Genetic characterisation of Felis catus papillomavirus type 7, a rare infection of cats that may be associated with skin cancer

Six Felis catus papillomavirus (FcaPV) types have been fully sequenceed from domestic cats including some that have been associated with the development of neoplasia. A sequence from a novel FcaPV type was amplified from a basal cell carcinoma that contained unusual histological evidence of PV infection and intense p16CDKN2A protein (p16) immunostaining. The entire 7467 bp genome was amplified using 'outward facing' primers. The PV was designated FcaPV7 and contained putative coding regions that were predicted to produce five early proteins and two late ones. The ORF L1 showed 77% similarity to that of FcaPV6. As the novel PV also showed greater than 60% similarity to three other feline Tau-PV types, FcaPV7 is proposed to be classified within this genus. Specific primers were designed but did not amplify FcaPV7 DNA from any of 60 samples from the mouth and skin of cats. FcaPV7 appears to rarely infect cats. However, FcaPV7 may be associated with skin cancer in this species.

Canine and feline papillomaviruses: an update

Papillomaviruses are small viruses able to cause disease not only in mammalians, but also in birds and reptiles. In recent years, a rising number of papillomaviruses have been identified in dogs and cats, totaling 24 canine papillomavirus (CPV) and six feline papillomavirus (FcaPV). The canine and feline papillomaviruses (CPVs and FcaPVs, respectively) are responsible for multiple lesions in these domestic species but the potential pathological relevance of some recently identified types remains to be determined. CPVs are associated with oral papillomatosis, cutaneous papillomas and viral pigmented plaques, and have been rarely associated with the development of oral and cutaneous squamous cell carcinomas in their canine hosts. FcaPVs are associated with oral papillomas, viral plaques, and Bowenoid in situ carcinomas. The present review provides readers with the more recent advances on dog and cat papillomavirus research, bringing an update on this field to both veterinary practitioners and the virology community at large.

Detection of a Novel Papillomavirus Type within a Feline Cutaneous Basal Cell Carcinoma

A 4 cm diameter exophytic mass was excised from the left flank of a 10-year-old domestic short-haired cat. Histology of the superficial aspects of the mass revealed epidermal cells arranged in nests and trabeculae while the deeper parts of the mass consisted of small round cells arranged in sheets or bundles of elongate spindle-shaped cells. A diagnosis of basal cell carcinoma (BCC) was made. Approximately 40% of the cells throughout the neoplasm contained prominent papillomaviral (PV)-induced cell changes. The BCC recurred three months after excision and grew rapidly. At this time a smaller mass was observed on the thorax. Due to the rapid recurrence of the BCC, the cat was euthanatized. As in the initial mass, histology of the recurrent mass revealed pleomorphic cells that often contained PV-induced cell changes. In contrast, the thoracic mass appeared as a more typical BCC and contained no histological evidence of PV infection. A novel PV DNA sequence was amplified from the flank BCC. While the sequence was most (75.1%) similar to Felis catus papillomavirus (FcaPV) 6, the level of similarity between the sequences is consistent with a novel PV type. No PV DNA was amplifiable from the thoracic mass. The case is unique due to the histological features of the BCC and the presence of a putative novel PV type. Observations from the present case add to the number of PV types associated with disease in cats as well as increasing the spectrum of PV-induced lesions in this species.

Papillomaviral skin diseases of humans, dogs, cats and horses: A comparative review. Part 1: Papillomavirus biology and hyperplastic lesions

Papillomaviruses (PVs) cause disease in humans, dogs, cats, and horses. While there are some differences, many aspects of the pathogenesis, presentation, and treatment of these diseases are similar between the four species. In this review, the PV-induced diseases of humans are compared to the similar diseases that develop in the companion animal species. By comparing with the human diseases, it is possible to make assumptions about some of the less common and less well-studied diseases in the veterinary species. In the first part of this review, the PV lifecycle is discussed along with the classification of PVs and the immune response to PV infection. The hyperplastic diseases caused by PVs are then discussed; including PV-induced cutaneous, anogenital, and oral warts within the four species.

Infectious Causes of Neoplasia in the Domestic Cat

Simple Summary

Increasingly, cancers are being linked to infections with viruses, bacteria, and parasites in human medicine. This review summarises the current literature regarding neoplasia occurring in association with infectious diseases in domestic cats. To date, most studies have focused on the role of viruses, especially feline leukaemia virus and feline immunodeficiency virus in association with lymphoma, or the role of papillomavirus in cutaneous and oral neoplasms in cats. Recently, there has been a focus on a potential role of mouse mammary tumour virus in feline mammary carcinoma and lymphoma and studies assessing the potential role of gammaherpes virus and hepadnaviruses in feline neoplasia. Additionally, there has been some focus on potential bacterial and parasitic associations with neoplasia; including reports assessing potential associations between Helicobacter species and gastrointestinal neoplasms, and case reports of neoplasia in association with Platynosomum fastosum and Opisthorchis viverrini.

Abstract

In recent years, growing attention has been paid to the influence/role of infectious diseases in tumour development and progression. Investigations have demonstrated that some infectious organisms can have a direct role in the development of neoplasia, whereas others can predispose to neoplasia by alterations in the immune response, or by creating a pro-inflammatory environment. Feline leukaemia virus was one of the first infectious agents recognised as an oncogenic organism, and along with feline immunodeficiency virus has received the most attention. Since the discovery of this retrovirus, several other organisms have been associated with neoplastic processes in cats, these include gammaherpes virus, mouse mammary tumour virus, papillomaviruses, hepadnavirus, Helicobacter species, and the parasitic infections Platynosomum fastosum and Opisthorchis viverrini. This review summarises the findings to date.

Sublingual papillomas of cheetahs in southern Africa

Nine distinct papillomaviruses (Lambdapapillomavirus) have been described in domestic and nondomestic cats, but not in cheetahs. These viruses have been associated with cutaneous papillomas or plaques, bowenoid in situ carcinomas, feline cutaneous squamous cell carcinomas (SCC), feline sarcoids, and oral (often sublingual) papillomas. Fourteen cheetahs from the AfriCat foundation (Namibia) and one from the Ann van Dyk Cheetah center (South Africa) presented with sublingual lesions reminiscent of sublingual papillomas. Two animals were biopsied and the histopathology revealed benign proliferative epithelial lesions with prominent thickening of the overlying squamous epithelium. Throughout the squamous epithelial layers were cells with nuclear enlargement, irregularity of the nuclear membranes and cell contours, focal hyperchromasia of the nuclei, and perinuclear halos, reminiscent of a virus-associated process as seen in papillomavirus infections. Thirteen more cheetahs were sampled and the tissue snap frozen for molecular characterization. Amplification and sequencing of the papillomavirus L1, E6, E7, and E1 gene regions was achieved with modified primers. Maximum likelihood phylogenetic analyses revealed all 15 cheetah papilloma samples were 99.99% genetically similar and closely related to, but genetically distinct from any known felinepapillomaviruses. All cheetahs were FIV and FeLV negative. The results suggest the samples identified in this study can be considered a previously undescribed or novel feline papillomavirus and the authors propose "Acinonyx jubatus papillomavirus type 1" (AjPV-1), within the Lambdapapillomavirus 1 genus (Family: Papillomaviridae).

Cutaneous papilloma associated with a novel papillomavirus sequence in a cat

A 5-mm diameter mass developed on the nasal planum of a 4.5-y-old castrated male domestic shorthaired cat; the mass was raised ~2 mm above the surrounding skin. Histology revealed focal thickening of the epidermis with marked orthokeratosis. Many of the epidermal cells within the mass had prominent papillomavirus-induced changes. A diagnosis of a viral papilloma was made, and a DNA sequence from a novel papillomavirus type was amplified from the lesion. Although the sequence was most similar to other feline papillomavirus types, the low level of similarity was suggestive of a novel papillomavirus genus. There has been no recurrence of the mass or development of additional lesions in the 6 mo since the mass was removed. This is the third cutaneous papilloma reported in a cat; a putative feline papillomavirus type has not been identified previously within these lesions, to our knowledge. Our findings expand the range of lesions associated with papillomaviruses in cats and increase the number of papillomavirus types that infect cats.

Papillomaviruses in Domestic Cats

Papillomaviruses (PVs) are well established to cause hyperplastic papillomas (warts) in humans and animals. In addition, due to their ability to alter cell regulation, PVs are also recognized to cause approximately 5% of human cancers and these viruses have been associated with neoplasia in a number of animal species. In contrast to other domestic species, cats have traditionally been thought to less frequently develop disease due to PV infection. However, in the last 15 years, the number of viruses and the different lesions associated with PVs in cats have greatly expanded. In this review, the PV life cycle and the subsequent immune response is briefly discussed along with methods used to investigate a PV etiology of a lesion. The seven PV types that are currently known to infect cats are reviewed. The lesions that have been associated with PV infections in cats are then discussed and the review finishes with a brief discussion on the use of vaccines to prevent PV-induced disease in domestic cats.

Detection of Felis catus papillomavirus type-2 DNA and viral gene expression suggest active infection in feline oral squamous cell carcinoma

Papillomavirus (PV) infection is associated with development of epithelial cancer in different species, including domestic cat (Felis catus). Felis catus PV type-2 (FcaPV-2) is considered the causative agent of a proportion of feline cutaneous squamous cell carcinoma (SCC), through the transforming properties of its E6 and E7 oncogenes. However, the possible role of FcaPVs in the aetiology of feline oral SCC (FOSCC) is still unclear. The aim of this study was to assess the presence and gene expression of FcaPV-2 in FOSCC samples. We detected FcaPV-2 DNA in 10/32 (31%) of the analysed FOSCC by the use of PCR methods. Importantly, viral mRNA was detected by RT-PCR in 7/10 (70%) of DNA positive samples. In particular, FcaPV-2 L1, E2 and E6E7 genes were found to be expressed in 5/10 (50%), 3/10 (33%) and 5/10 (50%) samples, respectively. Viral DNA was also detected in non neoplastic oral ulcerative lesions (ULs) (4/11, 36%); qPCR suggested a difference in viral load between ULs and FOSCCs, particularly in those expressing E6E7, although it was not statistically significant. These data suggest, but do not definively prove, a possible role of FcaPV-2 in the development of a proportion of FOSCC. Moreover, L1 and E2 gene expression results indicate that FcaPV-2 infection associated with these tumours may possibly be productive.

The Detection and Association of Canine Papillomavirus with Benign and Malignant Skin Lesions in Dogs

Papillomavirus (PV) mainly infects the squamous epithelium and may potentially lead to benign or even malignant cutaneous lesions. However, the malignant transforming ability has been identified in several types of PVs. In humans, papillomavirus (HPV) type 16 and 18 are the most prevalent causative agents of cervical cancer. Therefore, vaccines are being developed to protect against these types. For dogs, there have been limited investigations into the association of different canine papillomavirus (CPV) genotypes with malignant lesions. Understanding the high-risk CPV genotype(s) responsible for these malignant lesions would contribute to the development of interventions for preventing CPV-induced carcinomas. In the present study, a retrospective cohort of 102 pathologically confirmed papillomas and 212 squamous cell carcinomas (SCCs) were included. The viral genome and antigens in the formalin-fixed paraffin-embedded (FFPE) tissues were detected using PCR targeting pan PV E1 and COPV L1 genes and by immunohistochemistry staining (IHC), respectively. PVs were successfully detected from 11 FFPE cutaneous tissues and four oral tissues using pan PV E1- and COPV L1-based PCR, respectively. After sequencing, CPV 1, CPV 2, and CPV 6 were detected in the benign lesions using PCR and were confirmed through IHC. While CPV 9 and CPV 15 were first detected in the SCCs of dogs, CPV 16 was most often detected in SCC specimens. The association and confirmative demonstration of viral genes and intralesional antigens of CPV 9, CPV 15, and CPV 16 in SCCs highlight the potential risk of these genotypes of CPVs in malignant transformation.

Spindle cell sarcomas, suggestive of peripheral nerve sheath tumours, arising in the tongues of two cats

Case summary

Two domestic shorthair cats, one an 11-year-old female neutered cat and the other a 13-year-old male neutered cat, presented with partly raised, well-demarcated masses at the rostral tip of the tongue. Histological examination and immunohistochemical staining were consistent with sarcomas, and were most suggestive of peripheral nerve sheath tumours. One tumour had histological features consistent with a malignant peripheral nerve sheath tumour (PNST).

Relevance and novel information

Feline PNSTs arising on the tongue are rarely described in the published literature, and, to our knowledge, a case of malignant PNST originating at this site has not been described to date. Therefore, this represents a new differential diagnosis for cats presenting with a lingual mass. Regardless of histological malignancy, in cats these tumours have the potential for local recurrence but appear very unlikely to metastasise.

Papillomavirus DNA is not Amplifiable from Bladder, Lung, or Mammary Gland Cancers in Dogs or Cats

Simple Summary

Papillomaviruses (PVs) are well established to cause genital and oral cancer in humans. Additionally, some evidence suggests that these viruses may also have a role in the development of human lung, breast, and bladder cancer. Recent studies have revealed that PVs can influence the development of some cancers in cats and, less frequently, in dogs. In the present study, 47 lung, mammary gland, and bladder cancers in dogs and 25 cancers in cats were evaluated for evidence of any role PVs may have in cancer development. Histology did not reveal any lesions suggestive of PV infection, and no PV DNA was amplified from any cancer. Therefore, these findings suggest that PVs do not frequently infect these tissues and are therefore unlikely to be significant factors in the development of lung, mammary gland, or bladder cancer in either dogs or cats.

Abstract

Papillomaviruses (PVs) cause around 5% of all human cancers, including most cervical cancers and around a quarter of all oral cancers. Additionally, some studies have suggested that PVs could cause a proportion of human lung, breast, and bladder cancers. As PVs have been associated with skin cancer in cats and, more rarely, dogs, it was hypothesized that these viruses could also contribute to epithelial cancers of the lung, mammary gland, and bladder of dogs and cats. Formalin-fixed paraffin-embedded samples of 47 canine and 25 feline cancers were examined histologically for evidence of PV infection. Additionally, three sets of consensus PCR primers were used to amplify PV DNA from the samples. No histological evidence of PV infection was visible in any of the cancers. DNA from a bovine PV type was amplified from one sample, while two different samples were found to contain human PV DNA. However, these were considered to be contaminants, and no canine or feline PV types were amplified from any of the cancers. These results suggest that PVs do not frequently infect the lung, mammary gland, or bladder of dogs and cats and therefore are unlikely to be significant factors in the development of cancers in these tissues.

Felis catus Papillomavirus Types 1, 2, 3, 4, and 5 in Feline Bowenoid in Situ Carcinoma: An In Situ Hybridization Study

Several studies based on histopathology or molecular investigations suggest a causal relation between Felis catus papillomavirus (FcaPV-2) infection and bowenoid in situ carcinoma (BISC) in cats. Nevertheless, data on distribution of viral DNA for different F. catus papillomavirus types (FcaPV-1, 2, 3, 4, 5) in precancerous skin lesions are lacking. In this study, incisional and excisional skin biopsies from 18 cats with BISC were investigated for the presence of FcaPV DNA by quantitative polymerase chain reaction (qPCR) and chromogenic in situ hybridization (CISH) using specific probes to detect each of the FcaPVs that have been identified so far. By qPCR analysis, 15 of 18 samples were positive for FcaPV-2, 2 were positive for FcaPV-4, and 1 sample was negative for all FcaPVs studied. Two cases were positive for FcaPV-5 by qPCR only. FcaPV-1 and FcaPV-3 were not detected by either method. CISH positivity for FcaPV-2 and FcaPV-4 was 100% concordant with qPCR. FcaPV-2 CISH signal was observed as nuclear dots within grouped neoplastic keratinocytes in 12 BISCs and in the perilesional skin of 9 biopsies. In 3 of these 9 cases, the signal was not observed within the BISC. FcaPV-4 CISH positivity was detected only within BISCs in 2 cases. The overall rate of concordance for FcaPV detection between PCR and CISH was 97.8%. This study suggests that CISH is a reliable method to detect FcaPV-2 and FcaPV-4 infection in cats and provides useful information on the type, rate, and localization of infected cells.

Increased p16CDKN2A, but not p53, immunostaining is predictive of longer survival time in cats with oral squamous cell carcinomas

Although oral squamous cell carcinomas (SCCs) are common in cats there are currently few prognostic markers for these cancers. This study used 52 feline oral SCCs to determine if prognosis can be predicted by the age or sex of the cat, the presence of bone within the diagnostic sample, or the anatomic location of the SCC. Additionally, as p16^CDKN2A protein (p16) and p53 are prognostic for human oral SCCs, p16 and p53 immunostaining was evaluated. Only SCC location and p16 immunostaining were prognostic. Cats with oropharyngeal SCCs had an estimated median survival time (MST) of 151 days which was significantly longer than cats with maxillary (51 days P = 0.017), sublingual (33 days P = 0.011) and mandibular (34 days P = 0.029) SCCs. Overall, 19% of oral SCCs were p16-positive with intense nuclear and cytoplasmic immunostaining within most neoplastic cells, 69% had cytoplasmic immunostaining that was confined to the periphery of nests of neoplastic cells, and 12% had no p16 immunostaining. Cats with p16-positive SCCs had a MST of 87 days, which was significantly longer than cats with p16-peripheral SCCs (MST 37 days, P = 0.03), but not longer than cats with p16-negative SCCs (MST 51 days, P = 0.72). No papillomaviral DNA was amplified from the p16-positive SCCs. Twenty (39%) SCCs contained immunostaining for p53, but this was not prognostic (P = 0.31). These results suggest that feline oral SCCs develop by cellular mechanisms that result in one of three patterns of p16 immunostaining. Cancers which develop due to these mechanisms appear to have different clinical behaviors and p16 immunostaining predicts the behavior of these common feline cancers.

Felis catus papillomavirus type-2 E6 binds to E6AP, promotes E6AP/p53 binding and enhances p53 proteasomal degradation

E6 from high risk human papillomaviruses (HR HPVs) promotes ubiquitination and degradation of p53 tumour suppressor by mediating its binding to ubiquitin ligase E6AP in a ternary complex, contributing to cell transformation in cervical cancer. We have previously shown that Felis catus papillomavirus type −2 (FcaPV-2) E6 is expressed in feline squamous cell carcinoma (SCC) and displays the ability to bind p53 and decrease its protein levels in transfected CRFK cells. However, the mechanism of p53 downregulation has not yet been characterized. Here we show that FcaPV-2 E6 bound to E6AP, which in turn was bound by p53 exclusively in cells expressing the viral oncoprotein (CRFKE6). Furthermore, p53 was highly poly-ubiquitinated and underwent accumulation upon E6AP gene knockdown in CRFKE6. Half-life experiments and proteasome inhibition treatments indicated that down-regulation of p53 protein in CRFKE6 was due to accelerated proteasomal degradation. E6AP/p53 binding was also demonstrated in two feline SCC cell lines expressing FcaPV-2 E6, where p53 protein levels and poly-ubiquitination degree were proportional to E6 mRNA levels. The data obtained in both artificial and spontaneous in vitro models suggest that FcaPV-2 E6 degrades p53 through a molecular mechanism similar to HR HPVs, possibly contributing to the development of feline SCC.

Novel viruses: Update on the significance of papillomavirus infections in cats

PRACTICAL RELEVANCE

Prior to 1990 papillomaviruses (PVs) were not recognised to infect or cause disease in domestic cats. Since this time, the use of histology, immunohistochemistry and, more recently, molecular techniques has revealed that PVs almost certainly cause feline viral plaques and Bowenoid in situ carcinomas, oral papillomas and feline sarcoids. In addition, there is increasing evidence that PVs play a significant role in the development of feline cutaneous squamous cell carcinomas, one of the most common skin cancers of cats. Recent studies have also revealed that most cats are asymptomatically infected with PVs. This raises a critical question that is currently unanswered: why do only a small proportion of infected cats develop disease? In the future it may be possible to prevent PV-induced diseases by using a vaccine to prevent PV infection. Alternatively, novel therapies may be developed that prevent PVs from causing clinical disease by stimulating the host immune response.

CLINICAL CHALLENGES

A recognition of the skin diseases caused by PVs is important to more accurately predict disease progression. Unfortunately, there are currently no non-surgical treatments that have been proven to be beneficial in cats and clinical management of PV-induced skin disease in cats can be challenging.

GLOBAL IMPORTANCE

PVs have a worldwide distribution and negatively impact feline health and welfare globally.

AUDIENCE

This review is aimed at clinicians, especially those who regularly treat cats with skin disease. The review will also be useful to oncologists and researchers who have an interest in how cancer develops in cats.

EVIDENCE BASE

In producing this update the authors have drawn on recently published peer-reviewed literature.

Detection of felis catus papillomavirus type 3 and 4 DNA from squamous cell carcinoma cases of cats in Japan

Association of felis catus papillomaviruses (FcaPVs) with feline squamous cell carcinoma (SCC) has been reported worldwide, while there is limited information about FcaPVs in Asia. In this study, 21 feline SCC biopsy samples from cats in Japan were analyzed by PCR with PV consensus primers and type-specific primers for FcaPV type 2 (FcaPV-2), FcaPV-3 and FcaPV-4 designed in this study. Sequence analysis revealed that one sample was FcaPV-3, and two were FcaPV-4. In both FcaPV-4 positive samples, 334th tryptophan in L1 ORF was deleted compared with the reference sequence. Moreover, immunohistochemistry showed that p16 protein was positive in both FcaPV-4 detected samples. This study would contribute to the molecular epidemiological and pathological understanding of FcaPV in Japan.

Skin as a marker of general feline health: Cutaneous manifestations of infectious disease

Practical relevance: Infectious disease in feline patients often presents a diagnostic challenge. This article reviews the most relevant viral, bacterial and protozoal diseases and their cutaneous manifestations. Many of the diseases discussed have overlapping presentations or may mimic more common noninfectious disease processes. The purpose of the article is to reinforce knowledge of common and uncommon infectious diseases, help practitioners identify possible infectious dermatoses, create a comprehensive and prioritized differential list, and provide guidance for the diagnosis of these diseases. A working knowledge of these clinical syndromes is important if what is thought to be a case of a common disease does not respond to conventional management.

AUDIENCE

This review is aimed at veterinarians who treat cats and especially those with an interest in feline dermatology. Tables are included to allow the reader to formulate a concise list of differential diagnoses for clinically similar presentations. The diagnostic approach to a case of ulcerative facial dermatitis is reviewed in a Case Notes quiz. Evidence base: This article includes up-to-date information regarding dermatologic manifestations of less commonly encountered feline cutaneous infectious diseases. Information has been drawn from the published, peer-reviewed literature and the most recent textbook chapters with a particular aim of describing and differentiating clinical lesions and the diagnostic approach to cutaneous disease, especially in unusual cases.

Felis catus papillomavirus type-2 but not type-1 is detectable and transcriptionally active in the blood of healthy cats

Papillomaviruses (PVs) are small DNA viruses that induce benign and/or malignant epithelial tumours in different species, including the domestic cat (Felis catus). To date, five F. catus papillomavirus genotypes have been identified (FcaPV-1 to FcaPV-5). FcaPV-1 is associated with skin and oral benign lesions, while FcaPV-2 infection is widely associated with feline squamous cell carcinomas. Several human and animal PVs have been found in body fluids such as peripheral blood; however, the presence of FcaPVs in non-epithelial tissues has not previously been investigated. The aim of this study was to assess the presence and gene expression of FcaPV-1 and FcaPV-2 in the blood of healthy cats. We detected FcaPV-2 DNA in 26 of 103 (25%) blood samples. Importantly, FcaPV-2 L1, E2, E6 and E7 genes were found to be expressed in 3 (25%), 11 (92%), 6 (50%) and 5 (42%) of the samples available for mRNA analysis, respectively. FcaPV-1 was not detected in any of the blood samples analysed here. The data obtained in this work suggest active and eventually productive infection of FcaPV-2 in the blood of healthy cats, implying a possible role in intra-individual spreading as well as in vertical and horizontal transmission.

A study of multiple Felis catus papillomavirus types (1, 2, 3, 4) in cat skin lesions in Italy by quantitative PCR

Objectives The aim of the study was to investigate, by quantitative PCR (qPCR), the presence of papillomavirus in feline viral plaques (VPs), Bowenoid in situ carcinoma (BISC), squamous cell carcinoma (SCC) and actinic keratosis (AK). Methods Twenty-nine cases with previously established diagnoses of feline VPs, BISC, invasive SCC and AK were selected from a dermatopathological database. A critical re-evaluation of diagnosis was performed by defining clear criteria toward carcinomatous vs non-carcinomatous, in situ vs invasive (if carcinomatous) and viral vs actinic. Cases were evaluated for p16 immunolocalisation. The presence of the target viral genes for Felis catus papillomavirus (FcaPV)-1, FcaPV-2, FcaPV-3 and FcaPV-4 was determined by qPCR. The data generated ΔΔCq values, which represent a normalised measure of DNA viral quantity. Samples with a positive ΔΔCq value were submitted to sequence analysis. Results Four VPs, 19 BISCs, four SCCs and one case of AK were included. By ΔΔCq analysis we found that all VPs were positive for FcaPV-1 or FcaPV-2; eight BISCs were positive for FcaPV-1, FcaPV-2 and FcaPV-4. FcaPV-2 was the most prevalent among the group of VPs and BISCs. Conclusions and relevance Using the ΔΔCq method we report the first evidence of FcaPV-1, FcaPV-2 and FcaPV-4 in Italy. FcaPV-2 was the most frequently detected; to a lesser extent, FcaPV-1 and FcaPV-4 were detected in the examined samples. FcaPV-3 was never associated with viral-induced lesions by ΔΔCq investigation. Compared with conventional PCR the ΔΔCq method has the advantage of establishing a possible role of the virus in the outcome of infection.

Papillomaviruses in dogs and cats

Papillomaviruses (PVs) cause disease in both dogs and cats. In dogs, PVs are thought to cause oral papillomatosis, cutaneous papillomas and canine viral pigmented plaques, whereas PVs have been rarely associated with the development of oral and cutaneous squamous cell carcinomas in this species. In cats, PVs are currently thought to cause oral papillomas, feline viral plaques, Bowenoid in situ carcinomas and feline sarcoids. Furthermore, there is increasing evidence that PVs may also be a cause of cutaneous squamous cell carcinomas and basal cell carcinomas in cats. These diseases are discussed in this review. Additionally, there is a brief overview of PV biology, including how these viruses cause disease. Diagnostic techniques and possible methods to prevent PV infection are also discussed.

Multiple viral plaques with sebaceous differentiation associated with an unclassified papillomavirus type in a cat

CASE HISTORY AND CLINICAL FINDINGS A 15-year-old neutered male domestic short-haired cat was presented due to multiple 0.5-2 cm-diameter crusting plaques in the left preauricular region, over the bridge of nose, and in the right periocular region. The plaques did not appear to cause discomfort. HISTOPATHOLOGICAL FINDINGS Biopsy samples of four plaques were examined histologically. Three plaques consisted of well-demarcated foci of mild epidermal hyperplasia overlying markedly hyperplastic sebaceous glands. Approximately 60% of the hyperplastic cells contained a large cytoplasmic vacuole that ranged from being clear to containing prominent grey-blue fibrillar material. The fourth plaque was composed solely of epidermal hyperplasia, consistent with previous descriptions of feline viral plaques. MOLECULAR BIOLOGY Papillomavirus DNA was amplified from all four plaques using PCR. A single DNA sequence was amplified from the plaques with sebaceous differentiation. This sequence was identical to the FdPV-MY sequence previously suggested to be from a putative unclassified papillomavirus type. Felis catus papillomavirus type 2 sequences were amplified from the plaque typical of feline viral plaques. Immunohistochemistry to detect p16^CDKN2A protein (p16) showed marked immunostaining throughout the hyperplastic epidermis and adnexal structures within the plaques with sebaceous differentiation. DIAGNOSIS Multiple feline viral plaques with variable sebaceous differentiation. CLINICAL RELEVANCE Feline viral plaques with sebaceous differentiation have not been previously reported in cats. The presence of unique cell changes within these lesions, the detection of an unclassified papillomavirus type, and the p16 immunostaining within these plaques suggest that they may have been caused by the papillomavirus that contains the FdPV-MY sequence.

An Update on Canine, Feline and Bovine Papillomaviruses

Over recent years, a growing number of papillomaviruses have been identified, which cause a wide range of lesions in domestic and wild animals. Papillomavirus-induced lesions may have a great impact on animal health, and some diseases observed in farm animals are associated with significant economic losses. This concise review brings together recent advancements on animal papillomavirus research, providing the scientific community and veterinary practitioners with an update on this rapidly evolving field. Among others, bovine, canine and feline papillomaviruses (BPV, CPV and FcaPV) are most extensively discussed, in view of the recent discovery of new viral types and their worldwide importance for animal health. Feline papillomaviruses 2 is an emerging, highly prevalent pathogen in domestic cats, associated with a subset of malignant skin lesions. Aspects related to cross-species infection by BPV and its environmental co-factors are also addressed. Animal papillomaviruses are also fascinating models for studying molecular and cell biology and have recently inspired some major breakthroughs. Overall, it is clear that additional, international and systematic efforts are needed to clarify which lesions are caused by which viral types and to develop experimental models for studying animal papillomavirus.

The detection of Felis catus papillomavirus 3 DNA in a feline bowenoid in situ carcinoma with novel histologic features and benign clinical behavior

Bowenoid in situ carcinoma (BISC; papillomavirus-associated squamous cell carcinoma in situ) is an uncommon skin neoplasm of cats that can result in euthanasia because of the development of multiple lesions or because of progression to invasive squamous cell carcinoma. BISCs are currently thought to be caused by Felis catus papillomavirus 2 (FcaPV-2). The presently described cat developed a single 0.5 cm in diameter interscapular mass. Over the following 18 months, the mass doubled in size; no additional lesions developed. The mass was surgically excised and histologically diagnosed as a BISC. However, in contrast to previously reported BISCs, neither prominent thickening of the deep aspects of the follicular infundibula nor marked cell dysplasia were present. Furthermore, ~50% of the keratinocytes in the affected epidermis had prominent PV cytopathic changes that included shrunken angular nuclei and elongated basophilic cytoplasmic inclusions. As the histopathology was not typical for FcaPV-2 infection, polymerase chain reaction was performed and revealed only DNA sequences from Felis catus papillomavirus 3 (FcaPV-3). No further BISCs developed in this cat 6 months postremoval, hence surgical excision appeared to be curative. Results from this case suggest that, although FcaPV-2 appears to be the predominant cause of BISCs in cats, infection by FcaPV-3 can also cause these neoplasms. BISCs caused by FcaPV-3 appear to have unique histologic features that allow the causative PV type to be predicted. Results from this single case suggest that BISCs caused by FcaPV-3 may have a more benign clinical course than those caused by FcaPV-2.

Cats, Cancer and Comparative Oncology

Naturally occurring tumors in dogs are well-established models for several human cancers. Domestic cats share many of the benefits of dogs as a model (spontaneous cancers developing in an immunocompetent animal sharing the same environment as humans, shorter lifespan allowing more rapid trial completion and data collection, lack of standard of care for many cancers allowing evaluation of therapies in treatment-naïve populations), but have not been utilized to the same degree in the One Medicine approach to cancer. There are both challenges and opportunities in feline compared to canine models. This review will discuss three specific tumor types where cats may offer insights into human cancers. Feline oral squamous cell carcinoma is common, shares both clinical and molecular features with human head and neck cancer and is an attractive model for evaluating new therapies. Feline mammary tumors are usually malignant and aggressive, with the ‘triple-negative’ phenotype being more common than in humans, offering an enriched population in which to examine potential targets and treatments. Finally, although there is not an exact corollary in humans, feline injection site sarcoma may be a model for inflammation-driven tumorigenesis, offering opportunities for studying variations in individual susceptibility as well as preventative and therapeutic strategies.

Molecular and immunohistochemical studies do not support a role for papillomaviruses in canine oral squamous cell carcinoma development

Oral squamous cell carcinomas (OSCCs) are common neoplasms of dogs and are of unknown cause. Whereas papillomaviruses (PVs) are an established cause of human OSCCs, few studies have investigated canine OSCCs for a PV aetiology. In humans, a PV aetiology can be determined by detecting PV DNA and PV-induced increased p16(CDKN2A) protein (p16) within the OSCC. In this study, PCR, using four different primer sets and p16 immunohistochemistry, was used to evaluate 28 canine OSCCs for a possible PV aetiology. None of the primers amplified PV DNA from any of the OSCCs although four neoplasms contained intense p16 immunostaining. Intense p16 immunostaining would indicate a PV aetiology in a human OSCC but the absence of PV DNA suggests that the increase in p16 was not due to PV infection. Overall the results indicated that PVs are not a significant cause of canine OSCCs.