Novel snake papillomavirus does not cluster with other non-mammalian papillomaviruses

Papillomaviruses (PVs) are associated with the development of neoplasias and have been found in several different species, most of them in humans and other mammals. We identified, cloned and sequenced PV DNA from pigmented papilloma-like lesions of a diamond python (Morelia spilota spilota). This represents the first complete PV genome discovered in a Squamata host (MsPV1). It consists of 7048 nt and contains the characteristic open reading (ORF) frames E6, E7, E1, E2, L1 and L2. The L1 ORF sequence showed the highest percentage of sequence identities to human PV5 (57.9%) and Caribbean manatee (Trichechus manatus) PV1 (55.4%), thus, establishing a new clade. According to phylogenetic analysis, the MsPV1 genome clusters with PVs of mammalian rather than sauropsid hosts.

The members of the family Papillomaviridae are non-enveloped, icosahedral viral particles with a diameter of 50 to 55 nm and a small (~8 kbp), circular, double stranded DNA genome, which is transcribed into one single direction. The family may be divided into at least 29 genera with a vast number of species, types, subtypes, and variants of papillomaviruses (PVs), based on nucleotide identities of the L1 open reading frames (ORFs). Due to the high genetic diversity and the host range it is anticipated, that the family Papillomaviridae has a long evolutionary history, but details remain yet vague.
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DNA of PVs can be detected in a wide range of vertebrate species, thus far including humans, various other mammals, birds, and turtles. PVs have been found to play a role in several human diseases of the skin and mucous membranes. The DNA of PVs can be amplified from samples of clinical asymptomatic individuals, but more importantly their influence on the development of certain benign and malignant disorders was demonstrated repeatedly.

The sequences of three PVs from birds, namely the Chaffinch (Fringgilla coelebs), the Yellownecked Francolin (Francolinus leucoscepus) and the Timneh African gray parrot (Psittacus erithacus timneh), have been determined. Various data suggest the existence of sauropsid-specific PVs in association with papillomas in lizards, snakes, crocodiles and turtles. Sequences of the entire genome from two PVs of turtles were determined recently from the Loggerhead turtle (Caretta caretta) and the Green seaturtle (Chelonia mydas). Upon phylogenetic analysis, these five sauropsid PVs cluster together and appear clearly distinct from the PVs infecting mammalian species.

Here, we report on the cloning, sequence determination and phylogenetic analysis of a PV-specific DNA from the Australian diamond python (Morelia spilota spilota).

Samples from a diamond python with small black papillated and pedunculated exophytic skin proliferations were taken and stored at -20°C until processing.