QUANTIFICATION OF MAREKS-DISEASE VIRUS IN CHICKEN LYMPHOCYTES USING THE POLYMERASE CHAIN-REACTION WITH FLUORESCENCE DETECTION

A quantitative assay was developed for Marek's disease virus (MDV). Th e assay determines the numbers of viral genomes present in samples by polymerase chain reaction (PCR) amplification of a portion of the vira l genome for a restricted number of cycles. Fluorescent-tagged primers are used for the PCR amplification which allows quantification of the fluorescent product. Previously, quantitation of Marek's disease viru s has required plaque assays, which are laborious and potentially erro r-prone, and this has limited quantitative comparisons. The PCR assay is rapid, less laborious and can be applied to high levels of accuracy , since replicate assays can be carried out relatively easily. The PCR -based assay assesses the number of viral genomes present in the sampl e, rather than the numbers of infected cells measured in the plaque as say, however correlation between the two assays is high, suggesting vi ral copy number per cell may be rather uniform. In crosses between gen etically resistant and susceptible animals the PCR-based assay was cor related significantly with subsequent development of disease, and was a better predictor than the plaque assay of the likelihood of developm ent of pathological disease in the birds studied. (C) 1997 Elsevier Sc ience B.V.