The twenty-first century has already recorded more than ten major epidemics or pandemics of viral disease, including the devastating COVID-19. Novel effective antivirals with broad-spectrum coverage are urgently needed. Herein, we reported a novel broad-spectrum antiviral compound PAC5. Oral administration of PAC5 eliminated HBV cccDNA and reduced the large antigen load in distinct mouse models of HBV infection. Strikingly, oral administration of PAC5 in a hamster model of SARS-CoV-2 omicron (BA.1) infection significantly decreases viral loads and attenuates lung inflammation. Mechanistically, PAC5 binds to a pocket near Asp49 in the RNA recognition motif of hnRNPA2B1. PAC5-bound hnRNPA2B1 is extensively activated and translocated to the cytoplasm where it initiates the TBK1-IRF3 pathway, leading to the production of type I IFNs with antiviral activity. Our results indicate that PAC5 is a novel small-molecule agonist of hnRNPA2B1, which may have a role in dealing with emerging infectious diseases now and in the future.
Animals ; Mice ; Antiviral Agents/pharmacology* ; COVID-19 ; Hepatitis B virus ; Interferon Type I/metabolism* ; SARS-CoV-2/drug effects* ; Heterogeneous-Nuclear Ribonucleoprotein Group A-B/antagonists & inhibitors*

Type I interferon (IFN) is considered as a bridge between innate and adaptive immunity. Proper activation or inhibition of type I IFN signaling is essential for host defense against pathogen invasion, tumor cell proliferation, and overactive immune responses. Due to intricate and diverse chemical structures, natural products and their derivatives have become an invaluable source inspiring innovative drug discovery. In addition, some natural products have been applied in clinical practice for infection, cancer, and autoimmunity over thousands of years and their promising curative effects and safety have been well-accepted. However, whether these natural products are primarily targeting type I IFN signaling and specific molecular targets involved are not fully elucidated. In the current review, we thoroughly summarize recent advances in the pharmacology researches of natural products for their type I IFN activity, including both agonism/activation and antagonism/inhibition, and their potential application as therapies. Furthermore, the source and chemical nature of natural products with type I IFN activity are highlighted and their specific molecular targets in the type I IFN pathway and mode of action are classified. In conclusion, natural products possessing type I IFN activity represent promising therapeutic strategies and have a bright prospect in the treatment of infection, cancer, and autoimmune diseases.
Biological Products/therapeutic use* ; Immunity, Innate ; Signal Transduction ; Interferon Type I/metabolism*

In order to study the signal pathway secreting type Ⅰ interferon in porcine alveolar macrophages (PAMs) infected with porcine circovirus type 2 (PCV2), the protein and the mRNA expression levels of cGAS/STING pathways were analyzed by ELISA, Western blotting and quantitative reverse transcriptase PCR in PAMs infected with PCV2. In addition, the roles of cGAS, STING, TBK1 and NF-κB/P65 in the generation of type I interferon (IFN-I) from PAMs were analyzed by using the cGAS and STING specific siRNA, inhibitors BX795 and BAY 11-7082. The results showed that the expression levels of IFN-I increased significantly at 48 h after infection with PCV2 (P<0.05), the mRNA expression levels of cGAS increased significantly at 48 h and 72 h after infection (P<0.01), the mRNA expression levels of STING increased significantly at 72 h after infection (P<0.01), and the mRNA expression levels of TBK1 and IRF3 increased at 48 h after infection (P<0.01). The protein expression levels of STING, TBK1 and IRF3 in PAMs infected with PCV2 were increased, the content of NF-κB/p65 was decreased, and the nuclear entry of NF-κB/p65 and IRF3 was promoted. After knocking down cGAS or STING expression by siRNA, the expression level of IFN-I was significantly decreased after PCV2 infection for 48 h (P<0.01). BX795 and BAY 11-7082 inhibitors were used to inhibit the expression of IRF3 and NF-κB, the concentration of IFN-I in BX795-treated group was significantly reduced than that of the PCV2 group (P<0.01), while no significant difference was observed between the BAY 11-7028 group and the PCV2 group. The results showed that PAMs infected with PCV2 induced IFN-I secretion through the cGAS/STING/TBK1/IRF3 signaling pathway.
Animals ; Cells, Cultured ; Circovirus ; Interferon Type I/genetics* ; Macrophages, Alveolar/virology* ; Membrane Proteins/metabolism* ; Nucleotidyltransferases/metabolism* ; Signal Transduction ; Swine

Virus infection induces the production of type I interferons (IFNs). IFNs bind to their heterodimeric receptors to initiate downstream cascade of signaling, leading to the up-regulation of interferon-stimulated genes (ISGs). ISGs play very important roles in innate immunity through a variety of mechanisms. Although hundreds of ISGs have been identified, it is commonly recognized that more ISGs await to be discovered. The aim of this study was to identify new ISGs and to probe their roles in regulating virus-induced type I IFN production. We used consensus interferon (Con-IFN), an artificial alpha IFN that was shown to be more potent than naturally existing type I IFN, to treat three human immune cell lines, CEM, U937 and Daudi cells. Microarray analysis was employed to identify those genes whose expressions were up-regulated. Six hundred and seventeen genes were up-regulated more than 3-fold. Out of these 617 genes, 138 were not previously reported as ISGs and thus were further pursued. Validation of these 138 genes using quantitative reverse transcription PCR (qRT-PCR) confirmed 91 genes. We screened 89 genes for those involved in Sendai virus (SeV)-induced IFN-β promoter activation, and PIM1 was identified as one whose expression inhibited SeV-mediated IFN-β activation. We provide evidence indicating that PIM1 specifically inhibits RIG-I- and MDA5-mediated IFN-β signaling. Our results expand the ISG library and identify PIM1 as an ISG that participates in the regulation of virus-induced type I interferon production.
Cells, Cultured ; Gene Library ; Humans ; Interferon Type I ; metabolism ; Interferon-beta ; genetics ; metabolism ; Proto-Oncogene Proteins c-pim-1 ; genetics ; Up-Regulation

Dendritic Cells ; cytology ; metabolism ; Enzyme-Linked Immunosorbent Assay ; HEK293 Cells ; Humans ; Interferon Regulatory Factor-7 ; metabolism ; Interferon Type I ; metabolism ; Interferon-gamma ; analysis ; Interleukin-6 ; analysis ; Oligonucleotides ; metabolism ; RNA Interference ; RNA, Small Interfering ; metabolism ; Real-Time Polymerase Chain Reaction ; Receptors, Tumor Necrosis Factor ; antagonists & inhibitors ; genetics ; metabolism

The host takes use of pattern recognition receptors (PRRs) to defend against pathogen invasion or cellular damage. Among microorganism-associated molecular patterns detected by host PRRs, nucleic acids derived from bacteria or viruses are tightly supervised, providing a fundamental mechanism of host defense. Pathogenic DNAs are supposed to be detected by DNA sensors that induce the activation of NFκB or TBK1-IRF3 pathway. DNA sensor cGAS is widely expressed in innate immune cells and is a key sensor of invading DNAs in several cell types. cGAS binds to DNA, followed by a conformational change that allows the synthesis of cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) from adenosine triphosphate and guanosine triphosphate. cGAMP is a strong activator of STING that can activate IRF3 and subsequent type I interferon production. Here we describe recent progresses in DNA sensors especially cGAS in the innate immune responses against pathogenic DNAs.
DNA, Bacterial ; immunology ; metabolism ; DNA, Viral ; immunology ; metabolism ; Gene Expression Regulation ; Host-Pathogen Interactions ; Humans ; Immunity, Innate ; Interferon Regulatory Factor-3 ; genetics ; immunology ; Interferon Type I ; biosynthesis ; immunology ; Membrane Proteins ; genetics ; immunology ; Models, Molecular ; NF-kappa B ; genetics ; immunology ; Nucleotides, Cyclic ; biosynthesis ; immunology ; Nucleotidyltransferases ; genetics ; immunology ; Protein Binding ; Protein-Serine-Threonine Kinases ; genetics ; immunology ; Signal Transduction

OBJECTIVEThe study was aimed to investigate the inhibitory effect and mechanism of astragaloside IV (ASI) on the activation of microglial cells.

METHODAfter pre-incubated with ASI for 2 h, microglial cells BV-2 were stimulated with interferon-γ (IFN-γ) for 1. 5 h and 24 h, respectively. Secretion of nitric oxide (NO) in the medium was measured by Griess method. Production of tumor necrosis factor alpha (TNF-α) was detected by ELISA approach. Cellular gene expressions of CD11b, TNF-α, interleukin 1β (IL-1β) and induced nitric oxide synthase (iNOS) were examined by quantitative-PCR analysis. Total and phosphorylation of STAT1, IκB and NF-κB was analyzed by Western blot method.

RESULTASI could significantly inhibit the increased secretion of TNF-α and NO from BV-2 cells upon IFN-γ stimulation (P < 0.001). Further study showed that ASI significantly down-regulated gene expression of IL-1β and TNF-α (P < 0.01, P < 0.05) and exhibited a trend to reduce that of iNOS. IFN-γ and ASI have no obvious effect on gene expression of CD11b. Moreover, ASI inhibited the phosphorylation of STAT1, IκB and NF-κB elicited by IFN-γ stimulation.

CONCLUSIONASI could restrain microglial activation through interfering STAT1/IκB/NF-κB signaling pathway, reducing gene expres- sion of IL-1β and TNF-α, and thus inhibiting the production of proinflammatory mediators such as NO and TNF-α.

Animals ; Astragalus Plant ; chemistry ; Drugs, Chinese Herbal ; pharmacology ; I-kappa B Proteins ; genetics ; metabolism ; Interferon-gamma ; genetics ; metabolism ; Mice ; NF-kappa B ; genetics ; metabolism ; Nitric Oxide ; metabolism ; Nitric Oxide Synthase Type II ; genetics ; metabolism ; STAT1 Transcription Factor ; genetics ; metabolism ; Saponins ; pharmacology ; Signal Transduction ; drug effects ; Triterpenes ; pharmacology

Dendritic cells (DCs) comprise two functionally distinct subsets: plasmacytoid DCs (pDCs) and myeloid DCs (mDCs). pDCs are specialized in rapid and massive secretion of type I interferon (IFN-I) in response to nucleic acids through Toll like receptor (TLR)-7 or TLR-9. In this report, we characterized a CD56(+) DC population that express typical pDC markers including CD123 and BDCA2 but produce much less IFN-I comparing with pDCs. In addition, CD56(+) DCs cluster together with mDCs but not pDCs by genome-wide transcriptional profiling. Accordingly, CD56(+) DCs functionally resemble mDCs by producing IL-12 upon TLR4 stimulation and priming naïve T cells without prior activation. These data suggest that the CD56(+) DCs represent a novel mDC subset mixed with some pDC features. A CD4(+)CD56(+) hematological malignancy was classified as blastic plasmacytoid dendritic cell neoplasm (BPDCN) due to its expression of characteristic molecules of pDCs. However, we demonstrated that BPDCN is closer to CD56(+) DCs than pDCs by global gene-expression profiling. Thus, we propose that the CD4(+)CD56(+) neoplasm may be a tumor counterpart of CD56(+) mDCs but not pDCs.
Biomarkers ; metabolism ; CD56 Antigen ; genetics ; immunology ; Cell Lineage ; genetics ; immunology ; Dendritic Cells ; immunology ; metabolism ; pathology ; Gene Expression ; Hematologic Neoplasms ; genetics ; immunology ; pathology ; Humans ; Immunophenotyping ; Interferon Type I ; biosynthesis ; metabolism ; Interleukin-12 ; biosynthesis ; metabolism ; Interleukin-3 Receptor alpha Subunit ; genetics ; immunology ; Lectins, C-Type ; genetics ; immunology ; Membrane Glycoproteins ; genetics ; immunology ; Myeloid Cells ; immunology ; metabolism ; pathology ; Receptors, Immunologic ; genetics ; immunology ; Terminology as Topic ; Toll-Like Receptor 4 ; genetics ; immunology ; Toll-Like Receptor 7 ; genetics ; immunology ; Toll-Like Receptor 9 ; genetics ; immunology

SARS coronavirus (SARS-CoV) develops an antagonistic mechanism by which to evade the antiviral activities of interferon (IFN). Previous studies suggested that SARS-CoV papain-like protease (PLpro) inhibits activation of the IRF3 pathway, which would normally elicit a robust IFN response, but the mechanism(s) used by SARS PLpro to inhibit activation of the IRF3 pathway is not fully known. In this study, we uncovered a novel mechanism that may explain how SARS PLpro efficiently inhibits activation of the IRF3 pathway. We found that expression of the membrane-anchored PLpro domain (PLpro-TM) from SARS-CoV inhibits STING/TBK1/IKKε-mediated activation of type I IFNs and disrupts the phosphorylation and dimerization of IRF3, which are activated by STING and TBK1. Meanwhile, we showed that PLpro-TM physically interacts with TRAF3, TBK1, IKKε, STING, and IRF3, the key components that assemble the STING-TRAF3-TBK1 complex for activation of IFN expression. However, the interaction between the components in STING-TRAF3-TBK1 complex is disrupted by PLpro-TM. Furthermore, SARS PLpro-TM reduces the levels of ubiquitinated forms of RIG-I, STING, TRAF3, TBK1, and IRF3 in the STING-TRAF3-TBK1 complex. These results collectively point to a new mechanism used by SARS-CoV through which PLpro negatively regulates IRF3 activation by interaction with STING-TRAF3-TBK1 complex, yielding a SARS-CoV countermeasure against host innate immunity.
Dimerization ; HEK293 Cells ; Humans ; I-kappa B Kinase ; metabolism ; Interferon Regulatory Factor-3 ; metabolism ; Interferon Type I ; antagonists & inhibitors ; metabolism ; Membrane Proteins ; chemistry ; genetics ; metabolism ; Papain ; metabolism ; Peptide Hydrolases ; chemistry ; metabolism ; Phosphorylation ; Protein Binding ; Protein Structure, Tertiary ; Protein-Serine-Threonine Kinases ; metabolism ; SARS Virus ; enzymology ; Signal Transduction ; TNF Receptor-Associated Factor 3 ; metabolism ; Ubiquitination

As the first line of immune defense for Mycobacterium tuberculosis (Mtb), macrophages also provide a major habitat for Mtb to reside in the host for years. The battles between Mtb and macrophages have been constant since ancient times. Triggered upon Mtb infection, multiple cellular pathways in macrophages are activated to initiate a tailored immune response toward the invading pathogen and regulate the cellular fates of the host as well. Toll-like receptors (TLRs) expressed on macrophages can recognize pathogen-associated-molecular patterns (PAMPs) on Mtb and mediate the production of immune-regulatory cytokines such as tumor necrosis factor (TNF) and type I Interferons (IFNs). In addition, Vitamin D receptor (VDR) and Vitamin D-1-hydroxylase are up-regulated in Mtb-infected macrophages, by which Vitamin D participates in innate immune responses. The signaling pathways that involve TNF, type I IFNs and Vitamin D are inter-connected, which play critical roles in the regulation of necroptosis, apoptosis, and autophagy of the infected macrophages. This review article summarizes current knowledge about the interactions between Mtb and macrophages, focusing on cellular fates of the Mtb-infected macrophages and the regulatory molecules and cellular pathways involved in those processes.
Animals ; Apoptosis ; Autophagy ; Humans ; Interferon Type I ; metabolism ; Macrophages ; immunology ; metabolism ; Mycobacterium tuberculosis ; physiology ; Receptors, Calcitriol ; metabolism ; Steroid Hydroxylases ; metabolism ; Toll-Like Receptors ; metabolism ; Tuberculosis ; immunology ; metabolism ; pathology ; Tumor Necrosis Factors ; metabolism