鸡传染性法氏囊病疫苗B87对SPF鸡289的免疫效果

30日龄SPF鸡经点鼻途径用鸡传染性法氏囊病病毒（1BDV）的中等毒力疫苗B87株免疫后14d，再以200个ELD50超强毒IBDV株GX8/99点鼻人工攻毒，所有鸡都没有发病死亡。而对照鸡有10/10发病和6/10死亡，并有典型的病理变化。这表明，对SPF鸡用中等毒力的IBDV疫苗免疫可诱发有效的免疫保护作用。并能完全抵抗超强毒IBDV的攻击。     

IBDV超强毒GX8/99株细胞适应毒及其鸡体回传毒的致病性、免疫原性比较

传染性法氏囊病病毒(Infectious Bursal Disease Virus,IBDV)的超强毒株GX8/99经在鸡胚成纤维细胞(CEF)上连续传代22代后,细胞适应毒株GXC23对鸡的致病性显著减弱,对4~6周龄SPF鸡的致死率从85%~90%,减为0~5%.将GXC23在96孔细胞培养板上经两次无限稀释法得到3个克隆病毒.在SPF鸡回传20代后,相应的毒株GX-2B20、GX-4B20、GX-5B20,对SPF鸡的致死率仍维持在0~5%.回传23代后,GX-2B23,GX-4B23免疫2周龄SPF鸡,3周后虽然能引起法氏囊一定程度的萎缩及点状出血,法氏囊髓质区淋巴细胞坏死和变性,而且,仍表现出明显的免疫抑制性,都能造成新城疫,禽流感(H9-和H5-)疫苗抗体水平的显著降低.但是二者却都可以诱导机体产生很高的抗体水平,可抵抗超强毒GX8/99的人工感染,保护率可达100%.     

鸡传染性法氏囊病超强毒Gx与疫苗毒Gt在鸡体内的复制研究

本试验利用鸡传染性法氏囊病超强毒Gx及其致弱疫苗毒Gt为对象,研究超强毒与弱毒株在鸡体主要免疫器官内的复制情况,以探讨两类毒株表现不同生物特性的原因。分别利用鸡胚半数致死量和鸡胚成纤维细胞半数感染量对超强毒Gx和疫苗株Gt进行病毒滴度的测定;再利用荧光定量RT-PCR对两类毒株进行病毒量的校准。以相同量的病毒对2周龄SPF鸡进行攻毒。攻毒试验表明超强毒Gx能造成47.5%的死亡,法氏囊、脾脏、胸腺等免疫器官均严重损伤;而疫苗毒Gt无致死,且未能造成任何病理可见的损伤。病毒的体内复制情况表明超强毒相对于疫苗毒复制更为迅速,病毒载量更高。     

1997～2001年间31个不同传染性法氏囊病病毒分离株的致病性研究

对1997～2001年间从不同地区收集到的31个鸡传染性法氏囊病病毒(IBDV)野毒株分别人工感染3～7周龄SPF鸡,以比较和确定它们的致病性.比较试验表明,不同毒株间的毒力差异很大,人工感染鸡的年龄也对病毒的致死率有很大影响,4周龄SPF鸡最易感.致病性最强的GX8/99不仅有较明显的易感年龄范围,而且可稳定地引起高达70%～92%的死亡率,是一株真正的超强毒.而人工接种YN2/99株的SPF鸡的死亡率几乎为零.其余毒株对SPF鸡的致死率则介于6%～77%间,但是所有毒株都能造成法氏囊和胸腺的显著萎缩.本研究还表明,我国近几年流行的IBDV大多数毒株的毒力介于典型的超强毒和标准毒之间.     

IBDV超强毒GX8/99株的细胞适应毒和鸡体传代毒的致病性和VP5基因的比较

传染性法氏囊病病毒(Infectious Bursal Diseas Virus,IBDV)的超强毒株GX8/99经在鸡胚成纤维细胞(CEF)上连续盲传23代后,细胞适应毒株GXC23时鸡的致病性显著减弱,对4～6周龄SPF鸡的致死率从85%～90%减为0～5%.GXC23在96孔细胞培养板上经2次无限稀释法后得到3个克隆病毒.经SPF鸡回传20代后,相应的毒株GX-2820、GX-4820、GX-5820对SPF鸡的致死率仍维持在0～5%.序列比较表明,GX8/99在传代过程中,其细胞适应毒GXC23有8个碱基突变,其中5个碱基突变导致了氨基酸改变.bp#2 T→C突变,导致传代毒ORF中的起始编码子后移了4个氨基酸.而3个克隆化病毒回鸡20代后致病性不变,这几个位点也保持不变,且与3个疫苗株完全一致.进一步分析表明,有4个超强毒株和4个强毒株的VP5基因的5个位点与GX8/99原始毒相同,而另3个超强毒及6个强毒株与细胞适应毒GXC23一致.这些结果表明,超强毒GX8/99在细胞传代过程中VP5基因上5个氨基酸的变异主要与适应细胞培养相关而与致病性无关.     

鸡传染性法氏囊病病毒12个野毒株的毒力比较

对3－7周龄SPF鸡人工感染的致病性比较试验表明，从不同地区收集的12个鸡传染性法氏囊病病毒（IBDV）野毒株的毒力差异甚大，致病性最强的GX8／99株可引起易感年龄的SPF鸡70％－92％的死亡率，属超强毒，而人工接种YN2／99株的SPF鸡死亡率几乎为零。其余毒株对SPF鸡的致死率介于20％－60％，它们的毒力介于IBDV的标准毒与超强毒之间。     

鸡传染性法氏囊病免疫复合物疫苗的安全性和免疫效力试验

用鸡法氏囊病免疫复合疫苗(IBDV-Icx)和常规IBD活疫苗分别免疫1日龄商品鸡和SPF鸡,进行疫苗的安全性及免疫效力比较.免疫后8d检测,IBDV-Icx免疫组鸡的法氏囊未见明显萎缩,而传统弱毒疫苗免疫组鸡的法氏囊萎缩明显;免疫后28d各组用IBDV标准强毒株进行攻击,IBDV-Icx免疫组鸡的攻毒保护率均为10/10,常规IBD活疫苗对照组分别为8/10及9/10.免疫后3个月,IBDV-Icx免疫组血清抗体可达AGP1∶32,攻击强毒仍为10/10保护,而常规IBD活疫苗免疫后2个月抗体AGP为0,攻毒保护率为1/10,免疫后3个月时攻毒10/10发病.     

传染性法氏囊病沉淀抗体水平与免疫保护关系的研究

以传染性法氏囊病(IBD)基因工程重组亚单位油乳剂疫苗及其重组活载体疫苗实验室试制品免疫SPF鸡,以法氏囊眼观病变及法氏囊中IBDV抗原检测结果来评定免疫保护效力。结果血清IBDV沉淀抗体水平达到1/8的鸡能抵抗IBDV强毒的攻击,低于1/4的部分鸡不能抵抗IBDV强毒的攻击。经t检验,在以血清IBDV沉淀抗体水平≥1/8所得百分率、血清IBDV沉淀抗体水平≥1/4所得百分率、法氏囊眼观变化正常鸡只百分率及法氏囊中IBDV抗原检测的阴性率之间差异都不显著。表明以血清IBDV沉淀抗体水平≥1/4所得百分率与法氏囊中IBDV抗原检测的阴性率和法氏囊眼观变化正常鸡只百分率一样,适用于评定攻毒免疫保护效力。     

人参皂苷Rg1-菌体CpG对IBDV VP2基因重组真核表达质粒免疫效果的影响

将构建的含鸡传染性法氏囊病病毒（IBDV）JS超强毒株VP2基因的重组真核表达质粒与人参皂苷Rg1和CpG DNA联合佐剂免疫SPF鸡,检测免疫后的抗体水平,并观察超强毒株攻毒后的免疫保护效果。试验结果显示：Rg1-CpG佐剂与重组真核表达质粒DNA疫苗联合免疫后的抗体水平比单一使用DNA疫苗高,二者间有显著性差异;Rg1-CpG佐剂组的发病率、死亡率均低于非佐剂组,保护率则高于非佐剂组,且有显著性差异;而与法氏囊病中等毒力（NF8株）活疫苗免疫组的抗体水平及保护率相一致。表明Rg1-CpG佐剂显著增强了IBDV DNA疫苗的免疫效果。     

鸡传染性法氏囊病灭活苗与基因工程亚单位疫苗免疫效果比较

应用SPF鸡分别比较研究了鸡传染性法氏囊病组织灭活苗和基因工程亚单位疫苗接种后的免疫效果,并用中等毒力毒株D78株攻毒后产生的免疫保护力。结果表明用于试验的灭活苗能够80％保护已经免疫的SPF鸡免于D78株人工感染造成的死亡,而基因工程亚单位相对效果较差,仅能保护20％。这说明在不受母源抗体干扰的情况下,灭活苗的免疫效果要优于基因工程亚单位疫苗。     

Efficacy of live virus vaccines against infectious laryngotracheitis assessed by polymerase chain reaction-restriction fragment length polymorphism

The efficacy of four different commercial live vaccines (vaccines A, B, C, and D) against the infectious laryngotracheitis virus (ILTV) was assessed in specific-pathogen-free (SPF) chickens. SPF chickens were vaccinated intraocularly at 6 wk old with ILTV live vaccines and were challenged intratracheally with the N91B01 strain of virulent Korean ILTV 2 wk after vaccination. The immunity against ILTV live vaccines was assessed by the incidence of latent infection by the challenge virus in the chickens' tracheas and trigeminal ganglia, the reisolation rate of the challenge virus, and the clinical signs in the chickens challenged with the N91B01 strain of ILTV. The latent infection in chickens was assessed by nested polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Our data showed that the clinical signs and challenge virus isolation were negative in all chickens receiving four difference commercial ILTV live vaccines. The viral DNA of the vaccine strain, but not that of the challenge virus, was detected in chickens vaccinated with vaccine A by nested PCR-RFLP. The viral DNAs of both the vaccine and challenge strains were detected from chickens vaccinated with vaccines B, C, and D. This study showed that only vaccine A can protect chickens from latent infection with the field virulent ILTV. We speculate that the efficacy of infectious laryngotracheitis live vaccines to protect chickens from latent infection with virulent ILTVs can be assessed by nested PCR-RFLP analysis.     

An evaluation of inactivated infectious coryza vaccines containing a double-emulsion adjuvant system.

The efficacy of experimental inactivated infectious coryza vaccines produced by a commercial vaccine manufacturer was evaluated. The vaccines, containing as the adjuvant phase either a double-emulsion mineral oil system or aluminum-hydroxide gel, were administered to 6-week-old chickens as a single dose. Some vaccines were a monovalent product containing a Page serovar C Haemophilus paragallinarum strain, and others were a bivalent product containing both Page serovar A and serovar C strains. After 3 weeks, all chickens were challenged by infraorbital sinus inoculation of virulent H. paragallinarum, either Page serovar C (strain HP31) or Page serovar A (strain HP14). The monovalent serovar C double-emulsion-based vaccines gave significant protection against a serovar C challenge, with the level of protection varying from 60% to 100%. The monovalent serovar C aluminum-hydroxide-gel vaccine also gave significant protection (94%) against a serovar C challenge. The bivalent double-emulsion vaccine gave significant protection against challenge from both serovars (100% for serovar C and 83% for serovar A). Although no major adverse reactions were detected, some chickens receiving both the double-emulsion vaccines and the aluminum-hydroxide vaccine developed relatively minor granulomatous reactions at the site of injection.     

Immune responses of breeding chickens to trivalent oil emulsion vaccines: responses to Newcastle disease and infectious bursal disease

Bivalent Newcastle disease (ND)/infectious bursal disease (IBD) and trivalent ND/IBD/infectious bronchitis (IB) inactivated oil emulsion vaccines were prepared in the laboratory and evaluated under field conditions. Broiler breeder parent chickens previously vaccinated with live vaccines were inoculated with commercial monovalent ND and experimental bivalent or trivalent oil emulsion vaccines. The commercial vaccine induced a higher initial ND haemagglutination inhibition (HI) response than the experimental vaccines but, by 34 weeks after vaccination, the mean ND HI levels were not significantly different in any of the three flocks. All three vaccines provided sufficient ND immunity to protect against the clinical disease and egg production losses. The IBD responses of both flocks vaccinated with oil emulsion vaccine were similar to each other and only slightly lower than those flocks vaccinated with monovalent IBD oil emulsion vaccine in earlier experiments. Six weeks after vaccination, sufficient immunity was transferred to protect all the progeny against IBD challenge up to 33 days of age and some of them up to 45 days of age. Thirty-four weeks after vaccination of the parents with oil emulsion vaccine, the progeny were totally immune up to 27 days of age and some of them were immune until 37 days. Application of oil emulsion vaccines in bivalent or trivalent form did not impair the responses of the chickens to the monovalent components.     

Influence of a reovirus-antibody complex vaccine on efficacy of Marek's disease vaccine administered in ovo

Two experiments determined the influence of an experimental reovirus-antibody complex vaccine on Mareks disease virus (MDV) vaccine when used in ovo. Designs were the same except that specific-pathogen-free (SPF) broiler eggs were used in Experiment 1 and commercial broiler eggs with maternal antibodies against reovirus were used in Experiment 2. At 18 days of incubation, embryos were separated into four groups and inoculated with either diluent, MDV vaccine, reovirus-antibody complex vaccine, or a combination of reovirus-antibody complex and MDV vaccine. At 5 days of age, half the chickens in each group were challenged with MDV. At 7 wk old, all were euthanatized, weighed, and examined. At 7 days of age, remaining chickens in each group were challenged with reovirus. At 21 days old, chickens were euthanatized and weighed. No vaccine adversely affected hatchability or posthatch mortality in SPF or commercial chickens. There were no significant differences in protection against reovirus challenge when vaccines were used separately or in combination, and lesion scores were nearly identical in all vaccinated groups in both experiments. However, percentage of protection against reovirus was lower in Experiment 2, indicating an adverse effect of maternal immunity on efficacy of the reovirus vaccine. There were no significant differences in protection against MDV when the vaccines were used separately or combined. Severity of MDV lesions was nearly identical in all vaccinated groups in both experiments. However, the combination of vaccines gave numerically lower protection against MDV than MDV vaccine alone. Use of a larger number of birds, as in field conditions, may result in statistically lower protection for the vaccine combination. Large field trials are needed to determine the potential of the reovirus-antibody complex vaccine.     

鸡马立克氏病三价疫苗的安全性及免疫效力研究

将MD三价疫苗以25000PFU／只的剂量颈部皮下接种1日龄SPF雏鸡，结果表明，疫苗的接种不影响鸡体重的增加；不引起鸡法氏囊、脾脏等组织器官发生MD组织病理学变化，对鸡安全无毒性。用SPF鸡评价MD三价疫苗的免疫效力，三批疫苗对RB1B超强毒株攻击的平均保护效力为95．99％，而且无论是用RB1B超强毒株还是用BJMDV-1血毒攻击，MD三价疫苗的保护效力明显高于HVT＋SB1二价疫苗及HVT冻干苗，好于CV1988疫苗；接种MD三价疫苗的4个品系的商品鸡群，抗RB1B超强毒株攻毒的平均保护效力为94．60％；在模拟MD强毒自然传染的试验中，MD三价疫苗的保护效力达到95．65％。上述效力试验的结果说明：MD三价疫苗的免疫接种可使鸡形成抗MD强毒攻击的坚强免疫力。     

Safety and efficacy of an experimental reovirus vaccine for in ovo administration

A commercial reovirus vaccine alone or experimental reovirus vaccine plus antibody complex were inoculated into 18-day-old specific pathogen free (SPF) broiler embryos at 0.1 of the recommended chick dose. The following groups were used: group 1A was not vaccinated or challenged; group 1B was not vaccinated, but was challenged with virulent reovirus; group 2 received the vaccine complexed with 1/4 dilution of antiserum; group 3 received the vaccine with 1/8 dilution of antiserum; group 4 received the vaccine with 1/16 dilution of antiserum, and group 5 received vaccine alone. At 1, 3, 6, 9, and 12 days of age, serum was collected and antibody against avian reovirus was analyzed by enzyme-linked immunosorbent assay (ELISA). At the same times, spleens were collected and vaccine virus detected by inoculating chicken embryo fibroblasts (CEFs) and examining for cytopathic effect. At 15 days of age, chickens in groups 2-5 were challenged with reovirus. At 22 days of age, birds were euthanatized and weighed. Efficacy of the vaccines was based on safety, percent protection, and antibody response. In ovo vaccination with the commercial or experimental vaccines did not adversely affect hatchability of SPF chickens. The vaccine complexed with antibody resulted in significantly less posthatch mortality (3.7%) when compared to mortality of chickens that received vaccine alone (17%). Both vaccine virus recovery and antibody response were delayed at least 3 days in birds receiving the experimental vaccines. In evo administration of reovirus antibody complex vaccines provided at least 70% protection. The experimental reovirus-antibody complex vaccines were safe and efficacious when given in ovo to SPF broiler embryos.     

Infectious bursal disease virus variant from commercial Leghorn pullets

An infectious bursal disease virus (IBDV) was isolated from 39-to-43-day-old commercial leghorn pullets suspected of having infectious bursal disease (IBD). These chickens had been vaccinated with a commercial live IBDV vaccine at 28 and 35 days of age. An isolate designated IN was recovered using specific-pathogen-free (SPF) chickens and the BGM-70 established cell line. Experimental studies using SPF chickens vaccinated with either inactivated vaccines made from the vaccine strain used in the problem flock or a standard-type vaccine indicated no protection against the IN isolate. However, two variants and another standard-type vaccine induced protection against the IN isolate. Cross-neutralization tests indicated that the IN isolate differed antigenically from commercial vaccine strains and was related to the variant IBDV strains recently isolated from broilers. To our knowledge, this is the first report of a variant IBDV recovered from commercial layer chickens in the United States.     

Evaluation of the effectiveness of two infectious bronchitis virus vaccine programs for preventing disease caused by a California IBV field isolate

Infectious bronchitis virus CA99 serotype was isolated from several broiler flocks in Northern California. The virus caused late-onset respiratory disease and increased airsacculitis condemnation in affected flocks despite the use of an established infectious bronchitis virus vaccination program. An experimental study compared Holland/Arkansas and Massachusetts/Arkansas vaccination protocols to determine the efficacy of commercial infectious bronchitis virus vaccines in reducing respiratory disease and airsacculitis lesions found at processing that were associated with a CA99 field isolate. All vaccination groups were given Massachusetts/Connecticut strains of infectious bronchitis virus vaccines at age 1 day followed by vaccination with either Holland/ Arkansas or Massachusetts/Arkansas vaccine strains at 18 days of age. Birds were challenged at age 31 days with a CA99 field isolate. Gross pathology, histopathology, and virus isolation were evaluated. Chickens vaccinated with Holland/Arkansas had marginally better protection against CA99 challenge than chickens vaccinated with Massachusetts/Arkansas, although differences were not statistically significant.     

Efficacy of avridine as an adjuvant for Newcastle disease virus antigen in chickens

Avridine, a lipoidal amine with interferon-inducing and adjuvant properties, was an effective adjuvant for Newcastle disease antigen (NDA) in chickens. Eleven vaccine lots were evaluated: 2 commercial water-in-oil vaccines, 4 experimental oil emulsion vaccines, 4 avridine-containing vaccines, and a control lot of nonadjuvanted antigen. Avridine significantly enhanced the immunologic responses of chickens against NDA. Chickens vaccinated with the avridine-containing vaccines had significantly higher antibody titers (hemagglutination inhibition) than did chickens vaccinated with the commercial vaccines. Experimental oil emulsion vaccines prepared from the same antigens as avridine-adjuvanted vaccines induced higher hemagglutination inhibition antibody titers after primary but not after booster vaccination. Use of avridine as an adjuvant for NDA in vaccines for chickens induced immunologic protection rates similar to those induced by oil emulsion vaccines, without causing the reactogenic and tissue residue problems associated with the use of oil vaccines in chickens.