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1.
An outbreak of bluetongue caused by bluetongue virus serotype 2 virus in certain Mediterranean countries during 1999/2000, presented an opportunity to produce a monovalent type 2 vaccine. Since no data have been published previously on the protection conferred by the current live attenuated bluetongue vaccine strains used in the polyvalent vaccine, a challenge experiment was performed to determine the degree of homologous protection induced by the type 2 vaccine strain. The standard vaccine dose of 5 x 10(4) pfu of vaccine conferred 99.7% protection against clinical disease and no viraemia was detected in the vaccinates.  相似文献   

2.
An experimental study was conducted into the immunisation of mice to a strain of Pasteurella multocida with pathogenicity for calf. Here are the findings: (a) The attenuation of Sm-id revertants was measured with reference to the order of extinction and compared to the wild strain. (b) A selected range of Sm-id revertants with differentiated attenuation is presented. (c) Single immunisation, using fully attenuatted Sm-d mutant does prevent lethal infection with partially attenuated Sm-id revertants, although it is ineffective against wild strain infection. (d) Immunity against 100 times the lethal dose of the wild strain can be achieved by two immunisations, that is primary antigen application, using fully attenuated Sm-d mutant, and booster immunisation, using partially attenuated Sm-id revertant.  相似文献   

3.
CpxR是细菌中Cpx双组分系统（two component system,TCS）的反应调控蛋白,通过调控靶基因的转录表达,在细菌细胞膜稳定及毒力方面发挥作用。本研究旨在探究TCS CpxR对禽致病性大肠杆菌（avian pathogenic Escherichia coli,APEC）基本生物学特性、抗血清杀菌能力及致病性的影响。利用Red同源重组系统及互补质粒构建cpxR基因缺失株、互补株,然后比较分析野生株、基因缺失株与互补株的生长曲线、运动性、生物被膜形成能力、药物敏感性、抗血清杀菌能力、动物致病性的差异。结果显示：cpxR基因缺失株与野生株、互补株的生长速度和运动性能无明显差异,且缺失cpxR基因不影响APEC的生物被膜形成能力。然而,缺失CpxR导致APEC对阿米卡星和卡那霉素耐药性降低。血清杀菌试验结果显示,CpxR有助于APEC的抗血清杀菌能力。动物感染试验结果显示,野生株、cpxR基因缺失株和互补株对雏鸭的半数致死量（LD50）分别为7.50×105、7.50×106、1.33×106 CFU,表明CpxR缺失显著降低APEC的毒力。综上表明,TCS CpxR在APEC耐药性、抗血清杀菌能力及毒力方面发挥作用,为阐明APEC的环境适应性、生存能力及致病机制提供参考。  相似文献   

4.
The objective of this study was to determine if a replication defective recombinant adenovirus expressing rabies virus glycoprotein (Adrab.gp) given through a non-invasive vaccination route (by topical application) onto the skin (NIVS) could elicit an immune response and/or protection against rabies. Groups of mice were immunized by NIVS with various doses of Adrab.gp. For comparison, groups of mice were immunized intramuscularly, subcutaneously, or intradermally with Adrab.gp. Mice received two booster immunizations at 1 and 2 months after the first immunization. Virus neutralizing antibody (VNA) titers were measured at day 21 after the first and second immunizations and at day 14 after the third immunization. Fifty percent of the mice immunized by NIVS with 2 x 10(7) and 2 x 10(8)pfu Adrab.gp vaccine developed VNA, whereas none of the control mice or the mice immunized by NIVS with the lowest dose (2 x 10(6)pfu) of Adrab.gp virus developed VNA. However, this low dose induced high titers of VNA in mice immunized by parenteral routes. Two weeks after the last immunization, all the mice were challenged with a lethal dose of rabies virus. More than 70% of the animals immunized by NIVS with > or = 2 x 10(7)pfu Adrab.gp virus survived the challenge, whereas all the mice in the negative control group and the group immunized by NIVS with the lowest dose of Adrab.gp succumbed to rabies. Taken together, the results suggest that NIVS with Adrab.gp can induce VNA production and protection against lethal challenge with rabies virus in mice.  相似文献   

5.
Abstract

A neutralizing monoclonal antibody against infectious hematopoietic necrosis virus (IHNV) was used to select neutralization-resistant mutants from isolates of virus obtained from adult steelhead Oncorhynchus mykiss returning to the Round Butte Hatchery (RB mutants) on the Deschutes River in Oregon, USA, and from rainbow trout (nonanadromous O. mykiss) at a commercial hatchery in the Hagerman Valley of Idaho, USA (193-110 mutants). Two of the mutants, RB-1 and 193-110-4, were significantly (P < 0.001) attenuated compared with parental strains. Vaccination of rainbow trout by waterborne exposure to the mutants conferred solid protection against challenge with wild-type virus. In some trials, fish vaccinated with the RB-1 mutant at 50% tissue culture infectious doses (TCID50) of 1 × 104–1 × 105 TCID50/mL or with the 193-110-4 mutant at 1 × 102–1 × 103 TCID50/mL, held for 14 d, then challenged with the homologous wild-type strain at 1 × 105 TCID50/mL showed relative percent survival of 95–100% (P < 0.005). There was no significant difference (P > 0.05) in protection among fish exposed to the RB-1 vaccine strain at a dose of 1 × 105 TCID50/mL for periods of either 1, 12, or 24 h, held for 14 d, and then challenged with the wild-type RB isolate, although the 1-h exposure seemed to be somewhat less effective. Fish were vaccinated with the RB-1 strain at 1 × 103–1 × 105 TCID50/mL for 24 h then challenged after 1, 7, 14, or 21 d with the wild-type RB isolate. No significant (P > 0.1) protection was observed at 1 d postvaccination, but the relative percent survival increased progressively at each subsequent challenge period, becoming statistically significant by day 7 (P < 0.001) and beyond. These results suggested that resistance to challenge with wild-type virus resulted from development of IHNV-specific immunity and not from viral interference or interferon induction, and they reinforce the potential of an attenuated vaccine to control this important disease.  相似文献   

6.
为探究内化素inlA/inlB/inlC基因对单增李斯特菌(Listeria monocytogenes,Lm)生物学特性的影响,本研究采用融合PCR方法构建Lm681 inlC基因缺失突变体,并构建pKSV7-△inlC穿梭载体,将其转化Lm681-△inlAB感受态细胞,利用温度(42℃)和氯霉素(10μg/mL)抗性双重压力来实现同源重组,筛选同源重组子进行鉴定并研究其部分生物学特性。结果显示,PCR和测序结果证实成功构建了3基因缺失株(Lm681-△inlABC),且缺失株的生长特性与野生株相比无明显差异,溶血特性与野生株保持一致;小鼠感染试验显示,野生株Lm681、Lm681-△inlAB和Lm681-△inlABC对小鼠的致死率分别为80%(8/10)、60%(6/10)和40%(4/10),对小鼠的LD50分别为4.36×10~4、1.35×10~6和2.95×10~7 CFU,且Lm681-△inlABC在肝脏、脾脏及脑组织中的定植能力极显著低于野生株(P<0.01)。研究结果表明,inlA/inlB/inlC基因对Lm致病性发挥具有一定的作用,为深入研究inlX基因介导Lm入侵宿主细胞过程中的作用机制提供了科学依据。  相似文献   

7.
Aeromonas hydrophila is a Gram-negative opportunistic pathogen that causes disease in a wide range of hosts due to its multifactorial virulence. Here we describe the application of transposon insertion mutagenesis approach to obtain an exoenzyme mutant of A. hydrophila strain J-1. Immunization of swordtail fish (Xiphophorus helleri Heckel) with the highly attenuated mutant provided protection (survival of 27 out of 35 fish, compared to survival of only 13 out of 35 control fish) in the fish given the highest immunization dose (10(7) CFU) against intraperitoneal challenge with the wild J-1 strain. Immunization with doses of 10(5) or 10(3) did not provide significant protection.  相似文献   

8.
为了确定深圳出入境检验检疫局和深圳太太基因工程有限公司联合研制的禽流感H5、H7、H9亚型多重实时荧光RT-PCR检测试剂盒对H5和H9亚型禽流感的灵敏度，通过测定已知鸡胚半数致死量（ELD50）的标准毒株的进行了定量。利用9～11日龄SPF鸡胚，对深圳出入境检验检疫局保存的H5和H9亚型标准禽流感毒株进行了鸡胚半数致死量（ELD50）的测定，结果为H5亚型禽流感毒株的半数致死量为10^-7.75/0．2mL，H9亚型禽流感毒株的半数致死量为10^-8.5／0．2mL。用所研制的禽流感H5、H7、H9亚型多重实时荧光RT-PCR检测试剂盒对H5和H9亚型标准禽流感毒株原液进行10倍连续稀释，进行实时荧光RT-PCR灵敏度的测定，结果发现：试剂盒检测H5亚型标准禽流感毒株的灵敏度为标准毒株10^-5倍稀释液，该稀释液含有281ELD50病毒量；检测H9亚型标准禽流感毒株的灵敏度为标准毒株10^-8倍稀释液，该稀释液含有15．8ELD50病毒量。同时检测H5和H9时，试剂盒的灵敏度要比单独检测一个亚型时的灵敏度增加一个数量级。本灵敏度已经能够检测到感染鸡的喉拭子和（或）泄殖腔拭子所采集的病毒量，能够满足检验检疫的实际需要。  相似文献   

9.
本研究旨在确定猪流行性腹泻病毒（PEDV）变异株CH/GX/750A/2015株在Vero细胞上转瓶培养的最佳条件，为大规模生产高效PEDV变异株疫苗提供技术支撑。试验以10 L转瓶培养病毒，对接毒时细胞维持液中胰酶浓度（0、2、4、6、8和10 μg/mL）、细胞密度（40%、60%、80%、100%、200%）、接毒剂量（MOI分别为1、0.1、0.01和0.001）、吸附时间（0、30、60、90、120、240 min）、收毒时间（接毒后12、24、36、48、60、72 h）、维持培养温度（35、36、37和38 ℃）和转瓶转速（6、8、10、12、14、16 r/h）7个条件进行优化。结果显示，PEDV CH/GX/750A/2015株在10 L转瓶中的最佳培养条件为：细胞刚铺满单层时接毒，接毒量为MOI=0.01，维持液（无血清DMEM培养液）中胰酶质量浓度为6 μg/mL，不需吸附，维持培养温度为37 ℃，12 r/h 旋转培养48 h后收获病毒液可获得较高效价的病毒液，效价可稳定达到106.50 TCID50/0.1 mL。本试验为 PEDV 变异株大量培养提供了参考，为变异株疫苗研发奠定了基础。  相似文献   

10.
In this study, we infected NOD/Scid/Jak3null mice engrafted human peripheral blood leukocytes (hu-PBL-NOJ) with measles virus Edmonston B strain (MV-Edm) expressing hepatitis C virus (HCV) envelope proteins (rMV-E1E2) to evaluate the immunogenicity as a vaccine candidate. Although human leukocytes could be isolated from the spleen of mock-infected mice during the 2-weeks experiment, the proportion of engrafted human leukocytes in mice infected with MV (103–105 pfu) or rMV-E1E2 (104 pfu) was decreased. Viral infection of the splenocytes was confirmed by the development of cytopathic effects (CPEs) in co-cultures of splenocytes and B95a cells and verified using RT-PCR. Finally, human antibodies against MV were more frequently observed than E2-specific antibodies in serum from mice infected with a low dose of virus (MV, 100–101 pfu, and rMV-E1E2, 101–102 pfu). These results showed the possibility of hu-PBL-NOJ mice for the evaluation of the immunogenicity of viral proteins.  相似文献   

11.
Chickens were immunized orally with 10(9)cfu of the temperature-sensitive (T(s)) mutant E/1/3 of Salmonella enteritidis at 1, 2, 3 and 7 days of age. The animals were challenged with wild-type strains of Salmonella of different serotypes 7 or 14 days following immunization. Chickens receiving multiple oral doses of the vaccine strain showed no signs of disease. Immunized animals shed the vaccine strain for at least 2 weeks after the last inoculation; on the other hand, colonization by the attenuated mutant of internal organs such as spleen and liver was limited. Early exposure of the immunized animals to the virulent bacteria resulted in a reduced cecal colonization by the pathogen. Visceral invasion by the wild-type strain of S. enteritidis or S. gallinarum was drastically diminished in birds challenged 14 days after immunization. Significant differences in the number of these Salmonella were found in the cecal contents, spleen and liver of immunized birds compared with the control animals. In addition, cecal colonization by the virulent strain was reduced in birds challenged with S. typhimurium. These results demonstrate that immunization of newly hatched chickens with live attenuated T(s) mutant E/1/3 of S. enteritidis is safe and reduces Salmonella shedding.  相似文献   

12.
OmpA is a virulence factor of Riemerella anatipestifer   总被引：1，自引：0，他引：1  
Hu Q  Han X  Zhou X  Ding C  Zhu Y  Yu S 《Veterinary microbiology》2011,150(3-4):278-283
Riemerella anatipestifer infection is probably the most economically important disease of farm ducks worldwide. The pathogen R. anatipestifer causes septicemia anserum exsudativa in ducks, but little is known about the molecular basis of its pathogenesis and the virulence factors involved. In this study, by deleting ompA gene from R. anatipestifer serotype 2 strain Th4, we constructed a mutant strain Th4ΔompA to investigate whether R. anatipestifer OmpA is an important virulence factor. Results showed that although the growth curve, bacterial and colony morphology of Th4ΔompA in tryptic soybean broth (TSB) or on TSB agar were similar to its parent strain Th4, the adhesion and invasion capacities of mutant strain to Vero cells were decreased significantly. Furthermore, the median lethal dose (LD(50)) of both strains was determined to measure the virulence with 10-day-old Cherry Valley ducklings. The results showed that LD(50) of Th4ΔompA mutant was >10(10) colony forming units (CFU), it was attenuated significantly in comparison with that of Th4 which LD(50) was 4.41 × 10(8) CFU. Additional analysis indicated that blood bacterial loading of ducklings infected with the Th4ΔompA mutant were much lower than those of Th4-infected ducklings. The results demonstrate that OmpA is a virulence factor of R. anatipestifer, and that it may act as an adhesin.  相似文献   

13.
To explore the potential of the swinepox virus (SPV) as vector for Streptococcus suis vaccines, a vector system was developed for the construction of a recombinant SPV carrying bacterial genes. Using this system, a recombinant virus expressing truncated muramidase-released protein (MRP) of S. suis type 2 (SS2), designated rSPV-MRP, was produced and identified by PCR, western blotting and immunofluorescence assays. The rSPV-MRP was found to be only slightly attenuated in PK-15 cells, when compared with the wild-type virus. After immunization intramuscularly with rSPV-MRP, SS2 inactive vaccine (positive control), wild-type SPV (negative control) and PBS (blank control) respectively, all CD1 mice were challenged with a lethal dose or a sublethal dose of SS2 highly virulent strain ZY05719. While SS2 inactive vaccine protected all mice, immunization with rSPV-MRP resulted in 60% survival and protected mice against a lethal dose of the highly virulent SS2 strain, compared with the negative control (P < 0.05). Our data indicate that animals immunized with rSPV-MRP had a significantly reduced bacterial burden in all organs examined, compared to negative controls and blank controls (P <0.05). Antibody titers of the rSPV-MRP-vaccinated group were significantly higher (P <0.001), when compared to negative controls and blank controls. Antibody titers were also significantly higher in the vaccinated group at all time points post-vaccination (P <0.001), compared with the positive controls. These initial results demonstrated that the rSPV-MRP provided mice with protection from systemic SS2 infection. If SPV recombinants have the potential as S. suis vaccines for the use in pigs has to be evaluated in further studies.  相似文献   

14.
Immunity against Chlamydia psittaci, an obligate intracellular parasite, was studied in a mouse model of systemic infection. Sera (0.1 ml) and splenic cells (2 X 10(8)) from immunised mice were given intravenously to susceptible mice 16 hours before intravenous challenge with 1 X 10(5) plaque forming units (pfu) of virulent strain AB7. Transfer of immune cells primed with virulent strain AB7 or vaccinal strain 1B, lowered splenic and hepatic colonisation by approximately 5.5 log pfu. Treatment of immune cells with antithymocyte serum plus complement, before transfer, abrogated the protection. Transfer of sera raised against the virulent strain AB7, or the attenuated vaccinal strain 1B, lowered hepatic colonisation by approximately 1.5 log pfu. Sera containing antigenus antibodies, raised against heat-killed chlamydiae from strain AB7 or the non-virulent intestinal strain iB1, were not protective. Cellular immunity is mainly responsible for the observed protection, although humoral immunity may play some role.  相似文献   

15.
从浙江省某麻鸭养殖基地的产蛋下降病鸭生殖器官内分离到1株致产蛋锐减、不致鸭死亡的病毒,经鉴定该病毒属于禽副黏病毒1型,命名为YH99V株。该毒株经动物回归试验能成功诱导鸭发病并回收同样的病毒,通过SPF鸡胚盲传至第9代时致病性突然增强,第11代出现血凝特性,第15代血凝价趋于稳定,鸡胚半数致死量EF15ELD50为10-4.8。MDT、ICPI和IVPI毒力学指标测定以及毒力相关基因序列结构分析表明,分离株的MDT为112h,ICPI为0.225,IVPI为0.41;YH99 V株F0蛋白裂解位点(112～117位)区域氨基酸推导序列为Gly-Arg-Gln-Gly-Arg-Leu,与弱毒株相一致。证明该毒株为新城疫弱毒株。  相似文献   

16.
Deletion of the M063 gene from myxoma virus produces a virus that is unable to replicate in rabbit cells in vitro or in live rabbits but can be propagated in non-rabbit cell lines. A targeted M063 deletion mutant was constructed in the attenuated Uriarra strain of myxoma virus and the ability of this virus to act as a safe, non-transmissible vaccine against myxomatosis was tested in outbred laboratory rabbits. Immunization with the M063 deletion vaccine provided good short-term protection against lethal challenge with virulent myxoma virus. Long-term protection was similar to reported results with heterologous live virus, with some rabbits protected but others succumbing to challenge. Replication-deficient poxvirus vaccines, like the Modified Vaccinia Virus Ankara (MVA) in man and the myxoma virus vaccine described here in rabbits, are very attractive from a safety perspective. Seasonal boosting would be predicted to provide long-term protection. Targeted host-range gene deletions could have potential for rapid development of poxvirus vaccines in general.  相似文献   

17.
猪流行性腹泻病毒SD201604株的分离鉴定及致病性研究   总被引：2，自引：2，他引：0  
本研究旨在获得猪流行性腹泻病毒（PEDV）分离株,并对其致病性进行研究。应用Vero细胞从山东某猪场腹泻病料中进行病毒分离,通过细胞病变、免疫荧光试验、电镜观察和RT-RCR进行鉴定,并对分离株的S基因序列进行分析;应用103.5 TCID50/mL分离株口服接种3日龄仔猪并观察临床症状和病理变化;用不同滴度的分离株分别口服接种3日龄仔猪（3 mL/只）,统计各组仔猪的死亡率,确定最小致死量。结果显示,成功分离到1株PEDV,命名为PEDV SD201604株。该分离毒株能在Vero细胞上增殖,产生细胞病变,传代至F6代时病毒滴度可达103.5 TCID50/mL,免疫荧光试验和RT-RCR检测均为PEDV阳性。电镜观察可见直径大小约为100 nm的病毒粒子,有明显的囊膜和纤突,具有PEDV病毒粒子典型的形态特征,确定分离株为PEDV。S基因序列分析显示,分离株为国内流行的PEDV变异株。动物回归试验结果显示,口服感染该分离株的5头3日龄仔猪全部出现典型的PED临床症状和病理变化,其中3头死亡。最小致死量试验结果表明,口服感染3 mL病毒含量为104.5 TCID50/mL的分离株可使仔猪全部死亡。本试验结果可为PEDV的分离鉴定及生物学研究提供参考与借鉴。  相似文献   

18.
Abstract

Fry of brook trout Salvelinus fontinalis became infected and diseased after immersion exposure to infectious hematopoietic necrosis virus (IHNV), but a long-lasting IHNV carrier state was not induced. Duplicate groups of 100 fish were immersed for 6 h in baths containing a type 1 (Round Butte, RB) or a type 2 (Rangen, RA) IHNV isolate at a high or low dose. Brook trout mortalities induced by immersion in a bath of the RB or RA IHNV isolate at 102 plaque-forming units (pfu) per milliliter were equivalent (1 and 0%), but fish were more susceptible to infection with RA IHNV. Only the single dead fish in the RB group was infected, but 24% of the RAexposed fish were infected 1 week after exposure. At a dose of 106 pfu/mL, exposure to RB IHNV resulted in a higher mortality (35%) and prevalence of infection (89% of live fish sampled at 1 week postexposure), but no infectious virus was detectable by 5 weeks after exposure. In contrast, RA IHNV exposure at a dose of 104 pfu/mL resulted in only 5% mortality, and live fish killed at 1 week postexposure had a 22% prevalence of infection, but infectious virus was not detectable by week 3. Although brook trout have been previously considered to be resistant to IHNV, this study has shown that brook trout become diseased and die after exposure to a high dose of one type I IHNV isolate and can be infected after immersion exposure to even a low dose of type 1 or type 2 IHNV.  相似文献   

19.
为检测牛传染性鼻气管炎病毒(IBRV)抗体在免疫牛体内的产生及其消长规律,评价IBRV LNM株致弱疫苗的保护效力,并确定免疫持续期,本实验对免疫试验组牛每头颈部肌肉接种制备的IBRV LNM株致弱疫苗104.5 TCID50/mL,监测血清抗体效价,进行免疫期的确定。在疫苗免疫后的6个月、9个月和12个月分别抽取3头免疫组和两头对照组牛采用IBRV-LN01/08强毒株进行攻毒试验,每头牛的攻毒剂量为107.0 TCID50/mL。结果显示疫苗免疫后12个月时,中和抗体效价仍维持在1∶11以上。攻毒结果显示3个时间点强毒攻击后,疫苗对免疫牛均具有良好的保护力。研究表明IBRV弱毒疫苗可有效地保护免疫牛抵抗IBRV强毒株的攻毒,其免疫持续期最少为12个月。  相似文献   

20.
The aroA gene from Actinobacillus pleuropneumoniae serotype 1 reference strain 4074 was isolated and sequenced. The gene complemented the aroA mutation in Escherichia coli AB2829. A kanamycin resistance cassette was inserted into the aroA gene and the mutant gene was reintroduced into A. pleuropneumoniae by allelic replacement. Intratracheal infection of susceptible pigs with A. pleuropneumoniae aroA caused no signs of respiratory disease or lung lesions in any of the animals at a dose 10(4) times the dose reliably known to induce acute pleuropneumonia; all animals infected with the unaltered control strain developed acute disease. The aroA mutant was rapidly eliminated from the lungs and tonsil of infected animals. The mutant may represent a safely attenuated strain for use in live bacterial vaccination or the delivery of antigen by the intranasal route. However, the residence time of the mutant in the respiratory tract of the pig may be too short for it to be useful in generating a protective immune response.  相似文献   

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