Equus caballus papillomavirus Type 7 is a rare cause of equine penile squamous cell carcinomas

Penile squamous cell carcinomas (SCCs) are common, potentially life-threatening neoplasms of horses. They are well-recognized to be caused by Equus caballus papillomavirus (EcPV) type 2, although EcPV2 cannot be detected in all cases. A 23-year-old standardbred gelding developed multiple penile in situ and invasive SCCs that contained histological evidence of PV infection. By using both consensus and specific PCR primers, these lesions were found to contain EcPV7 DNA, but not DNA from EcPV2 or any other PV type. To determine how frequently EcPV7 is present in equine penile SCCs, specific primers were used to detect EcPV2 and EcPV7 in a series of 20 archived samples. EcPV7 was the only PV detected in one, both EcPV2 and 7 were detected in five, and only EcPV2 was detected in 14 SCCs. EcPV7 DNA was also detected in three of 10 archived oropharyngeal SCCs, although only as a co- infection with EcPV2. This is the first report of EcPV7 causing disease in horses. These results suggest EcPV7 could cause a subset of equine penile SCCs, and this is the first evidence that PV types other than EcPV2 can cause these neoplasms. The detection of EcPV7 in the oropharyngeal SCCs suggests a potential role of this PV type in the development of these SCCs. There were no clinical or histological features that differentiated lesions containing EcPV7 DNA from those containing EcPV2 DNA. If EcPV7 causes a proportion of equine penile SCCs, vaccines to prevent EcPV2 infection may not prevent all equine penile SCCs.

Abortion storm of Yili horses is associated with Equus caballus papillomavirus 2 variant infection

Nine different species of Equus caballus papillomavirus (EcPV) and three bovine papillomaviruses (BPVs) have been reported to infect horses. However, there are few descriptions of such infections in China. In our pioneer study on Chinese horses, we identified EcPV-2 in the nasal swabs (4/230, 1.7%) of Yili horses, and the semen (3/18, 16.7%) of thoroughbred horses. This indicated that EcPV is indeed hosted by horses in China, and that EcPV-2 might be transmitted though breeding. Further detection of EcPVs in the lung tissues of aborted fetuses of Yili horses, which were originally negative for equid herpes viruses, demonstrated EcPV-2 positivity in 19 of 50 samples, thereby indicating that EcPV-2 may be a new pathogen responsible for causing abortion. Thereafter, sequence analyses of the L1 genes of 26 EcPV-2 in China were performed, indicating that EcPV-2, which primarily infects horses in China, shared 98.3-99.9% nt identity with the published sequences for EcPV-2. These observations indicated that EcPV-2 identified in the current study were highly similar variants of the previously identified strains of EcPV-2. Phylogenetic analysis based on L1 gene sequences from GenBank showed that the EcPV-2 found in Chinese horses was closely related to and clustered together with an already known EcPV-2a lineage. Our study provides the first evidence related to EcPV-2 infection in Chinese horses, which can serve as a causative agent for Yili horse abortions, and may thus lay the foundation for a systematic and detailed epidemiological study of this infection in Chinese horses.

Detection of Equus caballus Papillomavirus in Equine Aural Plaque Samples

Aural plaques have been linked to Equus caballus papillomavirus (EcPV). Ten types of EcPVs have already been described; however, only EcPVs 1, 3, 4, 5, and 6 have been observed in association with aural plaques. Accordingly, the objective of this study was to evaluate the presence of EcPVs in equine aural plaque samples. A total of 29 aural plaque samples (from 15 horses) were collected and assessed for the presence of the DNA of these EcPVs by PCR. Additionally, 108 aural plaque samples used in previous research were evaluated for the presence of EcPVs 8 and 9. Previously described primers were used for PCR to detect EcPVs 1 to 8, and specific primers were designed for EcPV 9. Minigenes were synthesized and used as a positive control in the PCRs for the undetected EcPVs. EcPVs 2, 7, 8, and 9 were not detected in any of the evaluated samples, suggesting that these viral types are not involved in the etiology of the equine aural plaque in Brazil. EcPV 6 was the most prevalent (81%), followed by EcPVs 3 (72%), 4 (63%) and 5 (47%), which reinforces the idea that these viruses play an important role in the etiology of the equine aural plaque in Brazil.

Cutaneous plaques associated with a putative novel papillomavirus type in a horse

CASE HISTORY AND CLINICAL FINDINGS

A 6-year-old Thoroughbred mare developed multiple flat plaques, < 1 cm in diameter, on the left front fetlock. These were treated topically using 5-fluorouracil and resolved after 4 weeks. However, additional similar plaques developed on the left front pastern 5 months later. These lesions resolved within 3 months without treatment.

PATHOLOGICAL AND MOLECULAR FINDINGS

One plaque that developed initially and one plaque that developed later were examined histologically. Both consisted of well-demarcated foci of moderate epidermal hyperplasia. Scattered throughout both plaques were cells showing evidence of papillomavirus-induced cell changes and the same papillomaviral DNA sequence was amplified from both lesions using PCR. As the novel sequence had 79.1% similarity to a partial sequence previously amplified from an equine cutaneous wart and 67.9% similarity to Equus caballus papillomavirus type 1, these results indicate detection of a putative novel papillomavirus type.

DIAGNOSIS

Multiple cutaneous plaques due to infection by a novel papillomavirus type.

CLINICAL RELEVANCE

Unlike more typical equine cutaneous warts which generally appear as pedunculated and filiform masses, the lesions in this horse appeared as raised plaques. With the exception of aural plaques that are confined to the ears, localised clusters of papillomaviral plaques have not been previously described in horses. The lesions contained subtle histological evidence of papillomavirus infection and careful examination is required to differentiate these plaques from pre-neoplastic lesions. The plaques contained a putative novel papillomavirus type. These results increase the spectrum of papillomavirus-induced skin disease in horses.

Genetic Characterization of a Novel Equus caballus Papillomavirus Isolated from a Thoroughbred Mare

Papillomaviruses (PVs) are small, non-enveloped viruses, ubiquitous across the animal kingdom. PVs induce diverse forms of infection, such as cutaneous papillomas, genital papillomatosis, and carcinomas. During a survey on the fertility status of a mare, a novel Equus caballus PV (EcPV) has been identified using Next Generation Sequencing, and it was further confirmed with genome-walking PCR and Sanger sequencing. The complete circular genome 7607 bp long shares 67% average percentage of identity with EcPV9, EcPV2, EcPV1, and EcPV6, justifying a new classification as Equus caballus PV 10 (EcPV10). All EcPV genes are conserved in EcPV10, and phylogenetic analysis indicates that EcPV10 is closely related to EcPV9 and EcPV2, genus Dyoiota 1. A preliminary EcPV10 genoprevalence study, carried out on 216 horses using Real Time PCRs, suggested a low incidence of this isolate (3.7%) compared to EcPVs of the same genus such as EcPV2 and EcPV9 in the same horse population. We hypothesize a transmission mechanism different from the one observed in the closely related EcPV9 and EcPV2 that particularly infect Thoroughbreds. This horse breed is usually submitted to natural mating, thus indicating a possible sexual diffusion. No differences were detected for breeds in terms of susceptibility to EcPV10. Further studies are needed to investigate the molecular mechanisms behind the host and EcPV10 infection to explain the reduced viral spread.

Detection of Equine Papillomaviruses and Gamma-Herpesviruses in Equine Squamous Cell Carcinoma

Squamous cell carcinoma (SCC) seriously compromises the health and welfare of affected horses. Although robust evidence points to equine papillomavirus type 2 (EcPV2) causing genital lesions, the etiopathogenesis of equine SCC is still poorly understood. We screened a series of SCCs from the head-and-neck (HN), (peri-)ocular and genital region, and site-matched controls for the presence of EcPV2-5 and herpesvirus DNA using type-specific EcPV PCR, and consensus nested herpesvirus PCR followed by sequencing. EcPV2 DNA was detected in 45.5% of HN lesions, 8.3% of (peri-)ocular SCCs, and 100% of genital tumors, whilst control samples from tumor-free horses except one tested EcPV-negative. Two HNSCCs harbored EcPV5, and an ocular lesion EcPV4 DNA. Herpesvirus DNA was detected in 63.6%, 66.6%, 47.2%, and 14.2% of horses with HN, ocular, penile, and vulvar SCCs, respectively, and mainly identified as equine herpesvirus 2 (EHV2), 5 (EHV5) or asinine herpesvirus 5 (AsHV5) DNA. In the tumor-free control group, 9.6% of oral secretions, 46.6% of ocular swabs, 47% of penile samples, and 14.2% of vaginal swabs scored positive for these herpesvirus types. This work further highlights the role of EcPV2 as an oncovirus and is the first to provide information on the prevalence of (gamma-)herpesviruses in equine SCCs.

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.

Equus caballus Papillomavirus Type-9 (EcPV9): First Detection in Asymptomatic Italian Horses

Papillomavirus (PV) infections may be related to anogenital lesions and cancer development in humans and several other animal species. To date, 11 different PVs have been reported in horses. Among them, a newly described PV named Equus caballus Papillomavirus Type9 (EcPV9) was thus far only reported in the semen of a stallion with penile lesions in Australia. This study reports for the first time the presence of EcPV9 in asymptomatic Italian horses. From July 2020 to January 2022, genital brush samples were collected from 209 horses with no apparent signs of neoplastic disease and no PV-associated lesions, clinically examined at the Didactic Veterinary University Hospital (OVUD) of Perugia and at the Veterinary University Hospital (OVU) of Turin. Brushes were submitted to real-time PCR targeting the EcPV9-L1 region. The first amplification targeted a region of ~116 bp, followed by the amplification and sequencing of ~533 bp of the positive samples. EcPV9-L1 DNA was found in eleven horses (5.3%), all female and mainly English Thoroughbred. Co-infection with EcPV2-L1 was found in 7 out of the 11 EcPV9-L1 positive horses (63.6%). This study contributes to the description of the prevalence of exposure or infection of EcPVs in the horse population in Italy, for which data are still limited. In this regard, here we provide a phylogenetic analysis and the completely reconstructed viral genomes of two Italian EcPV type 9 isolates, as well as four EcPV type 2 obtained from co-infected animals.

Tumor Cell Plasticity in Equine Papillomavirus-Positive Versus-Negative Squamous Cell Carcinoma of the Head and Neck

Squamous cell carcinoma of the head and neck (HNSCC) is a common malignant tumor in humans and animals. In humans, papillomavirus (PV)-induced HNSCCs have a better prognosis than papillomavirus-unrelated HNSCCs. The ability of tumor cells to switch from epithelial to mesenchymal, endothelial, or therapy-resistant stem-cell-like phenotypes promotes disease progression and metastasis. In equine HNSCC, PV-association and tumor cell phenotype switching are poorly understood. We screened 49 equine HNSCCs for equine PV (EcPV) type 2, 3 and 5 infection. Subsequently, PV-positive versus -negative lesions were analyzed for expression of selected epithelial (keratins, β-catenin), mesenchymal (vimentin), endothelial (COX-2), and stem-cell markers (CD271, CD44) by immunohistochemistry (IHC) and immunofluorescence (IF; keratins/vimentin, CD44/CD271 double-staining) to address tumor cell plasticity in relation to PV infection. Only EcPV2 PCR scored positive for 11/49 equine HNSCCs. IHC and IF from 11 EcPV2-positive and 11 EcPV2-negative tumors revealed epithelial-to-mesenchymal transition events, with vimentin-positive cells ranging between <10 and >50%. CD44- and CD271-staining disclosed the intralesional presence of infiltrative tumor cell fronts and double-positive tumor cell subsets independently of the PV infection status. Our findings are indicative of (partial) epithelial–mesenchymal transition events giving rise to hybrid epithelial/mesenchymal and stem-cell-like tumor cell phenotypes in equine HNSCCs and suggest CD44 and CD271 as potential malignancy markers that merit to be further explored in the horse.

Vulvar squamous cell carcinoma associated with Equus caballus papillomavirus type 2 infection in a Japanese mare

Equus caballus papillomavirus type 2 (EcPV2) infection has been associated with genital squamous cell carcinoma (SCC) development in horses. However, very few reports on EcPV2-associated disease in Asia exist. Our study characterizes pathological and virological features of an EcPV2-associated vulvar SCC from a Japanese mare. Conventional PCR, in situ hybridization, reverse-transcriptase PCR and immunohistochemistry confirmed the presence and distribution of EcPV2 within the lesion and suggested that p53 degradation may not be the mechanism by which this virus induces neoplastic transformation. The complete viral sequence in this Japanese case shows near perfect sequence homology with European reference strains of EcPV2, which may be useful when considering the target for future EcPV2 vaccine development. This report also serves to highlight the importance of EcPV2 in female (vulvar) neoplasia, which is less commonly recognized than EcPV2-induced male (penile or preputial) neoplasia. Finally, the SCC described in this mare was an unusual acantholytic variant that has not been reported previously in horses. It is the first report of EcPV2 identified from genital SCC in Asia and underscores the likely worldwide distribution of this virus and its consistent association with equine genital neoplasia.

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This is the first report of Equus caballus papillomavirus 2 (EcPV2)-associated genital squamous cell carcinoma (SCC) in Asia.

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This report features EcPV2 in vulvar neoplasia, which is less commonly recognized than EcPV2-induced penile neoplasia.

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Histopathologically, the SCC described in this mare was an unusual acantholytic variant that has not been reported previously.

EQUINE SARCOIDS IN CAPTIVE WILD EQUIDS: DIAGNOSTIC AND CLINICAL MANAGEMENT OF 16 CASES-A POSSIBLE PREDISPOSITION OF THE EUROPEAN COHORT OF SOMALI WILD ASS (EQUUS AFRICANUS SOMALIENSIS)?

Equine sarcoids (ES) were diagnosed in 12 Somali wild asses (SWA) (Equus africanus somaliensis) from 10 different institutions of the SWA European Endangered Species Programme from 1976 to 2019. Samples of surgically excised masses, biopsies, or necropsy samples were submitted for histologic and virologic analysis. In addition, tissue samples from one onager (Equus hemionus onager), one kulan (Equus hemionus kulan), and two Hartmann's mountain zebras (HMZ) (Equus zebra hartmannae) were examined. Histology confirmed the diagnosis of ES exhibiting the typical microscopic features. Polymerase chain reaction detected bovine papillomavirus type 1 (BPV1) DNA in eight SWA samples and bovine papillomavirus type 2 (BPV2) DNA in one SWA sample. The onager, kulan, and one HMZ sample tested positive for BPV1. The other HMZ tested positive for BPV1 and BPV2. This is the first report of ES in an onager. Surgical excision was the treatment elected by most veterinarians. A follow-up survey of the cases over several years after clinical diagnosis and therapy revealed variable individual outcome with ES recurrence in four cases. Three SWA and the kulan were euthanized due to the severity of the lesions. Nine affected SWA were males with seven having a sarcoid located at the prepuce. Because a genetic disposition is a risk factor for the development of ES in horses, this may also be true for endangered wild equids with few founder animals in their studbook history. Innovative approaches regarding therapy and prevention of ES in wild equids are therefore highly encouraged.

Identification of a Novel Papillomavirus Type (MfoiPV1) Associated with Acrochordon in a Stone Marten (Martes foina)

Papillomaviruses (PVs) are an extremely large group of viruses that cause skin and mucosal infections in humans and various domestic and wild animals. Nevertheless, there is limited knowledge about PVs in wildlife hosts, including mustelid species. This study describes a case in stone marten (Martes foina) with a clinical manifestation of skin tumor, which is rather atypical for infections with PVs. The result of the papillomavirus PCR performed on the skin tumor sample was positive, and the complete PV genome was determined in the studied sample using next-generation sequencing technology. The analysis of the PV genome revealed infection of the stone marten with a putative new PV type belonging to the Dyonupapillomavirus genus. The proposed new stone marten PV type was named MfoiPV1.

Anogenital-Associated Papillomaviruses in Animals: Focusing on Bos taurus Papillomaviruses

In contrast to the diverse studies on human papillomaviruses (HPVs), information on animal PVs associated with anogenital lesions is limited. In the animal kingdom, papillomas occur more commonly in cattle than in any other animals, and diverse types of Bos taurus papillomaviruses (BPVs) exist, including the very recently discovered BPV type 29 (BPV29). From this perspective, we will review previous studies describing PV types associated with anogenitals in animals, with a focus on BPVs. To date, two classical BPV types, classified into Deltapapillomavirus (BPV1 and BPV2) and Dyokappapapillomavirus (BPV22), and two novel Xipapillomaviruses (BPV28 and BPV29) have been identified from anogenital lesions and tissues of the domestic cow. Due to the limited reports describing anogenital-associated PVs in animals, the relationships between their phylogenetic and pathogenetic properties are still undiscovered. Animal studies are valuable not only for the veterinary field but also for human medicine, as animal diseases have been shown to mimic human diseases. Studies of anogenital-associated PVs in animals have a positive impact on various research fields.

Detection of a Putative Novel Papillomavirus Type within a Large Exophytic Papilloma on the Fetlock of a Horse

A 10-year-old horse presented with two 3-cm diameter exophytic masses over the fetlock. Histology was consistent with a hyperplastic squamous papilloma and numerous cell changes consistent with papillomavirus (PV) infection were visible. Partial sequences of PV L1 and E1 ORFs were amplified using consensus PCR primers. The sequences were most similar to Equus caballus type 1 (EcPV1). However, as the sequences were only around 73% similar to EcPV1, they appear to be from a novel PV type that is likely to be within the Zetapapillomavirus genus. The papillomas were treated with topical imiquimod and resolved within 14 weeks. The clinical presentation of the papillomas in the present case had marked differences to the clinical presentation of EcPV-1-induced papillomas, which are typically small, numerous and around the face. Observations from the present case increase the clinical spectrum of PV-induced lesions in this species as well as providing evidence of an additional novel papillomavirus that is able to cause disease in horses.

Characterization of Bovine papillomavirus 28 (BPV28) and a novel genotype BPV29 associated with vulval papillomas in cattle

Papillomavirus (PV) infections are associated with the development of cutaneous and mucosal tumors in humans and various animal species. In humans, infection of high-risk human PVs (HPVs) causes anogenital cancers, while in animals, anogenital-associated PVs are not well understood. Among animal PVs, Bos taurus PVs (BPVs) have the most diverse genotypes, up to 28 of them. The present study will report two unique BPVs identified in vulval papilloma lesions from two Holstein Friesian cattle by conventional PCR and sequencing. In the first case, BPV28 harboring two L1 open reading frames (ORFs) due to a five-nucleotide deletion was identified. In the second case, histologically diagnosed as papilloma, an unclassified BPV genotype was detected. However, in both cases, the immunohistochemistry against PV antigen was negative. The full genome of the unclassified BPV was amplified by inverse PCR and analyzed by genome-walking sequencing. The L1 nucleotide sequence was most identical to BPV genotype 6 (BPV6), showing 78 % identity, indicating that this novel BPV should be classified as species Xipapillomavirus 1, genotype BPV29. The mRNA expression of three early genes (E1, E2, E10), but not L1, was confirmed in both BPV28- and BPV29-detected papilloma lesions. The present study suggests the involvement of novel types of BPV in vulval papilloma. The alteration of BPV28 pathogenicity due to the frameshift mutation of L1 needs to be elucidated in the future.

Prevalence and Prognostic Impact of Equus caballus Papillomavirus Type 2 Infection in Equine Squamous Cell Carcinomas in Western Canadian Horses

Equus caballus papillomavirus type-2 (EcPV-2) has been proposed as a causal factor in equine genital squamous cell carcinoma (SCC). This study had 2 objectives: first, calculate the frequency of papillomavirus (PV) and EcPV-2 infection in papillomas, carcinomas in situ (CIS), and SCCs in Western Canadian horses; and second, determine if EcPV-2 status of equine SCCs is associated with overall survival (OS). EcPV-2 status of 115 archived tissue samples, spanning 6 years, was determined using broad spectrum (MY09/11) and EcPV-2-specific polymerase chain reaction (PCR) assays, EcPV-2-E6/E7 chromogenic RNA in situ hybridization (R-ISH), and amplicon sequencing. A retrospective survey gathered data on history, outcome, breeding, treatment, and rationales of referring veterinarians when managing PV-associated diseases. Histologic grade and completeness of surgical margins of SCCs were also considered. EcPV-2 DNA was identified in 10/58 (17%) SCC, 8/27 (30%) papillomas, 0/5 CIS, and 0/11 lesions identified as "other." Overall, 18/101 (18%) of these lesions were positive for EcPV-2. EcPV-2 was identified in 10/35 (29%) SCCs arising from genital tissues but in 0/22 SCCs from other locations. There was no association between breeding history and EcPV-2 status of genital SCCs. EcPV-2 status of genital SCCs was not associated with OS (P = .76). The strongest negative predictors of OS were a lack of treatment (P < .01) and recurrence post-treatment (P < .01). Weaker predictors of OS included older age at time of diagnosis (P = .02). Completeness of margins at surgical excision, concurrent disease, treatment type, anatomic location of the SCC (anogenital vs other), and histologic grade of the SCC did not influence OS (P > .1).

Prevalence of Equus caballus Papillomavirus Type-2 Infection and Seropositivity in Asymptomatic Western Canadian Horses

Equus caballus papillomavirus type 2 (EcPV-2) has been recognized as a potential cause of a subset of genital squamous cell carcinomas (SCCs) in horses. In the current study, we measured EcPV-2 seropositivity in 50 healthy horses from Western Canada, and these were compared to a herd of horses with known EcPV-2 exposure. Second, the presence of EcPV-2 DNA was measured using EcPV-2-specific PCR (polymerase chain reaction), performed on a variety of tissues collected at necropsy from 70 horses that lacked any history, gross, or histologic evidence of neoplasia or papillomavirus-associated disease. EcPV-2-specific RNA in situ hybridization (R-ISH) was performed on PCR-positive samples to identify the specific tissues infected. The prevalence of asymptomatic infection with EcPV-2 in Western Canadian horses was 20/70 (29%). Exposure to EcPV-2 as measured by seropositivity was 18/50 (36%). EcPV-2 positivity by anatomic location, as measured by R-ISH, was as follows: penis 10/29 (35%), vulva 5/34 (15%), eyelid 8/68 (12%), oral mucosa 7/65 (11%), skin from muzzle 7/68 (10%), and retropharyngeal lymph node 2/64 (3%). The youngest horses with EcPV-2 infection, based on PCR, were fetuses, suggesting for the first time that vertical transmission of EcPV-2 occurs in horses. The current study observed an increased prevalence of EcPV-2 as compared to previous studies. We suggest that this difference is due to our use of biopsies in place of superficial swabs. We propose that EcPV-2 infection in asymptomatic horses is more common than previously reported and that the virus' role in equine genital SCCs may be more complex than originally thought.

Progression of aural plaques to squamous cell carcinoma in a horse

BACKGROUND

Aural plaques are associated with and thought to be caused by one or more Equus caballus papillomaviruses (EcPV). Aural plaques have not previously been reported to be associated with squamous cell carcinoma (SCC).

HYPOTHESIS/OBJECTIVES

To describe a horse with aural plaques and squamous cell carcinoma (SCC) on the right pinna.

ANIMALS

A 28-year-old thoroughbred gelding presented for multiple plaques and a mass on the right pinna.

METHODS AND MATERIALS

Pinnal resection, histopathological investigation, multiple conventional PCRs for papillomavirus DNA and Sanger sequencing were performed.

RESULTS

Multiple, raised, pale tan, fronded plaques covered 60% of the concave surface of the right pinna. Focally these plaques coalesced into an exophytic ulcerated mass near the base of the pinna. Multiple aural plaques and a SCC were diagnosed histopathologically. EcPV4 was detected via PCR in a sample of the SCC.

CONCLUSIONS AND CLINICAL IMPORTANCE

This report demonstrates the possibility of malignant transformation from aural plaques to SCC on the pinna of a horse. To the best of the authors' knowledge, this is the first report of EcPV4 associated with SCC.

Leopardus wiedii Papillomavirus type 1, a novel papillomavirus species in the tree ocelot, suggests Felidae Lambdapapillomavirus polyphyletic origin and host-independent evolution

The limited knowledge on Papillomavirus diversity (particularly in wild animal species) influences the accuracy of PVs phylogeny and their evolutionary history, and hinders the comprehension of PVs pathogenicity, especially the mechanism of virus - related cancer progression. This study reports the identification of Leopardus wiedii Papillomavirus type 1 (LwiePV1), the first PV type within Lambdapapillomavirus in a Leopardus host. LwiePV1 full genome sequencing allowed the investigation of its taxonomic position and phylogeny. Based on results, LwiePV1 should be assigned to a novel PV species providing evidence for a polyphyletic origin of feline lambda PVs, and representing an exception to codivergence between feline lambda PVs and their hosts. Results improve our knowledge on PV diversity and pave the way to future studies investigating biological and evolutionary features of animal PVs.

Paving the way for more precise diagnosis of EcPV2-associated equine penile lesions

Background

There is growing evidence that equine papillomavirus type 2 (EcPV2) infection is causally associated with the development of equine genital squamous cell carcinomas (SCCs). Early stages of disease present clinically as plaques or wart-like lesions which can gradually progress to tumoural lesions. Histologically these lesions are inconsistently described as benign hyperplasia, papilloma, penile intraepithelial neoplasia (PIN), carcinoma in situ (CIS) or SCC. Guidelines for histological classification of early SCC precursor lesions are not precisely defined, leading to potential misdiagnosis. The aim of this study was to identify histologic criteria and diagnostic markers allowing for a more accurate diagnosis of EcPV2-associated equine penile lesions.

Results

A total of 61 archived equine penile lesions were histologically re-assessed and classified as benign hyperplasia, papilloma, CIS or SCC. From these, 19 representative lesions and adjacent normal skin were comparatively analysed for the presence of EcPV2 DNA and transcripts using PCR and RNA in situ hybridisation (RISH). All lesional samples were positive by EcPV2 PCR and RISH, while adjacent normal skin was negative. RISH analysis yielded signal distribution patterns that allowed distinction of early (hyperplasia, papilloma) from late stage lesions (CIS, SCC). Subsequently, the 19 lesions were further assessed for expression of p53, Ki67, MCM7 and MMP1 by immunohistochemistry (IHC). All four proteins were expressed in both normal and lesional tissue. However, p53 expression was up-regulated in basal keratinocyte layers of papillomas, CIS and SCCs, as well as in upper keratinocyte layers of CIS and SCCs. MCM7 expression was only up-regulated in upper proliferating keratinocyte layers of papillomas, CIS and SCCs.

Conclusion

This study proposes combining a refined histological protocol for analysis of equine penile lesions with PCR- and/or RISH based EcPV2-screening and p53/MCM7 IHC to more accurately determine the type of lesion. This may help to guide the choice of optimum treatment strategy, especially at early stages of disease.

Identification of a Novel Equine Papillomavirus in Semen from a Thoroughbred Stallion with a Penile Lesion

Papillomaviruses (PVs) have been identified in a wide range of animal species and are associated with a variety of disease syndromes including classical papillomatosis, aural plaques, and genital papillomas. In horses, 13 PVs have been described to date, falling into six genera. Using total RNA sequencing (meta-transcriptomics) we identified a novel equine papillomavirus in semen taken from a thoroughbred stallion suffering a genital lesion, which was confirmed by nested RT-PCR. We designate this novel virus Equus caballus papillomavirus 9 (EcPV9). The complete 7656 bp genome of EcPV9 exhibited similar characteristics to those of other horse papillomaviruses. Phylogenetic analysis based on concatenated E1-E2-L2-L1 amino acid sequences revealed that EcPV9 clustered with EcPV2, EcPV4, and EcPV5, although was distinct enough to represent a new viral species within the genus Dyoiotapapillomavirus (69.35%, 59.25%, and 58.00% nucleotide similarity to EcPV2, EcPV4, and EcPV5, respectively). In sum, we demonstrate the presence of a novel equine papillomavirus for which more detailed studies of disease association are merited.

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.

Identification of bovine papillomavirus type 1 and 2 from bovine anogenital fibropapillomas

Papillomavirus (PV) is a well-known pathogen associated with epithelial and mucosal neoplastic diseases. In contrast to human PVs, characterization of animal PVs from the aspect of anogenital neoplasm is still on a learning curve. In the present study, two vulval and one anal warts, histologically diagnosed as fibropapillomas, excised from dairy cattle were analyzed. PCR and sequencing revealed that bovine papillomavirus type 1 (BPV-1) and BPV-2 were detected from anal and vulval fibropapillomas, respectively. Immunohistochemistry detected PV antigen in a few differentiated keratinocytes of one vulval case. Reverse-transcriptase PCR detected the early region, but not the late region of BPV mRNA in all three cases. The present study will provide new insight into the relationship between BPV and anogenital papilloma in cattle.

Frequency of Equus caballus papillomavirus in equine aural plaques

Despite the reported association between aural plaques and the presence of Equus caballus papillomavirus (EcPV), there are few data regarding the distribution of viral types in different geographic regions or possible correlations for different papillomaviruses and lesion characteristics. We detected the presence and frequency of EcPV (1-7) DNA in aural plaque biopsies of horses from different regions of Brazil and identified the patterns of these infections or coinfections and their possible association with lesion severity. A total of 108 aural plaque biopsies from horses in the 5 geopolitical regions of Brazil were examined. We performed PCR to detect EcPV DNA in the biopsies. At least 1 type of EcPV was detected in 97% of the samples. EcPV coinfection was observed in 59% of the samples. Compared to the other viruses, EcPV-4 was found at the highest frequency in coinfection (84%) or individually identified (32%). EcPV-2 and -7 were not detected. No significant association was found between lesion characteristics (type and distribution) and either the viral type detected or the presence of coinfection. EcPV is widely distributed in Brazil, both isolated and in coinfection; the viral type does not appear to influence the clinical characteristics of equine aural plaques.

Isolation of equine papillomavirus type 1 from racing horse in Japan

Although many studies have been conducted worldwide for Equus caballus papillomavirus (EcPV), limited information is available on the virus in Japan. We recently collected one classical viral papillomatosis sample (E150904) from a racing horse in Japan. Papillomavirus infection was confirmed by histopathology, immunohistochemistry and PCR assays, and the sample was diagnosed as epithelial papilloma. Full-length genome of the virus was cloned and sequenced. It was 7,613 bp in length and had the same genome organization with reported EcPV-1. Moreover, phylogenetic analysis based on L1 gene revealed that the infection was caused by a variant of EcPV-1. This is the first report of EcPV infection in Japan, and would further contribute to the molecular epidemiological and pathological studies for EcPV.

Generalized papillomatosis in three horses associated with a novel equine papillomavirus (EcPV8)

BACKGROUND

Currently, seven equine papillomaviruses (PV) are known and are associated with one of three different and distinct clinical presentations.

HYPOTHESIS/OBJECTIVES

To report the clinical, histopathological and immunohistochemical findings in horses with generalized papillomatosis associated with a novel equine PV, Equus caballus papillomavirus 8 (EcPV8).

ANIMALS

Three client-owned quarter horses.

METHODS

Case report, retrospective.

RESULTS

Dozens to thousands of papillomas involved the axilla, inguinal area and proximal limbs as well as the ventral and lateral neck, thorax and abdomen. Lesions were sometimes confluent in ventral areas. Fewer lesions were on the face, ears, distal limbs and genitalia. Plaque-type papillomas were small, 0.5 to 1.5 cm in diameter and hyperkeratotic. Histologically, plaque-type papillomas prominently involved follicular infundibula. Immunohistochemical findings demonstrated PV antigen in superficial keratinocyte nuclei. PCR using degenerate primers for the PV L1 gene and sequencing of amplicons revealed PV DNA sequences that were 98% identical for all three cases, but shared <70% identity to other PVs. Horses were otherwise healthy; serum immunoglobulin levels and peripheral blood lymphocyte phenotyping did not identify a known immunodeficiency syndrome. Lesions nearly completely resolved after 1.5 years in one horse and persisted for two years in another, despite intralesional human IFN-alpha treatment. The oldest horse was lost to follow-up.

CONCLUSION AND CLINICAL IMPORTANCE

A novel equine papillomavirus (EcPV8) is associated with a distinct, plaque-type, generalized papillomatosis. Papillomas persisted for months to years, with or without treatment.

Papillomavirus infection and squamous cell carcinoma in horses

Squamous cell carcinoma (SCC) is a common disease that seriously impairs the health and welfare of affected horses and other equids. In humans, almost all cervical carcinomas, a high percentage of anogenital SCCs and a subset of SCCs of the head and neck are caused by high-risk human papillomavirus (hrHPV) infection. Since hrHPV-induced human cancers and equine SCC have similar cytological and histopathological features, it has been hypothesised that equine SCCs could also be induced by papillomaviruses. This review provides an overview of the current evidence for an aetiological association between papillomavirus infections and equine SCCs and SCC precursor lesions. SCC of apparently papillomavirus-unrelated aetiology are also discussed, as are recent advances in equine SCC prophylaxis.

Equine Genital Squamous Cell Carcinoma: In Situ Hybridization Identifies a Distinct Subset Containing Equus caballus Papillomavirus 2

Equus caballus papillomavirus 2 (EcPV2) has been proposed as an etiologic agent for genital squamous cell carcinoma (SCC), the most common malignant tumor of the horse penis. EcPV2 is commonly detected by polymerase chain reaction (PCR) on normal horse genitalia; therefore, unraveling the virus' role in oncogenic transformation requires other methods of detection. In this study, a highly sensitive multiple-probe chromogenic in situ hybridization (ISH) technique was designed to recognize the E6/E7 oncogenes of EcPV2. ISH demonstrated abundant virus within 6 of 13 penile and preputial SCCs, whereas evidence of solar damage was found in 6 cases that were negative for EcPV2 by ISH. The ISH technique is valuable for studies of pathogenesis, since it demonstrates for the first time that the vast majority of neoplastic cells contain virus. Moreover, hybridization was present in all metastases examined, implying stability of E6/E7 expression in these clonal populations of neoplastic cells. This study contributes to the accumulating evidence for a causal role of EcPV2 in a subset of genital SCCs in horses.

Equus asinus papillomavirus (EaPV1) provides new insights into equine papillomavirus diversity

We detected a novel papillomavirus (EaPV1) from healthy skin and from sun associated cutaneous lesions of an Asinara (Sardinia, Italy) white donkey reared in captivity in a wildlife recovery centre. The entire genome of EaPV1 was cloned, sequenced, and characterised. Genome is 7467 bp long, and shows some characteristic elements of horse papillomaviruses, including a small untranslated region between the early and late regions and the lack of the retinoblastoma tumour suppressor binding domain LXCXE in E7. Additionally, a typical E6 ORF is missing. EaPV1 DNA was detected in low copies in normal skin of white and grey donkeys of the Asinara Island, and does not transform rodent fibroblasts in standard transformation assays. Pairwise nucleotide alignments and phylogenetic analyses based on concatenated E1-E2-L1 amino acid sequences revealed the highest similarity with the Equine papillomavirus type 1. The discovery of EaPV1, the prototype of a novel genus and the first papillomavirus isolated in donkeys, confirms a broad diversity in Equidae papillomaviruses. Taken together, data suggest that EaPV1 is a non-malignant papillomavirus adapted to healthy skin of donkeys.

Animal papillomaviruses

We provide an overview of the host range, taxonomic classification and genomic diversity of animal papillomaviruses. The complete genomes of 112 non-human papillomavirus types, recovered from 54 different host species, are currently available in GenBank. The recent characterizations of reptilian papillomaviruses extend the host range of the Papillomaviridae to include all amniotes. Although the genetically diverse papillomaviruses have a highly conserved genomic lay-out, deviations from this prototypic genome organization are observed in several animal papillomaviruses, and only the core ORFs E1, E2, L2 and L1 are present in all characterized papillomavirus genomes. The discovery of papilloma-polyoma hybrids BPCV1 and BPCV2, containing a papillomaviral late region but an early region encoding typical polyomaviral nonstructural proteins, and the detection of recombination breakpoints between the early and late coding regions of cetacean papillomaviruses, could indicate that early and late gene cassettes of papillomaviruses are relatively independent entities that can be interchanged by recombination.