家蚕浓核症病毒感染油桐尺蠖卵巢细胞系的最适条件

<正> 本实验用提纯的家蚕浓核症病毒DNV体外感染油桐尺蠖卵巢细胞系(BS—484),在细胞水平上研究家蚕浓核症病毒的感染和增殖,并摸索了家蚕浓核症病毒体外感染的最适条件。     

桑尺蠖微粒子病对家蚕的交叉传染性调查

桑尺蠖是桑园常见的害虫,也是传播病原的主要昆虫之一。在广西蚕区调查了桑尺蠖微粒子病对家蚕的交叉传染性。调查结果发现桑尺蠖幼虫微粒子病自然感染率为0.54%;从桑尺蠖体内分离获得4株微孢子虫,编号分别为Pa BM3、Pa BM4、Pa BM5和Pa BM6,光学显微镜下观察Pa BM3、Pa BM5和Pa BM6均为长卵圆形,与家蚕微孢子虫(Nb)存在明显差异;Pa BM4为卵圆形,与Nb相似。通过生物试验测定,发现Pa BM4微孢子虫对蚁蚕的半数感染浓度(IC50)为2.49×10~5个/m L,是Nb的4.64倍,说明其对家蚕也具有较强的食下感染力,而其对家蚕没有胚种传染性;Pa BM3、Pa BM5和Pa BM6三种微孢子虫对家蚕均无感染力。因此,桑尺蠖微粒子病发生情况复杂,潜在对家蚕有交叉传染的风险,蚕种生产需要采取措施防控桑尺蠖的危害。     

生物素—亲和素系统在家蚕病毒研究中的应用:Ⅱ.不同发育时期家蚕DNV蚕座感染与发病率关系的研究

<正> 一、前言家蚕浓核病毒(DNV)是近年来在国内外确定存在的一种新的家蚕病毒,并在生产上危害极大,是养蚕农户歉收的原因之一。因此,如何防治家蚕浓核病是一个很有吸引力的问题。到目前为止,在家蚕 DNV 早期诊断方面,业已建立了酶对流免疫电泳技术、免疫酶标组化法以及前报的 ABC 法等。为早期检测家蚕DNV 提供了有效的手段。但如何把这些手段     

江苏省蚕桑学会1986年年会论文摘要(或题录)(中)

<正> 家蚕CPV、DNV 病毒病是蚕业生产上发生最为普遍的病害,均属慢性病,家蚕在感病后4～7天才出现症状,这时已近晚期。同时潜伏期蚕粪已造成蚕座污染,并将酿成更大发生。应用琼脂双向扩散法与对流免疫电泳法早期诊断家蚕CPV、DNV 病毒病技术,进行家蚕CPV、DNV 病毒病的发生期、发生程度的预测预报,可以使生产者及时地采取相应措施,控制其蔓延,减少损失。本课题共进行了五方面的研究:(1)应用血清化学反应检测家蚕CPV、DNV 病     

溴虫腈对几种桑园害虫和家蚕的室内毒力测定及在田间防治的选择性毒力调查

研究杀虫、杀螨剂溴虫腈在桑树害虫与非靶标昆虫家蚕之间以及桑树害虫之间的差异性毒力,为溴虫腈在桑园安全、合理使用提供依据。采用浸叶法测定24%溴虫腈悬浮剂对野桑蚕、家蚕、桑螟、桑尺蠖的室内毒力选择性比值较高,其LC50值倍数比例为362∶126∶1.6∶1,各种试虫对该药剂的敏感程度从大到小依次是桑尺蠖>桑螟>家蚕>野桑蚕,该药剂对家蚕的毒性很小。分别采用80、160、320 mg/L 3种质量浓度溴虫腈悬浮剂稀释液喷施桑树后间隔1、3、6、9 d采摘桑叶饲养家蚕3龄幼虫至上蔟,除用320、160 mg/L溴虫腈悬浮剂稀释液处理区间隔1 d的桑叶养蚕后,家蚕的各项生理指标与清水对照区差异极显著(P<0.01)外,其它处理区无显著差异(P>0.05),并无迟发性毒性效应。田间防治试验表明,24%溴虫腈悬浮剂对桑树害虫的毒力具有选择性,试验期桑园内的几种害虫对该药剂的敏感程度从大到小依次是桑尺蠖>桑螟>桑毛虫>桑剌蛾,320、160、80 mg/L 3种质量浓度溴虫腈悬浮剂稀释液喷施后7 d对桑尺蠖的平均防效极显著优于对照农药267 mg/L辛硫磷稀释液的防效,而对桑螟的平均防效低于对照农药200 mg/L灭多威稀释液的防效(94.2%)。研究结果显示溴虫腈用于桑园害虫防治具有一定的选择性毒力,对非靶标生物家蚕的毒性较低,该药剂适合用于对桑尺蠖等桑园害虫的防治。     

家蚕对病毒感染抵抗性生理生化机制研究综述

本文介绍了近年在家蚕对病毒(CPV、NPV、IFV、DNV)感染抵抗性生理生化机制方面的研究进展。包括家蚕不同品种、不同发育阶段对病毒感染抵抗性的生理生化机制和不同伺育温度、不同叶质影响家蚕对病毒抵抗性的生理生化机制以及绝食饥饿、低温刺激引起家蚕对病毒抵抗性下降的生理机制。     

广东家蚕浓核病病毒理化性状研究

通过病毒提纯、电镜观察、病毒核酸性状鉴定、病毒蛋白测定、血清学反应、品种感染性及理化因素处理等方法对广东蚕区采集的家蚕浓核病病毒样品进行了分析。结果是:广东家蚕浓核病病毒为直径20nm左右的球状粒子;病毒核酸为单链DNA;顺德株病毒蛋白有6个亚基,南海株病毒蛋白有4个亚基;其它理化性状均与中国株DNV相似。因此认为,广东蚕区发生的浓核病病毒亦属细小病毒科(Parvoviridae)、浓核病毒属(Densovirus)。但顺德株病毒除有直径20nm的粒子外,还观察到有直径较小的球状粒子,病毒蛋白构成与中国株DNV有所不同,有待进一步研究。另外,广东各株浓核病病毒对高温、甲醛、漂白粉、石灰浆等的耐受力较强。     

广西野外昆虫微孢子虫对家蚕交叉感染情况调查

为了了解广西野外昆虫微孢子虫对家蚕交叉感染情况,开展了对野外昆虫感染微孢子虫情况调查,并研究其对家蚕的感染性。调查了桑螟、桑尺蠖、菜粉蝶、斜纹夜蛾和桑毛虫等昆虫的微粒子病自然感染率,测试菜粉蝶、桑尺蠖、斜纹夜蛾微孢子虫对家蚕的病原性及可能存在的自然感染方式,观察野外昆虫微孢子虫孢子的形态差异。结果表明:菜粉蝶、桑尺蠖微孢子虫对家蚕蚁蚕的半数感染浓度(IC50)分别为2.69×105个/mL和7.42×105个/mL,斜纹夜蛾微孢子虫对家蚕也具有食下感染能力,菜粉蝶微孢子虫对家蚕也有轻微的胚种传染能力。带病野外昆虫可以通过粪便或鳞毛传播孢子虫。虽然上述野外昆虫微孢子虫的形态与家蚕微粒子孢子虫具有明显差异,但对家蚕都有较强的交叉感染性。     

家蚕病毒病防治药剂——脓病清的药效评价

脓病清对家蚕NPV、CPV、DNV,只需经4h处理,就能将病毒杀灭;对家蚕血液型脓病、中肠型脓病及浓核病均具有很好的防治作用,能降低死蚕率及死笼率;使用安全,对蚕生理及茧丝质量无不良影响。     

对浓核病的显性抗病性遗传基因的发现

<正> 家蚕对浓核病病毒(DNV)的罹病性非常特殊,对蚕经口接种 DNV 时可区分为感病的和完全耐病的两个系统。业已明确耐病性(严格地说是不罹病性)是遗传的,是受单一的隐性基因所支配。为了了解耐病性     

African swine fever virus: generation of subpopulations with altered immunogenicity and virulence following passage in cell cultures.

Virus subpopulations with variable virulence, immunogenicity, and infectivity to pigs were readily generated by passaging Tengani isolate of African swine fever virus, either biologically cloned or uncloned, in Vero cell cultures. Avirulent virus populations which account for more than 99% of virus in an uncloned preparation of the 27th passage are laboratory artefacts, perhaps do not exist in nature. Furthermore, attenuation of virulence did not occur uniformly in all subpopulations newly generated, and a continuous modulation of virus populations differing in immunogenicity and virulence took place in the same individuals inoculated with the 27th passage virus. The same virus preparation, appearing to be slightly virulent in pigs, contained at least a virulent subpopulation that was manifested only by further inoculating susceptible pigs with viremic blood collected at various times during the clinical course. A cloned virus after 23 passages in cell cultures generated a subpopulation (99.9%) which induced subclinical infection in pigs; however, the infection did not confer a solid immunity to homologous challenge with Tengani isolate in these pigs. The Tengani isolate contained subpopulations of virus with immunogenicities shared by the Lisbon '60 isolate and also contained at least one subpopulation specific for the Tengani only.     

Isoelectric focusing of infectious particles of porcine pseudorabies virus strains in granulated dextran gels.

Isoelectric focusing of infectious particles of four strains of porcine pseudorabies viruses (Indiana, Iowa, Shope and an avirulent live-virus vaccine strains) are described. The pseudorabies virus strains exhibited great mobility in the electric field typical of viruses of the herpes group. Strains were considered electrophoretically homogeneous based on their respective isoelectric points. Maximal virus infectivity was concentrated in reproducible, stationary zones representing 73 to 86% of the total virus infectivity initially applied throughout the gels. All pseudorabies virus strains during processing and after isoelectric focusing retained their ability as whole complete particles to typically infect porcine kidney cell cultures. Virus from gel fractions produces foci in cell cultures that specifically reacted with pseudorabies virus fluorescent antibody conjugate. Prevention of foci could be demonstrated by neutralizing with pseudorabies virus monospecific antiserum. Maximal infectivity titers were demonstrated to be directly related to isoelectric points. Strain differences, in relation to virulence in swine, apparently is not related to isoelectric points.     

杆状病毒的酪氨酸蛋白磷酸酯酶研究

酪氨酸蛋白磷酸酯酶是生命细胞内一类重要的酶 ,与细胞信号转导有关 ,对多种生理过程如生长、分化、代谢、细胞周期调节和细胞骨架等具有重要的调节功能。某些杆状病毒和痘苗病毒的基因组中具有编码酪氨酸蛋白磷酸酯酶的开读框 ,与感染性和致病性有关。病毒编码的酪氨酸蛋白磷酸酯酶具有双重底物特异性 ,即可以同时催化蛋白质酪氨酸和丝氨酸 /苏氨酸残基上的脱磷酸反应     

Infectious cDNA clones of porcine reproductive and respiratory syndrome virus and their potential as vaccine vectors

Full-length infectious cDNA clones have recently become available for both European and North American genotypes of porcine reproductive and respiratory syndrome virus (PRRSV), and it is now possible to alter the PRRSV genome and create genetically defined mutant viruses. Among many possible applications of the PRRSV infectious cDNA clones, development of genetically modified vaccines is of particular interest. Using infectious clones, the PRRSV genome has been manipulated by changing individual amino acids, deleting coding regions, inserting foreign sequences, and generating arterivirus chimeras. The limited available data suggest that all structural proteins of PRRSV are essential for replication of the virus, and that PRRSV infectivity is relatively intolerant of subtle changes within the structural proteins. The major tasks in PRRSV research are to identify virulence factors and pathogenic mechanisms, and to understand the structure-function relationships of individual viral proteins. Utilizing these infectious clones as tools, a new generation of safe and efficacious PRRS vaccines may be constructed.     

Effects of replacing the promoter of the immediate early gene with the promoter of Drosophila heat-shock gene HSP70 on the growth and virulence of pseudorabies virus.

We investigated whether altering control of expression of an essential gene of pseudorabies virus (PRV) influences virus replication and virulence. The PRV immediate early (IE) gene was selected as a target, and its promoter was replaced with the promoter of the heat-shock gene HSP70 of the fruit fly Drosophila. The HSP70 promoter was selected because it is well characterized and can be induced in a broad range of eukaryotic cell lines at temperatures around 42 degrees C. Overlap recombination was used to construct the NIA3-HSP mutant virus. When stocks of the recombinant virus were titrated at 42 degrees C, virus titres were 100 times higher than titres obtained at 37 degrees C. Once replication began, however, the rate of growth of the mutant NIA3-HSP was equal at both temperatures. When wild-type virus was titrated at both temperatures, titres were identical. Mice that were infected with the mutant virus had a longer mean-time-to-death than those infected with the wild-type virus. Thus, the mutant virus was considered to be less virulent. We conclude that replication and virulence of PRV can be modified by altering control of expression of the viral IE gene.     

新城疫病毒弱毒骨架表达强毒F基因的重组病毒生物学特性研究

为了解目前中国新城疫病毒（Newcastle disease virus,NDV）优势基因VIId型的毒力机制,应用反向遗传技术将我国优势流行基因VIId型强毒株I4的F基因替换弱毒LX的F基因,获得表达NDV强毒株I4F基因的重组病毒NDV/LX-If。测定重组病毒的致病指数和组织分布,结果发现,重组病毒NDV/LX-If毒力比骨架病毒有了显著的提高。NDV/LX-If的鸡胚平均致死时间（mean death time,MDT）为56 h,雏鸡脑内接种致病指数（intracebral pathogenicity index,ICPI）为1.49,属于中等毒力,毒力比亲本病毒毒力低,但都能使自然途径感染的鸡100%死亡,同时获得了亲本毒株的组织嗜性。可见,新城疫病毒F基因是毒力和组织嗜性的主要决定因素,但是其它基因对新城疫病毒的毒力也可以产生影响。     

Effect of different methods of maintenance on the pathogenicity and infectivity of Babesia bigemina for the vector Boophilus microplus

Observations were made on the effects of five different methods of laboratory maintenance on the infectivity and virulence of Babesia bigemina for the tick Boophilus microplus. The original isolate was highly infective and virulent, causing premature death of engorged female ticks and reduced egg production. Maintenance of the strain by syringe passage in unsplenectomised calves at six to 10 week intervals reduced both its infectivity and virulence for ticks. When slow passages were preceded by a series of rapid passages in splenectomised calves, the changes to the strain were less pronounced. The other three procedures, rapid syringe passage in splenectomised calves and tick passage in either splenectomised or intact calves, had no statistically significant effect on the characteristics measured.     

Biological properties of viral haemorrhagic septicaemia (VHS) virus: Adsorption and replication

Adsorption and growth of VHS virus of trout were studied in cultures of RTG-2 and FHM cells.Within 1 h virus infectivity in the culture fluid decreased by 90%. No measurable adsorption took place after this time. A higher adsorption rate was achieved by pretreatment of cell cultures with 10 μg zinc sulphate and 10 or 50 μg diethyl-aminoethyl (DEAE) dextran.In both cell lines small amounts of viral antigen could be detected in the perinuclear region by the immunofluorescence technique as early as 3 h after inoculation. Infectivity titres of the culture supernatants started to rise 8–10 h post-infection and reached their maximum after 18 h. In both cell lines, 50% or more of the total infectivity remained cell associated, the yields of free virus obtained from FHM cells being 0.5 log₁₀ TCID₅₀ lower.     

Virulence of South African isolates of Haemophilus paragallinarum. Part 1: NAD-dependent field isolates

The virulence of four South African field isolates of NAD-dependent Haemophilus paragallinarum, representing the four serovars known to occur in that country, was investigated. During this study an alternative challenge model for infectious coryza was used, in which the infectivity as well the virulence of different isolates could be evaluated. The challenge model consisted of the direct challenge, via intrasinus injection of one chicken in a row of interconnected layer cages, containing 10 chickens, which are subsequently infected by natural routes. A scoring system of the clinical signs was established in which a score is given to the ability of the isolate to produce clinical signs in the challenge birds. The mean daily disease score for the flock can be calculated and plotted on a graph to give a graphic representation of the disease profile. A mean disease score, calculated over a 20-day examination period can be calculated. Isolates can then be compared to each other, either graphically or by a comparison of the mean disease scores. It has been demonstrated using this scoring system that the South African serogroup C isolates appear to be more virulent than the South African serogroup A or B isolates. It was further established that the serovar C-3 isolate appeared to be the most virulent.     

Comparison of intestinal (Illinois strain) and cell culture-adapted (M-HP strain) viral populations of transmissible gastroenteritis of swine.

Intestinal and cell culture-adapted viral populations of transmissible gastroenteritis (TGE) of swine were compared by means of sucrose gradient centrifugation, immunnofluorescence, electron microscopy, immune electron microscopy, statistical analysis of the number of plaque-forming units, and ultraviolet sensitivity. Results indicated that the size range and general coronavirus morphologic characteristics were shared by both viral populations. Marked morphologic variations existed among particles from both populations. Unlike the cell culture-adapted virus, the Illinois virus of intestinal origin was infractions representing 2 bands of infectivity which were isolated by the sucrose gradient centrifugation method. The intestinal and cell culture-adapted TGE viruses were similar in antigenicity and in sensitivity to ultraviolet irradiation. There was no indication of a 2nd virus in addition to the coronavirus described as the cause of TGE.