Genetic and pathogenic characterization of new infectious bronchitis virus strains in the GVI-1 and GI-19 lineages isolated in central China

Avian infectious bronchitis(IB)is a highly contagious infectious disease caused by infectious bronchitis virus(IBV),which is prevalent in many countries worldwide and causes serious harm to the poultry industry.At present,many commercial IBV vaccines have been used for the prevention and control of IB;however,IB outbreaks occur frequently.In this study,two new strains of IBV,SX/2106 and SX/2204,were isolated from two flocks which were immunized with IBV H120 vaccine in central China.Phylogenetic and recombination analysis indicated that SX/2106,which was clustered into the GI-19 lineage,may be derived from recombination events of the GI-19 and GI-7 strains and the LDT3-A vaccine.Genetic analysis showed that SX/2204 belongs to the GVI-1 lineage,which may have originated from the recombination of the GI-13 and GVI-1 strains and the H120 vaccine.The virus cross-neutralization test showed that the antigenicity of SX/2106 and SX/2204 was different from H120.Animal experiments found that both SX/2106 and SX/2204 could replicate effectively in the lungs and kidneys of chickens and cause disease and death,and H120 immunization could not provide effective protection against the two IBV isolates.It is noteworthy that the pathogenicity of SX/2204 has significantly increased compared to the GVI-1 strains isolated previously,with a mortality rate up to 60%.Considering the continuous mutation and recombination of the IBV genome to produce new variant strains,it is important to continuously monitor epidemic strains and develop new vaccines for the prevention and control of IBV epidemics.

Evolutionary implications of Avian Infectious Bronchitis Virus(AIBV)analysis

For developing efficient vaccines, it is essential to identify which amino acid changes are most important to the survival of the virus. We investigate the amino acid substitution features in the Avian Infectious Bronchitis Virus （AIBV） antigenic domain of a vaccine serotype （DE072） and a virulent viral strain （GA98） to better understand adaptive evolution of AIBV. In addition, the SARS Coronavirus （SARS-CoV） was also analyzed in the same way. It is interesting to find that extreme comparability exists between AIBV and SARS in amino acid substitution pattern. It suggests that amino acid changes that result in overall shift of residue charge and polarity should be paid special attention to during the development of vaccines.

Cloning and Sequencing of S Gene of Novel Variant of Infectious Bronchitis Virus ZJ971 Isolates in China

A novel proventriculopathogic variant (isolate ZJ971) of infectious bronchitis virus (IBV) was identified from enlarged proeventriculus of the sick chickens in the study. The S gene cDNA segment with 3.6 kb in length was amplified by RT-PCR with special primers from the ZJ971 viral isolate of (IBV) and cloned into plasmid pBluescript SK( + ). The recombinants containing S gene of IBV-ZJ971 isolate were identified by digestion of restriction enzyme EcoRI, BamHI and PCR amplification. The cloned S gene from isolate IBV-7J971 was composed of 3492 bp in length encoding for a polypeptide of 1080 amino acids. Comparing the nucleotide of S gene of IBV isolate ZJ971 with that of reported IBV strains Beaudette, M41, Ark99 and CuT2, the homology was 97.3%, 97.5%, 88.6% and 85.6%, respectively; and the homology of the deduced amino acids of S protein of IBV isolate ZJ971 was 96%, 96.3%, 86.1% and 83.1% respectively; especially, the mutation of 3241st nucleotide of S gene of IBV isolate ZJ971 from G to T resulted in the translating termination of S protein at 3240th nucleotide site.

A duplex RT-PCR assay for detection of H9 subtype avian influenza viruses and infectious bronchitis viruses

H9 s ubtype avian influenza virus（AIV） and infectious bronchitis virus（IBV） are major pathogens circulating in poultry and have resulted in great economic losses due to respiratory disease and reduced egg production. As similar symptoms are elicited by the two pathogens, it is difficult for their differential diagnosis. So far, no reverse transcription-polymerase chain reaction（RT-PCR） assay has been found to differentiate between H9 AIV and IBV in one reaction. Therefore, developing a sensitive and specific method is of importance to simultaneously detect and differentiate H9 AIV and IBV. In this study, a duplex RT-PCR（d RT-PCR） was established. Two primer sets target the hemagglutinin（HA） gene of H9 AIV and the nucleocapsid（N） gene of IBV, respectively. Spec ific PCR products were obtained from all tested H9 AIVs and IBVs belonging to the major clades circulating in China, but not from AIVs of other subtypes or other infectious avian viruses. The sensitivity of the d RT-PCR assay corresponding to H9 AIV, IBV and mixture of H9 AIV and IBV were at a concentration of 1×10^1, 1.5×10^1 and 1.5×10^1 50% egg infective doses（EID_（50）） m L^–1, respectively. The concordance rates between the d RT-PCR and virus isolation were 99.1 and 98.2%, respectively, for detection of samples from H9N2 AIV or IBV infected chickens, while the concordance rate was 99.1% for detection of samples from H9N2 AIV and IBV co-infected chickens. Thus, the d RT-PCR assay reported herein is specific and sensitive, and suitable for the differential diagnosis of clinical infections and survei llance of H9 AIVs and IBVs.

Effects of Traditional Chinese Herbal Medicine on Immune Organ Indexes and Macrophages Phagocytic Indexes in Chickens Infected by Infectious Bronchitis Virus

[ Objective] To study the therapeutic effects of traditional Chinese medicine prescriptions on infectious bronchitis （IB） and find a novel avenue for prevention and treatment of viral diseases in poultry. [Method] A total of 160 cockerels at the age of 15 d were divided into four groups randomly, including traditional Chinese medicine group, moroxydine control group, challenge control group and healthy control group. Except the healthy control group, other groups were challenged with infectious bronchitis virus （IBV） on Day 15. After 48 h post challenge, the traditional Chinese medicine groupand moroxydine control group were respectively administrated with Chinese herbal medicine prescription and moroxydine, continuously for 5 d. The immune organ indexes and macrephage phagocytic indexes were detected on Day 18, 24 and 30, respectively. [ Result] The immune organ indexes and macrophage phagocytic indexes were not significantly different between traditional Chinese medicine group and moroxydine control group on Day 18. But all the indexes of the traditional Chinese medicine groups were increased significantly （ P 〈 0.05） on Day 24 and 30, and showed extremely significant difference （ P 〈 0.01 ） with those of challenge control group on Day 30. [ Conclusion] The traditional Chinese herbal medicine can enhance macrophage phagocytic indexes and immune organs indexes of chickens infected by IBV.

Molecular Characteristics of S1 Gene of Infectious Bronchitis Virus Isolated from Chicken Proventriculus

Infectious bronchitis virus was isolated from swollen proventriculi of clinically ill chicken. The suspected virus samples (2/97, 3/97, 1/98) were adapted in SPF chicken embryos for virus isolation and identification. All the virus isolates were able to agglutinate chicken erythrocytes after treatment with trypsin, and interfer with the reproduction of Newcastle disease virus in chicken embryos, and have low antigenic relat-edness values with reference positive IBV. The isolates 2/97, 3/97, 1/98 RNAs extracted from the allantoic fluid of inoculated embryonated eggs were converted to cDNA by reverse transcription with 3'-primer of S1 gene of (IBV). Polymerase chain reaction (PCR) was performed with two primers which span the S1 gene. Amplified product of 1. 93 kb was subjected to EcoR I and BamH I digestion and the fragments obtained were the same as expected size. The PCR product was ligated to pBlueScript-SK ( + ) vector, and its nucleotide sequence was determined by the dideoxy-mediated chain termination method. Nucleotide sequence analysis showed 73. 6 - 99. 7% homology between the isolated IBV and the IBV strains in GenBank. The homology of amino acid was 71. 4 - 99.4%.

E Protein Prokaryotic Expression of Avian Infectious Bronchitis Virus

The small envelope protein （E） gene of avian infectious bronchitis virus （IBV） M41 strain was cloned, and then it was subcloned into prokaryotic expressing vector pGEX-6P-1. The recombinant plasmid was transformed into E.coli. BL21 and induced by IPTG. SDS-PAGE result showed that when objective protein fused with GST （about 20 ku）, the relative molecular mass of fusion protein was 38 ku. It indicated that objective protein was about 12.4 ku. The result showed that E protein was expressed successfully, it was useful to the subsequent E protein research.

Isolation and Identification of Avian Infectious Bronchitis Virus

[ Objective] The aim was to isolate and identify avian infectious bronchitis virus （IBV） from diseased chickens. [ Method] IBVs were iso- lated from the diseased chickens in a chicken farm in Anhui Province with blind passage method to observe virus pathogenicity. Then animal regres- sion test was made to replicate symptoms of bronchial congestion in SPF chickens and S1 gene segments were amplified and isolated, followed by comparison with IBV vaccine strains. [ Result] Detection of Hemagglutinating activity （HA） showed that allantoic fluid had no concerning effect on erythrocyte, suggesting that NDV and AIV were not included in the isolated viruses. However, the erythrocyte could be agglutinated with allantoic fluid treated with 1% of pancreatin, which is in consistent with biological characters of IBV. After SPF chickens were inoculated with the 6^th SPF al- lantoic fluid, bronchial congestion was replicated, proving that the isolated virus was avian IBV, named IBV XZ strain. [ Conclusion] This study pro- vides a theoretical basis for prevention of avian infectious bronchitis.

Prokaryotic Expression of Infectious Bronchitis Virus S1 Gene and Analysis of Biological Activity of Recombinant Protein

[Objective] To study the prokaryotic expression and antigenicity identification of S1 gene from avian infectious bronchitis virus （IBV）. [Method] The S1 gene was cloned into a pMD18-T vector to yield a recombinant plasmids pMD18-T-IBV-S1. Then S1 gene was inserted into the multiple cloning site of a prokaryotic expression vector pET-32a （ ＋ ）. The recombinant plasmid was transformed into E. coil BL21. The recombinant protein was induced by IPTG and measured by SDS-PAGE and western-blotting. [Result] The S1 gene was successfully expressed in E. coil BL21, the fusion proteins were about 66.0 kDa in a form of inclusion body. Western-blotting test showed that the recombinant proteins could be identified by IBV polyclonal antibody. [ Conclusion] The recombinant proteins of S1 gene have the antigenicity, which lays a good foundation for further research on new generation vaccine of IBV.

The Establishment of Fluorescent PCR Detection Method for Avian Infectious Bronchitis Virus

[ Objective] The aim was to to establish a kind of peculiar, sensitive and quick fluorescent PCR detection method. [Method] A peculiar, sensitive and quick method of fluorescent PCR detection for avian infectious bronchitis virus was established, the standard curve was built, specific primers, susceptibility and repeatability was detected. [ Result] This method diagnosed avian infectious bronchitis virus peculiarly, sensitively and quickly, simple and easy to use, time short, suitable for clinical testing. [ Conclusion] This research laid the foundation to diagnose avian infectious bronchitis virus.

Isolation and Identification of Avian Nephropathogenic Infectious Bronchitis Virus

In November 2009, a respiratory disease with rapid transmission, rapid onset and mortality of about 8% appeared many times in a large chicken farm in Jiangsu Province of China. Necropsy revealed tracheal bleeding, kidney enlargement and white-spotted kidney. An isolate from the farm was identified as an avian infectious bronchitis virus （IBV） by chicken embryo inoculation, hemagglutination assay, virus interference assay, animal regression and tracheal rings culture. The complete ,S1 gene was amplified by RT-PCR, and its homology to that of the vaccine strains com- monly used in China was analyzed with DNAStar software. Therefore, the IBV isolate was initially classified into nephropathogenic IBV and named IBV JS09 strain.

Responses of the Toll-like receptor and melanoma differentiation-associated protein 5 signaling pathways to avian infectious bronchitis virus infection in chicks

Avian infectious bronchitis virus(IBV) is a Gammacoronavirus in the family Coronaviridae and causes highly contagious respiratory disease in chickens. Innate immunity plays significant roles in host defense against IBV. Here, we explored the interaction between IBV and the host innate immune system. Severe histopathological lesions were observed in the tracheal mucosa at 3–5days post inoculation(dpi) and in the kidney at 8 dpi, with heavy viral loads at 1–11 and 1–28 dpi,respectively. The expression of m RNAs encoding Toll-like receptor(TLR) 3 and TLR7 were upregulated at 3–8 dpi, and that of TIR-domain-containing adapter-inducing interferon(IFN) β(TRIF) was upregulated at 21 dpi in the trachea and kidney. Myeloid differentiation primary response protein 88(My D88) was upregulated in the trachea during early infection. Tumor necrosis factor receptor-associated factor(TRAF) 3 and TRAF6 were upregulated expression in both tissues.Moreover, melanoma differentiation-associated protein 5(MDA5), laboratory of genetics and physiology 2(LGP2), stimulator of IFN genes(STING), and mitochondrial antiviral signaling protein(MAVS), as well as TANK binding kinase 1(TBK1), inhibitor of kappa B kinase(IKK) ?, IKKα, IKKβ,IFN regulatory factor(IRF) 7, nuclear factor of kappa B(NF-κB), IFN-α, IFN-β, various interleukins(ILs), and macrophage inflammatory protein-1β(MIP-1β) were significantly upregulated in the trachea and downregulated in the kidney. These results suggested that the TLR and MDA5 signaling pathways and innate immune cytokine were induced after IBV infection. Additionally,consistent responses to IBV infection were observed during early infection, with differential and complicated responses in the kidney.

The Efficacy of a Live Attenuated TW I-Type Infectious Bronchitis Virus Vaccine Candidate

Infectious bronchitis(IB) is a highly contagious avian disease caused by infection with infectious bronchitis virus(IBV),which seriously affects the development of the global poultry industry. The distribution of TW I-type IBV in China has increased in recent years, becoming a widespread genotype. We previously isolated a TW I-type IBV strain termed CK/CH/GD/GZ14 in 2014, but its pathogenicity and possibility for vaccine development were not explored. Therefore, this research aimed to develop a live-attenuated virus vaccine based on the CK/CH/GD/GZ14 strain. The wild type IBV CK/CH/GD/GZ14 strain was serially passaged in SPF embryos for 145 generations. The morbidity and mortality rate of wildtype strain in 14 day-old chickens is 100% and 80% respectively, while the morbidity rate in the attenuated strain was 20%in the 95 th and 105 th generations and there was no death. Histopathological observations showed that the pathogenicity of the 95th and 105th generations in chickens was significantly weakened. Further challenge experiments confirmed that the attenuated CK/CH/GD/GZ14 strain in the 95th and 105 th generations could resist CK/CH/GD/GZ14(5th generation)infection and the protection rate was 80%. Tracheal cilia stagnation, virus shedding, and viral load experiments confirmed that the 95 th and 105th generations provide good immune protection in chickens, and the immunogenicity of the 105th generation is better than that of the 95th generation. These data suggest that the attenuated CK/CH/GD/GZ14 strain in the105th generation may be applied as a vaccine candidate against TW I-type IBV.

Phylogenetic analysis of avian infectious bronchitis virus isolates from Morocco:a retrospective study(1983 to 2014)

Dear Editor,Infectious bronchitis(IB),one of the most common and difficult poultry diseases,is caused by a gammacoronavirus named infectious bronchitis virus(IBV).IBV frequently causes respiratory and/or renal diseases in chickens and egg production losses in hens.IB has

Preliminary Screening of Plant Ethanol Extracts Inhibiting IBV Proliferation

[ Objective] The paper was to study the inhibition effects of ethanol extracts from different plants on imCcctious bronchitis virus （ IBV ）. [Method ] Certain amount of plant ethanol extract was mixed with the recombinant virus IBV-3ab-luc inosculating luciferase gene at room temperature for 20 rain, and then added in H1299 cell culture system together. The activity of luciferase was detected after 24 h, to compare the inhibition effects of ethanol extracts from different plants on the virus. [ Result ] The logarithms of Gynura segetum leaf, Prunella vulgaris powder, Plantago asiatica leaf, Ophiopogon japonicus root, Lycium barba- rum fruit and Citrus reticulata were 4, 3,3,2,0 and 0, respectively. [ Conclusion] The ethanol extract from G. segetum leaf had the best inhibitory effect against IBV, followed by P. vulgaris powder, P. asiatica leaf, and O. japonicus root had relatively poor inhibition effect, whereas L. barbarum fruit and C. reticulata almost had no inhibition effect.