| The biologic toxins produced by bacteria and virus have important effects to organic metabolism and reproduction. The study on bacterial toxin at molecular level, especially, on complete nucleotide sequence determination of pathogenic micro-organism has make it possible to comprehend pathogenic micro-organism pathogenesis and its rule. Recently complete nucleotide sequences of near ten bacteria have been examined. All those works will bring a new opportunity to study the toxicity gene of coding bacterial toxicity protein, and to understand the toxicology of toxicity protein. But such research on virus is still falling behind relatively. In order to probe the malignancy of virus and its toxicology to cell and tissue, to analyze the function of main structural genes of viral genome in pathogencity and immune, to manufacture drugs, which prevent the virus with bacteria and to effective vaccine, genome must be analyzed.In this Paper, A field strain of Infectious Bronchitis Virus was isolated from proventriculus tissue, morphological observation by electron-microscope and the biological characterizations of the virus were studied, pairs of specific primers are designed and synthesized in correspondence with them, according to the published sequences of infectious bronchitis virus three structural protein (spike protein S membrane protein M nucleocapsid protein N) genes, the cDNA of SI gene , S2 gene, M gene. N gene of IB V isolate LX4 were amplified by RT-PCR and full sequences were first reported. The products were recovered with purification agent kit, and identified by restriction endonuclease, then it was ligated with pUC19 vector, transformed into E.coli DH5a competent cell. The clones identified to be positive through PCR and restriction enzymes digestion reaction were sequenced by Sanger's method, therefore the entire structural gene sequences were obtained. The sequences of the structural protein genes and deduced amino acid sequence of isolate LX4 were compared. By computer software, complete mainstructural genes sequence of IBV domestic strain and molecular characteristic genetic-variant analyses, and probably T cell and B cell epitopes of the main structural protein of infectious bronchitis virus were analyzed premently.1. The results of biological tests have demonstrated that allantoic fluid of the first passage virus didn't produce macroscopic pathogenic role to chicken embryos and after passaged for four times, gross lesions were observed in chicken embryo.The virus showed typical coronavirus under electron-microscope and it couldn't form plaque in CEF cells and could hemagglutinates chicken Red Blood cells after treatment with 1% trypsin. To surprise, The virus replicated in CEF cells also showed hemagglutination activity to chicken Red Blood cells. In addition, the SPF chickens which inoculated with the virus isolated from the chicken damaged tissue showed clinical sign and grow lesion, but it's gross lesion didn't resemble to those of field outbreaks.2. The sequence of SI gene from IBV-LX4 strain was consisted of 1614 bp from initiation codon ATG to the possible cleavage site of spike glycoprotein, encoding for a 18-amino signal-peptide with the N terminus of SI protein and a polypeptide of 537-amino acids. 19 highly conserved, potential glycosylation sites and 17 Cysteines residues were characterized with SI protein, Homology analysis showe that there were gene deletion -. substitution and insertion in all strains SI gene, The homogeneity of nucleotide and the deduced amino acids of S1 gene with 17 alien and domestic references strains were equally less than 80%. It indicated that the LX4 strain was the new variant differented from others alien references.3. The cloned S2 gene from LX4 strain was composed of 2023bp in length encoding for a polypeptide of 625 amino acid. The amino acids located between 560-600 are all hydrophobic, which were probably associated with the envelope membrane, there were 19 cysteines and 13 potential glycosylation sites in S2 protein, the cleavage r...
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