登革病毒2型全长cDNA感染性转录体的构建和鉴定

为构建登革病毒感染性克隆, 针对登革病毒2型基因组全长cDNA的体外转录方法及感染性转录体进行研究。采用长链RT-PCR技术, 扩增DEN2 NGC株全长基因组cDNA, 以之为模板, 用SP6 RNA聚合酶系统制备体外转录RNA转录体, 分别经乳鼠脑内接种及电穿孔转染BHK-21细胞, 观察其感染效应。并从受染鼠脑和病变细胞中提取总RNA, 进行RT-PCR扩增、克隆测序以及电镜观察。结果发现, 从感染鼠脑和细胞中经RT-PCR均可扩增出病毒特异的基因片段, 大小与预期一致; 并从乳鼠脑组织和BHK-21细胞中观察到恢复病毒颗粒。上述结果表明本文成功构建的DEN2 NGC株病毒全长cDNA的体外转录体具有感染性, 乳鼠脑内接种途径与电穿孔转染细胞一样可成为体外转录体感染宿主细胞、获得恢复病毒的方法。     

RNA病毒感染性转录体的制备

构建感染性转录体已成为研究ＲＮＡ病毒复制,表达,致病机制等的有力工具。感染性转录体可通过ｃＤＮＡ克隆经体内或体外转录获得,也可通过聚合酶链反应（ＰＣＲ）扩增产物直接转录获取。ＤＮＡ聚合酶引起的点突变、ｃＤＮＡ克隆的稳定性,转录体长度多态性、病毒基因组的５‘和３’端序列等均可影响转录体的感染性。     

乙脑病毒全长cDNA的扩增克隆及体外转录制备感染性RNA的研究

本研究根据已知的乙脑病毒(JEV)SA14株基因序列设计一套引物 ,利用长模板RT-PCR 技术,一次扩增出了JEV的全长cDNA,并采用大片段克隆技术将其克隆于载体的RNA聚合酶启动子下游.阳性克隆转录的RNA转染HBK细胞后细胞产生病变,经乳鼠脑内接种及特异性免疫荧光染色证明为JEV,这一结果表明JEV感染性克隆的构建获得了成功.其次,合成一条含有 RNA聚合酶启动子序列的5′引物,利用长模板RT-PCR方法扩增出带有启动子的JEV全长cDNA ,以此cDNA为模板作体外转录.转录产物转染BHK细胞后观察到了典型的JEV病变.收获的病毒经乳鼠脑内接种及免疫荧光染色证明为JEV,从而建立了制备JEV感染性RNA的快捷方法.本研究构建的JEV感染性克隆与建立的长模板RT-PCR快速制备JEV感染性RNA的方法,将为JEV 分子生物学研究的后续工作提供有力的工具和奠定坚实的基础.     

乙脑病毒全长cDNA的扩增克隆及体外转录制备感染性RNA的研究

本研究根据已知的乙脑病毒（ＪＥＶ）ＳＡ１４株基因序列设计一套引物,利用长模板ＲＴ－ＰＣＲ技术,一次扩增出了ＪＥＶ的全长ｃＤＮＡ,并采用大片段克隆技术将其克隆于载体的ＲＮＡ聚合酶启动子下游。阳性克隆转录的ＲＮＡ转染ＨＢＫ细胞后细胞产生病变,经乳鼠脑内接种及特异性免疫荧光染色证明为ＪＥＶ,这一结果表明ＪＥＶ感染性克隆的构建获得了成功。其次,合成一条含有ＲＮＡ聚合酶启动子序列的５′引物,利用长模板ＲＴ－     

型内嵌合口蹄疫病毒全长感染性cDNA克隆的构建

【目的】近年来,O型口蹄疫的不断暴发严重危害了我国畜牧业的发展,其病原——O型口蹄疫病毒已演化出3种谱系:中国型猪毒系、泛亚系和缅甸98系。其中中国型猪毒系病毒高度嗜猪,对养猪业危害最大。目前应用的疫苗已不能有效保护中国型猪毒系变异株的流行,这给我国猪口蹄疫的防控带来了极大的困难。为了进一步发展免疫原性好、抗原谱广的猪O型口蹄疫疫苗候选株,本研究以O/HN/93现用疫苗毒株的感染性克隆为骨架,用流行的新猪毒系病毒的部分VP3和VP1基因(主要是替换VP1蛋白上的B-C环和G-H环)替换疫苗毒株的相应部分,构建了嵌合的FMDV全长cDNA克隆。【方法】线化的嵌合全长质粒和表达T7 RNA聚合酶的真核质粒pcDNAT7P共转染BHK-21细胞,体内转录拯救嵌合病毒。【结果】嵌合全长质粒转染BHK-21细胞36h后,出现明显的FMDV致细胞病变效应。对收获的病毒分别用RT-PCR、间接免疫荧光、电子显微镜观察结果证实成功拯救到嵌合的FMDV。拯救的病毒乳鼠致病性试验结果表明该拯救病毒对乳鼠的致病力减弱。该嵌合病毒的成功拯救为研制口蹄疫新型疫苗等奠定了基础。     

猪瘟病毒感染性cDNA克隆的构建及其致病性

为了建立研究猪瘟病毒的技术平台,利用RT-PCR技术构建了猪瘟病毒中国石门株(Shimen)的全长有感染性cDNA克隆pT7SM。通过体外转录线性化的pT7SM并将转录的RNA转染至PK-15细胞中,获得了猪瘟病毒粒子。再用间接免疫荧光法测定了其生长曲线,通过电镜观察到重组病毒呈球形,具有囊膜结构。进一步把获得的猪瘟病毒粒子感染非免疫实验猪,结果子代病毒与石门株类似,对非免疫实验猪有强烈的致病性,证明该全长cDNA克隆可靠稳定,忠实地保留了石门株病毒的感染性和致病特征。由此为进一步探讨猪瘟病毒的致弱机制及病毒与机体相互作用的机制打下了良好的基础。     

猪瘟病毒兔化弱毒株全长cDNA克隆的感染性鉴定

用SrfⅠ限制性内切酶将构建的猪瘟病毒兔化弱毒株(C-株)全长cDNA线性化,体外转录获得其基因组RNA,利用脂质体将基因组RNA转染至SK-6细胞系,连续传代,收集5代以后培养细胞,采用RT-PCR、荧光抗体直接法、夹心ELISA进行鉴定.结果表明,所构建的全长cDNA具有感染性.猪瘟病毒C-株全长感染性cDNA的成功构建,为在分子水平上进一步研究中国猪瘟病毒兔化弱毒株提供了极有价值的研究工具.     

HCV5′端非编码区cDNA的体外转录

采用逆转录聚合酶链反应（ＲＴ－ＰＣＲ）从广东省一例慢性丙型肝炎病人血清中获得丙型肝炎病毒（ＨＣＶ）５′端非编码区（５′ＮＣＲ）３０２ｂｐ的ｃＤＮＡ片段,经补齐和提纯后插入ｐＵＣ１９质粒,获得的重组体ｐＵＮ进行序列测定,将ｐＵＮ的目的基因亚克隆进体外转录载体ｐＳＰＯＲＴＩ多克隆位点的ＥｃｏＲｆｆＩ和ＰｓｔＩ切点之间,所得重组体ｐＳＮ线性化后由Ｔ７ＲＮＡ多聚酶及ＳＰ６ＲＮＡ多聚酶引导体外转录反应,产物     

Immunopathogenesis of dengue virus infection

Dengue virus infection causes dengue fever (DF), dengue hemorrhagic fever (DHF), and dengue shock syndrome (DSS), whose pathogeneses are not clearly understood. Current hypotheses of antibody-dependent enhancement, virus virulence, and IFN-gamma/TNFalpha-mediated immunopathogenesis are insufficient to explain clinical manifestations of DHF/DSS such as thrombocytopenia and hemoconcentration. Dengue virus infection induces transient immune aberrant activation of CD4/CD8 ratio inversion and cytokine overproduction, and infection of endothelial cells and hepatocytes causes apoptosis and dysfunction of these cells. The coagulation and fibrinolysis systems are also activated after dengue virus infection. We propose a new hypothesis for the immunopathogenesis for dengue virus infection. The aberrant immune responses not only impair the immune response to clear the virus, but also result in overproduction of cytokines that affect monocytes, endothelial cells, and hepatocytes. Platelets are destroyed by crossreactive anti-platelet autoantibodies. Dengue-virus-induced vasculopathy and coagulopathy must be involved in the pathogenesis of hemorrhage, and the unbalance between coagulation and fibrinolysis activation increases the likelihood of severe hemorrhage in DHF/DSS. Hemostasis is maintained unless the dysregulation of coagulation and fibrinolysis persists. The overproduced IL-6 might play a crucial role in the enhanced production of anti-platelet or anti-endothelial cell autoantibodies, elevated levels of tPA, as well as a deficiency in coagulation. Capillary leakage is triggered by the dengue virus itself or by antibodies to its antigens. This immunopathogenesis of DHF/DSS can account for specific characteristics of clinical, pathologic, and epidemiological observations in dengue virus infection.     

Structural proteomics of dengue virus

In this paper, we discuss recent advances in our knowledge of the dengue virus life cycle based on new structural data of the virus and its proteins. Specifically, we focus on the structure of the pre-membrane protein, prM and its role in virus assembly, the first full-length structure of a multi-domain dengue virus replication protein, NS3, and the recently solved structures of NS5 methyltransferase and polymerase domains. These structures provide a basis for describing function and predicting putative host interactions.     

Study on immunity of dengue virus and dengue vaccine development

In the study of vaccines for dengue viruses, which are multivalent immunization, genetically and antigenically distinct, we should have more sophisticated understanding of viral immune physiology. Because the immune response to dengue and its role in the pathophysiology of dengue fever and dengue hemorrhagic fever are multifaceted, several different efforts have been made to engineer a protective vaccine. Because of space limitations, this review is focused only on vaccines that have emerged from preclinical studies into clinical trial.     

Study on immunity of dengue virus and dengue vaccine development

In the study of vaccines for dengue viruses,which are multivalent immunization,genetically and antigenically distinct,we should have more sophisticated understanding of viral immune physiology.Because the immune response to dengue and its role in the pathophysiology of dengue fever and dengue hemorrhagic fever are multifaceted,several different efforts have been made to engineer a protective vaccine.Because of space limitations,this review is focused only on vaccines that have emerged from preclinical studies into clinical trial.     

Antibody response to dengue virus

In this review, we discuss the current knowledge of the role of the antibody response against dengue virus and highlight novel insights into targets recognized by the human antibody response. We also discuss how the balance of pathological and protective antibody responses in the host critically influences clinical aspects of the disease.     

登革病毒受体的研究进展

登革病毒(Dengue virus,DENV)是登革热(DF)、登革出血热和登革休克综合征(DHF/DSS)的病原体.根据包膜蛋白的抗原性的不同,DENV可分为4个血清型,即DENV1～4.由于血清型比较复杂,目前关于病毒受体仍未得出明确一致的结论.但近几年取得了一些引人注目的进展,比如研究发现甘露糖受体(MR)、CLEC5A等作为DENV的受体,可能在病毒进入宿主细胞过程中发挥重要作用.为此,就近几年关于DENV受体以及病毒进入细胞的机制作一综述.     

Selection-driven evolution of emergent dengue virus

In the last four decades the incidence of dengue fever has increased 30-fold worldwide, and over half the world's population is now threatened with infection from one or more of four co-circulating viral serotypes (DEN-1 through DEN-4). To determine the role of viral molecular evolution in emergent disease dynamics, we sequenced 40% of the genome of 82 DEN-4 isolates collected from Puerto Rico over the 20 years since the onset of endemic dengue on the island. Isolates were derived from years with varying levels of DEN-4 prevalence. Over our sampling period there were marked evolutionary shifts in DEN-4 viral populations circulating in Puerto Rico; viral lineages were temporally clustered and the most common genotype at a particular sampling time often arose from a previously rare lineage. Expressed changes in structural genes did not appear to drive this lineage turnover, even though these regions include primary determinants of viral antigenic properties. Instead, recent dengue evolution can be attributed in part to positive selection on the nonstructural gene 2A (NS2A), whose functions may include replication efficiency and antigenicity. During the latest and most severe DEN-4 epidemic in Puerto Rico, in 1998, viruses were distinguished by three amino acid changes in NS2A that were fixed far faster than expected by drift alone. Our study therefore demonstrates viral genetic turnover within a focal population and the potential importance of adaptive evolution in viral epidemic expansion.