FIG. 1.

Schematic representation of genomic organizations of PRV mutants. Four strains of virus were used in this study. PRV-Becker (6), a wild-type laboratory strain, was used in a small group of animals to verify prior assessments of PRV virulence in visual circuitry (16). PRV-Bartha (5), an attenuated vaccine strain, was used for similar purposes and was the parental strain used for construction of PRV-BaBlu and PRV-D. Construction of PRV-BaBlu and PRV-D is described in Materials and Methods and has been reported previously (16, 38).