Detection of the prototype of a potential novel genus in the family Papillomaviridae in association with canine epidermodysplasia verruciformis.

Epidermodysplasia verruciformis (EV) is a rare human genetic predisposition to develop flat warts, some of which subsequently undergo cancer transformation. Some human papillomaviruses (HPVs), i.e. HPV 5 and 8, have been associated with cancer development as a sequela of EV. As similar diseases have been observed in dogs, it was hypothesized that unknown canine papillomaviruses (CPVs) may exist and that they may be present in cases of canine EV. Consequently, DNA was extracted from a malignant lesion of a dog with EV and circular DNA was amplified by multiple-primed rolling-circle amplification (RCA). Indeed, sequence determination and analysis of the RCA-amplified and cloned DNA from a malignant canine EV lesion resulted in the detection and primary description of a third CPV (CPV3). Typical papillomavirus genes were identified, with deduced amino acid similarities ranging from 20 to 57 % for E1, E2, E6, E7, L1 and L2, respectively. According to the sequence of the L1 gene, which is used for papillomavirus classification, the new isolate meets the majority of criteria needed to declare detection of a novel genus among the papillomaviruses. Thus, CPV3 may represent the prototype of this novel genus. As the novel virus was found in a dog in association with lesions reminiscent of human EV, it should be interesting to test in the future whether this condition can be reproduced in experimental animals. If such were the case, a new model for EV could be established.