含卫星RNA的黄瓜花叶病毒弱株系的分离鉴定及在病毒病防治上的应用

从豌豆上分离获得黄瓜花叶病毒分离物ＣＭＶＰ１,摩擦接种９科２９种植物,ＣＭＶＰｌ在大多数植物上症状很轻或无任何症状,提纯的病毒颗粒为球形,直径约２８ｎｍ,病毒衣壳蛋白亚基分子量约２７．５ｋＤ,所含核酸有五个组份,即ＣＭＶＰ１含有卫星ＲＮＡ。ＣＭＶＰ１接种三生烟后８－１２天内呈轻花叶,此时组织中病毒含量最高,随后症状消失,去除卫星ＲＮＡ能加重ＣＭＶＰ１在番茄上的症状,因而是卫星ＲＮＡ减轻了ＣＭＶＰｌ的病状。当ＣＭＶＰ１保护接种番茄后攻强毒,番茄发病率低,病情轻,保护率达９０％以上,并有一定的刺激生长作用,还能提早开花４天,植株结果数增多,成熟果实的颜色、形态、品质和重量均正常。ＣＭＶＰ１对烟草亦具有很好的保护效果。保护接种的植株能明显减少强毒株侵染,可减少９０％以上。     

猪伪狂犬病毒蛋白激酶基因的序列测定与分析

对伪狂犬病毒湖北株（ＰＲＶ ＨＢ株）蛋白激酶（ＰＫ）基因进行了克隆和序列测定。分析比较了该序列与ＰＲＶＮＩＡ－３株、Ｋａ株以及ＨＳＶ－１、ＶＺＶ ＰＫ基因的同源性。结果显示,在测定全长１３１２ｂｐ的ＤＮＡ序列中,包括着一个１００２核苷酸的开放读框,可编码３３４个氨基酸组成的多肽。ＰＲＶ－ＨＢ株ＰＫ与ＰＲＶ－ＮＩＡ３、ＰＲＶ－Ｋａ、ＨＳＶ－１、ＶＺＶ ＰＫ基因比较,核苷酸的同源性分别为９８．７％、９     

汉滩病毒A9株强毒和弱毒克隆M基因片段G1糖蛋白编码区核苷酸序列的分析比较

采用逆转录－ＰＣＲ方法,用３对引物分３个片段扩增强毒克隆（Ａ９ｖ）及弱毒克隆（Ａ３％）的Ｍ基因片段ｃＤＮＡ,并克隆入ｐＧＥＭ－Ｔ载体中。采用Ｓａｎｇｅｒ双脱氧法测定了Ａ３９ｓ、Ａ９ｖ病毒Ｇ１糖蛋白编码区的全序列,发现二者均由１９７８个核苷酸组成,比７６／１１８株少６个核苷酸,并发现Ａ３９ｓ在Ｇ１编码区有３３个碱基及８个氨基酸与Ａ９ｖ不同。进一步与７６／１１８、ＨＶ１１４的相关序列比较,发现Ｇ１编码区的第６０６、６１４位氨基酸的变异同Ａ３９ｓ病毒的减毒有一定相关。从Ａ３９ｓ、Ａ９ｖ、７６／１１８及ＨＶ１１４４株病毒Ｇ１糖蛋白编码区推导的氨基酸序列亲疏水性资料显示,在位于Ｇ１糖蛋白Ｃ末端的最大亲水区域的６００～６２０位氨基酸区域,弱毒株Ａ３９ｓ同强毒株Ａ９ｖ、７６／１１８、ＨＶ１１４的亲水性有明显不同,而这一差异又主要由第６１４位氨基酸的变异所引起。因此推测,Ｇ１糖蛋白Ｃ端亲水区域同汉滩病毒毒力相关,而第６１４位的精氨酸被谷氨酰胺取代,同Ａ３９ｓ病毒毒力的减弱可能有关。     

表达强毒pp38决定簇的马立克病病毒疫苗毒CVI988点突变株的构建和特性

用鸡马立克病病毒（ＭＤＶ）强毒ＧＡ株的３８ｋＤ磷蛋白（ｐｐ３８）基因克隆ＤＮＡ转染Ｉ型弱毒疫苗ＣＡＩ９８８／Ｒｉｓｐｅｎｓ株ＭＤＶ感染的鸡胚成纤维细胞,再用能识别Ｉ型强毒ｐｐ３８的单克隆抗体Ｈ１９做免疫荧光试验,筛选到能在ｐｐ３８基因上表达强毒株特异性抗原决定簇的定向点突变弱毒株ＣＶＩ／ｒｐｐ３８。用＾３５Ｓ－蛋氨酸标记的细胞裂解物做免疫沉淀反应表明,单抗Ｈ１９不能识别天然ＣＶＩ９８８株ＭＤＶ中的     

表达HSV－2 gD基因的重组痘苗病毒保护小鼠对抗致死量HSV病霉攻击

利用ＰＣＲ方法对单纯疱疹病毒Ⅱ型糖蛋白Ｄ（ＨＳＶ－２ｇＤ）基因进行了修饰,在其５＇端删去约５００ｂｐ的非编码区,仅保留ＡＴＧ上游７个ｂｐ。将修饰后的ＨＳＶ－２ｇＤ基因插入到带有痘苗病毒天坛株ＴＫ基因区段的痘苗表达质粒ｐＪＳＡ１１７５,置于痘苗病毒Ｐ７．５ｋ早／晚期启动子控制下。将此重组质粒用脂质体Ｌｉｐｏｆｅｃｔｉｎ方法转染已受野型ＴＫ￣＋痘苗病毒天坛株感染的ＴＫ￣－１４３细胞,通过同源重组机制和标志基因ＬａｃＺ产物的蓝斑显色作用,以及ＢｕｄＲ试剂对ＴＫ表型的选择压力,筛选出整合有ＨＳＶ－２ｇＤ基因的重组痘苗病毒。Ｓｏｕｔｈｅｍ杂交表明,ＨＳＶ－２ｇＤ基因已正确地插入痘苗病毒ＴＫ基因区内;间接免疫荧光检测显示,ＨＳＶ－２ｇＤ蛋白已得到有效表达,且主要分布于细胞膜。重组病毒免疫家兔可产生明显的抗ＨＳＶ－２ｇＤ中和抗体。用重组病毒免疫小鼠,３周后可使９４％（１７／１８）的小鼠对抗ＨＳＶ－２的致死量攻击,表明重组病毒具有明显的免疫保护作用。     

我国河南与北京腹泻患儿中的星状病毒感染

人星状病毒（ＨＡｓｔＶ）是ＲＮＡ病毒的新家族,从我国河南和北京两地区的急性腹泻患儿便样中鉴定了７株星状病毒,经电镜观察病毒颗粒直径约为２８ｎｍ,表面呈五角或六角星状形态,用ＲＴ－ＰＣＲ检定为阳性,比较ＰＣＲ扩增产物的核苷酸序列构建的序列同源性树表明,１９９０年在河南流行的星状病毒主要为ＨＡｓｔＶ－１,另有一株ＨＡｓｔＶ－５,１９９６年北京流行株为ＨＡｓｔＶ－５。对ＨＡｓｔＶ患儿的临床症状进行了讨论     

汉滩病毒A9株强毒和弱毒克隆M基因片段G1糖蛋白编码区核苷酸序列…

采用逆转录－ＰＣＲ方法,用３对引物分３个片段扩增强毒克隆（Ａ９ｖ）及弱毒克隆（Ａ３９ｓ）的Ｍ基因片段ｃＤＮＡ并克隆入ｐＧＥＭ－Ｔ载体中,采用Ｓａｎｇｅｒ双脱氧法测定了Ａ３９ｓ,Ａ９ｖ病毒Ｇ１糖蛋白编码区的全序列,发现二者均由１９７８个核苷酸组成,比７６／１１８株少６个核苷酸,并发现Ａ３９ｓ在Ｇ１编码区有３３个碱基及８个氨基酸与Ａ９ｖ不同,进一步与７６／１１８,ＨＶ１１４的相关序列比较,发现Ｇ１编码     

不同型犬腺病毒纤突蛋白基因序列的比较分析

根据已发表的ＣＡＶ纤突基因序列,用ＰＣＲ方法,对４个ＣＡＶ－２毒　株和４个ＣＡＶ－１毒株的纤突基因进行了扩增和测序,测定的核苷酸序列经推导得到分别编　码５４３和５４２个氨基酸的ＣＡＶ纤突蛋白全序列。测定的ＣＡＶ－２比较表明：我国流行的ＣＡＶ－２　ＳＹ　强毒株与国外标准强毒株Ｔｏｒｏｎｔｏ　Ａ２６／６１株相同,其驯化致弱的毒株与驯化前相比在１１３４位　发生碱基颠换。测定的ＣＡＶ－１比较表明：我国流行的ＣＡＶ－１株与标准强毒ＲＩ２６１株差异相对　较大,而国内ＣＡＶ－１毒株互相之间相对差别较小。ＣＡＶ－２与ＣＡＶ－１纤突基因的同源性为８０．４８％。     

传染性法氏囊病病毒中国强毒株A节段cDNA基因的克隆和序列分析

以来自哈尔滨传染性法氏囊病病毒（ＩＢＤＶ） 强毒株（Ｈａｒｂｉｎ 毒株,Ｈ） 的基因组ＲＮＡ为模板,用反转录聚合酶链反应（ＲＴ－ ＰＣＲ） 的方法得到了其Ａ 节段的全长ｃＤＮＡ 片段,分５＇端（１ ６５９ｂｐ） 和３＇端（１ ４４４ｂｐ） 上下两段分别克隆到ｐＧＥＭＢ○Ｒ － Ｔ 载体上,测定了其核苷酸顺序,在长为３ １０１ ｂｐ 中含有两个阅读框ＯＲＦＡ１ 和ＯＲＦＡ２ ,分别编码１ ０１２ 个氨基酸的前体蛋白（ＶＰ２ － ４ －３） 和１４５ 个氨基酸的ＶＰ５,ＯＲＦＡ１ 和ＯＲＦＡ２ 有部分的重叠。将核苷酸序列及推测出的氨基酸序列与已报道的ＩＢＤＶ 血清Ⅰ型和Ⅱ型毒株的相应序列进行了比较,结果表明：Ｈ 毒株与其它血清Ⅰ型毒株之间,在核苷酸水平上存在２５ｂｐ － ２６７ｂｐ 的差异;在氨基酸水平上存在１７ ～４０ 个氨基酸的差异。在ＶＰ２ － ４ － ３ 内比较显示,Ｈ 毒株与Ｐ２ 、Ｃｕ－ １ 之间氨基酸的差异最小为１ ．７％ ,Ｈ 毒株与ＵＫ６６１ 之间氨基酸的差异最大为３ ．９ ％ 。变异主要发生在ＶＰ２ 的可变区（２０６ － ３５０ 位氨基酸） ,在Ｈ 毒株所特有的１２ 个氨基酸当中,该区就占５ 个,代表１ ．７６ ％ 的变异。ＶＰ４、ＶＰ３ 和ＶＰ５区各有     

丙型肝炎病毒与宿主细胞蛋白的相互作用及其意义

蛋白－蛋白的结合是病毒与宿主细胞相互作用的分析基础。随着酵母双杂交系统等研究蛋白－蛋白结合新技术的广泛应用,人们对病毒复制的本质及致病机制有了更新的认识,本文综述了丙型肝炎病毒（ＨＣＶ）核心蛋白Ｃ及非结构蛋白５Ａ（ＮＳ５Ａ）与宿主蛋白相互作用的进展,并讨论了它们在ＨＣＶ致病中的作用。     

Mapping of viral genomic regions important in cross-protection between strains of a potyvirus

Cross-protection was tested between potato and tobacco strains of Potato virus A, a member of the genus Potyvirus (PVA), in tobacco plants. Cross-protection was effective only at the initiation of infection. The potato strains provided only weak cross-protection against the tobacco strain, whereas the tobacco strain provided strong cross-protection against potato strains. The tamarillo strain (TamMV) showed cross-protection phenotypes mostly resembling those of the potato strains. Chimera of the PVA strains were utilized to map viral genomic regions important for cross-protection. The coat protein (CP) encoding region and the helper component proteinase (HCpro) affected cross-protection and virus accumulation. An amino acid substitution at the CP N-terminus reduced virus accumulation and the ability to overcome cross-protection, whereas amino acid substitutions introduced to the HCpro increased virus accumulation and the ability to overcome cross-protection. Closer sequence relatedness between the protector and challenger isolate, as determined by the CP-encoding sequence, was correlated with an increased cross-protection ability. Cross-protection was not overcome by inoculation with nonencapsidated viral RNA. Thus, the differences in cross-protection abilities between PVA strains and chimera were not explained with the "re-encapsidation model" described for strains of Tobacco mosaic tobamovirus but may be associated with a virus infection-induced RNA silencing mechanism.     

Vaccination and the population structure of antigenically diverse pathogens that exchange genetic material.

Populations of antigenically diverse pathogens undergoing genetic exchange may be categorized into strains on the basis of a set of principal protective antigens. The extent to which polyvalent vaccines based on these protective antigens can alter the population structure of the pathogen is determined by the degree of cross-protection between strains. In the case where there is no cross-protection, vaccinating against a particular strain will have no effect on the others. As cross-protection increases, the strains containing the antigenic variants included in the vaccine will be diminished in prevalence, and those that do not will increase in prevalence. The rise in prevalence of the latter will become more and more exaggerated as cross-protection increases. However, beyond a critical level of cross-protection, in the absence of vaccination, the steady state of the system is asymmetric in that a certain subset of strains (with non-overlapping repertoires of antigenic variants) will dominate over the others in terms of prevalence. Under these circumstances, a vaccine consisting of the most immunogenic combinations of antigenic variants can cause a dramatic increase in frequency of a subset of rare strains.     

Studies on mutagenesis and cross-protection of cauliflower mosaic virus

Three strains of cauliflower mosaic virus (CaMV) designated NVRS, CM4-184 and PK caused respectively severe, moderate and mild reactions in turnip cv. Just Right plants and severe, mild and symptomless reactions in Brussels sprout cv. Fasolt plants. Chlorotic local lesions formed consistently in the leaves of young turnip plants when inoculated with each of the virus strains. Lesions were suitable for infectivity assay of crude and purified preparations of the virus. Three variants of the NVRS strain were isolated by single-lesion transfer after treatment of the virus with nitrous acid (pH 5.0) and two variants were obtained after treating the virus in acetate buffer at the same pH. One of the variants (designated V3) caused symptomless infection in turnip and Brussels sprout plants. In cross-protection tests, Brussels sprout plants infected symptomlessly with the PK, CM4-184 or the V3 strains, subsequently resisted infection by the severe NVRS strain.     

Dynamics of influenza A drift: the linear three-strain model

We analyze an epidemiological model consisting of a linear chain of three cocirculating influenza A strains that provide hosts exposed to a given strain with partial immune cross-protection against other strains. In the extreme case where infection with the middle strain prevents further infections from the other two strains, we reduce the model to a six-dimensional kernel capable of showing self-sustaining oscillations at relatively high levels of cross-protection. Dimensional reduction has been accomplished by a transformation of variables that preserves the eigenvalue responsible for the transition from damped oscillations to limit cycle solutions.     

The dynamics of cocirculating influenza strains conferring partial cross-immunity

 We develop a model that describes the dynamics of a finite number of strains that confer partial cross-protection among strains. The immunity structure of the host population is captured by an index-set notation where the index specifies the set of strains to which the host has been exposed. This notation allows us to derive threshold conditions for the invasion of a new strain and to show the existence of an endemic multi-strain equilibrium in a special case. The dynamics of systems consisting of more than two strains can exhibit sustained oscillations caused by an overshoot in the immunity to a specific strain if cross-protection is sufficiently strong. Received 15 January 1996; received in revised form 24 June 1996     

Plant viruses and new perspectives in cross-protection

Cross-protection in plants is the phenomenon whereby a plant preinoculated with a mild virus strain becomes resistant to subsequent inoculation by a related severe strain. It has been used on a large scale in cases where no resistant plants are available. Although several hypotheses have been proposed to explain the molecular mechanism underlying cross-protection, no single hypothesis can account for all the data obtained. Recently, a phenomenon akin to cross-protection has been achieved in transformed plants harboring the cDNA of a part of a viral RNA genome. These results obtained by genetic engineering raise new hopes for obtaining plants resistant to virus infection.     

痢疾杆菌不同群、型间交叉保护性试验研究

本文对痢疾杆菌不同群、型间的交叉保护作用进行了观察。试验模型为恒河猴,将其分为４组,第一、三组分别为感染过福氏１ａ和宋内菌并已康复的猴;第四组为用双价菌苗株ＦＳ（福氏２ａ和宋内）免疫的猴体,剂量依次为４×１０１０、６．５×１０１０、６×１０１０,共１６．５×１０１０活菌,第二组为空白对照。所有４组皆用福氏２ａ２５８００×１０８活菌攻击。从发病率来看,不同菌群与菌型间没有明显的交叉保护作用;从发病程度看则一组显著低于对照组,三组与对照组无显著差异,此结果表明痢疾杆菌Ｂ群内存在交叉保护作用,但较同型保护作用弱。     

不同地区分离的霍乱0139菌株交叉保护力试验

本文对得自不同地区的四株０１３９菌株做了毒力、免疫力及交叉免疫力试验;四个地区０１３９菌株免疫小鼠后血清ＩｇＧ、肠液ｓＩｇＡ抗体滴度的比较以及０１群霍乱与０１３９型霍乱的交叉保护力试验。结果表明：０１群霍乱与０１３９型霍乱无交叉免疫力。０１群霍乱菌苗对０１３９型霍乱弧菌基本无保护作用;四株菌株的自身毒力基本相同。３＃株免疫力高于其它株,用３＃株免疫后能抵抗２＃、３＃及５＃株的感染。四株菌株免疫小鼠     

Immunity to seasonal and pandemic influenza A viruses

The introduction of a new influenza strain into human circulation leads to rapid global spread. This review summarizes innate and adaptive immunity to influenza viruses, with an emphasis on T-cell responses that provide cross-protection between distinct subtypes and strains. We discuss antigenic variation within T-cell immunogenic peptides and our understanding of pre-existing immunity towards the pandemic A(H1N1) 2009 strain.     

Effects of acquired immunity and mating strategy on the genetic structure of parasite populations

Although it may have profound effects on how researchers seek to tackle many infectious diseases, little is known of the genetic structure of many pathogen populations. Previous models have suggested that if levels of cross-protection are high, parasite populations may be structured into discrete strains with nonoverlapping antigenic repertoires, even among populations that reproduce sexually. Here, I consider a discrete model of the coevolution of parasites with host-acquired immunity. In this model, if the effective recombination rate is low, strain structure can be maintained for very high levels of cross-protection. However, if the effective recombination rate is higher, this strain structure can no longer be maintained. The effective recombination rate is affected by the actual recombination rate between immunologically selected loci, the proportion of individuals that reproduce sexually, whether recombination occurs inside or outside of the host or vector, and the level of cross-protection. The model predicts that for Plasmodium falciparum, where reproduction occurs inside of a vector, we expect to see strain structure in areas of low transmission but not in areas of high transmission. Strain structure is unlikely to be seen in parasites that reproduce outside of a host or vector, such as Strongyloides ratti.