Real-time PCR for differential quantification of CVI988 vaccine virus and virulent strains of Marek's disease virus.

CVI988/Rispens vaccine, the 'gold standard' vaccine against Marek's disease in poultry, is not easily distinguishable from virulent strains of Marek's disease herpesvirus (MDV). Accurate differential measurement of CVI988 and virulent MDV is commercially important to confirm successful vaccination, to diagnose Marek's disease, and to investigate causes of vaccine failure. A real-time quantitative PCR assay to distinguish CVI988 and virulent MDV based on a consistent single nucleotide polymorphism in the pp38 gene, was developed, optimised and validated using common primers to amplify both viruses, but differential detection of PCR products using two short probes specific for either CVI988 or virulent MDV.

Variations in the H/ACA box sequence of viral telomerase RNA of isolates of CVI988 Rispens vaccine.

The use of the complete DNA sequence for the Marek's disease virus (MDV) serotype 1 vaccine strain CVI988 Rispens in comparative genomic studies with virulent strains of MDV has revealed the presence of a number of insertions, deletions and single-nucleotide polymorphisms. In this study, we investigated a SNP in the H/ACA box of the viral RNA subunit of telomerase (vTR). We sequenced vTR from four different batches of CVI988 vaccine originating from a single commercial company.