Multiple oral carcinomas associated with a novel papillomavirus in a dog

Canine oral squamous cell carcinoma as a spontaneous, translational model for radiation and immunology research

Introduction

Improving outcomes for oral squamous cell carcinoma (OSCC) patients has been hindered by a lack of effective predictive animal models. Spontaneously occurring canine OSCC could help fill this gap. The objective of this study was to characterize the immune landscape of canine OSCC to advance understanding of how dogs could serve as a surrogate for human OSCC.

Methods/Results

Canine OSCC contains a heterogenous tumor immune microenvironment. CD3+ T cells were the predominant tumor infiltrating immune cell population; however, there was a wide range CD3+ T cell density across samples. The most common CD3+ T cell micro-anatomical distribution was defined as "pre-existing immunity", but the remaining 20% of tumors were characterized as "immunologically ignorant" or "excluded infiltrates" patterns. When compared to normal oral mucosa, the tumor gene expression pattern suggests that canine OSCC microenvironment is highly inflamed and characterized by the presence of an anti-tumor immune response dominated by cytotoxic\effector T cells and NK cells (CD8a, GZMA, OX40, and HLA-A); however, overexpression of genes associated with effector T cell exhaustion and microenvironmental immunosuppression was also identified (PD-1, LAG3, CXCL2). Correlations between CD3+ T cell density and immune gene expression revealed key genes associated with cytotoxic anti-tumor T cell responses (GZMA, GZMB, PRF1), co-stimulation of T cells (CD27, CD28, ICOS), and other immune processes, including Type I IFN response (TNF, TNFSF10), and T cell exhaustion (CTLA4, PD-1). CD3+ T cell density in canine OSCC was significantly correlated with a cytolytic activity score (mean PRF1 and GZMA expression), suggestive of active effector CD8 T cell function. CD204+ macrophages were the second most abundant tumor infiltrating immune cell, and when comparing to normal oral mucosa, two differently expressed genes linked to tumor associated macrophages and myeloid derived suppressor cells (MDSC) were identified: CXCL2, CD70. Overexpression of CXCL2 was also identified in canine OSCC "T cell-high" tumors compared to "T cell-low" tumors.

Discussion

This study identified actionable immunotherapy targets which could inform future comparative oncology trials in canine OSCC: CTLA-4, PD-1, CXCL2. These data provide a good first step towards utilizing spontaneous canine OSCC as a comparative model for human OSCC radiation and immuno-oncology research.

Papillomaviral skin diseases of humans, dogs, cats and horses: A comparative review. Part 2: Pre-neoplastic and neoplastic diseases

Papillomaviruses (PVs) are well recognized to cause pre-neoplastic and neoplastic diseases in humans. Similarly, there is increasing evidence that PVs play a significant role in the development of pre-neoplastic and neoplastic diseases of the haired skin of dogs and cats, and the mucosa of horses. As the mechanisms by which PVs cause neoplasia are well studied in humans, it is valuable to compare the PV-induced neoplasms of humans with similar PV-associated neoplasms in the companion animal species. In the second part of this comparative review, the pre-neoplastic and neoplastic diseases thought to be caused by PVs in humans, dogs, cats, and horses are described. This includes PV-induced cutaneous plaques, cutaneous squamous cell carcinomas (SCCs) and mucosal SCCs within the four species. The review concludes with a discussion about the potential use of vaccines to prevent PV-induced diseases of dogs, cats, and horses.

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.

Alimentary squamous cell carcinoma in psittacines: 12 cases and review of the literature

Squamous cell carcinoma (SCC), which is a neoplasm that usually arises from the integument, is reported uncommonly in pet birds. Only a few reports of SCCs in the alimentary tract of birds, including psittacines, have been published, and a detailed description of the pathology is not available in the literature. We present here 12 cases of alimentary SCC in psittacines. The average age of the birds was 22.2 y (range: 15-29 y), and affected species included 4 Amazon parrots (Amazona sp.), 3 cockatiels (Nymphicus hollandicus), 3 macaws (Ara sp.), 1 conure (Eupsittula sp.), and 1 Senegal parrot (Poicephalus sp.). Frequent clinical complaints included regurgitation, dysphagia, dyspnea, lethargy, and/or weight loss. SCC primarily affected the oral cavity in 6 of 12 cases, the crop alone in 2 of 12 cases, the crop and esophagus in 1 of 12 cases, the proventriculus alone in 1 of 12 cases, and the crop, esophagus, and proventriculus in 2 of 12 cases. Histologically, alimentary SCCs were locally invasive and often resulted in mucosal ulceration. Although there were no metastases in any of our cases, poor clinical outcomes were frequent and associated most commonly with complete effacement of the alimentary segment and severe inflammation with opportunistic bacterial infection. Our review of the literature records commonly affected species, variability of gross presentations and clinical signs, plausible etiologies, and current diagnostic developments.

A First NGS Investigation Suggests No Association Between Viruses and Canine Cancers

Approximately 10–15% of worldwide human cancers are attributable to viral infection. When operating as carcinogenic elements, viruses may act with various mechanisms, but the most important is represented by viral integration into the host genome, causing chromosome instability, genomic mutations, and aberrations. In canine species, few reports have described an association between viral integration and canine cancers, but more comprehensive studies are needed. The advancement of next-generation sequencing and the cost reduction have resulted in a progressive increasing of sequencing data in veterinary oncology offering an opportunity to study virome in canine cancers. In this study, we have performed viral detection and integration analyses using VirusFinder2 software tool on available whole-genome and whole-exome sequencing data of different canine cancers. Several viral sequences were detected in lymphomas, hemangiosarcomas, melanomas, and osteosarcomas, but no reliable integration sites were identified. Even if with some limitations such as the depth and type of sequencing, a restricted number of available nonhuman genomes software, and a limited knowledge on endogenous retroviruses in the canine genome, results are compelling. However, further experiments are needed, and similarly to feline species, dedicated analysis tools for the identification of viral integration sites in canine cancers are required.

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.

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.

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.

Immunostaining for p53 and p16CDKN2A Protein Is Not Predictive of Prognosis for Dogs with Malignant Mammary Gland Neoplasms

Mammary gland tumors (MGTs) are common in dogs and show a variable clinical behavior that is difficult to predict. Currently, few immunohistochemical markers have been established to predict the prognosis of a canine MGT. However, p53 immunostaining has been variably reported to be prognostic for canine MGTs. Additionally, while p16^CDK2NA protein (p16) immunostaining has been found to be prognostic for human breast cancers, this marker has never been evaluated as a prognostic marker for canine neoplasms. In the present study, the prognostic utility of p53 and p16 was evaluated in 35 canine malignant MGTs. It was observed that 19 (54%) dogs died due to their MGTs with an overall mean survival time (MST) of 882 days. Seven MGTs showed p53 immunostaining, but this was not significantly associated with death (4 of 7 vs. 15 of 28; p = 0.6) or MST (670 vs. 934 days; p = 0.57). Five dogs had MGTs with no p16 immunostaining, 28 MGTs had intermediate p16 immunostaining, and two MGTs had increased p16 immunostaining. Neither death due to MGT (4 of 5, 14 of 28, or 1 of 2; p = 0.28) nor MST (683, 927, and 307 days; p = 0.31) were significantly associated with p16 immunostaining. Interestingly, p53 immunostaining was significantly associated with an increase or loss of p16 immunostaining. This is the first time that p16 has been evaluated as a prognostic marker for canine neoplasms. While these results suggest that a proportion of canine MGTs develop by cellular mechanisms that alter both p53 and p16 expression, there was no evidence that defects in p53 or p16 alter the behavior of a MGT. Neither p53 nor p16 was found to significantly predict prognosis, although this could reflect the limited number of MGTs included in the study.

Alpha, Beta, gamma human PapillomaViruses (HPV) detection with a different sets of primers in oropharyngeal swabs, anal and cervical samples

Background

Recent studies have shown a 13-fold increase of oropharyngeal cancer in the presence of HPV, while α-HPV detection seems to be rare in oral cavity in comparison to anal or cervical district, many novel β and γ types have been isolated in this anatomical site suggesting a wide tropism range. Currently, there are no guidelines recommending HPV oral cavity screening as a mandatory test, and it remains unknown which HPV types should be included in HPV screening programs. Our goal was to assess HPV prevalence in oropharyngeal, anal, and cervical swabs using different sets of primers,which are able to amplify α, β, γ HPV types.

Methods

We analysed the presence of HPV DNA in oropharyngeal (n = 124), anal (n = 186), cervical specimens (n = 43) from HIV positive and negative patients using FAP59/64 and MY09/11 primers. All untyped strains were genetically characterized through PCR amplification and direct sequencing of partial L1 region, and the resulting sequences were classified through phylogenetic analysis.

Results

HPV prevalence was 20.9% in 124 oropharyngeal swab samples, including infections with multiple HPV types (5.6%). HPV prevalence in this anatomical site was significantly associated with serostatus: 63.3%in HIV positive and 36.3% in HIV negative patients (p < 0.05).

Unclassified types were detected in 6 specimens. In our analysis, we did not observe any difference in HPV (α, β, γ) prevalence between men and women. Overall, β species were the most frequently detected 69.7%. When using anal swabs, for HIV positive patients, β genus prevalence was 1% and γ genus was 3.7% including 6 unclassified types. In cervical samples from 43 HIV positive women (18 HPV negative and 25 positive by MY09/11 PCR), only one sample was positivite for β₁ species (2.4%) using FAP primers. Six of the untyped strains clustered with sequences from species 7, 9, 10, 8,12 of γ genus. Four sequences remained unclassified. Finally, β and γ HPV prevalence was significantly lower than their respective HPV prevalence as identified by the Luminex system in all anatomical sites that were analyzed in previous studies.

Conclusion

This study provides new information about viral isolates present in oropharyngeal site and it will contribute to improve the monitoring of HPV infection.

Electronic supplementary material

The online version of this article (10.1186/s12985-019-1132-x) contains supplementary material, which is available to authorized users.

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.

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.

Immunohistochemical Characterization of Canine Oral Papillary Squamous Cell Carcinoma

Recently, histologic subtypes of oral squamous cell carcinoma (SCC) corresponding to the human classification scheme have been proposed for dogs. A papillary squamous cell carcinoma subtype is characterized by dominant exophytic architectural growth with limited invasion, a lower metastatic rate, and better overall survival compared with conventional SCC. Whereas most canine oral conventional SCCs are easily diagnosed by histologic examination, the diagnosis of canine oral papillary squamous cell carcinoma (COPSCC) can be challenging since the exophytic portion lacks histologic features of malignancy and appears similar to oral nonviral papillomas. In contrast, the invasive portion of COPSCC has morphologic similarities to conventional SCC and canine acanthomatous ameloblastoma. The goals of this study were to immunophenotype these 3 entities and to potentially identify discriminating markers. A panel of 17 immunohistochemical markers was investigated in tissue microarrays that included 25 COPSCCs, 10 conventional SCCs, and 10 canine acanthomatous ameloblastomas. Additionally, COPSCCs were screened for papillomavirus as a potential cause using immunohistochemistry and in situ hybridization. COPSCC had immunophenotypical similarities with conventional SCC and acanthomatous ameloblastoma, but the combined differences in immunolabeling for AE1/AE3, 34βE12, p63, and calretinin discriminated between the entities. Papillomavirus was not detected in any COPSCC, making a viral pathogenesis unlikely. A better understanding of the immunophenotype of COPSCC will aid in a more accurate diagnosis and potentially improve therapeutic approaches.

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.

Complete Genome Sequences of Two Isolates of Canis familiaris Oral Papillomavirus from South Africa

Canis familiaris oral papillomavirus, formerly canine oral papillomavirus, is a causative agent of the self-resolving canine oral papillomatosis and was first described in 1994. This is the first report of two full-length genome sequences described in South Africa and indicates the highly conserved nature of Canis familiaris oral papillomavirus.

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.

p16 Immunostaining of Canine Squamous Cell Carcinomas Is Not Associated with Papillomaviral DNA

While papillomavirus (PVs) are an established cause of human cancer, few reports have supported a relationship between PV and canine squamous cell carcinomas (SCCs). Human oncogenic PVs lead to an increased expression of the p16 tumor suppressor protein, and the latter can be demonstrated immunohistochemically to support a likely causal relationship between tumor and PV infection. In the present study, archive samples of canine SCC from different anatomical locations were tested by polymerase chain reaction for the presence of PV DNA and by p16 immunohistochemistry. The aims were to investigate the relationship between p16 expression and presence of PV DNA, in order to assess the utility of p16 overexpression as a biomarker of PV infection in canine SCC. A total of 52 SCCs were included. Nine cases (17.3%) showed moderate p16 immunoreactivity, with no association with tumor degree of differentiation, histotype or mitotic activity. The canPVf/FAP64 primers amplified Canis familiaris PV-1 DNA from 3 out of 52 tumors (5.8%), one cutaneous, one oral and one tonsillar SCC. There was no association between PV presence and p16 immunostaining. These results do not support a significant role of PVs in the development of canine SCCs. Additionally, PV infection was apparently not the cause of the p16 immunostaining observed in a subset of canine SCCs. A better awareness of p16 level of expression and cellular function in canine cancer may help to define its diagnostic and prognostic role.

Collision Tumour of Squamous Cell Carcinoma and Malignant Melanoma in the Oral Cavity of a Dog

A 7-year-old, male cocker spaniel was presented with a gingival proliferative lesion in the rostral maxilla and enlargement of the regional lymph node. Morphological and immunohistochemical analysis revealed a collision tumour composed of two malignant populations, epithelial and melanocytic, with metastasis of the neoplastic melanocytes to the regional lymph node. The epithelial component consisted of trabeculae and islands of well-differentiated squamous epithelium immunoreactive to cytokeratins. The melanocytic component had a varying degree of pigmentation of polygonal and spindle-shaped cells, growing in nests or densely packed aggregates and immunolabelled with S100, melanoma-associated antigen (melan A), neuron-specific enolase and vimentin antibodies. Protein markers involved in tumorigenesis or cell proliferation (i.e. COX-2, p53, c-kit and Ki67), were overexpressed by the neoplastic cells. To the authors' knowledge, this is the first description of an oral collision tumour involving malignant melanoma and squamous cell carcinoma in the dog.

Animal models of head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is the most common oral cancer worldwide. Local bone invasion into the maxilla or mandible and metastasis to regional lymph nodes often result in a poor prognosis, decreased quality of life and shortened survival time for HNSCC patients. Poor response to treatment and clinical outcomes are the major concerns in this aggressive cancer. Multiple animal models have been developed to replicate spontaneous HNSCC and investigate genetic alterations and novel therapeutic targets. This review provides an overview of HNSCC as well as the traditional animal models used in HNSCC preclinical research. The value and challenges of each in vivo model are discussed. Similarity between HNSCC in humans and cats and the possibility of using spontaneous feline oral squamous cell carcinoma (FOSCC) as a model for HNSCC in translational research are highlighted.

Genomic characterisation of canine papillomavirus type 17, a possible rare cause of canine oral squamous cell carcinoma

Squamous cell carcinomas (SCCs) are the second most common cancer of the canine oral cavity resulting in significant morbidity and mortality. Recently a dog with multiple oral SCCs that contained a novel papillomavirus (PV) was reported. The aim of the present study was to determine the genome of this novel PV. To do this a short section of PV DNA was amplified from an oral SCC and 'back-to-back' primers were designed. Due to the circular nature of PV DNA, these primers were then used to amplify the remainder of the genome by inverse PCR. The PCR product was sequenced using next generation sequencing and the full genome of the PV, consisting of 8007 bp, was assembled and analysed. As this is the seventeenth PV identified from the domestic dog, the novel PV was designated Canis familiaris papillomavirus (CPV) type 17. Similar to other CPV types, the putative coding regions of CPV-17 were predicted to produce 5 early and 2 late proteins. Phylogenetic analysis of ORF L1 revealed greater than 70% similarity to CPV-2 and CPV-7 and we propose that CPV-17 also be classified as a Taupapillomavirus 1. While it appears CPV-17 is only rarely present in canine oral SCCs, evidence suggests that this PV could influence the development of oral SCCs in this species.

Molecular methods for identification and characterization of novel papillomaviruses

Papillomaviruses (PV) are a remarkably heterogeneous family of small DNA viruses that infect a wide variety of vertebrate species and are aetiologically linked with the development of various neoplastic changes of the skin and mucosal epithelia. Based on nucleotide similarity, PVs are hierarchically classified into genera, species and types. Novel human PV (HPV) types are given a unique number only after the whole genome has been cloned and deposited with the International HPV Reference Center. As of 9 March 2015, 200 different HPV types, belonging to 49 species, had been recognized by the International HPV Reference Center. In addition, 131 animal PV types identified from 66 different animal species exist. Recent advances in molecular techniques have resulted in an explosive increase in the identification of novel HPV types and novel subgenomic HPV sequences in the last few years. Among PV genera, the γ-PV genus has been growing most rapidly in recent years with 80 completely sequenced HPV types, followed by α-PV and β-PV genera that have 65 and 51 recognized HPV types, respectively. We reviewed in detail the contemporary molecular methods most often used for identification and characterization of novel PV types, including PCR, rolling circle amplification and next-generation sequencing. Furthermore, we present a short overview of 12 and 10 novel HPV types recently identified in Sweden and Slovenia, respectively. Finally, an update on the International Human Papillomavirus Reference Center is provided.

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.