Domestic dogs are currently recognized as being infected by 25 different canine papillomavirus (CPV) types classified into three genera. A short sequence from a novel CPV type was amplified, along with CPV1, from a papilloma (wart) from the mouth of a dog. The entire 7499 bp genome was amplified, and CPV26 contained putative coding regions that were predicted to produce four early proteins and two late ones. The ORF L1 showed less than 62% similarity for all previously sequenced CPV types but over 69% similarity to multiple Omegapapillomavirus types from a variety of Caniform species including the giant panda, Weddel seal, and polar bear. Phylogenetic analysis confirmed CPV26 clusters within the Omegapapillomavirus genus. Specific primers were used to investigate the presence of CPV26 DNA within a series of 37 canine proliferative lesions. CPV26 DNA was amplified from one lesion, a cutaneous papilloma that also contained CPV6. This is the first time a PV type within the Omegapapillomavirus genus has been detected in a non-domestic species and this provides evidence that the omegapapillomaviruses infected a common ancestor of, and then co-evolved with, the Caniform species. Whether CPV26 causes disease is uncertain, but the absence of an E7 protein may suggest low pathogenicity.
Keywords: CPV; CPV26; Caniform; canine papillomavirus; dog; evolution; omegapapillomavirus; oral papilloma; papillomavirus.