Novel canine papillomavirus type 18 found in pigmented plaques

Clinical, histopathological, and molecular characterization of canine pigmented viral plaques

Canine pigmented viral plaques (PVPs) are proliferative epidermal lesions caused by canine papillomaviruses (CPVs). Although the lesions are benign, neoplastic transformation has been reported. Cases reported in the literature are few and mainly focused on genome sequencing. The aim of this study was to collect data on the epidemiology, clinicopathological features, and genotyping of PVPs. Fifty-five canine PVPs were retrospectively retrieved and histologically evaluated. Follow-up was available for 33 cases. The median age was 6.5 years and pugs were the most represented breed (25%). There were 4 clinical presentations: a single lesion (24%), multiple lesions (75%) in one (41%) or different sites (34%), and generalized lesions all over the body (24%). The abdomen and axillae were the most common sites. In single lesions, no recurrence was observed after conventional surgery, whereas different medical treatments reported for multiple lesions were not successful. Spontaneous regression was reported in 3 cases. Neoplasia in contiguity with PVPs was seen in 5 of 55 lesions (9%), and 1 dog was euthanized due to invasive squamous cell carcinoma (SCC). The most useful histopathological features for diagnosis were scalloped profile, epidermal spikes, hypergranulosis, and hyperpigmentation. L1 immunolabeling was present in 14 of 16 cases (87%). Sequencing revealed that 10 of 16 cases were associated with CPV-9 (71%), 2 cases were associated with CPV-4 (14%), and 2 cases were associated with CPV-8 (14%). In conclusion, this represents a large cohort study on canine PVPs reporting data on clinicopathological features, therapy, outcome, and the type of CPV involved for the first time in Italy.

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.

Long-Term Culture of Canine Ocular Cells That Maintain Canine Papillomaviruses

Canine ocular papillomas occur on the haired skin of eyelids, conjunctival epithelium, and rarely on the cornea. Using PCR typing assays with canine papillomavirus type-specific primer sets, our study confirmed that the papillomas contained canine papillomavirus type 1. The positive result from a rolling circle amplification assay indicated the CPV1 viral genome in the cells is a circular episomal form. We also successfully established the first canine corneal cell line using the conditional reprogramming method. The cells exhibited an epithelial cell morphology, grew rapidly in vitro, and could be maintained long term. For the continued growth of the canine corneal cells, feeder cells played a more important role than Rho-kinase inhibitor Y-27632. More importantly, the viral CPV1 genome was maintained in the canine corneal cells during the long-term expansion. Unlimited supplies of these cells provide as a model for the study CPV in dog cells, and a platform for drug screening for effective therapies against canine papillomavirus infection in the future.

New insights into Canis familiaris papillomaviruses genetics and biology: Is the genetic characterization of CPV types and their variants an important clinical issue?

Canis familiaris papillomavirus (CPV) is a member of the Papillomaviridae family and is found in dogs. After infection, the host can remain asymtomatic or develop benign ephitelial neoplasms such as papillomas and pigmented viral plaques, which can progress to cancer, in the form of squamous cell carcinoma (SCC). In humans, 227 types of human papillomavirus (HPV) have been described, with a well-established risk classification for cancer development. In addition, it is also known that variants of some high-risk HPV types may present different risks in respect of SCC development. In dogs, however, only a few types of CPV have been identified, despite the growing interest in this area, and knowledge on the genetic characterization of CPV variants is still scarce. Recent studies of CPV have shown that, as with HPV, benign neoplasia can develop into cancer, but it is believed that there are many more types and variants still to be described. Therefore, the aim of this study was to describe the genetics and biology of CPV, with the focus on what is known about lesions, geographic localization, virus types and variants.

Solitary pedunculated multicystic viral plaque associated with canine papillomavirus 18 in a British Bulldog

A pedunculated exophytic mass developed on the rump of a dog. Fine-needle aspiration revealed keratin debris suggestive of a follicular tumor. However, histology revealed a pigmented viral plaque that contained numerous keratin-filled cystic cavities. Canine papillomavirus 18 DNA sequences were detected in the lesion. Viral plaques are typically multiple sessile lesions of dogs. A viral plaque appearing as a solitary exophytic keratin-filled mass has not been reported previously, to our knowledge. The novel clinical findings in this case expand the ways that viral plaques may appear in dogs. In addition, the histologic findings represent a novel pathologic entity of dogs. Given that canine viral plaques can be progressive, and dogs typically develop numerous plaques, it is important to differentiate between a viral plaque and a hair follicle tumor.

Whole Genomic Analysis and Comparison of Two Canine Papillomavirus Type 9 Strains in Malignant and Benign Skin Lesions

Papillomaviruses (PVs) usually cause benign proliferative lesions in the stratified epithelium of various animal species. However, some high-risk types of PVs have been proven to lead to malignant transformations. In dogs, several canine papillomaviruses (CPVs) have been identified in malignant lesions and are suggested as one of the risk factors for the development of squamous cell carcinomas (SCCs). In the present study, the full genomes of two CPV9 strains from recurrent SCCs of Dog 1 and skin viral papilloma (viral plaque) of Dog 2 were sequenced. Alignment of the two CPV9 sequences with the genome of the reference CPV9 strain (accession no. JF800656.1) derived from a solitary pigmented plaque was performed. Compared with the reference strain, a 27 bp in-frame insertion in the E1 gene was identified in both CPV9 strains in this study. In comparison with the CPV9 strains derived from benign lesions, the CPV9 from the SCCs of Dog 1 exhibited a 328 bp deletion at the 3′ end of the E2 and spacer sequence, which encoded a truncated deduced E2 protein and a chimeric E8^E2 protein. However, there was no difference in the mRNA expression levels of viral oncoproteins of E6 and E7 between the two CPV9 cases, suggesting that the oncogenesis of CPV9 for malignant transformation might be different from that of human papillomaviruses. The roles of E2 and E8^E2 deleted CPV9 in the oncogenesis of benign and malignant lesions should be further investigated.

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.

Metagenomics revealing new virus species in farm and pet animals and aquaculture

Viral metagenomics is slowly taking over the traditional and widely used molecular techniques for the investigation of pathogenic viruses responsible for illness and inflicting great economic burden on the farm animal industry. Owing to the continued improvements in sequencing technologies and the dramatic reduction of per base costs of sequencing the use of next generation sequencing have been key factors in this progress. Discoveries linked to viral metagenomics are expected to be beneficial to the field of veterinary medicine starting from the development of better diagnostic assays to the design of new subunit vaccines with minimal investments. With these achievements the research has taken a giant leap even toward the better healthcare of animals and, as a result, the animal sector could be growing at an unprecedented pace.

Pigmented viral plaque and basal cell tumor associated with canine papillomavirus infection in Pug dogs

Pigmented viral plaque is most commonly seen in Pug dogs in association with canine papillomavirus (CPV). In the present study, nucleic acid sequence and localization of viral genes were examined in 4 cases of pigmented viral plaque in Pug dogs. The results of polymerase chain reaction and nucleic acid sequence analysis showed that the 3 cases with pigmented viral plaque were infected with CPV4, and 1 case with CPV18. In the case with CPV18-positive viral plaque, CPV18 gene was also detected in a lesion of cytokeratin-14- and P63-positive basal cell tumor that developed adjacent to a pigmented viral plaque. Moreover, CPV gene was detected in the squamous cells of pigmented viral plaques and the neoplastic cells of basal cell tumor by in situ hybridization. This is the first report of basal cell tumor associated with CPV18-infection in the dog. Infection of CPV18 may be associated with development of basal cell tumor.

Malignant Transformation of a Canine Papillomavirus Type 1-Induced Persistent Oral Papilloma in a 3-Year-Old Dog

This case report describes a rare case of a persistent canine papillomavirus type 1 (CPV-1)-induced oral papilloma that underwent malignant transformation into an oral squamous cell carcinoma (OSCC) in a 3-year-old Labrador retriever cross. Initially, the patient had multiple and multifocal verrucous lesions populating the oral cavity exclusively. The papillomas persisted despite multiple surgical ablations, azithromycin, interferon α-2b, alternative medicines, and off-label drug use of an immunostimulant. After 1 year and 6 months, an aggressive lesion developed at the level of the left mandibular first molar (309) and progressed to a well-differentiated invasive OSCC. The presence of CPV-1 DNA in the OSCC, and the known oncogenic abilities of CPV-1, suggests that this virus might have played a significant role in the emergence of the OSCC that ultimately led to the patient's euthanasia due to poor quality of life. This is the first well-documented case where OSCC has developed from an oral papilloma caused by CPV-1 in which the presence of coinfection by another papillomavirus was excluded by multiple polymerase chain reaction tests using various primers.

Molecular characterization of Canis familiaris oral papillomavirus 1 identified in naturally infected dogs from Northeast Brazil

BACKGROUND

Canine papillomavirus (CPV) has 20 described types associated with papillomas or squamous cell carcinoma (SCC). Knowledge about CPV diversity is scarce. Studies on papillomaviruses that infect other hosts show substantial diversity with some types and variants being associated with cancer.

HYPOTHESIS/OBJECTIVES

The aim of this study was to assess the genetic variability of the capsid L1 gene of CPV identified in lesions of naturally infected dogs from Brazil.

ANIMALS

Six dogs presenting with oral and cutaneous warts from different veterinary clinics in Sergipe state, Northeast Brazil.

METHODS AND MATERIALS

Nine skin biopsy samples were collected for histopathological and molecular analyses. Bioinformatics tools were used for genotyping and diversity analysis. Mutations were characterized based on their impact on the L1 protein structure.

RESULTS

Sequences of CPV1 were obtained from exophytic papillomas. These sequences had at least five different mutations showing that all sequences were putative CPV1 variants. One CPV1 sequence, obtained from an oral SCC, had a highly destabilizing substitution in the L1 protein which was likely to be associated with changes in protein function.

CONCLUSIONS AND CLINICAL IMPORTANCE

Despite the small number of cases analysed and the partial analysis of L1 nucleotide and amino acid sequences, this study has demonstrated diversity in CPV samples from Northeast Brazil. A putative new CPV1 variant associated with oral SCC, with novel protein structure changing mutations, was identified which may be important for understanding papillomavirus pathogenesis.

Canine papillomavirus types 1 and 2 in classical papillomas: High abundance, different morphological associations and frequent co-infections

Canine papillomatosis is mainly attributed to papillomavirus infections. Papillomavirus DNA is also frequently identified in healthy skin, and evidence of high papillomavirus diversity complicates this simplistic view of causality. The aim of this study was to determine how frequently canine papillomas contain papillomavirus DNA and express viral protein, and how these factors correlate to the histology and anatomic location. Fifty-three archived, formalin-fixed samples of canine papillomas and eight samples of other proliferative skin lesions from dogs were included. Samples were re-evaluated histologically, tested for papillomavirus L1-antigen using immunohistochemistry, and for papillomavirus DNA with PCR assays and molecular sequencing. Most papillomas from haired skin contained papillomavirus DNA (96%) and antigen (92%). Of oral papillomas, 88% were positive for both papillomavirus DNA and antigen. Approximately 50% of non-papilloma proliferations and papillomas from eyelid/conjunctiva specimens contained viral DNA, but antigen was present in only 12% of eyelid/conjunctiva papillomas and in none of the non-papilloma proliferations. The presence of viral antigen was highly correlated with histological indicators of viral infection, including intranuclear inclusions, koilocytes, cytoplasmatic vacuolation and dysplasia. The viruses found were mainly CPV1 and CPV2. CPV1 dominated in oral infections, while CPV2 dominated in cutaneous endophytic papillomas. Co-infections with CPV1 and CPV2 accounted for about 20% of all detected infections. These results support a role for papillomaviruses in canine cutaneous and oral, exophytic and endophytic papillomas and support previously raised doubts about their role in squamous papillomas from eyelid/conjunctiva specimens.

Viral genome integration of canine papillomavirus 16

Papillomaviruses infect humans and animals, most often causing benign proliferations on skin or mucosal surfaces. Rarely, these infections persist and progress to cancer. In humans, this transformation most often occurs with high-risk papillomaviruses, where viral integration is a critical event in carcinogenesis. The first aim of this study was to sequence the viral genome of canine papillomavirus (CPV) 16 from a pigmented viral plaque that progressed to metastatic squamous cell carcinoma in a dog. The second aim was to characterize multiple viral genomic deletions and translocations as well as host integration sites. The full viral genome was identified using a combination of PCR and high throughput sequencing. CPV16 is most closely related to chipapillomaviruses CPV4, CPV9, and CPV12 and we propose CPV16 be classified as a chipapillomavirus. Assembly of the full viral genome enabled identification of deletion of portions of the E1 and E2/E4 genes and two viral translocations within the squamous cell carcinoma. Genome walking was performed which identified four sites of viral integration into the host genome. This is the first description of integration of a canine papillomavirus into the host genome, raising the possibility that CPV16 may be a potential canine high-risk papillomavirus type.

Nasal virome of dogs with respiratory infection signs include novel taupapillomaviruses

Using viral metagenomics, we characterized the mammalian virome of nasal swabs from 57 dogs with unexplained signs of respiratory infection showing mostly negative results using the IDEXX Canine Respiratory Disease RealPCR™ Panel. We identified canine parainfluenza virus 5, canine respiratory coronavirus, carnivore bocaparvovirus 3, canine circovirus and canine papillomavirus 9. Novel canine taupapillomaviruses (CPV21-23) were also identified in 3 dogs and their complete genome sequenced showing L1 nucleotide identity ranging from 68.4 to 70.3% to their closest taupapillomavirus relative. Taupapillomavirus were the only mammalian viral nucleic acids detected in two affected dogs, while a third dog was coinfected with low levels of canine parainfluenza 5. A role for these taupapillomavirues in canine respiratory disease remains to be determined.

Malignant transformation of canine oral papillomavirus (CPV1)-associated papillomas in dogs: An emerging concern?

Canine oral papillomavirus (CPV1, also known as COPV), the most common cause of non-neoplastic papillomas, has not been shown to cause squamous cell carcinomas (SCC). Furthermore, malignant transformation of benign papillomas to SCC has only been reported in a single group of dogs with severe combined immunodeficiency infected with CPV2. Here, we report a series of 7 dogs with benign CPV1-associated papillomas with histologic evidence of CPV1 causing malignant transformation to carcinoma in situ and ultimately SCC. Expression of p53 and p16 proteins in CPV1-infected cells within the benign papillomas and lesions that progressed into SCC also supported an association between papillomavirus and malignant transformation. Moreover, our retrospective analysis indicated that while there have been increased numbers of viral papillomas with malignant transformation, the number of annually diagnosed canine viral papillomas has remained constant over the past decade in our laboratory. We speculate that either an altered host immunity from increased usage of immunosuppressive drugs or changing environmental factors, e.g. increase exposure to UV radiation, may cause an increased oncogenic potential of this “low-risk” virus. This study aims to raise awareness of the malignant potential of CPV1 and to encourage further investigations into the cause of this suspected change in its oncogenic potential.