鸡传染性法氏囊病活疫苗（Gt株）对超强毒株HLJ-4和Gx株的免疫保护试验

本研究用传染性法氏囊病活疫苗(Gt株)免疫3周龄SPF雏鸡,免疫两周后,分别用IBDV超强毒株HLJ-4株与Gx株进行攻毒,攻毒剂量为10ELD50/0.1ml,攻毒结果表明:传染性法氏囊活疫苗(Gt株)能抵抗HLJ-4和Gx的攻击,SPF鸡保护率达100%。     

传染性法氏囊病超强毒Gx株VP3基因在病毒致弱过程中的变异研究

利用SPF鸡胚对鸡传染性法氏囊病超强毒vvIBDV Gx株进行培育，通过鸡胚成纤维细胞对病毒进行传代致弱，对其结构蛋白VP3基因核苷酸及推导的氨基酸序列进行分析，从而揭示vvIBDV Gx从超强毒力向弱毒力转化过程中基因的序列变化规律。对不同代次细胞毒序列分析的结果表明，细胞毒在第8代以前，VP3基因序列没有改变，与标准超强毒HK46株氨基酸同源性达99％以上；细胞毒第9代核苷酸和氨基酸序列发生了改变；10代毒VP3基因与标准弱毒P2株氨基酸序列同源性达100％；细胞适应毒传至20代，其VP3基因序列不再改变。从而说明，vvIBDV Gx株在致弱过程中，VP3基因也随之改变。     

1株基因3型鸭甲肝病毒鸡胚化弱毒株的培育

为研发基因3型鸭甲肝病毒(Duckhepatitis virustype3,DHAV-3)的弱毒活疫苗,用SPF鸡胚对DHAV-3Y株进行了连续传代致弱,由此获得第80代鸡胚适应毒。致病性试验结果显示,第80代毒株对1日龄雏鸭已无致病性。免疫攻毒保护试验显示,雏鸭在1日龄时经肌肉注射途径免疫第80代鸡胚适应毒,能有效抵抗7日龄时的强毒感染,保护指数为100%。表明第80代鸡胚适应毒是一株具有良好免疫原性的鸡胚化弱毒疫苗候选株。     

传染性法氏囊病超强毒Gx株VP5基因在病毒致弱过程中的变异研究

利用SPF鸡胚对鸡传染性法氏囊病超强毒(vvIBDV)Gx株进行培育,通过鸡胚成纤维细胞对病毒进行传代致弱,对其非结构蛋白VP5基因核苷酸及推导的氨基酸序列进行分析,从而揭示vvIBDV Gx从超强毒力向弱毒力转化过程中基因的序列变化规律.对不同代次细胞毒序列分析的结果表明,细胞毒在第8代以前,VP5基因序列没有改变,与欧洲标准超强毒氨基酸同源性达98%以上;细胞毒第9代核苷酸和氨基酸序列发生了改变;10代毒VP5基因与欧洲标准弱毒Cu-1氨基酸序列同源性达99%;细胞适应毒传至20代,其VP5基因序列不再改变.从而说明,vvIBDV Gx株VP5基因在致弱过程中存在变化规律.     

鸡传染性法氏囊Gt株弱毒活苗与G株灭活苗免疫方法的探索

目前我国鸡传染性法氏囊病(IBD)超强毒株的弱毒疫苗和灭活疫苗已相继研制成功,但各有特点,其中Gt株活疫苗的特点是产生免疫抗体较早,对母源抗体的干扰相对较差,产生的抗体水平相对较低;而G株灭活苗的特点是产生免疫抗体相对较晚,抗体水平相对较高,保护性较强。为有效地控制IBD,最大限度地发挥疫苗的作用,笔者设计了本次试验,对鸡传染性法氏囊Gt株弱毒活苗与G株灭活苗的免疫方法进行了再探索,应用不同方法免疫鸡群,通过不同时期免疫抗体水平跟踪检测,最终达到对不     

鸡传染性法氏囊病三价与单价活疫苗的效力比较试验

鸡传染性法氏囊病(IBD)是3～12周龄鸡的一种高度接触性病毒传染病，会造成鸡的主要免疫器官——法氏囊损伤，导致机体的免疫抑制，使病鸡对其它疾病的易感性增加，对其它疫苗免疫的应答能力下降，给养鸡业造成严重危害。近年来，鸡法氏囊病病毒血清亚型或变异株和超强毒株的出现，使该病又出现了一些新的流行特点。传统的标准Ⅰ型弱     

鸡传染性法氏囊的治疗

鸡传染性法氏囊病(IBD)又称鸡传染性腔上囊病。传染性法氏囊病毒属双RNA病毒科,包括两个血清型。根据毒株的致病性,IBDV可分为无致病力(血清II型)、弱毒力(疫苗株)、经典强毒、变异株和超强毒株。血清II型株不引起鸡的法氏囊损伤和鸡只死亡。弱毒力株不引起死亡,但根据其毒力的差异对法氏囊造成不同程度的损伤。经典强毒株引起     

B-2鸡传染性法氏囊病弱毒细胞疫苗的研究

将鸡传染性法氏囊病(IBD)弱毒鸡胚疫苗病毒适应于鸡胚成纤维细胞,使之成 IBD 弱毒细胞疫苗,代号为B-2.疫苗毒价稳定在10~7 TCID_(50)ml.可采用滴鼻、点眼或饮水等途径免疫.实验室试验,对雏鸡安全,被免疫鸡的免疫活性不受影响,野外试验,可有效控制 IBD 和减少死亡率,对新城疫免疫不发生干扰.     

鸡传染性法氏囊病超强毒Gx及其致弱株基因组B节段的克隆和序列分析

用蛋白酶K法分离提取了鸡传染性法氏囊病病毒强毒株Gx及其致弱株Gt的病毒核酸dsRNA,应用随机引物将RNA反转录成cDNA,以此为模板用长距离一步法扩增出全长基因B节段,将其克隆入PMD18-T载体,进行了测序,并用DNAStar软件进行序列分析.测序结果表明,克隆的Gx株B节段全长为2 827bp,与超强毒参考株UK661的同源性为88.2%,与强毒参考株Harbin-1株的同源性达96.3%;克隆的Gt株B节段全长为2827bp,与弱毒参考株P2的同源性达99.5%.而Gx株与Gt株B节段的核苷酸的同源性只有89.8%;vvIBDV-Gx、IBDV-Gt株B节段全长的获得将为进一步构建感染性分子克隆奠定必要的基础.     

两个中等毒力IBDV疫苗免疫鸡对超强毒攻毒的保护试验

应用 SPF鸡分别比较研究了两个国内厂家生产的中等毒力 IBDV疫苗接种后对法氏囊和胸腺的影响和对超强毒 GX-8/99攻毒后的免疫保护力。结果表明 ,用于试验的两个中等毒力疫苗虽然在 SPF鸡可引起法氏囊和胸腺不同程度的萎缩 ,但确实能够 1 0 0 %保护已经免疫的SPF鸡免于超强毒 IBDV人工感染造成的死亡 ,而且 ,还能减缓和预防超强毒感染合并诱发的法氏囊的炎症、出血和变性。从而说明 ,在不受母源抗体干扰条件下 ,中等毒力的 IBDV疫苗能诱发对超强毒 IBDV中国株 GX-8/99攻毒的有效免疫保护力。     

鸡传染性法氏囊病毒超强毒株的分离及生物学特性鉴定

用SPF鸡及鸡胚，从吉林某鸡场病死鸡的法氏囊组织到一株超强毒株（J20株）。此病毒不能凝集鸡的红细胞，可以被IBDV标准阳性血清检出IBDV抗原。通过对J2001分离毒株进行回归实验，测定病毒效价EID50达10^6/0.2ml，发病率为100％，死亡达70％；病毒理化特性试验，电镜观察等证实J20株为鸡传染性法氏囊病超强毒株。     

Changes in VP2 gene during the attenuation of very virulent infectious bursal disease virus strain Gx isolated in China

Very virulent (vv) infectious bursal disease virus (IBDV) Gx strain with high pathogenicity was attenuated through replication in specific-pathogen-free (SPF) chicken embryos and in chicken embryo fibroblast (CEF) cell cultures. The changes in VP2 nucleotide and the deduced amino acid sequences were obtained during attenuation of vvIBDV in CEF culture. Sequence analysis of selected passages from numbers 0 to 20 in CEFs (designated here Gx to CEF-20) showed that no changes were detectable in the VP2 gene before CEF-7. There were a few changes in the nucleotide sequence of the VP2 gene but no amino acid substitutions at CEF-8. The virus of CEF-9 was an intermediate with some amino acid changes that possibly were related to virulence. CEF-10 virus had become similar to CU-1 strain. The VP2 gene sequence remained the same from CEF-10 to CEF-20. The results of pathogenicity tests showed that the mortalities of Gx, CEF-5, CEF-8, and CEF-9 in 4-wk-old SPF chickens were 64%, 60%, 60%, and 32%, respectively; whereas CEF-10, CEF-15, and CEF-20 were nonpathogenic. Virus neutralization tests with Gx strain showed that the antigenicities are similar from Gx to CEF-20.     

Pathogenicity of embryo-adapted serotype 2 OH strain of infectious bursal disease virus in chickens and turkeys

The pathogenicity of serotype 2 OH strain of infectious bursal disease virus (IBDV) to specific-pathogen-free (SPF) chicken embryos and 2-wk-old SPF chickens and turkey poults was investigated. The virus was pathogenic for chicken embryos after five passages as evidenced by pathologic changes in inoculated embryos. The embryo-adapted virus was not pathogenic for 2-wk-old SPF chickens and turkey poults as indicated by lack of clinical signs, gross or microscopic lesions in the bursa of Fabricius of inoculated birds. Bursa-to-body-weight ratios of the inoculated chickens and turkey poults were not significantly different from those of uninoculated controls. Virus-neutralizing antibodies to serotype 2 IBDV were detected in inoculated chickens and turkeys. Results of this study indicated that the embryo-adapted serotype 2 OH IBDV isolate that is pathogenic for chicken embryos is infectious but not pathogenic in chickens and turkeys.     

Protection against infectious bursal disease virulent challenge conferred by a recombinant avian adeno-associated virus vaccine

The development and use of recombinant vaccine vectors for the expression of poultry pathogens proteins is an active research field. The adeno-associated virus (AAV) is a replication-defective virus member of the family Parvoviridae that has been successfully used for gene delivery in humans and other species. In this experiment, an avian adeno-associated virus (AAAV) expressing the infectious bursal disease virus (IBDV) VP2 protein (rAAAV-VP2) was evaluated for protection against IBDV-virulent challenge. Specific pathogen free (SPF) birds were inoculated with rAAAV-VP2 or with a commercial intermediate IBDV vaccine and then challenged with the Edgar strain. IBDV-specific antibody levels were observed in all vaccinated groups; titers were higher for the commercial vaccine group. The live, commercial vaccine induced adequate protection against morbidity and mortality; nevertheless, initial lymphoid depletion and follicular atrophy related to active viral replication was observed as early as day 14 and persisted up to day 28, when birds were challenged. No bursal tissue damage due to rAAAV-VP2 vaccination was observed. Eight-out-of-ten rAAAV-VP2-vaccinated birds survived the challenge and showed no clinical signs. The bursa:body weight ratio and bursa lesion scores in the rAAAV-VP2 group indicated protection against challenge. Therefore, transgenic expression of the VP2 protein after rAAAV-VP2 vaccination induced protective immunity against IBDV challenge in 80% of the birds, without compromising the bursa of Fabricius. The use of rAAAV virions for gene delivery represents a novel approach to poultry vaccination.     

不同方法对鸡胚和法氏囊中囊病病毒抗原含量的检测比较

用单抗介导的抗原捕获－酶联免疫吸附试验（AC－ELISA），琼脂扩散试验（ACP）快速诊断试纸条（ISK）对感染同株强毒或弱毒囊病病毒（IBDV）的鸡胚和鸡法氏囊中的病毒抗原效价进行了检测比较，结果表明，上述3种方法测得法氏囊中温毒IBDV抗原效价分别为10^6.0(AC-ELISA),2^-3.0(AGP)t 10^-3.0，测得鸡胚中强毒IBDV抗原效价依次为10^-1.0,0和0。强毒株接种鸡胚后，只有第1代鸡胚组织可被AC－ELISA测到低效价的IBDV抗原，而第2代以后则未能测到病毒抗原，弱毒疫苗株IBDV感染鸡后，法氏囊中可测到低效价抗原，但感染鸡胚后则无可测性病毒抗原。