流行性感冒病毒鸡胚高产株的遗传特性分析

流行性感冒（流感）病毒的基因组由分节段的单股负链RNA组成,其中A、B型流感病毒含8个基因节段［1］。它的第4和第6节段分别编码病毒的血凝素（HA）和神经氨酸酶（NA）,决定病毒的抗原性,其它6个节段与病毒的生长特性有关［2］。在流感疫苗生产中,为了提高产量,利用高产毒株与流行毒株基因重配获得重组病毒,它含有流行毒株的第4、第6节段和高产毒株的其它6个节段,这样既具有流行毒株的抗原性又具有高产特性,可以用来降低疫苗的生产成本。     

Functional Match between Influenza Virus Hemagglutinin and Neuraminidase Is Restored after Gene Reassortment

Influenza virus A (FluA) reassortants with low-functional neuraminidase (NA) of subtype N1 and hemagglutinin (HA) of subtypes H2, H3, H4, and H13 display virion aggregation and accumulate to a lower titer because sialyl residues are not completely removed from virion components. Nonaggregating variants of FluA (H13N1) were shown to result from a mutation that reduces the HA affinity for sialyl substrates. Amino acid substitution K156E, which increases a negative charge at the edge of the receptor-binding pocket of HA large subunit (HA1), was revealed in two independent variants. This substitution was the only difference between HA1 of the original reassortant and one of its variants and, therefore, accounted for restoration of the functional match between HA and NA.     

整合禽流感病毒血凝素糖蛋白的假型鼠白血病病毒

本研究通过一个瞬时转染系统将H5N1亚型鹅源禽流感病毒囊膜表面的血凝素(HA)糖蛋白整合到鼠白血病病毒(MuLV)颗粒表面并进行了感染性测定。将包含HA基因的真核表达质粒pcDNA-HA与MuLV假病毒构建体系的两种质粒pHIT60(包括MuLV的结构蛋白基因,即gag和pol)和pHIT111(为MuLV的基因组,还包括一个报告基因LacZ)瞬时共转染转化了SV40大T抗原的人胚肾细胞293T,48小时后收集假病毒上清进行了一系列鉴定。将假病毒上清超速离心后用抗H5亚型禽流感病毒的多抗通过Western-blot证实HA 蛋白能够在此假病毒颗粒表面表达,表明HA能够整合到此病毒粒子表面。通过感染293T、COS 7和NIH3T3 三种不同的靶细胞,均能检测到LacZ基因的表达,证实所构建的假病毒粒子具有感染性。本研究成功构建了具有感染性的MuLV-HA假病毒,为研究鹅源禽流感病毒侵入细胞的机理及其组织嗜性的变异提供一种新方法。     

IL-12增强流感血凝素DNA疫苗在小鼠中抗流感作用

流感病毒的表面抗原血凝素 (hemagglutinin ,HA)能作为DNA疫苗抗流感病毒攻击 ,在小鼠模型中检测白介素 12 (interleukin 12 ,IL 12 )能否作为HADNA疫苗佐剂增强小鼠抗流感病毒攻击。将IL 12和HA共同免疫小鼠 ,免疫 2次 ,间隔 3周 ,加强免疫后用致死量流感病毒攻击。共同免疫IL 12和HADNA与单独免疫HA相比 ,无论初免还是加强免疫后血清中抗HA的IgG抗体显著提高 ,小鼠体重丢失 (一种临床症状 )明显减少且提高了小鼠的存活率。这些结果表明了IL 12能作为一种佐剂提高流感DNA疫苗的免疫效价。     

Isolation and Classification of Temperature-Sensitive Mutants of Influenza B Virus

We isolated 25 temperature-sensitive mutants of B/Kanagawa/73 strain generated by mutagenesis with 5-fluorouracil and classified them into seven recombination groups by pair-wise crosses. All mutants showed a ratio of plaquing efficiency at the nonpermissive temperature (37.5 C) to the permissive temperature (32 C) of 10^–4 or less. At 37.5 C most of group I, II, and III mutants did not produce appreciable amounts of protein, but all other group mutants were protein synthesis-positive. A group VII mutant produced active hemagglutinin (HA) and neuraminidase (NA) at the nonpermissive temperature, but Group V mutants produced only active NA and were defective in the HA molecule. The other group mutants, including group IV mutants with mutation only in the NA gene (8, 10), lacked both activities at the nonpermissive temperature. One of nine influenza B virus isolates in 1989 had EOP 37.5/32 of 1/3 × 10^–2 and belonged to recombination group VII.     

H9与H5亚型禽流感病毒血凝素基因的快速鉴别

建立一步法RT-PCR检测方法,对禽流感病毒(Avian influenza virus,AIV)的血凝素(Hemagglutinin,HA)分型进行了研究。参照AIV的HA基因序列设计1对引物,对H9和H5亚型AIV进行了扩增,产物大小分别为579bp和177bp。经测试,该引物不与新城疫病毒等鸡的其它传染性病原及鸡肌肉组织的核酸发生交叉反应。敏感性分析发现,从50pg的AIV总RNA中亦能扩增到目的条带。结果表明,此次利用1对引物建立的一步法RT-PCR方法简便适用,可以在一次反应中同时将H9和H5亚型AIV进行快速检测和分型。另外,两个亚型的扩增产物均包含了HA裂解位点在内的基因序列,可通过测序推导氨基酸顺序以预测H5或H9亚型禽流感病毒的潜在毒力。     

人H5N1流感病毒血凝素蛋白DNA疫苗的构建及其免疫原性研究

将我国分离的首株人H5N1亚型禽流感病毒A/Anhui/1/2005作为研究对象,扩增其HA和HA1基因片段并克隆至真核表达载体pStar,构建成真核表达质粒。通过Western blot和间接免疫荧光检测方法确认,构建的重组质粒在真核细胞中成功地表达了目的蛋白HA和HA1。将重组质粒免疫BALB/c小鼠,检测免疫后外周血中HA/HA1特异性抗体的效价,并比较HA和HA1的免疫原性。结果表明,重组质粒免疫后成功地诱导了体液免疫反应,且二者的血清抗体效价无显著性差异。     

禽流感病毒血凝素蛋白的结构、功能与表达

血凝素蛋白（HA）既是一种重要吸附蛋白,介导禽流感病毒吸附和穿入宿主细胞而发挥致病作用,也是一种良好的保护性抗原,对宿主抵抗禽流感起到了决定性保护作用。研究HA蛋白对揭示禽流感病毒的致病机理和免疫防治禽流感均具有重要意义。本文重点概述了HA蛋白的结构、功能和蛋白表达方面的研究进展,并对HA蛋白在禽流感疫苗中的应用进行了探讨。     

麻疹病毒血凝素基因H的点突变与血凝作用的转变

经Ｂ９５ａ细胞系纯化分离的三株麻疹病毒Ｆｕ、ＩＭＡ、ＳＭＤ的血凝试验（ＨＡＤ）为阴性,但将它们分别感染Ｖｅｒｏ细胞并传代培养后其血凝试验由阴性转变为阳性。实验证明这种血凝表型的转变与血凝素基因Ｈ的表达与吸附无关。以ＰＣＲ扩增血凝素基因Ｈ和融合基因Ｆ,并分别进行序列分析。表明三株病毒在两种培养细胞中传代后其融合基因Ｆ的序列未发现差异。但血凝素基因Ｈ的序列却有显著的点突变并伴随血凝表型的转变。其中Ｆｕ     

Localization Analysis of Heterophilic Antigen Epitopes of H1N1 Influenza Virus Hemagglutinin

Previous studies have indicated that two monoclonal antibodies(mAbs; A1-10 and H1-84) of the hemagglutinin(HA)antigen on the H1 N1 influenza virus cross-react with human brain tissue. It has been proposed that there are heterophilic epitopes between the HA protein and human brain tissue(Guo et al. in Immunobiology 220:941–946, 2015). However,characterisation of the two mAbs recognising the heterophilic epitope on HA has not yet been performed. In the present study, the common antigens of influenza virus HA were confirmed using indirect enzyme-linked immunosorbent assays and analysed with DNAMAN software. The epitopes were localized to nine peptides in the influenza virus HA sequence and the distribution of the peptides in the three-dimensional structure of HA was determined using PyMOL software. Key amino acids and variable sequences of the antibodies were identified using abYsis software. The results demonstrated that there were a number of common antigens among the five influenza viruses studied that were recognised by the mAbs. One of the peptides, P2(LVLWGIHHP191–199), bound both of the mAbs and was located in the head region of HA. The key amino acids of this epitope and the variable regions in the heavy and light chain sequences of the mAbs that recognised the epitope are described. A heterophilic epitope on H1 N1 influenza virus HA was also introduced. The existence of this epitope provides a novel perspective for the occurrence of nervous system diseases that could be caused by influenza virus infection, which might aid in influenza prevention and control.     

Synonymous Mutations at the Beginning of the Influenza A Virus Hemagglutinin Gene Impact Experimental Fitness

The fitness effects of synonymous mutations can provide insights into biological and evolutionary mechanisms. We analyzed the experimental fitness effects of all single-nucleotide mutations, including synonymous substitutions, at the beginning of the influenza A virus hemagglutinin (HA) gene. Many synonymous substitutions were deleterious both in bulk competition and for individually isolated clones. Investigating protein and RNA levels of a subset of individually expressed HA variants revealed that multiple biochemical properties contribute to the observed experimental fitness effects. Our results indicate that a structural element in the HA segment viral RNA may influence fitness. Examination of naturally evolved sequences in human hosts indicates a preference for the unfolded state of this structural element compared to that found in swine hosts. Our overall results reveal that synonymous mutations may have greater fitness consequences than indicated by simple models of sequence conservation, and we discuss the implications of this finding for commonly used evolutionary tests and analyses.     

两株H9N2亚型禽流行性感冒病毒HA基因序列分析

禽流感(AI)是由A型流行性感冒(流感)病毒引起的一种严重危害禽类健康的传染性疾病.禽类感染禽流感病毒(AIV)后,症状可表现为非显性感染,亚临诊感染,或轻度呼吸道疾病,产蛋量降低,直至急性全身致死性疾病等多种形式.     

Approach to the Involvement of Influenza B Neuraminidase in the Cleavage of HA by Host Cell Protease Using Low pH-Induced Cell Fusion Reaction

ts7, a temperature-sensitive mutant defective in neuraminidase (NA) of influenza B/Kanagawa/73, lacks NA enzymatic activity at the nonpermissive temperature (37.5 C). When MDCK cells were infected with the mutant at the permissive temperature (32 C) and exposed to pH 5.2 medium, extensive cell fusion occurred. In contrast, at the nonpermissive temperature cells did not show cell fusion at all unless they were pretreated with trypsin, suggesting that at 37.5 C the hemagglutinin (HA) of ts7 is expressed at the cell surface in an uncleaved form. It was also found that the replacement of RNA segment 6 of ts7 with that of wild-type B/Lee resulted in the emergence of low pH-induced fusion activity as well as NA enzymatic activity at the incubation temperature of 37.5 C and that the addition of bacterial NA to the cultures infected with ts7 at 37.5 C early in infection brought about low pH-induced cell fusion. We suggest that the removal of neuraminic acid from the carbohydrate moiety of HA by NA is essential for the cleavage of HA by cellular protease.     

Functional Interactions of the Influenza Virus Glycoproteins

Hemagglutinin (HA) and neuraminidase (NA) are functionally related envelope glycoproteins of the influenza virus (Flu). HA interacts with terminal sialyl residues of oligosaccharides and ensures the binding of the virus particle to the cell surface. NA is a receptor-destroying enzyme that removes sialyl residues from oligosaccharides contained in cell and virus components and thereby prevents aggregation of virus particles. Analysis of reassortants combining low-functional NA of human Flu with HA of avian Flu showed that sialyl residues are not completely removed in some cases. With high HA affinity for sialyl substrates, such virus particles aggregate, aggregates accumulate on the cell surface, and virus yield decreases. Serial passaging of low-yield aggregating reassortants may lead to selection of high-yield variants, which do not aggregate. The loss of aggregation is due to a decrease in HA affinity for high-molecular-weight sialyl substrates. On evidence of sequencing of the HA gene in original reassortants and their nonaggregating variants, for different HA antigenic subtypes (H2, H3, H4, and H13) the affinity is reduced and aggregation lost through a common mechanism: an increase in the negative charge as a result of an amino acid substitution in the vicinity of the receptor-binding pocket of HA. Taken together, these findings suggest a way of postreassortment adaptation, which improves the functional match of HA and NA. The experimental system employed provides a model of natural processes associated with emergence of Flu variants having a pandemic potential.     

AIV血凝素亚型同步检测基因芯片技术研究

对流感病毒14个血凝素亚型的基因芯片检测技术进行了初步研究。通过RT-PCR克隆禽流感病毒血凝素基因片段,获得重组质粒。从重组质粒扩增大约500bp的DNA片段,浓缩后点到氨基化玻璃载体上,制成芯片。待检病毒样品用TRIzolLS提取RNA,反转录过程中用Cy5标记样品cDNAs。将标记样品与芯片杂交,扫描芯片上待检样品与芯片上捕捉探针的结合位点,杂交信号与预期设想一致。结果显示,DNA芯片技术可以提供一种有效的AIV血凝素亚型鉴别诊断方法。     

蛋氨酸脑啡肽（MEK）抗B型流感病毒感染作用的研究

研究MEK抗B型流感病毒感染的作用。采用MDCK细胞和9～10日龄鸡胚,按不同的顺序加入不同剂量MEK和B型流感病毒,共培养72 h后做血凝实验。所有加入B型流感病毒的MDCK细胞均培养出病毒,HA滴度为1：64。在鸡胚尿囊腔中,先注入MEK孵育24 h后,再注入B型流感病毒的鸡胚也培养出病毒,HA滴度为1：6.8,与病毒对照组比较P〈0.01,有统计学意义。实验结果未见MEK直接抗B型流感病毒感染MDCK细胞株的作用,但可见MEK抗B型流感病毒感染鸡胚的作用。     

Intracellular Cleavage of Human Influenza A Virus Hemagglutinin and Its Inhibition

Replication of human influenza A viruses and proteolytic cleavage of the viral glycoprotein HA0 HA1/2 were studied in passaged cultures of epithelial cells of the serous membrane of human large intestine (CACO-2 line), dog kidney cells (MDCK), and monkey kidney cells (CV-1). Cleavage of the viral glycoprotein HA0, synthesis of activated virions, multicycle virus infection, and effective production of viral foci under an agarose overlayer were found in CACO-2 cells. By pulse–chase labeling of viral glycoproteins, testing the sensitivity to endoglycosidase-H of the viral glycoproteins HA0 and HA1/2 synthesized, and inhibiting the HA0 proteolysis with brefeldin A, the HA0 HA1/2 proteolysis was established to occur in the late stages of intracellular transport in the trans-Golgi and plasma membrane areas of the cells. Proteolysis of the viral glycoprotein HA0 in CACO-2 cells was suppressed by aprotinin, a natural inhibitor of serine proteinases. Unlike MDCK and CV-1 cells resistant to apoptosis induced by influenza virus, CACO-2 cells retained their viability for 2-3 days after infection with human influenza A virus.     

我国H3N8马流感病毒血凝素基因分子进化树的分析

根据已发表的马流感病毒血凝素基因序列,设计并合成一对特异性引物,经反转录聚合酶链反应(RTPCR)成功扩增出了我国马流感病毒青海株(AEquineQinghai194)、吉林株(AEquineJilin189)及黑龙江株(AEquineHeilongjiang189)血凝素基因,将片段分别连接到PGEMTeasy载体并转化DH5α,提取阳性菌落的质粒经EcRo1酶切和PCR鉴定其大小均为17kb左右,对其测序并构建HA基因进化树。经过比较分析,青海株与AEquineKentucky286、AEquineMiami163等关系较近,核苷酸同源率为973%～847%,而与我国马流感吉林株和黑龙江株关系较远,同源率仅为552%。经过比较,青海株与我国香港1992年马流感病毒关系密切 。     

禽流感病毒H5N1血凝素基因适应性进化过程中的关键位点突变规律研究

目的:寻找导致禽流感病毒H5N1血凝素(HA)适应性进化的关键突变,建立氨基酸突变评价体系,对突变作用进行评估,印证它们与病毒适应性进化的关联性。方法:计算株频率和枝频率,寻找标记分枝,向根结点回溯寻找HA进化路径上的氨基酸突变。计算各突变位点氨基酸的频率变化、有效变换及高频次突变,基于以上几个因素建立突变评价体系。结果:建立了大规模自动化寻找突变的方法,计算得到HA进化过程中的氨基酸突变435个,通过氨基酸频率图表分析这些突变可以很好地反映病毒适应性进化过程,其中79个突变是有效变换,发生的位点为正选择位点,且多数位点落在HA抗原表位上;29个突变是高频次突变,其中多数也为有效变换,因而与病毒适应性进化密切相关。结论:大规模自动化寻找突变的方法可靠,建立的突变评价体系准确性高,找到的关键突变及位点对实验有很好的指导意义。     

在疫苗免疫选择压力下H9N2亚型禽流行性感冒病毒HA基因的遗传变异

为了解H9N2亚型禽流行性感冒(流感)病毒在同亚型灭活疫苗的选择压力下的遗传变异情况,对某鸡场的感染鸡群进行连续4年的跟踪监测,对使用疫苗前和持续使用疫苗后不同时段分离到的H9N2亚型禽流感病毒的HA基因进行全序列分析.结果表明,在使用第一次分离的病毒株制备的疫苗后8个月分离到的病毒株,其HA基因仅发生一个氨基酸的差异;但在继续使用该疫苗的第二个和第三个年头分离的病毒株,它们的HA基因则一直在发生较大的变化.这一发现对进一步研究禽流感病毒在不断使用疫苗的选择压力下发生变异的规律,指导制定正确的禽流感防制对策具有重要意义.