Early IFNß secretion determines variable downstream IL-12p70 responses upon TLR4 activation.

The interleukin-12 (IL-12) family comprises the only heterodimeric cytokines mediating diverse functional effects. We previously reported a striking bimodal IL-12p70 response to lipopolysaccharide (LPS) stimulation in healthy donors. Herein, we demonstrate that interferon ß (IFNß) is a major upstream determinant of IL-12p70 production, which is also associated with numbers and activation of circulating monocytes. Integrative modeling of proteomic, genetic, epigenomic, and cellular data confirms IFNß as key for LPS-induced IL-12p70 and allowed us to compare the relative effects of each of these parameters on variable cytokine responses. Clinical relevance of our findings is supported by reduced IFNß-IL-12p70 responses in patients hospitalized with acute severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or chronically infected with hepatitis C (HCV). Importantly, these responses are resolved after viral clearance. Our systems immunology approach defines a better understanding of IL-12p70 and IFNß in healthy and infected persons, providing insights into how common genetic and epigenetic variation may impact immune responses to bacterial infection.

Discovery Proteomics Analysis Determines That Driver Oncogenes Suppress Antiviral Defense Pathways Through Reduction in Interferon-ß Autocrine Stimulation.

Since the discovery of oncogenes, there has been tremendous interest to understand their mechanistic basis and to develop broadly actionable therapeutics. Some of the most frequently activated oncogenes driving diverse cancers are c-MYC, EGFR, HER2, AKT, KRAS, BRAF, and MEK. Using a reductionist approach, we explored how cellular proteomes are remodeled in isogenic cell lines engineered with or without these driver oncogenes. The most striking discovery for all oncogenic models was the systematic downregulation of scores of antiviral proteins regulated by type 1 interferon. These findings extended to cancer cell lines and patient-derived xenograft models of highly refractory pancreatic cancer and osteosarcoma driven by KRAS and MYC oncogenes. The oncogenes reduced basal expression of and autocrine stimulation by type 1 interferon causing remarkable convergence on common phenotypic and functional profiles. In particular, there was dramatically lower expression of dsRNA sensors including DDX58 (RIG-I) and OAS proteins, which resulted in attenuated functional responses when the oncogenic cells were treated with the dsRNA mimetic, polyI:C, and increased susceptibility to infection with an RNA virus shown using SARS-CoV-2. Our reductionist approach provides molecular and functional insights connected to immune evasion hallmarks in cancers and suggests therapeutic opportunities.

Imiquimod Boosts Interferon Response, and Decreases ACE2 and Pro-Inflammatory Response of Human Bronchial Epithelium in Asthma.

Background: Both anti-viral and anti-inflammatory bronchial effects are warranted to treat viral infections in asthma. We sought to investigate if imiquimod, a TLR7 agonist, exhibits such dual actions in ex vivo cultured human bronchial epithelial cells (HBECs), targets for SARS-CoV-2 infectivity. Objective: To investigate bronchial epithelial effects of imiquimod of potential importance for anti-viral treatment in asthmatic patients. Methods: Effects of imiquimod alone were examined in HBECs from healthy (N=4) and asthmatic (N=18) donors. Mimicking SARS-CoV-2 infection, HBECs were stimulated with poly(I:C), a dsRNA analogue, or SARS-CoV-2 spike-protein 1 (SP1; receptor binding) with and without imiquimod treatment. Expression of SARS-CoV-2 receptor (ACE2), pro-inflammatory and anti-viral cytokines were analyzed by RT-qPCR, multiplex ELISA, western blot, and Nanostring and proteomic analyses. Results: Imiquimod reduced ACE2 expression at baseline and after poly(I:C) stimulation. Imiquimod also reduced poly(I:C)-induced pro-inflammatory cytokines including IL-1ß, IL-6, IL-8, and IL-33. Furthermore, imiquimod increased IFN-ß expression, an effect potentiated in presence of poly(I:C) or SP1. Multiplex mRNA analysis verified enrichment in type-I IFN signaling concomitant with suppression of cytokine signaling pathways induced by imiquimod in presence of poly(I:C). Exploratory proteomic analyses revealed potentially protective effects of imiquimod on infections. Conclusion: Imiquimod triggers viral resistance mechanisms in HBECs by decreasing ACE2 and increasing IFN-ß expression. Additionally, imiquimod improves viral infection tolerance by reducing viral stimulus-induced epithelial cytokines involved in severe COVID-19 infection. Our imiquimod data highlight feasibility of producing pluripotent drugs potentially suited for anti-viral treatment in asthmatic subjects.

Detection of A-to-I RNA Editing in SARS-COV-2.

ADAR1-mediated deamination of adenosines in long double-stranded RNAs plays an important role in modulating the innate immune response. However, recent investigations based on metatranscriptomic samples of COVID-19 patients and SARS-COV-2-infected Vero cells have recovered contrasting findings. Using RNAseq data from time course experiments of infected human cell lines and transcriptome data from Vero cells and clinical samples, we prove that A-to-G changes observed in SARS-COV-2 genomes represent genuine RNA editing events, likely mediated by ADAR1. While the A-to-I editing rate is generally low, changes are distributed along the entire viral genome, are overrepresented in exonic regions, and are (in the majority of cases) nonsynonymous. The impact of RNA editing on virus-host interactions could be relevant to identify potential targets for therapeutic interventions.

SARS-CoV-2 N Protein Targets TRIM25-Mediated RIG-I Activation to Suppress Innate Immunity.

A weak production of INF-ß along with an exacerbated release of pro-inflammatory cytokines have been reported during infection by the novel SARS-CoV-2 virus. SARS-CoV-2 encodes several proteins able to counteract the host immune system, which is believed to be one of the most important features contributing to the viral pathogenesis and development of a severe clinical picture. Previous reports have demonstrated that SARS-CoV-2 N protein, along with some non-structural and accessory proteins, efficiently suppresses INF-ß production by interacting with RIG-I, an important pattern recognition receptor (PRR) involved in the recognition of pathogen-derived molecules. In the present study, we better characterized the mechanism by which the SARS-CoV-2 N counteracts INF-ß secretion and affects RIG-I signaling pathways. In detail, when the N protein was ectopically expressed, we noted a marked decrease in TRIM25-mediated RIG-I activation. The capability of the N protein to bind to, and probably mask, TRIM25 could be the consequence of its antagonistic activity. Furthermore, this interaction occurred at the SPRY domain of TRIM25, harboring the RNA-binding activity necessary for TRIM25 self-activation. Here, we describe new findings regarding the interplay between SARS-CoV-2 and the IFN system, filling some gaps for a better understanding of the molecular mechanisms affecting the innate immune response in COVID-19.

Transglutaminase 2 Regulates Innate Immunity by Modulating the STING/TBK1/IRF3 Axis.

We have recently shown that type 2 transglutaminase (TG2) plays a key role in the host's inflammatory response during bacterial infections. In this study, we investigated whether the enzyme is involved in the regulation of the STING pathway, which is the main signaling activated in the presence of both self- and pathogen DNA in the cytoplasm, leading to type I IFN (IFN I) production. In this study, we demonstrated that TG2 negatively regulates STING signaling by impairing IRF3 phosphorylation in bone marrow-derived macrophages, isolated from wild-type and TG2 knockout mice. In the absence of TG2, we found an increase in the IFN-ß production and in the downstream JAK/STAT pathway activation. Interestingly, proteomic analysis revealed that TG2 interacts with TBK1, affecting its interactome composition. Indeed, TG2 ablation facilitates the TBK1-IRF3 interaction, thus indicating that the enzyme plays a negative regulatory effect on IRF3 recruitment in the STING/TBK1 complex. In keeping with these findings, we observed an increase in the IFNß production in bronchoalveolar lavage fluids from COVID-19-positive dead patients paralleled by a dramatic decrease of the TG2 expression in the lung pneumocytes. Taken together, these results suggest that TG2 plays a negative regulation on the IFN-ß production associated with the innate immunity response to the cytosolic presence of both self- and pathogen DNA.

Immunotherapies and COVID-19 related Neurological manifestations: A Comprehensive Review Article.

In December 2019, an outbreak of pandemic severe respiratory distress syndrome coronavirus disease 2019 (COVID-19) initially occurred in China, has spread the world resulted in serious threats to human public health. Uncommon neurological manifestations with pathophysiological symptoms were observed in infected patients including headache, seizures, and neuroimmunological disorders. Regardless of whether these neurological symptoms are direct or indirect casual infection relationship, this novel viral infection has a relevant impact on the neuroimmune system that requires a neurologist's careful assessment. Recently, the use of immunotherapy has been emerged in fighting against COVID-19 infection despite the uncertain efficiency in managing COVID-19 related disorders or even its proven failure by increasing its severity. Herein, the author is addressing the first approaches in using immunotherapies in controlling COVID-19 viral impact on the brain by highlighting their role in decreasing or increasing infection risks among subjects. This point of view review article supports the use of immunotherapies in managing COVID-19 neurological disorders but in optimal timing and duration to ensure the maximum therapeutic outcome by reducing morbidity and mortality rate. Based on recently published data, the current review article highlights the beneficial effects and drawbacks of using immunotherapies to combat COVID-19 and its neurological symptoms.

Inhibition of anti-viral stress granule formation by coronavirus endoribonuclease nsp15 ensures efficient virus replication.

Cytoplasmic stress granules (SGs) are generally triggered by stress-induced translation arrest for storing mRNAs. Recently, it has been shown that SGs exert anti-viral functions due to their involvement in protein synthesis shut off and recruitment of innate immune signaling intermediates. The largest RNA viruses, coronaviruses, impose great threat to public safety and animal health; however, the significance of SGs in coronavirus infection is largely unknown. Infectious Bronchitis Virus (IBV) is the first identified coronavirus in 1930s and has been prevalent in poultry farm for many years. In this study, we provided evidence that IBV overcomes the host antiviral response by inhibiting SGs formation via the virus-encoded endoribonuclease nsp15. By immunofluorescence analysis, we observed that IBV infection not only did not trigger SGs formation in approximately 80% of the infected cells, but also impaired the formation of SGs triggered by heat shock, sodium arsenite, or NaCl stimuli. We further demonstrated that the intrinsic endoribonuclease activity of nsp15 was responsible for the interference of SGs formation. In fact, nsp15-defective recombinant IBV (rIBV-nsp15-H238A) greatly induced the formation of SGs, along with accumulation of dsRNA and activation of PKR, whereas wild type IBV failed to do so. Consequently, infection with rIBV-nsp15-H238A strongly triggered transcription of IFN-ß which in turn greatly affected rIBV-nsp15-H238A replication. Further analysis showed that SGs function as an antiviral hub, as demonstrated by the attenuated IRF3-IFN response and increased production of IBV in SG-defective cells. Additional evidence includes the aggregation of pattern recognition receptors (PRRs) and signaling intermediates to the IBV-induced SGs. Collectively, our data demonstrate that the endoribonuclease nsp15 of IBV interferes with the formation of antiviral hub SGs by regulating the accumulation of viral dsRNA and by antagonizing the activation of PKR, eventually ensuring productive virus replication. We further demonstrated that nsp15s from PEDV, TGEV, SARS-CoV, and SARS-CoV-2 harbor the conserved function to interfere with the formation of chemically-induced SGs. Thus, we speculate that coronaviruses employ similar nsp15-mediated mechanisms to antagonize the host anti-viral SGs formation to ensure efficient virus replication.

Asymptomatic SARS-CoV-2 infection: is it all about being refractile to innate immune sensing of viral spare-parts?-Clues from exotic animal reservoirs.

A vast proportion of coronavirus disease 2019 (COVID-19) individuals remain asymptomatic and can shed severe acute respiratory syndrome (SARS-CoV) type 2 virus to transmit the infection, which also explains the exponential increase in the number of COVID-19 cases globally. Furthermore, the rate of recovery from clinical COVID-19 in certain pockets of the globe is surprisingly high. Based on published reports and available literature, here, we speculated a few immunovirological mechanisms as to why a vast majority of individuals remain asymptomatic similar to exotic animal (bats and pangolins) reservoirs that remain refractile to disease development despite carrying a huge load of diverse insidious viral species, and whether such evolutionary advantage would unveil therapeutic strategies against COVID-19 infection in humans. Understanding the unique mechanisms that exotic animal species employ to achieve viral control, as well as inflammatory regulation, appears to hold key clues to the development of therapeutic versatility against COVID-19.

Porcine haemagglutinating encephalomyelitis virus deactivates transcription factor IRF3 and limits type I interferon production.

Porcine haemagglutinating encephalomyelitis virus (PHEV) is a member of coronavirus that causes acute infectious disease and high mortality in piglets. The transcription factor IRF3 is a central regulator of type I interferon (IFN) innate immune signalling. Here, we report that PHEV infection of RAW264.7 cells results in strong suppression of IFN-ß production in the early stage. A comparative analysis of the upstream effector of IFN-ß transcription demonstrated that deactivation of IRF3, but not p65 or ATF-2 proteins, is uniquely attributed to failure of early IFN-ß induction. Moreover, the RIG-I/MDA5/MAVS/TBK1-dependent protective response that regulates the IRF3 pathway is not disrupted by PHEV and works well underlying the deactivated IRF3-mediated IFN-ß inhibition. After challenge with poly(I:C), a synthetic analogue of dsRNA used to stimulate IFN-ß secretion in the TLR-controlled pathway, we show that PHEV and poly(I:C) regulate IFN-ß-induction via two different pathways. Collectively, our findings reveal that deactivation of IRF3 is a specific mechanism that contributes to termination of type I IFN signalling during early infection with PHEV independent of the conserved RIG-I/MAVS/MDA5/TBK1-mediated innate immune response.

The ORF6, ORF8 and nucleocapsid proteins of SARS-CoV-2 inhibit type I interferon signaling pathway.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel human coronavirus causing the pandemic of severe pneumonia (Coronavirus Disease 2019, COVID-19). SARS-CoV-2 is highly pathogenic in human, having posed immeasurable public health challenges to the world. Innate immune response is critical for the host defense against viral infection and the dysregulation of the host innate immune responses probably aggravates SARS-CoV-2 infection, contributing to the high morbidity and lethality of COVID-19. It has been reported that some coronavirus proteins play an important role in modulating innate immunity of the host, but few studies have been conducted on SARS-CoV-2. In this study, we screened the viral proteins of SARS-CoV-2 and found that the viral ORF6, ORF8 and nucleocapsid proteins were potential inhibitors of type I interferon signaling pathway, a key component for antiviral response of host innate immune. All the three proteins showed strong inhibition on type I interferon (IFN-ß) and NF-κB-responsive promoter, further examination revealed that these proteins were able to inhibit the interferon-stimulated response element (ISRE) after infection with Sendai virus, while only ORF6 and ORF8 proteins were able to inhibit the ISRE after treatment with interferon beta. These findings would be helpful for the further study of the detailed signaling pathway and unveil the key molecular player that may be targeted.