鸡传染性支气管炎病毒基因型与血清型相关性初步研究

为研究鸡传染性支气管炎病毒(IBV)基因型与血清型之间的相关性,本研究以国内不同地区的17株IBV分离株、2株疫苗株(M41、W93)和1株强毒株(X株)为研究对象,经RT-PCR扩增获得20株IBV的S1基因并进行测序.将其分别与GenBank中的20株国内外参考IBV株的S1基因进行序列比较,绘制S1基因系统进化树...     

Emergence of novel strains of avian infectious bronchitis virus in Sweden

Infectious bronchitis virus (IBV) causes avian infectious bronchitis, an important disease that produces severe economic losses in the poultry industry worldwide. Recent IBV infections in Sweden have been associated with poor growth in broilers, drop in egg production and thin egg shells in layers. The complete spike gene of selected isolates from IBV cases was amplified and sequenced using conventional RT-PCR. Nucleotide and amino acid sequence comparisons have shown that the recent isolates bear 98.97% genetic similarity with strains of the QX-like genotype. The phylogenetic analysis revealed that strains predominant in the nineties, which were of the Massachusetts type, have been replaced by D388/QX-like strains, however the evolutionary link could not be established. The homology between the two genotypes was 79 and 81%. Remarkably, a strong positive selection pressure was determined, mostly involving the S1 subunit of the S gene. This strong selective pressure resulted in recombination events, insertions and deletions in the S gene. Two new isolates generated from recombination were found with nucleotide sequence diverging 1.7-2.4% from the D388/QX-like branch, indicating the emergence of a new lineage. The study demonstrates a constant evolution of IBV that might be in relation to increased poultry farming, trade and vaccine pressure. The findings underscore the importance of continuous monitoring to control spread of infections, as well as to timely adjust diagnostic methods, molecular epidemiological studies, development and use of vaccines that are adapted to the changing disease scenario.     

1株鸡传染性支气管炎病毒变异株的分子特征和抗原性分析

从山东省发病商品鸡群分离鉴定了1株鸡传染性支气管炎病毒,命名为CK/CH/SD09/005.S1基因序列分析发现,该株和同期分离的16个IBV流行株与疫苗株H120和491同源性分别为65.2％和66.0％.BLAST发现,CK/CH/SD09/005株仅与GenBank中3个广东分离株同源性较高(98.6％～98.8％),并形成独立的进化群.分别以H120和491为参考株,除了广泛的点突变,CK/CH/SD09/005 S1基因在多个位点发生了插入和缺失,CK/CH/SD09/005 N基因仅发生了点突变,没有基因插入和缺失;M基因除了发生点突变之外,分别在16～18和7～18位发生了碱基插入.鸡胚中和试验结果显示,CK/CH/SD09/005与H120和491均有交叉中和性,抗原相关性分别为0.18和0.09,应属于Mass和793/B之外新的血清型.结果表明,IBV S1基因可同时通过点突变、插入和缺失产生变异株,增加了免疫预防的难度.     

Coronavirus avian infectious bronchitis virus

Infectious bronchitis virus (IBV), the coronavirus of the chicken (Gallus gallus), is one of the foremost causes of economic loss within the poultry industry, affecting the performance of both meat-type and egg-laying birds. The virus replicates not only in the epithelium of upper and lower respiratory tract tissues, but also in many tissues along the alimentary tract and elsewhere e.g. kidney, oviduct and testes. It can be detected in both respiratory and faecal material. There is increasing evidence that IBV can infect species of bird other than the chicken. Interestingly breeds of chicken vary with respect to the severity of infection with IBV, which may be related to the immune response. Probably the major reason for the high profile of IBV is the existence of a very large number of serotypes. Both live and inactivated IB vaccines are used extensively, the latter requiring priming by the former. Their effectiveness is diminished by poor cross-protection. The nature of the protective immune response to IBV is poorly understood. What is known is that the surface spike protein, indeed the amino-terminal S1 half, is sufficient to induce good protective immunity. There is increasing evidence that only a few amino acid differences amongst S proteins are sufficient to have a detrimental impact on cross-protection. Experimental vector IB vaccines and genetically manipulated IBVs--with heterologous spike protein genes--have produced promising results, including in the context of in ovo vaccination.     

Pathogenesis of infectious bronchitis virus in vaccinated chickens of two different major histocompatibility B complex genotypes

Infectious bronchitis (IB) disease progression in vaccinated chickens after challenge was evaluated in a single commercial line of layer chickens presenting two different major histocompatibility complex (MHC) B complex genotypes. MHC B genotypes were determined by DNA sequence-based typing of BF2 alleles. In total, 33 B2/B15 and 47 B2/B21 chickens were vaccinated with an Ark-type IB virus (IBV) attenuated vaccine and challenged with Ark-type IBV field isolate AL/4614/98 14 days later. Additional chickens of both genotypes served as unvaccinated/challenged and unvaccinated/nonchallenged controls. Clinical signs, histopathologic analysis, detection of IBV genomes in tears, and IBV-specific immunoglobulin A (IgA) in tears were used to evaluate disease progression and immune response. The incidence of IBV respiratory signs was significantly higher in B2/21 than in B2/B15 MHC genotype birds. However, neither the severity and duration of respiratory signs nor the severity and incidence of histologic lesions differed significantly with MHC genotype. The levels of IBV-specific IgA in tears of vaccinated and challenged chickens did not differ significantly between MHC genotypes. IBV genomes were present in the tears of vaccinated and challenged birds, and the incidence of detectable IBV genomes did not vary significantly with MHC B genotype. From an applied perspective, these results indicate that vaccinated commercial outbred chickens with these MHC genotypes are equally resistant to IBV.     

传染性支气管炎病毒的鉴定

试验采用鸡胚接种和气管环培养相结合的方法,对IBV毒株进行培养鉴定,IBV经鸡胚传一代后再上鸡胚气管环培养可引起气管环纤毛运动停止,应用此法可以快速地进行IBV检测。     

Genotyping of avian infectious bronchitis virus in Iran: Detection of D274 and changing in the genotypes rate

The coronavirus avian Infectious bronchitis virus (IBV) poses economic threats to poultry farms worldwide, affecting the performance of both meat-type and egg-laying birds. To define the evolution of recent IBVs in Iran, a genetic analysis based on hypervariable nucleotide sequences of S1 gene was carried out. Tracheal swab samples were collected from 170 Broiler flocks during 2017. Ten tracheal swabs from each flock pooled. From a total number of 170 flocks tested, 84.71% found to be positive. Phylogenetic tree analysis revealed the presence of D274 as a first time in Iran. IS/1494/06 was showed to be dominant IBV type circulating in broiler farms with a significantly higher prevalence than other four genotypes. Considering fluctuations in QX-type prevalence in recent years, continuous monitoring is necessary to reduce economic consequences in layer and broiler farms. The findings highlight the importance of using modified vaccination strategies that are adapted to the changing disease scenario.     

A dot-immunobinding assay for infectious bronchitis virus

Common Whatman filter paper grade 1 and nitrocellulose membrane were compared for their sensitivity in a dot-immunobinding assay for detection of serum antibody titers to Arkansas avian infectious bronchitis virus (AIBV). For a blue to purple color detection, serum antibodies were bound to AIBV antigen adsorbed on the filter-paper discs or nitrocellulose membrane. Rabbit anti-chicken IgG horseradish-peroxidase (HRP) conjugate and hydrogen peroxide with 4-chloro-1-naphthol (HRP-color development reagent) were applied. The study indicates that very small amounts of antigen/antisera are needed for the dot-immunobinding assay. The test is sensitive, economical, and easy to run and can be completed within 6-8 hours.     

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。