Stability of the pseudorabies virus genome after in vivo serial passage

Restriction endonuclease patterns of pseudorabies virus (PRV) DNA were examined after each of 11 serial passages of the virus through pigs. Minor variations in the electrophoretic mobility of certain restriction enzyme fragments were observed by the sixth passage. This variability was similar to some of the minor variability observed in field isolates. The variable fragments were mapped to three locations on the PRV genome: the junction between the short unique sequences and the repeat sequences, the terminus of the long unique region, and an internal area of the long unique region.