammatory diseases, including acute lung injury and sepsis. An increase in EC inflammation results in neutrophil infiltration from the blood to the site of inflammation, further promoting EC permeability. The ubiquitin E3 ligase TRIM21 has been implicated in human disorders; however, the roles of TRIM21 in endothelial dysfunction and acute lung injury have not been reported. Here, we reveal an antiinflammatory property of TRIM21 in a mouse model of acute lung injury and human lung microvascular ECs. Overexpression of TRIM21 by lentiviral vector infection effectively dampened LPS-induced neutrophil infiltration, cytokine release, and edema in mice. TRIM21 inhibited human lung microvascular endothelial cell inflammatory responses as evidenced by attenuation of the NF-κB pathway, release of IL-8, expression of intercellular adhesion molecules, and adhesion of monocytes to ECs. Furthermore, we demonstrated that TRIM21 was predominantly degraded by an increase in its monoubiquitination and lysosomal degradation after inflammatory stimuli. Thus, inhibition of vascular endothelial inflammation by TRIM21 provides a novel therapeutic target to lessen pulmonary inflammation.

Ehrlichia chaffeensis Outer Membrane Protein 1-Specific Human Antibody-Mediated Immunity Is Defined by Intracellular TRIM21-Dependent Innate Immune Activation and Extracellular Neutralization

Antibodies are essential for immunity against Ehrlichia chaffeensis, and protective mechanisms involve blocking of ehrlichial attachment or complement and Fcγ-receptor-dependent destruction. In this study, we determined that major outer membrane protein 1 (OMP-19) hypervariable region 1 (HVR1)-specific human monoclonal antibodies (huMAbs) are protective through conventional extracellular neutralization and, more significantly, through a novel intracellular TRIM21-mediated mechanism.

Antibodies are essential for immunity against Ehrlichia chaffeensis, and protective mechanisms involve blocking of ehrlichial attachment or complement and Fcγ-receptor-dependent destruction. In this study, we determined that major outer membrane protein 1 (OMP-19) hypervariable region 1 (HVR1)-specific human monoclonal antibodies (huMAbs) are protective through conventional extracellular neutralization and, more significantly, through a novel intracellular TRIM21-mediated mechanism. Addition of OMP-1-specific huMAb EHRL-15 (IgG1) prevented infection by blocking attachment/entry, a mechanism previously reported; conversely, OMP-1-specific huMAb EHRL-4 (IgG3) engaged intracellular TRIM21 and initiated an immediate innate immune response and rapid intracellular degradation of ehrlichiae. EHRL-4-TRIM21-mediated inhibition was significantly impaired in TRIM21 knockout THP-1 cells. EHRL-4 interacted with cytosolic Fc receptor TRIM21, observed by confocal microscopy and confirmed by co-immunoprecipitation. E. chaffeensis-EHRL-4-TRIM21 complexes caused significant upregulation of proinflammatory cytokine/chemokine transcripts and resulted in rapid (<30 min) nuclear accumulation of NF-κB and TRIM21 and ehrlichial destruction. We investigated the role of TRIM21 in the autophagic clearance of ehrlichiae in the presence of EHRL-4. Colocalization between EHRL-4-opsonized ehrlichiae, polyubiquitinated TRIM21, autophagy regulators (ULK1 and beclin 1) and effectors (LC3 and p62), and lysosome-associated membrane protein 2 (LAMP2) was observed. Moreover, autophagic flux defined by conversion of LC3I to LC3II and accumulation and degradation of p62 was detected, and EHRL-4-mediated degradation of E. chaffeensis was abrogated by the autophagy inhibitor 3-methyladenine. Our results demonstrate that huMAbs are capable of inhibiting E. chaffeensis infection by distinct effector mechanisms: extracellularly by neutralization and intracellularly by engaging TRIM21, which mediates a rapid innate immune response that mobilizes the core autophagy components, triggering localized selective autophagic degradation of ehrlichiae.

[Association of polymorphisms of the TRIM21 gene with the severity of dry keratoconjunctivitis in rheumatoid arthritis and Sjogren's disease]

Ophthalmologic manifestation of Sjogren's disease (SD) and rheumatoid arthritis (RA) is dry keratoconjunctivitis (dry eye disease; DED).

PURPOSE

To study the relationship of polymorphic markers rs7947461 (C/T), rs915956 (C/T), rs4144331 (C/A) of the TRIM21 gene with the severity of DED in patients with RA and SD.

MATERIAL AND METHODS

The study included 70 patients with RA (n=27) and SD (n=43). The control group consisted of volunteers without a history of RA or SD (n=35). Alleles of the polymorphic marker C660T rs7947461 of the TRIM21 gene were identified using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method; alleles of the polymorphic marker rs915956 (C/T) and rs4144331 (C/A) of the TRIM21 gene were identified by analyzing DNA melting curves.

RESULTS

An association was found between the predisposing genotype (TT) of rs7947461 polymorphic marker and the risk of developing severe DED. The AA genotype of rs4144331 polymorphic marker was found only in severe DED (c²=7.74; OR=17.46, CI_95%=1.96-318.38, p=0.02).

CONCLUSION

An association was established between rs7947461 (rs660) and rs4144331 and the risk of developing severe DED.

TRIM8 is required for virus-induced IFN response in human plasmacytoid dendritic cells

Plasmacytoid dendritic cells (pDCs) play a crucial role in antiviral innate immunity through their unique capacity to produce large amounts of type I interferons (IFNs) upon viral detection. Tripartite motif (TRIM) proteins have recently come forth as important modulators of innate signaling, but their involvement in pDCs has not been investigated. Here, we performed a rationally streamlined small interfering RNA (siRNA)-based screen of TRIM proteins in human primary pDCs to identify those that are critical for the IFN response. Among candidate hits, TRIM8 emerged as an essential regulator of IFN regulatory factor 7 (IRF7) function. Mechanistically, TRIM8 protects phosphorylated IRF7 (pIRF7) from proteasomal degradation in an E3 ubiquitin ligase-independent manner by preventing its recognition by the peptidyl-prolyl isomerase Pin1. Our findings uncover a previously unknown regulatory mechanism of type I IFN production in pDCs by which TRIM8 and Pin1 oppositely regulate the stability of pIRF7.

TRIM21-From Intracellular Immunity to Therapy

Tripartite motif containing-21 (TRIM21) is a cytosolic ubiquitin ligase and antibody receptor that provides a last line of defense against invading viruses. It does so by acting as a sensor that intercepts antibody-coated viruses that have evaded extracellular neutralization and breached the cell membrane. Upon engagement of the Fc of antibodies bound to viruses, TRIM21 triggers a coordinated effector and signaling response that prevents viral replication while at the same time inducing an anti-viral cellular state. This dual effector function is tightly regulated by auto-ubiquitination and phosphorylation. Therapeutically, TRIM21 has been shown to be detrimental in adenovirus based gene therapy, while it may be favorably utilized to prevent tau aggregation in neurodegenerative disorders. In addition, TRIM21 may synergize with the complement system to block viral replication as well as transgene expression. TRIM21 can also be utilized as a research tool to deplete specific proteins in cells and zebrafish embryos. Here, we review our current biological understanding of TRIM21 in light of its versatile functions.

Enhanced T-cell proliferation and IL-6 secretion mediated by overexpression of TRIM21 in oral lesions of patients with oral lichen planus

BACKGROUNDS

To explore the expression and functions of the tripartite motif-containing protein 21 (TRIM21) in oral lichen planus(OLP) lesions.

METHODS

Paraffin sections of buccal mucosa samples from 15 cases of reticular oral lichen planus (OLP) patients and 10 healthy controls were used for immunohistochemistry to determine expression and distribution of TRIM21. Buccal mucosae from 11 OLP patients and seven healthy controls were analyzed by qPCR to quantify its gene expression. Peripheral blood mononuclear cells and CD3+ cells from four pairs of age- and sex-matched OLP patients and healthy controls were isolated for immunocytochemistry and culture. Following lentivirus-mediated overexpression of TRIM21 gene in CD3+ cells, CCK-8 was applied to evaluate cell proliferation. Cytokines including IL-2, IL-4, IL-5, IL-6, IL-10, TNF-α, and IFN-γ in the supernatants were measured by the cytometric bead array and verified by ELISA.

RESULTS

A larger number of TRIM21-positive cells infiltrating the lamina propria were observed in OLP lesions by immunohistochemistry than those of healthy controls. Significantly higher transcription of TRIM21 was revealed by qPCR. TRIM21 overexpression in CD3+ cells significantly enhanced the proliferation and IL-6 secretion in CD3+ cells from 12 to 72 hours.

CONCLUSION

Overexpressed TRIM21 in OLP may be a primary proinflammatory molecule rather than a secondary and inducible regulatory factor in immunopathogenesis of OLP.

Regulating IRFs in IFN Driven Disease

The Interferon regulatory factors (IRFs) are a family of transcription factors that play pivotal roles in many aspects of the immune response, including immune cell development and differentiation and regulating responses to pathogens. Three family members, IRF3, IRF5, and IRF7, are critical to production of type I interferons downstream of pathogen recognition receptors that detect viral RNA and DNA. A fourth family member, IRF9, regulates interferon-driven gene expression. In addition, IRF4, IRF8, and IRF5 regulate myeloid cell development and phenotype, thus playing important roles in regulating inflammatory responses. Thus, understanding how their levels and activity is regulated is of critical importance given that perturbations in either can result in dysregulated immune responses and potential autoimmune disease. This review will focus the role of IRF family members in regulating type I IFN production and responses and myeloid cell development or differentiation, with particular emphasis on how regulation of their levels and activity by ubiquitination and microRNAs may impact autoimmune disease.

Activation of Toll-like receptor 7 signaling in labial salivary glands of primary Sjögren's syndrome patients

The aim of this study was to determine the expressions of Toll-like receptors (TLRs) 7-9 and type I interferon (IFN) signal in labial salivary glands (LSGs) and cultured salivary gland epithelial cells (SGECs) from primary Sjögren's syndrome (pSS) patients. We performed an immunohistochemistry analysis of LSGs from 11 patients with pSS as defined by American-European Consensus Group classification criteria and five healthy subjects. The pSS patients' SGECs were analyzed by immunofluorescence and western blotting. IFN-α expression was examined by immunosorbent assay and flow cytometry. Mononuclear cells (MNCs) from pSS patients' LSGs showed TLR-7-dominant expression. B cells, plasma cells and plasmacytoid dendritic cells (pDCs) co-expressed with TLR-7. Myeloid differentiation primary response gene 88 (MyD88), tumor necrosis factor receptor-associated factor 6 (TRAF6) and interferon regulatory factor 7 (IRF7) co-expressed with the pDC marker CD303 in LSGs. Ducts from pSS patients dominantly expressed TLR-7, and TLR-7 in the ducts co-expressed with MyD88, TRAF6 and IRF7. Type I IFNs including IFN-α and IFN-β were detected in MNCs and ducts in pSS patients' LSGs. Increased TRAF6 expression and the nuclear translocation of IRF7 in SGECs were detected by immunofluorescence following loxoribine (a TLR-7 ligand) stimulation despite IFN-β pretreatment. Western blotting showed increased TRAF6 expression in SGECs following IFN-β and loxoribine stimulation. Although no increase in IFN-α was detected in supernatant from stimulated SGECs, the IFN-α in supernatant from stimulated peripheral blood pDCs from pSS patients was significantly increased. Our findings suggest that TLR-7 is dominantly expressed in both MNCs and ducts with downstream signals for type I IFNs, indicating that TLR7-dominant innate immunity is related to the development of sialadenitis in pSS.

TRIM21 mediates antibody inhibition of adenovirus-based gene delivery and vaccination

Viral-based delivery vectors have huge potential in the treatment of human disease. Adenoviral vectors specifically have proven highly efficacious in delivering corrected genes, as part of gene therapy, and vaccine epitopes for treating cancer and infectious disease. A principal obstacle to their widespread use is that antibodies potently neutralize them, limiting treatment to naïve patients. How antibodies block adenovirus-based transduction has long remained a mystery because, even though they prevent transgene expression, they do not prevent transgene delivery into target tissue. Here we show that the cytosolic antibody receptor TRIM21 is responsible for intercepting adenoviral gene therapy and vaccine vectors and neutralizing them. Gene KO of TRIM21 or a single-antibody mutation that prevents interaction is sufficient to restore transgene expression.

Adenovirus has enormous potential as a gene-therapy vector, but preexisting immunity limits its widespread application. What is responsible for this immune block is unclear because antibodies potently inhibit transgene expression without impeding gene transfer into target cells. Here we show that antibody prevention of adenoviral gene delivery in vivo is mediated by the cytosolic antibody receptor TRIM21. Genetic KO of TRIM21 or a single-antibody point mutation is sufficient to restore transgene expression to near-naïve immune levels. TRIM21 is also responsible for blocking cytotoxic T cell induction by vaccine vectors, preventing a protective response against subsequent influenza infection and an engrafted tumor. Furthermore, adenoviral preexisting immunity can lead to an augmented immune response upon i.v. administration of the vector. Transcriptomic analysis of vector-transduced tissue reveals that TRIM21 is responsible for the specific up-regulation of hundreds of immune genes, the majority of which are components of the intrinsic or innate response. Together, these data define a major mechanism underlying the preimmune block to adenovirus gene therapy and demonstrate that TRIM21 efficiently blocks gene delivery in vivo while simultaneously inducing a rapid program of immune transcription.

Modulation of Apoptosis by Cytotoxic Mediators and Cell-Survival Molecules in Sjögren's Syndrome

The pathogenesis of Sjögren’s syndrome (SS) involves multiple factors including genetic background, cell death, and exocrine dysfunction. We here discuss apoptotic control in exocrine glands in SS by showing various pro- and anti-apoptotic pathways. Although the membrane-bound and soluble form of the Fas/Fas ligand system is a leading player with activation of the death domain and caspase 8/3 cleavage, the role of soluble Fas/FasL (including its polymorphism) in apoptosis is controversial. The tumor necrosis factor related apoptosis-inducing ligand (TRAIL)-mediated apoptosis of salivary gland epithelial cells (SGECs) involves a mitochondrial pathway that includes caspase 9 cleavage. The involvement of innate immunity cells such as toll-like receptors (TLRs) has been investigated; TLR2-4 and TLR7-9 are associated with the induction of inflammation in exocrine glands of SS patients. TLR3 has the potential to induce the apoptosis of SS patients’ SGECs. Linkage of epidermal growth factor (EGF) was shown in exocrine glands in SS, and it inhibited the Fas/FasL system with the help of cell-survival factors. TLR3 has dual actions to cause inflammation as well as apoptosis, which are inhibited by EGF. In conclusion, apoptosis in exocrine glands of SS patients is tightly controlled by balance of pro-apoptotic signals and growth factor.

Investigation of MicroRNA in Mitochondrial Apoptotic Pathway in Systemic Lupus Erythematosus

Background

Accumulating evidence indicates that microRNAs play a pivotal role in the pathogenesis of systemic lupus erythematosus (SLE). This study tested the hypothesis that microRNA is associated with the mitochondrial apoptotic pathway in patients with SLE.

Methods

Thirteen patients were in the clinical comparison study and microRNA study and overall 19 patients in the study of intracellular protein. Levels of microRNAs were determined by miRNeasy kit in 13 patients with SLE and 29 volunteer normal controls. Intracellular levels of caspase-9, caspase-10, MAVS, MDA5, and pIRF7 in mononuclear cells from 19 patiens and the SLE disease activity index (SLEDAI) were determined in all SLE patients. Correlation analyses were performed among microRNAs, intracellular adaptor proteins, and caspase levels and mean SLEDAI.

Results

The ΔCT, defined by test reading difference between the target and the internal control microRNA (miR-451a), of miR-21-5p, miR-150-5p, and miR221-3p were significantly higher in plasma from SLE patients than in normal controls. miR-150-5pΔCT was positively correlated with both CRP and SLEDAI value. miR-150-5pΔCT was negatively associated with MAVS 70 kD. Caspase-10 protein levels were negatively associated with plasma miR-22-3pΔCT and miR-21-5pΔCT levels.

Conclusions

Our study confirmed the hypothesis that these microRNAs were associated with the mitochondrial apoptotic pathway in SLE. miR-150-5pΔCT was positively associated with SLE disease activity and it was negatively correlated with MAVS 70 kD, which may facilitate viral survival and further enhance inflammation. On the other hand, miR-22-3pΔCT and miR-21-5pΔCT, were negatively correlated with caspase-10 levels, which may repress extrinsic apoptosis and increase cell survival.

TRIM Proteins and Their Roles in Antiviral Host Defenses

Tripartite motif (TRIM) proteins are a versatile family of ubiquitin E3 ligases involved in a multitude of cellular processes. Studies in recent years have demonstrated that many TRIM proteins play central roles in the host defense against viral infection. While some TRIM proteins directly antagonize distinct steps in the viral life cycle, others regulate signal transduction pathways induced by innate immune sensors, thereby modulating antiviral cytokine responses. Furthermore, TRIM proteins have been implicated in virus-induced autophagy and autophagy-mediated viral clearance. Given the important role of TRIM proteins in antiviral restriction, it is not surprising that several viruses have evolved effective maneuvers to neutralize the antiviral action of specific TRIM proteins. Here, we describe the major antiviral mechanisms of TRIM proteins as well as viral strategies to escape TRIM-mediated host immunity.

Update on Pathogenesis of Sjogren's Syndrome

Sjogren's syndrome is a common autoimmune disease that presents with sicca symptoms and extraglandular features. Sjogren's syndrome is presumably as common as RA; yet it is poorly understood, underdiagnosed and undertreated. From the usual identity as an autoimmune exocrinopathy to its most recent designate as an autoimmune epithelitis - the journey of SS is complex. We herein review some of the most important milestones that have shed light on different aspects of pathogenesis of this enigmatic disease. This includes role of salivary gland epithelial cells, and their interaction with cells of the innate and adaptive immune system. Non-immune factors acting in concert or in parallel with immune factors may also be important. The risk genes identified so far have only weak association, nevertheless advances in genetics have enhanced understanding of disease mechanisms. Role of epigenetic and environmental role factors is also being explored. SS has also some unique features such as congenital heart block and high incidence of lymphoma; disease mechanisms accounting for these manifestations are also reviewed.

SOCS1 and SOCS3 Target IRF7 Degradation To Suppress TLR7-Mediated Type I IFN Production of Human Plasmacytoid Dendritic Cells

Type I IFN production of plasmacytoid dendritic cells (pDCs) triggered by TLR-signaling is an essential part of antiviral responses and autoimmune reactions. Although it was well-documented that members of the cytokine signaling (SOCS) family regulate TLR-signaling, the mechanism of how SOCS proteins regulate TLR7-mediated type I IFN production has not been elucidated yet. In this article, we show that TLR7 activation in human pDCs induced the expression of SOCS1 and SOCS3. SOCS1 and SOCS3 strongly suppressed TLR7-mediated type I IFN production. Furthermore, we demonstrated that SOCS1- and SOCS3-bound IFN regulatory factor 7, a pivotal transcription factor of the TLR7 pathway, through the SH2 domain to promote its proteasomal degradation by lysine 48-linked polyubiquitination. Together, our results demonstrate that SOCS1/3-mediated degradation of IFN regulatory factor 7 directly regulates TLR7 signaling and type I IFN production in pDCs. This mechanism might be targeted by therapeutic approaches to either enhance type I IFN production in antiviral treatment or decrease type I IFN production in the treatment of autoimmune diseases.