Detection of papillomavirus DNA in precancerous lesions of the ears of sheep.

Sixty-seven benign precancerous cutaneous lesions from the ears of 51 sheep were examined for papillomavirus DNA by hybridisation to radioactively labelled or biotinylated probes of bovine papillomavirus type 1 (BPV 1) DNA under varying conditions of stringency. An additional 16 precancerous lesions from other cutaneous sites on 15 sheep and 15 samples of lesion-free skin from nine sheep were similarly examined. Both total genomic and subgenomic probes were used. DNA from 10 aural lesions and one vulval lesion reacted with the probe in a manner indicative of the presence of episomal papillomavirus DNA. Papillomavirus DNA was detected at low stringency in eight of the 10 aural lesions and the vulval lesions, and at high stringency in two aural lesions. Three out of the 8 aural lesions that were positive at low stringency reacted when re-tested at high stringency. Hybridisation with one of the samples of lesion-free ovine skin produced occasional equivocal signals. One particular positive lesion, an ovine aural cutaneous horn, was studied in more detail. When treated with restriction endonucleases, its restriction enzyme pattern was the same as that for BPV 2 DNA with eight of twelve enzymes and the same as that for BPV 1 DNA with two of the twelve enzymes. It was concluded that this ovine papillomavirus was more closely related to BPV 2 than to BPV 1. The possibility that it could be a subtype of BPV 2 is discussed.