H5N1禽流感病毒HA假病毒的构建及特性研究

目的 构建包膜蛋白为H5N1禽流感病毒HA蛋白的假病毒,对其生物学特性进行研究,并将其初步应用于H5N1禽流感病毒的血清检测.方法 将我国分离的高致病性H5N1禽流感病毒的HA基因插入真核表达质粒,得到pLP-HA,与假病毒构建体系的三种质粒pLP1,pLF2和pEmGFP,瞬时共转染人胚肾细胞293T,48 h收集假病毒上清,对其感染性,血凝活性进行测定,并应用于微量中和实验.同时,构建了优化HA基因的假病毒以及一株含有越南禽流感病毒HA基因的假病毒,进行比较.结果 电镜下观察到假病毒颗粒的存在;Western-Blot表明HA蛋白存在于假病毒颗粒中;HA假病毒与野生型活病毒的微量中和实验相比,两者结果具有很好的相关性.结论 成功构建了不同高致病性H5N1禽流感病毒HA蛋白的假病毒,所构建的假病毒可以应用于微量中和实验.研究发现不同禽流感病毒株HA蛋白假病毒的包装效率不同,并且真核表达优化基因并不能显著提高假病毒颗粒包装效率.     

H5N1禽流感病毒headless HA基因在杆状病毒中的表达

目的 建立能有效表达禽流感病毒A/Hubei/1/2010( H5N1)无头HA( headless HA)的杆状病毒系统.方法 利用RT-PCR扩增获得headless HA基因,克隆至杆状病毒转移载体pFastBac1,命名为pFastBac1headless HA.将pFastBac1headless HA转化到DH10Bac感受态细胞,获得重组穿梭质粒Headless HA-Bac.利用Bac-to-Bac杆状病毒表达系统,转染Sf9昆虫细胞,获得重组杆状病毒,并进行Western Blot和红细胞凝集试验检测.结果 Headless HA在Sf9细胞中能有效表达,不能使红细胞发生凝集.结论 本研究为利用headless HA表达蛋白研制广谱流感疫苗奠定了基础.     

中国人感染H5N1亚型高致病性禽流感病例病毒分离培养探讨

目的 分析中国大陆人感染H5N1高致病性禽流感病例标本采集和病毒分离培养之间的关系.方法 对2005年10月至2009年3月中国大陆人感染H5N1高致病性禽流感病例标本进行病毒分离培养.结果 标本采集时间主要集中在发病后的0～14 d,其中0～7 d采样的标本阳性率分布相对集中,病毒分离的效果要更加显著;标本采集类型主要为呼吸道标本,其中下呼吸道标本的病毒分离阳性率分布较集中,病毒分离效果也更明显.结论 人禽流感病例标本采集时间及标本的采集类型对病毒分离有一定的影响,应在发病的急性期侧重于采集下呼吸道标本,这样利于提高病毒分离的阳性率.     

H9N2禽流感病毒反向遗传系统的构建和鉴定

目的 建立H9N2亚型禽流感病毒反向遗传系统,为人禽流感疫苗研制以及传播和致病机制等方面的研究提供技术平台.方法 使用RT-PCR方法获得禽流感H9N2亚型病毒A/Guangzhou/333/99(H9N2)的8条全长基因节段,然后克隆到双表达载体pCI-pol Ⅰ中,获得H9N2禽流感病毒的8个基因节段的8质粒系统.将构建好的8质粒共转染293T细胞后,收获上清接种鸡胚,然后对鸡胚尿囊液进行鉴定;对拯救的病毒进行鉴定.结果 8质粒系统转染293T细胞后可以成功拯救出H9N2禽流感病毒,血凝效价可达到29/50μl,生长特性与野生型病毒类似.结论 成功建立了H9N2禽流感病毒反向遗传系统.     

中国职业暴露人群感染H6N6禽流感病毒血清学调查

目的 系统评估我国职业暴露人群感染H6N6禽流感病毒的状况.方法 本研究利用我国2009-2011年开展的高致病性H5N1禽流感病毒职业暴露人群血清学监测所采集的近15 000份血清标本,开展H6N6禽流感病毒血清学调查.结果 本研究中检测到H6N6禽流感病毒阳性血清共10份,分别来自不同的职业暴露人群,包括活禽市场、家禽规模养殖场、家禽散养户、屠宰加工场和野生候鸟栖息地.从地域上看该10份阳性血清来自8个不同的省份,分布在我国的南北方.结论 这是我国大陆地区首次报道人感染H6亚型禽流感病毒.     

甲型H1N1流感病毒非结构蛋白NS1真核表达载体的构建与表达

目的:构建甲型H1N1流感病毒非结构蛋白NS1真核表达载体并表达其编码蛋白(转染293T细胞)。方法:从江苏首例甲型H1N1流感病毒毒株(A/Nan jing/1/2009(H1N1))提取病毒RNA,采用RT-PCR技术扩增NS1全长基因,将其克隆至pMD18-T Vector中构建pMD18-T-NS1质粒,双酶切pMD18-T-NS1与PXJ40-HA后,构建真核表达载体PXJ40-HA-NS1,经酶切及测序鉴定后将质粒转染到293T细胞中,通过Western blot鉴定NS1蛋白的表达。结果:经双酶切、测序鉴定证实NS1基因的真核表达载体构建成功。West-ern blot法可见NS1基因编码蛋白的成功表达。结论:成功克隆NS1全长基因,并构建了其真核表达载体,该表达载体的构建为后期建立稳定表达NS1蛋白的细胞模型和NS1蛋白功能研究提供了材料。     

含H5N1-HA基因重组腺病毒疫苗的构建及其诱导免疫应答的初步探讨

目的 构建包含H5N1-HA基因的重组腺病毒疫苗并探讨其免疫效果.方法 用Admax系统构建包含H5N1-HA基因的重组腺病毒疫苗,并用PCR、Western-Blot等方法对重组病毒疫苗进行鉴定;疫苗免疫小鼠后,通过HI实验和ELISPOT实验检测其体液免疫和细胞免疫反应,评价其免疫效果.结果 成功得到了含有H5N1-HA基因的重组腺病毒疫苗;基因表达鉴定表明,HA基因能够在细胞中进行表达;血凝抑制实验结果显示小鼠产生的针对HA抗体滴度在1:320和1:640之间;ELISPOT结果显示实验组和对照组(PBS)相比斑点数量差异有统计学意义(P<0.05),以上免疫结果表明重组腺病毒载体疫苗可以诱导小鼠产生良好的特异性体液和细胞免疫反应.结论 含H5NA-HA的重组腺病毒疫苗可以诱导小鼠产生良好的免疫反应,为研制人禽流感疫苗打下基础.     

高致病性禽流感病毒H5N1安徽株A/Anhui/1/2005感染人肺癌上皮细胞(A549)的差异表达分析

目的 筛选人细胞中与高致病性禽流感病毒致病相关的基因,探讨高致病性禽流感病毒的致病机理.方法 分别用高致病性禽流感病毒安徽株和普通人流感病毒H1N1株分别感染人肺癌上皮细胞,通过人类全基因表达谱芯片技术对不同时段感染细胞进行差异表达分析,筛选出与高致病性禽流感病毒感染相关的候选基因,以实时定量荧光PCR法验证差异表达基因.结果 获得了不同致病性流感病毒感染细胞后的差异表达谱,验证了细胞凋亡通路、mTOR通路中以及与免疫相关的16个基因的差异表达.结论 H5N1感染后与普通人流感病毒H1N1相比具有促进细胞凋亡的趋势.     

人感染高致病性禽流感病毒H5N1的病理学和病原学特点

目的 探讨人感染禽流行性感冒病毒的病理学及病原学特点.方法 应用透射电镜、光镜、组织化学和免疫组织化学方法对发生在2003年11月中国内地人禽流感死亡尸检病例1例进行观察研究.行病原体分离培养鉴定、全基因组序列测定和动物致病性观察以确定病原学特点.结果 肺部病理改变主要表现为广泛性肺实变,肺出血、肺水肿及坏死.肺泡腔内充满水肿液、多量红细胞、纤维素,细胞碎片,混合较多的巨噬细胞和中性粒细胞及淋巴细胞,并见少数单核和多核巨细胞,伴有透明膜形成.部分肺组织出血坏死显著,肺泡隔坏死崩解.心肌间质水肿,少数淋巴细胞浸润.电镜下A型禽流感病毒样颗粒多为球形,80～120 nm,主要以高电子密度核心居中的C型病毒颗粒为多见,也可见到低电子密度核心的A型病毒颗粒.病毒分离及序列分析确定为A型禽流感病毒(H5N1).结论 高致病性A型禽流感病毒感染所致的严重急性病毒性肺炎以广泛性肺实变、肺水肿和显著的出血性坏死性炎症等病理改变为特征.电镜下查见A型禽流感病毒样颗粒.探讨和研究人禽流行性感冒的病理学和病原学特点,为人禽流感临床诊断和治疗方案的选择提供重要的理论依据和病理学基础.     

H5N1-NP蛋白的原核表达及与宿主蛋白相互作用的初步研究

目的 原核表达并纯化禽流感病毒A/Anhui/1/2005（H5N1）的NP蛋白,并筛选人支气管上皮BEAS-2B细胞总蛋白中能够与纯化的NP蛋白相互作用的蛋白.方法 一方面,构建了含有NP基因的原核表达质粒pET30a-NP,并在大肠埃希菌中获得了可溶性表达.亲和层析和离子交换层析两步对NP蛋白进行纯化.另一方面,制备了BEAS-2B细胞总蛋白.在此基础上,联合应用Pull-down与LC-MS/MS技术来筛选并确认细胞中与纯化的NP蛋白相互作用的成分.结果 构建的pET30a-NP质粒在IPTG诱导下在原核细胞中实现了可溶表达,经过两步纯化后,得到可溶的NP蛋白纯品.Pull-down与LC-MS/MS技术初步筛选到BEAS-2B细胞中20个可能与NP蛋白相互作用的细胞蛋白.还需要进一步的实验来验证他们和NP蛋白之间的相互作用.结论 获得了高纯度的可溶NP蛋白及筛选到20个可能与其相互作用的BEAS-2B细胞候选蛋白.     

H1N1亚型流感病毒在A549和BEAS-2B细胞中复制情况的初步研究

目的 探讨不同宿主来源的H1N1亚型流感病毒在A549和BEAS-2B细胞的复制情况.方法 用分离自人、禽、猪三种宿主的7株H1N1甲型流感病毒分别接种A549和BEAS-2B细胞,分析病毒感染细胞后不同时段的特点;应用受体类型不同的红细胞进行微量血凝试验,检测流感病毒的受体结合特性;同时检测了A549和BEAS-2B细胞表面的受体分布情况.结果 三种宿主来源的H1N1亚型流感病毒感染A549细胞,24 h后CPE十分明显,36 h病毒滴度达到最高值;而感染BEAS-2B细胞后,从24 h-120 h CPE都不是很明显,且所有病毒的病毒滴度都很低.对6株H1N1流感病毒的受体结合特性进行了筛查,发现部分测试病毒具有SA a-2,6Gal受体结合特异性.而A549和BEAS-2B细胞表面均含有SA a-2,3Gal及SA a-2,6Gal受体,且A549细胞表面糖受体含量明显高于BEAS-2B细胞.结论 不同宿主来源的H1N1亚型流感病毒对A549细胞都易感并能有效增殖复制,而对具有相似受体特性、上皮组织来源的BEAS-2B细胞不易感,提示支持流感病毒有效感染、复制存在宿主内的调节机制.     

Rescue of influenza virus expressing GFP from the NS1 reading frame

In this study, several influenza NS1 mutants were examined for their growth ability in interferon (IFN)-deficient Vero cells treated with human interferon alpha (IFN-alpha). Mutants with an intact RNA binding domain showed similar growth properties as the wild-type virus, whereas viruses carrying an impaired RNA binding domain were dramatically attenuated. Relying on the ability of the first half of the NS1 protein to antagonize the IFN action, we established a rescue system for the NS gene based on the transfection of one plasmid expressing recombinant NS vRNA and subsequent coinfection with an IFN sensitive helper virus followed by adding of human IFN-alpha as a selection drug. Using this method, a recombinant influenza A virus expressing green fluorescence protein (GFP) from the NS1 reading frame was rescued. To ensure the posttranslational cleavage of GFP from the N-terminal 125 amino acids (aa) of NS1 protein, a peptide sequence comprising a caspase recognition site (CRS) was inserted upstream the GFP protein. Although a rather long sequence of 275 aa was inserted into the NS1 reading frame, the rescued recombinant vector appeared to be genetically stable while passaging in Vero cells and was able to replicate in PKR knockout mice.     

CDK/ERK-mediated phosphorylation of the human influenza A virus NS1 protein at threonine-215

Posttranslational modification of viral proteins by cellular enzymes is a feature of many virus replication strategies. Here, we report that during infection the multifunctional human influenza A virus NS1 protein is phosphorylated at threonine-215. Substitution of alanine for threonine at this position reduced early viral propagation, an effect apparently unrelated to NS1 antagonizing host interferon responses or activating phosphoinositide 3-kinase signaling. In vitro, a subset of cellular proline-directed kinases, including cyclin dependent kinases (CDKs) and extracellular signal-regulated kinases (ERKs), potently phosphorylated NS1 protein at threonine-215. Our data suggest that CDK/ERK-mediated phosphorylation of NS1 at threonine-215 is important for efficient virus replication.     

A site on the influenza A virus NS1 protein mediates both inhibition of PKR activation and temporal regulation of viral RNA synthesis

It is not known how influenza A viruses, important human pathogens, counter PKR activation, a crucial host antiviral response. Here we elucidate this mechanism. We show that the direct binding of PKR to the NS1 protein in vitro that results in inhibition of PKR activation requires the NS1 123-127 amino acid sequence. To establish whether such direct binding of PKR to the NS1 protein is responsible for inhibiting PKR activation in infected cells, we generated recombinant influenza A/Udorn/72 viruses expressing NS1 proteins in which amino acids 123/124 or 126/127 are changed to alanines. In cells infected with these mutant viruses, PKR is activated, eIF-2alpha is phosphorylated and viral protein synthesis is inhibited, indicating that direct binding of PKR to the 123-127 sequence of the NS1 protein is necessary and sufficient to block PKR activation in influenza A virus-infected cells. Unexpectedly, the 123/124 mutant virus is not attenuated because reduced viral protein synthesis is offset by enhanced viral RNA synthesis at very early times of infection. These early viral RNAs include those synthesized predominantly at later times during wild-type virus infection, demonstrating that wild-type temporal regulation of viral RNA synthesis is absent in 123/124 virus-infected cells. Enhanced early viral RNA synthesis after 123/124 virus infection also occurs in mouse PKR-/- cells, demonstrating that PKR activation and deregulation of the time course of viral RNA synthesis are not coupled. These results indicate that the 123/124 site of the NS1A protein most likely functionally interacts with the viral polymerase to mediate temporal regulation of viral RNA synthesis. This interaction would occur in the nucleus, whereas PKR would bind to NS1A proteins in the cytoplasm prior to their import into the nucleus.     

Evolution of the NS genes of the influenza a viruses. II. Characteristics of the amino acid changes in the NS1 proteins of the influenza a viruses

We compared the amino acid sequences of the NS1 proteins of human, equine, and avian influenza viruses. The ratios of the amino acid substitutions per nucleotide substitutions in the NS1 proteins were about 27–45%, suggesting the existence of constraints on the amino acid changes of the NS1 protein in evolution. As a measure of constraints exerted on the regions of a protein, a changeability index is proposed. There was a highly conserved region between amino acid residues 30 and 50. The C-terminal region of amino acid residue 165 was a continuously changeable region. We have either introduced several nucleotide substitutions to the NS cDNA of the A/Udorn/72 virus in vitro or constructed the recombinant NS cDNAs between the A/Udorn/72 and A/chick/Japan/24 viruses, and then expressed them in animal cells. We have found that the amino acid substitutions introduced to the low-conserved region of the NS1 protein affected the stability and nuclear localization of the NS1 protein. One of the chimeric proteins between the A/Udorn/72 and A/chick/Japan/24 viruses did not move to the nucleus of the cell and remained in the cytoplasm.     

Direct interaction of cellular hnRNP-F and NS1 of influenza A virus accelerates viral replication by modulation of viral transcriptional activity and host gene expression

To investigate novel NS1-interacting proteins, we conducted a yeast two-hybrid analysis, followed by co-immunoprecipitation assays. We identified heterogeneous nuclear ribonucleoprotein F (hnRNP-F) as a cellular protein interacting with NS1 during influenza A virus infection. Co-precipitation assays suggest that interaction between hnRNP-F and NS1 is a common and direct event among human or avian influenza viruses. NS1 and hnRNP-F co-localize in the nucleus of host cells, and the RNA-binding domain of NS1 directly interacts with the GY-rich region of hnRNP-F determined by GST pull-down assays with truncated proteins. Importantly, hnRNP-F expression levels in host cells indicate regulatory role on virus replication. hnRNP-F depletion by small interfering RNA (siRNA) shows 10- to 100-fold increases in virus titers corresponding to enhanced viral RNA polymerase activity. Our results delineate novel mechanism of action by which NS1 accelerates influenza virus replication by modulating normal cellular mRNA processes through direct interaction with cellular hnRNP-F protein.     

Structure of an avian influenza A virus NS1 protein effector domain

Influenza A virus NS1 protein is a multifunctional virulence factor. Here, we report a crystal structure for the NS1 effector domain of avian influenza virus A/Duck/Albany/76. Comparison of this structure with that reported for a human strain shows both proteins share a common monomer conformation, albeit with subtle differences. Strikingly, our data reveal a novel helix-helix dimeric interface between monomers of the avian NS1 protein, which is also found in the human NS1 crystal lattice. We re-evaluate the current model of NS1 dimeric assembly, and provide biochemical evidence to show tryptophan-187 (a residue located at the helix-helix interface) is essential for dimerization of this effector domain.     

跨膜区缺失的流感病毒M2蛋白表达纯化及其抗原性检测

目的 表达并纯化缺失跨膜区的流感病毒M2蛋白，并检测其抗原性。方法 利用RT．PCR方法从流感病毒A／PR／8／34（H1N1）的cDNA中扩增全长M2基因，利用两套引物扩增出缺失跨膜区26—43位氨基酸的sM2基因，并克隆到pET30a载体中表达融合蛋白，用镍柱纯化后的融合蛋白免疫小鼠获得抗血清，免疫荧光检测其抗原性。结果 sM2融合蛋白在大肠埃希菌中可高效表达，纯化后可获得高纯度的重组蛋白。免疫小鼠获得的血清进行免疫荧光检测，显示表达的融合蛋白有免疫原性。结论 跨膜区缺失的流感病毒M2融合蛋白与完整M2蛋白有相同的抗原性。