杆状病毒AcMNPV vp39基因的克隆、表达与抗体制备

目的:构建苜蓿丫纹夜蛾核多角体病毒(Autographa californica nucleopolyhedro virus,AcMNPV)VP39的原核表达载体,表达、纯化蛋白并制备多克隆抗体。方法:用PCR方法扩增vp39基因,并将其克隆至pET-21a( )上,转化到大肠杆菌BL21(DE3)中进行诱导表达,采用割胶回收的方法纯化融合蛋白,纯化的融合蛋白作为抗原,免疫新西兰大白兔,Western blot检测抗体活性。结果:构建了pET-VP39原核表达质粒,含有该质粒的大肠杆菌经IPTG诱导超量表达了一个与预期理论值相符的约为40kDa的融合蛋白。对制备的抗体进行免疫印迹分析表明该抗血清能与感染苜蓿丫纹夜蛾核多角体病毒的细胞蛋白样品发生特异性反应。结论:获得了兔抗AcMNPV-VP39多克隆抗体,为进一步深入研究VP39在病毒侵染过程中与宿主因子的相互作用提供了检测工具。     

杆状病毒Ac60基因的原核表达与亚细胞定位研究

用PCR方法从AcMNPV基因组中扩增到ORF60基因,插入原核表达载体pET-28a(+),构建pETAc60质粒,再将该质粒转化大肠埃希菌BL21,在IPTG诱导下表达了分子量约为16 ku的融合蛋白.用纯化的表达产物免疫新西兰大白兔制备了多克隆抗体,应用该抗体检测了AcMNPV感染的昆虫宿主细胞(Si9)中ORF60基因的表达,结果显示:在感染后的细胞中有2条分子量分别约为33 ku和17 ku蛋白质带能与所制备的抗体发生特异性反应.间接免疫荧光分析发现:在病毒感染的晚期,Ac60蛋白同时存在于所感染宿主的细胞核和细胞质中.     

杆状病毒ac68基因的克隆、表达与抗体制备

目的：对苜蓿丫纹夜蛾核多角体病毒（Autographa califorica multicapsid nucleopoly hedrovirus,AcMNPV）开放阅读框68（open reading frame,ORF68,ac68）进行原核表达,制备该蛋白的多克隆抗体,为深入研究其功能提供基础。方法：将ac68基因克隆至原核表达载体pET28a上,在大肠杆菌BL21（DE3）中表达Ac68蛋白,通过His抗体检测进一步验证所表达的蛋白为带有组氨酸的融合蛋白。以纯化的Ac68蛋白作为抗原,免疫昆明小鼠制备多克隆抗体。结果：实现了ac68基因的原核表达,获得了该蛋白的多克隆抗体并在AcMNPV感染的Sf-9细胞中检测到一条大小为25kD左右的特异杂交带。结论：获得的抗体可用于Ac68蛋白功能的进一步研究。     

肌动蛋白抑制了杆状病毒多角体蛋白基因的转录与表达

为进一步研究肌动蛋白在杆状病毒感染晚期的作用,利用Bac-to-Bac系统构建了表达多角体基因、肌动蛋白与绿色荧光蛋白融合基因的重组病毒vAc-ph/70GA,同时构建对照病毒vAc-ph.实验发现,重组病毒vAc-ph/70GA感染Sf9细胞后能持续表达肌动蛋白,但不能形成多角体,vAc-ph则能形成多角体.sDS-聚丙烯酰胺凝胶电泳(SDS-PAGE)显示,vAc-ph/70GA感染晚期,细胞内没有多角体蛋白的表达;RT-PCR的结果进一步表明多角体基因的转录被抑制.肌动蛋白的表达并没有影响vAc-ph/70GA对细胞的感染力.结果表明,晚期表达的外源肌动蛋白抑制了多角体基因的转录和表达,从而导致多角体不能正常产生.     

杆状病毒核衣壳组装相关蛋白研究进展

杆状病毒生命周期中会产生包埋型和芽生型两种病毒粒子,这两种病毒粒子的包膜组成存在明显的差异,但拥有相同的核衣壳结构.杆状病毒核衣壳是由衣壳蛋白和杆状病毒基因组两部分组成,核衣壳的正常组装对两种病毒粒子的形成都是不可或缺的,因此核衣壳的正常组装在病毒的整个感染传播过程中发挥着重要作用.尽管越来越多参与核衣壳组装的蛋白被鉴定出来,目前还有许多核衣壳组装细节不明了,例如这些衣壳蛋白之间的互作关系是怎样的,宿主通过何种方式参与到病毒核衣壳组装过程等.本文主要以杆状病毒模式物种苜蓿银纹夜蛾核型多角体病毒(Autographa californica multiple nucleopolyhedrovirus,AcMNPV)为例综述了参与杆状病毒核衣壳组装的相关蛋白,并对一些参与核衣壳运输有关的核衣壳蛋白也做了阐述.     

AcMNPV突变株的蛋白表达时相研究

将苜蓿银纹夜蛾多核衣壳核型多角体病毒（Autograph Clifornica nuclear polyhedrosis nvius,AcMNPV)的野生型株HR3和温度敏感突变株ts317,ts538,ts8感染草地贪夜蛾（Spodoptera frugiperda)Sf21细胞,并在允许温度（25℃）或非允许温度（33℃）下培养,分别采用过氧化物酶标记的抗P47蛋白,抗P143蛋白,抗多体蛋白和抗病毒结构蛋白的单克隆抗体检测病毒增殖过程各蛋白出现的时间。结果表明：1）P47蛋白是一种晚期（12hpi)表达蛋白,各突变株在允许温度（25℃）能够表达,但在非允许温度（33℃）不能表达。2）P143蛋白是一种早期（8hpi)表达蛋白,在允许温度和非允许温度时都能表达,ts8的表达量较少。3）在非允放温度条件下,蛋白质的合成速度高于允许温度。4）野生才突变株ts317的病毒结构蛋白（P80,GP64,VP39,P24和PTP)允许温度增殖下都能检测到,ts538和ts8表达量相对少些。5）除了GP64和除P24外,ts583和ts8感染的细胞非允许温度下不能表达病毒的结构蛋白。6）野生型毒株HR3在允许温度和允许温度下的蛋白表达无明显差异。     

苜蓿银纹夜蛾多核衣壳核型多角体病毒AcMNPV P78/83蛋白初步研究

AcMNPV ORF9编码病毒核衣壳蛋白P78/83,该蛋白在宿主细胞内以磷酸化和去磷酸化两种形式存在,能够与细胞骨架成分肌动蛋白相互作用,序列分析表明其具有与WASP蛋白类似的结构,推测可能在病毒粒子的包装、运输等过程中起重要作用.本文利用Bac-to-Bac系统构建了P78/83与绿色荧光蛋白融合表达的重组AcMNPV,激光共聚焦显微镜观察表明,重组病毒感染Sf21细胞12h后绿色荧光主要集中分布于细胞质中,24h及以后绿色荧光主要集中分布于细胞核中.感染试验表明,超表达P78/83对病毒的生长无明显的影响.     

苜蓿银纹夜蛾多核衣壳核型多角体病毒AcMNPVP78／83蛋白初步研究

AcMNPV ORb-9编码病毒核衣壳蛋白P78／83,该蛋白在宿主细胞内以磷酸化和去磷酸化两种形式存在,能够与细胞骨架成分肌动蛋白相互作用,序列分析表明其具有与WASP蛋白类似的结构,推测可能在病毒粒子的包装、运输等过程中起重要作用。本文利用Bac—to-Bac系统构建了P78／83与绿色荧光蛋白融合表达的重组AcMNPV,激光共聚焦显微镜观察表明,重组病毒感染Sf21细胞12h后绿色荧光主要集中分布于细胞质中,24h及以后绿色荧光主要集中分布于细胞核中。感染试验表明,超表达P78／83对病毒的生长无明显的影响。     

杆状病毒AcMNPV p35基因的克隆表达及多抗制备

用PCR方法扩增得到苜蓿丫纹夜蛾核多角体病毒(Autographa californic anucleopolyhedrovirus,AcM N-PV)p35基因,将其克隆至质粒pET-32a( )上,构建得到重组质粒pET-p35,转化大肠杆菌BL21(DE3),经IPTG诱导,表达了1条约为55 ku的蛋白带。以Ni2 -NTA偶连抗体检测证明所表达的蛋白为带有组氨酸的融合蛋白。采用割胶回收的方法纯化融合蛋白,以纯化的融合蛋白制备多克隆抗体,效价为1/1 024。免疫印迹分析表明,该抗血清能与感染苜蓿丫纹夜蛾核多角体病毒的细胞蛋白样品发生特异性反应。     

杆状病毒SpltMNPV ORF124基因截短片段的克隆与表达

目的:克隆并表达斜纹夜蛾核多角体病毒(Spodotura litura mulfieapsid nucleopolyhedrovirus,SpltMNPV)ORF124基因的部分编码序列.方法:用PER方法扩增目的基因序列片段,并将其克隆至原核表达载体pQE-30上,转化到Escherichia.coli M15[pREP-4]中进行诱导表达.结果:构建了pQE-tr124原核表达质粒,含有该质粒的大肠杆菌经IPTG诱导表达了一个与预期理论值相符的约为33kDa的蛋白.以Ni2+-NTA偶连抗体检测证明所表达的蛋白为带有组氨酸的融合蛋白.结论:成功表达了SpltMNPV ORF124的部分编码序列,该融合蛋白的成功表达为进一步深入研究基因的功能奠定了基础.     

A MicroRNA Encoded by Autographa californica Nucleopolyhedrovirus Regulates Expression of Viral Gene ODV-E25

Baculovirus-encoded microRNAs (miRNAs) have been described in Bombyx mori nucleopolyhedrovirus; however, most of their functions remain unclear. Here we report the identification and characterization of an miRNA encoded by Autographa californica nucleopolyhedrovirus. The identified miRNA, AcMNPV-miR-1, perfectly matched a segment in the coding sequence of the viral gene ODV-E25 and downregulated ODV-E25 mRNA expression, which likely resulted in a reduction of infectious budded virions and accelerated the formation of occlusion-derived virions.     

Multiple Nucleocapsid Packaging of Autographa californica Nucleopolyhedrovirus Accelerates the Onset of Systemic Infection in Trichoplusia ni

Among the nucleopolyhedroviruses (Baculoviridae), the occlusion-derived virus (ODV), which initiates infection in host insects, may contain only a single nucleocapsid per virion (the SNPVs) or one to many nucleocapsids per virion (the MNPVs), but the significance of this difference is unclear. To gain insight into the biological relevance of these different packaging strategies, we compared pathogenesis induced by ODV fractions enriched for multiple nucleocapsids (ODV-M) or single nucleocapsids (ODV-S) of Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) containing a β-galactosidase reporter gene. In time course experiments wherein newly molted fourth-instar Trichoplusia ni were challenged with doses of ODV-S or ODV-M that yielded the same final mortality (~70%), we characterized viral foci as either being restricted to the midgut or involving tracheal cells (the secondary target tissue, indicative of systemic infection). We found that while the timing of primary infection by ODV-S and ODV-M was similar, ODV-S established significantly more primary midgut cell foci than ODV-M, but ODV-M infected tracheal cells at twice the rate of ODV-S. The more efficient establishment of tracheal infections by ODV-M decreased the probability that infections were lost by midgut cell sloughing, explaining why higher numbers of primary infections established by ODV-S within larvae were needed to achieve the same final mortality. These results showed that the multiple nucleocapsid packaging strategy of AcMNPV accelerates the onset of irreversible systemic infections and may indicate why MNPVs have wider individual host ranges than SNPVs.     

Functional Analysis of the Autographa californica Multiple Nucleopolyhedrovirus GP64 Terminal Fusion Loops and Interactions with Membranes

The Autographa californica multiple nucleopolyhedrovirus (AcMNPV) glycoprotein GP64 is the major envelope protein of the budded virus (BV). GP64 is a class III fusion protein that mediates BV attachment to the cell surface and low-pH-triggered membrane fusion between the BV envelope and the endosome membrane during entry. Class III fusion proteins contain terminal looped structures that are believed to interact with membranes. To examine the functions of 3 loops found at the apex of the GP64 postfusion structure, we generated 2-alanine substitutions that scanned the two so-called fusion loops (loop 1 and loop 2) plus an adjacent loop structure (loop 3) that is closely attached to loop 2 and is also found at the apex of the GP64 postfusion structure. We identified essential residues from Y75 to T86 (loop 1) and N149 to H156 (loop 2) that are required for fusion activity, but no essential residues in loop 3. Further analysis revealed that critical fusion loop residues fall within two groups that are associated with either membrane merger (hemifusion) or fusion pore expansion. We next examined the interactions of soluble GP64 proteins and BV with membranes composed of various phospholipids. BV interacted directly with small unilamellar vesicles (SUVs) comprised of phospholipids phosphatidylcholine and phosphatidic acid (PC/PA) or phosphatidylcholine and phosphatidylserine (PC/PS) under neutral and acidic pH. We also examined the interactions of soluble GP64 constructs containing substitutions of the most hydrophobic residues within each of the two fusion loops. We found that a 2-residue substitution in either single loop (loop 1 [positions 81 and 82] or loop 2 [positions 153 and 154]) was not sufficient to substantially reduce the GP64-liposome interaction, but the same substitutions in both fusion loops severely reduced the GP64-liposome association at neutral pH. These results suggest that critical hydrophobic residues in both fusion loops may be involved in the interaction of GP64 with host cellular membranes and direct GP64-membrane interactions may represent a receptor-binding step prior to a low-pH-triggered conformational change.