MxA抗病毒蛋白的研究进展

MxA抗病毒蛋白是由I型干扰素（IFNα／β）诱导产生的分布于细胞质中的蛋白质,具有广谱的抗病毒作用,对多种RNA病毒和部分DNA病毒均有抑制作用。活化的MxA发挥对病毒核衣壳的水解作用,以阻止病毒对细胞的吸附与穿入。MxA基因多态性对不同个体的病毒性疾病发稿、IFN的治疗效果及预后产生重要影响。MxA基因（蛋白）具有极大的临床应用价值和广阔的研究前景。     

聚乙二醇干扰素治疗丙型肝炎

干扰素目前仍是治疗丙型肝炎的主要药物。干扰素是人体内自然产生的一种细胞因子，具有广谱的抗病毒活性。其作用机制一是直接抑制病毒复制，通过激活细胞干扰素受体诱导细胞产生干扰素效应蛋白(如2′，5′-寡腺苷酸合成酶，新喋呤等)而发挥作用；二是通过增强免疫系统的功能而抑制病毒。目前临床用于治疗丙型肝炎的主要是α-干扰     

干扰素在肝炎治疗中的应用

干扰素(IFN)是细胞感染病毒后释放出来的免疫物质，分为Ⅰ型和Ⅱ型，分别由病毒和病毒以外物质诱发。IFN是一类在同种细胞上具有广谱抗病毒活性的蛋白，其活性的发挥受细胞基因组调节和控制。目前用于临床的IFN有α、β、γ三类，分别由病毒诱导白细胞、纤维母细胞、淋巴样细胞产生；多为基因工程DNA重组制备的产品。主要作用为可抑制病毒mRVA信息的传递，阻止病毒在宿主细胞内繁殖；诱导病毒感染的细胞产生蛋白激酶及2，5寡腺苷合成酶，使病毒合成减少，生长受抑制；近年其治疗肝炎的报道较多。     

丙型肝炎抗病毒治疗疗效的影响因素及其机制

丙型肝炎病毒(hepatitis Cvirus,HCV)是引起输血后肝炎及散发性非甲非乙型肝炎的主要病原,目前丙型肝炎抗病毒治疗主要是α干扰素联合利巴韦林,其它抗病毒新药如NS3丝氨酸蛋白酶抑制剂(BILN2061)、NS5B多聚酶抑制剂(JTK-003、JTK-109、NM-283)、利巴韦林类似物(Levovirin,Viramidine)以及一些免疫调节剂等正处于Ⅰ-Ⅲ期临床试验阶段。干扰素是天然存在的细胞蛋白,其功能包括诱导靶细胞的抗病毒状态及细胞因子的分泌、招募免疫细胞、诱导细胞分化等。α干扰素抗病毒作用主要通过二种不同而又互补的机制,一是诱导靶细胞非病毒特异性…     

干扰素在病毒性肝炎治疗中的联合应用

干扰素是细胞在病毒感染或其他诱导因素作用下产生的具有广谱抗病毒、抗肿瘤、抑制细胞增殖和免疫调节作用的细胞因子[1].自1986年应用于临床以来,因其肯定的疗效已被广泛地用于临床治疗多种疾病,在肝脏疾病中的应用目前主要集中在病毒性肝炎的抗病毒治疗,目前应用最广泛的是乙型病毒性肝炎及丙型病毒性肝炎.     

对免疫反应介导的肝细胞损伤机制的新认识

干扰素是细胞在病毒感染或其他诱导因素作用下产生的具有广谱抗病毒、抗肿瘤、抑制细胞增殖和免疫调节作用的细胞因子[1].自1986年应用于临床以来,因其肯定的疗效已被广泛地用于临床治疗多种疾病,在肝脏疾病中的应用目前主要集中在病毒性肝炎的抗病毒治疗,目前应用最广泛的是乙型病毒性肝炎及丙型病毒性肝炎.     

免疫系统在病毒性肝炎肝脏损伤中的作用

在病毒性肝炎疾病中,免疫介导的肝损伤在肝脏损害初期起着主要作用。其介导肝损害的主要机制是细胞介导的细胞毒作用,后者主要通过颗粒胞吐作用和死亡受体两条途径杀伤靶细胞。细胞毒性淋巴细胞作用的时期及与之相关联的其他免疫反应的发生很可能在决定病毒性肝炎急性肝损伤的严重性中起着重要作用。本文就免疫系统在病毒性肝炎肝损伤中的作用及机制研究进展作一介绍。概述在急、慢性病毒性肝炎[1,2]的肝损害的研究中,国内外学者所观察到的炎性浸润和肝细胞损伤的模式强烈表明,免疫系统介导的肝脏损伤是首要机制。大部分肝炎病毒是非致细胞病变性病毒,它们并不直接诱导肝脏损伤,而是通过诱导宿主的细胞病变免疫反应杀伤病毒感染的肝细胞[3-5]。在病毒性肝炎免疫诱导肝损伤疾病中,针对病毒抗原的抗体反应是最易辨认的特征。然而涉及到病毒性肝炎中肝外免疫复合物介导的肝脏疾病时,这些抗体反应在相应肝损伤中的作用并不是十分显著。细胞因子则在针对病毒抗原的天然免疫和特异性免疫中起着重要作用。由于α、β型干扰素可以通过非细胞病变机制介导多种抗病毒效应,因此在急性病毒性肝炎中被视为最大的保护因素,它们可以先于或在细胞毒性T细胞发挥作用的同时降低病毒滴度[2]。其它的...     

HCV感染中的α干扰素抵抗现象

HCV感染病例中有 5 0 %～ 85 %转为慢性。目前慢性丙型肝炎治疗主要基于长效干扰素和病毒唑的联合应用。在这种治疗中 ,2型和 3型感染的病人有 18～ 2 4%不能根除感染 ,1型感染为 5 4%～ 5 8%。HCV对干扰素抵抗 ,例如HCV病毒量消弱干扰素的抗病毒反应从而逃避其作用 ,在急性感染向慢性转化的过程中起一定作用。通过相似或其他的机制 ,干扰素抵抗亦可能在干扰素治疗的病毒学反应中起作用。然而可能的机制尚不清楚 ,新近发现的几种病毒蛋白被证明可在体外通过阻断IFN的抗病毒因子而介导干扰素抵抗 ,但体内的机制是否相同尚未被证实。无论…     

线粒体抗病毒信号蛋白与RNA病毒的相互作用

天然免疫是宿主细胞在生物进化过程中形成的抵御外来侵袭的第一道防线。病毒感染后通过信号转导机制引发机体免疫反应,线粒体抗病毒信号蛋白(MAVS)作为天然免疫信号通路的重要接头蛋白,可以接收上游Toll样受体(TLR)和维甲酸诱导基因I(RIG-I)受体(RLRs)等识别RNA病毒并传递信号,活化下游NF-κB和IRF3/7相关信号通路,从而激活干扰素表达,介导天然免疫相关信号通路。RNA病毒在长期进化过程中针对MAVS也形成了一系列免疫逃逸策略。本综述介绍了MAVS的发现及结构,并对MAVS抗RNA病毒的作用及病毒对MAVS的负调控进行综述,旨在为相关研究提供帮助。     

重组干扰素诱导的跨膜蛋白表达及其对结直肠癌患者的血清学反应

干扰素诱导的跨膜蛋白1（interferon induced transmembrane protein 1，IFITM1）是SEREX方法筛选大肠癌组织cDNA文库时获得的结肠癌相关抗原基因^[1]本研究利用大肠杆菌表达系统重组IFITM1编码蛋白并研究该蛋白对结直肠癌患者血清的抗血清反应。     

IFITM Proteins Inhibit Entry Driven by the MERS-Coronavirus Spike Protein: Evidence for Cholesterol-Independent Mechanisms

The interferon-inducible transmembrane (IFITM) proteins 1, 2 and 3 inhibit the host cell entry of several enveloped viruses, potentially by promoting the accumulation of cholesterol in endosomal compartments. IFITM3 is essential for control of influenza virus infection in mice and humans. In contrast, the role of IFITM proteins in coronavirus infection is less well defined. Employing a retroviral vector system for analysis of coronavirus entry, we investigated the susceptibility of human-adapted and emerging coronaviruses to inhibition by IFITM proteins. We found that entry of the recently emerged Middle East respiratory syndrome coronavirus (MERS-CoV) is sensitive to inhibition by IFITM proteins. In 293T cells, IFITM-mediated inhibition of cellular entry of the emerging MERS- and SARS-CoV was less efficient than blockade of entry of the globally circulating human coronaviruses 229E and NL63. Similar differences were not observed in A549 cells, suggesting that cellular context and/or IFITM expression levels can impact inhibition efficiency. The differential IFITM-sensitivity of coronaviruses observed in 293T cells afforded the opportunity to investigate whether efficiency of entry inhibition by IFITMs and endosomal cholesterol accumulation correlate. No such correlation was observed. Furthermore, entry mediated by the influenza virus hemagglutinin was robustly inhibited by IFITM3 but was insensitive to accumulation of endosomal cholesterol, indicating that modulation of cholesterol synthesis/transport did not account for the antiviral activity of IFITM3. Collectively, these results show that the emerging MERS-CoV is a target of the antiviral activity of IFITM proteins and demonstrate that mechanisms other than accumulation of endosomal cholesterol can contribute to viral entry inhibition by IFITMs.     

IFITMs from Mycobacteria Confer Resistance to Influenza Virus When Expressed in Human Cells

Interferon induced transmembrane proteins (IFITMs) found in vertebrates restrict infections by specific viruses. IFITM3 is known to be essential for restriction of influenza virus infections in both mice and humans. Vertebrate IFITMs are hypothesized to have derived from a horizontal gene transfer from bacteria to a primitive unicellular eukaryote. Since bacterial IFITMs share minimal amino acid identity with human IFITM3, we hypothesized that examination of bacterial IFITMs in human cells would provide insight into the essential characteristics necessary for antiviral activity of IFITMs. We examined IFITMs from Mycobacterium avium and Mycobacterium abscessus for potential antiviral activity. Both of these IFITMs conferred a moderate level of resistance to influenza virus in human cells, identifying them as functional homologues of IFITM3. Analysis of sequence elements shared by bacterial IFITMs and IFITM3 identified two hydrophobic domains, putative S-palmitoylation sites, and conserved phenylalanine residues associated with IFITM3 interactions, which are all necessary for IFITM3 antiviral activity. We observed that, like IFITM3, bacterial IFITMs were S-palmitoylated, albeit to a lesser degree. We also demonstrated the ability of a bacterial IFITM to co-immunoprecipitate with IFITM3 suggesting formation of a complex, and also visualized strong co-localization of bacterial IFITMs with IFITM3. However, the mycobacterial IFITMs lack the endocytic-targeting motif conserved in vertebrate IFITM3. As such, these bacterial proteins, when expressed alone, had diminished colocalization with cathepsin B-positive endolysosomal compartments that are the primary site of IFITM3-dependent influenza virus restriction. Though the precise evolutionary origin of vertebrate IFITMs is not known, our results support a model whereby transfer of a bacterial IFITM gene to eukaryotic cells may have provided a selective advantage against viral infection that was refined through the course of vertebrate evolution to include more robust signals for S-palmitoylation and localization to sites of endocytic virus trafficking.     

Interferon induction of IFITM proteins promotes infection by human coronavirus OC43

IFNs are a family of cytokines that are essential for the antiviral response in vertebrates. Not surprisingly, viruses have adapted to encode virulence factors to cope with the IFN response. Intriguingly, we show here that all three types of interferons, IFN-α, IFN-γ, and IFN-λ, efficiently promote infection by a human coronavirus, HCoV-OC43, one of the major etiological agents of common cold, through the induction of IFN-inducible transmembrane (IFITM) proteins. IFITMs typically exert their antiviral function by inhibiting the entry of a broad spectrum of viruses into their host cells, presumably by trapping and degrading invading virions within the endocytic compartments. In contrast, HCoV-OC43 uses IFN-induced human IFITM2 or IFITM3 as an entry factor to facilitate its infection of host cells. Reverse genetics analyses suggest that the structural motifs critical for the IFITM proteins’ enhancement of HCoV-OC43 infection are distinct from those required for inhibiting infection by other viruses. We also present evidence showing that IFITM family members work as homo- and hetero-oligomers to modulate virus entry. The observed enhancement of HCoV-OC43 infection by IFNs may underlie the propensity of the virus to invade the lower respiratory tract under inflammatory conditions.Coronaviruses (CoVs) are a large family of enveloped, positive-stranded RNA viruses with a broad host range. Six CoVs have been identified thus far as human pathogens (HCoVs) causing either mild upper respiratory tract infections (HCoV-229E, HCoV-OC43, HCoV-NL63, and HCoV-HKU1) or severe acute respiratory syndrome [SARS-CoV and Middle East respiratory syndrome coronavirus (MERS-CoV)] (1, 2). Although regarded as one of the major etiological agents of the common cold, HCoV-OC43 occasionally causes severe infection of upper and lower respiratory tracts in infants and elderly people (3, 4). In our efforts to evaluate the role of inflammatory cytokines in HCoV-OC43 infection and pathogenesis, we found that, unlike other human CoVs that are sensitive to IFN-induced antiviral response (5), HCoV-OC43 infection of cell lines derived from human respiratory tract epithelia and hepatocytes was enhanced drastically not only by IFN-α but also by type II and type III IFNs, i.e., IFN-γ and IFN-λ. Furthermore, we found that this enhancement occurs because HCoV-OC43 uses the IFN-inducible transmembrane (IFITM) proteins to facilitate its entry into host cells.IFITMs are widely expressed IFN-inducible proteins that localize in the membranes of cell plasma and endocytic vesicles and restrict infection by many pathogenic viruses (6–11). Studies by us and by others have revealed that IFITMs do not inhibit viruses from binding to and entering their host cells by endocytosis but instead trap the incoming virions in endocytic compartments, resulting in their degradation (12, 13). Although there is evidence suggesting that IFITMs may inhibit membrane fusion between virions and endosomal membranes, additional mechanisms, such as the disruption of signaling pathways regulating vesicle trafficking and alteration of endosome environments, cannot be excluded (14, 15). In this study, we obtained evidence showing that although the distant N-terminal region of IFITMs is critical for inhibiting influenza A virus (IAV) entry, the sequence-divergent C-terminal region is the critical determinant for IFITM enhancement of HCoV-OC43 infection. Although the detailed molecular mechanisms by which IFITM proteins modulate the entry of the variety of viruses remain to be explored further, the extraordinary ability of HCoV-OC43 to hijack IFITM proteins as its entry factor and to evade other IFN-induced antiviral pathways may play a role in its pathogenesis in humans.     

病毒感染时IFITM3与TRIM22和Foxp3表达及关联基因的富集分析

目的病毒感染时对IFITM3、TRIM22和FOXP3及基因进行富集分析。方法利用STRING作出IFITM3、TRIM22和FOXP3及其关联的50个基因互作网络图;利用DAVID数据库和KOBAS数据库对其进行GO分析和KEGG分析。应用荧光定量PCR对3基因的mRNA相对表达量进行相关性分析。结果通过STRING数据库分析得到3基因互作网络图,关联性大小与图中代表基因节点的圆圈大小呈正比(P<0.05)。经基因功能富集分析表明基因相关的信号通路与基因有关联的可信度较高(P<0.05)。在乙型肝炎病毒、丙型肝炎病毒和甲型流感病毒感染患者的外周血白细胞(P<0.05)分别为(4.462±3.441)、(4.406±4.415)和(4.013±0.081)中的IFITM3的mRNA与健康对照组差异有统计学意义(t=2.987,P<0.01)。结论机体感染病毒后,IFITM3与TRIM22之间、FOXP3与TRIM22之间可能存在着一定的相互作用,并参与机体对病毒感染的应答进程。     

Analysis of in vivo dynamics of influenza virus infection in mice using a GFP reporter virus

Influenza A virus is being extensively studied because of its major impact on human and animal health. However, the dynamics of influenza virus infection and the cell types infected in vivo are poorly understood. These characteristics are challenging to determine, partly because there is no efficient replication-competent virus expressing an easily traceable reporter gene. Here, we report the generation of a recombinant influenza virus carrying a GFP reporter gene in the NS segment (NS1-GFP virus). Although attenuated when compared with wild-type virus, the NS1-GFP virus replicates efficiently in murine lungs and shows pathogenicity in mice. Using whole-organ imaging and flow cytometry, we have tracked the dynamics of influenza virus infection progression in mice. Imaging of murine lungs shows that infection starts in the respiratory tract in areas close to large conducting airways and later spreads to deeper sections of the lungs. In addition to epithelial cells, we found GFP-positive antigen-presenting cells, such as CD11b⁺CD11c⁻, CD11b⁻CD11c⁺, and CD11b⁺CD11c⁺, as early as 24 h after intranasal infection. In addition, a significant proportion of NK and B cells were GFP positive, suggesting active infection of these cells. We next tested the effects of the influenza virus inhibitors oseltamivir and amantadine on the kinetics of in vivo infection progression. Treatment with oseltamivir dramatically reduced influenza infection in all cell types, whereas, surprisingly, amantadine treatment more efficiently blocked infection in B and NK cells. Our results demonstrate high levels of immune cells harboring influenza virus antigen during viral infection and cell-type–specific effects upon treatment with antiviral agents, opening additional avenues of research in the influenza virus field.     

Cellular transcriptional profiling in influenza A virus-infected lung epithelial cells: the role of the nonstructural NS1 protein in the evasion of the host innate defense and its potential contribution to pandemic influenza

The NS1 protein of influenza A virus contributes to viral pathogenesis, primarily by enabling the virus to disarm the host cell type IFN defense system. We examined the downstream effects of NS1 protein expression during influenza A virus infection on global cellular mRNA levels by measuring expression of over 13,000 cellular genes in response to infection with wild-type and mutant viruses in human lung epithelial cells. Influenza A/PR/8/34 virus infection resulted in a significant induction of genes involved in the IFN pathway. Deletion of the viral NS1 gene increased the number and magnitude of expression of cellular genes implicated in the IFN, NF-kappaB, and other antiviral pathways. Interestingly, different IFN-induced genes showed different sensitivities to NS1-mediated inhibition of their expression. A recombinant virus with a C-terminal deletion in its NS1 gene induced an intermediate cellular mRNA expression pattern between wild-type and NS1 knockout viruses. Most significantly, a virus containing the 1918 pandemic NS1 gene was more efficient at blocking the expression of IFN-regulated genes than its parental influenza A/WSN/33 virus. Taken together, our results suggest that the cellular response to influenza A virus infection in human lung cells is significantly influenced by the sequence of the NS1 gene, demonstrating the importance of the NS1 protein in regulating the host cell response triggered by virus infection.     

IFN-stimulated gene 15 functions as a critical antiviral molecule against influenza, herpes, and Sindbis viruses

Type I interferons (IFNs) play an essential role in the host response to viral infection through the induction of numerous IFN-stimulated genes (ISGs), including important antiviral molecules such as PKR, RNase L, Mx, and iNOS. Yet, additional antiviral ISGs likely exist. IFN-stimulated gene 15 (ISG15) is a ubiquitin homolog that is rapidly up-regulated after viral infection, and it conjugates to a wide array of host proteins. Although it has been hypothesized that ISG15 functions as an antiviral molecule, the initial evaluation of ISG15-deficient mice revealed no defects in their responses to vesicular stomatitis virus or lymphocytic choriomeningitis virus, leaving open the important question of whether ISG15 is an antiviral molecule in vivo. Here we demonstrate that ISG15 is critical for the host response to viral infection. ISG15-/- mice are more susceptible to influenza A/WSN/33 and influenza B/Lee/40 virus infections. ISG15-/- mice also exhibited increased susceptibility to both herpes simplex virus type 1 and murine gammaherpesvirus 68 infection and to Sindbis virus infection. The increased susceptibility of ISG15-/- mice to Sindbis virus infection was rescued by expressing wild-type ISG15, but not a mutant form of ISG15 that cannot form conjugates, from the Sindbis virus genome. The demonstration of ISG15 as a novel antiviral molecule with activity against both RNA and DNA viruses provides a target for the development of therapies against important human pathogens.     

Interferon antagonist proteins of influenza and vaccinia viruses are suppressors of RNA silencing

Homology-dependent RNA silencing occurs in many eukaryotic cells. We reported recently that nodaviral infection triggers an RNA silencing-based antiviral response (RSAR) in Drosophila, which is capable of a rapid virus clearance in the absence of expression of a virus-encoded suppressor. Here, we present further evidence to show that the Drosophila RSAR is mediated by the RNA interference (RNAi) pathway, as the viral suppressor of RSAR inhibits experimental RNAi initiated by exogenous double-stranded RNA and RSAR requires the RNAi machinery. We demonstrate that RNAi also functions as a natural antiviral immunity in mosquito cells. We further show that vaccinia virus and human influenza A, B, and C viruses each encode an essential protein that suppresses RSAR in Drosophila. The vaccinia and influenza viral suppressors, E3L and NS1, are distinct double-stranded RNA-binding proteins and essential for pathogenesis by inhibiting the mammalian IFN-regulated innate antiviral response. We found that the double-stranded RNA-binding domain of NS1, implicated in innate immunity suppression, is both essential and sufficient for RSAR suppression. These findings provide evidence that mammalian virus proteins can inhibit RNA silencing, implicating this mechanism as a nucleic acid-based antiviral immunity in mammalian cells.