仙台病毒血凝素神经氨酸酶在哺乳动物细胞中的 …

仙台病毒的血凝素神经氨酸酶（ＨＮ）在ＣＯＳ－７细胞中得到了表达。将具有表达功能的质粒转入非洲绿猴肾细胞ＬＬＣＭＫ２中,在抗生素筛选压力下连续传代,获得了具有抗生素抗药性的细胞系,表明ＨＮ基因已整合到该细胞的染色体中。尽管核酸酶Ｓ１实验结果表明,这些抗药性细胞内有大量ＨＮ ｍＲＮＡ的转录,但非直接免疫荧光和放射性免疫沉淀的结果却显示,细胞表面和细胞内部的ＨＮ蛋白的表达量很低。而仙台病毒持续感染的ＬＬ     

非编码序列对仙台病毒HN基因表达的调控作用

仙台病毒的血凝素神经氨酸酶 (HN)蛋白在COS 7细胞中得到了表达 .结果表明 ,SRα启动子驱动HN基因表达的活性高于鸡 β肌动蛋白启动子 .而且 ,HN基因的 5′非编码序列能促进其表达 .Northern杂交证明 ,高表达是由HN mRNA转录引起 .为研究HN基因 5′编码序列对其转录的调控作用 ,用位点专一性突变分别以角蛋白基因和细胞色素P45 0基因的 5′非编码序列替代HN基因的 5′非编码序列 ,并分别缺失HN基因 3′非编码序列 ,构建了一系列表达载体 .以氯霉素乙酰转移酶(CAT)基因为报道基因 ,用S1酶对HN mRNA转录量进行定量分析 .实验证明 ,HN基因 5′非编码序列能非特异性提高HN mRNA的转录 ,3′非编码序列对其转录也有某种特殊的调控作用 .     

CMV与T7启动子对仙台病毒微小基因组拯救效率的比较

构建一种以分泌型荧光素酶基因(Gluc)作为报告基因的仙台病毒BB1株微小基因组质粒,比较了CMV启动子与T7启动子对仙台病毒微小基因组的拯救效率。首先设计并合成锤头状核酶序列,仙台病毒trailer、L基因非编码区、N基因非编码区和leader序列以及丁型肝炎病毒核酶序列,插入含有CMV和T7双启动子的质粒pVAX1中,获得仙台微小基因组的通用型载体pVAX-miniSeV。将Gluc基因插入pVAX-miniSeV中,分别获得正向插入的仙台病毒微小基因组载体pVAX-miniSeV-Gluc(+)和反向插入的pVAX-miniSeV-Gluc(-)。用pVAX-miniSeV-Gluc(+)转染BHK21细胞能在上清中检测到高水平的Gluc活性,表明其中的CMV启动子具有正常转录功能。将pVAX-miniSeVGluc(-)和仙台病毒N、P、L蛋白表达质粒共转染BSR T7/5细胞(稳定表达T7RNA聚合酶的BHK-21细胞)检测到Gluc的高效表达,表明pVAX-miniSeV-Gluc(-)能够被有效拯救;但在BHK-21细胞中却未检测到Gluc的有效表达,提示该载体中的CMV启动子对仙台病毒微小基因组的拯救效率可能没有明显作用。为了进一步了解CMV与T7启动子各自对于仙台病毒微小基因组拯救的作用,本研究又构建了单独含有CMV或T7启动子的仙台病毒微小基因组载体pCMV-miniSeV-Gluc(-)和pT7-miniSeV-Gluc(-)。将这两种载体和仙台病毒N、P、L蛋白表达质粒分别共转染BSR T7/5细胞,结果pT7-miniSeV-Gluc(-)共转染组检测到了Gluc的高效表达,而pCMV-miniSeV-Gluc(-)共转染组未检测到,证实了通用型载体pVAX-miniSeV中仅T7启动子对仙台病毒微小基因组的拯救起了关键作用,而CMV启动子作用不明显。本研究成功构建了一种通用型双启动子仙台病毒微小基因组载体pVAX-miniSeV,并证明了T7启动子系统对仙台病毒微小基因组拯救的关键作用。本研究为下一步构建仙台病毒全基因感染性克隆打下了基础。     

仙台病毒BB1株6个编码基因的克隆及表达

在仙台病毒BB1株全基因组序列测定的基础上,用反转录和PCR方法获得了核蛋白基因(N),磷蛋白基因(P),神经血凝素基因(HN),基质蛋白基因(M)、融合蛋白基因(F)和聚合酶蛋白基因(L)等6个编码基因全长克隆;测序结果表明,其序列与Genbank中登录的序列(DQ219803)完全一致。为了提供仙台病毒基因组载体拯救和包装所需的反式作用蛋白,将N、P、M、F、HN和L分别克隆到腺病毒穿梭表达载体pDC316上,将它们分别与腺病毒基因组质粒pBHGlox△E1,3Cre共转染HEK293细胞,获得了6种复制缺陷性重组腺病毒Ad5-N、Ad5-P、Ad5-M、Ad5-F、Ad5-HN和Ad5-L。酶切结果表明6种重组腺病毒穿梭质粒构建正确;用PCR方法证明所获得的6种重组腺病毒分别携带了上述6个编码基因;用重组腺病毒感染LLC-MK2细胞后用Western blotting和免疫荧光方法检测到了相应仙台病毒编码基因的表达。本研究为仙台病毒BB1株全长基因组的拼接和病毒载体包装系统组建打下了基础。     

新型的基于基因组复制缺陷性仙台病毒载体的免疫原性疫苗平台的评价

<正>作者开发了一种以副黏病毒基因组复制缺陷性仙台病毒为基础的新型疫苗平台。这种仙台病毒载体可以表达插入到基因组的异源性基因。为了在体内验证这种新型方案,作者构建了针对呼吸道合胞病毒(RSV)和人乳头瘤病毒3型(PIV3)的联合疫苗候选物。本项研究比较了2种不同的展示异源性抗原的方法 :(i)RSV融合蛋白F,在转录单位中以分泌性蛋白形式被编码,在感染细胞中表达后可作     

重组诱导型一氧化氮合酶在NG108-15细胞中稳定表达及其生物学特性

本文用重组iNOS基因真核表达载体转染NG108-15神经母细胞瘤和神经胶质瘤杂交细胞株,获得G418抗性克隆。在稳定表达iNOS基因2~#克隆中,胞浆相酶活性增加,伴有NO_2~-含量和胞内cGMP水平增高,提示iNOS基因表达参与NO-cGMP信号转导通路,且可被L-NNA和MB所阻断。蛋白表达产物的亚细胞定位分析显示功能性iNOS主要位于细胞胞浆中。对转染细胞做外源基因整合、转录和翻译水平鉴定,证实均有较高水平iNOS mR-NA转录和特异性蛋白表达,成功地建立了稳定表达iNOS基因的工程细胞。     

一种嵌合型调控元件在肿瘤靶向基因治疗中的应用

肿瘤靶向基因治疗成功的关键是调控治疗基因在肿瘤细胞中特异、高效地表达。首次构建一种嵌合型表达调控元件,旨在转录水平、转录后水平和翻译水平上实现联合调控目的基因在肿瘤细胞中特异性表达。体外实验表明,在前列腺癌细胞系LNCa P中,该调控元件可将报告基因增强型绿色荧光蛋白(EGFP)和荧光素酶(luciferase)的肿瘤表达特异性分别提高420%和480%。体外细胞存活实验表明,运用该元件调控单纯疱疹病毒-1胸腺激酶(HSV-1 TK)的表达能特异性杀伤LNCa P细胞,验证了该元件可成功用于治疗基因的肿瘤靶向表达。     

基因修饰对鸡新城疫病毒F48E9株HN基因DNA疫苗表达效力的影响

DNA疫苗的免疫效果与抗原基因的表达量和免疫原性有直接关系, 为了提高目的基因的表达量, 本研究对NDV F48E9株的HN基因进行了修饰, 对修饰前后HN基因表达水平进行了比较。利用分子生物学软件将NDV F48E9株的HN基因的密码子全部替换为鸡体内偏嗜性密码子, 同时在HN基因的5′端加上同样已替换密码子的禽流感病毒HA蛋白信号肽序列以期望提高目的蛋白在细胞中的表达。修饰后HN基因命名为SoptiHN, 剔除信号肽的HN基因命名为optiHN。将SoptiHN、optiHN和F48E9株的HN基因分别克隆到真核表达载体pVAX1和含有多个鸡体内最适免疫刺激序列CpG-ODN的载体pVAX1-CpG中, 将他们分别命名为pV-SoptiHN、pVC-SoptiHN、pV-optiHN、pVC-optiHN和pV-HN、 pVC-HN, 用这些质粒转染293T细胞, 48小时后间接免疫荧光和Western blotting检测细胞中瞬时表达的HN蛋白。结果显示, 与未经修饰的HN基因相比, 修饰后的HN基因体外瞬时表达水平明显提高, 并且密码子优化与添加信号肽序列这两种途径都可以提高HN基因的体外表达量。     

基因修饰对鸡新城疫病毒F48E9株HN基因DNA疫苗表达效力的影响

DNA疫苗的免疫效果与抗原基因的表达量和免疫原性有直接关系, 为了提高目的基因的表达量, 本研究对NDV F48E9株的HN基因进行了修饰, 对修饰前后HN基因表达水平进行了比较。利用分子生物学软件将NDV F48E9株的HN基因的密码子全部替换为鸡体内偏嗜性密码子, 同时在HN基因的5′端加上同样已替换密码子的禽流感病毒HA蛋白信号肽序列以期望提高目的蛋白在细胞中的表达。修饰后HN基因命名为SoptiHN, 剔除信号肽的HN基因命名为optiHN。将SoptiHN、optiHN和F48E9株的HN基因分别克隆到真核表达载体pVAX1和含有多个鸡体内最适免疫刺激序列CpG-ODN的载体pVAX1-CpG中, 将他们分别命名为pV-SoptiHN、pVC-SoptiHN、pV-optiHN、pVC-optiHN和pV-HN、 pVC-HN, 用这些质粒转染293T细胞, 48小时后间接免疫荧光和Western blotting检测细胞中瞬时表达的HN蛋白。结果显示, 与未经修饰的HN基因相比, 修饰后的HN基因体外瞬时表达水平明显提高, 并且密码子优化与添加信号肽序列这两种途径都可以提高HN基因的体外表达量。     

Adsorption of LLCMK2 cell-grown Sendai virus onto human red blood cells and its release from the virus adsorbed cells

An early stage of virus adsorption was studied in a system of Sendai virus metabolically labeled with [3H]leucine in LLCMK2 cells and of human red blood cells (RBCs). The efficiency of viral release from the virus-bound RBCs by incubation at 37 C depended on the number of virus particles which had been used for adsorption onto the RBC at 4 C. When 7.8 x 10(2) virus particles were previously adsorbed onto the RBC at 4 C, most of the viruses were dissociated from the RBC at 37 C. In the case of adsorption of 3 to 12 virus particles per RBC, however, most of the viruses were not dissociated from the RBC by incubation at 37 C. Such RBC-bound viruses were released by incubation with various bacterial neuraminidases (Clostridium perfringens, etc.) or with a large number of LLCMK2 cell-grown Sendai virus (LLCMK2-Sendai) particles, but not released by treatment with hemagglutinin-neuraminidase protein (Sendai-gp) isolated from egg-grown Sendai virus.     

Protein blot analysis of virus receptors: identification and characterization of the Sendai virus receptor

Receptors for Sendai virions in human erythrocyte ghost membranes were identified by virus overlay of protein blots. Among the various erythrocyte polypeptides, only glycophorin was able to bind Sendai virions effectively. The detection of Sendai virions bound to glycophorin was accomplished either by employing anti-Sendai virus antibodies or by autoradiography, when 125I-labeled Sendai virions were used. The binding activity was associated with the viral hemagglutinin/neuraminidase (HN) glycoprotein, as inferred from the observation that the binding pattern of purified HN glycoprotein to human erythrocyte membranes was identical to that of intact Sendai virions. No binding was observed when blots, containing either human erythrocyte membranes or purified glycophorin, were probed with the viral fusion factor (F glycoprotein). Active virions competed effectively with the binding of 125I-labeled Sendai virions (or purified HN glycoprotein), whereas no competition was observed with inactivated Sendai virus. The results of the present work clearly show that protein blotting can be used to identify virus receptors in cell membrane preparations.     

Hemagglutinin-neuraminidase enhances F protein-mediated membrane fusion of reconstituted Sendai virus envelopes with cells.

Reconstituted Sendai virus envelopes containing both the fusion (F) protein and the hemagglutinin-neuraminidase (HN) (F,HN-virosomes) or only the F protein (F-virosomes) were prepared by solubilization of the intact virus with Triton X-100 followed by its removal by using SM2 Bio-Beads. Viral envelopes containing HN whose disulfide bonds were irreversibly reduced (HNred) were also prepared by treating the envelopes with dithiothreitol followed by dialysis (F,HNred-virosomes). Both F-virosomes and F,HNred-virosomes induced hemolysis of erythrocytes in the presence of wheat germ agglutinin, but the rates and extents were markedly lower than those for hemolysis induced by F,HN-virosomes. Using an assay based on the relief of self-quenching of a lipid probe incorporated in the Sendai virus envelopes, we demonstrate the fusion of both F,HN-virosomes and F-virosomes with cultured HepG2 cells containing the asialoglycoprotein receptor, which binds to a terminal galactose moiety of F. By desialylating the HepG2 cells, the entry mediated by HN-terminal sialic acid receptor interactions was bypassed. We show that both F-virosomes and F,HN-virosomes fuse with desialylated HepG2 cells, although the rate was two- to threefold higher if HN was included in the viral envelope. We also observed enhancement of fusion rates when both F and HN envelope proteins were attached to their specific receptors.     

Cytoplasmic Domain of Sendai Virus HN Protein Contains a Specific Sequence Required for Its Incorporation into Virions

In the assembly of paramyxoviruses, interactions between viral proteins are presumed to be specific. The focus of this study is to elucidate the protein-protein interactions during the final stage of viral assembly that result in the incorporation of the viral envelope proteins into virions. To this end, we examined the specificity of HN incorporation into progeny virions by transiently transfecting HN cDNA genes into Sendai virus (SV)-infected cells. SV HN expressed from cDNA was efficiently incorporated into progeny Sendai virions, whereas Newcastle disease virus (NDV) HN was not. This observation supports the theory of a selective mechanism for HN incorporation. To identify the region on HN responsible for the selective incorporation, we constructed chimeric SV and NDV HN cDNAs and evaluated the incorporation of expressed proteins into progeny virions. Chimera HN that contained the SV cytoplasmic domain fused to the transmembrane and external domains of the NDV HN was incorporated to SV particles, indicating that amino acids in the cytoplasmic domain are responsible for the observed specificity. Additional experiments using the chimeric HNs showed that 14 N-terminal amino acids are sufficient for the specificity. Further analysis identified five consecutive amino acids (residues 10 to 14) that were required for the specific incorporation of HN into SV. These residues are conserved among all strains of SV as well as those of its counterpart, human parainfluenza virus type 1. These results suggest that this region near the N terminus of HN interacts with another viral protein(s) to lead to the specific incorporation of HN into progeny virions.     

Identification and characterization of cell lines with a defect in a post-adsorption stage of Sendai virus-mediated membrane fusion

In the early stage of infection, Sendai virus delivers its genome into the cytoplasm by fusing the viral envelope with the cell membrane. Although the adsorption of virus particles to cell surface receptors has been characterized in detail, the ensuing complex process that leads to the fusion between the lipid bilayers remains mostly obscure. In the present study, we identified and characterized cell lines with a defect in the Sendai virus-mediated membrane fusion, using fusion-mediated delivery of fragment A of diphtheria toxin as an index. These cells, persistently infected with the temperature-sensitive variant Sendai virus, had primary viral receptors indistinguishable in number and affinity from those of parental susceptible cells. However, they proved to be thoroughly defective in the Sendai virus-mediated membrane fusion. We also found that viral HN protein expressed in the defective cells was responsible for the interference with membrane fusion. These results suggested the presence of a previously uncharacterized, HN-dependent intermediate stage in the Sendai virus-mediated membrane fusion.     

Association of the parainfluenza virus fusion and hemagglutinin-neuraminidase glycoproteins on cell surfaces.

We previously observed that cell fusion caused by human parainfluenza virus type 2 or type 3 requires the expression of both the fusion (F) and hemagglutinin-neuraminidase (HN) glycoproteins from the same virus type, indicating that a type-specific interaction between F and HN is needed for the induction of cell fusion. In the present study we have further investigated the fusion properties of F and HN proteins of parainfluenza virus type 1 (PI1), type 2 (PI2), and type 3 (PI3), Sendai virus (SN), and simian virus 5 (SV5) by expression of their glycoprotein genes in HeLa T4 cells using the vaccinia virus-T7 transient expression system. Consistent with previous results, cell fusion was observed in cells transfected with homotypic F/HN proteins; with one exception, coexpression of any combination of F and HN proteins from different viruses did not result in cell fusion. The only exception was found with the closely related PI1 HN and SN HN glycoproteins, either of which could interact with SN F to induce cell fusion upon coexpression as previously reported. By specific labeling and coprecipitation of proteins expressed on the cell surface, we observed that anti-PI2 HN antiserum coprecipitated PI2 F when the homotypic PI2 F and PI2 HN were coexpressed, but not the F proteins of other paramyxoviruses when heterotypic F genes were coexpressed with PI2 HN, suggesting that the homotypic F and HN proteins are physically associated with each other on cell surfaces. Furthermore, we observed that PI3 F was found to cocap with PI3 HN but not with PI2 HN, also indicating a specific association between the homotypic proteins. These results indicate that the homotypic F and HN glycoproteins are physically associated with each other on the cell surface and suggest that such association is crucial to cell fusion induced by paramyxoviruses.