Abstract
Infectious bursal disease virus (IBDV) is one of the most important immunosuppressive viral agents in poultry production. Prophylactic vaccinations of chicken flocks are the primary tool for disease control. Widely used immunoprophylaxis can, however, provide high pressure which contributes to the genetic diversification of circulating viruses, e.g. through reassortment of genome segments. We report the genetic and phenotypic characterization of a field reassortant IBDV (designated as Bpop/03) that acquired segment A from very virulent IBDV and segment B from classical attenuated D78-like IBDV. Despite the mosaic genetic make-up, the virus caused high mortality (80%) in experimentally infected SPF chickens and induced lesions typical of the acute form of IBD. The in vivo study results are in contrast with the foregoing experimental investigations in which the natural reassortants exhibited an intermediate pathotype, and underline the complex nature of IBDV virulence.
Highlights
Infectious bursal disease virus (IBDV) is a doublestranded RNA virus which belongs to the Avibirnavirus genus, Birnaviridae family
Detection of IBDV The rRT-PCR reaction confirmed the presence of IBDV in the examined flock and the presence of virus in inoculated SPF embryos
Further identification with conventional RT-PCR, sequencing and basic local alignment search tool (BLAST) searches of partial sequences of both segments revealed that the analysed VP2 gene sequence has high nucleotide identity to the very virulent D6948 strain (Accession Number AF240687) and VP1 gene sequence to the cell culture–adapted attenuated 903/78 strain (JQ411013)
Summary
Infectious bursal disease virus (IBDV) is a doublestranded RNA virus which belongs to the Avibirnavirus genus, Birnaviridae family. The virus possesses a bisegmented genome (segments A and B) within a nonenveloped icosahedral capsid and is the causative agent of an immunosuppressive disease of young chickens [1]. It is commonplace in nature that viruses with segmented genomes may exchange genetic material if they infect one cell at the same time. The genome of IBDV encodes for 5 viral proteins. VP2 is the major structural viral protein that builds the viral capsid [9] and contains an antigenic domain responsible for inducing secretion of neutralization antibodies [10]. The IBDV encodes its own RNA-dependent RNA polymerase designated VP1 that is responsible for the genome replication, transcription [11] and probably translation of virus protein [12].
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