Interferon Stimulation Research Articles

MITA/STING-mediated antiviral immunity and autoimmunity: the evolution, mechanism, and intervention.

Mediator of IRF3 activation (MITA, also known as stimulator of interferon genes (STING) and endoplasmic reticulum interferon stimulator (ERIS)) is an ER-associated protein that senses cellular and bacterium-derived cyclic dinucleotide (CDN), leading to induction of type-I interferons (IFNs) and innate immune responses against viruses and bacteria. Recently, it has become clear that sensing of CDN and induction of autophagy are two evolutionarily conserved functions of MITA, predating its role in mediating type-I IFN induction. Studies have shown that MITA-mediated signaling promotes a number of autoimmune disorders caused by gene mutations in human. Here, we summarize the most recent progress on MITA-mediated signaling in a view of evolution and highlight the roles of MITA in human inflammatory disorders caused by gene mutations and in genetically modified mouse models. We also briefly introduce the chemicals targeting MITA and discuss their potential in treatment of MITA-mediated inflammatory diseases. Finally, we propose several key questions that should be addressed for targeting MITA for treatment of related autoimmune diseases.

Post-transcriptional regulatory feedback encodes JAK-STAT signal memory of interferon stimulation.

Immune cells fine tune their responses to infection and inflammatory cues. Here, using live-cell confocal microscopy and mathematical modelling, we investigate interferon-induced JAK-STAT signalling in innate immune macrophages. We demonstrate that transient exposure to IFN-γ stimulation induces a long-term desensitisation of STAT1 signalling and gene expression responses, revealing a dose- and time-dependent regulatory feedback that controls JAK-STAT responses upon re-exposure to stimulus. We show that IFN-α/β1 elicit different level of desensitisation from IFN-γ, where cells refractory to IFN-α/β1 are sensitive to IFN-γ, but not vice versa. We experimentally demonstrate that the underlying feedback mechanism involves regulation of STAT1 phosphorylation but is independent of new mRNA synthesis and cognate receptor expression. A new feedback model of the protein tyrosine phosphatase activity recapitulates experimental data and demonstrates JAK-STAT network’s ability to decode relative changes of dose, timing, and type of temporal interferon stimulation. These findings reveal that STAT desensitisation renders cells with signalling memory of type I and II interferon stimulation, which in the future may improve administration of interferon therapy.

Deciphering the lncRNA and mRNA profiles of Min pig backfat after acute cold stress

ABSTRACT Cold stress can promote fat metabolism and reduce fat deposition. The present study compared differentially expressed (DE) lncRNAs and mRNAs in the subcutaneous back fat of Min pigs subjected to 24 h acute cold stress. Transcriptome sequencing was used to identify DE lncRNAs and mRNAs. A lncRNA mRNA co expression network was constructed using the confirmed lncRNAs. GO and KEGG analyses were performed to investigate the biological processes involved in the response to acute cold stress. A total of 166 DE lncRNAs and 269 DE mRNAs were found. Several genes such as ANGPTL4, KLF11 and NUPR1 were related to lipid metabolism. Interferon stimulating genes (ISGS) such as RSAD2, ISG20, ISG15, DDX60, MX2, MX1 and IFI6 were all significantly up-regulated. In addition, genes related to blood flow, respiration, and oxidative stress were also up-regulated. Many terms related to defense response to a virus were found in the GO annotation. A lncRNA mRNA co expression network comprising 46 specific mRNAs and the top 10 up-regulated DE lncRNAs was constructed. According to the results, the interaction between lncRNAs and mRNAs was complex. This study provides genome-wide gene and lncRNA expression profiles in adipose tissue of pigs after acute cold stress.

Activation mechanisms of monocytes/macrophages in adult-onset Still disease.

Adult onset Still disease (AOSD) is a systemic inflammatory disorder characterized by skin rash, spiking fever, arthritis, sore throat, lymphadenopathy, and hepatosplenomegaly. Although the etiology of this disease has not been fully clarified, both innate and acquired immune responses could contribute to its pathogenesis. Hyperactivation of macrophages and neutrophils along with low activation of natural killer (NK) cells in innate immunity, as well as hyperactivation of Th1 and Th17 cells, whereas low activation of regulatory T cells (Tregs) in acquired immunity are involved in the pathogenic process of AOSD. In innate immunity, activation of monocytes/macrophages might play central roles in the development of AOSD and macrophage activation syndrome (MAS), a severe life-threating complication of AOSD. Regarding the activation mechanisms of monocytes/macrophages in AOSD, in addition to type II interferon (IFN) stimulation, several pathways have recently been identified, such as the pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs)-pattern recognition receptors (PRRs) axis, and neutrophil extracellular traps (NETs)-DNA. These stimulations on monocytes/macrophages cause activation of the nucleotide-binding oligomerization domain, leucine-rich repeat, and pyrin domain (NLRP) 3 inflammasomes, which trigger capase-1 activation, resulting in conversion of pro-IL-1β and pro-IL-18 into mature forms. Thereafter, IL-1β and IL-18 produced by activated monocytes/macrophages contribute to various clinical features in AOSD. We identified placenta-specific 8 (PLAC8) as a specifically increased molecule in monocytes of active AOSD, which correlated with serum levels of CRP, ferritin, IL-1β, and IL-18. Interestingly, PLAC8 could suppress the synthesis of pro-IL-1β and pro-IL-18 via enhanced autophagy; thus, PLAC8 seems to be a regulatory molecule in AOSD. These findings for the activation mechanisms of monocytes/macrophages could shed light on the pathogenesis and development of a novel therapeutic strategy for AOSD.

Aberrant signaling of immune cells in Sjögren's syndrome patient subgroups upon interferon stimulation.

BackgroundPrimary Sjögren’s syndrome (pSS) is a systemic autoimmune disease, characterized by mononuclear cell infiltrates in the salivary and lacrimal glands, leading to glandular atrophy and dryness. Patient heterogeneity and lack of knowledge regarding its pathogenesis makes pSS a difficult disease to manage.MethodsAn exploratory analysis using mass cytometry was conducted of MAPK/ERK and JAK/STAT signaling pathways in peripheral blood mononuclear cells (PBMC) from 16 female medication free pSS patients (8 anti-Sjögren’s syndrome-related antigen A negative/SSA- and 8 SSA+) and 8 female age-matched healthy donors after stimulation with interferons (IFNs).ResultsWe found significant differences in the frequencies of memory B cells, CD8+ T central and effector memory cells and terminally differentiated CD4+ T cells among the healthy donors and patient subgroups. In addition, we observed an upregulation of HLA-DR and CD38 in many cell subsets in the patients. Upon IFNα2b stimulation, slightly increased signaling through pSTAT1 Y701 was observed in most cell types in pSS patients compared to controls, while phosphorylation of STAT3 Y705 and STAT5 Y694 were slightly reduced. IFNγ stimulation resulted in significantly increased pSTAT1 Y701 induction in conventional dendritic cells (cDCs) and classical and non-classical monocytes in the patients. Most of the observed differences were more prominent in the SSA+ subgroup, indicating greater disease severity in them.ConclusionsAugmented activation status of certain cell types along with potentiated pSTAT1 Y701 signaling and reduced pSTAT3 Y705 and pSTAT5 Y694 induction may predispose pSS patients, especially the SSA+ subgroup, to upregulated expression of IFN-induced genes and production of autoantibodies. These patients may benefit from therapies targeting these pathways.

Low-dose exposure to PBDE disrupts genomic integrity and innate immunity in mammary tissue.

The low-dose mixture hypothesis of carcinogenesis proposes that exposure to an environmental chemical that is not individually oncogenic may nonetheless be capable of enabling carcinogenesis when it acts in concert with other factors. A class of ubiquitous environmental chemicals that are hypothesized to potentially function in this low-dose capacity are synthesized polybrominated diphenyl ethers (PBDEs). PBDEs can affect correlates of carcinogenesis that include genomic instability and inflammation. However, the effect of low-dose PBDE exposure on such correlates in mammary tissue has not been examined. In the present study, low-dose long-term (16 weeks) administration of PBDE to mice modulated transcriptomic indicators of genomic integrity and innate immunity in normal mammary tissue. PBDE increased transcriptome signatures for the Nuclear Factor Erythroid 2 Like 2 (NFE2L2) response to oxidative stress and decreased signatures for non-homologous end joining DNA repair (NHEJ). PBDE also decreased transcriptome signatures for the cyclic GMP-AMP Synthase - Stimulator of Interferon Genes (cGAS-STING) response, decreased indication of Interferon Stimulated Gene Factor 3 (ISGF3) and Nuclear Factor Kappa B (NF-κB) transcription factor activity, and increased digital cytometry estimates of immature dendritic cells (DCs) in mammary tissue. Replication of the PBDE exposure protocol in mice susceptible to mammary carcinogenesis resulted in greater tumor development. The results support the notion that ongoing exposure to low levels of PBDE can disrupt facets of genomic integrity and innate immunity in mammary tissue. Such effects affirm that synthesized PBDEs are a class of environmental chemicals that reasonably fit the low-dose mixture hypothesis.

Sterilization of Drug‐Resistant Influenza Virus through Genetic Interference Inspired by Unnatural Amino Acid‐Engineered Particles

AbstractThe frequent emergence of drug resistance during the treatment of influenza A virus (IAV) infections highlights a need for effective antiviral countermeasures. Here, this work presents an antiviral method that utilizes unnatural amino acid‐engineered drug‐resistant (UAA‐DR) virus generated through genetic code expansion to combat emerging drug‐resistant viruses through genomic segment reassortment to produce sterilized progenies due to artificial amber codons in the viral genome. This work validates in vitro that UAA‐DR can provide a broad‐spectrum antiviral strategy for several H1N1 strains, different DR‐IAV strains, multidrug‐resistant (MDR) strains, and even antigenically distant influenza strains (e.g., H3N2). Moreover, a minimum dose of neuraminidase (NA) inhibitors for influenza virus can further enhance the sterilizing effect when combating inhibitor‐resistant strains, partly due to the promoted superinfection of unnatural amino acid‐modified virus in cellular and animal models. The fact that the antiviral effect of UAA‐DR virus cannot be attributed to interferon stimulation and interferon stimulating genes is also investigated. It is anticipated that UAA‐engineered virus‐like particle can be extended to combat emerging drug‐resistant influenza virus and other segmented RNA viruses.

STING expression is an independent prognostic factor in patients with mycosis fungoides

Mycosis fungoides is recognized as an indolent cutaneous malignant T-cell lymphoma. In contrast, there are few therapeutic options for advanced forms of mycosis fungoides. Since immunotherapy is desirable as an alternative therapeutic option, identifying candidate molecules is an important goal for clinicians. Although tumor-derived negative immunomodulatory molecules, such as PD-1/PD-L1, have been identified in various malignancies, the useful positive immunological drivers of mycosis fungoides are largely unknown. We found that the stimulator of interferon (IFN) genes (STING) was highly upregulated in early-stage mycosis fungoides. Immunohistochemical examination revealed different STING staining patterns in patients with mycosis fungoides. Although there were no significant differences in clinical factors’ characteristics, STING expression was associated with the survival of patients with mycosis fungoides. The survival rate was significantly poor in patients with low STING-expressing mycosis fungoides. Univariate and multivariate analyses revealed that low STING expression was associated with an increased hazard ratio. Our results indicate that STING expression independently influences the prognosis of mycosis fungoides.

Resveratrol reduces inflammatory response and detrimental effects in chronic cerebral hypoperfusion by down-regulating stimulator of interferon genes/TANK-binding kinase 1/interferon regulatory factor 3 signaling.

Inflammatory responses induced by chronic cerebral hypoperfusion (CCH) play a critical role in the progression of vascular dementia. Stimulator of interferon genes (STING) signaling function as a key mediator of inflammation and immunological responses in the central nervous system (CNS), and resveratrol (RES) exerts potent anti-inflammatory effects. However, the role of STING signaling and the relationship between RES and STING signaling in persistent hypoperfusion-induced cerebral inflammation remain unclear. In this study, Sprague–Dawley rats were subjected to either Sham or bilateral common carotid artery occlusion (2VO) surgery and received RES or vehicle daily by intraperitoneal injection for 4 or 8 weeks. Morris’s water maze was used for the analysis of cognitive function. The neuroinflammatory responses in white matter and hippocampus of the rat brain were assessed by Western blot, Immunofluorescence staining, and qRT-PCR analyses. Myelin integrity, neutrophil infiltration, and microglia proliferation were assessed by Immunohistochemistry and histologic analysis. We demonstrated that after CCH, neurons, microglia, and astrocyte under endoplasmic reticulum (ER) stress upregulated the expression of STING, TANK-binding kinase 1 (TBK1), and the transcription factor interferon regulatory factor 3 (IRF3), as well as translocation of IRF3 into the nucleus. These were accompanied by infiltration of neutrophils, activation of microglia, and overproduction of proinflammatory mediators. Improvements in cognitive deficits were related to reduced hippocampal neuronal cell death and increased myelin integrity in RES-treated rats. The neuroprotective effects of RES were associated with suppression of the expression of tumor necrosis factor-alpha (TNF-α), intercellular adhesion molecule 1 (ICAM-1), VCAM-1, interferon-β (IFN-β), and IL-1β, likely through mitigation of the STING/TBK1/IRF3 pathway. These inhibitory effects exerted by RES also inhibited the levels of myeloperoxidase, reduced excess expression of reactive astrocytes, and activated microglia. In conclusion, the STING/TBK1/IRF3 axis may be critical for proinflammatory responses in cerebral tissue with persistent hypoperfusion, and RES exerts its anti-inflammatory effects by suppressing STING/TBK1/IRF3 signaling.

Transient upregulation of IRF1 during exit from naive pluripotency confers viral protection

Stem cells intrinsically express a subset of genes which are normally associated with interferon stimulation and the innate immune response. However, the expression of these interferon‐stimulated genes (ISG) in stem cells is independent from external stimuli such as viral infection. Here, we show that the interferon regulatory factor 1, Irf1, is directly controlled by the murine formative pluripotency gene regulatory network and transiently upregulated during the transition from naive to formative pluripotency. IRF1 binds to regulatory regions of a conserved set of ISGs and is required for their faithful expression upon exit from naive pluripotency. We show that in the absence of IRF1, cells exiting the naive pluripotent stem cell state are more susceptible to viral infection. Irf1 therefore acts as a link between the formative pluripotency network, regulation of innate immunity genes, and defense against viral infections during formative pluripotency.

Pharmacological Inhibition of STING/TBK1 Signaling Attenuates Myeloid Fibroblast Activation and Macrophage to Myofibroblast Transition in Renal Fibrosis.

Renal fibrosis is an important pathological biomarker of chronic kidney disease (CKD). Stimulator of interferon genes/TANK binding kinase 1 (STING/TBK1) axis has been identified as the main regulator of innate immune response and closely related to fibrotic disorder. However, the role of STING/TBK1 signaling pathway in kidney fibrosis is still unknown. In this study, we investigated the effect of pharmacological inhibition of STING/TBK1 signaling on renal fibrosis induced by folic acid (FA). In mice, TBK1 was significantly activated in interstitial cells of FA-injured kidneys, which was markedly inhibited by H-151 (a STING inhibitor) treatment. Specifically, pharmacological inhibition of STING impaired bone marrow-derived fibroblasts activation and macrophage to myofibroblast transition in folic acid nephropathy, leading to reduction of extracellular matrix proteins expression, myofibroblasts formation and development of renal fibrosis. Furthermore, pharmacological inhibition of TBK1 by GSK8612 reduced myeloid myofibroblasts accumulation and impeded macrophage to myofibroblast differentiation, resulting in less deposition of extracellular matrix protein and less severe fibrotic lesion in FA-injured kidneys. In cultured mouse bone marrow-derived monocytes, TGF-β1 activated STING/TBK1 signaling. This was abolished by STING or TBK1 inhibitor administration. In addition, GSK8612 treatment decreased levels of α-smooth muscle actin and extracellular matrix proteins and prevents bone marrow-derived macrophages to myofibroblasts transition in vitro. Collectively, our results revealed that STING/TBK1 signaling has a critical role in bone marrow-derived fibroblast activation, macrophages to myofibroblasts transition, and kidney fibrosis progression.

Abnormal lower expression of GPR183 in peripheral blood T and B cell subsets of systemic lupus erythematosus patients

G protein-coupled receptor 183 (GPR183) has been indicated to mediate the migration and localisation of immune cells in T cell-dependent antibody responses. Systemic lupus erythematosus (SLE) is a canonical autoimmune disease involving B cell-mediated tolerance destruction and excessive pathogenic autoantibody production, in which multiple GPCRs play a role. To date, there has been no systematic study regarding the expression of GPR183 in lymphocyte subsets of SLE patients. In this research, firstly, we observed the expression trends of GRP183 in various T and B cell subsets in human tonsil tissues. These lymphocyte subsets include CD4+, CD8+, naïve T, effector T, Tfh, activated Tfh, Th1, Th2, Th17, Treg, CD19+CD27-, CD19+CD27+, naïve B, germinal centre B, memory B, and plasma cells. Further, compared with healthy controls (HCs), GPR183 expression levels in above peripheral blood lymphocyte subsets of patients with SLE were reduced overall. The differential expression of GPR183 expression between inactive and active SLE patients indicates that GPR183 expression may be concerned with the disease activity of SLE. This was further confirmed through the strong negative correlation with SLEDAI score and positive correlation with serum complement protein C3, C4 and C1q levels. Further receiver operating characteristic (ROC) curve analysis revealed that GPR183 expression in circulating CD27-IgD+ B cells may be beneficial in distinguishing between inactive and active SLE patients. In addition, type I interferon stimulation could down-regulate the expression of GPR183 in peripheral blood T and B cell subsets. Aberrant expression of GPR183 may provide some novel insights into disease activity prediction and underlying pathogenesis of SLE.

Alpha-synuclein supports type 1 interferon signalling in neurons and brain tissue.

The protein alpha-synuclein is predominantly expressed in neurons and is associated with neurodegenerative diseases like Parkinson's disease and dementia with Lewy bodies. However, the normal function of alpha-synuclein in neurons is not clearly defined. We have previously shown that mice lacking alpha-synuclein expression exhibit markedly increased viral growth in the brain, increased mortality and increased neuronal cell death, implicating alpha-synuclein in the neuronal innate immune response. To investigate the mechanism of alpha-synuclein-induced immune responses to viral infections in the brain, we challenged alpha-synuclein knockout mice and human alpha-synuclein knockout dopaminergic neurons with RNA virus infection and discovered that alpha-synuclein is required for neuronal expression of interferon-stimulated genes. Furthermore, human alpha-synuclein knockout neurons treated with type 1 interferon failed to induce a broad range of interferon stimulated genes, implying that alpha-synuclein interacts with type 1 interferon signalling. We next found that alpha-synuclein accumulates in the nucleus of interferon-treated human neurons after interferon treatment and we demonstrated that interferon-mediated phosphorylation of STAT2 is dependent on alpha-synuclein expression in human neurons. Next, we found that activated STAT2 co-localizes with alpha-synuclein following type 1 interferon stimulation in neurons. Finally, we found that brain tissue from patients with viral encephalitis expresses increased levels of phospho-serine129 alpha-synuclein in neurons. Taken together, our results show that alpha-synuclein expression supports neuron-specific interferon responses by localizing to the nucleus, supporting STAT2 activation, co-localizing with phosphorylated STAT2 in neurons and supporting expression of interferon-stimulated genes. These data provide a novel mechanism that links interferon activation and alpha-synuclein function in neurons.

A Novel Type I Interferon Primed Dendritic Cell Subpopulation in TREX1 Mutant Chilblain Lupus Patients.

Heterozygous TREX1 mutations are associated with monogenic familial chilblain lupus and represent a risk factor for developing systemic lupus erythematosus. These interferonopathies originate from chronic type I interferon stimulation due to sensing of inadequately accumulating nucleic acids. We here analysed the composition of dendritic cell (DC) subsets, central stimulators of immune responses, in patients with TREX1 deficiency. We performed single-cell RNA-sequencing of peripheral blood DCs and monocytes from two patients with familial chilblain lupus and heterozygous mutations in TREX1 and from controls. Type I interferon pathway genes were strongly upregulated in patients. Cell frequencies of the myeloid and plasmacytoid DC and of monocyte populations in patients and controls were similar, but we describe a novel DC subpopulation highly enriched in patients: a myeloid DC CD1C+ subpopulation characterized by the expression of LMNA, EMP1 and a type I interferon- stimulated gene profile. The presence of this defined subpopulation was confirmed in a second cohort of patients and controls by flow cytometry, also revealing that an increased percentage of patient’s cells in the subcluster express costimulatory molecules. We identified a novel type I interferon responsive myeloid DC subpopulation, that might be important for the perpetuation of TREX1-induced chilblain lupus and other type I interferonopathies.

KAJIAN SENYAWA HEXOSE DAN MALIC ACID SEBAGAI INHIBITOR PAPAIN LIKE PROTEASE (PLPro) CORONA VIRUS

Papain-like protease is a SARSCOV-2 protease that functions for ubiquitination in host cells. Caffeine compounds have been widely reported to have antioxidant, anti-inflammatory, antidiabetic, and antiobesity activities. However, hexose and malic acid compounds in coffee rind as potential inhibitors of the papain-like protease SARSCOV2 have not been reported. This study investigated the potential of malic acid and hexose compounds as PLPro inhibitor agents in inhibiting SARSCOV2 ubiquitination. In silico studies were used to identify the potential of the two compounds by interacting hexose and malic acid compounds with papain-like protease (PLPro) proteins with the Molegro virtual Docker 5 program. Next, the ligand-protein complex visualization was done with discovery studio version 5.0. hexose and malic acid compounds showed interactions with papain-like protease proteins on several active site residues. The interactions showed inhibition of ubiquitination and stimulation of interferon in host cells. The two compound complexes – PLPro protein showed hydrophobic interactions, hydrogen bonds, and van der Waals forces, which contributed to the formation of bond energy and strong bonds between compounds and proteins. In this study, it was concluded that hexose and malic acid compounds have the potential to act as inhibitors of papain-like protease (PLPro) protein.

African swine fever virus MGF505-3R inhibits cGAS-STING-mediated IFN-β pathway activation by degrading TBK1

African swine fever virus (ASFV) is an important pathogen causing acute infectious disease in domestic pigs and wild boars that seriously endangers the global swine industry. As ASFV is structurally complex and encodes a large number of functional proteins, no effective vaccine has been developed to date. Thus, dissecting the mechanisms of immune escape induced by ASFV proteins is crucial. A previous study showed that the ASFV-encoded protein is an important factor in host immunity. In this study, we identified a negative regulator, MGF505-3R, that significantly downregulated cGAS/STING- and poly (dG:dC)-mediated IFN-β and interferon stimulation response element (ISRE) reporter activity and suppressed IFNB1 and IFIT2 mRNA levels. In addition, TBK1, IRF3 and IκBα phosphorylation levels were also inhibited. Mechanistically, MGF505-3R interacted with cGAS/TBK1/IRF3 and targeted TBK1 for degradation, thereby disrupting the cGAS-STING-mediated IFN-β signaling pathway, which appears to be highly correlated with autophagy. Knockdown MGF505-3R expression enhanced IFN-β and IL-1β production. Taken together, our study revealed a negative regulatory mechanism involving the MGF505-3R-cGAS-STING axis and provided insights into an evasion strategy employed by ASFV that involves autophagy and innate signaling pathways.

Classification of PD-L1 expression in various cancers and macrophages based on immunohistocytological analysis.

Programmed death (PD)‐1/PD‐ligand 1 (PD‐L1) antibodies have shown an intense clinical effect in some patients with PD‐L1+ tumors, and their applications have rapidly expanded to various cancer types with or without the application of new companion diagnostics (CDx) with a lower cutoff value and inclusion of macrophage evaluation. However, the pathological background explaining the difference in the cutoff value remains unknown. To address this, we evaluated tissue array samples from 231 patients with lung adenocarcinoma, 186 with lung squamous cell carcinoma, and 38 with renal cell carcinoma (RCC) who were not receiving PD‐1/PD‐L1 antibodies to investigate the relationship between PD‐L1 expression on tumor cells and CD8+ T‐cell infiltration in tumor tissues. PD‐L1 expression in RCC was clearly lower than that in non–small‐cell lung cancer (NSCLC) tissue, whereas CD8+ T‐cell infiltration was low in all cancers. We next analyzed PD‐L1 expression by interferon (α, β, and γ) and LPS stimulation in both macrophages and 41 cancer cell lines derived from various organs and histological types. The PD‐L1 expression patterns were classified into three types, which differed depending on each organ or tissue type. Interestingly, NSCLC cell lines showed highly diverse PD‐L1 expression patterns compared with RCC cell lines. Conversely, PD‐L1 expression was stronger and more prolonged in macrophages than in typical cell lines. Here, we revealed the diversity of the PD‐L1 expression patterns in tumor cells and macrophages, demonstrating the pathological and cytological significance of the transition of cutoff values in PD‐L1 CDx for PD‐1/PD‐L1 antibody administration.

IFN‐α/β‐mediated NK2R expression is related to the malignancy of colon cancer cells

Neurokinin 2 receptor (NK2R), a G protein‐coupled receptor for neurokinin A (NKA), a tachykinin family member, regulates various physiological functions including pain response, relaxation of smooth muscle, dilation of blood vessels, and vascular permeability. However, the precise role and regulation of NK2R expression in cancer cells have not been fully elucidated. In this study, we found that high NK2R gene expression was correlated with the poor survival of colorectal cancer patients, and Interferon (IFN‐α/β) stimulation significantly enhanced NK2R gene expression level of colon cancer cells in a Janus kinas 1/2 (JAK 1/2)‐dependent manner. NKA stimulation augmented viability/proliferation and phosphorylation of Extracellular‐signal‐regulated kinase 1/2 (ERK1/2) levels of IFN‐α/β‐treated colon cancer cells and NK2R blockade by using a selective antagonist reduced the proliferation in vitro. Administration of an NK2R antagonist alone or combined with polyinosinic‐polycytidylic acid, a synthetic analog of double‐stranded RNA, to CT26‐bearing mice significantly suppressed tumorigenesis. NK2R‐overexpressing CT26 cells showed enhanced tumorigenesis and metastatic colonization in both lung and liver after the inoculation into mice. These findings indicate that IFN‐α/β‐mediated NK2R expression is related to the malignancy of colon cancer cells, suggesting that NK2R blockade may be a promising strategy for colon cancers.

Sensing of viral lung infections by cGAS-STING

Lower respiratory tract infections caused over 4 million deaths per year worldwide, especially in low-income countries. Viral respiratory infections often occur as rapidly spreading seasonal endemic or epidemic, and sometimes due to new respiratory viruses including corona viruses. The first level of host defense against viral infection is based on the innate immune system and intracellular killing mechanisms. The latter is activated by the release of viral DNA or RNA into the cytosol of the infected cells during the initial phase of virus replication. Viral DNA and RNA are recognized by the cyclic guanosine monophosphate (cGMP)-adenosine monophosphate (AMP) synthase (cGAS)–stimulator of interferon (IFN) genes (STING) sensing pathway, leading to the activation of type-I and -III IFN synthesis, with the aim to limit viral replication. However, the efficacy of the cGAS-STING sensing mechanism seems to vary with different viruses, and therefore, so is the efficacy of the host defense mechanism. Viral DNA can be sensed by different proteins including DNA-dependent activator of IFN regulating factor (DAI), cGAS, and toll-like receptor-9 (TLR-9). Viral RNA is recognized by retinoid acid-inducible gene 1 (RIG-1), TLR-7 and TLR-8. The question if cGAS also recognizes viral RNA remains unclear. The activation of IFN synthesis by cGAS is initiated by the recognition of purines and pyrimidines and their enzymatic conversion into cGMP and cyclic AMP (cAMP), followed by the activation of STING. In addition, it is indicated that several viruses can evade the cGAS-STING signaling and escape the host defense. This review aims to summarize the role of cGAS-STING as a host defense mechanism against viral respiratory tract infections.

SARS-CoV-2 ORF6 disrupts nucleocytoplasmic trafficking to advance viral replication

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) ORF6 is an antagonist of interferon (IFN)-mediated antiviral signaling, achieved through the prevention of STAT1 nuclear localization. However, the exact mechanism through which ORF6 prevents STAT1 nuclear trafficking remains unclear. Herein, we demonstrate that ORF6 directly binds to STAT1 with or without IFN stimulation, resulting in the nuclear exclusion of STAT1. ORF6 also recognizes importin α subtypes with different modes, in particular, high affinity to importin α1 but a low affinity to importin α5. Although ORF6 potentially disrupts the importin α/importin β1-mediated nuclear transport, thereby suppressing the nuclear translocation of the other classical nuclear localization signal-containing cargo proteins, the inhibitory effect of ORF6 is modest when compared with that of STAT1. The results indicate that the drastic nuclear exclusion of STAT1 is attributed to the specific binding with ORF6, which is a distinct strategy for the importin α1-mediated pathway. Combined with the results from a newly-produced replicon system and a hamster model, we conclude that SARS-CoV-2 ORF6 acts as a virulence factor via regulation of nucleocytoplasmic trafficking to accelerate viral replication, resulting in disease progression.