Identification and cloning of main immune anlage cDNA of infectious bursal disease variant strain virus

Abstract

Using Reverse Transcription Polymerase Chain Reaction (RT PCR) technique,the cDNA fragment with length of about 1350bp coding for immunodominant protein VP 2 of infectious bursal disease virus (IBDV) was amplified from Gz902,a variant strain isolated from Guangdong Province.The fragment digested with BgII and EcoRI were inserted into the BamHI/EcoRI sites of pBluescriptII KS vector,and the recombinant plasmid were transformed into E.coli strain XLI Blue.The positive recombinant colonies were identified by PCR and restriction endonuclease digestion.The nucleotide sequence of hypervariable region of VP 2 gene was analyzed using Autocycle DNA Sequencing kit.The result showed that the similarities of the DNA sequence of Gz902 strain with variant strain A,GLS and E are 98.9%,96.2%and 95.5% respectively.Comparing the deduced amino acid sequences,there is one amino acid changed in each of the two hydrophilc regions of Gz902 strain.At two positions (249 and 254),the amino acid residues of Gz902 strain are conserved in variant strain A,GLS and E,but differs from that of all the classical strains.These two amino acid residues can be regarded as the signature of variant strains of IBDV.