嵌合HCV串联多表位的乙肝S基因真核载体构建及表达

[目的]构建丙型肝炎病毒(hepatitis C virus,HCV)串联多中和抗原表位与乙型肝炎病毒(hepatitis B virus,HBV)S抗原嵌合基因真核表达质粒,并在293T细胞中进行表达。[方法]将HCV基因中高度保守且具有广谱交叉中和活性的三个表位和一个HVR1模拟表位串连。串联表位嵌合于HBV S基因的氨基端胞外区,形成嵌合基因MEpS;将基因克隆至真核表达载体pCI-neo中,构建重组质粒pCI-MEpS。将质粒转染至293T细胞中,间接免疫荧光及Western Blot检测嵌合基因的表达情况。[结果]重组质粒经双酶切证实构建正确;pCI-MEpS转染的293T细胞胞浆内可见较强的绿色荧光,Western Blot显示pCI-MEpS在相对分子量约38 kDa处可见蛋白条带。[结论]构建了HBV S抗原嵌合HCV串联多中和抗原表位的重组质粒,成功在293T细胞中表达,为制备嵌合HCV串联多中和抗原表位的HBV S抗原VLPs,研究嵌合VLPs免疫动物后产生的中和抗体的保护作用奠定了实验基础。     

嵌合中国河北株包膜蛋白基因的HCV细胞培养模型的传代分析

建立稳定的嵌合中国河北株包膜蛋白基因的丙型肝炎病毒(HCV)细胞培养体系,进行传代特性分析。本研究经体外转录获得嵌合中国河北株包膜蛋白基因的丙型肝炎病毒(HCV)全长RNA,脂质体法转染Huh7.5-CD81细胞,连续传代培养,进行Real Time RT-PCR、间接免疫荧光、Western blot、再感染试验与感染滴度检测及序列分析。结果表明:嵌合重组HCV RNA转染Huh7.5-CD81细胞后可产生感染性的病毒颗粒(HCVcc);传代过程中,Western blot可检测细胞内HCV蛋白的表达;IFA检测阳性细胞数逐渐增多,41d升至高峰,达80%~90%;Real Time RT-PCR检测传代细胞上清中HCV RNA拷贝数在104~107拷贝/mL;再感染实验嵌合HCVcc最高感染滴度为104ffu/mL。序列分析显示在传代后期嵌合的HCV包膜基因发生了适应性突变,导致6处氨基酸改变。结论嵌合中国河北株1b亚型包膜蛋白基因的HCV细胞培养体系可以产生具有感染性的嵌合HCV病毒颗粒,传代后感染性增强并且嵌合的HCV包膜基因发生了适应性突变。     

轮状病毒VP4抗原表位在VP6载体蛋白同一位点表达比较研究

目的:评价轮状病毒(RV)VP4两个抗原表位插入VP6载体蛋白同一位点所表达的重组嵌合蛋白免疫学性质及在研制嵌合蛋白疫苗中的意义。方法:采用分子克隆和基因重组技术将RV VP4的两个抗原表位插入到VP6载体蛋白同一位点上,构建重组抗原表达质粒,表达携带不同抗原表位的重组嵌合蛋白,用Western blot和中和试验分析重组嵌合蛋白的抗原反应性和免疫原性。结果:成功构建了两个嵌合蛋白表达质粒,并在大肠杆菌中高效表达;表达的嵌合蛋白可与相应抗体特异性反应;可诱导豚鼠产生特异性血清抗体;抗嵌合蛋白血清抗体可特异性识别载体蛋白VP6F,Wa株病毒的VP6和VP4蛋白,可中和Wa株病毒在MA104细胞上的感染性;结果表明,所构建和表达的两个以VP6为载体的VP4抗原表位嵌合蛋白具有较高抗原反应性和免疫原性;嵌合蛋白携带的VP4抗原表位具有增强载体蛋白免疫原性作用;为研制新型RV重组蛋白疫苗的奠定了较好的基础。     

丙型肝炎病毒感染的体外培养细胞的抗原表达

建立丙型肝炎病毒（HCV）体外感染细胞模型,观察其感染细胞的HCV抗原表达,用抗HCV抗体和HCVRNA阳性及阴性血清感染MOLT-4细胞,制备细胞片进行免疫酶染色。结果显示HCV感染MOLT-4细胞4天和阴性对照HCV抗原均为阴性;感染后7天胞浆内可见HCV抗原阳性免疫反应产物;15天阳性细胞达到高峰,43天仍可见少量阳性细胞。结果表明HCV体外感染MOLT-4细胞胞浆内观察到HCV抗原表达。     

嵌合型HCV全长cDNA的构建及体外转录制备感染性RNA的研究

构建HCV la/1b嵌合型全长cDNA克隆,进行体外转录,脂质体法转染HepG2细胞,以RT-PCR法检测HCV正、负链RNA,Western印迹检测HCV蛋白表达.结果表明,细胞在转染后8代(约35d)内,能间断检测到HCV正、负链RNA以及相对分子质量约70000的HCV NS3蛋白,证明该HCV嵌合体可以在细胞中复制和表达.本研究表明含有该嵌合型全长cDNA的质粒可以为后续HCV的研究提供大量可重复的性质均一的病毒模板,有助于深入了解HCV的复制机制.     

丙肝抗原决定簇与CTB的融合、表达及融合蛋白的纯化

通过固相化学合成法合成了编码丙型肝炎病毒(HCV)结构区和非结构区的4个抗原决定簇基因,这些抗原决定簇基因片段以不同方式串联后与ctxB基因融合,构建了12种表达不同嵌合蛋白的重组质粒,各重组质粒转化大肠杆菌后均能高效分泌性表达融合蛋白,表达产量在10～50μg/ml之间,随所融合的抗原决定簇不同而不同,表达水平主要与抗原决定簇的氨基酸组成有关,而与抗原决定簇的大小及串联次数关系不大。融合蛋白通过亲和层析纯化,达到了电泳纯,为进一步研究融合蛋白的抗原性及用作抗-HCV ELISA诊断试剂抗原打下了基础。     

EV71病毒中和表位和诺如病毒P结构域嵌合蛋白的原核表达

目的:构建肠道病毒71型(Enterovirus71,EV71)的线性中和抗原表位与诺如病毒P结构域融合基因的重组质粒,在大肠杆菌中表达诺如病毒P结构域与EV71中和抗原表位的嵌合蛋白。方法:根据已报道的3个EV71线性中和抗原表位的氨基酸序列,按大肠杆菌密码子表达使用的偏好性优化和设计各线性中和抗原表位的核苷酸序列,将这些表位以单个或不同的组合克隆至含诺如病毒P结构域和GST标签的质粒中,经测序确认后,分别转化到E.coli BL21(DE3)感受态细胞中,通过IPTG诱导融合蛋白表达。用GST融合蛋白纯化磁珠对融合蛋白进行纯化,最后通过免疫印迹法确认融合蛋白的表达及嵌合蛋白的抗原性。结果:测序结果表明,成功地构建了含EV71病毒3个单表位和4个串联中和抗原表位的诺如病毒P结构域重组质粒,而且这7个含线性中和抗原表位的嵌合蛋白在大肠杆菌中都以可溶形式得到了表达。免疫印迹分析表达蛋白的抗原性结果表明,表达的嵌合蛋白都能与抗诺如病毒P结构域抗血清反应。除了含单表位的SP55和SP28嵌合蛋白外,其它的嵌合蛋白均能与抗EV71病毒的抗血清反应。结论:成功地在大肠杆菌中表达了诺如病毒P结构域和EV71病毒中和抗原表位的嵌合蛋白,且具有抗原性,这为诺如病毒和EV71病毒的二价疫苗及检测方法的研发奠定了基础。     

人-鼠嵌合Fab片段的温度诱导表达

构建了具有λPRPL启动子高效表达人鼠嵌合Fab片段的温度诱导表达型载体pHZ01。并在大肠杆菌中表达了三种嵌合Fab片段：抗前列腺特异抗原(PSA)的嵌合Fab．抗溶菌酶(HEL)的嵌合Fab和抗破伤风类毒素(TT)的嵌合Fab．三种表达的可溶 性嵌合Fab都具有特异结合抗原的能力,嵌合Fab的CHI和CK区均为人源的。较之鼠源 Fab具有更好的应用前景。     

人-鼠嵌合Fab片段的温度诱导表达

构建了具有λＰＲＰＬ启动子高效表达人鼠嵌合Ｆａｂ片段的温度诱导表达型载体ｐＨＺ０１,并在大肠杆功中表达了三种嵌合Ｆａｂ片段：抗前列腺特异抗原（ＰＳＡ）的嵌合Ｆａｂ,抗溶菌酶（ＨＥＬ）的嵌合Ｆａｂ和抗破伤风类毒素（ＴＴ）的嵌合Ｆａｂ,三种表达的可溶性嵌合Ｆａｂ都具有特异结合抗原的能力,嵌合Ｆａｂ的ＣＨ１和ＣＫ区均为人源的,较之鼠源Ｆａｂ具有更好的应用前景。     

嵌合中国分离株基因的丙型肝炎病毒（1b／2a）细胞培养模型的建立

目的：建立嵌合中国分离株基因的丙型肝炎病毒（HCV）细胞培养模型。方法：利用3片段融合PCR的方法将中国HCV河北分离株（1b）的全长包膜蛋白基因引入JFH1（2a）株基因骨架,构建包膜蛋白基因区相互置换的嵌合HCV（1b／2a）全长基因组,经线性化后体外转录获得全长RNA,转染Huh7．5．1细胞系,用免疫荧光及蛋白印迹实验检测。结果：该RNA可以产生具有体外感染活性的嵌合HCV,且感染性可在共同培养的细胞间传播。结论：首次在国内建立了嵌合中国HCV分离株基因的HCV细胞培养体系。     

Persistent replication of a hepatitis C virus genotype 1b‐based chimeric clone carrying E1, E2 and p6 regions from GB virus B in a New World monkey

The development of effective hepatitis C virus (HCV) vaccines is essential for the prevention of further HCV dissemination, especially in developing countries. Therefore the aim of this study is to establish a feasible and immunocompetent surrogate animal model of HCV infection that will help in evaluation of the protective efficacy of newly developing HCV vaccine candidates. To circumvent the narrow host range of HCV, an HCV genotype 1b‐based chimeric clone carrying E1, E2 and p6 regions from GB virus B (GBV‐B), which is closely related to HCV, was generated. The chimera between HCV and GBV‐B, named HCV/G, replicated more efficiently as compared with the HCV clone in primary marmoset hepatocytes. Furthermore, it was found that the chimera persistently replicated in a tamarin for more than 2 years after intrahepatic inoculation of the chimeric RNA. Although relatively low (<200 copies/mL), the viral RNA loads in plasma were detectable intermittently during the observation period. Of note, the chimeric RNA was found in the pellet fraction obtained by ultracentrifugation of the plasma at 73 weeks, indicating production of the chimeric virus. Our results will help establish a novel non‐human primate model for HCV infection on the basis of the HCV/G chimera in the major framework of the HCV genome.     

Construction of a chimeric hepatitis C virus replicon based on a strain isolated from a chronic hepatitis C patient

Subgenomic replicons of hepatitis C virus (HCV) have been widely used for studying HCV replication. Here, we report a new subgenomic replicon based on a strain isolated from a chronically infected patient. The coding sequence of HCV was recovered from a Chinese chronic hepatitis C patient displaying high serum HCV copy numbers. A consensus sequence designated as CCH strain was constructed based on the sequences of five clones and this was classified by sequence alignment as belonging to genotype 2a. The subgenomic replicon of CCH was replication-deficient in cell culture, due to dysfunctions in NS3 and NS5B. Various JFH1/CCH chimeric replicons were constructed, and specific mutations were introduced. The introduction of mutations could partially restore the replication of chimeric replicons. A replication-competent chimeric construct was finally obtained by the introduction of NS3 from JFH1 into the backbone of the CCH strain.     

HCV 1a／1b型嵌合体能在HepG2细胞内复制与表达

采用HCV 1a／1b嵌合体cDNA构建表达质粒转染HepG2细胞,以免疫组化和Westem blotting检测HCV蛋白表达,RT-PCR检测HCV正、负链RNA,研究丙型肝炎病毒(HCV) 1a和1b型嵌合体全长cDNA在HepG2细胞中的复制和表达。结果证明,转染细胞中检测到分子量约70kDa的HCV NS3蛋白,转染细胞连续传20代,仍能检测到HCV正、负链RNA。表明该HCV嵌合体可以在细胞中复制和表达,HCV1b型的RNA依赖的RNA聚合酶(RdRp)可以起始含1a型非编码区的病毒复制。HCV5′端非翻译区第11、12、13、34和35位核苷酸改变可不影响其与核糖体结合。3′非翻译区9400,9403和9407位核苷酸改变,9435位缺失“A”,9409,9410位及9495,9496,9497位分别插入“TT”和“AAT”可不影响RdRp的生物活性。本研究对阐明HCV复制和翻译机制有重要意义。     

丙型肝炎病毒基因组C区和NS3区基因cDNA的融合及其在大肠杆菌中的表达与初步应用

通过逆转录（ＲＴ）－聚合酶链式反应（ＰＣＲ）,从中国人丙型肝炎病毒（ＨＣＶ）携带者的血清中扩增并克隆到２段ｃＤＮＡ片段,即ＨＣＶ基因组Ｃ区抗原基因Ｃ８３１ｃＤＮＡ片断（约５３０ｂｐ）和ＮＳ３区抗原基因Ｃ３３ｃｃＤＮＡ片段（约８６０ｂｐ）。Ｃ３３ｃｃＤＮＡ片段同Ｃ８３１ｃＤＮＡ片段经连接　　　肽Ｓｅｒ－Ｐｒｏ－Ｇｌｙ－Ｓｅｒ连接成为基因嵌合体Ｃ３３ｃ－Ｃ８３１（约１４００ｂｐ）。Ｃ３３ｃ－Ｃ８３１基因嵌合体同温控型原核表达载体ｐＢＶ２２０重组,构建成表达质粒ｐＢＶ／Ｃ３３ｃ－Ｃ８３１,并在大肠杆菌细胞中获得了重组嵌合抗原Ｃ３３ｃ－ＣＬ的表达。通过酶切分析和Ｗｅｓｔｅｒｎ免疫印迹法,对约占菌体可溶性蛋白９％的表达产物做了鉴定。采用ＴｒｉｔｏｎＸ－１００和盐析处理,获得粗提表达产物。粗提的表达产物经尿素裂解和离子交换层析纯化,得到可用于检测抗ＨＣＶ核壳蛋白和抗ＮＳ３区抗体的重组嵌合抗原Ｃ３３ｃ－ＣＬ。对Ｃ３３ｃ－ＣＬ做抗原性分析发现,它同时具有完整的Ｃ３３ｃ抗原和Ｃ２２抗原的免疫反应活性,完全能替代单纯的Ｃ３３ｃ和Ｃ２２抗原。该嵌合抗原在血清学诊断中有重要的应用价值,可望成为新一代ＨＣＶＥＩＡ诊断试剂的优选抗原。     

A Cell Culture Adapted HCV JFH1 Variant That Increases Viral Titers and Permits the Production of High Titer Infectious Chimeric Reporter Viruses

The unique properties of the hepatitis C virus (HCV) JFH1 isolate have made it possible to produce and study HCV in an infectious cell culture system. However, relatively low virus titers restrict some of the uses of this system and preparing infectious chimeric reporter viruses have been difficult. In this study, we report cell culture-adapted mutations in wild-type JFH1 yielding higher titers of infectious particles of both JFH1 and chimeric JFH1 viruses carrying reporter genes. Sequencing analyses determined that ten of the sixteen nonsynonymous mutations were in the NS5A region. Individual viruses harboring specific adaptive mutations were prepared and studied. The mutations in the NS5A region, which included all three domains, were most effective in increasing infectious virus production. Insertion of two reporter genes in JFH1 without the adaptive mutations ablated the production of infectious HCV particles. However, the introduction of specific adaptive mutations in the NS5A region permitted reporter genes, Renilla luciferase (Rluc) and EGFP, to be introduced into JHF1 to produce chimeric HCV-NS5A-EGFP and HCV-NS5A-Rluc reporter viruses at relatively high titers of infectious virus. The quantity of hyperphosphorylated NS5A (p58) was decreased in the adapted JFH1 compared wild type JFH1 and is likely be involved in increased production of infectious virus based on previous studies of p58. The JFH1-derived mutant viruses and chimeric reporter viruses described here provide new tools for studying HCV biology, identifying HCV antivirals, and enable new ways of engineering additional infectious chimeric viruses.     

Mutational Analysis of Hepatitis C Virus NS5B in the Subgenomic Replicon Cell Culture

The hepatitis C virus (HCV) NS5B is an RNA-dependent RNA polymerase (RdRP), a central catalytic enzyme of HCV RNA replication. We previously identified five novel residues of NS5B in a JK-1 isolate indispensable for RdRP activity in vitro (Qin, W., Yamashita, T., Shirota, Y., Lin, Y., Wei, W., and Murakami, S. (2001) Hepatology 33, 728-737). We addressed the role of these residues in HCV RNA replication using a HCV replicon system derived from an M1LE isolate (Kishine, H., Sugiyama, K., Hijikata, M., Kato, N., Takahashi, H., Noshi, T., Nio, Y., Hosaka, M., Miyanari, Y., and Shimotohno, K. (2002) Biochem. Biophys. Res. Commun. 293, 993-999). The five residues of NS5B in M1LE were found to be critical for HCV replication in vivo and also indispensable for RdRP activity in vitro along with purified bacterial recombinant proteins. We also found a chimeric replicon of JK-1 and M1LE in which only the NS5B sequence derived from JK-1 could not replicate in Huh-7 cells. The residues responsible for the phenomenon were mapped by several chimeric and substituted forms of NS5B M1LE and/or JK-1 isolates in the HCV RNA replicon. Two residues, amino acids 220 and 288, were critical, and two residues, amino acids 213 and 231, were important for efficient HCV replication. Mutant JK-1 NS5B harboring all four residues of M1LE was replication-competent in the chimeric replicon and was as efficient as the original M1LE replicon. By comparing the replication competence in vivo and RdRP activity in vitro with various chimeric and mutated versions of NS5B, the HCV replication ability was found to correlate well with the RdRP activity. However, heat- and dilution-sensitive NS5Bs exhibiting weaker RdRP activity in vitro were found to be replication-incompetent, suggesting that HCV replication requires RdRP activity higher than a certain critical threshold.     

Selection of Functional Variants of the NS3-NS4A Protease of Hepatitis C Virus by Using Chimeric Sindbis Viruses

The NS3-NS4A serine protease of hepatitis C virus (HCV) mediates four specific cleavages of the viral polyprotein and its activity is considered essential for the biogenesis of the HCV replication machinery. Despite extensive biochemical and structural characterization, the analysis of natural variants of this enzyme has been limited by the lack of an efficient replication system for HCV in cultured cells. We have recently described the generation of chimeric HCV-Sindbis viruses whose propagation depends on the NS3-NS4A catalytic activity. NS3-NS4A gene sequences were fused to the gene coding for the Sindbis virus structural polyprotein in such a way that processing of the chimeric polyprotein, nucleocapsid assembly, and production of infectious viruses required NS3-NS4A-mediated proteolysis (G. Filocamo, L. Pacini, and G. Migliaccio, J. Virol. 71:1417–1427, 1997). Here we report the use of these chimeric viruses to select and characterize active variants of the NS3-NS4A protease. Our original chimeric viruses displayed a temperature-sensitive phenotype and formed lysis plaques much smaller than those formed by wild-type (wt) Sindbis virus. By serially passaging these chimeric viruses on BHK cells, we have selected virus variants which formed lysis plaques larger than those produced by their progenitors and produced NS3-NS4A proteins different in size and/or sequence from those of the original viruses. Characterization of the selected protease variants revealed that all of the mutated proteases still efficiently processed the chimeric polyprotein in infected cells and also cleaved an HCV substrate in vitro. One of the selected proteases was expressed in a bacterial system and showed a catalytic efficiency comparable to that of the wt recombinant protease.