Analysis Of The Genome Of The Typical Ibv Strains In China And The Research Of The Pathogenicity

In recent years, there has been using the vaccine H120 extensively, but the kidney-type IBV occurs frequently, even the Mass-type IBV was isolated in 2007. In order to elucidate the characteristics and reseach the serotype of the predominant strains and evaluate the vaccine H120, 7 IBV typical strains were selected, which were isolated in China from 1997 to 2008. ck/CH/LDL/97â… was isolated from Proventriculus in Liao Ning province in 1997; tl/CH/LDT3/03 from kidney of a teal in Guang Dong province in 2003; ck/CH/LLN/98â… from Liao Ning province which was LX4-type and lack of 3a gene ; ck/CH/LSD/03â… from Shan Dong Province, which was also LX4-type, with 10aa deletion in 3a protein; ck/CH/LHLJ/07â…¦from the chicken vaccined by H120 and 4/91 in Qi Qihaer city Hei Longjiang Province in 2007,which was Mass-type. The ck/CH/LHB/08â… and ck/CH/LAH08â…¡isolated from He Bei Province and An Hui province respectively in 2008, were two viarants, which similarity of S1 gene compared with others except TCoV were 71.9%~87.7% and 69.9%~73.3% respectively.The genes of these strains were amplified through RT-PCR, then ligated to T vector, transformed into TG1 E.coli, cloned and seqnenced, analysed genes and genomes through computer softwares.It was found that the 5`UTR and 3`UTR sequence were conserved, which effects were practiced by their conserved second structure; the stem in pseudonodule were conserved but not loop; the fusion protein 1ab was cleaved into 15 small nsps; there were two mutations of amino-acid in ADRP:S130-L130, G132-R132, so maybe resulted into the lower activity; there no the cleavage site between nsp4 and nsp5 in ck/CH/LAH08â…¡, because of the mutation of A-T of the 8834th nt; there was a lack of 20aa in S gene, beceuse of the mutation of C-G of 23806thnt.The phylogenic trees which were constructed according to the genome, S1 gene, S2 gene, M gene, N gene, 3CLpaa sequence, showed that there were no recombination between all experimental strains; IBV genome order was the same as TCoV, but the lower similarty in sequence;the predominant strain in China was also the LX4-type strain; the vaccine of H120 could not provide complete protection; the characteristic of an IBV strain was reflected exactly only by the analysis of complete genome.The trial of the vaccine H120 against ck/CH/LHB/08â… and ck/CH/LAH08â…¡togather with the analysis of sequences showed that the Mass-type strains always existed though using H120 vaccine extensively in China.