Dear Colleagues,

Papillomaviridae are a heterogeneous and numerous family of small non-enveloped DNA viruses that infect all amniotes. Papillomaviruses have a double-stranded circular genome of approximately 8 kB in size that is extremely stable genetically. In fact, the mutation rate for this virus has been estimated at only 1 base pair every 10,000 years. On the other hand, high viral diversity has been found in humans and is still investigated in animals. To date, papillomaviruses (PVs) are classified in 54 genera, and the majority of the established papillomavirus (PV) diversity has been isolated from humans. Although debated, the current rule for the classification of papillomavirus is based on nucleotide sequence identity of the L1 ORF to delimitate variants, types and genera. Since the rate of isolation and characterization of new animals’ papillomavirus types has exploded, the classification has been improved by inclusion of other information such as common ancestry in phylogeny, genome organization, biology and pathogenicity. Moreover, the creation of an International Reference Center for animal PVs has been proposed. Indeed, even though human papillomaviruses have been the most studied due to their association with some human cancers, animal PVs have been identified in more than 80 different host species over the last fourteen years. Research has been focused mainly in macaques, cattle, horses and dogs, but further types of papillomavirus have been studied more deeply in order to better understand papillomavirus evolution and the different diseases that they can cause. In fact, some PVs cause asymptomatic infections in skin and mucosa and are considered part of the healthy mammalian skin microbiota, while others produce lesions from highly productive self-limited warts to fibropapillomas and cancer. Several methods are currently used for the identification of papillomaviruses in animal tissues, such as PCR, rolling circle amplification, high-throughput sequencing, electron microscopy and histopathology examination, but there is no standard method for the detection and identification of these viruses. Besides simultaneous detection of different papillomavirus types in the same specimen, co-infection of papillomavirus with other skin epitheliotropic viruses has been reported in animals and humans. Nevertheless, little information is available on the pathogenetic role and the molecular interaction between host and pathogens involved in the infection. This Special Issue will focus on identification of new or known papillomaviruses associated to different lesions in all animal species. We welcome submissions of original research and review manuscripts that cover any aspects related to PV infection, diagnosis and co-infection and also those that address mechanistic interactions between co-infecting pathogens.

Dr. Laura Gallina
Guest Editor

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• papillomavirus
• papillomatosis
• fibropapilloma
• oncogenesis
• co-infection