Infectious bursal disease viruses: molecular differentiation of antigenic subtypes among serotype 1 viruses.

Published nucleotide sequence data for IBDV variant viruses (A and 1048E) and classic viruses (STC, 52-70, PBG98, Cu-1, and 002-73) were used to identify restriction enzyme sites that could potentially be used to differentiate these strains of IBDV. To test this hypothesis, the genomes of IBDV strains STC, MD, NC, and OH were converted to cDNA using reverse transcriptase (RT) and then amplified using the polymerase chain reaction (PCR). The PCR primers were selected from relatively conserved sequence regions in the VP2 gene, and they were used to amplify a 394-base-pair fragment. The restriction enzymes (RE) DraI, EcoRII, SacI, Sau3AI, StyI, and TaqI were tested for their ability to digest the RT/PCR products. The STC classic virus was SacI-, StyI-, and EcoRII-positive and DraI-, Sau3AI-, and TaqI-negative. The MD, NC, and OH viruses were DraI-, Sau3AI-, and TaqI-positive and SacI-, StyI-, and EcoRII-negative. The classic STC strain could be differentiated from the variant MD strain using the RT/PCR-RE assay. Based on these results and the presence or absence of other restriction sites that were predicted by published nucleotide sequence data, the RT/PCR-RE assay has the potential to differentiate IBDV isolates MD, A, and 1048E. Published nucleotide sequence data and the RT/PCR-RE results obtained using STC and MD indicated that variant viruses MD, A, and 1048E could be differentiated from classic viruses STC, 52-70, PBG98, Cu-1, 002-73, and NC.