Alpha-synuclein dynamics bridge Type-I Interferon response and SARS-CoV-2 replication in peripheral cells

BACKGROUND: Increasing evidence suggests a double-faceted role of alpha-synuclein (α-syn) following infection by a variety of viruses, including SARS-CoV-2. Although α-syn accumulation is known to contribute to cell toxicity and the development and/or exacerbation of neuropathological manifestations, it is also a key to sustaining anti-viral innate immunity. Consistently with α-syn aggregation as a hallmark of Parkinson's disease, most studies investigating the biological function of α-syn focused on neural cells, while reports on the role of α-syn in periphery are limited, especially in SARS-CoV-2 infection. RESULTS: Results herein obtained by real time qPCR, immunofluorescence and western blot indicate that α-syn upregulation in peripheral cells occurs as a Type-I Interferon (IFN)-related response against SARS-CoV-2 infection. Noteworthy, this effect mostly involves α-syn multimers, and the dynamic α-syn multimer:monomer ratio. Administration of excess α-syn monomers promoted SARS-CoV-2 replication along with downregulation of IFN-Stimulated Genes (ISGs) in epithelial lung cells, which was associated with reduced α-syn multimers and α-syn multimer:monomer ratio. These effects were prevented by combined administration of IFN-ß, which hindered virus replication and upregulated ISGs, meanwhile increasing both α-syn multimers and α-syn multimer:monomer ratio in the absence of cell toxicity. Finally, in endothelial cells displaying abortive SARS-CoV-2 replication, α-syn multimers, and multimer:monomer ratio were not reduced following exposure to the virus and exogenous α-syn, suggesting that only productive viral infection impairs α-syn multimerization and multimer:monomer equilibrium. CONCLUSIONS: Our study provides novel insights into the biology of α-syn, showing that its dynamic conformations are implicated in the innate immune response against SARS-CoV-2 infection in peripheral cells. In particular, our results suggest that promotion of non-toxic α-syn multimers likely occurs as a Type-I IFN-related biological response which partakes in the suppression of viral replication. Further studies are needed to replicate our findings in neuronal cells as well as animal models, and to ascertain the nature of such α-syn conformations.

Modulation of type I interferon signaling by natural products in the treatment of immune-related diseases / 中国天然药物

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.

A hnRNPA2B1 agonist effectively inhibits HBV and SARS-CoV-2 omicron in vivo

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.

Niveles de Interferón Tipo I en pacientes con Lupus Eritematoso Sistémico / Type I interferon levels in patients with systemic lupus erythematosus

Introducción: El interferón (IFN) tipo I es una citoquina que juega un rol fundamental en la patogenia del Lupus Eritematoso Sistémico (LES). Diferentes niveles de esta citoquina podrían explicar la heterogeneidad de esta patología y ser útil para evaluar la actividad de la misma. Objetivos: Determinar los niveles de IFN tipo I sérico en pacientes con LES y evaluar su utilidad como biomarcador de actividad. Material y Métodos: 16 pacientes con LES (ACR 1997) y 16 controles. Métodos: Actividad de la enfermedad (SLEDAI-2K), daño orgánico (SLICC), IFN tipo I (HEK-Blue-IFNα/β), anticuerpos anti-DNAdc (Inmunofluorescencia Indirecta), anticuerpos anti-ENA (ELISA), C3-C4 (Inmunoturbidimetría). Estadística: InfoStat/Instat/MedCalc. Valores de p<0,05 fueron considerados estadísticamente significativos. Resultados: Se observó un aumento de la concentración de IFN en el grupo LES con respecto al control (p<0,05). Los pacientes con valores de IFN superiores al punto de corte, se asociaron con la presencia de anticuerpos anti-DNAdc (OR:13,33; p<0,05). Pacientes con hipocomplementemia y aquellos con puntaje de SLEDAI-2K mayor a 8 presentaron mayores niveles de IFN comparados con pacientes con complemento normal y menor puntaje de índice, respectivamente (p<0,05). Conclusiones: Estos resultados sugieren la importancia que podría tener la determinación de IFN tipo I para el monitoreo de la actividad del LES.

Introduction: Type I interferon (IFN) is a cytokine that plays a fundamental role in the pathogenesis of Systemic Lupus Erythematosus (SLE). Different levels of this cytokine could explain the heterogeneity of this pathology and be useful to evaluate its activity. Objectives: To determine the serum type I IFN levels in patients with SLE and evaluate its usefulness as a biomarker of activity. Material and Method: 16 patients with SLE (ACR 1997) and 16 controls. Methods: Disease activity (SLEDAI-2K), organ damage (SLICC), type I IFN (HEK-Blue-IFNα/β), anti-dsDNA antibodies (Indirect Immunofluorescence), anti-ENA antibodies (ELISA), C3-C4 (Immunoturbidimetry). Statistics: InfoStat/Instat/MedCalc. P values <0.05 were statistically significant. Results: An increase in IFN concentration was observed in the SLE group respect to the control (p <0.05). Patients with IFN values above the cut-off point were associated with the presence of anti-dsDNA antibodies (OR: 13.33; p<0.05). Hypocomplementemic patients and those with a SLEDAI-2K score greater than 8 had higher IFN levels compared to patients with normal complement and a lower index score, respectively (p<0.05). Conclusions: These results suggest the importance that the determination of IFN type I could have for the monitoring of SLE activity.

Importancia de los interferones tipo I en la respuesta inmune antiviral contra el Virus del Papiloma Humano / Importance of type I interferons in the antiviral immune response against the Human Papillomavirus

Resumen Los interferones (IFNs) son citoquinas fundamentales en la modulación de la inmunidad innata y adaptativa del hospedero, el papel de los IFNs tipo I en el control de la infección por el Virus del Papiloma Humano (VPH) es crucial para una eficiente respuesta antiviral del huésped. Esta revisión profundiza sobre las funciones de los IFNs tipo I en la infección causada por el VPH y los mecanismos de evasión de este virus para inactivar los IFNs tipo I, todos estos mecanismos necesarios para el desarrollo y progresión de lesiones malignas en los tejidos infectados por el VPH.

Abstract The interferons (IFNs) are very important cytokines in the interface between innate and adaptive immunity of the host, the role type I IFNs in the control of HPV is pivotal for an efficient immune response, so a wide knowledge about this topic will contribute understanding HPV pathogenicity mechanism. This review focuses on the HPV evasion mechanisms for the type I IFNs which are necessary for a malignant lesion development, otherwise develops knowledge about the type I IFNs functions on the HPV infection.

Plasmacytoid dendritic cells in dermatology

Abstract Plasmacytoid dendritic cells are part of the dendritic cells family and are a relevant link between innate and adaptive immunity. They are the most potent producers of type 1 interferon, generating antiviral response, stimulating macrophages and dendritic cells and inducing activation and migration of natural killer cells. Plasmacytoid dendritic cells also exert a role as antigen-presenting cells, promote T-lymphocyte responses, immunoregulation, plasma cells differentiation and antibody secretion. Even though plasmacytoid dendritic cells are not usually present in normal skin, their presence is detected in healing processes, viral infections, and inflammatory, autoimmune, and neoplastic diseases. In recent years, the presence of plasmacytoid dendritic cells in several dermatological diseases has been described, enhancing their potential role in the pathogenesis of such conditions. Future studies on the role of plasmacytoid dendritic cells in dermatology may lead to new therapeutic targets.

cGAS/STING signaling pathways induces the secretion of type Ⅰ interferon in porcine alveolar macrophages infected with porcine circovirus type 2 / 生物工程学报

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.

Immune response in SARS-CoV-2 infection: the role of interferons type I and type III

Abstract Background There is scarce information on the human immune response to the SARS-CoV-2 infection, and on the exacerbated inflammatory reaction observed in severe COVID-19 cases. Objective To review the available evidence on the role of interferons type I and type III to SARS-CoV-2 infection. Methods We reviewed the available published evidence on the role of immune response to SARS-CoV-2 infection as well as recent publications on characteristics and outcomes of COVID-19, and their relationship with interferons type I and type III. Results The available data indicates that immune response plays an important role in controlling SARS-CoV-2 infection and the immune dysregulation can significantly modify the clinical outcomes of affected patients. In addition, the evidence suggests that IFN type I and III can play an important role in controlling viremia and modulating the immune response in COVID-19. Conclusions Due to their central role in immune response against SARS-CoV-2 infection, IFN type I and III could be considered for treatment of COVID-19.

Informe diário de evidências COVID-19: busca referente aos dias 11, 12 e 13 de julho de 2020 / COVID-19 daily evidence report: search for July 11, 12 and 13, 2020

O Informe Diário de Evidências é uma produção do Ministério da Saúde que tem como objetivo acompanhar diariamente as publicações científicas sobre tratamento farmacológico e vacinas para a COVID-19. Dessa forma, são realizadas buscas estruturadas em bases de dados biomédicas, referentes ao dia anterior desse informe. Não são incluídos estudos pré-clínicos (in vitro, in vivo, in silico). A frequência dos estudos é demonstrada de acordo com a sua classificação metodológica (revisões sistemáticas, ensaios clínicos randomizados, coortes, entre outros). Para cada estudo é apresentado um resumo com avaliação da qualidade metodológica. Essa avaliação tem por finalidade identificar o grau de certeza/confiança ou o risco de viés de cada estudo. Para tal, são utilizadas ferramentas já validadas e consagradas na literatura científica, na área de saúde baseada em evidências. Cabe ressaltar que o documento tem caráter informativo e não representa uma recomendação oficial do Ministério da Saúde sobre a temática. Foram encontrados 14 artigos.

MALAT1 is involved in type I IFNs-mediated systemic lupus erythematosus by up-regulating OAS2, OAS3, and OASL

Systemic lupus erythematosus (SLE) is an autoimmune disease associated with an aberrant activation of immune cells partly due to the dysfunction of cytokines such as type I interferons (IFNs). Long non-coding RNA MALAT1 has been found to play a pathogenic role in SLE; however, the underlying mechanisms are still poorly understood. Bioinformatics analysis showed the up-regulation of type I IFN downstream effectors OAS2, OAS3, and OASL (OAS-like) in CD4+ T cells, CD19+ B cells, and CD33+ myeloid cells in patients with active SLE compared to healthy participants. In this study, peripheral blood mononuclear cells (PBMCs), CD19+ B, and CD4+ T cells were isolated from active SLE patients and healthy participants. PCR was performed to quantify MALAT1, OAS2, OAS3, and OASL expression in immune cells. MALAT1, OAS2, OAS3, and OASL were knocked down in CD4+ T cells to investigate the regulatory effect of MALAT1 on the effectors and their involvement in type I IFNs-mediated inflammation. Results showed higher OAS2, OAS3, and OASL expression in active SLE patients. MALAT1 expression was positively correlated to OAS2, OAS3, and OASL expression in CD19+ B or CD4+ T cells. MALAT1 knockdown decreased OAS2, OAS3, and OASL expression. Treatment with IFN-α-2a increased the expression of TNF-α, IL-1β, and IFN-α in CD4+ T cells. However, knockdown of MALAT1, OAS2, OAS3, and OASL alone inhibited the effect of IFN-α-2a on TNF-α and IL-1β. This study suggested the involvement of MALAT1 in type I IFNs-mediated SLE by up-regulating OAS2, OAS3, and OASL.

The Role of Plasmacytoid Dendritic Cells in Gut Health

Plasmacytoid dendritic cells (pDCs) are a unique subset of cells with different functional characteristics compared to classical dendritic cells. The pDCs are critical for the production of type I IFN in response to microbial and self-nucleic acids. They have an important role for host defense against viral pathogen infections. In addition, pDCs have been well studied as a critical player for breaking tolerance to self-nucleic acids that induce autoimmune disorders such as systemic lupus erythematosus. However, pDCs have an immunoregulatory role in inducing the immune tolerance by generating Tregs and various regulatory mechanisms in mucosal tissues. Here, we summarize the recent studies of pDCs that focused on the functional characteristics of gut pDCs, including interactions with other immune cells in the gut. Furthermore, the dynamic role of gut pDCs will be investigated with respect to disease status including gut infection, inflammatory bowel disease, and cancers.

Análise do envolvimento do interferon tipo I na imunopatogênese do eritema nodoso hanseniano / Analysis of type I interferro involvement in the immunopathogenesis of erythema nodosum leprosum

A forma multibacilar da hanseníase pode apresentar manifestações inflamatórias agudas, conhecidas como episódios reacionais. Um desses episódios é o eritema nodoso hanseniano (ENH), considerado o quadro clínico mais grave da hanseníase, sendo caracterizado pelo aparecimento abrupto de múltiplas lesões novas, sintomas sistêmicos e agravamento da neuropatia. A talidomida é o fármaco de escolha para o tratamento e tem efeito benéfico num curto período de tempo. Dados recentes do nosso grupo demonstram uma maior expressão de TLR-9, tanto nas lesões como no sangue de pacientes ENH. Uma consequência importante da ativação da via de TLR-9 é a produção de IFN tipo I, especialmente o IFN-α. Essa citocina tem sido implicada na patogênese de várias doenças inflamatórias crônicas com intercorrências agudas, como a psoríase e o lúpus eritematoso sistêmico, contribuindo para uma desregulação da imunidade inata e adquirida e amplificação do processo inflamatório. Baseado nos dados acima citados, este estudo teve como objetivo analizar a participação de IFN-I na patogênese do ENH. Para alcançar este objetivo, amostras de sangue e lesões de pele de pacientes com as formas multibacilares sem reação (grupo LL/BL) e com diagnóstico da reação antes de iniciar o tratamento com talidomida (grupo ENH D0) foram coletadas. Também analisamos amostras clínicas de pacientes ENH após 7 dias de tratamento com talidomida (grupo ENH D7) para avaliar o impacto deste medicamento na via de IFN-I. Foram realizados ensaios de imunofluorescência e PCR em tempo real para investigar, respectivamente, a presença de IFN-α e a expressão de genes de assinatura de IFN-I (EIF2AK2, MX1 e IFIT-1).

Além disso, os níveis da proteína MX1 na lesão cutânea foram analisados através de western blotting. Os resultados de expressão gênica indicam níveis mais elevados de RNAm de EIF2AK2 tanto na lesão cutânea como no sangue de pacientes ENH D0. Já no que se refere aos genes MX1 e IFIT-1 não houve diferença entre os grupos. O tratamento com a talidomida resultou na diminuição da expressão dos genes EIF2AK2 e MX1. Os níveis proteicos de MX1 se mostraram elevados nos pacientes LL/BL e ENH D0, com uma diminuição após o tratamento com a talidomida. Imagens de imunofluorescência sugerem a presença de um maior número de células produtoras de IFN-α nas lesões de pacientes ENH D0 quando comparadas a LL/BL, ocorrendo uma diminuição drástica após 7 dias de tratamento com talidomida. Finalmente, confirmamos que o IFN-α possui a capacidade de induzir a NETose em neutrófilos de indivíduos sadios. Em conjunto esses resultados sugerem o envolvimento do IFN do tipo I na patogênese do ENH, abrindo perspectivas para a identificação de biomarcadores para o diagnóstico precoce do ENH e novos alvos para melhor conduta terapêutica deste episodio reacional. (AU)

Aryl Hydrocarbon Receptor Ligands Indoxyl 3-sulfate and Indole-3-carbinol Inhibit FMS-like Tyrosine Kinase 3 Ligand-induced Bone Marrow-derived plasmacytoid Dendritic Cell Differentiation

Aryl hydrocarbon receptor (AhR) regulates both innate and adaptive immune responses by sensing a variety of small synthetic and natural chemicals, which act as its ligands. AhR, which is expressed in dendritic cells (DCs), regulates the differentiation of DCs. However, effects of AhR on the differentiation of DCs are variable due to the heterogeneity of DCs in cell surface marker expression, anatomical location, and functional responses. The plasmacytoid DCs (pDCs), one of DC subsets, not only induce innate as well as adaptive immune responses by secreting type I interferons and pro-inflammatory cytokines, but also induce IL-10 producing regulatory T cell or anergy or deletion of antigen-specific T cells. We showed here that AhR ligands indoxyl 3-sulfate (I3S) and indole-3-carbinol (I3C) inhibited the development of pDCs derived from bone marrow (BM) precursors induced by FMS-like tyrosine kinase 3 ligand (Flt3L). I3S and I3C downregulated the expression of signal transducer and activator of transcription 3 (STAT3) and E2-2 (Tcf4). In mice orally treated with I3S and I3C, oral tolerance to dinitrofluorobenzene was impaired and the proportion of CD11c⁺B220⁺ cells in mesenteric lymph nodes was reduced. These data demonstrate that AhR negatively regulates the development of pDCs from BM precursors induced by Flt3L, probably via repressing the expression of STAT3.

Direct Antiviral Mechanisms of Interferon-Gamma

Interferon-gamma (IFNG) is a pleiotropic cytokine that modulates both innate and adaptive immune networks; it is the most potent activator of macrophages and a signature cytokine of activated T lymphocytes. Though IFNG is now appreciated to have a multitude of roles in immune modulation and broad-spectrum pathogen defense, it was originally discovered, and named, as a secretory factor that interferes with viral replication. In contrast to the prototypical type I interferons produced by any cells upon viral infection, only specific subsets of immune cells can produce IFNG upon infection or stimulation with antigen or mitogen. Still, virtually all cells can respond to both types of interferons. This makes IFNG a versatile anti-microbial cytokine and also gives it a unique position in the antiviral defense system. The goal of this review is to highlight the direct antiviral mechanisms of IFNG, thereby clarifying its antiviral function in the effective control of viral infections.

Identification of new type I interferon-stimulated genes and investigation of their involvement in IFN-β activation

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.

Interferon-free treatment for hepatitis C virus infection induces normalization of extrahepatic type I interferon signaling

BACKGROUND/AIMS: Hepatitis C virus (HCV) replicates in the peripheral blood mononuclear cells (PBMCs), leading to the production of type I interferons (IFNs). It is well known that the gene expression profile of PBMC is similar to that of the liver. The present study explored the dynamic gene expression profile of PBMCs collected from HCV-infected patients undergoing direct-acting antiviral (DAA) therapy. METHODS: A prospective cohort comprising 27 patients under DAA therapy was formed. Expression level of IFN-β and its downstream interferon-stimulated genes (ISGs) was measured in PBMCs before and after DAA treatment. Furthermore, immunoblotting was performed to identify the signaling molecules involved in the expression of ISGs. RESULTS: The pretreatment expression level of interferon-induced protein 44 (IFI44) and C-X-C motif chemokine ligand 10 (CXCL10) correlated with the pretreatment expression level of IFN-β. After DAA treatment, a significant decrease in the expression levels of IFN-β, IFI44, and CXCL10 was observed in the PBMCs. Furthermore, the pretreatment expression level of IFN-β and ISGs correlated with the level of signal transducer and activator of transcription 1 (STAT1) phosphorylation, and DAA treatment abrogated STAT1 phosphorylation. CONCLUSIONS: Pretreatment activation of IFN-β response is rapidly normalized after DAA treatment. The present study suggests that the decreased type I IFN response by the clearance of HCV might contribute to DAA-induced alleviation of extrahepatic manifestation of chronic HCV infection.

DNA sensor cGAS-mediated immune recognition

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.

Dependence of RIG-I Nucleic Acid-Binding and ATP Hydrolysis on Activation of Type I Interferon Response

Exogenous nucleic acids induce an innate immune response in mammalian host cells through activation of the retinoic acid-inducible gene I (RIG-I). We evaluated RIG-I protein for RNA binding and ATPase stimulation with RNA ligands to investigate the correlation with the extent of immune response through RIG-I activation in cells. RIG-I protein favored blunt-ended, double-stranded RNA (dsRNA) ligands over sticky-ended dsRNA. Moreover, the presence of the 5'-triphosphate (5'-ppp) moiety in dsRNA further enhanced binding affinity to RIG-I. Two structural motifs in RNA, blunt ends in dsRNA and 5'-ppp, stimulated the ATP hydrolysis activity of RIG-I. These structural motifs also strongly induced IFN expression as an innate immune response in cells. Therefore, we suggest that IFN induction through RIG-I activation is mainly determined by structural motifs in dsRNA that increase its affinity for RIG-I protein and stimulate ATPase activity in RIG-I.

Enhanced Viral Replication by Cellular Replicative Senescence

Cellular replicative senescence is a major contributing factor to aging and to the development and progression of aging-associated diseases. In this study, we sought to determine viral replication efficiency of influenza virus (IFV) and Varicella Zoster Virus (VZV) infection in senescent cells. Primary human bronchial epithelial cells (HBE) or human dermal fibroblasts (HDF) were allowed to undergo numbers of passages to induce replicative senescence. Induction of replicative senescence in cells was validated by positive senescence-associated β-galactosidase staining. Increased susceptibility to both IFV and VZV infection was observed in senescent HBE and HDF cells, respectively, resulting in higher numbers of plaque formation, along with the upregulation of major viral antigen expression than that in the non-senescent cells. Interestingly, mRNA fold induction level of virus-induced type I interferon (IFN) was attenuated by senescence, whereas IFN-mediated antiviral effect remained robust and potent in virus-infected senescent cells. Additionally, we show that a longevity-promoting gene, sirtuin 1 (SIRT1), has antiviral role against influenza virus infection. In conclusion, our data indicate that enhanced viral replication by cellular senescence could be due to senescence-mediated reduction of virus-induced type I IFN expression.

Research progress on the role of TANK-binding kinase 1 in anti-virus innate immune response / 浙江大学学报·医学版

The innate immune response against viral infection is mainly relies on type I interferon, the production of which is mediated by TANK-binding kinase 1 (TBK1). It is revealed that the downstream TBK1 is activated by viral nucleic acid sensors RIG-I, cGAS and TLR3. The activity of TBK1 is complexly and precisely regulated by different type of protein modifications, including phosphorylation, ubiquitination and Sumolylation. This article focuses on the role of TBK1 in anti-viral innate immunity and the regulatory mechanism for the TBK1 activation.