禽流感病毒H5N1亚型NS1基因在大肠杆菌中的表达

目的表达H5N1亚型禽流感病毒(AIV)NS1蛋白,用于AIV感染与注射灭活疫苗鸡的鉴别诊断和NS1蛋白功能研究。方法采用RT_PCR方法对H5N1亚型AIVNS1基因进行扩增,将PCR产物克隆于pGEM_T_easy载体,将该基因插入pGEX_4T_1中构建NS1基因原核表达载体,转化BL21大肠杆菌后,在IPTG诱导下表达NS1蛋白,Westernblot鉴定表达NS1蛋白。结果成功克隆H5N1亚型AIV的NS1基因,其核苷酸序列长度为690bp,编码230个氨基酸残基。构建NS1基因原核表达载体在大肠杆菌内表达出约51×103的NS1融合蛋白。Westernblot鉴定表明表达NS1蛋白与H7N2AIV感染鸡血清有反应性。结论在大肠杆菌中成功表达了H5N1亚型AIVNS1基因蛋白,具有与感染H7N2亚型AIV阳性血清反应原性。     

H1亚型猪流感病毒血凝素基因在昆虫细胞中的表达及其间接ELISA方法的初步建立

根据GenBank发表的H1亚型猪流感HA基因序列设计引物,扩增出HA基因片段,将其克隆到pFastBacGP67B杆状病毒载体上,筛选阳性重组转座载体pFastBacGP67B-H1,转化含有杆状病毒穿梭载体(bacmid)的DH10Bac感受态细胞,构建杆状病毒表达载体获得重组转座子(rBacmid-H1),在脂质体介导下转染sf9昆虫细胞,获得重组杆状病毒(rBV-H1),再感染细胞,收获目的蛋白。通过血凝试验、免疫印迹法、免疫组化分析表明该蛋白得到表达,且具有良好的生物学活性。利用表达的蛋白作为猪流感间接ELISA的抗原,初步建立H1亚型猪流感的间接ELISA检测方法,并对内蒙古、辽宁和黑龙江等地送检的93份猪血清进行了检测,阳性率为31.18%,为研制开发快速、准确、简便的H1亚型猪流感鉴别诊断试剂盒奠定基础。     

H5N1禽流感病毒HA基因在昆虫细胞中的表达及生物活性鉴定

经RT-PCR扩增了H5N1亚型禽流感病毒血凝素基因(HA)片断,限制性内切酶酶切后将其克隆到pFastBacHTA杆状病毒转座载体,经酶切鉴定及测序,筛选出阳性重组转座载体pFastBac-H5。将pFastBacH5转化含有杆状病毒穿梭载体（bacmid）的DH10Bac感受态细胞,通过蓝白斑筛选和PCR鉴定获得重组杆状病毒穿梭载体rBacmid-H5。rBacmid-H5在脂质体介导下转染sf9昆虫细胞,SDS－PAGE蛋白电泳、Western blot、血凝试验和血凝抑制试验分析表明：分子量约63Kd重组血凝素蛋白（rH5）在sf9昆虫细胞中实现了高效表达。rH5具有血凝活性,而且其血凝活性能够被H5N1禽流感病毒高免血清所抑制;rH5免疫鸡诱导产生针对H5N1禽流感病毒亚型特异的血凝抑制抗体,说明表达的重组蛋白具有与天然蛋白相似的生物活性。     

H5N1亚型禽流感病毒NS1基因在昆虫细胞中的表达

将H5N1亚型禽流感病毒（AIV）NS1基因插入到杆状病毒转移载体pFastBac1中,获得重组转移载体pFastBac1- NS1。将pFastBac1- NS1转化到DH10Bac感受态细胞中,筛选到重组转座子rBacmid-NS1。在脂质体转染试剂介导下将rBacmid-NS1转染对数生长期的Sf9昆虫细胞获得重组杆状病毒rBV-NS1。rBV-NS1感染Sf9细胞后,通过SDS-PAGE、Western blot和ELISA分析表明：获得了分子量为26ku的特异性NS1蛋白;并且该蛋白可与H5N1 AIV攻毒鸭的血清发生特异性免疫反应,而不能与H5N1AIV灭活疫苗免疫鸭的血清发生反应。试验结果表明：NS1在Sf9昆虫细胞中获得了高效表达,具有与天然蛋白相似的免疫活性,并可以作为区分免疫及自然感染个体的鉴别诊断抗原。本实验为建立禽流感病毒自然感染家禽与禽流感灭活苗免疫家禽的鉴别诊断方法奠定基础。     

H1亚型猪流感病毒血凝素基因在昆虫细胞中的表达及其间接

根据GenBank发表的H1亚型猪流感HA基因序列设计引物,扩增出HA基因片段.将其克隆到pFastBacGP67B杆状病毒载体上,筛选阳性重组转座载体pFastBacGP67B-H1,转化含有杆状病毒穿梭载体(bacmid)的DH10Bac感受态细胞,构建杆状病毒表达载体获得重组转座子(rBacmid-H1),在脂质体介导下转染sf9昆虫细胞,获得重组杆状病毒(rBV-H1),再感染细胞,收获目的蛋白.通过血凝试验、免疫印迹法、免疫组化分析表明该蛋白得到表达,且具有良好的生物学活性.利用表达的蛋白作为猪流感间接ELISA的抗原,初步建立H1亚型猪流感的间接ELISA检测方法,并对内蒙古、辽宁和黑龙江等地送检的93份猪血清进行了检测,阳性率为31.18%,为研制开发快速、准确、简便的H1亚型猪流感鉴别诊断试剂盒奠定基础.     

H5N1亚型禽流感病毒血凝素蛋白单链抗体基因的克隆及表达

构建并表达H5N1亚型禽流感病毒血凝素蛋白单链抗体,为禽流感靶向治疗药物的研制制备靶向载体。从分泌血凝素单克隆抗体的杂交瘤细胞株中提取mRNA,采用RT-PCR法扩增出重链和轻链可变区基因,通过SOE-PCR法将重链和轻链通过Linker连接起来构建单链抗体基因,将获得的单链抗体基因装入原核表达载体pET28a(+)中,构建重组质粒并表达,以Western blot鉴定单链抗体的特异性。结果成功构建了单链抗体基因,全长714bp,经原核表达,所构建的单链抗体可与H5亚型禽流感病毒HA蛋白特异结合,为禽流感的靶向治疗奠定了基础。     

H5N1亚型禽流感病毒神经氨酸酶基因的克隆与表达

根据已知H5N1亚型禽流感病毒神经氨酸酶基因(na)序列设计、合成克隆引物。自H5N1亚型病毒感染的鸡胚尿囊液中提取总RNA,反转录后采用高可信度DNA聚合酶(PyobestTMDNAPolymerase)扩增na基因,采用Invitrogen定向表达系统(ChampionTMpETdirectionalTOPOexpressionsystem)进行克隆表达,纯化获得N末端携带多聚组氨酸标签的重组神经氨酸酶,分子量约53.8kDa。分析重组NA的免疫反应性和免疫原性,结果表明:重组NA能与H5N1亚型病毒抗血清发生特异性结合,且其免异动物后能诱导机体产生特异性抗体,具有良好的抗原性。     

H5N1亚型禽流感病毒神经氨酸酶基因的克隆与表达

根据已知H5N1亚型禽流感病毒神经氨酸酶基因(na)序列设计、合成克隆引物.自H5N1亚型病毒感染的鸡胚尿囊液中提取总RNA,反转录后采用高可信度DNA聚合酶(PyobestTMDNAPolymerase)扩增na基因,采用Invitrogen定向表达系统(ChampionTM pET directional TOPO expression system)进行克隆表达,纯化获得N末端携带多聚组氨酸标签的重组神经氨酸酶,分子量约53.8kDa.分析重组NA的免疫反应性和免疫原性,结果表明重组NA能与H5N1亚型病毒抗血清发生特异性结合,且其免异动物后能诱导机体产生特异性抗体,具有良好的抗原性.     

H5N1亚型高致病性禽流感病毒NS1基因的克隆及其序列分析

目的：克隆H5N1亚型禽流感病毒的NS1基因,并分析其序列特性。方法：通过RT-PCR方法克隆H5N1亚型禽流感病毒NS1基因,并对该基因片段进行测序,将此序列与数据库中不同时间、地点、宿主来源的H5N1亚型流感毒株NS1基因序列进行同源性比较。结果：获得了678bp的NS1全长基因,可编码225个氨基酸;其与毒株A／chicken／Jilin／hq／2003的同源性最高,二者的核酸和氨基酸的同源性分别为99．7％和99．1％。比对分析发现,该毒株NS1基因在第238-252位有15个核苷酸的缺失;进化树分析表明,它与1997年香港流行的H5N1亚型禽流感病毒毒株分别属于2个不同的分支。结论：克隆了一株H5N1亚型禽流感病毒的NS1基因,并初步分析了其序列特性,为进一步研究NS1基因的功能奠定了基础。     

H7N9亚型禽流感病毒非结构蛋白1(NS1)基因序列分析及2013上海分离株NS1的原核表达

目的:对2013年3月发生的感染人的新型H7N9亚型禽流感病毒的非结构蛋白1(NS1)基因序列进行同源性分析,构建NS1重组质粒并表达。方法:从GenBank获得2006~2013年不同来源的H7N9亚型病毒NS1序列,并进行同源性比较;利用PCR方法从H7N9亚型禽流感病毒株A/Shanghai/4664T/2013(H7N9)基因组cDNA中扩增得到全长NS1基因,并将该片段定向克隆到原核表达载体pET28a上,构建重组质粒pET28a-NS1,经酶切鉴定,将重组质粒转化大肠杆菌BL21(DE3)感受态细胞后,IPTG诱导表达,且进行Western印迹分析。结果:经序列分析,2013年暴发的H7N9型禽流感病毒的NS1基因核苷酸序列同源性为95%~100%,与之前暴发的H7N9型流感病毒NS1基因序列的同源性为86.4%~90.7%,表明2次暴发的该型流感分离株属于不同的进化分支;PCR扩增得到约680 bp的NS1基因序列,所克隆的NS1基因在原核细胞中的表达产物主要以包涵体形式存在,SDS-PAGE检测结果表明重组蛋白相对分子质量为25×103,Western印迹分析证实表达产物为H7N9禽流感病毒NS1蛋白。结论:为进一步研究H7N9亚型流感病毒NS1蛋白功能及基于NS1蛋白的抗病毒药物奠定了基础。     

H9N2亚型禽流感病毒非结构蛋白(NS1)基因的克隆与表达

由于H9N2亚型禽流感对我国的养鸡业已造成了很大的损失,因而在我国许多养鸡场不得不使用H9N2亚型禽流感灭活苗[1],但由于灭活苗的使用,而增加了H9N2亚型禽流感的监测难度.因此,建立一种能区别自然感染鸡和疫苗免疫鸡的鉴别诊断方法已被提到日程上来.     

H9N2亚型禽流感病毒非结构蛋白（NS1）基因的克隆与表达

The nostructural protein (NS1) encoded by gene 8 of the Influenza virus is present in cells infected with Influenza virus. In this study, NS1 protein gene of the Chicken influenza virus A/chicken/Beijing/2/97 (H9N2) strain was amplified by PCR. The fragment contains EcoR Ⅰ and Xho Ⅰ restriction enzyme sites at the ends. The amplified product was cloned into the expression vector pET-30(c). Recombinant plasmid pET/NS 1 was transformed into E.coli BL21 (DE3) competent cells and induced with 0.4 mmol/L IPTG the target protein was produced, the molecular weight of the expressed protein was 30 kDa as expected. Western-blot test indicated that the expressed protein can react with the NS 1 monoclonal antibody of the influenza virus. This study laid an important foundation for H9N2 subtype avian influenza surveillance in China.     

Hemagglutinin-Dependent Tropism of H5N1 Avian Influenza Virus for Human Endothelial Cells

Although current H5N1 highly pathogenic avian influenza viruses (HPAIV) are inefficiently transmitted to humans, infected individuals can suffer from severe disease, often progressing rapidly to acute respiratory distress syndrome and multiorgan failure. This is in contrast with the situation with human influenza viruses, which in immunocompetent individuals usually cause only a respiratory disease which is less aggressive than that observed with avian H5N1 viruses. While the biological basis of inefficient transmission is well documented, the mechanisms by which the H5N1 viruses cause fatal disease remain unclear. In the present study, we demonstrate that human pulmonary microvascular endothelial cells (hPMEC) had a clearly higher susceptibility to infection by H5N1 HPAIV than to infection by human influenza viruses. This was measurable by de novo intracellular nucleoprotein production and virus replication. It was also related to a relatively higher binding capacity to cellular receptors. After infection of hPMEC, cell activation markers E-selectin and P-selectin were upregulated, and the proinflammatory cytokines interleukin-6 and beta interferon were secreted. H5N1 virus infection was also associated with an elevated rate of cell death. Reverse genetics analyses demonstrated a major role for the viral hemagglutinin in this cell tropism. Overall, avian H5N1 viruses have a particular receptor specificity targeting endothelial cells that is different from human influenza viruses, and this H5N1 receptor specificity could contribute to disease pathogenesis.Certain highly pathogenic avian influenza viruses (HPAIV) expressing the H5 and H7 hemagglutinins (HA) have acquired the capacity to infect humans. Particularly, HPAIV with the H5 HA and the neuraminidase (NA) type 1 (H5N1) can cause severe disease, often with a fatal outcome in humans and other mammals (27). With such infections in humans, there are two striking differences compared to infection by human influenza A viruses (IAV). First, bird-to-human and human-to-human transmission has been considered inefficient, and second, the mortality rate of H5N1 virus infections has been unexpectedly high. There is a lot of experimental evidence that inefficient transmission rate is related to several viral gene products not optimally adapted to facilitate infection and replication in the primary target cells, the epithelial cells of the respiratory tract. Of particular importance is the HA determining receptor specificity with human viruses preferentially recognizing sialic acid (SA)-α-2,6-Gal-terminated saccharides (α-2,6-SA), abundantly expressed in the upper respiratory tract, and avian viruses preferentially binding to α-2,3-SA, expressed mainly in the lower respiratory tract and on ciliated epithelial cells (23, 33, 39). In addition, the viral polymerases determining the rate of replication as well as the NS1 protein involved in multiple processes enabling efficient viral replication and evasion of cellular antiviral responses are of importance in determining host tropism (17, 26).However, in contrast to infections with human influenza viruses, avian H5N1 virus infections more often cause severe pneumonia. These are associated with high levels of proinflammatory cytokines and chemokines in the respiratory tract, severe inflammatory reactions, and infiltration of leukocytes. Furthermore, a generalized inflammatory reaction with elevated cytokine and chemokine levels in the circulation, together with leukopenia and multiorgan failure, indicates that an aberrant immunological reaction is an important factor contributing to the fatality of H5N1 virus infections (19). This is supported by in vitro studies of human macrophages, dendritic cells, and epithelial cells, in which it was demonstrated that H5N1 viruses can induce higher levels of inflammatory cytokine and chemokine responses than human IV isolates (2, 3, 37). Based on this, it was proposed that factors of the innate and adaptive immune response are of central importance for the outcome of disease (8, 26).Endothelial cells (EDC) are abundant in all organs, particularly the lung, and play an important role in inflammatory processes through the regulation of leukocyte extravasation, the production of inflammatory cytokines and chemokines, and the regulation of coagulation (4). During systemic disease in chickens infected with H5N1 isolates, the cardiovascular system can be affected with coagulopathy and viral antigen detectable in EDC (15, 25, 36). This also relates to a report demonstrating a targeted infection of EDC in chicken embryo by A/FPV/Rostock/34 (H7N1) virus (6). In this study, the infection of human umbilical vein EDC is also reported. Finally, in humans, various degrees of hemorrhages as well as signs of disseminated intravascular coagulation have been found (1).Accordingly, the present study compared influenza virus isolates of avian and human origin with respect to their characteristics of interaction with human EDC. To this end, we infected primary human lung EDC with different naturally occurring virus isolates as well as viruses created by reverse genetics. Viruses expressing the H5 clearly possessed the greatest potency to infect and replicate in EDC, resulting in activation and inflammatory responses.