Sequence analysis of the VP2 gene hypervariable region of Iranian infectious bursal disease viruses
2009
Toroghi, Reza, Department of Veterinary Research and Biotechnology, Razi Vaccine and Serum Research Institute, Mashhad, Iran
Highy virulent strains of infectious bursal disease virus (IBDV) emerged in Iran in 1991, devasting Iranian poultry industry. In the present study, molecular characterization of recent Iranian IBD viruses prevalent in the country was carried out. Total 13 IBDV isolates collected from different parts of the country, mostly with the history of high mortality during 2002 to 2003 were used. Highly sensitive techinqe of reverse transcription – polymerase chain reaction (RT-PCR) could detect virus in clinical samples. The 643 bp PCR products generated by amplification of VP2 gene variable region were confirmed by their size in Agarose gel and nested –PCR technique. Deduced amino acid sequence analysis of VP2 gene variable region, comprising major virus neutralizing epitopes, revealed Iranian field isolates to be similar to each other and highly virulent IBDV isolates repoted from Europe and Japan. Howerer, most of these viruses could be differentiated from each other at nucleotid level. Out of total nucleotid changes found in Iranian field isolaters four resulted in amino acid changes at positions 222 (P to A) , 256 (V to I) , 294(Lto I) and 299 (N to S). Serin rich heptapeptide sequence ";SWSASGS"; reported to be conserved in pathogenic strains of IBDV was also conserved in Iranian field isolates. None of the field isolates was found to be an antigenically variant or atypical highly virulent IBDV. Phylogenetic analysis revealed that Iraian field isolates originated from the same sourece as that of European and Japanese highly virulent IBDV isolates. Key words: Infectious bursal disease virus, Sequence analysis, phylogeny, VP2
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