| Avian Infectious Bronchitis (IB) is a highy contacting viral infection of the domesticfowl (Gallus gallus, more commonly known as the chicken) by infectious bronchitis virus(IBV). It can cause respiratory disease, kidney inflammation with low production and poor quality of eggs.It result in enormous losses to pultry industry.Ten field virus were isolated from 23 flocks of fowl vaccinated with live Mass viral strain (H120)in seven araes in Anhui provivce between 2007 to 2008.These isolates were identified by pathological role to chicken embryo , returning pathogen to host ,hemagglutination activity and chicken embryo serum neutralization test.all facts of expriments provde that the ten virus strain is avian infectious bronchitis nephritis virus. Respectively they were named as AH/HF1,AH/HF2,AH/HF3,AH/CZ,AH/FY,AH/LA,AH/CH,AH/AQ,AH/HN and AH/XC strains.Using fixed virus to dilute blood and fixed blood to dilute virus,chicken embryo serum neutrali -zation test among ten isolates indicate that AH/HF2 strain is belong to Hotle serotype,which genesis cross -immune reaction with other strains isolated in Anhui,and take place complete cross -immune reaction with five strains.but H120 positive serum only genesis part cross -immune reaction with two strains.the pathogenicity of AH/HF2 and AH/HN were compared through histopathological examination,the results showed that AH/HF2 strain was individed into mixed-type (pathological lension in the upper respiratory tract,kidey and glandular stomach of nonimmuned chicken),but AH/HN is belong to intestinal tract type (pathological lesion in the intestinal tract and muscle of leg),there were two sorts of new clinical type after kidey-type and glandular stomach-type reported in Anhui province. viral culture in cell indicated that AH/FY strain could propagate in Vero cell monolayers and generate cytopathic effect(CPE),however,could not propagate in chick embryo fibroblast (CEF)monolayers.The four main structural protein genes of ten isolates were amplified by reverse trascriptase-polymersase chain reaction (RT-PCR).the results showed that the ORFof S1 genes of ten strains isolated in Anhui were composed of 1617bp to 1638bp,the ORF of S2 genes were composed of 1878bp,the ORF of M genes were composed of 678bp to 681bp,the ORF of N genes were composed of 1230bp.deletion,insertion and mutation were found in the nucleotide sequences and deduced amino acid sequences of S1genes and M genes of ten isolates comared with china isolates,vaccine strains and overseas strains,however, the N genes and S2 genes was more conserved among the four structural proteins,there were different degrees of variation within the whole N gene and S2 gene.The analysis of gene homologous recombination demonstrated that ten strains isolated in Anhui were directly or indirectly occurred within the part IBV strains of Jiangsu,Hebei, Shangdong,Jilin, Shangdong,Jilin,Helong-jiang,Xinjiang and Guangdong.The nucleotide identity and phylogenic relationships among the nucleotide sequences and deduced amino acid sequences of main structural protein genes derived from the ten isolates and the reference strains indicated that ten isolates were closely related with79.9﹪to 99.9﹪nucleotide sequence homology,according to S1 genes of ten isolates,they could be divided into subgroups,formed indigenous genotypes and higher hucleotide sequece identity were found among them.between the ten isolates the part of china isolates were closely related to ten isolates with 81.5﹪to 98.0﹪higher nucleotide sequence homology and divided into different groups.furthermore,among the main structural genes of ten isolates,vaccine strains used in china and overseas IBV strains except korea strains also indicated that they were no closly related with 76. 0﹪to 91.7﹪low nucleotide sequence identity and did no belong to the same as a group.
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