丙型肝炎病毒NS3蛋白单克隆杂交瘤细胞株的建立及初步鉴定

应用国产基因工程表达的丙型肝炎病毒（ＨＣＶ）ＮＳ３区抗原免疫小鼠，然后取其脾细胞与小鼠骨髓瘤细胞系ＳＰ２／０融合，筛选出４株稳定分泌抗ＨＣＶＮＳ３区蛋白单克隆抗体（ＭｃＡｂ）的杂交瘤细胞株，分别命名为２Ｂ６，２Ｆ３，３Ｄ８，３Ｄ９，经初步研究表明这４株单抗与ＮＳ３抗原具有良好的反应性，与ＨＣＶ核心区多肽及乙型肝炎病毒表面抗原和ｅ抗原均无反应。抑制实验表明这４株抗体分别针对ＮＳ３抗原分子上的２个不同的抗原决定簇。     

丙型肝炎病毒非结构蛋白NS4A的研究进展

丙型肝炎病毒（ＨＣＶ）的ＮＳ４Ａ蛋白分子由５４个氨基酸残基组成。ＮＳ４Ａ与ＮＳ４Ｂ的结合位点处有一抗原位点结构。ＮＳ４Ａ主要的生物学功能就是作为ＮＳ３丝氨酸蛋白酶的辅助因子,在ＨＣＶ多蛋白的成熟过程中发挥着重要的调节作用。     

52 例病毒性肝炎患者肝组织中丙型肝炎病毒 RNA 和 HCAg-NS3 的测定

应用地高辛标记探针原位杂交法和单克隆抗ＨＣＶ－ＮＳ３－ＨＲＰ建立直接酶标免疫组化法分别测定５２例肝炎患者肝组织ＨＣＶＲＮＡ和ＨＣＡｇ－ＮＳ３。结果抗ＨＣＶ阳性组ＨＣＶＲＮＡ检出率５７．１％（１６／２８），ＨＣＡｇ－ＮＳ３检出率５３．６％（１５／２８）；抗ＨＣＶ阴性组其两项检出率均为１２．５％（３／２４）。肝组织中ＨＣＶＲＮＡ阳性物呈蓝紫色细小颗粒存在于肝细胞核或胞浆内，其在肝小叶中的分布可分为３型，即弥漫型、局灶型、散在型。肝组织中ＨＣＡｇ－ＮＳ３阳性物呈棕黄色细小颗粒分布于肝细胞核或胞浆内，以单个或数个阳性细胞散布于肝小叶中。２３例ＨＣＶＲＮＡ或／和ＨＣＡｇ－ＮＳ３阳性病例以肝炎后肝硬化（ＬＣ）病例占多数（１４／２３），其次为慢性重型肝炎（ＣＳＨ）和中度慢性肝炎（ＣＡＨ）。此两种检测方法具有较高符合率（９０．４％，４７／５２），表明病毒核酸及其表达产物均存在于肝细胞内，与ＨＣＶ感染密切相关。这为ＨＣＶ感染诊断提供了直接依据，有利于研究ＨＣＶ感染中病毒复制、慢性化进程、抗病毒治疗监测及重叠感染时病毒相互关系。     

人原发性肝内胆管细胞癌中HCVRNA及其NS3区抗原的分布及意义

人原发性肝内胆管细胞癌中ＨＣＶＲＮＡ及其ＮＳ３区抗原的分布及意义西安第四军医大学病理学教研室应用原位分子杂交及免疫组化方法，使用地高辛标记ＨＣＶ５＇非编码区探针及抗ＨＣＶＮＳ３区Ｃ３３ｃ单克隆抗体，对３５例人原发性肝内胆管细胞癌（ＰＩＣ）和癌旁肝组织...     

HCV感染后NS5区抗体的动态观察与检测意义

本文报道用ＨＣＶＮＳ５区两段抗原性较好的合成肽研制的ＥＬＩＳＡ试剂盒及ＵＢＩＨＣＶＮＳ５区抗体检测ＥＬＩＳＡ试剂盒观察１４例ＨＣＶ感染者ＮＳ５区抗体的动态变化，证实ＮＳ５区抗体如同ＮＳ４区抗体一样比Ｃ及ＮＳ３区抗体出现晚。ＮＳ５区抗体总体检出率近似于ＮＳ４区抗体；１．５５％的血清为单独ＮＳ５区抗体阳性；存在ＮＳ５区抗体与其他区抗体滴度有互补作用的标本等提示ＮＳ５区抗体仍有一定的诊断价值。采用ＵＢＩＮＳ５区抗体检测试剂盒发现，９５．６５％（２２／２３）ＵＢＩ试剂盒诊断为ＮＳ５区抗体阳性的标本中含ＨＣＶＲＮＡ，６／１４ＨＣｖ感染者用ＵＢＩ试剂盒检出的抗体出现在ＡＬＴ再次异常升高或剧烈升高（高于参考值的３倍以上）前后，４／１４的感染者抗体出现于ＡＬＴ首次升高前后（其余４／１４的感染者未检出抗ＮＳ５抗体），因此ＵＢＩ抗ＨＣＶＮＳ５抗体诊断试剂盒检测的抗体似与疾病的活动有关。     

庚型肝炎病毒NS3蛋白在大肠杆菌中的表达

目的　获取具备免疫反应原性的庚型肝炎病毒ＮＳ３ 抗原。方法　从重组质粒Ｉｗｑ２利用ＰＣＲ 反应扩增出ＧＢＶＣ／ＨＧＶ ＮＳ３ 基因片段,克隆至表达载体ｐＰＲＯＥＸ ＨＴａ 后进行核苷酸序列测定,待鉴定正确后经ＩＰＴＧ 诱导重组工程菌,用ＳＤＳＰＡＧＥ 和Ｗｅｓｔｅｒｎ ｂｌｏｔ 对重组蛋白进行鉴定。结果　酶切鉴定和核苷酸序列测定结果表明成功地构建了重组工程菌ｐＨＴＮＳ３／ ＤＨ５α且克隆的基因片段为ＧＢＶＣ／ＨＧＶ ＮＳ３ 基因片段。ＳＤＳＰＡＧＥ 分析诱导表达产物发现在相对分子质量约４３ ８１０处有一条明显的蛋白表达带,占菌体总量的１７ ．７ ％ 。用ＮｉＮＴＡ 亲和层析柱快捷地获得了纯化的重组蛋白。Ｗｅｓｔｅｒｎ ｂｌｏｔ 鉴定发现重组蛋白可与ＧＢＶＣ／ＨＧＶ ＲＮＡ 阳性病人血清发生抗原抗体反应。结论　获得了具备免疫反应原性的ＧＢＶＣ／ＨＧＶ ＮＳ３ 抗原,该重组蛋白可用于ＧＢＶＣ／ＨＧＶ 感染的检测。     

鼠抗丙型肝炎病毒（HCV）NS3区单克隆抗体的研制及特性分析

用淋巴细胞杂交瘤技术，制备出５株抗ＨＣＶ－ＮＳ３区单克隆抗体（ＭｃＡｂ）分别命名为Ｃ７－１，３，６，８，９。单抗特性测定结果显示５株单抗均为ＨＣＶ－ＮＳ３区特异性，与ＨＣＶ其它区域的抗原及宿主菌成份均无交叉反应，此５株单抗识别ＮＳ３区上两个不完全相关的抗原位点，其中Ｃ７－１，３，６株识别同一抗原决定簇，Ｓ７－９的识别位点与此３株有一定的相关，Ｃ７－８则识别与此４株不完全相关的位点。ＨＣＶ－ＮＳ３抗     

多重引物聚合酶链反应扩增丙型肝炎病毒基因及基 …

利用聚合酶链反应（ＰＣＲ）技术对丙型肝炎病毒（ＨＣＶ）的５’－非编码区（５’－ＮＣＲ）、Ｃ及ＮＳ４基因区的３对引物分别及同时扩增，检测８０例抗－ＨＣＶ阳性患者的血清ＨＣＶ ＲＮＡ，并进行了ＨＣＶ基因分型研究。各不同引物所介导的ＰＣＲ检出ＨＣＶ ＲＮＡ的结果为：５’－ＮＣＲ基因区６０％（４８／８０），Ｃ基因区３７％（３０／８０），ＮＳ４基因区３０％（２４／８０）。以上３对引物同时扩增仅４２％（３４／     

肝细胞肝癌中丙型肝炎病毒C区、E区、NS3区、NS4区抗原的表达

本文报道研究丙型肝炎病毒抗原在肝细胞肝癌组织内的定位分布情况。以丙型肝炎病毒（ＨＣＶ）的Ｃ、Ｅ、ＮＳ３、ＮＳ４区四种单克隆抗体用免疫组化方法检测了１３９例肝细胞肝癌（ＨＣＣ）的肝脏标本，结果总的阳性率为１５．１％。２１例阳性标本中，Ｃ区单抗检测阳性占８０．９％（１７／２１），Ｅ区占３３．３％（７／２１），ＮＳ３、ＮＳ４区均占５７．１％（１２／２１），表明应用多区段单抗有助于提高ＨＣＶ抗原的检出率。阳性物质主要存在于胞浆中，呈细、粗颗粒及块状，３例出现膜及膜下型，１例核内有阳性反应。ＨＣＶ感染与ＨＣＣ的发生发展有一定的关系。     

中国株HGV NS3区基因的原核表达及其产物的抗原性分析

目的 研究ＨＧＶ ＮＳ３区基因产物的抗原性,并探讨ＮＳ３蛋白在血清学检测中的应用。方法 将中国株ＨＧＶ ＮＥ３区的３个基因片段分别克隆到ｐＲＳＥＴ Ｂ和ｐＲＳＥＴ Ｃ质粒载体中,构建成原核表达载体。ＩＰＴＧ诱导下,在大肠杆菌ＢＬ２１中高效表达,获得３个重组蛋白,用Ｗｅｓｔｅｒｎ ｂｌｏｔ和ＥＬＩＳＡ法分别对表达产物进行分析。结果 所构建的表达载体均得到高效表达,得到的重组蛋白ＰＡ,Ｐ３和Ｐ４的分子     

NS3 serine protease of bovine viral diarrhea virus: characterization of active site residues, NS4A cofactor domain, and protease-cofactor interactions

The gene expression of bovine viral diarrhea virus (BVDV), a pestivirus, occurs via translation of a hypothetical polyprotein that is processed cotranslationally and posttranslationally by viral and cellular enzymes. A protease located in the N-terminal region of nonstructural (NS) protein NS3 catalyzes the cleavages, leading to the release of NS4A, NS4B, NS5A, and NS5B. Our study provides experimental evidence that histidine at position 1658 and aspartic acid at position 1686 constitute together with the previously identified serine at position 1752 (S1752) the catalytic triad of the pestiviral NS3 serine protease. Interestingly, a mutant protease encompassing an exchange of the active site S1752 to threonine still showed residual activity. This finding links the NS3 protease of pestiviruses to the capsid protease of Sindbis virus. Furthermore, we observed that the minimal protease domain of NS3 encompasses about 209 amino acids. The NS3 protease was found to be sensitive to N-terminal truncation because a deletion of 6 amino acids significantly reduced the cleavage efficiency at the NS4A/4B site. Larger N-terminal deletions also impaired the activity of the enzyme with respect to the other cleavage sites but to a different degree at each site. The NS3 protease of BVDV has previously been shown to depend on NS4A as cofactor. We demonstrate here that the central region of NS4A represents the cofactor domain. Furthermore, coprecipitation studies strongly suggest an interaction between NS4A and the N-terminal region of NS3. Besides the remarkable similarities observed between the pestiviral NS3 protease and the corresponding enzyme of hepatitis C virus (HCV), our results suggest a common ancestry between these enzymes and the capsid protease of Sindbis virus.     

A comparative analysis of the substrate permissiveness of HCV and GBV-B NS3/4A proteases reveals genetic evidence for an interaction with NS4B protein during genome replication

The hepatitis C virus (HCV) serine protease (NS3/4A) processes the NS3-NS5B segment of the viral polyprotein and also cleaves host proteins involved in interferon signaling, making it an important target for antiviral drug discovery and suggesting a wide breadth of substrate specificity. We compared substrate specificities of the HCV protease with that of the GB virus B (GBV-B), a distantly related nonhuman primate hepacivirus, by exchanging amino acid sequences at the NS4B/5A and/or NS5A/5B cleavage junctions between these viruses within the backbone of subgenomic replicons. This mutagenesis study demonstrated that the GBV-B protease had a broader substrate tolerance, a feature corroborated by structural homology modeling. However, despite efficient polyprotein processing, GBV-B RNAs containing HCV sequences at the C-terminus of NS4B had a pseudo-lethal replication phenotype. Replication-competent revertants contained second-site substitutions within the NS3 protease or NS4B N-terminus, providing genetic evidence for an essential interaction between NS3 and NS4B during genome replication.     

Characterisation of interaction between NS3 and NS5B protein of classical swine fever virus by deletion of terminal sequences of NS5B

The NS3-NS5B interaction of classical swine fever virus (CSFV) is important for viral replication. For characterisation of the interaction between the NS3 and NS5B, a series of NS5B mutants with deletion of N-, C-terminal amino acids and quadruple alanine substitution mutations were produced. GST pull-down assays and immunoprecipitation analyses showed that NS5B and some NS5B mutants have NS3 binding activity. Further experimental data indicated that CSFV NS5B might contain two NS3 binding sites, one covering amino acids 63-99 located at the N-terminal end, another covering amino acids 611-642 at the C-terminal end. Assays for RNA-dependent RNA polymerase (RdRp) activity revealed that CSFV NS3 is able to enhance the RdRp activity of NS5B and some NS5B mutants in vitro. The enhancement might be obtained by NS3 binding to the two terminal sequences of NS5B, which could be attractive targets for drug development against CSFV.     

A wide range of NS3/4A protease catalytic efficiencies in HCV-infected individuals

The hepatitis C virus (HCV) NS3/4A protease acts as an antagonist of virus-induced interferon (IFN) regulatory factor (IRF)-3 activation and IFN-beta expression. The NS3/4A protease performs this function by cleaving Cardif and TRIF proteins to block retinoic-acid-inducible gen I (RIG-I) and toll-like receptor (TLR)-3 signaling, respectively. NS3/4A protease inhibition can prevent Cardif and/or TRIF inactivation during HCV infection, thereby maintaining the innate immune response. Thus, differences in NS3/4A protease catalytic efficiency could be related to viral pathogenicity. In this study, we analyzed the catalytic efficiency of the most abundant NS3/4A protease isolated from each of 12 individuals infected with HCV genotypes 1b, 1a, 3a, 4a or 4d. A diversity of NS3/4A protease catalytic efficiencies (up to a six-fold difference) was found in the analyzed samples. The genotype 1b NS3/4A proteases displayed the highest catalytic efficiencies. However, within this genotype up to three-fold differences were observed. Cross-genotypic interactions between the NS3 protease domain and the NS4A cofactor peptide were also investigated. Overall, catalytic efficiencies of NS3 proteases cross-interacting with NS4A cofactors from heterologous genotypes were as efficient as the homologous NS3/4A interactions. Of the 28 heterologous interactions tested, only 6 resulted in deleterious or nonfunctional enzymes. Nonfunctional interactions were not genotype-specific, suggesting that enhancement of NS3 catalytic efficiency by the NS4A cofactor depends on a few specific amino acid residues. Characterization of the proteolytic activities of individual NS3/4A proteases should provide clues for understanding HCV-host interactions, as well as assisting in the development of new classes of NS3/4A protease inhibitors.     

聚合酶链反应诱导丙型肝炎病毒(HCV)蛋白酶活性位点的突变及突变HCVNS3/4a蛋白的表达

目的 以聚合酶链反应（PCR）突变方法诱导丙型肝炎病毒（HCV）蛋白酶活性位点ser1165的突变，获得全长非结构基因3（NS3）／4a的表达与纯化。方法 分别以NS3 N端正向引物与诱变反向引物，诱变正向引物与NS4a C端反向引物获得2个PCR产物，产物纯化后在新的PCR反应体系中加入以上2个PCR产物与NS3 N端正向引物、NS4a C端反向引物。再次PCR扩增突变模板，分别与野生型模板重组入表达载体pET26-Ub，转化大肠杆菌BL21（DE3）pCG1，诱导表达后经菌体裂解、纯清化、硫酸铵沉淀、DEAE－Sepharose、NTA纯化，Western blot分析表达蛋白的特异性及PCR诱导突变使HCV蛋白酶活性位点失活的作用。结果 获得诱导突变的模板，Western blot证实该突变可完全阻断对NS3丝氨酸蛋白酶与NS3螺旋酶间的切割，部分阻断了螺旋酶与NS4a间的切割，纯化后的HCV NS3／4a蛋白在SDS－PAGE胶上显示为双带。结论 PCR突变方法简便、有效，获得丝氨酸蛋白酶失活的NS3蛋白表达，NS3蛋白与NS4a蛋白以复合物形式存在。     

Development of robust in vitro serine protease assay based on recombinant Pakistani HCV NS3-4A protease

Hepatitis C virus (HCV) infection is a serious cause of chronic liver disease worldwide with more than 170 million infected individuals at risk of developing significant morbidity and mortality. Current interferon-based therapies are suboptimal especially in patients infected with HCV genotype 3 (predominant genotype in Pakistan) and they are poorly tolerated, highlighting the requirement of new therapeutics. HCV non-structural protein-3 (NS3) protease and helicase domains are essential for viral replication; they are highly conserved among various HCV strains. In the current study, we enrolled 56 HCV infected patients from various regions of Pakistan and determined their genotypes, ALT level and virus titer. We have cloned and sequenced NS3/NS4A from 4 of the HCV Serum samples. Nucleotide sequence alignment showed high level of identities among 3a genotypes. One of the samples (NCVI 01) showed unique amino acids substitutions, including R9Q, L332P, L354I, I605V and S622C. Three dimensional structures were determined and analyzed effect of substitutions on amino acids interactions. We further established fluorescence resonance energy transfer (FRET) based assays for detecting proteolytic activity of (NS3-4A) serine protease, using AnaSpec peptide, for high throughput screening (HTS) inhibitors against HCV. In future, this study could be of great interest in the development of HCV NS3 cell-based HTS FRET assay for genotype 3a and subsequent antiviral testing of drugs.     

A novel high throughput screening assay for HCV NS3 serine protease inhibitors

Hepatitis C virus (HCV) infection is a major worldwide health problem, causing chronic hepatitis, liver cirrhosis and primary liver cancer (Hepatocellular carcinoma). HCV encodes a precursor polyprotein that is enzymatically cleaved to release the individual viral proteins. The viral non-structural proteins are cleaved by the HCV NS3 serine protease. NS3 is regarded currently as a potential target for anti-viral drugs thus specific inhibitors of its enzymatic activity should be of importance. A prime requisite for detailed biochemical studies of the protease and its potential inhibitors is the availability of a rapid reliable in vitro assay of enzyme activity. A novel assay for measurement of HCV NS3 serine protease activity was developed for screening of HCV NS3 serine protease potential inhibitors. Recombinant NS3 serine protease was isolated and purified, and a fluorometric assay for NS3 proteolytic activity was developed. As an NS3 substrate we engineered a recombinant fusion protein where a green fluorescent protein is linked to a cellulose-binding domain via the NS5A/B site that is cleavable by NS3. Cleavage of this substrate by NS3 results in emission of fluorescent light that is easily detected and quantitated by fluorometry. Using our system we identified NS3 serine protease inhibitors from extracts obtained from natural Indian Siddha medicinal plants. Our unique fluorometric assay is very sensitive and has a high throughput capacity making it suitable for screening of potential NS3 serine protease inhibitors.     

Functional determinants of NS2B for activation of Japanese encephalitis virus NS3 protease

Japanese encephalitis virus (JEV) is a mosquito-borne flavivirus, causing severe central nerve system diseases without specific treatments. The NS2B-NS3 protease of flaviviruses mediates several cleavages on the flavivirus polyprotein, being believed to be a target for antiviral therapy. NS2B is the cofactor of the viral serine protease, correlating with stabilization and substrate recognition of the NS3 protease. In this study, we investigate the functional determinants in the JEV NS2B for the activation of the NS3 protease. Cis- and trans-cleavage assays of the deletions at the N-terminal of NS2B demonstrated that the NS2B residues Ser(46) to Ile(60) were the essential region required for both cis and trans activity of the NS3 protease. In addition, alanine substitution at the residues Trp53, Glu55, and Arg56 in NS2B significantly reduced the cis- and trans-cleavage activities of the NS3 protease. Sequence alignment and modeled structures suggested that functional determinants at the JEV NS2B residues Ser46 to Ile60, particularly in Trp53, Glu55 and Arg56 could play an important configuration required for the activity of the flavivirus NS3 protease. Our results might be useful for development of inhibitors that block the interaction between NS2B and NS3.     

Hepatitis C virus NS3/4A protein interacts with ATM, impairs DNA repair and enhances sensitivity to ionizing radiation

Hepatitis C virus (HCV) infection is frequently associated with the development of hepatocellular carcinomas and non-Hodgkin's B-cell lymphomas. Nonstructural protein 3 (NS3) of HCV possesses serine protease, nucleoside triphosphatase, and helicase activities, while NS4A functions as a cofactor for the NS3 serine protease. Here, we show that HCV NS3/4A interacts with the ATM (ataxia-telangiectasia mutated), a cellular protein essential for cellular response to irradiation. The expression of NS3/4A caused cytoplasmic translocation of either endogenous or exogenous ATM and delayed dephosphorylation of the phosphorylated ATM and gamma-H2AX following ionizing irradiation. As a result, the irradiation-induced gamma-H2AX foci persisted longer in the NS3/4A-expressing cells. Furthermore, these cells showed increased comet tail moment in single-cell electrophoresis assay, indicating increased double-strand DNA breaks. The cells harboring an HCV replicon also exhibited cytoplasmic localization of ATM and increased sensitivity to irradiation. These results demonstrate that NS3/4A impairs the efficiency of DNA repair by interacting with ATM and renders the cells more sensitive to DNA damage. This effect may contribute to HCV oncogenesis.     

Complex formation between hepatitis C virus NS2 and NS3 proteins

Hepatitis C virus (HCV) NS2 and NS3 proteins as well as the NS3 protease cofactor NS4A are essential for the replication of the virus. The presence of in vivo heterodimeric complex between HCV NS2 and NS3 has been suggested by biochemical studies. Detailed characterization of the interactions between these viral proteins is of great importance for better understanding their role in viral replication cycle and represents attractive target for antiviral agents. In this study, we demonstrated in vivo interactions between HCV NS2 and NS3 proteins using an epitope tagging technique. For this purpose NS2, NS3 and NS4A were expressed in fusion with two different tags in Cos7 cells. Immunofluorescence analysis and co-immunoprecipitation with tag-specific antibodies revealed the existence of biologically important NS3/NS4A and NS3/NS2 complexes. Similar complexes were detected also in Huh7 cells infected with Semliki Forest virus vectors expressing NS2 and NS3 or NS23 precursor polyprotein. The formation of complex between NS2 and NS3 was found not to depend on whether the proteins were expressed individually or in form of common precursor. This observation suggests the existence of direct interaction between these two proteins that may have importance for the formation of the whole HCV replication complex.