The first two nucleotides of the respiratory syncytial virus antigenome RNA replication product can be selected independently of the promoter terminus

There is limited knowledge regarding how the RNA-dependent RNA polymerases of the nonsegmented negative-strand RNA viruses initiate genome replication. In a previous study of respiratory syncytial virus (RSV) RNA replication, we found evidence that the polymerase could select the 5'-ATP residue of the genome RNA independently of the 3' nucleotide of the template. To investigate if a similar mechanism is used during antigenome synthesis, a study of initiation from the RSV leader (Le) promoter was performed using an intracellular minigenome assay in which RNA replication was restricted to a single step, so that the products examined were derived only from input mutant templates. Templates in which Le nucleotides 1U, or 1U and 2G, were deleted directed efficient replication, and in both cases, the replication products were initiated at the wild-type position, at position -1 or -2 relative to the template, respectively. Sequence analysis of the RNA products showed that they contained ATP and CTP at the -1 and -2 positions, respectively, thus restoring the mini-antigenome RNA to wild-type sequence. These data indicate that the RSV polymerase is able to select the first two nucleotides of the antigenome and initiate at the correct position, even if the 3'-terminal two nucleotides of the template are missing. Substitution of positions +1 and +2 of the template reduced RNA replication and resulted in increased initiation at positions +3 and +5. Together these data suggest a model for how the RSV polymerase initiates antigenome synthesis.     

住院肺炎患儿偏肺病毒和呼吸道合胞病毒感染研究

为探讨沈阳地区肺炎患儿中偏肺病毒(hMPV)和呼吸道合胞病毒(RSV)感染情况,用反转录聚合酶链反应(RT-PCR)法对部分因肺部感染住院患儿进行了病原学研究。结果显示,hMPV感染率为9%;而RSV感染率为46%,其中A型占40%,B型占60%。研究结果表明,在婴幼儿肺炎患儿中RSV感染率高于hMPV感染率,两者所致肺炎在发病年龄、性别及临床症状上无显著区别。     

负链不分节段RNA病毒反向遗传系统中通用型真核表达载体的构建

本研究选择pVAX1作为供体载体,通过分子克隆方法,分别用人工合成的锤头型核酶、丁型肝炎核酶序列(用于获得转录后病毒基因组RNA的精确末端)和含有9个常用限制性酶切位点的linker序列(用于病毒基因组插入的多克隆酶切位点)取代真核表达载体pVAX1的多克隆酶切位点,将其改造成负链不分节段RNA病毒反向遗传系统的通用型表达载体。通过酶切鉴定和序列测定表明,pVAX1载体中插入的核酶及linker序列正确无误,并将CTN株狂犬病病毒全长基因组cDNA插入pVAX-R中,通过与辅助质粒的共转染成功拯救CTN株狂犬病毒,证明通用型真核表达载体构建成功,为快速建立负链不分节段RNA病毒反向遗传系统奠定基础。     

人呼吸道合胞病毒M蛋白非复制型重组腺病毒的构建和鉴定

人呼吸道合胞病毒（human respiratory syncytial virus, RSV)基质蛋白（matrix protein,M）在RSV形态发生上具有重要作用,因含有CTL抗原表位,在疫苗研究上具有一定意义。为此,应用RT-PCR 方法从感染RSV的HEp-2 细胞中扩增获得M蛋白基因,构建了含M基因的非复制型重组腺病毒并进行表达和鉴定。基因序列分析显示RSV M基因仅有一处碱基发生错义突变。非复制型重组腺病毒DNA分子FGAd/RSVM转染293细胞,观察到细胞出现CPE,RT-PCR发现M基因有转录,Western blotting及间接免疫荧光分析检测到M蛋白。成功克隆A亚型RSV Long株M基因,并获得一株可表达A亚型RSV M蛋白的非复制型重组腺病毒FGAd/RSVM,可用于体内研究观察其免疫效果及免疫保护作用。     

呼吸道合胞病毒疫苗研究进展

呼吸道合胞病毒(RSV)是引起严重下呼吸道感染的重要病原体,尽管经历了半个多世纪的努力,至今仍未有安全有效的RSV疫苗上市。近年来在RSV F蛋白结构生物学方面的研究进展为新一代RSV疫苗的开发提供了新方向,同时更多的采用不同技术、或针对不同人群的RSV侯选疫苗也在迅速发展,尤其是针对婴幼儿及老年人的RSV侯选苗已有60多种在研究中,大部分已处于临床前研究阶段,18种侯选苗已进入临床试验。我们简要介绍RSV疫苗的最新研究进展。     

呼吸道合胞病毒重组蛋白候选疫苗的质粒构建、表达及免疫原性和保护性研究

PCR扩增呼吸道合胞病毒（respiratory syncytial virus,RSV）M2 蛋白的CD8＋T细胞表位F/M2:81-95和RSV-G蛋白的B细胞表位片段G:125～225（简称G1）,以一个Linker连接,插入质粒pET-DsbA中构建原核表达重组质粒, 转染E.coli BL21(DE3)后成功表达了融合蛋白DsbA-G1-Linker-F/M2:81-95（简称D-G1LF/M2）,Western-blot结果表明该融合蛋白是RSV特异性的,采用Ni+螯合亲和层析法纯化变性的包涵体溶液,经梯度透析法复性,用该蛋白免疫BALB/c小鼠,结果表明被免疫小鼠肺部及血清中产生了高滴度的抗D-G1LF/M2及抗RSV IgG抗体和中和抗体,同时还诱导产生了RSV特异性的CTL应答;IgG的亚型IgG1/IgG2a的比值为2.66;用RSV攻击免疫后的小鼠,病毒滴定法检测肺部RSV滴度,结果表明D-G1LF/M2对小鼠肺部具有保护作用。     

Genome 3'-end repair in dengue virus type 2

Genomes of RNA viruses encounter a continual threat from host cellular ribonucleases. Therefore, viruses have evolved mechanisms to protect the integrity of their genomes. To study the mechanism of 3′-end repair in dengue virus-2 in mammalian cells, a series of 3′-end deletions in the genome were evaluated for virus replication by detection of viral antigen NS1 and by sequence analysis. Limited deletions did not cause any delay in the detection of NS1 within 5 d. However, deletions of 7–10 nucleotides caused a delay of 9 d in the detection of NS1. Sequence analysis of RNAs from recovered viruses showed that at early times, virus progenies evolved through RNA molecules of heterogeneous lengths and nucleotide sequences at the 3′ end, suggesting a possible role for terminal nucleotidyl transferase activity of the viral polymerase (NS5). However, this diversity gradually diminished and consensus sequences emerged. Template activities of 3′-end mutants in the synthesis of negative-strand RNA in vitro by purified NS5 correlate well with the abilities of mutant RNAs to repair and produce virus progenies. Using the Mfold program for RNA structure prediction, we show that if the 3′ stem–loop (3′ SL) structure was abrogated by mutations, viruses eventually restored the 3′ SL structure. Taken together, these results favor a two-step repair process: non-template-based nucleotide addition followed by evolutionary selection of 3′-end sequences based on the best-fit RNA structure that can support viral replication.     

Structure-activity relationship of uridine-based nucleoside phosphoramidate prodrugs for inhibition of dengue virus RNA-dependent RNA polymerase

To identify a potent and selective nucleoside inhibitor of dengue virus RNA-dependent RNA polymerase, a series of 2′- and/or 4′-ribose sugar modified uridine nucleoside phosphoramidate prodrugs and their corresponding triphosphates were synthesized and evaluated. Replacement of 2′-OH with 2′-F led to be a poor substrate for both dengue virus and human mitochondrial RNA polymerases. Instead of 2′-fluorination, the introduction of fluorine at the ribose 4′-position was found not to affect the inhibition of the dengue virus polymerase with a reduction in uptake by mitochondrial RNA polymerase. 2′-C-ethynyl-4′-F-uridine phosphoramidate prodrug displayed potent anti-dengue virus activity in the primary human peripheral blood mononuclear cell-based assay with no significant cytotoxicity in human hepatocellular liver carcinoma cell lines and no mitochondrial toxicity in the cell-based assay using human prostate cancer cell lines.     

重组西尼罗病毒NS5融合蛋白依赖RNA的RNA聚合酶特性鉴定

西尼罗病毒(West Nile virus, WNV)非结构蛋白NS5是病毒基因组复制的关键蛋白.以病毒全长cDNA克隆为模板,PCR扩增获得NS5的RNA依赖的RNA聚合酶(RdRp)活性区（NS5pol）及该蛋白完整的编码序列（NS5F）,分别克隆于原核表达载体pET-28a 并转化至大肠杆菌E.coliBL21（DE3）中诱导表达.表达的可溶性重组蛋白经Ni柱亲和层析纯化后进行SDS-PAGE和Western印迹鉴定.结果显示,二者均为病毒特异蛋白,且纯度均在90%以上.进一步的体外RdRp分析及EMSA的结果表明,NS5pol和NSF5均有较高的RdRp活性,且该活性具有RNA模板序列和二级结构的特异性.获得的具有RdRp活性的NS5pol和NS5F为西尼罗病毒基因组复制相关元件的研究奠定了基础.     

呼吸道合胞病毒感染促进豚鼠产生气道高反应性及其机制研究

目的：通过检测气道反应性和M2受体功能,研究呼吸道合胞病毒（RSV）感染与哮喘发病的关系及机制。方法：34只豚鼠随机分为4组：Hep-2滴鼻＋生理盐水雾化（Hep-2／NS,A）组,RSV滴鼻＋生理盐水雾化（RSV／NS,B）组,Hep-2滴鼻＋鸡卵蛋白（OVA）雾化（Hep-2／OVA,C）组和RSV滴鼻＋OVA雾化（RSV／OVA,D）组,其中A和B纽各9只,C和D组各8只,以A组为对照组。21d通过电刺激迷走神经检测各组气道反应性和M2受体功能,行嗜酸性粒细胞计数以及病理学观察。结果：B组气道内压力（mmH2O）与A组无明显差异（P〉0．05）,给予匹罗卡品,IP下降幅度高于A组,但差别无显著性（P〉0．05）。C组IP明显高于A且（P〈0．05）,且给予匹罗卡品,IP下降幅度明显低于A组,差别有显著性（P〈0．05）。D组IP明显高于C组（P〈0．05）,给予匹罗卡品后IP下降幅度明显低于C组（P〈0．05）。结论：RSV感染可促进过敏原引起的M2R功能障碍,从而促进AHR发生。     

Localization of the replicase recognition site within brome mosaic virus RNA by hybrid-arrested RNA synthesis

Summary 3 terminal fragments of BMV RNA as short as 153 bases in length serve as efficient templates in vitro for BMV-specific RNA polymerase. Template activity of such fragments or of native BMV RNA is abolished when cDNA fragments as short as 39 bases are hybridized to their 3 termini. Hybridization of cDNa fragments to regions of BMV RNA 200 or more bases distal to the 3 end has no discernible effect on initiation and little effect on elongation. We conclude that BMV RNA polymerase initiates binding with an RNA template through a mechanism mediated by the tRNA-like 3 end of BMV RNA, requiring at least some of the last 39, but no more than the last 153 bases.     

互补引物/模板评价毕加酵母表达的丙型肝炎病毒RNA依赖的RNA聚合酶

构建含有感染性克隆HCV非结构基因5b区序列的酵母表达质粒,转化毕加酵母,获得持续、可溶性HCV RNA依赖的RNA聚合酶(RdRp)的表达,纯化蛋白在SDS-PAGE及Western blot中显示出特异性的64.2kD HCV RdRp蛋白带,同聚引物/模板测定显示RdRp的活性极低,延长反应时间,RNA聚合活性仅轻度升高.采用合成的杂聚互补引物/模板,未发现核苷酸在毕加酵母表达的RdRp作用下掺入模板,随时间延长,杂聚互补引物/模板降解.     

人呼吸道合胞病毒微型复制子的构建

摘要：【目的】构建RSV微型复制子（minireplicon）并进行功能学研究。【方法】构建含RSV病毒前导序列（Leader, genomic promoter, Le）、转录起始信号（gene start, GS）、多克隆酶切位点、转录终止信号（gene end, GE）和尾随序列(Trailer, antigenomic promoter, Tr)的基因片段GSGE,通过引入T7 RNA多聚酶（T7 RNA polymerase, T7 RNP）启动子、克隆入载体px8δT和插入增强型绿色荧光蛋白（Enhanced Green Fluorescent Protein, EGFP）等多步操作,获得RSV微型复制子重组质粒px8δT/GSGE1/EGFP和px8δT/GSGE2/EGFP。同时构建可表达大蛋白（large protein,L）的质粒pcDNA3.1/L及表达转录延长/转录终止抑制因子（M2 ORF 1 protein,M2-1）的质粒pcDNA3.1/M2-1。通过脂质体法共转染RSV微型复制子质粒及四种RSV核壳体蛋白质粒至可表达T7 RNP的BSRT7/5细胞系,倒置荧光显微镜及流式细胞仪分析EGFP的表达情况。【结果】成功构建了px8δT/GSGE1/EGFP和px8δT/GSGE2/EGFP及pcDNA3.1/L和pcDNA3.1/M2-1,五质粒共转染BSRT7/5细胞,倒置荧光显微镜及流式细胞仪均观察到绿色荧光的表达。【结论】构建的RSV微型复制子具有转录和复制功能,将有助于进一步开展以RSV反向遗传操作为基础的RSV疫苗研究。