Search

Background: Intervertebral disc degeneration (IDD) is widely regarded as the primary contributor to low back pain(LBP). As an immune-privileged organ, upon the onset of IDD, various components of the nucleus pulposus (NP) are exposed to the host's immune system, accumulating cytokines. Cytokines facilitate intercellular communication within the immune system, induce immune cells polarisation, and exacerbate oxidative stress in IDD., Methods: Machine learning was used to identify crucial immune cells. Subsequently, Immune Response Enrichment Analysis (IREA) was conducted on the key immune cells to determine their cytokine responses and polarisation states in IDD. "CellChat" package facilitated the analysis of cell-cell communication. Differential gene expression analysis, PPI network, GO and KEGG pathway enrichment analysis, GSVA, co-expressed gene analysis and key gene-related networks were also performed to explore hub genes and their associated functions. Lastly, the differential expression and functions of key genes were validated through in vitro and in vivo experiments., Results: Through multiple machine learning methods, monocytes were identified as the crucial immune cells in IDD, exhibiting significant differentiation capacity. IREA revealed that monocytes in IDD polarize into an IFN-a1 and IFN-b enriched Mono-a state, potentially intensifying inflammation. Cell-cell communication analysis uncovered alteration in ANNEXIN pathway and a reduction in CXCL signaling between macrophages and monocytes, suggesting immune response dysregulation. Furthermore, ten algorithms identified three hub genes. Both experiments conducted in vitro and in vivo have conclusively shown that IRF7 serves as a crucial target for the treatment of IDD, and its knockdown alleviates IDD. Eight small-molecule drugs were predicted to have therapeutic potential for IDD., Conclusion: These findings offer a multidimensional understanding of the pathogenesis of IDD, pinpointing monocytes and key genes as potential diagnostic and therapeutic targets. They provide novel insights into potential diagnostic and therapeutic targets for IDD., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Xu, Li, Yuan, Zhao, Pan, Pan, Xiong, Tan, Li, Huang, Chen, Miao, He and Cheng.)

Background: The incidence of inflammatory bowel disease (IBD) is on the rise in developing countries, and investigating the underlying mechanisms of IBD is essential for the development of targeted therapeutic interventions. Interferon regulatory factor 7 (IRF7) is known to exert pro-inflammatory effects in various autoimmune diseases, yet its precise role in the development of colitis remains unclear., Methods: We analyzed the clinical significance of IRF7 in ulcerative colitis (UC) by searching RNA-Seq databases and collecting tissue samples from clinical UC patients. And, we performed dextran sodium sulfate (DSS)-induced colitis modeling using WT and Irf7 -/- mice to explore the mechanism of IRF7 action on colitis., Results: In this study, we found that IRF7 expression is significantly reduced in patients with UC, and also demonstrated that Irf7 -/- mice display heightened susceptibility to DSS-induced colitis, accompanied by elevated levels of colonic and serum pro-inflammatory cytokines, suggesting that IRF7 is able to inhibit colitis. This increased susceptibility is linked to compromised intestinal barrier integrity and impaired expression of key molecules, including Muc2, E-cadherin, β-catenin, Occludin, and Interleukin-28A (IL-28A), a member of type III interferon (IFN-III), but independent of the deficiency of classic type I interferon (IFN-I) and type II interferon (IFN-II). The stimulation of intestinal epithelial cells by recombinant IL-28A augments the expression of Muc2, E-cadherin, β-catenin, and Occludin. The recombinant IL-28A protein in mice counteracts the heightened susceptibility of Irf7 -/- mice to colitis induced by DSS, while also elevating the expression of Muc2, E-cadherin, β-catenin, and Occludin, thereby promoting the integrity of the intestinal barrier., Conclusion: These findings underscore the pivotal role of IRF7 in preserving intestinal homeostasis and forestalling the onset of colitis., (© 2024. The Author(s).)

The production of type I interferon is tightly regulated to prevent excessive immune activation. However, the role of selective autophagy receptor SQSTM1 in this regulation in teleost remains unknown. In this study, we cloned the triploid fish SQSTM1 (3nSQSTM1), which comprises 1371 nucleotides, encoding 457 amino acids. qRT-PCR data revealed that the transcript levels of SQSTM1 in triploid fish were increased both in vivo and in vitro following spring viraemia of carp virus (SVCV) infection. Immunofluorescence analysis confirmed that 3nSQSTM1 was mainly distributed in the cytoplasm. Luciferase reporter assay results showed that 3nSQSTM1 significantly blocked the activation of interferon promoters induced by 3nMDA5, 3nMAVS, 3nTBK1, and 3nIRF7. Co-immunoprecipitation assays further confirmed that 3nSQSTM1 could interact with both 3nTBK1 and 3nIRF7. Moreover, upon co-transfection, 3nSQSTM1 significantly inhibited the antiviral activity mediated by TBK1 and IRF7. Mechanistically, 3nSQSTM1 decreased the TBK1 phosphorylation and its interaction with 3nIRF7, thereby suppressing the subsequent antiviral response. Notably, we discovered that 3nSQSTM1 also interacted with SVCV N and P proteins, and these viral proteins may exploit 3nSQSTM1 to further limit the host's antiviral innate immune responses. In conclusion, our study demonstrates that 3nSQSTM1 plays a pivotal role in negatively regulating the interferon signaling pathway by targeting 3nTBK1 and 3nIRF7., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Toll-like receptor 7 (Tlr7) deficiency-accelerated severe COVID-19 is associated with reduced production of interferons (IFNs). However, the underlying mechanisms remain elusive. To address these questions, we utilize Tlr7 and Irf7 deficiency mice, single-cell RNA analysis together with bone marrow transplantation approaches. We demonstrate that at the early phase of infection, SARS-CoV-2 causes the upregulation of Tlr7, Irf7, and IFN pathways in the lungs of the infected mice. The deficiency of Tlr7 and Irf7 globally and/or in immune cells in mice increases the severity of COVID-19 via impaired IFN activation in both immune and/or non-immune cells, leading to increased lung viral loads. These effects are associated with reduced IFN alpha and gamma levels in the circulation. The deficiency of Tlr7 tends to cause the reduced production and nuclear translocation of interferon regulatory factor 7 (IRF7) in the lungs of the infected mice, indicative of reduced IRF7 activation. Despite higher amounts of lung viral antigen, Tlr7 or Irf7 deficiency resulted in substantially reduced production of antibodies against SARS-CoV-2, thereby delaying the viral clearance. These results highlight the importance of the activation of TLR7 and IRF7 leading to IFN production on the development of innate and adaptive immunity against COVID-19., (© 2024. The Author(s).)

Outbreaks of short beak and dwarfism syndrome (SBDS), caused by a novel goose parvovirus (NGPV), have occurred in China since 2015. The NGPV, a single-stranded DNA virus, is thought to be vertically transmitted. However, the mechanism of NGPV immune evasion remains unclear. In this study, we investigated the impact of NGPV infection on the Cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway in duck embryonic fibroblast (DEF) cells. Our findings demonstrate that NGPV infection stimulates the mRNA expression of cGAS but results in weak IFN-β induction. NGPV impedes the expression of IFN-β and downstream interferon-stimulated genes, thereby reducing the secretion of IFN-β induced by interferon-stimulating DNA (ISD) and poly (I: C). RNA-seq results show that NGPV infection downregulates interferon mRNA expression while enhancing the mRNA expression of inflammatory factors. Additionally, the results of viral protein over-expression indicate that VP1 exhibits a remarkable ability to inhibit IFN-β expression compared to other viral proteins. Results indicated that only the intact VP1 protein could inhibit the expression of IFN-β, while the truncated proteins VP1U and VP2 do not possess such characteristics. The immunoprecipitation experiment showed that both VP1 and VP2 could interact with IRF7 protein, while VP1U does not. In summary, our findings indicate that NGPV infection impairs the host's innate immune response by potentially modulating the expression and secretion of interferons and interferon-stimulating factors via IRF7 molecules, which are regulated by the VP1 protein., Competing Interests: DISCLOSURES We certify that there is no conflict of interest with any financial organization regarding the material discussed in the manuscript., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

TLRs are the most thoroughly studied group of pattern-recognition receptors that play a central role in innate immunity. Among them, TLR10 (CD290) remains the only TLR family member without a known ligand and clearly defined functions. One major impediment to studying TLR10 is its absence in mice. A recent study on TLR10 knock-in mice demonstrated its intrinsic inhibitory role in B cells, indicating that TLR10 is a potential drug target in autoimmune diseases. In this study, we interrogated the expression and function of TLR10 in human plasmacytoid dendritic cells (pDCs). We have seen that primary human pDCs, B cells, and monocytes constitutively express TLR10. Upon preincubation with an anti-TLR10 Ab, production of cytokines in pDCs was downregulated in response to stimulation with DNA and RNA viruses. Upon further investigation into the possible mechanism, we documented phosphorylation of STAT3 upon Ab-mediated engagement of TLR10. This leads to the induction of inhibitory molecule suppressor of cytokine signaling 3 (SOCS3) expression. We have also documented the inhibition of nuclear translocation of transcription factor IFN regulatory factor 7 (IRF7) in pDCs following TLR10 engagement. Our data provide the (to our knowledge) first evidence that TLR10 is constitutively expressed on the surface of human pDCs and works as a regulator of their innate response. Our findings indicate the potential of harnessing the function of pDCs by Ab-mediated targeting of TLR10 that may open a new therapeutic avenue for autoimmune disorders., (Copyright © 2024 by The American Association of Immunologists, Inc.)

Osteoclasts are multinucleated bone-resorbing cells, and their formation is tightly regulated to prevent excessive bone loss. However, the mechanisms by which osteoclast formation is restricted remain incompletely determined. Here, we found that sterol regulatory element binding protein 2 (SREBP2) functions as a negative regulator of osteoclast formation and inflammatory bone loss. Cholesterols and SREBP2, a key transcription factor for cholesterol biosynthesis, increased in the late phase of osteoclastogenesis. The ablation of SREBP2 in myeloid cells resulted in increased in vivo and in vitro osteoclastogenesis, leading to low bone mass. Moreover, deletion of SREBP2 accelerated inflammatory bone destruction in murine inflammatory osteolysis and arthritis models. SREBP2-mediated regulation of osteoclastogenesis is independent of its canonical function in cholesterol biosynthesis but is mediated, in part, by its downstream target, interferon regulatory factor 7 (IRF7). Taken together, our study highlights a previously undescribed role of the SREBP2-IRF7 regulatory circuit as a negative feedback loop in osteoclast differentiation and represents a novel mechanism to restrain pathological bone destruction., (© 2024. The Author(s).)

Analyzing changes in gene expression within specific brain regions of individuals with Type 2 Diabetes (T2DM) who do not exhibit significant cognitive deficits can yield valuable insights into the mechanisms underlying the progression towards a more severe phenotype. In this study, transcriptomic analysis of the cortex and hippocampus of mice with long-term T2DM revealed alterations in the expression of 28 genes in the cerebral cortex and 15 genes in the hippocampus. Among these genes, six displayed consistent changes in both the cortex and hippocampus: Interferon regulatory factor 7 (Irf7), Hypoxia-inducible factor 3 alpha (Hif-3α), period circadian clock 2 (Per2), xanthine dehydrogenase (Xdh), and Transforming growth factor β-stimulated clone 22/TSC22 (Tsc22d3) were upregulated, while Claudin-5 (Cldn5) was downregulated. Confirmation of these changes was achieved through RT-qPCR. At the protein level, CLDN5 and IRF7 exhibited similar alterations, with CLDN5 being downregulated and IRF7 being upregulated. In addition, the hippocampus and cortex of the T2DM mice showed decreased levels of IκBα, implying the involvement of NF-κB pathways as well. Taken together, these results suggest that the weakening of the blood-brain barrier and an abnormal inflammatory response via the Interferon 1 and NF-κB pathways underlie cognitive impairment in individuals with long-standing T2DM., (© 2024. The Author(s).)

Aim: The main focus of this study is to explore the molecular mechanism of IRF7 regulation on RPS18 transcription in M1-type macrophages in pancreatic adenocarcinoma (PAAD) tissue, as well as the transfer of RPS18 by IRF7 via exosomes to PAAD cells and the regulation of ILF3 expression., Methods: By utilising single-cell RNA sequencing (scRNA-seq) data and spatial transcriptomics (ST) data from the Gene Expression Omnibus database, we identified distinct cell types with significant expression differences in PAAD tissue. Among these cell types, we identified those closely associated with lipid metabolism. The differentially expressed genes within these cell types were analysed, and target genes relevant to prognosis were identified. Flow cytometry was employed to assess the expression levels of target genes in M1 and M2 macrophages. Cell lines with target gene knockout were constructed using CRISPR/Cas9 editing technology, and cell lines with target gene knockdown and overexpression were established using lentiviral vectors. Additionally, a co-culture model of exosomes derived from M1 macrophages with PAAD cells was developed. The impact of M1 macrophage-derived exosomes on the lipid metabolism of PAAD cells in the model was evaluated through metabolomics analysis. The effects of M1 macrophage-derived exosomes on the viability, proliferation, division, migration and apoptosis of PAAD cells were assessed using MTT assay, flow cytometry, EdU assay, wound healing assay, Transwell assay and TUNEL staining. Furthermore, a mouse PAAD orthotopic implantation model was established, and bioluminescence imaging was utilised to assess the influence of M1 macrophage-derived exosomes on the intratumoural formation capacity of PAAD cells, as well as measuring tumour weight and volume. The expression of proliferation-associated proteins in tumour tissues was examined using immunohistochemistry., Results: Through combined analysis of scRNA-seq and ST technologies, we discovered a close association between M1 macrophages in PAAD samples and lipid metabolism signals, as well as a negative correlation between M1 macrophages and cancer cells. The construction of a prognostic risk score model identified RPS18 and IRF7 as two prognostically relevant genes in M1 macrophages, exhibiting negative and positive correlations, respectively. Mechanistically, it was found that IRF7 in M1 macrophages can inhibit the transcription of RPS18, reducing the transfer of RPS18 to PAAD cells via exosomes, consequently affecting the expression of ILF3 in PAAD cells. IRF7/RPS18 in M1 macrophages can also suppress lipid metabolism, cell viability, proliferation, migration, invasion and intratumoural formation capacity of PAAD cells, while promoting cell apoptosis., Conclusion: Overexpression of IRF7 in M1 macrophages may inhibit RPS18 transcription, reduce the transfer of RPS18 from M1 macrophage-derived exosomes to PAAD cells, thereby suppressing ILF3 expression in PAAD cells, inhibiting the lipid metabolism pathway, and curtailing the viability, proliferation, migration, invasion of PAAD cells, as well as enhancing cell apoptosis, ultimately inhibiting tumour formation in PAAD cells in vivo. Targeting IRF7/RPS18 in M1 macrophages could represent a promising immunotherapeutic approach for PAAD in the future., (© 2024 The Author(s). Clinical and Translational Medicine published by John Wiley & Sons Australia, Ltd on behalf of Shanghai Institute of Clinical Bioinformatics.)

Background: It is known that nerve signals arising from sites of inflammation lead to persistent changes in the spinal cord and contribute to the amplification and persistence of pain. Nevertheless, the underlying mechanisms have not yet been completely elucidated. We identified differentially expressed genes in the lumbar (L4-L6) segment of the spinal cord from complete Freund's adjuvant (CFA) rats compared to control animals via high throughput sequencing. Based on differential gene expression analysis, we selected interferon regulatory factor 7 (IRF7) for follow-up experiments to explore its antinociceptive potential., Methods: An animal model of inflammatory pain was induced by intraplantar injection of CFA. We evaluated the effects of adeno-associated viral (AAV)-mediated overexpression of IRF7 in the spinal cord on pain-related behavior after CFA injection. Moreover, the activation of the nuclear factor-κB (NF-κB) and the expression of inflammatory cytokines were investigated to understand the underlying mechanisms related to the contribution of IRF7 to inflammatory pain., Results: CFA intraplantar injection caused a significant decrease in the level of spinal IRF7, which is mainly expressed in the dorsal horn neurons and astrocytes. Moreover, IRF7 overexpression significantly attenuated pain-related behaviors, as well as the activity of NF-κB/p65 and the production of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in the spinal cord of CFA rats., Conclusions: Our data indicated that spinal IRF7 plays an important role in the regulation of inflammatory pain. Thus, IRF7 overexpression at the spinal cord level might represent a potential target for the treatment of inflammatory pain., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Type I interferons exhibit anti-proliferative and anti-cancer activities, but their detailed regulatory mechanisms in cancer have not been fully elucidated yet. RNA binding proteins are master orchestrators of gene regulation, which are closely related to tumor progression. Here we show that the upregulated RNA binding protein RBM45 correlates with poor prognosis in breast cancer. Depletion of RBM45 suppresses breast cancer progression both in cultured cells and xenograft mouse models. Mechanistically, RBM45 ablation inhibits breast cancer progression through regulating type I interferon signaling, particularly by elevating IFN-β production. Importantly, RBM45 recruits TRIM28 to IRF7 and stimulates its SUMOylation, thereby repressing IFNB1 transcription. Loss of RBM45 reduced the SUMOylation of IRF7 by reducing the interaction between TRIM28 and IRF7 to promote IFNB1 transcription, leading to the inhibition of breast cancer progression. Taken together, our finding uncovers a vital role of RBM45 in modulating type I interferon signaling and cancer aggressive progression, implicating RBM45 as a potential therapeutic target in breast cancer., Competing Interests: Declaration of competing interest The authors declare no competing interests., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background: Retinal pigment epithelial (RPE) cells have a pivotal function in preserving the equilibrium of the retina and moderating the immunological interaction between the choroid and the retina. This study primarily focuses on delineating the protective effect offered by Kaempferol (Kae) against RPE cell damage., Methods: Bioinformatics analysis was performed on the GSE30719 dataset to identify hub genes associated with RPE. Subsequently, we analyzed the impact of Kae on RPE apoptosis, cell viability, and inflammatory response through cell experiments, and explored the interaction between hub genes and Kae., Results: Based on the GSE30719 dataset, nine hub genes ( ISG15 , IFIT1 , IFIT3 , STAT1 , OASL , RSAD2 , IRF7 , MX2 , and MX1 ) were identified, all of which were highly expressed in the GSE30719 case group. Kae could boost the proliferative activity of RPE cells caused by lipopolysaccharide (LPS), as well as reduce apoptosis and the generation of inflammatory factors (tumor necrosis factor receptor (TNFR), interleukin-1beta (IL-1β)) and cytokines (IL-1, IL-6, IL-12). STAT1 was shown to inhibit cell proliferation, promote apoptosis, and secrete IL-1/IL-6/IL-12 in LPS-induced RPE cells. Moreover, IRF7 was found to interact with STAT1 in LPS-induced RPE cells, and STAT1 could maintain IRF7 levels through deubiquitination. In addition, we also found that the protective effect of Kae on LPS-induced RPE cell injury was mediated through STAT1/IRF7 axis., Conclusion: This study provided evidence that Kae protects RPE cells via regulating the STAT1/IRF7 signaling pathways, indicating its potential therapeutic relevance in the diagnosis and management of retinal disorders linked with RPE cell damage., Competing Interests: The authors declare no conflict of interest., (© 2024 The Author(s). Published by IMR Press.)

Interferon regulatory factor 7 (IRF7) is considered the master regulator of virus-induced interferon (IFN) production. However, to avoid an autoimmune response, the expression of IRF7 must be tightly controlled. In this study, we report that zebrafish ubiquitin-specific protease 8 (USP8) promotes IRF7 degradation through an autophagy-lysosome-dependent pathway to inhibit IFN production. First, zebrafish usp8 is induced upon spring viremia of carp virus (SVCV) infection and polyinosinic/polycytidylic acid (poly I:C) stimulation. Second, overexpression of USP8 suppresses SVCV or poly I:C-mediated IFN expression. Mechanistically, USP8 interacts with IRF7 and promotes its degradation via an autophagy-lysosome-dependent pathway. Finally, USP8 significantly suppresses cellular antiviral responses and enhances SVCV proliferation. In summary, our discoveries offer a perspective on the role of zebrafish USP8 and provide additional understanding of the regulation of IRF7 in host antiviral immune response., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

During virus-host co-evolution, viruses have developed multiple strategies to dampen IFN response and prevent its antiviral activity in host cells. To date, the interactions between host IFN response and the immune evasion strategies exploited by fish iridoviruses still remain largely uncertain. Here, a potential immune evasion protein candidate of Singapore grouper iridovirus (SGIV), VP82 (encoded by SGIV ORF82) was screened and its roles during viral replication were investigated in detail. Firstly, VP82 overexpression dramatically decreased IFN or ISRE promoter activity and the transcription levels of IFN stimulated genes (ISGs) stimulated by grouper cyclic GMP-AMP synthase (EccGAS)/stimulator of interferon genes (EcSTING), TANK-binding kinase 1 (EcTBK1), IFN regulatory factor 3 (EcIRF3)and EcIRF7. Secondly, Co-IP assays indicated that VP82 interacted with EcIRF3 and EcIRF7, but not EcSTING and EcTBK1, which was consistent with the co-localization between VP82 and EcIRF3 or EcIRF7. Furthermore, VP82 promoted the degradation of EcIRF3 and EcIRF7 in a dose-dependent manner via the autophagy pathway. Finally, VP82 overexpression accelerated SGIV replication, evidenced by the increased transcriptions of viral core genes and viral production. Moreover, the antiviral action of EcIRF3 or EcIRF7 was significantly depressed in VP82 overexpressed cells. Together, VP82 was speculated to exert crucial roles for SGIV replication by inhibiting the IFN response via the degradation of IRF3 and IRF7. Our findings provided new insights into understanding the immune evasion strategies utilized by fish iridovirus through IFN regulation., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Viral infections pose a significant threat to public health, and the production of interferons represents one of the most critical antiviral innate immune responses of the host. Consequently, the screening and identification of compounds or reagents that induce interferon production are of paramount importance. This study commenced with the cultivation of host bacterium 15,597, followed by the infection of Escherichia coli with the MS2 bacteriophage. Utilizing the J2 capture technique, a class of dsRNA mixtures (MS2+15,597) was isolated from the E. coli infected with the MS2 bacteriophage. Subsequent investigations were conducted on the immunostimulatory activity of the MS2+15,597 mixture. The results indicated that the dsRNA mixtures (MS2+15,597) extracted from E. coli infected with the MS2 bacteriophage possess the capability to activate innate immunity, thereby inducing the production of interferon-β. These dsRNA mixtures can activate the RIG-I and TLR3 pattern recognition receptors, stimulating the expression of interferon stimulatory factors 3/7, which in turn triggers the NF-κB signaling pathway, culminating in the cellular production of interferon-β to achieve antiviral effects. This study offers novel insights and strategies for the development of broad-spectrum antiviral drugs, potentially providing new modalities for future antiviral therapies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

IFN regulatory factor 7 (IRF7) exerts anti-infective effects by promoting the production of IFNs in various bacterial and viral infections, but its role in highly morbid and fatal Candida albicans infections is unknown. We unexpectedly found that Irf7 gene expression levels were significantly upregulated in tissues or cells after C. albicans infection in humans and mice and that IRF7 actually exacerbates C. albicans infection in mice independent of its classical function in inducing IFNs production. Compared to controls, Irf7-/- mice showed stronger phagocytosis of fungus, upregulation of C-type lectin receptor CD209 expression, and enhanced P53-AMPK-mTOR-mediated autophagic signaling in macrophages after C. albicans infection. The administration of the CD209-neutralizing Ab significantly hindered the phagocytosis of Irf7-/- mouse macrophages, whereas the inhibition of p53 or autophagy impaired the killing function of these macrophages. Thus, IRF7 exacerbates C. albicans infection by compromising the phagocytosis and killing capacity of macrophages via regulating CD209 expression and p53-AMPK-mTOR-mediated autophagy, respectively. This finding reveals a novel function of IRF7 independent of its canonical IFNs production and its unexpected role in enhancing fungal infections, thus providing more specific and effective targets for antifungal therapy., (Copyright © 2024 by The American Association of Immunologists, Inc.)

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., (© 2024 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Macrophage proinflammatory activation contributes to the pathology of severe acute pancreatitis (SAP) and, simultaneously, macrophage functional changes, and increased pyroptosis/necrosis can further exacerbate the cellular immune suppression during the process of SAP, where cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) plays an important role. However, the function and mechanism of cGAS-STING in SAP-induced lung injury (LI) remains unknown., Methods: Lipopolysaccharide (LPS) was combined with caerulein-induced SAP in wild type, cGAS -/- and sting -/- mice. Primary macrophages were extracted via bronchoalveolar lavage and peritoneal lavage. Ana-1 cells were pretreated with LPS and stimulated with nigericin sodium salt to induce pyroptosis in vitro., Results: SAP triggered NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome activation-mediated pyroptosis of alveolar and peritoneal macrophages in mouse model. Knockout of cGAS/STING could ameliorate NLRP3 activation and macrophage pyroptosis. In addition, mitochondrial (mt)DNA released from damaged mitochondria further induced macrophage STING activation in a cGAS- and dose-dependent manner. Upregulated STING signal can promote NLRP3 inflammasome-mediated macrophage pyroptosis and increase serum interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α levels and, thus, exacerbate SAP-associated LI (SAP-ALI). Downstream molecules of STING, IRF7, and IRF3 connect the mtDNA-cGAS-STING axis and the NLRP3-pyroptosis axis., Conclusions: Negative regulation of any molecule in the mtDNA-cGAS-STING-IRF7/IRF3 pathway can affect the activation of NLRP3 inflammasomes, thereby reducing macrophage pyroptosis and improving SAP-ALI in mouse model., (© 2024. The Author(s).)

Psoriasis is a chronic, recurrent, inflammatory dermatosis accompanied by excessive activation of dendritic cells (DCs), which are primarily responsible for initiating an immune response. The bromodomain and extraterminal domain (BET) family plays a pivotal role in the transcriptional regulation of inflammation and its inhibitors can downregulate DCs maturation and activation. Here we investigated the effect of NHWD-870, a potent BET inhibitor, on inflammation in an imiquimod (IMQ)-induced psoriasis-like mouse model and murine bone marrow-derived dendritic cells (BMDCs) stimulated by lipopolysaccharide (LPS) and IMQ. Application of NHWD-870 significantly ameliorated IMQ-triggered skin inflammation in mice, and markers associated with DC maturation (CD40, CD80 and CD86) were decreased in skin lesions, spleen and lymph nodes. Additionally, NHWD-870 reduced LPS or IMQ induced DCs maturation and activation in vitro, with lower expression of inflammatory cytokines [interleukin (IL)-12, IL-23, tumor necrosis factor-α, IL-6, IL-1β, chemokine (C-X-C motif) ligand (CXCL)9 and CXCL10]. In addition, we found that interferon regulatory factor 7 (IRF7) significantly increased during DCs maturation, and inhibition of IRF7 could impair BMDCs maturation and activation. What's more, IRF7 was highly expressed in both psoriatic patients and IMQ-induced psoriasis-like mice. Single-cell RNA sequencing of normal and psoriatic skin demonstrated that IRF7 expression was increased in DCs of psoriatic skin. While NHWD-870 could inhibit IRF7 and phosphorylated-IRF7 expression in vivo and in vitro. These results indicate that NHWD-870 suppresses the maturation and activation of DCs by decreasing IRF7 proteins which finally alleviates psoriasis-like skin lesions, and NHWD-870 may be a potent therapeutic drug for psoriasis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

p53 is mutated in half of cancer cases. However, no p53-targeting drugs have been approved. Here, we reposition decitabine for triple-negative breast cancer (TNBC), a subtype with frequent p53 mutations and extremely poor prognosis. In a retrospective study on tissue microarrays with 132 TNBC cases, DNMT1 overexpression was associated with p53 mutations (P = 0.037) and poor overall survival (OS) (P = 0.010). In a prospective DEciTabinE and Carboplatin in TNBC (DETECT) trial (NCT03295552), decitabine with carboplatin produced an objective response rate (ORR) of 42% in 12 patients with stage IV TNBC. Among the 9 trialed patients with available TP53 sequencing results, the 6 patients with p53 mutations had higher ORR (3/6 vs. 0/3) and better OS (16.0 vs. 4.0 months) than the patients with wild-type p53. In a mechanistic study, isogenic TNBC cell lines harboring DETECT-derived p53 mutations exhibited higher DNMT1 expression and decitabine sensitivity than the cell line with wild-type p53. In the DETECT trial, decitabine induced strong immune responses featuring the striking upregulation of the innate immune player IRF7 in the p53-mutated TNBC cell line (upregulation by 16-fold) and the most responsive patient with TNBC. Our integrative studies reveal the potential of repurposing decitabine for the treatment of p53-mutated TNBC and suggest IRF7 as a potential biomarker for decitabine-based treatments., (© 2023. Higher Education Press.)

Interferon (IFN) regulatory factors (IRF) are key transcription factors in cellular antiviral responses. IRF7, a virus-inducible IRF, expressed primarily in myeloid cells, is required for transcriptional induction of interferon α and antiviral genes. IRF7 is activated by virus-induced phosphorylation in the cytoplasm, leading to its translocation to the nucleus for transcriptional activity. Here, we revealed a nontranscriptional activity of IRF7 contributing to its antiviral functions. IRF7 interacted with the pro-inflammatory transcription factor NF-κB-p65 and inhibited the induction of inflammatory target genes. Using knockdown, knockout, and overexpression strategies, we demonstrated that IRF7 inhibited NF-κB-dependent inflammatory target genes, induced by virus infection or toll-like receptor stimulation. A mutant IRF7, defective in transcriptional activity, interacted with NF-κB-p65 and suppressed NF-κB-induced gene expression. A single-action IRF7 mutant, active in anti-inflammatory function, but defective in transcriptional activity, efficiently suppressed Sendai virus and murine hepatitis virus replication. We, therefore, uncovered an anti-inflammatory function for IRF7, independent of transcriptional activity, contributing to the antiviral response of IRF7., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: The production of interferons (IFNs) is essential for the control of viral infections, and interferon regulatory factor 7 (IRF7) is considered as a vital regulator for the transcription of type I IFNs. Amphibians appear to possess a highly expanded type I IFN repertoire, consisting of intron-containing genes as observed in fish, and intronless genes as in other higher vertebrates. However, the knowledge on transcriptional regulatory mechanism of these two types of type I IFN genes is rather scarce in amphibians., Methods and Results: A IRF7 gene named as Np-IRF7 was identified in Tibetan frog (Nanorana parkeri), and bioinformatic analysis revealed that the predicted protein of Np-IRF7 contains several important structural features known in IRF7. Expression analysis showed that Np-IRF7 gene was widely expressed and rapidly induced by poly(I:C) in different organs/tissues. Interestingly, luciferase reporter assay revealed that intronless IFN promoters were more effectively activated than intron-containing IFN promoter in Np-IRF7-transfected cells. Moreover, the overexpression of Np-IRF7 could induce the expression of ISGs and suppress the replication of FV3 in A6 cells., Conclusion: Np-IRF7 is indeed the ortholog of known IRF7, and IRF7 is structurally conserved in different lineages of vertebrates. Np-IRF7 played distinct roles in the activation of intron-containing and intronless type I IFN promoters, thus inducing the expression of interferon-stimulated antiviral effectors and providing a protection against ranavirus infection. The present research thus contributes to a better understanding of regulatory function of IRF7 in the IFN-mediated antiviral response of anuran amphibians., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Introduction: While TLR ligands derived from microbial flora and pathogens are important activators of the innate immune system, a variety of factors such as intracellular bacteria, viruses, and parasites can induce a state of hyperreactivity, causing a dysregulated and potentially life-threatening cytokine over-response upon TLR ligand exposure. Type I interferon (IFN-αβ) is a central mediator in the induction of hypersensitivity and is strongly expressed in splenic conventional dendritic cells (cDC) and marginal zone macrophages (MZM) when mice are infected with adenovirus. This study investigates the ability of adenoviral infection to influence the activation state of the immune system and underlines the importance of considering this state when planning the treatment of patients., Methods: Infection with adenovirus-based vectors (Ad) or pretreatment with recombinant IFN-β was used as a model to study hypersensitivity to lipopolysaccharide (LPS) in mice, murine macrophages, and human blood samples. The TNF-α, IL-6, IFN-αβ, and IL-10 responses induced by LPS after pretreatment were measured. Mouse knockout models for MARCO, IFN-αβR, CD14, IRF3, and IRF7 were used to probe the mechanisms of the hypersensitive reaction., Results: We show that, similar to TNF-α and IL-6 but not IL-10, the induction of IFN-αβ by LPS increases strongly after Ad infection. This is true both in mice and in human blood samples ex vivo, suggesting that the regulatory mechanisms seen in the mouse are also present in humans. In mice, the scavenger receptor MARCO on IFN-αβ-producing cDC and splenic marginal zone macrophages is important for Ad uptake and subsequent cytokine overproduction by LPS. Interestingly, not all IFN-αβ-pretreated macrophage types exposed to LPS exhibit an enhanced TNF-α and IL-6 response. Pretreated alveolar macrophages and alveolar macrophage-like murine cell lines (MPI cells) show enhanced responses, while bone marrow-derived and peritoneal macrophages show a weaker response. This correlates with the respective absence or presence of the anti-inflammatory IL-10 response in these different macrophage types. In contrast, Ad or IFN-β pretreatment enhances the subsequent induction of IFN-αβ in all macrophage types. IRF3 is dispensable for the LPS-induced IFN-αβ overproduction in infected MPI cells and partly dispensable in infected mice, while IRF7 is required. The expression of the LPS co-receptor CD14 is important but not absolutely required for the elicitation of a TNF-α over-response to LPS in Ad-infected mice., Conclusion: Viral infections or application of virus-based vaccines induces type I interferon and can tip the balance of the innate immune system in the direction of hyperreactivity to a subsequent exposure to TLR ligands. The adenoviral model presented here is one example of how multiple factors, both environmental and genetic, affect the physiological responses to pathogens. Being able to measure the current reactivity state of the immune system would have important benefits for infection-specific therapies and for the prevention of vaccination-elicited adverse effects., (© 2024 The Author(s). Published by S. Karger AG, Basel.)

The innate antiviral response to RNA viruses is initiated by sensing of viral RNAs by RIG-I-like receptors and elicits type I interferon (IFN) production, which stimulates the expression of IFN-stimulated genes that orchestrate the antiviral response to prevent systemic infection. Negative regulation of type I IFN and its master regulator, transcription factor IRF7, is essential to maintain immune homeostasis. We previously demonstrated that AIP (aryl hydrocarbon receptor interacting protein) functions as a negative regulator of the innate antiviral immune response by binding to and sequestering IRF7 in the cytoplasm, thereby preventing IRF7 transcriptional activation and type I IFN production. However, it remains unknown how AIP inhibition of IRF7 is regulated. We show here that the kinase TBK1 phosphorylates AIP and Thr40 serves as the primary target for TBK1 phosphorylation. AIP Thr40 plays critical roles in regulating AIP stability and mediating its interaction with IRF7. The AIP phosphomimetic T40E exhibited increased proteasomal degradation and enhanced interaction with IRF7 compared with wildtype AIP. AIP T40E also blocked IRF7 nuclear translocation, which resulted in reduced type I IFN production and increased viral replication. In sharp contrast, AIP phosphonull mutant T40A had impaired IRF7 binding, and stable expression of AIP T40A in AIP-deficient mouse embryonic fibroblasts elicited a heightened type I IFN response and diminished RNA virus replication. Taken together, these results demonstrate that TBK1-mediated phosphorylation of AIP at Thr40 functions as a molecular switch that enables AIP to interact with and inhibit IRF7, thus preventing overactivation of type I IFN genes by IRF7., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Importance: Viral encephalomyelitis outcome is dependent on host responses to neuronal infection. Interferon (IFN) is an important component of the innate response, and IFN regulatory factor (IRF) 7 is an inducible transcription factor for the synthesis of IFN-α. IRF7-deficient mice develop fatal paralysis after CNS infection with Sindbis virus, while wild-type mice recover. Irf7 -/- mice produce low levels of IFN-α but high levels of IFN-β with induction of IFN-stimulated genes, so the reason for this difference is not understood. The current study shows that Irf7 -/- mice developed inflammation earlier but failed to clear virus from motor neuron-rich regions of the brainstem and spinal cord. Levels of IFN-γ and virus-specific antibody were comparable, indicating that IRF7 deficiency does not impair expression of these known viral clearance factors. Therefore, IRF7 is either necessary for the neuronal response to currently identified mediators of clearance or enables the production of additional antiviral factor(s) needed for clearance., Competing Interests: DEG is a member of advisory boards for GSK and Takeda Pharmaceuticals.

Background: Type I interferons (IFN-I) are fundamental in controlling viral infections but fatal interferonopathy is restricted in the immune-privileged central nervous system (CNS). In contrast to the well-established role of Interferon Regulatory Factor 7 (IRF7) in the regulation of IFN-I response in the periphery, little is known about the specific function in the CNS., Methods: To investigate the role for IRF7 in antiviral response during neurotropic virus infection, mice deficient for IRF3 and IRF7 were infected systemically with Langat virus (LGTV). Viral burden and IFN-I response was analyzed in the periphery and the CNS by focus formation assay, RT-PCR, immunohistochemistry and in vivo imaging. Microglia and infiltration of CNS-infiltration of immune cells were characterized by flow cytometry., Results: Here, we demonstrate that during infection with the neurotropic Langat virus (LGTV), an attenuated member of the tick-borne encephalitis virus (TBEV) subgroup, neurons do not rely on IRF7 for cell-intrinsic antiviral resistance and IFN-I induction. An increased viral replication in IRF7-deficient mice suggests an indirect antiviral mechanism. Astrocytes rely on IRF7 to establish a cell-autonomous antiviral response. Notably, the loss of IRF7 particularly in astrocytes resulted in a high IFN-I production. Sustained production of IFN-I in astrocytes is independent of an IRF7-mediated positive feedback loop., Conclusion: IFN-I induction in the CNS is profoundly regulated in a cell type-specific fashion., (© 2023. BioMed Central Ltd., part of Springer Nature.)

Interferon regulatory factor 7 (IRF7) regulates type I interferon (IFN) genes via combining to the ISRE region in the immune response against bacteria. Streptococcus iniae is one of the dominant pathogenic bacteria of yellowfin seabream, Acanthopagrus latus. However, the regulatory mechanisms of A. latus IRF7 (AlIRF7) mediated by the type I IFN signalling pathway against S. iniae was ambiguously. In the present study, IRF7, and two IFNa3s (IFNa3 and IFNa3-like) were authenticated from A. latus. The total length of AlIRF7 cDNA is 2142 bp, containing a 1314 bp open reading frame (ORF) encoding an inferred 437 amino acids (aa). Three typical regions, a serine-rich domain (SRD), a DNA-binding domain (DBD), and an IRF association domain (IAD), are conserved in AlIRF7. Furthermore, AlIRF7 is fundamentally expressed in various kinds of organs, with high levels in the spleen and liver. Additionally, S. iniae challenge promoted AlIRF7 expression in the spleen, liver, kidney, and brain. AlIRF7 is confirmed to be located at the nucleus and cytoplasm by overexpression of AlIRF7. Moreover, truncation mutation analyses shows that the regions, -821 bp to +192 bp and -928 bp to +196 bp, were known as core promoters from AlIFNa3 and AlIFNa3-like, respectively. The point mutation analyses and electrophoretic mobile shift assay (EMSA) verified that AlIFNa3 and AlIFNa3-like transcriptions are depended on the M2/5 and M2/3/4 binding sites with AlIRF7 regulation, respectively. Additionally, an overexpression experiment showed that AlIRF7 can dramatically decrease the mRNA levels of two AlIFNa3s and interferon signalling molecules. These results suggest that two IFNa3s may mediate the regulation of AlIRF7 in the immune responses of A. latus against S. iniae infection., Competing Interests: Declaration of competing interest The authors declare no competing interests., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Sterile alpha motif and HD domain-containing protein 1 (SAMHD1) restricts human immunodeficiency virus type 1 (HIV-1) infection by reducing the intracellular dNTP pool. We have shown that SAMHD1 suppresses nuclear factor kappa-B activation and type I interferon (IFN-I) induction by viral infection and inflammatory stimuli. However, the mechanism by which SAMHD1 inhibits IFN-I remains unclear. Here, we show that SAMHD1 inhibits IFN-I activation induced by the mitochondrial antiviral-signaling protein (MAVS). SAMHD1 interacted with MAVS and suppressed MAVS aggregation in response to Sendai virus infection in human monocytic THP-1 cells. This resulted in increased phosphorylation of TANK binding kinase 1 (TBK1), inhibitor of nuclear factor kappa-B kinase epsilon (IKKε), and IFN regulatory factor 3 (IRF3). SAMHD1 suppressed IFN-I activation induced by IKKε and prevented IRF7 binding to the kinase domain of IKKε. We found that SAMHD1 interaction with the inhibitory domain (ID) of IRF7 (IRF7-ID) was necessary and sufficient for SAMHD1 suppression of IRF7-mediated IFN-I activation in HEK293T cells. Computational docking and molecular dynamics simulations revealed possible binding sites between IRF7-ID and full-length SAMHD1. Individual substitution of F411, E416, or V460 in IRF7-ID significantly reduced IRF7 transactivation activity and SAMHD1 binding. Furthermore, we investigated the role of SAMHD1 inhibition of IRF7-mediated IFN-I induction during HIV-1 infection. We found that THP-1 cells lacking IRF7 expression had reduced HIV-1 infection and viral transcription compared to control cells, indicating a positive role of IRF7 in HIV-1 infection. Our findings suggest that SAMHD1 suppresses IFN-I induction through the MAVS, IKKε, and IRF7 signaling axis., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

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.

Among cancer immunotherapy, which has received great attention in recent years, cancer vaccines can potentially prevent recurrent tumors by using the exquisite power and specificity of the immune system. Specifically, whole tumor cell vaccines (WTCVs) based on surgically resected tumors have been considered to elicit robust anti-tumor immune responses by exposing various tumor-associated antigens to host immunity. However, most tumors have little immunogenicity because of immunoediting by continuous interactions with host immunity; thus, preparing WTCVs based on patient-derived non-modified tumors cannot prevent tumor onset. Hence, the immunogenicity of tumor cells must be improved for effective WTCVs. In this study, we indicate the importance of the interferon regulatory factor 7 (Irf7) axis, including Irf7 and its downstream factors, within tumor cells in regulating immunogenicity. Indeed, WTCVs that augmented the Irf7 axis have exerted remarkable recurrence-preventive effects when vaccinated after tumor inactivation by radiation. Most notably, vaccination with murine colon cancer cells that enhanced the Irf7 axis prevented the development of challenged tumors in all mice and resulted in a 100% survival rate during the observation period. Furthermore, the mechanism leading to vaccine effectiveness was mediated by interferon-gamma-producing B cells. This study provides novel insights into how to enhance tumor immunogenicity and use WTCVs as recurrence prophylaxis., Competing Interests: No potential conflict of interest was reported by the authors., (© 2023 The Author(s). Published with license by Taylor & Francis Group, LLC.)

Ferroptosis is implicated in the progression of ulcerative colitis (UC), and interferon regulatory factor 7 (IRF7) contributes to cell death. This study probed the mechanism of IRF7 in ferroptosis of colonic epithelial cells (ECs) in mice with dextran sodium sulfate (DSS)-induced UC. The UC mouse model and the in vitro ferroptosis model were respectively established by DSS feeding and the treatment with FIN56 (a ferroptosis inducer). Results of quantitative real-time polymerase chain reaction and western blotting revealed the upregulation of IRF7 and solute carrier family 11 member 2 (SLC11A2/NRAMP2/DMT1) and the downregulation of microRNA (miR)-375-3p in DSS-treated mice and FIN56-treated ECs. Silencing of IRF7 improved the symptoms of UC in DSS-induced mice and decreased the levels of tumor necrosis factor α, interleukin 6, monocyte chemoattractant protein 1, and interleukin 1β, reactive oxygen species, iron ions, lipid peroxidation, and increased glutathione and glutathione peroxidase 4. Chromatin immunoprecipitation and dual-luciferase assays showed that binding of IRF7 to the miR-375-3p promoter inhibited miR-375-3p expression, and miR-375-3p suppressed SLC11A2 transcription. The rescue experiments revealed that knockdown of miR-375-3p neutralized the role of silencing IRF7 in alleviating ferroptosis of colonic ECs. Overall, IRF7 upregulated SLC11A2 transcription by inhibiting miR-375-3p expression, thereby prompting ferroptosis of colonic ECs and UC progression in DSS-treated mice.

Type I interferon (IFN) response is the first line of host-based innate immune defense against viral infections. However, viruses have developed multiple strategies to counter host IFN responses, so they may continue infecting hosts via effective replication. Avian reovirus (ARV), an RNA virus, causes viral arthritis or tenosynovitis in chickens. Previous studies have shown that ARV is highly resistant to the antiviral effects of IFN. However, the underlying mechanisms that enable ARV to block the IFN pathway remain unclear. In this study, we found that ectopic expression of ARV protein, σA, significantly inhibited the production of IFN-β induced by melanoma-differentiation-associated gene 5 (MDA5) and poly(I·C). Knockdown of σA during ARV infection enhances the IFN-β response and suppresses viral replication. ARV σA inhibited the MDA5-mediated IFN-β activation by targeting interferon regulatory factor 7 (IRF7). Further studies demonstrated that σA interacts with IRF7, thereby blocking IRF7 dimerization and nuclear translocation, finally leading to the inhibition of IFN-β production. These findings reveal a novel mechanism that allows ARV to evade host antiviral immunity. IMPORTANCE ARV, the causative agent of viral arthritis or tenosynovitis in chickens, has a significant economic impact as it results in poor weight gain and increased feed conversion ratios. The MDA5-mediated IFN-β signal pathway plays an important role in host antiviral defense. Therefore, RNA viruses have developed mechanisms to counter this signaling pathway and successfully establish infection. However, the strategies adopted by ARV to block MDA5-IRF7 signaling remain unclear. In the current study, we demonstrated that ARV σA inhibits this pathway by binding to IRF7, which blocked IRF7 dimerization and nuclear translocation. Our findings may provide insights into how avian reovirus counteracts the innate antiviral immunity of the host to ensure viral replication.

Interferon regulatory factor (IRF) 3 and IRF7 are master regulators of type I interferon (IFN-I)-dependent antiviral innate immunity. Upon viral infection, a positive feedback loop is formed, wherein IRF7 promotes further induction of IFN-I in the later stage. Thus, it is critical to maintain a suitably low level of IRF7 to avoid the hyperproduction of IFN-I. In this study, we find that early expression of IFN-I-dependent STAT1 promotes the expression of XAF1 and that XAF1 is associated specifically with IRF7 and inhibits the activity of XIAP. XAF1-knockout and XIAP-transgenic mice display resistance to viral infection, and this resistance is accompanied by increases in IFN-I production and IRF7 stability. Mechanistically, we find that the XAF1-XIAP axis controls the activity of KLHL22, an adaptor of the BTB-CUL3-RBX1 E3 ligase complex through a ubiquitin-dependent pathway. CUL3-KLHL22 directly targets IRF7 and catalyzes its K48-linked ubiquitination and proteasomal degradation. These findings reveal unexpected functions of the XAF1-XIAP axis and KLHL22 in the regulation of IRF7 stability and highlight an important target for antiviral innate immunity., (© 2022 The Authors.)

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway plays a vital role in sensing viral DNA in the cytosol, stimulating type I interferon (IFN) production and triggering the innate immune response against DNA virus infection. However, viruses have evolved effective inhibitors to impede this sensing pathway. Chicken anemia virus (CAV), a nonenveloped ssDNA virus, is a ubiquitous pathogen causing great economic losses to the poultry industry globally. CAV infection is reported to downregulate type I IFN induction. However, whether the cGAS-STING signal axis is used by CAV to regulate type I IFN remains unclear. Our results demonstrate that CAV infection significantly elevates the expression of cGAS and STING at the mRNA level, whereas IFN-β levels are reduced. Furthermore, IFN-β activation was completely blocked by the structural protein VP1 of CAV in interferon stimulatory DNA (ISD) or STING-stimulated cells. VP1 was further confirmed as an inhibitor by interacting with interferon regulatory factor 7 (IRF7) by binding its C-terminal 143-492 aa region. IRF7 dimerization induced by TANK binding kinase 1 (TBK1) could be inhibited by VP1 in a dose-dependent manner. Together, our study demonstrates that CAV VP1 is an effective inhibitor that interacts with IRF7 and antagonizes cGAS-STING pathway-mediated IFN-β activation. These findings reveal a new mechanism of immune evasion by CAV., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Cyclic GMP-AMP synthase (cGAS), a key DNA sensor, detects cytosolic viral DNA and activates the adaptor protein stimulator of interferon genes (STING) to initiate interferon (IFN) production and host innate antiviral responses. Duck enteritis virus (DEV) is a duck alphaherpesvirus that causes an acute and contagious disease with high mortality in waterfowl. In the present study, we found that DEV inhibits host innate immune responses during the late phase of viral infection. Furthermore, we screened DEV proteins for their ability to inhibit the cGAS-STING DNA-sensing pathway and identified multiple viral proteins, including UL41, US3, UL28, UL53, and UL24, which block IFN-β activation through this pathway. The DEV tegument protein UL41, which exhibited the strongest inhibitory effect, selectively downregulated the expression of interferon regulatory factor 7 (IRF7) by reducing its mRNA accumulation, thereby inhibiting the DNA-sensing pathway. Ectopic expression of UL41 markedly reduced viral DNA-triggered IFN-β production and promoted viral replication, whereas deficiency of UL41 in the context of DEV infection increased the IFN-β response to DEV and suppressed viral replication. In addition, ectopic expression of IRF7 inhibited the replication of the UL41-deficient virus, whereas IRF7 knockdown facilitated its replication. This study is the first report identifying multiple viral proteins encoded by a duck DNA virus, which inhibit the cGAS-STING DNA-sensing pathway. These findings expand our knowledge of DNA sensing in ducks and reveal a mechanism through which DEV antagonizes the host innate immune response. IMPORTANCE Duck enteritis virus (DEV) is a duck alphaherpesvirus that causes an acute and contagious disease with high mortality, resulting in substantial economic losses in the commercial waterfowl industry. The evasion of DNA-sensing pathway-mediated antiviral innate immunity is essential for the persistent infection and replication of many DNA viruses. However, the mechanisms used by DEV to modulate the DNA-sensing pathway remain poorly understood. In the present study, we found that DEV encodes multiple viral proteins to inhibit the cGAS-STING DNA-sensing pathway. The DEV tegument protein UL41 selectively diminished the accumulation of interferon regulatory factor 7 (IRF7) mRNA, thereby inhibiting the DNA-sensing pathway. Loss of UL41 potently enhanced the IFN-β response to DEV and impaired viral replication in ducks. These findings provide insights into the host-virus interaction during DEV infection and help develop new live attenuated vaccines against DEV.

Influenza A virus (IAV) is a globally distributed zoonotic pathogen and causes a highly infectious respiratory disease with high morbidity and mortality in humans and animals. IAV has evolved various strategies to counteract the innate immune response, using different viral proteins. However, the mechanisms are not fully elucidated. In this study, we demonstrated that the nonstructural protein 2 (NS2) of H1N1 IAV negatively regulate the induction of type-I interferon. Co-immunoprecipitation experiments revealed that NS2 specifically interacts with interferon regulatory factor 7 (IRF7). NS2 blocks the nuclear translocation of IRF7 by inhibiting the formation of IRF7 dimers, thereby prevents the activation of IRF7 and inhibits the production of interferon-beta. Taken together, these findings revealed a novel mechanism by which the NS2 of H1N1 IAV inhibits IRF7-mediated type-I interferon production.

Tuberculosis (TB) induced by Mycobacterium tuberculosis (M. tuberculosis) infection remains a global most deadly infectious disease. While development of more effective TB vaccines and therapeutics relies on identifications of true biomarkers designating an immune protection against M. tuberculosis infection, exact protective immune components against M. tuberculosis infection remain largely unidentified. We previously found that severe TB induced remarkable up-regulation of interferon regulatory factor 7 (IRF7) and IRF7-related gene signatures, implicating that some unknown downstream molecules in IRF7 signaling cascades may determine the M. tuberculosis infection outcomes and serve as a protective immune component against M. tuberculosis infection. Indeed, here, we observe that genetic ablation of IRF7 leads to more severe lung pathology, increased M. tuberculosis burdens, impaired differentiation of effector/memory T subsets, and extensively elevated expression of pro-inflammatory cytokines in lungs. Importantly, IRF7 is vital for sustaining expression of PD-1/PD-L1 and PD-1/PD-L1-modulated miRNA-31. Moreover, interventions of miRNA-31 expressions via administration of miRNA-31 agomir reduces lung pathology and bacilli burdens via inducing up-regulation of gene sets involved in biological processes of defense response or cellular and chemical homeostasis in lungs. Thus, this study uncovers previously unrecognized importance and mechanisms of IRF7-mediated miRNA-31 as a protective immune component against M. tuberculosis infection., (Copyright © 2022 The Authors. Published by Elsevier GmbH.. All rights reserved.)

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.

Interferon regulatory factor 7 (IRF7), as the interferon-stimulated gene, maximally drives type I interferon (IFN) production. However, the mechanisms by which the biological function of IRF7 is regulated remain elusive. In this study, we found that IRF7 selectively interacted with the neuralized E3 ubiquitin-protein ligase 3 (NEURL3). In concomitant with IRF7 induction, NEURL3 is upregulated by NF-κB signaling in the late phase of viral infection. Moreover, NEURL3 augmented the host antiviral immune response through ubiquitinating IRF7. A mechanistic study revealed that NEURL3 triggered K63-linked poly-ubiquitination on IRF7 lysine 375, which in turn epigenetically enhanced the transcription of interferon-stimulated genes (ISGs) through disruption of the association of IRF7 with Histone Deacetylase 1 (HDAC1), consequently augmenting host antiviral immune response. Accordingly, Neurl3 -/- mice produced less type I IFNs and exhibited increased susceptibility to viral infection. Taken together, our findings identify NEURL3 as an E3 ubiquitin ligase of IRF7 and shed new light on the positive regulation of IRF7 in host antiviral immune signaling., (© 2022 The Authors. The FASEB Journal published by Wiley Periodicals LLC on behalf of Federation of American Societies for Experimental Biology.)

Innate antiviral immunity deteriorates with aging but how this occurs is not entirely clear. Here we identified SIRT1-mediated DNA-binding domain (DBD) deacetylation as a critical step for IRF3/7 activation that is inhibited during aging. Viral-stimulated IRF3 underwent liquid-liquid phase separation (LLPS) with interferon (IFN)-stimulated response element DNA and compartmentalized IRF7 in the nucleus, thereby stimulating type I IFN (IFN-I) expression. SIRT1 deficiency resulted in IRF3/IRF7 hyperacetylation in the DBD, which inhibited LLPS and innate immunity, resulting in increased viral load and mortality in mice. By developing a genetic code expansion orthogonal system, we demonstrated the presence of an acetyl moiety at specific IRF3/IRF7 DBD site/s abolish IRF3/IRF7 LLPS and IFN-I induction. SIRT1 agonists rescued SIRT1 activity in aged mice, restored IFN signaling and thus antagonized viral replication. These findings not only identify a mechanism by which SIRT1 regulates IFN production by affecting IRF3/IRF7 LLPS, but also provide information on the drivers of innate immunosenescence., (© 2022. The Author(s), under exclusive licence to Springer Nature America, Inc.)

Interferon regulatory factor (IRF) 3 and IRF7 are the most important nuclear transcription factors regulating type-I interferon (IFN) production in mammals and the IRF3 is missing in birds. Our previous study found that IFR7 is the most important IRF in chickens, however, its functions in geese remain unknown. We cloned goose IRF7 (GoIRF7) and conducted bioinformatics analyses to compare the chromosomal location and protein homology of IRF7 in different species. Overexpression of GoIRF7 in DF-1 cells induced the activation of IFN-β, and this activation correlated positively with the dosage of transfected plasmids. Overexpression of GoIRF7 in goose embryonic fibroblasts (GEFs) induced the expression of IFNs, proinflammatory cytokines, and IFN-stimulated genes (ISGs); it also inhibited replication of Newcastle disease virus (NDV) and vesicular stomatitis virus (VSV). Our results suggest that GoIRF7 is an important regulator of IFNs, proinflammatory cytokines, and ISGs and plays a role in antiviral innate immunity in geese., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Type 1 diabetes (T1D) is a T cell-mediated autoimmune disease. Increased incidence of T1D was reported in patients receiving IFN-α treatment. However, the exact mechanisms of IFN-α that facilitate the pathogenesis of T1D are not fully understood. To explore the mechanism of IFN-α on the immune system and islets, non-obese diabetic (NOD) mice were injected with IFN-α and the progression of autoimmune insulitis was assessed by haematoxylin and eosin (HE) staining, immunohistochemical and flow cytometry analysis. Transcriptional profiling of islets treated with IFN-α was explored by RNA-seq. IFN-α induced antigen presentation was evaluated by qRT-PCR, western blot and immunofluorescence, and key transcription factors were inhibited by small interfering RNAs (siRNAs). Our data show that IFN-α contributed to the progression of autoimmune insulitis in NOD mice by promoting the proliferation of CD8+ T cells. IFN-α upregulated antigen presentation related genes MHC I, TAP1, B2M, PSMB8, NLRC5 and transcriptional regulator STAT1, STAT2, IRF7 at a time and dose-dependent manner. The silence of STAT1 or STAT2 both weakened IFN-α-induced increase of antigen presenting related molecules. IRF7 was also merely influenced by STAT1 silence. The knockdown of IRF7 decreased the IFN-α induced expressions of TAP1, PSMB8 and MHC I and prevented the expression of STAT2 but not STAT1. Our study demonstrated that STAT1-IRF7-MHC I complex axis were crucial for IFN-α signalling in islets, and created positive feedback through IRF7-STAT2 cascade amplifying signals which accelerated the process of T1D., (© 2022 John Wiley & Sons Ltd.)

Interferon regulatory factor 7 (IRF7) is widely studied in inflammatory models. Its effects on malignant progression have been documented mainly from the perspective of the microenvironment. However, its role in leukemia has not been established. Here we used MLL-AF9-induced acute myeloid leukemia (AML) mouse models with IRF7 knockout or overexpression and xenograft mouse models to explore the intrinsic effects of IRF7 in AML. AML-IRF7 -/- mice exhibited accelerated disease progression with intracerebral invasion of AML cells. AML-IRF7 -/- cells showed increased proliferation and elevated leukemia stem cell (LSC) levels. Overexpression of IRF7 in AML cells decreased cell proliferation and LSC levels. Furthermore, overexpression of transforming growth-interacting factor 1 (TGIF1) rescued the enhanced proliferation and high LSC levels caused by IRF7 deficiency. Moreover, upregulation of vascular cell adhesion molecule 1 (VCAM1), which correlated with high LSC levels, was detected in AML-IRF7 -/- cells. In addition, blocking VCAM1-very late antigen 4 (VLA-4) axis delayed disease progression and attenuated intracerebral invasion of AML cells. Therefore, our findings uncover the intrinsic effects of IRF7 in AML and provide a potential strategy to control central nervous system myeloid leukemia., (© 2022. The Author(s).)

The small HERC family currently comprises four members (HERC3-6) involved in the regulation of various physiological activities. Little is known about the role of HERCs in IFN response. In this study, we identify a novel fish HERC member, named crucian carp HERC7, as a negative regulator of fish IFN response. Genome-wide search of homologs and comprehensive phylogenetic analyses reveal that the small HERC family, apart from HERC3-6 that have been well-characterized in mammals, contains a novel HERC7 subfamily exclusively in nonmammalian vertebrates. Lineage-specific and even species-specific expansion of HERC7 subfamily in fish indicates that crucian carp HERC7 might be species-specific. In virally infected fish cells, HERC7 is induced by IFN and selectively targets three retinoic acid-inducible gene-I-like receptor signaling factors for degradation to attenuate IFN response by two distinct strategies. Mechanistically, HERC7 delivers mediator of IFN regulatory factor 3 activator and mitochondrial antiviral signaling protein for proteasome-dependent degradation at the protein level and facilitates IFN regulatory factor 7 transcript decay at the mRNA level, thus abrogating cellular IFN induction to promote virus replication. Whereas HERC7 is a putative E3 ligase, the E3 ligase activity is not required for its negative regulatory function. These results demonstrate that the ongoing expansion of the small HERC family generates a novel HERC7 to fine-tune fish IFN antiviral response., (Copyright © 2022 by The American Association of Immunologists, Inc.)

N6-methyladenosine (m6A) is an abundant mRNA modification and affects many biological processes. However, how m6A levels are regulated during physiological or pathological processes such as virus infections, and the in vivo function of m6A in the intestinal immune defense against virus infections are largely unknown. Here, we uncover a novel antiviral function of m6A modification during rotavirus (RV) infection in small bowel intestinal epithelial cells (IECs). We found that rotavirus infection induced global m6A modifications on mRNA transcripts by down-regulating the m6a eraser ALKBH5. Mice lacking the m6A writer enzymes METTL3 in IECs ( Mettl3 ΔIEC) were resistant to RV infection and showed increased expression of interferons (IFNs) and IFN-stimulated genes (ISGs). Using RNA-sequencing and m6A RNA immuno-precipitation (RIP)-sequencing, we identified IRF7, a master regulator of IFN responses, as one of the primary m6A targets during virus infection. In the absence of METTL3, IECs showed increased Irf7 mRNA stability and enhanced type I and III IFN expression. Deficiency in IRF7 attenuated the elevated expression of IFNs and ISGs and restored susceptibility to RV infection in Mettl3 ΔIEC mice. Moreover, the global m6A modification on mRNA transcripts declined with age in mice, with a significant drop from 2 weeks to 3 weeks post birth, which likely has broad implications for the development of intestinal immune system against enteric viruses early in life. Collectively, we demonstrated a novel host m6A-IRF7-IFN antiviral signaling cascade that restricts rotavirus infection in vivo., Competing Interests: AW, WT, JT, JG, JW, GH, CQ, GZ, RL, DW, XR, KZ, SD, RF, HL, WP, SZ No competing interests declared, (© 2022, Wang et al.)

Interferon regulatory factor-7 (IRF7) is an essential regulator of both innate and adaptive immunity. It is also expressed in the otic vesicle of zebrafish embryos. However, any role for irf7 in hair cell development was uncharacterized. Does it work as a potential deaf gene to regulate hair cell development? We used whole-mount in situ hybridization (WISH) assay and morpholino-mediated gene knockdown method to investigate the role of irf7 in the development of otic vesicle hair cells during zebrafish embryogenesis. We performed RNA sequencing to gain a detailed insight into the molecules/genes which are altered upon downregulation of irf7. Compared to the wild-type siblings, knockdown of irf7 resulted in severe developmental retardation in zebrafish embryos as well as loss of neuromasts and damage to hair cells at an early stage (within 3 days post fertilization). Coinjection of zebrafish irf7 mRNA could partially rescued the defects of the morphants. atp1b2b mRNA injection can also partially rescue the phenotype induced by irf7 gene deficiency. Loss of hair cells in irf7-morphants does not result from cell apoptosis. Gene expression profiles show that, compared to wild-type, knockdown of irf7 can lead to 2053 and 2678 genes being upregulated and downregulated, respectively. Among them, 18 genes were annotated to hair cell (HC) development or posterior lateral line (PLL) development. All results suggest that irf7 plays an essential role in hair cell development in zebrafish, indicating that irf7 may be a member of deafness gene family., (© 2021 The Authors. Developmental Neurobiology published by Wiley Periodicals LLC.)

Infection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), causing the rapid spread of coronavirus disease 2019 (COVID-19), has generated a public health crisis worldwide. The molecular mechanisms of SARS-CoV-2 infection and virus-host interactions are still unclear. In this study, we identified four unique microRNA-like small RNAs encoded by SARS-CoV-2. SCV2-miR-ORF1ab-1-3p and SCV2-miR-ORF1ab-2-5p play an important role in evasion of type I interferon response through targeting several genes in type I interferon signaling pathway. Particularly worth mentioning is that highly expressed SCV2-miR-ORF1ab-2-5p inhibits some key genes in the host innate immune response, such as IRF7, IRF9, STAT2, OAS1, and OAS2. SCV2-miR-ORF1ab-2-5p has also been found to mediate allelic differential expression of COVID-19-susceptible gene OAS1. In conclusion, these results suggest that SARS-CoV-2 uses its miRNAs to evade the type I interferon response and links the functional viral sequence to the susceptible genetic background of the host., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Zhu, Zhang, Song, Qian, Gu, Yang, Shen, Xue and Tang.)

Poliomyelitis-like illness is a common clinical manifestation of neurotropic viral infections. Functional loss and death of motor neurons often lead to reduced muscle tone and paralysis, causing persistent motor sequelae among disease survivors. Despite several reports demonstrating the molecular basis of encephalopathy, the pathogenesis behind virus-induced flaccid paralysis remained largely unknown. The present study for the first time aims to elucidate the mechanism responsible for limb paralysis by studying clinical isolates of Japanese encephalitis virus (JEV) and Chandipura virus (CHPV) responsible for causing acute flaccid paralysis (AFP) in vast regions of Southeast Asia and the Indian subcontinent. An experimental model for studying virus-induced AFP was generated by intraperitoneal injection of 10-day-old BALB/c mice. Progressive decline in motor performance of infected animals was observed, with paralysis being correlated with death of motor neurons (MNs). Furthermore, we demonstrated that upon infection, MNs undergo an extrinsic apoptotic pathway in a RIG-I-dependent fashion via transcription factors pIRF-3 and pIRF-7. Both gene-silencing experiments using specific RIG-I-short interfering RNA and in vivo morpholino abrogated cellular apoptosis, validating the important role of pattern recognition receptor (PRR) RIG-I in MN death. Hence, from our experimental observations, we hypothesize that host innate response plays a significant role in deterioration of motor functioning upon neurotropic virus infections. IMPORTANCE Neurotropic viral infections are an increasingly common cause of immediate or delayed neuropsychiatric sequelae, cognitive impairment, and movement disorders or, in severe cases, death. Given the highest reported disability-adjusted life years and mortality rate worldwide, a better understanding of molecular mechanisms for underlying clinical manifestations like AFP will help in development of more effective tools for therapeutic solutions.

To investigate the antiviral effect of lithium chloride (LiCl) on the replication of Marek's disease virus (MDV) in chicken embryonic fibroblast (CEF) cells, real-time PCR, Western blotting, plaque counting, and indirect immunofluorescence experiments were performed at different time points of LiCl treated CEF cells with virus infection. The results demonstrated that LiCl could affect multiple steps of virus replication and inhibit viral gene expression and protein synthesis in a dose- and time-dependent manner. Moreover, LiCl could directly affect viral infectivity as well. In addition, LiCl significantly affected the gene expression of IFN-β related genes in virus-infected cells. These results indicate that LiCl significantly inhibits MDV replication and proliferation in CEF cells and it has the potential to be used as an antiviral agent against MDV.