Molecular Characterization of Hyper Variable Region of the Classical and Very Virulent Egyptian Isolates of IBDV
Molecular Characterization of Hyper Variable Region of the Classical and Very Virulent Egyptian Isolates of IBDV
Seham A. El-Zeedy1, Dalia A. Abd El-Moaty1, H. A. Hussein2 and M. A. Shalaby2
ABSTRACT
Many recent outbreaks of Infectious bursal disease in commercial chicken flocks worldwide are due to the spread of very virulent IBDV. Two Egyptian isolates Of IBDV isolated from Giza (Giza/2000) and Qalyubia (Kal/2001) governorates were characterized by RT/PCR-RFLP assay of a 643 bp hyper variable region Of VP2 gene using BstNI, MboI, and SspI restriction enzymes. The presence of Sspl site in Giza/2000 identified it as vvIBDV while the absence of this site in Kal/2001 beside the obtained profile of BstNI and MboI restriction enzymes identified it as classic strain. This was confirmed by sequence analysis or these RT-PCR products of the hyper variable region and the deduced a.a sequence 183-360, has the highest identity on both nucleotide and amino acid levels 99.4% and 98.8% to the classical strains Cu-l, D78, and PBG-98, while Giza/2000 has the highest identity 98.3-98.1% on nucleotide level and 98.3% on a.a level to the vvIBDV. The multiple alignment of the two Egyptian isolates with different IBDV serotype I strains showed that isolate shared three unique a.a residues at positions 222A, 256I, and 294Ile that were found only in vvIBDV as well as the conserved serine rich heptapeptide region. Giza/2000 showed two additional unique a.a residues at positions 220Phe and 321Thr that resulted from two unique nucleotide substitution at positions 609 (A to T) and 911 (G to A). Surprisingly Giza/2000 shared the unique a.a residue at position 254 (Gly to Ser) with the American Var A. Del E and GLS. Giza/2000 isolate showed 9 nucleotide differences with 3 a.a substitution at positions 220Phe, 254Ser, and 321Thr from the Egyptian isolate at 1989 (K406/89) giving indication that circulating IBD viruses in Egypt still undergoing mutations.
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