Long noncoding RNA AANCR modulates innate antiviral responses by blocking miR-210-dependent MITA downregulation in teleost fish,Miichthys miiuy

Viral infection induces the initiation of antiviral effectors and cytokines which are critical mediators of innate antiviral responses.The critical molecular determinants are responsible for triggering an appropriate immune response.Long noncoding RNAs(lncRNAs)have emerged as new gene modulators involved in various biological processes,while how lncRNAs operate in lower vertebrates are still unknown.Here,we discover a long noncoding RNA,termed antiviral-associated long noncoding RNA(AANCR),as a novel regulator for innate antiviral responses in teleost fish.The results indicate that fish MITA plays an essential role in host antiviral responses and inhibition of Siniperca chuatsi rhabdovirus(SCRV)production.miR-210 reduces MITA expression and suppress MITA-mediated antiviral responses,which may help viruses evade host antiviral responses.Further,AANCR functions as a competing endogenous RNA(ceRNA)for miR-210 to control protein abundance of MITA,thereby inhibiting SCRV replication and promoting antiviral responses.Our data not only shed new light on understanding the function role of lncRNA in biological processes in teleost fish,but confirmed the hypothesis that ceRNA networks exist widely in vertebrates.

ISG60 Negatively Regulates Cell Antiviral Responses by Disrupting the VISA-Associated Complexes

Viral infection activates the transcription factors NF-KB and interferon regulatory factor 3 （IRF3）, which collaborate to induce type I interferons （IFNs） and initiate host innate antiviral response. IFN-stimulated gene 56 （ISG56） induced by type I IFNs is a negative regulator of cellular antiviral response. In this study, we identified ISG60 as an ISG56-associated protein by biochemical purification and mass spectrometry analysis. Overex- pression of ISG60 inhibited Sendai virus-induced activation of NF-KB and IRF3. Coimmunoprecipitation assays indicated that ISG60 interacted with MDA5 and VISA, two important signaling proteins participating in virus-triggered production of type I IFNs. Furthermore, ISG60 disrupted the interaction of VISA with MDA5 or RIG-I. These results indicate that ISG60 is a negative regulator of virus-triggered type I IFNs induction.

Toll-Like Receptor-Dependent Antiviral Responses at the Maternal-Fetal Interface

The maternal-fetal interface is a key barrier to protect the fetus from infection.Toll-like receptors (TLRs) at the maternal-fetal interface are involved in antiviral responses.TLRs are expressed in both maternal decidua and fetal trophoblasts.Virus-induced activation of TLR signaling pathways triggers the release of interferon-related antiviral molecules and other inflammatory cytokines and/or chemokines by the host innate immune system,which may disrupt immune tolerance at the maternal-fetal interface and lead to pregnancy complications.In this review,we summarize the state of knowledge on the most common viral infections during pregnancy,antiviral TLR responses at the maternal-fetal interface,and TLR-associated pregnancy complications.

Negative feedback regulation of cellular antiviral signaling by RBCKl-mediated degradation of IRF3

Viral infection causes host cells to produce type I interferons （IFNs）, which are critically involved in viral clearance. Previous studies have demonstrated that activation of the transcription factor interferon regulatory factor （IRF）3 is essential for virus-triggered induction of type I IFNs. Here we show that the E3 ubiquitin ligase RBCC protein interacting with PKC1 （RBCK1） catalyzes the ubiquitination and degradation of IRF3. Overexpression of RBCK1 negatively regulates Sendai virus-triggered induction of type I IFNs, while knockdown of RBCK1 has the opposite effect. Plaque assays consistently demonstrate that RBCKI negatively regulates the cellular antiviral response. Furthermore, viral infection leads to induction of RBCK1 and subsequent degradation of IRF3. These findings suggest that the cellular antiviral response is controlled by a negative feedback regulatory mechanism involving RBCKl-mediated ubiquitination and degradation of IRF3.

Long noncoding RNA negative regulator of antiviral response contributes to pancreatic ductal adenocarcinoma progression via targeting miR-299-3p

BACKGROUND Pancreatic ductal cancer(PDAC)has high malignancy and poor prognosis.Long noncoding RNAs(lncRNAs)are associated with high levels of malignancy,including PDAC.However,the biological and clinical significance of negative regulator of antiviral response(NRAV)in PDAC is unclear.AIM To study the regulatory role of lncRNA NRAV in PDAC.METHODS GEPIA analyzed lncRNA NRAV and miRNA(miR-299-3p)expression levels in PDAC tissues and measured them in PDAC cells by quantitative measurements in real time.The specific role of NRAV and miR-299-3p in cell proliferation and transfer potential was evaluated by cell formation analysis,Cell Counting Kit-8 and Transwell analysis.The relationship between NRAV and miR-299-3p was studied by predictive bioinformatics,RNA immunoassay,and fluorescence enzyme analysis.In vivo experiments included transplantation of simulated tumor cells under naked mice.RESULTS The expression level of lncRNA NRAV was higher in both tumor tissues and cell lines of PDAC and was negatively associated with the clinical survival of PDAC patients.Functionally,overexpression of NRAV promoted cell proliferation and metastasis of PDAC cells,while knockdown of NRAV reversed these effects.Finally,NRAV was performed as a molecular sponge of miR-299-3p.Moreover,overexpression of miR-299-3p could reverse the promoting effects of NRAV on cell proliferation and metastasis of PDAC cells.CONCLUSION NRAV facilitates progression of PDAC as a molecular sponge of miR-299-3p and may be a potential molecular marker for diagnosis and treatment of PDAC.

Alpha-fetoprotein screening in patients with hepatitis C-induced cirrhosis who achieved a sustained virologic response in the direct-acting antiviral agents era

To the Editor:Hepatocellular carcinoma (HCC) is the most common primary livertumorandthethirdcauseofcancer-relateddeathsworldwide. HCC is the consequence of malignant transformation of hepatocytes and mainly occurs in patients with cirrhosis. Hepatitis C virus (HCV) chronic infection is a leading cause of end-stage liver diseaseandHCCintheWesterncountries[1].Theapprovalof direct-acting antiviral agents (DAAs) for the treatment of HCV has revolutionized the management of the disease, as no absolute contraindication to treatment exists and sustained virological response

Harnessing immunity:Immunomodulatory therapies in COVID-19

An overly exuberant immune response,characterized by a cytokine storm and uncontrolled inflammation,has been identified as a significant driver of severe coronavirus disease 2019(COVID-19)cases.Consequently,deciphering the intricacies of immune dysregulation in COVID-19 is imperative to identify specific targets for intervention and modulation.With these delicate dynamics in mind,immunomodulatory therapies have emerged as a promising avenue for miti-gating the challenges posed by COVID-19.Precision in manipulating immune pathways presents an opportunity to alter the host response,optimizing antiviral defenses while curbing deleterious inflammation.This review article compre-hensively analyzes immunomodulatory interventions in managing COVID-19.We explore diverse approaches to mitigating the hyperactive immune response and its impact,from corticosteroids and non-steroidal drugs to targeted biologics,including anti-viral drugs,cytokine inhibitors,JAK inhibitors,convalescent plasma,monoclonal antibodies(mAbs)to severe acute respiratory syndrome coronavirus 2,cell-based therapies(i.e.,CAR T,etc.).By summarizing the current evidence,we aim to provide a clear roadmap for clinicians and researchers navigating the complex landscape of immunomodulation in COVID-19 treatment.CS Glucocorticoids are among the most widely prescribed drugs with their immune-suppressive and anti-inflammatory effect[84].The current guidelines for the treatment of COVID-19 recommend against the use of dexamethasone or other systemic CS in non-hospitalized patients in the absence of another indication[70].The RECOVERY trial demonstrates the reduced 28-d mortality among hospitalized patients with COVID-19 using dexamethasone compared to the usual standard of care,along with other investigators,such as Ahmed and Hassan[85].The benefit of dexamethasone was seen only among participants receiving either oxygen alone or invasive mechanical ventilation at randomization but not among those receiving no respiratory support at enrollment[85].In a systematic review and meta-analysis,Albuquerque et al[86]showed that in comparison to tocilizumab,baricitinib,and sarilumab are associated with high probabilities of similar mortality reductions among hospitalized COVID-19 concurrently treated with CS.As a result of the absence of SARS-CoV-2-specific antiviral medications,the effectiveness of COVID-19 treatments is reduced.Several COVID-19 therapies are now under investigation.However,the majority of them lack specificity,efficacy,and safety[87].Immunotherapy is a ground-breaking medical treatment that manipulates the immune system to fight diseases.Translational research is rapidly progressing,recognized as a significant breakthrough in 2013[88].Among the immunotherapeutic options for treating COVID-19 are Immunoglobulin,CP,antibodies,mAbs(mAbs),NK cells,T cells,TLR,cytokine therapies and immune modulators.

PTEN-L promotes type I interferon responses and antiviral immunity

Phosphatase and tensin homolog deleted on chromosome ten(PTEN)is a well-known tumor suppressor that acts as a dual-specificity phosphatase and is frequently mutated in human cancer.Our previous work has demonstrated that PTEN also plays a vital role in type I interferon responses and antiviral innate immunity.Recently,a translational variant of PTEN with a long N-terminal extension(PTEN-L)has been discovered that is secreted into the extracellular environment and enters recipient cells,where it exerts a phosphatase function antagonistic to PI3K/Akt signaling and tumorigenesis.In this study,we demonstrate that PTEN-L promotes type I interferon responses and antiviral innate immunity during viral infection in a phosphatase activity-dependent manner.Compared with canonical PTEN,PTEN-L also exerts its antiviral function when it is applied exogenously in protein form.This finding was confirmed in cell cultures and mouse infection models.Furthermore,PTEN-L enhances the responses of both type I interferon and proinflammatory cytokines,thus suggesting that PTEN-L might possess additional functions compared with those of PTEN.Thus,the antiviral function of PTEN-L may open an avenue for the use of PTEN-L in antiviral therapy,particularly in patients with PTEN-deficient tumors.

Toll-like receptor 3(TLR3)regulation mechanisms and roles in antiviral innate immune responses

Toll-like receptor 3(TLR3)is a member of the TLR family,mediating the transcriptional induction of type I interferons(IFNs),proinflammatory cytokines,and chemokines,thereby collectively establishing an antiviral host response.Studies have shown that unlike other TLR family members,TLR3 is the only RNA sensor that is utterly dependent on the Tollinterleukin-1 receptor(TIR)-domain-containing adaptor-inducing IFN-β(TRIF).However,the details of how the TLR3-TRIF signaling pathway works in an antiviral response and how it is regulated are unclear.In this review,we focus on recent advances in understanding the antiviral mechanism of the TRIF pathway and describe the essential characteristics of TLR3 and its antiviral effects.Advancing our understanding of TLR3 may contribute to disease diagnosis and could foster the development of novel treatments for viral diseases.

HIV reservoir: antiviral immune responses and immune interventions for curing HIV infection

Antiretroviral therapy against human immunodeficiency virus (HIV) is effective in controlling viral replication but cannot completely eliminate HIV due to the persistence of the HIV reservoir. Innate and adaptive immune responses have been proposed to contribute to preventing HIV acquisition, controlling HIV replication and eliminating HIV-infected cells. However, the immune responses naturally induced in HIV-infected individuals rarely eradicate HIV infection, which may be caused by immune escape, an inadequate magnitude and breadth of immune responses, and immune exhaustion. Optimizing these immune responses may solve the problems of epitope escape and insufficient sustained memory responses. Moreover, immune interventions aimed at improving host immune response can reduce HIV reservoirs, which have become one focus in the development of innovative strategies to eliminate HIV reservoirs. In this review, we focus on the immune response against HIV and how antiviral immune responses affect HIV reservoirs. We also discuss the development of innovative strategies aiming to eliminate HIV reservoirs and promoting functional cure of HIV infection.

SOCS3 acts as a potential negative regulator in the antiviral response of large yellow croaker(Larimichthys crocea)by interacting with STAT1

Suppressors of cytokine signaling(SOCS)proteins are important regulators of the Janus kinase-signal transducer and activator of transcription(JAK-STAT)pathway.Within the SOCS family,SOCS3 is one of the most potent inhibitors of cytokine signaling.However,there is limited knowledge regarding the function of SOCS3 on regulating type I interferon(IFN)signaling in fish.In this study,the complete open reading frame(ORF)of SOCS3 from the large yellow croaker(Larimichthys crocea,LcSOCS3)was cloned and characterized.The ORF of LcSOCS3 was 618 nucleotides in length and encoded a protein containing 205 amino acids.LcSOCS3 had the typical domain architecture of the SOCS family,including an SRC homology 2(SH2)domain,a SOCS box,an additional kinase inhibition region(KIR),and an extended SH2 subdomain(ESS).Phylogenetic analysis revealed that LcSOCS3 was clustered with other fish SOCS3s and most closely related to the SOCS3 of Collichthy lucidus.LcSOCS3 mRNA was detected in all organs or tissues examined,and its expression was significantly increased in both head kidney and spleen tissues,and primary head kidney leukocytes after poly(I:C)stimulation.Overexpression of LcSOCS3 significantly promoted Spring viremia of carp virus(SVCV)replication,resulting in a more severe cytopathic effect,increased viral titer,enhanced copy number of the SVCV-G gene,and decreased expression levels of IFN1,IRF7,ISG15,Viperin,PKR,and Mx in epithelioma papulosum cyprinid(EPC)cells.Silencing of LcSOCS3 correspondingly up-regulated the expression of IFNi,IFNh,PKR,Viperin,and Mx in large yellow croaker head kidney(LYCK)cells.Additionally,LcSOCS3 was shown to interact with Signal Transducer and Activator of Transcription 1(STAT1)which may inhibit STAT1 translocating into the nucleus.This speculation was supported by the increased phosphorylation level of STAT1 in head kidney leukocytes after LcSOCS3 silencing.These results indicated that LcSOCS3 functioned as a potential negative regulator of type I IFN signaling in large yellow croaker through its interaction with STAT1.

TRIM4 modulates type I interferon induction and cellular antiviral response by targeting RIG-I for K63-1inked ubiquitination

RIG-I is a pivotal cytoplasmic sensor that recognizes different species of viral RNAs. This recognition leads to activation of the transcription factors NF-κB and IRF3, which collaborate to induce type I interferons （IFNs） and innate antiviral response. In this study, we identified the TRIM family protein TRIM4 as a positive regulator of RIG-I-mediated IFN induction. Overexpression of TRIM4 potentiated virus-triggered activation of IRF3 and NF-κB, as well as IFN-13 induction, whereas knockdown of TRIM4 had opposite effects. Mechanistically, TRIM4 associates with RIG-I and targets it for K63-linked poiyubiquitination. Our findings demonstrate that TRIM4 is an important regulator of the virus-induced IFN induction pathways by mediating RIG-I for K63-Unked ubiquitination.

MicroRNA-548 down-regulates host antiviral response via direct targeting of IFN-λ1

Interferon(IFN)-mediated pathways are a crucial part of the cellular response against viral infection.Type III IFNs,which include IFN-λ1,2 and 3,mediate antiviral responses similar to Type I IFNs via a distinct receptor complex.IFN-λ1 is more effective than the other two members.Transcription of IFN-λ1 requires activation of IRF3/7 and nuclear factor-kappa B(NF-κB),similar to the transcriptional mechanism of Type I IFNs.Using reporter assays,we discovered that viral infection in-duced both IFN-λ1 promoter activity and that of the 3′-untranslated region(UTR),indicating that IFN-λ1 expression is also regulated at the post-transcriptional level.After analysis with microRNA(miRNA)prediction programs and 3′UTR targeting site assays,the miR-NA-548 family,including miR-548b-5p,miR-548c-5p,miR-548i,miR-548j,and miR-548n,was identified to target the 3′UTR of IFN-λ1.Further study demonstrated that miRNA-548 mimics down-regulated the expression of IFN-λ1.In contrast,their inhibitors,the complemen-tary RNAs,enhanced the expression of IFN-λ1 and IFN-stimulated genes.Furthermore,miRNA-548 mimics promoted infection by enterovirus-71(EV71)and ve-sicular stomatitis virus(VSV),whereas their inhibitors significantly suppressed the replication of EV71 and VSV.Endogenous miRNA-548 levels were suppressed during viral infection.In conclusion,our results sug-gest that miRNA-548 regulates host antiviral response via direct targeting of IFN-λ1,which may offer a poten-tial candidate for antiviral therapy.

Suppression of innate antiviral response by severe acute respiratory syndrome coronavirus M protein is mediated through the first transmembrane domain

Coronaviruses have developed various measures to evade innate immunity, We have previously shown that severe acute respiratory syndrome （SARS） coronavirus M protein suppresses type I interferon （IFN） production by impeding the formation of functional TRAF3-containing complex. In this study, we demonstrate that the IFN-antagonizing activity is specific to SARS coronavirus M protein and is mediated through its first transmembrane domain （TM 1） located at the N terminus. M protein from human coronavirus HKU 1 does not inhibit IFN production. Whereas N-linked glycosylation of SARS coronavirus M protein has no influence on IFN antagonism, TM1 is indispensable for the suppression of IFN production. TM 1 targets SARS coronavirus M protein and heterologous proteins to the Golgi apparatus, yet Golgi localization is required but not sufficient for IFN antagonism. Mechanistically, TM 1 is capable of binding with RIG-I, TRAF3, TBK1 and IKK~, and preventing the interaction of TRAF3 with its downstream effectors. Our work defines the molecular architecture of SARS coronavirus M orotein reouired for suooression of innate antiviral re^nnn^e.

Death-associated protein kinase 1 is an IRF3/7-interacting protein that is involved in the cellular antiviral immune response

Interferon regulatory factor （IRF） 7 has been demonstrated to be a master regulator of virus-induced type I interferon production （IFN）, and it plays a central role in the innate immune response against viruses. Here, we identified death-associated protein kinase 1 （DAPK1） as an IRF7-interacting protein by tandem affinity purification （TAP）. Viral infection induced DAPKI-IRF7 and DAPKI-IRF3 interactions and overexpression of DAPK1 enhanced virus-induced activation of the interferon-stimulated response element （ISRE） and IFN-p promoters and the expression of the IFNB1 gene. Knockdown of DAPK1 attenuated the induction of IFNB1 and RIG.lexpression triggered by viral infection or I FN-p, and they were enhanced by viral replication. In addition, viral infection or IFN-p treatment induced the expression of DAPK1. IFN-p treatment also activated DAPK1 by decreasing its phosphorylation level at serine 308. Interestingly, the involvement of DAPK1 in virus-induced signaling was independent of its kinase activity. Therefore, our study identified DAPK1 as an important regulator of the cellular antiviral response.

Kruppel-like factor 4 negatively regulates cellular antiviral mmune response

Viral infection triggers activation of the transcription factors NF-KB and IRF3, which collaborate to induce the expression of type I interferons （IFNs） and elicit innate antiviral response. In this report, we identified Kr（ippel-like factor 4 （KLF4）as a negative regulator of virus-triggered signaling. Overexpression of KLF4 inhibited virus-induced activation of ISRE and IFN-β promoter in various types of cells, while knockdown of KLF4 potentiated viral infection-triggered induction of IFNB1 and downstream genes and attenuated viral replication. In addition, KLF4 was found to be localized in the cytosol and nucleus, and viral infection promoted the translocation of KLF4 from cytosol to nucleus. Upon virus infection, KLF4 was bound to the promoter of IFNBgene and inhibited the recruitment of IRF3 to the IFNB promoter. Our study thus suggests that KLF4 negatively regulates cellular antiviral resonse.

A molecular arms race between host innate antiviral response and emerging human coronaviruses

Coronaviruses have been closely related with mankind for thousands of years. Communityacquired human coronaviruses have long been recognized to cause common cold. However,zoonotic coronaviruses are now becoming more a global concern with the discovery of highly pathogenic severe acute respiratory syndrome(SARS) and Middle East respiratory syndrome(MERS) coronaviruses causing severe respiratory diseases. Infections by these emerging human coronaviruses are characterized by less robust interferon production. Treatment of patients with recombinant interferon regimen promises beneficial outcomes, suggesting that compromised interferon expression might contribute at least partially to the severity of disease. The mechanisms by which coronaviruses evade host innate antiviral response are under intense investigations. This review focuses on the fierce arms race between host innate antiviral immunity and emerging human coronaviruses. Particularly, the host pathogen recognition receptors and the signal transduction pathways to mount an effective antiviral response against SARS and MERS coronavirus infection are discussed. On the other hand, the counter-measures evolved by SARS and MERS coronaviruses to circumvent host defense are also dissected. With a better understanding of the dynamic interaction between host and coronaviruses, it is hoped that insights on the pathogenesis of newly-identified highly pathogenic human coronaviruses and new strategies in antiviral development can be derived.

Autoubiquitination of TRIM26 links TBK1 to NEMO in RLR-mediated innate antiviral immune response

The transcription factors IRF3 and NF-kB are required for the expression of many genes involved in antiviral innate immune response,including type I interferons(IFNs)and proinflammatory cytokines.It is well established thatTBK1 isan essential kinase engageddownstream of multiple pattern-recognition receptors(PRRs)to mediate IRF3 phosphorylation and activation,whereas the precise mechanisms of TBK1 activation have not been fully elucidated yet.Here,weidentified tripartite motif 26(TRIM26)as an important regulator for RNAvirus-triggered innate immune response.Knockdown of TRIM26 impaired virus-triggered IRF3,NF-kB activation,IFN-b induction,and cellular antiviral response.TRIM26 was physically associated with TBK1 independent of viral infection.As an E3 ligase,TRIM26 underwent autoubiquitination upon viral infection.Ubiquitinated TRIM26 subsequently associated with NEMO,thus bridging TBK1–NEMOinteraction,which is critical for the recruitment of TBK1 to the VISA signalsome and activation of TBK1.Our findings suggest that TRIM26 is an important regulator of innate immune responses against RNA viruses,which functions by bridging TBK1 to NEMO and mediating the activation of TBK1.

Heat shock cognate 71 (HSC71) regulates cellular antiviral response by impairing formation of VISA aggregates

In response to viral infection, RIG-I-like RNA helicases detect viral RNA and signal through the mitochondrial adapter protein VISA. VISA activation leads to rapid activation of transcription factors IRF3 and NF-κB, which collaborate to induce transcription of type I interferon (IFN) genes and cellular antiviral response. It has been demonstrated that VISA is activated by forming prion-like aggregates. However, how this process is regulated remains unknown. Here we show that overexpression of HSC71 resulted in potent inhibition of virus-triggered transcription of IFNB1 gene and cellular antiviral response. Consistently, knockdown of HSC71 had opposite effects. HSC71 interacted with VISA, and negatively regulated virus-triggered VISA aggregation. These findings suggest that HSC71 functions as a check against VISA-mediated antiviral response.

Current research progress on the viral immune evasion mechanisms of African swine fever virus

African swine fever(ASF),caused by the ASF virus(ASFV),is an acute,severe,and highly contagious infectious disease in domestic pigs and wild boars.Domestic pigs infected with a virulent ASFV strain can have morbidity and mortality rates of up to 100%.The epidemic of ASF has caused serious economic losses to the global pig industry.Currently,there is no safe and efective vaccine or specifc drug for treating ASF.Therefore,ASFV still poses a great threat to pig factories.ASFV is a double-stranded DNA virus with a complex icosahedral multilayer structure.The ASFV genome contains 150-170 open reading frames(ORFs)that encode 150-200 proteins.Some ASFV-encoded proteins are involved in virus invasion,genome replication,DNA repair,and virion formation.Some ASFV proteins execute immunomodulatory functions by regulating the host antiviral innate immune response.Accumulating studies have shown that the immunomodulatory functions of ASFV genes are closely related to the virulence and pathogenicity of ASFV isolates.This review summarizes the research advances on ASFV immune evasion mechanisms in African swine fever patients and provides new insights for developing attenuated live vaccine candidates to prevent and control ASF.