Vaccine efficacy against Ontario isolates of infectious bronchitis virus

Infectious bronchitis (IB) is an economically important viral disease with worldwide distribution. Every country with an intensive poultry industry has infectious bronchitis virus (IBV). The virus rapidly spreads from bird to bird through horizontal transmission by aerosol or ingestion. Sentinel bird studies were carried out in southern Ontario and IBV has been isolated from layer flocks. Genetic analysis of the S1 region of the strains showed that they were not vaccine related. The pathogenicity of selected Ontario variants of IBV isolates was studied and the subsequent work was to determine the degree of protection against field isolates provided by a commonly used vaccine MILDVAC-Ma5 in Ontario. The protection was evaluated by challenging immunized chickens with the respiratory (IBV-ON1) and nephropathogenic (IBV-ON4) viruses. The mean vaccine efficacy for IBV-ON1 was 66.7% indicating that a Massachusetts serotype vaccine would provide some protection against IBV field isolates.     

Cross-immunity in chickens using seven isolates of avian infectious bronchitis virus

Groups of 75 chickens were each infected with one of 7 isolates of infectious bronchitis virus (Mass 41, Holland 52, SE 17, Ark 99, Clark 333, JMK, and Florida). Following recovery, they were challenged along with susceptible controls to the homologous and 6 heterologous isolates. Cross-immunity was determined by virus recovery 4 or 5 days post-challenge. Challenge with the homologous isolate resulted in 90-100% protection. Challenge with heterologous isolates gave variable results and an overall average resistance of 38%. The SE-17-recovered chickens had a 50% protection, whereas the Holland-52-recovered chickens ahd a 13.3% protection.     

Serologic and cross-protection studies with several infectious bronchitis virus isolates from Delmarva-reared broiler chickens

Five isolates, from broiler-type chickens, capable of causing acute respiratory disease were identified as infectious bronchitis virus (IBV). The agar-gel precipitin (AGP) test was effective in identifying the isolates as IBV. Virus-neutralization (VN) and cross-challenge tests indicated two of the isolates to be Massachusetts types and one to be a JMK type. The remaining isolates were different from strains normally encountered in chickens reared on the Delmarva Peninsula. One isolate, although serologically similar to the Connecticut strain, was able to infect Connecticut-virus-immune chickens. Another isolate was similar to Arkansas 99, a strain not previously reported in Delmarva.     

Preparing hemagglutinating antigen from isolates of infectious bronchitis virus

The hemagglutinating (HA) activity of 14 strains of infectious bronchitis virus (IBV) was investigated. The optimal conditions for IBV antigen preparation include inoculation of 10- or 11-day-old specific pathogen-free embryonated eggs and incubation for 30 hours at 37 C. Embryos were inoculated via the allantoic cavity with 0.1 ml of a low embryonic passage of the virus (10(7) to 10(8) EID50/ml). Allantoic fluid was harvested and pooled, and a 100-fold concentration of virus particles was achieved by centrifugation for 3 hours at 30,000 x g. Virus pellets were resuspended in Tris-hydrochloride buffer containing 3 units of phospholipase-C (type-1) enzyme/ml and incubated for 2 hours at 37 C. All IBV strains tested demonstrated positive HA activity with chicken red blood cells. The antigen was stored in liquid state or lyophilized at 4 C.     

Characterization of three infectious bronchitis virus isolates from China associated with proventriculus in vaccinated chickens.

Outbreaks of an avian disease in infectious bronchitis-vaccinated chickens in China have led to the characterization of coronaviral isolates Q1, J2, and T3, which were isolated from proventricular tissues of the affected young layer flocks. Serologic analysis revealed that they could induce high titers of infectious bronchitis virus (IBV) antibodies in inoculated specific-pathogen-free (SPF) chickens in indirect enzyme-linked immunosorbent assay but were not neutralized by antisera specific to the IBV serotype M41 and the Australian T strain. In a pathogenicity experiment, the clinical signs and related gross lesions resembling those of field outbreaks were reproduced in SPF chickens, and viruses were reisolated from the damaged tissues, including trachea, proventriculus, duodenum, and cecal tonsil. Sequence data demonstrated the complete S1 amino acid sequences of these isolates were almost identical despite recovery from geographically different areas in China and had 47.3%-82.3% similarity in comparison with the 47 published S1 sequences. On the basis of genotyping and limited serology, the three isolates, which were responsible for field outbreaks of the disease, might be a new IBV variant.     

Serological and molecular characterization of three enteric isolates of infectious bronchitis virus of chickens

Three coronaviruses isolated from the intestines of laying chickens were partially characterized. Serological and molecular assays indicated that the enteric coronaviruses are infectious bronchitis virus (IBV) isolates. Although the three isolates were recovered from three unrelated chicken flocks, their RNase T1-resistant oligonucleotide fingerprints were almost identical. The three isolates were not neutralized by antisera specific to IBV serotype Connecticut, but their RNase T1-resistant oligonucleotide fingerprints closely matched the fingerprints of strain Conn-46, a Connecticut serotype. This and the co-fingerprinting data suggested that the three field isolates may have emerged from the Connecticut virus through mutation(s). The mutation(s) apparently involved the S1 protein gene that determines the virus serotype.     

Isolation of avian infectious bronchitis virus from experimentally infected chickens.

Virus was recovered from the faeces of chickens infected at three or four weeks of age for more than 20 weeks after infection with commercial vaccines or with the T strain of avian infectious bronchitis virus (IBV). Virus was not recovered from the trachea, liver, spleen, bursa or kidneys of T strain infected birds longer than 29 days after infection at which point IBV was recovered from the bursa of a single infected bird. In a subsequent experiment IBV was recovered from the caecal lymph nodes and faeces of one of five birds 14 weeks after infection with a commercial vaccine but no virus was isolated from the trachea, kidneys, duodenum, bursa, ovaries or testes of any of the five birds at this time.     

1株QX基因型鸡传染性支气管炎病毒的致病性

通过对8日龄SPF鸡人工感染鸡传染性支气管炎病毒(IBV)QX株发病,分别在攻毒后3,7,30 d剖杀并采集气管、肺、肾、脾、胸腺、法氏囊制作病理组织切片。攻毒7 d后,采集上述器官相同部位进行免疫组织化学法分析。根据IBV-QX株NP基因的保守序列设计引物,构建质粒标准品,建立了IBV-QX Real-time PCR标准曲线,并跟踪检测试验鸡的口腔、泄殖腔排毒情况。此外,观察并记录了2组鸡的临床症状、体质量差异等信息。结果显示,发病初期(3 d),气管、肺几乎无明显病理变化,其他器官均出现不同程度的炎性反应;临床症状明显期(7 d),所涉及的器官均有不同程度的病理变化;发病后期(30 d),气管纤毛有所恢复,肺、脾炎性反应有所减轻,但肾脏和法氏囊的病变依然严重。免疫组织化学法检测到上述器官均有可见抗原聚集。30 d时被感染鸡的口腔、泄殖腔仍可检出病毒核酸。试验鸡临床症状明显,体质量差异显著。本试验旨在探究具有组织嗜性的IBV-QX毒株对宿主的免疫器官和该病毒的主要靶器官的病理损伤以及被损伤器官的自我修复情况,抗原分布差异,排毒规律等,为后续研究宿主免疫器官发挥天然免疫的相关机理打下基础,也为研发新的疫苗、相关药物的临床药效评价、制定合理的疫苗接种策略提供参考。     

鸡传染性支气管炎病毒广西分离株血清型的分析

应用病毒感染的鸡胚材料免疫新西兰兔的方法制备抗鸡传染性支气管炎病毒(IBV)单因子血清,然后在鸡胚气管环培养(Tracheal organ cultures,TOC)上对广西分离的7个IBV代表性毒株和3个常用疫苗株进行交叉病毒中和试验。结果显示,10个毒株被分为6个血清型。根据试验所得的R值,应用聚类分析法分析了各血清型毒株之间的亲缘关系,显示目前在广西流行的IBV野毒株之间以及其与疫苗株间的抗原性存在很大程度的差异,分属不同的血清型。同时还对IBV基因分型和血清分型之间的关系进行了探讨。     

鸡传染性支气管炎病毒M41株的致病性及排毒规律

本试验针对鸡传染性支气管炎病毒(IBV)呼吸型M41标准株的S1基因设计并合成引物,构建了阳性质粒标准品;经过不断优化建立了检测IBV-M41 SYBR GreenⅠReal-Time PCR标准曲线。通过对8日龄SPF鸡人工感染IBV-M41发病,采用Real-Time PCR方法跟踪检测其泄殖腔排毒情况;剖检并采集试验鸡的相关器官制作病理切片;在临床观察的基础上记录试验鸡的体质量、体温等指标。结果显示,所建立的检测方法重复性好,特异性高,最低可检测到28.3拷贝/μL的病毒核酸。人工感染病毒3～15 d后在鸡的排泄物中均检测到了病毒;攻毒组鸡临床症状明显,相关组织器官均呈现不同程度的病变。该病毒致病性试验、排毒规律和real-time PCR检测方法的建立,为IBV感染鸡作为实验动物模型进行相关药物的临床药效评价提供方法与依据。     

4个传染性囊病野毒株的致病性试验

传染性囊病(infectious brusal disease,IBD)是由传染性囊病病毒(infectious brusal disease virus,IBDV)引起的一种急性、高度接触性、高度传染性的病毒病.自20世纪60年代发现传染性囊病(IBD)以来,给世界养禽业带来了极大的损失.对养禽业影响更严重的是,欧洲国家及我国相继出现了vvIBDV方面的报道,其致死率达到了100%[1-4].     

Serotypes of avian infectious bronchitis virus isolates from field cases in Japan

Eight etiologic agents isolated from field cases in Japan were identified as isolates of infectious bronchitis virus by agar-gel diffusion, buoyant-density determination on sucrose-density centrifugation, and morphological study by electron microscope of the purified viruses. In studies of the antigenic relationships of the eight isolates and six known infectious bronchitis viruses, antigenic diversity of these viruses was recognized from the degrees of relatedness using a plaque reduction in the "constant-virus decreasing-serum" method.