Isolation And Identification Of Yunnan IBV-WBL And Gene Evolution Analysis

Chickens Infectious bronchitis(IB)is an acute,highly contagious disease of chickens caused by Infectious bronchitis virus(IBV).Because of IBV mutation by IBV genome mutation,deletion,insertion and recombination among different strains of genomes,it is great difficult to the prevention and treatment of this disease.In order to keep attention on the biological characteristics and variability of infectious bronchitis virus(IBV)at any time,this study obtained an IBV-WBL strain from a chicken farm in Yunnan,sequenced and analyses of all genes.The IBV-WBL strain was identified by hemagglutination test,chicken embryo dwarf experiment,NDV interference test,RT-PCR identification and animal regression test.The results showed that IBV-WBL strain had no agglutination of chicken erythrocytes in hemagglutination test.In chicken embryo short experiment,the embryos of embryonic bodies were seriously bleeding.The kidney was enlarging.After 7 days' attacted,no death chicken anatomy showed bleeding,curly embryo,dwarf embryo phenomenon and white urate deposition;NDV interference test displayed 4 points of HA was different to NDV IV live vaccine control group;The IBV-WBL strain caused disease that the kidney was enlarged and the uric acid metabolic disorder,it resulted 100%of the 7-day-old SPF were infected and 50%chicks were died.The results showed that the total length of IBV-WBL strain(excluding Poly(A))was 2765 Int,and 6 ORPs were co-encoded.The whole gene of IBV-WBL strain was cloned,sequenced and analyzed.It showed the similarity between IBV-WBL strain and domestic isolate was between 86.2%and 94.7%.The similarity of S1 gene was 65.6%?86.9%with the main reference strain.Compared with the domestic common vaccine strain(H120,4/91,LDT3,YX10-D90),the similarity was 78%-85.2%.S1 gene were not clustered with the reference strain and distant from other continental isolates.The other genes S2,E,M,N and domestic reference strains clustered;Simplot recombination analysis indicated that similarity between IBV-WBL SI gene 1-750nt and TW2575/98,representativing TW I type representative strains,was 95%,similarity to 4/91 vaccine strains was less than 75%;The similarity of S1 gene 750-1620nt and 4/91 vaccine strains was higher than 98%,and the similarity with TW2575/98 was less than 80%.It was different from the main vaccine strains(H120,LDT3).The results showed that the S1 gene variation of IBV-WBL strain was larger.It is not poly with the current epidemic strains and vaccine poison.The S1 gene was recombined with type 4/91 and TW type I.