Genotype Of Infectious Bronchitis Virus And Genetic Diversity Of S1 Gene And N Gene

Avian infectious bronchitis virus (IBV), a member of Coronaviridae ,is a highly infectious,contagious and pathogenic in chickens, which mainly invaded chicken respiratory, urogenital and digestive systems. IBV could cause respiratory disease and eggs production losses and has a high rate of mortality. Further more, it is characterized by complex clinical symptom, pathological changes and various serotypes, which is a great thrill in poultry production.There are more than 20 kinds of serotypes of different IBV strains, but there was only a little cross-protection between them. Meanwhile, the serum Neutralization Test is trivial and cost a lot of time.,and it is too difficult to diagnose and prevent its infection. Gene sequencing and analysis would be an important methods to study the pathogenecity and evolution of IBV, and by this way it is easy to find that what the IBV is going next.In this paper, there were 17 IBVstrains isolated from several provinces such as Shandong, Sichuan et al during 1992-2008, and the S1 genes and N genes of them were amplified and sequenced, and then they were compared with that of the IBV reference strains published in GenBank. Alignment analysis of the S1 nucleotide and amino acids sequences (nt/aa) showed that there were amount of variations among field IBV strains, which indicated that the evolution of IBV S1 gene was diverse with only one of 17 IBV strains was high homologous with the vaccine strain H120 (rate was 5.88â„…), whereas that was less than 80â„… between H120 with ther others of China.Importantly, the amino acid substitutions, insertions were also found in Hign Variation Region I (HVR I) of these IBV isolates. Nonetheless, there was still a good synchronous relationship between gene S1, N enven partial segments of them and the whole genome of of IBV (S1:r=0.963;N:r=0.976), which could help us to have a better understanding to IBV. Furthermore, the distinctions among the prevailing strains and vaccine ones became more and more evident, which implies that there would be great variations in IBV isolates under the immune pressure due to the continuing H120 vaccination.The same took place to N gene. There was also a good relationships between gene S1 and N (r=0.645), which showed that genetic variation was consistent beteew S1 and N gene while showing somewhat differences.Alignment analsis of the S1 and N gene of diffrent IBVs were conducted, six genotypes were primarily divided by the homologies of their nucleotide acids and the other factors including identification times, areas and clinical pathologies. The results of the genotype classification was mostly similar between S1 or N gene. In detail, 30 of 40(75%)were same, while only 10 /40 (25%) disagree. More important, the divergence mainly existed in recent years since 2000, 6 of 13 strains classified results were inconsistent, the consistent was 53.8%, indicating the inconsistency between S and N genes, suggesting that there might be a possible recombination of IBV strains.