Molecular characterization of IBD virus isolated from Giza governorate, Egypt, 2014

Abstract

The emergence of new variant strains of the infectious bursal disease virus (IBDV) has been the cause ofserious economic losses in chicks. A field isolate of IBDV was recovered from suspected broiler chicks indifferent localities of Giza governorate in 2014. The virus was isolated on specific pathogen free -embryonated chicken eggs (SPF-ECE), detected by AGPT and confirmed by RT-PCR searching for VP2coding region of the serotype I IBDV. A total number of 26 out of 42 tested samples (61.9%) were positivefor virus isolation, AGPT and RT-PCR. Sequence analysis of the PCR product and genomic characterizationof the variable region of VP2 of the field isolate revealed amino acid substitutions in the hydrophilic regionA in the loops containing domains important for antigenic variation, binding of neutralizing antibodies andthe residues responsible for the viral virulence and cellular tropism. Studying homology and phylogeny ofthe isolated virus with the other reference classical, very virulent, variant and vaccinal strains of IBDVrevealed that IBDV Giza 2014 was in a separate branch and it was clustered more close to the Egyptian veryvirulent IBDV, Giza 2000 and Giza 2008 and the European and German IBDV but it was clustered at a fardistance from Hel 2008 IM, Hel 2008, Bursine Plus and other strains. It was concluded that genomiccharacterization of a variant IBDV which denote the continuous evolution and mutation of IBDV in Egyptwhich may affect the virus antigenicity and virulence