The genome of orf virus: Restriction endonuclease analysis of viral DNA isolated from lesions of orf in sheep

The purification of orf virus directly from scab material from clinical cases of orf in sheep and restriction endonuclease analysis of the viral DNA is described. Between 7×109 and 1.6×1011 virus particles, and 0.7 to 22.8 µg of viral DNA could be recovered from lg of scab material. Considerable heterogeneity was observed between different field isolates when restriction endonuclease digests of orf DNA were compared by gel electrophoresis. It was also shown, for two isolates, that these fragment patterns did not change after plaque purification and passage in cell culture. it is suggested that restriction endonuclease analysis of viral DNA offers a convenient method of identification of isolates of orf virus. The molecular weight of orf DNA was determined and found to be 88.8×106.