Protection of chickens against infectious bronchitis virus with a multivalent DNA vaccine and boosting with an inactivated vaccine

The protective efficacy of DNA plasmids encoding avian infectious bronchitis virus (IBV) S1, N, or M protein was investigated in chickens. Chickens were inoculated monovalently (with plasmid pVAX1-16S1, pVAX1-16M, or pVAX1-16N alone) or multivalently (combination of the three different plasmids, pVAX1-16S1/M/N). A prime-boost immunization protocol against IBV was developed. Chickens were immunized with the multivalent DNA vaccine twice and then boosted with an inactivated vaccine once. Antibody titers of the chickens immunized with pVAX1-16S1/M/N were much higher than those of the monovalent groups (p < 0.01). A protective rate up to 90% was observed in the pVAX1-16S1/M/N group. The serum antibody titers in the prime-boost birds were significantly higher than those of the multivalent DNA vaccine group (p < 0.01) but not significantly different compared to the inactivated vaccine group at 49 days of age. Additionally, the prime-boost group also showed the highest level of IBV-specific cellular proliferation compared to the monovalent groups (p < 0.01) but no significant difference was found compared to the multivalent DNA vaccine group, and the prime-boost group completely protected from followed viral challenge.

Isolation and biological properties of avian infectious bronchitis virus isolated from Shanxi province / 中国兽医学报

Five field strains of infectious bronchitis virus (IBV) were isolated from suspected flocks from different time and different regions of Shanxi province,respectively,and characterized by a series of systematic identification assays,such as morphological observation by electron-microscope,interfering with the propagation of NDV,virus pathological role to chicken embryo,virus pathological role to SPF chickens,hemagglutination activity,physiscochemical,and reverse transcription polymerase chain reaction(RT-PCR).The results showed:The typical coronavirus which the spherical virions 60-120 nm in diameter and surface covered with spike like corona were observed under electron-microscope)The propagation of NDV strain was seriously interfered by the 5 isolates respectively;The embryonated chicken egg passages of the 5 isolates could dwarf with chicken embryos;The five isolates had no hemagglutination activity,but after treatment with 1% trypsin,it can agglutinate chicken red blood cell.The strains are sensitive to chloroform and ethyl ether.The SPF chickens which inoculated with the 5 isolates showed clinical sign and result in respiratory and kidney diseases,flower-steak,and swollen with severe urate deposition.The specific fragments of N gene of the 5 isolates were amplified by RT-PCR,respectiveiy.On the basis of all above mentioned results,the 5 isolates were classified as IBV.The study got a good preparedness for further study on molecular epidemioogy of the 5 IBV isolates.