TLR and RLR Signaling Are Reprogrammed in Opposite Directions after Detection of Viral Infection

Nsp10-interacting host protein SAP18 restricts PEDV replication in Marc-145 cells via enhancing dephosphorylation of RIG-I

PEDV, a single-stranded RNA virus, causes significant economic losses in the pig industry. Sin3-associated protein 18 (SAP18) is known for its role in transcriptional inhibition and RNA splicing. However, research on SAP18's involvement in PEDV infection is limited. Here, we identified an interaction between SAP18 and PEDV nonstructural protein 10 (Nsp10) using immunoprecipitation-mass spectrometry (IP-MS) and confirmed it through immunoprecipitation and laser confocal microscopy. Additionally, PEDV Nsp10 reduced SAP18 protein levels and induced its cytoplasmic accumulation. Overexpressing SAP18 suppressed PEDV replication, meanwhile its knockdown via short interfering RNA (siRNA) enhanced replication. SAP18 overexpression boosted IRF3 and NF-κB P65 phosphorylation, nuclear translocation, and IFN-β antiviral response. Furthermore, SAP18 upregulated RIG-I expression and facilitated its dephosphorylation, while SAP18 knockdown had the opposite effect. Finally, SAP18 interacted with phosphatase 1 (PP1) catalytic subunit alpha (PPP1CA), promoting PPP1CA-RIG-I interaction during PEDV infection. These findings highlight SAP18's role in activating the type I interferon pathway and inhibiting viral replication by promoting RIG-I dephosphorylation through its interaction with PPP1CA.

Motor, Cognitive, and Behavioral Impairment in TLR3 and TLR9 Deficient Male Mice: Insights into the Non-Immunological Roles of Toll-Like Receptors

BACKGROUND

Toll-like receptors (TLRs) play a critical role in initiating the innate immune response to infection or injury. Recent studies have uncovered their intriguing functions as moonlighting proteins involved in various biological processes, including development, learning, and memory. However, the specific functions of individual TLRs are still largely unknown.

AIMS

We investigated the effects of TLR3 and TLR9 receptor deficiency on motor, cognitive, and behavioral functions during development using genetically modified male mice of different ages.

METHODS

We evaluated the motor coordination, anxiety-like behavior, spatial learning, and working memory of male mice lacking the TLR3 and TLR9 genes at different ages (two, four, six, and eight months) using the rotarod, open field, water maze, and T-maze tests.

RESULTS

We observed that the deletion of either TLR3 or TLR9 resulted in impaired motor performance. Furthermore, young TLR3-deficient mice exhibited reduced anxiety-like behavior and spatial learning deficits; however, their working memory was unaffected. In contrast, young TLR9-knockout mice showed hyperactivity and a tendency toward decreased working memory.

CONCLUSIONS

These findings provide valuable insights into the broader roles of the TLR system beyond the innate immune response, revealing its involvement in pathways associated with the central nervous system. Importantly, our results establish a strong association between the endosomal receptors TLR3 and TLR9 and the performance of motor, cognitive, and behavioral tasks that change over time. This study contributes to the growing body of research on the multifaceted functions of TLRs and enhances our understanding of their participation in non-immune-related processes.

Sequential MAVS and MyD88/TRIF signaling triggers anti-viral responses of tick-borne encephalitis virus-infected murine astrocytes

Tick-borne encephalitis virus (TBEV), a member of the Flaviviridae family, is typically transmitted upon tick bite and can cause meningitis and encephalitis in humans. In TBEV-infected mice, mitochondrial antiviral-signaling protein (MAVS), the downstream adaptor of retinoic acid-inducible gene-I (RIG-I)-like receptor (RLR) signaling, is needed to induce early type I interferon (IFN) responses and to confer protection. To characterize the brain-resident cell subset that produces protective IFN-β in TBEV-infected mice, we isolated neurons, astrocytes, and microglia from mice and exposed these cell types to TBEV in vitro. Under such conditions, neurons showed the highest percentage of infected cells, whereas astrocytes and microglia were infected to a lesser extent. In the supernatant (SN) of infected neurons, IFN-β was not detectable, while infected astrocytes showed high and microglia low IFN-β expression. Transcriptome analyses of astrocytes implied that MAVS signaling was needed early after TBEV infection. Accordingly, MAVS-deficient astrocytes showed enhanced TBEV infection and significantly reduced early IFN-β responses. Nevertheless, at later time points, moderate amounts of IFN-β were detected in the SN of infected MAVS-deficient astrocytes. Transcriptome analyses indicated that MAVS deficiency negatively affected the induction of early anti-viral responses, which resulted in significantly increased TBEV replication. Treatment with MyD88 and TRIF inhibiting peptides reduced only late IFN-β responses of TBEV-infected WT astrocytes and blocked entirely IFN-β responses of infected MAVS-deficient astrocytes. Thus, upon TBEV exposure of brain-resident cells, astrocytes are important IFN-β producers showing biphasic IFN-β induction that initially depends on MAVS and later on MyD88/TRIF signaling.

Cells Stimulated with More Than One Toll-Like Receptor-Ligand in the Presence of a MyD88 Inhibitor Augmented Interferon-β via MyD88-Independent Signaling Pathway

Host exposure to pathogens engage multiple pathogen recognition receptors (PRRs) including toll-like receptors (TLRs); recruit intracellular signaling adaptor proteins primarily myeloid differentiation primary response protein 88 (MyD88) for activating downstream signaling cascades, which culminate in the production of type I interferons (IFNs), proinflammatory cytokines, and chemokines; and impede pathogen replication and dissemination. However, recent studies highlight that absence of MyD88 increased antiviral type I IFN induction, and MyD88^-/- mice showed a higher survival rate compared with the low survival rate of the MyD88^+/+ mice, implicating MyD88 limits antiviral type I IFN response. As a single infectious agent may harbor multiple PRR agonists, which trigger different sets of TLR-initiated immune signaling, we examined whether MyD88 inhibition during stimulation of cells with more than one TLR-ligand would augment type I IFN. We stimulated human U87- and TLR3-transfected HEK293-TLR7 cells with TLR-ligands, such as lipopolysaccharides (LPS) (TLR4-ligand) plus poly I:C (TLR3-ligand) or imiquimod (R837, TLR7-ligand) plus poly I:C, in the presence of compound 4210, a previously reported MyD88 inhibitor, and measured IFN-β response using an enzyme-linked immunosorbent assay. Our results showed that when U87- or TLR3-transfected HEK293-TLR7 cells were stimulated with TLR-ligands, such as poly I:C plus LPS or poly I:C plus R837, IFN-β production was significantly increased with MyD88 inhibition in a dose-dependent manner. Collectively, these results indicate that during more than one TLR-ligand-induced immune signaling event, impairment of antiviral type I IFN response was restored by inhibition of MyD88 through MyD88-independent pathway of type I IFN signaling, thus, offer a MyD88-targeted approach for type I IFN induction.

HMGB1 promotes CXCL12-dependent egress of murine B cells from Peyer's patches in homeostasis

High mobility group box-1 protein (HMGB1) is an alarmin that, once released, promotes inflammatory responses, alone and as a complex with the chemokine CXCL12. Here, we report that the HMGB1-CXCL12 complex plays an essential role also in homeostasis by controlling the migration of B lymphocytes. We show that extracellular HMGB1 is critical for the CXCL12-dependent egress of B cells from the Peyer's patches (PP). This promigratory function of the complex was restricted to the PPs, since HMGB1 was not required for B-cell migratory processes in other locations. Accordingly, we detected higher constitutive levels of the HMGB1-CXCL12 complex in PPs than in other lymphoid organs. HMGB1-CXCL12 in vivo inhibition was associated with a reduced basal IgA production in the gut. Collectively, our results demonstrate a role for the HMGB1-CXCL12 complex in orchestrating B-cell trafficking in homeostasis, and provide a novel target to control lymphocyte migration in mucosal immunity.

Cross talk between hepatitis B virus and innate immunity of hepatocytes

Innate immunity plays a major role in controlling viral infections. Recent exploration of sodium taurocholate co-transporting polypeptide receptor as specific hepatitis B virus (HBV) receptor in human hepatocytes has provided appropriate cell culture tools to study the innate immunity of hepatocytes and its cross talk with HBV. In this review, we give a brief update on interaction between HBV and innate immunity using the currently available in vitro cellular models that support the complete life cycle of HBV. We will discuss how HBV can act as a 'stealth' virus to counteract the innate immune responses mediated by the pathogen recognition receptors of hepatocytes and escape the first line of surveillance of the host immune system. We give an overview of the cellular components of innate immunity that present in these in vitro models and discuss how activating these innate immunity components may contribute to the eradication of HBV infection.

RDUR, a lncRNA, Promotes Innate Antiviral Responses and Provides Feedback Control of NF-κB Activation

Influenza A virus (IAV), a highly infectious respiratory pathogen, remains a major threat to global public health. Numerous long non-coding RNAs (lncRNAs) have been shown to be implicated in various cellular processes. Here, we identified a new lncRNA termed RIG-I-dependent IAV-upregulated noncoding RNA (RDUR), which was induced by infections with IAV and several other viruses. Both in vitro and in vivo studies revealed that robust expression of host RDUR induced by IAV was dependent on the RIG-I/NF-κB pathway. Overexpression of RDUR suppressed IAV replication and downregulation of RDUR promoted the virus replication. Deficiency of mouse RDUR increased virus production in lungs, body weight loss, acute organ damage and consequently reduced survival rates of mice, in response to IAV infection. RDUR impaired the viral replication by upregulating the expression of several vital antiviral molecules including interferons (IFNs) and interferon-stimulated genes (ISGs). Further study showed that RDUR interacted with ILF2 and ILF3 that were required for the efficient expression of some ISGs such as IFITM3 and MX1. On the other hand, we found that while NF-κB positively regulated the expression of RDUR, increased expression of RDUR, in turn, inactivated NF-κB through a negative feedback mechanism to suppress excessive inflammatory response to viral infection. Together, the results demonstrate that RDUR is an important lncRNA acting as a critical regulator of innate immunity against the viral infection.

TLR3 activation by Zika virus stimulates inflammatory cytokine production which dampens the antiviral response induced by RIG-I-like receptors

Infection with the Zika virus (ZIKV), a member of the Flaviviridae family, can cause serious neurological disorders, most notably microcephaly in newborns. Here we investigated the innate immune response to ZIKV infection in cells of the nervous system. In human neural progenitor cells (hNPCs), a target for ZIKV infection and likely involved in ZIKV-associated neuropathology, viral infection failed to elicit an antiviral interferon (IFN) response. However, pharmacological inhibition of TLR3 partially restored this deficit. Analogous results were obtained in human iPSC-derived astrocytes, which are capable of mounting a strong antiviral cytokine response. There, ZIKV is sensed by both RIG-I and MDA5 and induces an IFN response as well as expression of pro-inflammatory cytokines such as interleukin-6 (IL-6). Upon inhibition of TLR3, also in astrocytes the antiviral cytokine response was enhanced, whereas amounts of pro-inflammatory cytokines were reduced. To study the underlying mechanism, we used human epithelial cells as an easy to manipulate model system. We found that ZIKV is sensed in these cells by RIG-I to induce a robust IFN response and by TLR3 to trigger the expression of pro-inflammatory cytokines, including IL-6. ZIKV induced upregulation of IL-6 activated the STAT3 pathway, which decreased STAT1 phosphorylation in a SOCS-3 dependent manner, thus reducing the IFN response. In conclusion, we show that TLR3 activation by ZIKV suppresses IFN responses triggered by RIG-I-like receptors.ImportanceZika virus (ZIKV) has a pronounced neurotropism and infections with this virus can cause serious neurological disorders, most notably microcephaly and the Guillain-Barré syndrome. Our studies reveal that during ZIKV infection, recognition of viral RNA by TLR3 enhances the production of inflammatory cytokines and suppresses the interferon response triggered by RIG-I-like receptors (RLR) in a SOCS3-dependent manner, thus facilitating virus replication. The discovery of this crosstalk between antiviral (RLR) and inflammatory (TLR) responses may have important implications for our understanding of ZIKV-induced pathogenesis.

Innate Receptor Activation Patterns Involving TLR and NLR Synergisms in COVID-19, ALI/ARDS and Sepsis Cytokine Storms: A Review and Model Making Novel Predictions and Therapeutic Suggestions

Severe COVID-19 is characterized by a “cytokine storm”, the mechanism of which is not yet understood. I propose that cytokine storms result from synergistic interactions among Toll-like receptors (TLR) and nucleotide-binding oligomerization domain-like receptors (NLR) due to combined infections of SARS-CoV-2 with other microbes, mainly bacterial and fungal. This proposition is based on eight linked types of evidence and their logical connections. (1) Severe cases of COVID-19 differ from healthy controls and mild COVID-19 patients in exhibiting increased TLR4, TLR7, TLR9 and NLRP3 activity. (2) SARS-CoV-2 and related coronaviruses activate TLR3, TLR7, RIG1 and NLRP3. (3) SARS-CoV-2 cannot, therefore, account for the innate receptor activation pattern (IRAP) found in severe COVID-19 patients. (4) Severe COVID-19 also differs from its mild form in being characterized by bacterial and fungal infections. (5) Respiratory bacterial and fungal infections activate TLR2, TLR4, TLR9 and NLRP3. (6) A combination of SARS-CoV-2 with bacterial/fungal coinfections accounts for the IRAP found in severe COVID-19 and why it differs from mild cases. (7) Notably, TLR7 (viral) and TLR4 (bacterial/fungal) synergize, TLR9 and TLR4 (both bacterial/fungal) synergize and TLR2 and TLR4 (both bacterial/fungal) synergize with NLRP3 (viral and bacterial). (8) Thus, a SARS-CoV-2-bacterium/fungus coinfection produces synergistic innate activation, resulting in the hyperinflammation characteristic of a cytokine storm. Unique clinical, experimental and therapeutic predictions (such as why melatonin is effective in treating COVID-19) are discussed, and broader implications are outlined for understanding why other syndromes such as acute lung injury, acute respiratory distress syndrome and sepsis display varied cytokine storm symptoms.

COVID-19: Oxidative Preconditioning as a Potential Therapeutic Approach

This Article summarizes the likely benefits of central nervous system oxidative preconditioning in the reduction of COVID-19 based on its putative pathogenesis. The current COVID-19 outbreak caused a pandemic with millions of infected patients and death cases worldwide. The clinical features of severe acute respiratory syndrome coronavirus (SARS-CoV) was initially linked with respiratory disorders, but recent studies have reported alterations of neurological and cerebrovascular functions in COVID-19 patients. The main viral infection features are related to cell death, inflammation, and cytokine generation, which can be associated with the dysregulation of redox systems or oxidative stress. However, until now, there is no available and effective therapeutic approach. Thus, it is necessary to search for care and adequate protection against the disease, especially for susceptible and vulnerable groups. Preconditioning, a well-known antioxidative stress and anti-inflammatory approach, is protective against many neurological age-related disorders. COVID-19 severity and morbidity have been observed in elderly patients. The aim of the present study is to elucidate the possible protective role of oxidative preconditioning in aged patients at high risk of developing severe COVID-19 complications.

A small molecule inhibitor of MyD88 exhibits broad spectrum antiviral activity by up regulation of type I interferon

Recent studies highlight that infection with Coxsackievirus B3, Venezuelan equine encephalitis virus (VEEV), Marburg virus, or stimulation using poly I:C (dsRNA), upregulates the signaling adaptor protein MyD88 and impairs the host antiviral type I interferon (IFN) responses. In contrast, MyD88 deficiency (MyD88^-/-) increases the type I IFN and survivability of mice implying that MyD88 up regulation limits the type I IFN response. Reasoning that MyD88 inhibition in a virus-like manner may increase type I IFN responses, our studies revealed lipopolysaccharide stimulation of U937 cells or poly I:C stimulation of HEK293-TLR3, THP1 or U87 cells in the presence of a previously reported MyD88 inhibitor (compound 4210) augmented IFN-β and RANTES production. Consistent with these results, overexpression of MyD88 decreased IFN-β, whereas MyD88 inhibition rescued IFN-β production concomitant with increased IRF3 phosphorylation, suggesting IRF-mediated downstream signaling to the IFN-β response. Further, compound 4210 treatment inhibited MyD88 interaction with IRF3/IRF7 indicating that MyD88 restricts type I IFN signaling through sequestration of IRF3/IRF7. In cell based infection assays, compound 4210 treatment suppressed replication of VEEV, Eastern equine encephalitis virus, Ebola virus (EBOV), Rift Valley Fever virus, Lassa virus, and Dengue virus with IC₅₀ values ranging from 11 to 42 μM. Notably, administration of compound 4210 improved survival, weight change, and clinical disease scores in mice following challenge with VEEV TC-83 and EBOV. Collectively, these results provide evidence that viral infections responsive to MyD88 inhibition lead to activation of IRF3/IRF7 and promoted a type I IFN response, thus, raising the prospect of an approach of host-directed antiviral therapy.

Double-Stranded Structure of the Polyinosinic-Polycytidylic Acid Molecule to Elicit TLR3 Signaling and Adjuvant Activity in Murine Intranasal A(H1N1)pdm09 Influenza Vaccination

Polyinosinic-polycytidylic acid (PIC) is a potent double-stranded RNA (dsRNA) adjuvant useful in intranasal influenza vaccination. In mice, the intensity and duration of immune responses to PIC correlated with the double-stranded chain length. A rational method to avoid PIC chain extension in PIC production is to use multiple short poly(I) molecules and one long poly(C) molecule for PIC assembly. In this study, we elucidate that a newly developed uPIC100-400 molecule comprising multiple 0.1 kb poly(I) molecules and one 0.4 kb poly(C) molecule effectively enhanced the immune responses in mice, by preventing the challenged viral propagation and inducing hemagglutinin-specific IgA, after intranasal A(H1N1)pdm09 influenza vaccination. Reduced intraperitoneal toxicity of PIC prepared with multiple short poly(I) molecules in mice indicates the widened effective range of uPIC100-400 as an adjuvant. In contrast to uPIC100-400, the PIC molecule comprising multiple 0.05 kb poly(I) molecules failed to elicit mouse mucosal immunity. These results were consistent with TLR3 response but not retinoic acid inducible gene I (RIG-I)-like receptor response in the cell assays, which suggests that the adjuvant effect of PIC in mouse intranasal immunization depends on TLR3 signaling. In conclusion, the double-stranded PIC with reduced toxicity developed in this study would contribute to the development of PIC-adjuvanted vaccines.

Histone demethylase KDM6A promotes somatic cell reprogramming by epigenetically regulating the PTEN and IL-6 signal pathways

Aberrant epigenetic reprogramming is one of the major barriers for somatic cell reprogramming. Although our previous study has indicated that H3K27me3 demethylase KDM6A can improve the nuclear reprogramming efficiency, the mechanism remains unclear. In this study, we demonstrate that the overexpression of Kdm6a may improve induced pluripotent stem cell (iPSC) reprogramming efficiency in a demethylase enzymatic activity-dependent manner. KDM6A erased H3K27me3 on pluripotency- and metabolism-related genes, and consequently facilitated changing the gene expression profile and metabolic pattern to an intermediate state. Furthermore, KDM6A may promote IL-6 expression, and the secreted IL-6 may further improve iPSC reprogramming efficiency. In addition, KDM6A may promote PTEN expression to decrease p-AKT and p-mTOR levels, which in turn facilitates reprogramming. Overall, our results reveal that KDM6A may promote iPSC reprogramming efficiency by accelerating changes in the gene expression profile and the metabolic pattern in a demethylation-activity-dependent manner. These results may provide an insight into the relationship between epigenomics, transcriptomics, metabolomics, and reprogramming.

Harnessing the immune system to fight cancer with Toll-like receptor and RIG-I-like receptor agonists

Cancer immunotherapy has come of age with the advent of immune checkpoint inhibitors. In this article we review how agonists for receptors of the innate immune system, the Toll-like receptors and the RIG-I-like receptors, impact anticancer immune responses. Treatment with these agonists enhances the activity of anticancer effector cells, such as cytotoxic T cells and NK cells, and at the same time blocks the activity of immunosuppressive cell types such as regulatory T cells and myeloid-derived suppressor cells. These compounds also impact the recruitment of immune cells to the tumor. The phenomena of pattern-recognition receptor tolerance and reprogramming and their implications for immunotherapy are discussed. Finally, novel delivery systems that target the immune-stimulating drugs to the tumor or the tumor-draining lymph nodes to enhance their efficacy and safety are presented.

microRNAs in viral acute respiratory infections: immune regulation, biomarkers, therapy, and vaccines

MicroRNAs (miRNAs) are single-stranded RNAs of 17-24 nt. These molecules regulate gene expression at the post-transcriptional level and are differentially expressed in viral acute respiratory infections (ARIs), which are responsible for high morbidity and mortality around the world. In recent years, miRNAs have been studied in order to discover anti-viral ARI drug targets as well as biomarkers for diagnosis, severity, and prognosis. This review presents an analysis of the regulatory response to viral ARIs of miRNAs, including their participation in the innate immune response, their utility as biomarkers, and their potential for future therapies and vaccine development.

Analysis of the Long-Lived Responses Induced by Immunostimulants and Their Effects on a Viral Infection in Zebrafish (Danio rerio)

In recent years, the innate immune response has gained importance since evidence indicates that after an adequate priming protocol, it is possible to obtain some prolonged and enhanced immune responses. Nevertheless, several factors, such as the timing and method of administration of the immunostimulants, must be carefully considered. An inappropriate protocol can transform the treatments into a double-edged sword for the teleost immune system, resulting in a stressful and immunosuppressive state. In this work, we analyzed the long-term effects of different stimuli (β-glucans, lipopolysaccharide, and polyinosinic:polycytidylic acid) on the transcriptome modulation induced by Spring Viremia Carp Virus (SVCV) in adult zebrafish (Danio rerio) and on the mortality caused by this infection. At 35 days post-immunostimulation, the transcriptome was found to be highly altered compared to that of the control fish, and these stimuli also conditioned the response to SVCV challenge, especially in the case of β-glucans. No protection against SVCV was found with any of the stimuli, and non-significant higher mortalities were even observed, especially with β-glucans. However, in the short term (pre-stimulation with β-glucan and infection after 7 days), slight protection was observed after infection. The transcriptome response in the zebrafish kidney at 35 days posttreatment with β-glucans revealed a significant response associated with stress and immunosuppression. The identification of genes that were differentially expressed before and after the infection seemed to indicate a high energy cost of the immunostimulation that was prolonged over time and could explain the lack of protection against SVCV. Differential responses to stress and alterations in lipid metabolism, the tryptophan–kynurenine pathway, and interferon-gamma signaling seem to be some of the mechanisms involved in this response, which represents the end of trained immunity and the beginning of a stressful state characterized by immunosuppression.

RIG-I-Like Receptors as Novel Targets for Pan-Antivirals and Vaccine Adjuvants Against Emerging and Re-Emerging Viral Infections

Emerging and re-emerging viruses pose a significant public health challenge around the world, among which RNA viruses are the cause of many major outbreaks of infectious diseases. As one of the early lines of defense in the human immune system, RIG-I-like receptors (RLRs) play an important role as sentinels to thwart the progression of virus infection. The activation of RLRs leads to an antiviral state in the host cells, which triggers the adaptive arm of immunity and ultimately the clearance of viral infections. Hence, RLRs are promising targets for the development of pan-antivirals and vaccine adjuvants. Here, we discuss the opportunities and challenges of developing RLR agonists into antiviral therapeutic agents and vaccine adjuvants against a broad range of viruses.

NAB2 is a novel immune stimulator of MDA-5 that promotes a strong type I interferon response

Novel adjuvants are needed to increase the efficacy of vaccine formulations and immune therapies for cancer and chronic infections. In particular, adjuvants that promote a strong type I IFN response are required, since this cytokine is crucial for the development of efficient anti-tumoral and anti-viral immunity. Nucleic acid band 2 (NAB2) is a double-stranded RNA molecule isolated from yeast and identified as an agonist of the pattern-recognition receptors TLR3 and MDA-5. We compared the ability of NAB2 to activate innate immunity with that of poly(I:C), a well-characterized TLR3 and MDA-5 agonist known for the induction of type I IFN. NAB2 promoted stronger IFN-α production and induced a higher activation state of both murine and human innate immune cells compared to poly(I:C). This correlated with a stronger activation of the signalling pathway downstream of MDA-5, and IFN-α induction was dependent on MDA-5. Upon injection, NAB2 induced higher levels of serum IFN-α in mice than poly(I:C). These results suggest that NAB2 has the potential to become an efficient adjuvant for the induction of type-I IFN responses in therapeutic immunization against cancer or infections.

Down-regulation of increased TRAF6 expression in the peripheral mononuclear cells of patients with primary Sjögren's syndrome by an EBV-EBER1-specific synthetic single-stranded complementary DNA molecule

AIM

We described earlier a simultaneously increased that the increased expression of miRNA-146a/b was accompanied by an increase in the expression of and TRAF6 and a decrease in the expression of IRAK1 genes in the peripheral mononuclear cells (PBMCs) of patients with primary Sjogren's syndrome (pSS) patients. Recently, the expression of EBV encoded. RNA (EBER) was published in the B cells of salivary glands of in pSS. In the present study, we applied an EBV-EBER1 specific synthetic single stranded complementary DNA molecule (EBV-EBER1-cDNA) to test whether any EBER1 related effect exists also in PBMCs of pSS patients.

METHODS

In the PBMCs of pSS patients and healthy controls, we investigated in vitro the effects of a synthetic single stranded EBV-EBER1-cDNA molecule, synthetic double-stranded (ds)RNA polyinosinic-polycytidylic acid [poly (I:C)] and polyadenylic acid potassium salt poly-adenylic acid [poly-(A)] on the expression of TRAF6 gene tested by qRTPCR. The release of interferon -α was detected by ELISA.

RESULTS

EBV-EBER1-cDNA resulted in a significant reduction in the expression of TRAF6 in the cells of patients, but in the healthy controls not, whereas the treatments with poly (I:C) and poly-(A) could not reduce the TRAF6 over-expression. No release of EBER1 could be observed in the culture supernatants of patients with pSS. Only the treatment with poly (I:C) resulted in a significant increase of interferon -α release, and only in the heathy controls. No release of EBER1 molecules took place during the culturing of cells. EBV-EBER- cDNA acted functionally on the cells of patients only.

CONCLUSION

These findings give a further evidence of the linkage between EBV and pSS, furthermore, they show the possible role of EBV-EBER1 in the induction of increased TRAF6 expression in the peripheral B cells of Sjögren's patients.

USP19 suppresses cellular type I interferon signaling by targeting TRAF3 for deubiquitination

AIM

To investigate host factors that mediate the immune escape of enterovirus 71 (EV71) in the context of deubiquitinating enzymes.

MATERIALS & METHODS

Utilize PCR array to screen candidate genes that may be involved in EV71-induced cellular antiviral immune responses, and utilize protein mass spectrometry analysis to identify the functional targets of the candidate regulator.

RESULTS

EV71 infection induces the upregulation of ubiquitin-specific protease 19 (USP19) gene expression, which negatively regulates cellular antiviral type I interferon signaling. Additionally, we identify that USP19 suppresses cellular type I interferon signaling by targeting tumor necrosis factor receptor-associated factor 3 (TRAF3) molecule and decreasing TRAF3 ubiquitination of K63-linkage.

CONCLUSION

This work suggests that USP19 is a previously unrecognized regulator employed by EV71 to evade host antiviral defenses.

MDA5 Induces a Stronger Interferon Response than RIG-I to GCRV Infection through a Mechanism Involving the Phosphorylation and Dimerization of IRF3 and IRF7 in CIK Cells

Retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5) are critical cytosolic sensors that trigger the production of interferons (IFNs). Though their recognition functions are well identified, their unique roles in the downstream signal transduction remain to be elucidated. Herein, we report the differential effect between grass carp (Ctenopharyngodon idella) MDA5 (CiMDA5) and CiRIG-I on the production of various IFNs upon grass carp reovirus (GCRV) infection in C. idella kidney (CIK) cell line. In CIK cells, grass carp IFN1 (CiIFN1) and CiIFN3 are relatively highly expressed while CiIFN2 and CiIFN4 are relatively slightly expressed. Following GCRV infection, CiMDA5 induces a more extensive type I IFN response than CiRIG-I. Further investigation reveals that both CiMDA5 and CiRIG-I facilitate the expression and total phosphorylation levels of grass carp IFN regulatory factor (IRF) 3 (CiIRF3) and CiIRF7 upon GCRV infection or poly(I:C) stimulation. However, the difference is that CiRIG-I decreases the threonine phosphorylation level of CiIRF7. As a consequence, CiMDA5 enhances the heterodimerization of CiIRF3 and CiIRF7 and homodimerization of CiIRF7, whereas CiRIG-I facilitates the heterodimerization but attenuates homodimerization of CiIRF7. Moreover, the present study suggests that CiIRF3 and CiIRF7 heterodimers and CiIRF7 homodimers are able to induce more extensive IFN-I responses than CiIRF3 homodimers under GCRV infection. Additionally, CiMDA5 induces a stronger type II IFN (IFN-II) response against GCRV infection than CiRIG-I. Collectively, these results demonstrate that CiMDA5 plays a more potent role than CiRIG-I in IFN response to GCRV infection through differentially regulating the phosphorylation and dimerization of CiIRF3 and CiIRF7.

Manipulation of viral infection by deubiquitinating enzymes: new players in host-virus interactions

Ubiquitination regulates gene expression post-translationally through the well-characterized ubiquitin system, which has been clearly established to have important functions in the regulation of many intracellular biological activities. Being obligate intracellular microbes, viruses inevitably co-opt this conserved host cytosolic machinery to accomplish their own life cycle, from entry into host cells to the release of progeny viral particles. Deubiquitinating enzymes (DUBs) remove ubiquitins from target proteins to reverse the modification of ubiquitination, and thusly affect a great number of signaling pathways, as well as viral infections. This review presents what is known about how viruses bypass or employ DUBs to evade host immune defenses and discusses new therapeutic strategies targeting DUBs for diseases treatment.

Reprogramming of TLR7 signaling enhances antitumor NK and cytotoxic T cell responses

Toll-like receptor (TLR) 7 agonists are effective in topical application for the immunotherapy of skin cancers, but their performance for the systemic treatment of solid tumors is limited by the development of TLR tolerance. In this study, we describe a novel strategy to overcome TLR tolerance and enhance TLR7-dependent antitumor immune responses through reprogramming of TLR signaling pathways. The sensitivity of TLR7 signaling in dendritic cells (DC) was increased by prior stimulation with the dsRNA poly(I:C) that mimics virally induced immune activation. Timing of the stimulations was important, as sequential stimulation with poly(I:C) and the TLR7 agonist R848 interspaced by 24 h induced higher MAPK and NFkB signaling in DC than the simultaneous application of the same ligands. DC activated by sequential poly(I:C)/R848 stimulation efficiently induced Th1 differentiation and primed NK-cell and cytotoxic T-cell responses. We have developed a treatment regimen taking advantage of TLR7 reprogram-ming that cured over 80% of large immunogenic tumors in mice by the action of NK cells and cytotoxic T cells. These results have direct implications for the use of these clinically established ligands in the immunotherapy of cancer.