ISG15 driven cellular responses to virus infection

Chronic sleep deprivation promotes experimental autoimmune uveitis through STAT1 phosphorylation, ISG15 expression and enhanced pathogenicity of macrophages

Chronic sleep deprivation (CSD) is increasingly common in modern society and is linked to various diseases, including autoimmune conditions like experimental autoimmune uveitis (EAU), a severe ocular inflammation. The pathogenesis of EAU remains unclear, but poor sleep quality has been shown to exacerbate inflammation through immune modulation. To explore this relationship, we conducted a clinical study at the Ophthalmology Center of Renmin Hospital of Wuhan University (July 2023-July 2024), assessing sleep quality in uveitis patients using the Pittsburgh Sleep Quality Index (PSQI). Based on PSQI scores, patients were categorized into four groups, and their symptoms and characteristics were recorded. Simultaneously, a B10.RIII mouse model of CSD and EAU was developed. Western blotting assessed the phosphorylation of Signal Transducer and Activator of Transcription 1 (STAT1) and the expression of Interferon-Stimulated Gene 15 (ISG15) expression, while immunofluorescence and western blotting evaluated macrophage activity and cytokine secretion. Clinical results showed a strong correlation between poor sleep quality and worsened inflammatory symptoms. In mice, CSD increased STAT1 phosphorylation and ISG15 expression, enhancing macrophage activity and worsening ocular inflammation. Our findings suggest that CSD exacerbates EAU through STAT1 phosphorylation, ISG15 expression, and macrophage activation. The clinical data further support this mechanism, indicating that improving sleep quality could reduce the risk of autoimmune diseases and offering new insights into the connection between sleep and immune function.

Design of inhibitors of SARS-CoV-2 papain-like protease deriving from GRL0617: Structure-activity relationships

The unique and complex structure of papain-like protease (PLpro) of the SARS-CoV-2 virus represents a difficult challenge for antiviral development, yet it offers a compelling validated target for effective therapy of COVID-19. The surge in scientific interest in inhibiting this cysteine protease emerged after its demonstrated connection to the cytokine storm in patients with COVID-19 disease. Furthermore, the development of new inhibitors against PLpro may also be beneficial for the treatment of respiratory infections caused by emerging coronavirus variants of concern. This review article provides a comprehensive overview of PLpro inhibitors, focusing on the structural framework of the known inhibitor GRL0617 and its analogs. We categorize PLpro inhibitors on the basis of their structures and binding site: Glu167 containing site, BL2 groove, Val70Ub site, and Cys111 containing catalytic site. We summarize and evaluate the majority of GRL0617-like inhibitors synthesized so far, highlighting their published biochemical parameters, which reflect their efficacy. Published research has shown that strategic modifications to GRL0617, such as decorating the naphthalene ring, extending the aromatic amino group or the orthomethyl group, can substantially decrease the IC50 from micromolar up to nanomolar concentration range. Some advantageous modifications significantly enhance inhibitory activity, paving the way for the development of new potent compounds. Our review places special emphasis on structures that involve direct modifications to the GRL0617 scaffold, including piperidine carboxamides and modified benzylmethylnaphthylethanamines (Jun9 scaffold). All these compounds are believed to inhibit the proteolytic, deubiquitination, and deISGylation activity of PLpro, biochemical processes linked to the severe progression of COVID-19. Finally, we summarize the development efforts for SARS-CoV-2 PLpro inhibitors, in detailed structure-activity relationships diagrams. This aims to inform and inspire future research in the search for potent antiviral agents against PLpro of current and emerging coronavirus threats.

Characterization of interferon-stimulated gene 15 from Bostrychus sinensis: Cloning, expression and functional analyses

In this study, the interferon-stimulated gene 15 (referred to as BsISG15) was sequenced and characterized in Bostrychus sinensis. BsISG15 encodes a 155-amino-acid protein weighing ∼17 kDa, featuring two conserved ubiquitin-like domains and an LRGG conjugation motif at the C-terminal. The real-time PCR assays revealed constitutive expression of the BsISG15 gene in all examined organs of healthy B. sinensis, with the peripheral blood showing the highest level of expression. The expression levels of the BsISG15 gene in the head kidney, liver, spleen, and peripheral blood of B. sinensis were significantly altered by both poly (I:C) stimulation and Vibrio parahaemolyticus infection. Western blot analyses showed that the expression of the BsISG15 protein was induced in both the liver and spleen of B. sinensis infected with either poly (I:C) or bacteria, with a concomitant increase in the levels of protein ISGylation, particularly evident in the bacterial-infected liver tissues. Besides, Western blot analyses have demonstrated that head kidney lymphocytes of B. sinensis are capable of secreting the free BsISG15 protein. The recombinant BsISG15 protein significantly increased the production of reactive oxygen species, synthesis of NO, and phagocytosis in macrophages from B. sinensis and also upregulated the expression of proinflammatory cytokine genes (IFNg, IL-1β, IL-6, and IL-8) in these cells. Knockdown of endogenous BsISG15 elevated the expression levels of proinflammatory cytokines IL-1β, IL-6, and IL-8, suggesting a negative regulation of BsISG15 on the inflammatory response in macrophages. The results indicate that BsISG15 plays a significant role in the innate antiviral and antibacterial immunity of B. sinensis.

Protumorigenic Interferon-Stimulated Genes in Cancer: A Comprehensive Review

Interferon-stimulated genes (ISGs), whose production is triggered by interferons, are known to defend the host from pathogenic and cancer-specific antigens, one of which is by inducing apoptosis in infected or mutated cells. It has been reported recently that specific ISGs aid cancer cells in evading immunosurveillance and inflammatory cells by inhibiting the apoptosis process. This report reviewed four apoptosis-regulating ISG proteins: interferon-stimulated gene 15 (ISG15), interferon alpha-inducible protein 27 (IFI27), interferon alpha-inducible protein 6 (IFI6), and radical S-adenosyl methionine domain containing 2 (RSAD2), demonstrating anti-apoptosis function, and considered them protumorigenic.

Antiviral activity of adenoviral vector expressing human interferon lambda-4 against influenza virus

Interferon lambda (IFNλ), classified as a type III IFN, is a representative cytokine that plays an important role in innate immunity along with type I IFN. IFNλ can elicit antiviral states by inducing peculiar sets of IFN-stimulated genes (ISGs). In this study, an adenoviral vector expression system with a tetracycline operator system was used to express human IFNλ4 in cells and mice. The formation of recombinant adenovirus (rAd-huIFNλ4) was confirmed using immunohistochemistry assays and transmission electron microscopy. Its purity was verified by quantifying host cell DNA and host cell proteins, as well as by confirming the absence of the replication-competent adenovirus. The transduction of rAd-huIFNλ4 induced ISGs and inhibited four subtypes of the influenza virus in both mouse-derived (LA-4) and human-derived cells (A549). The antiviral state was confirmed in BALB/c mice following intranasal inoculation with 109 PFU of rAd-huIFNλ4, which led to the inhibition of four subtypes of the influenza virus in mouse lungs, with reduced inflammatory lesions. These results imply that human IFNλ4 could induce antiviral status by modulating ISG expression in mice.

Deubiquitinating activity of SARS-CoV-2 papain-like protease does not influence virus replication or innate immune responses in vivo

The coronavirus papain-like protease (PLpro) is crucial for viral replicase polyprotein processing. Additionally, PLpro can subvert host defense mechanisms by its deubiquitinating (DUB) and deISGylating activities. To elucidate the role of these activities during SARS-CoV-2 infection, we introduced mutations that disrupt binding of PLpro to ubiquitin or ISG15. We identified several mutations that strongly reduced DUB activity of PLpro, without affecting viral polyprotein processing. In contrast, mutations that abrogated deISGylating activity also hampered viral polyprotein processing and when introduced into the virus these mutants were not viable. SARS-CoV-2 mutants exhibiting reduced DUB activity elicited a stronger interferon response in human lung cells. In a mouse model of severe disease, disruption of PLpro DUB activity did not affect lethality, virus replication, or innate immune responses in the lungs. This suggests that the DUB activity of SARS-CoV-2 PLpro is dispensable for virus replication and does not affect innate immune responses in vivo. Interestingly, the DUB mutant of SARS-CoV replicated to slightly lower titers in mice and elicited a diminished immune response early in infection, although lethality was unaffected. We previously showed that a MERS-CoV mutant deficient in DUB and deISGylating activity was strongly attenuated in mice. Here, we demonstrate that the role of PLpro DUB activity during infection can vary considerably between highly pathogenic coronaviruses. Therefore, careful considerations should be taken when developing pan-coronavirus antiviral strategies targeting PLpro.

Antiviral responses versus virus-induced cellular shutoff: a game of thrones between influenza A virus NS1 and SARS-CoV-2 Nsp1

Following virus recognition of host cell receptors and viral particle/genome internalization, viruses replicate in the host via hijacking essential host cell machinery components to evade the provoked antiviral innate immunity against the invading pathogen. Respiratory viral infections are usually acute with the ability to activate pattern recognition receptors (PRRs) in/on host cells, resulting in the production and release of interferons (IFNs), proinflammatory cytokines, chemokines, and IFN-stimulated genes (ISGs) to reduce virus fitness and mitigate infection. Nevertheless, the game between viruses and the host is a complicated and dynamic process, in which they restrict each other via specific factors to maintain their own advantages and win this game. The primary role of the non-structural protein 1 (NS1 and Nsp1) of influenza A viruses (IAV) and the pandemic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), respectively, is to control antiviral host-induced innate immune responses. This review provides a comprehensive overview of the genesis, spatial structure, viral and cellular interactors, and the mechanisms underlying the unique biological functions of IAV NS1 and SARS-CoV-2 Nsp1 in infected host cells. We also highlight the role of both non-structural proteins in modulating viral replication and pathogenicity. Eventually, and because of their important role during viral infection, we also describe their promising potential as targets for antiviral therapy and the development of live attenuated vaccines (LAV). Conclusively, both IAV NS1 and SARS-CoV-2 Nsp1 play an important role in virus-host interactions, viral replication, and pathogenesis, and pave the way to develop novel prophylactic and/or therapeutic interventions for the treatment of these important human respiratory viral pathogens.

Discovering common pathogenetic processes between COVID-19 and tuberculosis by bioinformatics and system biology approach

Introduction

The coronavirus disease 2019 (COVID-19) pandemic, stemming from the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has persistently threatened the global health system. Meanwhile, tuberculosis (TB) caused by Mycobacterium tuberculosis (M. tuberculosis) still continues to be endemic in various regions of the world. There is a certain degree of similarity between the clinical features of COVID-19 and TB, but the underlying common pathogenetic processes between COVID-19 and TB are not well understood.

Methods

To elucidate the common pathogenetic processes between COVID-19 and TB, we implemented bioinformatics and systematic research to obtain shared pathways and molecular biomarkers. Here, the RNA-seq datasets (GSE196822 and GSE126614) are used to extract shared differentially expressed genes (DEGs) of COVID-19 and TB. The common DEGs were used to identify common pathways, hub genes, transcriptional regulatory networks, and potential drugs.

Results

A total of 96 common DEGs were selected for subsequent analyses. Functional enrichment analyses showed that viral genome replication and immune-related pathways collectively contributed to the development and progression of TB and COVID-19. Based on the protein-protein interaction (PPI) network analysis, we identified 10 hub genes, including IFI44L, ISG15, MX1, IFI44, OASL, RSAD2, GBP1, OAS1, IFI6, and HERC5. Subsequently, the transcription factor (TF)-gene interaction and microRNA (miRNA)-gene coregulatory network identified 61 TFs and 29 miRNAs. Notably, we identified 10 potential drugs to treat TB and COVID-19, namely suloctidil, prenylamine, acetohexamide, terfenadine, prochlorperazine, 3'-azido-3'-deoxythymidine, chlorophyllin, etoposide, clioquinol, and propofol.

Conclusion

This research provides novel strategies and valuable references for the treatment of tuberculosis and COVID-19.

Comparative transcriptome analysis of SARS-CoV-2, SARS-CoV, MERS-CoV, and HCoV-229E identifying potential IFN/ISGs targets for inhibiting virus replication

Introduction

Since its outbreak in December 2019, SARS-CoV-2 has spread rapidly across the world, posing significant threats and challenges to global public health. SARS-CoV-2, together with SARS-CoV and MERS-CoV, is a highly pathogenic coronavirus that contributes to fatal pneumonia. Understanding the similarities and differences at the transcriptome level between SARS-CoV-2, SARS-CoV, as well as MERS-CoV is critical for developing effective strategies against these viruses.

Methods

In this article, we comparatively analyzed publicly available transcriptome data of human cell lines infected with highly pathogenic SARS-CoV-2, SARS-CoV, MERS-CoV, and lowly pathogenic HCoV-229E. The host gene expression profiles during human coronavirus (HCoV) infections were generated, and the pathways and biological functions involved in immune responses, antiviral efficacy, and organ damage were intensively elucidated.

Results

Our results indicated that SARS-CoV-2 induced a stronger immune response versus the other two highly pathogenic HCoVs. Specifically, SARS-CoV-2 induced robust type I and type III IFN responses, marked by higher upregulation of type I and type III IFNs, as well as numerous interferon-stimulated genes (ISGs). Further Ingenuity Pathway Analysis (IPA) revealed the important role of ISGs for impeding SARS-CoV-2 infection, and the interferon/ISGs could be potential targets for therapeutic interventions. Moreover, our results uncovered that SARS-CoV-2 infection was linked to an enhanced risk of multi-organ toxicity in contrast to the other two highly pathogenic HCoVs.

Discussion

These findings provided valuable insights into the pathogenic mechanism of SARS-CoV-2, which showed a similar pathological feature but a lower fatality rate compared to SARS-CoV and MERS-CoV.

Usp25-Erlin1/2 activity limits cholesterol flux to restrict virus infection

Reprogramming lipid metabolic pathways is a critical feature of activating immune responses to infection. However, how these reconfigurations occur is poorly understood. Our previous screen to identify cellular deubiquitylases (DUBs) activated during influenza virus infection revealed Usp25 as a prominent hit. Here, we show that Usp25-deleted human lung epithelial A549 cells display a >10-fold increase in pathogenic influenza virus production, which was rescued upon reconstitution with the wild type but not the catalytically deficient (C178S) variant. Proteomic analysis of Usp25 interactors revealed a strong association with Erlin1/2, which we confirmed as its substrate. Newly synthesized Erlin1/2 were degraded in Usp25-/- or Usp25C178S cells, activating Srebp2, with increased cholesterol flux and attenuated TLR3-dependent responses. Our study therefore defines the function of a deubiquitylase that serves to restrict a range of viruses by reprogramming lipid biosynthetic flux to install appropriate inflammatory responses.

Antiviral role of grouper FoxO1 against RGNNV and SGIV infection

As a key regulator of the innate immune system, FoxO1 has a variety of activities in biological organisms. In the present study, grouper FoxO1 (EcFoxO1) was cloned and the antiviral activity in red grouper neuron necrosis virus (RGNNV) and Singapore grouper iridescent virus (SGIV) was examined. The open reading frame (ORF) of EcFoxO1 contains 2,034 base pairs that encode a protein of 677 amino acids with a predicted molecular weight of 73.21 kDa. EcFoxO1 was shown to be broadly distributed in healthy grouper tissues, and was up-regulated in vitro in response to stimulation by RGNNV and SGIV. EcFoxO1 has a whole-cell distribution in grouper spleen (GS) cells. EcFoxO1 decreased the replication of RGNNV and SGIV, and activated interferon (IFN) 3, IFN-stimulated response element (ISRE), and nuclear factor-κB (NF-κB) promoter activities. EcFoxO1 could interact with EcIRF3. Together, the results demonstrated that EcFoxO1 might be an important regulator of grouper innate immune response against RGNNV and SGIV infection.

Crossroads in virology: current challenges and future perspectives in the age of emerging viruses

Ongoing global health challenges posed by emerging and re-emerging viruses have highlighted the critical importance of understanding virus-host interactions in countering these threats. Environmental changes, urbanisation and ecological disruption, coupled with the adaptable nature of viruses, facilitates the emergence and spread of new viruses. This Editorial emphasises the urgency of a concerted effort in understanding virus-host interactions to inform the development of therapeutics and vaccines, and help predict disease outcomes. Furthermore, efforts to monitor viral evolution, identify mutations of concern, and develop 'universal' vaccines and broad-spectrum antiviral drugs are needed to counter viral evolution and potentially prevent future viral emergences. Widespread public mistrust surrounding viruses and vaccines also calls for improvement in science communication. A 'One Health' approach that advocates the development of robust global health systems, interdisciplinary collaborations and equity in health access is therefore imperative for transforming the virology landscape.

Blood Transcriptomic Analyses Reveal Functional Pathways Associated with Thermotolerance in Pregnant Ewes Exposed to Environmental Heat Stress

Environmental heat stress triggers a series of compensatory mechanisms in sheep that are dependent on their genetic regulation of thermotolerance. Our objective was to identify genes and regulatory pathways associated with thermotolerance in ewes exposed to heat stress. We performed next-generation RNA sequencing on blood collected from 16 pregnant ewes, which were grouped as tolerant and non-tolerant to heat stress according to a physiological indicator. Additional samples were collected to measure complete blood count. A total of 358 differentially expressed genes were identified after applying selection criteria. Gene expression analysis detected 46 GO terms and 52 KEGG functional pathways. The top-three signaling pathways were p53, RIG-I-like receptor and FoxO, which suggested gene participation in biological processes such as apoptosis, cell signaling and immune response to external stressors. Network analysis revealed ATM, ISG15, IRF7, MDM4, DHX58 and TGFβR1 as over-expressed genes with high regulatory potential. A co-expression network involving the immune-related genes ISG15, IRF7 and DXH58 was detected in lymphocytes and monocytes, which was consistent with hematological findings. In conclusion, transcriptomic analysis revealed a non-viral immune mechanism involving apoptosis, which is induced by external stressors and appears to play an important role in the molecular regulation of heat stress tolerance in ewes.

Viral subversion of selective autophagy is critical for biogenesis of virus replication organelles

Infection by many (+)RNA viruses is accompanied by ER-expansion and membrane remodelling to form viral replication organelles, followed by assembly and secretion of viral progenies. We previously identified that virus-triggered lipophagy was critical for flaviviral assembly, and is driven by the lipid droplet associated protein Ancient ubiquitin protein 1 (Aup1). A ubiquitin conjugating protein Ube2g2 that functions as a co-factor for Aup1 was identified as a host dependency factor in our study. Here we characterized its function: Ube2g2-deficient cells displayed a dramatic reduction in virus production, which could be rescued by reconstituting the wild-type but not the catalytically deficient (C89K) mutant of Ube2g2, suggesting that its enzymatic activity is necessary. Ube2g2 deficiency did not affect entry of virus particles but resulted in a profound loss in formation of replication organelles, and production of infectious progenies. This phenomenon resulted from its dual activity in (i) triggering lipophagy in conjunction with Aup1, and (ii) degradation of ER chaperones such as Herpud1, SEL1L, Hrd1, along with Sec62 to restrict ER-phagy upon Xbp1-IRE1 triggered ER expansion. Our results therefore underscore an exquisite fine-tuning of selective autophagy by flaviviruses that drive host membrane reorganization during infection to enable biogenesis of viral replication organelles.

Dual domain recognition determines SARS-CoV-2 PLpro selectivity for human ISG15 and K48-linked di-ubiquitin

The Papain-like protease (PLpro) is a domain of a multi-functional, non-structural protein 3 of coronaviruses. PLpro cleaves viral polyproteins and posttranslational conjugates with poly-ubiquitin and protective ISG15, composed of two ubiquitin-like (UBL) domains. Across coronaviruses, PLpro showed divergent selectivity for recognition and cleavage of posttranslational conjugates despite sequence conservation. We show that SARS-CoV-2 PLpro binds human ISG15 and K48-linked di-ubiquitin (K48-Ub2) with nanomolar affinity and detect alternate weaker-binding modes. Crystal structures of untethered PLpro complexes with ISG15 and K48-Ub2 combined with solution NMR and cross-linking mass spectrometry revealed how the two domains of ISG15 or K48-Ub2 are differently utilized in interactions with PLpro. Analysis of protein interface energetics predicted differential binding stabilities of the two UBL/Ub domains that were validated experimentally. We emphasize how substrate recognition can be tuned to cleave specifically ISG15 or K48-Ub2 modifications while retaining capacity to cleave mono-Ub conjugates. These results highlight alternative druggable surfaces that would inhibit PLpro function.

The Wheel of p53 Helps to Drive the Immune System

The p53 tumor suppressor protein is best known as an inhibitor of the cell cycle and an inducer of apoptosis. Unexpectedly, these functions of p53 are not required for its tumor suppressive activity in animal models. High-throughput transcriptomic investigations as well as individual studies have demonstrated that p53 stimulates expression of many genes involved in immunity. Probably to interfere with its immunostimulatory role, many viruses code for proteins that inactivate p53. Judging by the activities of immunity-related p53-regulated genes it can be concluded that p53 is involved in detection of danger signals, inflammasome formation and activation, antigen presentation, activation of natural killer cells and other effectors of immunity, stimulation of interferon production, direct inhibition of virus replication, secretion of extracellular signaling molecules, production of antibacterial proteins, negative feedback loops in immunity-related signaling pathways, and immunologic tolerance. Many of these p53 functions have barely been studied and require further, more detailed investigations. Some of them appear to be cell-type specific. The results of transcriptomic studies have generated many new hypotheses on the mechanisms utilized by p53 to impact on the immune system. In the future, these mechanisms may be harnessed to fight cancer and infectious diseases.