Sequence analysis of a part of hypervariable region of VP2 gene of chicken embryo fibroblast adapted Infectious Bursal Disease virus isolates of Uttarakhand

Infectious bursal disease (IBD) is an acute and highly contagious immunosuppressive viral disease of young chickens causing great economic loss to the poultry industry worldwide. The disease is caused by serotype 1 of IBD virus (IBDV) belonging to genus Avibirnavirus of family Birnaviridae. One of the most probable reasons for frequent vaccination failures is attributed to emergence of variant or very virulent strains. Hence the present study was carried out in an attempt to characterize the chicken embryo fibroblast culture (CEF) adapted IBD isolates which was originally characterized as very virulent in nature at molecular level. Amplification of 248 bp hyper variable region of VP2 gene was done by reverse transcription polymerase chain reaction (RT-PCR) using specific primers with RNA isolated from CEF culture infected with these field isolates. Though sequence and phylogenetic analysis of 248 bp RT-PCR product indicate that these field isolates are closely related to very virulent strains of virus there is change in nucleotide and amino acid sequences from virulent one which may be is due to cell adaption. However, further studies such as challenge studies, complete genome sequence analysis and site directed mutagenesis and reverse genetics approach will throw more light on correlation between genotypes and antigenic subtypes and pathotypes.