Characterization of Polish infectious bursal disease virus strains by reverse transcription polymerase chain reaction combined with restriction enzyme analysis

Six Polish infectious bursal disease virus (IBDV) strains isolated from two epidemics on the turn of 1970/80 (early IBDV) and after 1990 (very virulent vvIBDV) were characterized by a reverse transcription/polymerase chain reaction (RT/PCR) and restriction enzyme analysis (REA) method. They were compared to classical IBDV (cIBDV): the F52/70 reference strain for European virulent IBDV, vaccine intermediate S706 strain, and intermediate plus 228E strain. The primers pair designed to amplify a 723 base pair (bp) fragment of the VP2 gene was used. The restriction enzymes SacI, BspMI, AccI and PdiI were used to differentiate the examined strains. SacI only cleaved cIBDV RT/PCR products, BspMI cleaved vvIBDV, AccI cleaved both vvIBDV and cIBDV, none of the RT/PCR products of early Polish strains was digested by these three enzymes. PdiI cuts all examined strains but only one cIBDV strain (S706). The results demonstrate that RT/PCR can be used to rapidly detect IBDV infections in chickens, and combined with REA, to differentiate Polish IBDV strains.