Bovine papillomavirus type 1 and Equus caballus papillomavirus 2 in equine squamous cell carcinoma of the head and neck in a Connemara mare

Equus caballus papillomavirus type 2 (EcPV2)-associated benign penile lesions and squamous cell carcinomas

BACKGROUND

Squamous cell carcinoma is the most common genital, ocular and gastric tumour in horses. Equus caballus papillomavirus type 2 (EcPV2) DNA has been detected in several studies in equine penile squamous cell carcinomas (SCCs) and precursor lesions providing evidence of a causal role of EcPV2 in equine genital SCCs. Recently, EcPV2 E6/E7 nucleic acids were also detected in equine gastric SCCs, but further studies are required to determine the role of EcPV2 infection in the pathogenesis of gastric SCC. EcPV2 nucleic acids have been rarely described in ocular SCCs and precursor lesions.

OBJECTIVES

To investigate the presence of EcPV2 nucleic acids with polymerase chain reaction (PCR) and in situ hybridisation (ISH) in penile hyperplasias, papillomas and SCCs in horses and to determine whether EcPV2 nucleic acids can be detected in SCCs affecting other locations, including the stomach, ocular tissues and larynx.

METHODS

Twenty-one archival formalin-fixed paraffin embedded (FFPE) tissue samples, including 12 genital lesions comprising penile hyperplasias, papillomas and SCCs, 6 ocular SCCs, 2 gastric SCCs and 1 laryngeal SCC, were screened by PCR and ISH for EcPV2 E6/E7 DNA and mRNA. Archival FFPE tissue samples (eyelid and penile mucosa and preputium) from six horses without a diagnosis or history of neoplastic or papillomavirus-associated disease were included as controls.

RESULTS

EcPV2 nucleic acids were detected by PCR and ISH in all genital lesions (12/12) and gastric SCCs (2/2), in two ocular SCCs (2/6) and in one laryngeal SCC (1/1). In control horses, one eyelid sample was positive in PCR but not in ISH. The remaining control samples were negative for EcPV2 E6/E7 nucleic acids in PCR and ISH.

CONCLUSIONS

These results further support the role of EcPV2 infection in the development of equine genital SCCs and suggest that EcPV2 infection may also act as a predisposing factor for other SCCs in horses, including gastric, ocular and laryngeal 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.

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.

Establishment of a Three-Dimensional In Vitro Model of Equine Papillomavirus Type 2 Infection

There is growing evidence that equine papillomavirus type 2 (EcPV2) infection is etiologically associated with the development of genital squamous cell carcinoma (SCC) and precursor lesions in equids. However, the precise mechanisms underlying neoplastic progression remain unknown. To allow the study of EcPV2-induced carcinogenesis, we aimed to establish a primary equine cell culture model of EcPV2 infection. Three-dimensional (3D) raft cultures were generated from equine penile perilesional skin, plaques and SCCs. Using histological, molecular biological and immunohistochemical methods, rafts versus corresponding natural tissue sections were compared with regard to morphology, presence of EcPV2 DNA, presence and location of EcPV2 gene transcripts and expression of epithelial, mesenchymal and tumor/proliferation markers. Raft cultures from perilesional skin harboring only a few EcPV2-positive (EcPV2+) cells accurately recapitulated the differentiation process of normal skin, whilst rafts from EcPV2+ penile plaques were structurally organized but showed early hyperplasia. Rafts from EcPV2+ SCCs exhibited pronounced hyperplasia and marked dysplasia. Raft levels of EcPV2 oncogene transcription (E6/E7) and expression of tumor/proliferation markers p53, Ki67 and MCM7 expression positively correlated with neoplastic progression, again reflecting the natural situation. Three-dimensional raft cultures accurately reflected major features of corresponding ex vivo material, thus constituting a valuable new research model to study EcPV2-induced carcinogenesis.

DDB2 Genetic Risk Factor for Ocular Squamous Cell Carcinoma Identified in Three Additional Horse Breeds

Squamous cell carcinoma (SCC) is the most common cancer affecting the equine eye. A missense variant within the gene damage-specific DNA binding protein 2 (DDB2 c.1013C>T, p.Thr338Met) was previously identified as a causal recessive genetic risk factor for the development of ocular SCC within Haflingers, Belgian Draft horses, and Rocky Mountain Horses, but not in the Appaloosa or Arabian breeds. This study aimed to evaluate three cases of ocular SCC in additional breeds and determine if DNA testing for the DDB2 variant in warmblood horses and Connemara ponies is warranted. Histopathology confirmed ocular SCC in all three cases and DNA testing confirmed each horse was homozygous for the DDB2 risk factor. The DDB2 risk allele frequency was estimated to be 0.0043 for Holsteiners (N = 115), 0.014 for Belgian Warmbloods (N = 71), and 0.22 for Connemara Ponies (N = 86). Taken together these data support using DNA testing for DDB2 in Connemara Ponies to assist in mate selection and clinical management. Given the low observed allele frequencies in both the Holsteiner and Belgian Warmblood breeds and that the case under investigation was a warmblood cross-bred, evaluating additional SCC affected warmbloods is warranted to fully determine the importance of DDB2 genotyping as a risk factor in warmblood breeds.

Molecular typing of equine papillomavirus and autovaccination to treat horses with cutaneous papillomatosis

OBJECTIVE

The aim of this study was to evaluate formalin-inactivated autovaccination to treat cutaneous papillomatosis and to perform molecular typing of the papillomavirus in four horses (two foals, one 3-year-old filly and a 5-year-old stallion).

METHODS

Histopathological slides of lesions were prepared and stained with haematoxylin and eosin (H&E) to establish a diagnosis that was based on observation koilocytosis, which is a pathognomonic cytopathic change that is associated with papillomatosis, using light microscopy. Polymerase chain reaction (PCR) and DNA sequencing were performed using the EPV-R and EPV-F primer set.

RESULTS

In histopathological examination, koilocyte formation and occasional intranuclear viral inclusions were detected in the papillomas. A 334-base pair (bp) fragment of the E2 and L2 genes from the EPV genome was amplified using the EPV-R and EPV-F primer set. This fragment contained 215 bp from the E2 gene and 56 bp from the L2 gene; these were found to be 98.78% to 98.97% identical to the known EcPV type-1 sequence (AF498323).

CONCLUSION

Three horses with cutaneous papillomatosis were administered two doses of a formalin-inactivated preparation of papillomatous lesions at 7-day intervals. The papillomatous lesions were observed to decrease gradually 1 week after the last vaccination, and all warts had resolved within 2-3 weeks. One horse with cutaneous papillomatosis was left as an unvaccinated control, and no changes to the lesions were noted. To the best of our knowledge, this is the first report of EcPV type-1 infection, autovaccine preparation and molecular typing in Turkey.

Bovine Papillomavirus Type 2 Infection Associated with Papillomatosis of the Amniotic Membrane in Water Buffaloes (Bubalus bubalis)

Multiple papillomatous nodules were observed scattered over the amniotic membrane in six water buffaloes that had recently aborted. Grossly, some of the nodules had multiple villous projections while others appeared as single prominent conical or cylindrical horns. Histology revealed folded hyperplastic and hyperkeratotic epithelium supported by a narrow fibro-vascular stalk. Using PCR, sequences of the bovine Deltapapillomavirus type 2 (BPV-2) E5 gene were amplified from the amniotic papillomas. Furthermore, expression of the E5 gene was detected using reverse transcription (RT)-PCR. Western blotting revealed BPV-2 E5 oncoprotein as well as L1 protein, suggesting both abortive and productive infection. Additionally, a functional complex composed of BPV-2 E5 oncoprotein and the phosphorylated PDGFβR was detected, which is consistent with the activation of PDGFβR by the interaction with BPV-2 E5 oncoprotein. These results demonstrate that BPV-2 can infect the amnion of water buffaloes and suggest that this infection may cause proliferation of the epithelial cells of the amnion. While the precise pathogenesis in uncertain, it is possible that BPV-2 infection of stratified squamous epithelial cells within squamous metaplasia foci and/or amniotic plaques could lead to papilloma formation. Papillomavirus-associated amniotic papillomas have not previously been reported in any species, including humans.

Additional Evidence for DDB2 T338M as a Genetic Risk Factor for Ocular Squamous Cell Carcinoma in Horses

Squamous cell carcinoma (SCC) is the most common periocular cancer in horses and the second most common tumor of the horse overall. A missense mutation in damage-specific DNA-binding protein 2 (DDB2, c.1012 C>T, p.Thr338Met) was previously found to be strongly associated with ocular SCC in Haflinger and Belgian horses, explaining 76% of cases across both breeds. To determine if this same variant in DDB2 contributes to risk for ocular SCC in the Arabian, Appaloosa, and Percheron breeds and to determine if the variant contributes to risk for oral or urogenital SCC, histologically confirmed SCC cases were genotyped for the DDB2 variant and associations were investigated. Horses with urogenital SCC that were heterozygous for the DDB2 risk allele were identified in the Appaloosa breed, but a significant association between the DDB2 variant and SCC occurring at any location in this breed was not detected. The risk allele was not identified in Arabians, and no Percherons were homozygous for the risk allele. High-throughput sequencing data from six Haflingers were analyzed to ascertain if any other variant from the previously associated 483 kb locus on ECA12 was more concordant with the SCC phenotype than the DDB2 variant. Sixty polymorphisms were prioritized for evaluation, and no other variant from this locus explained the genetic risk better than the DDB2 allele (P = 3.39 × 10⁻¹⁷, n = 118). These data provide further support of the DDB2 variant contributing to risk for ocular SCC, specifically in the Haflinger and Belgian breeds.

Laryngeal squamous cell carcinoma and papilloma associated with Equus caballus papillomavirus 2 in a horse

A case of laryngeal squamous cell carcinoma (SCC) and squamous papilloma in a 19-year-old Thoroughbred stallion is described. The animal exhibited severe wheezing caused by laryngopharyngeal stenosis. Histological examination identified laryngeal, laryngotracheal, and guttural pouch tumor masses consisting of areas of SCC. In the epiglottic lesion, the overlying epithelium was replaced by papilloma cells, and superficial cells frequently had nuclear inclusion bodies that expressed oncoprotein E6, which is characteristic of high risk human papillomaviruses. The papillomatous epithelium was continuous with epithelium composed of SCC cells. Equus caballus papillomavirus 2 (EcPV2) DNA was detected in the guttural pouch tumor. These findings suggest that laryngeal SCC and papilloma are a continuum of EcPV2-induced neoplastic lesions in horses.

A missense mutation in damage-specific DNA binding protein 2 is a genetic risk factor for ocular squamous cell carcinoma in Belgian horses

BACKGROUND

Belgian horses are commonly affected with ocular squamous cell carcinoma (SCC), the most common cancer of the equine eye. A missense mutation in damage-specific DNA binding protein 2 (DDB2 c.1013C>T, p.Thr338Met) has been established as a recessive genetic risk factor for ocular SCC in the Haflinger breed. A sample of Belgian horses with unknown SCC phenotype was shown to possess this variant at a similar frequency to the Haflinger breed. Retrospective studies indicate that chestnut coat colour may predispose to the development of SCC.

OBJECTIVES

To determine if DDB2 c.1013C>T is a risk factor for ocular SCC in a strictly phenotyped sample of Belgian horses. To investigate associations between coat colour loci genotypes and ocular SCC.

STUDY DESIGN

Retrospective and prospective case identification, genetic investigation.

METHODS

Genomic DNA was isolated from blood, hair or formalin-fixed paraffin-embedded tissue from 25 Belgian horses with histologically confirmed ocular SCC and 18 unaffected Belgian horses. Association testing of 34 single nucleotide variants from 11 genomic loci and genotyping for DDB2 c.1013C>T and coat colour alleles were performed. Exons of DDB2 were sequenced in four cases and two controls. Associations were analysed by Chi-square or Fisher's exact tests and relative risk was calculated.

RESULTS

Homozygosity for DDB2 c.1013C>T was significantly associated with ocular SCC (P = 7.4 × 10^-7 ). Seventy-six per cent of affected horses were homozygous for the variant. Relative risk for homozygous horses developing SCC was 4.0 (P = 1.0 × 10^-4 ). Sequencing DDB2 did not identify a variant more concordant with disease phenotype. An association between disease and coat colour loci was not identified.

MAIN LIMITATIONS

Phenotyping was determined at a single timepoint. Each included horse genotyped as chestnut, so association with this MC1R variant could not be investigated.

CONCLUSIONS

A missense variant, DDB2 c.1013C>T, p.Thr338Met, is a risk factor for ocular SCC in Belgian horses. A genetic risk test is commercially available.

Congenital papillomavirus infection in cattle: Evidence for transplacental transmission

Vertical transmission of bovine papillomavirus (BPV) infection was investigated on livers and kidneys of four foetuses from cows suffering from BPV-2-associated urothelial cancers of the urinary bladder. PCR analysis revealed the presence of BPV-2 E5 DNA in the livers and kidneys of two foetuses. Amplified DNA fragments, composed of 502 bp, showed a 100% homology with BPV-2 sequences (GenBank accession number: M20219.1). BPV-2 was found to be transcriptionally active. Indeed, reverse transcriptase (RT)-PCR showed BPV-2 E5 transcripts. Sequencing of amplified cDNA, composed of 154 bp, showed a 100% identity with BPV-2 E5 sequences (GenBank accession number: M20219.1). Western blot analysis revealed the presence of dimers of E5 oncoprotein. Furthermore, a statistically significant increase of the phosphorylated (activated) form of the platelet-derived growth factor ß receptor (PDGFßR) was also detected in the fetal tissues. PDGFßR is believed to form the most important interaction with the E5 oncoprotein, thus regulating biological activity of virus protein. The strong concordance between virus found in fetal organs with virus detected in infected mothers provides evidence that BPV-2 can spread through blood and vertical infection occurs via transplacental transmission. Finally, molecular findings of this study raise unsolved questions about the potential role of BPVs in reproductive disorders. The presence of E5 oncoprotein, as in adult organs, may also activate the constitutive receptor PDGFßR in foetal organs, which plays a pivotal role in angiogenesis and embryonic development. Therefore, abnormal phosphorylation of PDGFßR may be involved in vascular and organogenesis abnormalities other than cancer.

Oral fibropapillomatosis and epidermal hyperplasia of the lip in newborn lambs associated with bovine Deltapapillomavirus

Congenital fibropapillomatosis of the gingiva and oral mucosa and epidermal hyperplasia of the lip are described, for the first time, in two newborn lambs. Expression of the E5 oncoprotein of bovine deltapapillomavirus types 2 (BPV-2) and -13 (BPV-13) was detected in both fibropapillomas and the hyperplastic epidermal cells suggesting the BPV infection was the cause of the proliferative lesions. No DNA sequences of BPV-1 and BPV-14 were detected. Both BPV-2 and BPV-13 DNA were also amplified from peripheral blood mononuclear cells (PBMCs) of the newborn lambs’ dams. The concordance between BPV genotypes detected in the blood of dam and the oral and skin pathological samples of their offspring suggests that a vertical hematogeneous transmission was most likely source of BPV infection. Immunoblotting revealed the presence of E5 dimers allowing the viral protein to be biologically active. E5 dimers bind and activate the platelet derived growth factor β receptor (PDGFβR), a major molecular mechanism contributing to disease. The detection of E5 protein within the proliferating cells therefore adds further evidence that the BPV infection was the cause of the proliferative lesions seen in these lambs. This is the first evidence of vertical transmission of BPVs in sheep resulting in a clinical disease.

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.

Equine papillomavirus type 2: An equine equivalent to human papillomavirus 16?

In horses, squamous cell carcinomas (SCC) commonly affect the external genitals. There is growing evidence that equine papillomavirus type 2 (EcPV2) infection promotes disease development. To assess the possible association of EcPV2 with equine SCCs of the head (HSCC), 15 HSCC DNA samples were screened by E6/E7, E2, and LCR PCR and amplicons were analysed for sequence variations. The physical form of EcPV2 in HSCC, genital lesions, and smegma from horses with SCC was then addressed using EcPV2 immunocapture PCR (IC/PCR) for detection of virion, and E6 vs. E2 qPCR to investigate possible integration events. Four of 15 HSCC tested positive for EcPV2 DNA and harboured known or novel genetic variants of E6, E7, E2 and the LCR. Eighteen of 35 sample extracts including 3/4 smegma samples scored positive by IC/PCR, suggesting that about 51% of tested extracts harboured virions. E6/E2 qPCR from tumour DNA revealed E2/E6 copies/cell ranging between <1 (E2; E6) and 797 (E2) or 1434 (E6). IC/PCR-positive smegma samples contained higher E2 and E6 copy numbers, ranging between 1490 and 4.95×10⁵ (E2) or 2227 and 8.54×10⁵ (E6) copies/cell. Together with IC/PCR results, this finding suggests that smegma can serve as a rich EcPV2 reservoir. HSCCs harboured significantly lower viral DNA amounts (<1-25 copies/cell) than most genital tumour and smegma DNA isolates. The majority of samples contained more E6 than E2 DNA, with E6:E2 ratios ranging between 0.88 and 4.12. Although not statistically significant (P>0.05), this finding suggests that EcPV2 can integrate into the equine host cell genome.

Potential of a BPV1 L1 VLP vaccine to prevent BPV1- or BPV2-induced pseudo-sarcoid formation and safety and immunogenicity of EcPV2 L1 VLPs in horse

We have previously shown that immunization of horses with bovine papillomavirus type 1 (BPV1) L1 virus-like particles (VLPs) is safe and highly immunogenic and that BPV1 and bovine papillomavirus type 2 (BPV2) are closely related serotypes. Here we evaluated the protective potential of a BPV1 L1 VLP vaccine against experimental BPV1 and BPV2 challenge and studied the safety and immunogenicity of a bivalent equine papillomavirus type 2 (EcPV2)/BPV1 L1 VLP vaccine. Fourteen healthy horses were immunized with BPV1 L1 VLPs (100 µg per injection) plus adjuvant on days 0 and 28, while seven remained unvaccinated. On day 42, all 21 horses were challenged intradermally at 10 sites of the neck with 107 BPV1 virions per injection. In analogy, 14 horses immunized twice with EcPV2 plus BPV1 L1 VLPs (50 µg each) and seven control animals were challenged with 107 BPV2 virions per injection. Immunization with BPV1 L1 VLPs alone induced a robust antibody response (day 42 median titre: 12 800), and BPV1-inoculated skin remained unchanged in 13/14 vaccinated horses. Immunization with the bivalent vaccine was safe, resulted in lower median day 42 antibody titres of 400 for BPV1 and 1600 for EcPV2 and conferred significant yet incomplete cross-protection from BPV2-induced tumour formation, with 11/14 horses developing small, short-lived papules. Control horses developed pseudo-sarcoids at all inoculation sites. The monovalent BPV1 L1 VLP vaccine proved highly effective in protecting horses from BPV1-induced pseudo-sarcoid formation. Incomplete protection from BPV2-induced tumour development conferred by the bivalent vaccine is due to the poorer immune response by immune interference or lower cross-neutralization titres to heterologous BPV2 virions.

Neoplasia in 125 donkeys (Equus asinus): literature review and a survey of five veterinary schools in the United States and Canada

A diagnosis of neoplasia was noted in 125 of 357 donkeys (35%) in our review of medical records from 5 veterinary schools in the United States and Canada. Equine sarcoid was the most common tumor in our study, accounting for 72% of all tumors and 82% of cutaneous tumors. Soft-tissue sarcomas were the second most common skin tumors. All other types of neoplasia were rare. Important differences in the occurrence of neoplasia in donkeys compared to horses included the rarity or absence of squamous cell carcinoma in any organ system and gray horse melanoma. Lymphosarcoma, the most common malignant tumor in horses, appears to be very rare in donkeys. We report several tumors in donkeys including melanocytoma, peripheral nerve sheath tumor, and gastrointestinal stromal tumor. Our data demonstrate commonalities as well as differences in neoplastic diseases of donkeys and horses. Understanding differences in carcinogenesis among these 2 closely related species can inform researchers pursuing pathogenic mechanisms of equine disease and inform veterinary diagnosticians regarding tumor prevalence.

Establishment of an in vitro equine papillomavirus type 2 (EcPV2) neutralization assay and a VLP-based vaccine for protection of equids against EcPV2-associated genital tumors

The consistent and specific presence of Equus caballus papillomavirus type 2 (EcPV2) DNA and mRNA in equine genital squamous cell carcinoma (gSCC) is suggestive of an etiological role in tumor development. To further validate this concept, EcPV2-neutralizing serum antibody titers were determined by an EcPV2 pseudovirion (PsV) neutralization assay. Furthermore, an EcPV2 L1 virus-like particle (VLP)-based vaccine was generated and its prophylactic efficacy evaluated in vivo. All 6/6 gSCC-affected, but only 3/20 tumor-free age-matched animals revealed EcPV2-neutralizing serum antibody titers by PsV assay. Vaccination of NZW rabbits and BalbC mice with EcPV2 L1 VLP using Freund׳s or alum respectively as adjuvant induced high-titer neutralizing serum antibodies (1600-12,800). Passive transfer with rabbit EcPV2-VLP immune sera completely protected mice from experimental vaginal EcPV2 PsV infection. These findings support the impact of EcPV2 in equine gSCC development and recommend EcPV2 L1 VLP as prophylactic vaccine against EcPV2 infection and associated disease in equids.

Caracterização molecular de DNA de Delta papillomavirus bovino (BPV1, 2 e 13) em sarcoides equinos

Resumo:Sarcoides são tumores fibroblásticos, considerados os tumores de pele mais comuns em pele de equinos e que raramente apresentam regressão espontânea. Papilomavírus bovino (BPV) tipos 1 e 2 são relacionados com a patogenia do sarcoide e, provavelmente, o BPV tipo 13 (BPV13), recentemente descrito, também pode estar associado com a formação dessa lesão. Neste estudo, 20 amostras de lesões cutâneas, sendo 12 constituídas por tecidos frescos e 8 amostras de tecido fixado em formalina e embebido em parafina, provenientes de 15 cavalos foram utilizadas para a identificação do DNA de BPV. A análise histopatológica (HE) confirmou todas as lesões como sarcoide. Para a amplificação do DNA de papilomavírus (PV) foram realizadas três reações de PCR. Como triagem, os primers IFNR2/IDNT2 foram utilizados para amplificar um fragmento da ORF L1 do PV. O segundo par de primersutilizado é complementar a sequência dos genes E5 e L2 de BPVs 1, 2 e 13. O terceiro par de primers(FAP59/FAP64) utilizado tem o gene L1 como alvo. A primeira e a segunda PCRs permitiram amplificar produtos em todas as amostras avaliadas. Entretanto, na terceira reação, na qual foram utilizados os primers FAP, foi possível amplificar produtos com tamanho molecular esperado somente nas amostras constituídas por tecidos frescos. O sequenciamento de nucleotídeos e as análises filogenéticas realizadas nos fragmentos E5L2 resultaram na identificação de BPV1, 2 e 13 em 14 (70%), 2 (10%) e em 4 (20%) amostras de sarcoides, respectivamente. As amostras de sarcoides de um dos animais continha somente o DNA de BPV1. Entretanto, nas amostras provenientes do segundo cavalo foi possível identificar o DNA de três tipos de Deltapapillomavirus bovino (BPV1, 2 e 13) em lesões distintas. Este estudo ratifica a presença do DNA de BPV1, 2 e 13 em lesões de sarcoides em equinos, além de identificar três tipos de BPVs em um mesmo animal e descrever pela primeira vez no Brasil a presença de BPV1 e 2 nesse tipo de lesão.

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.

Detection of papillomavirus in equine periocular and penile squamous cell carcinoma

Squamous cell carcinoma (SCC) is the most common tumor arising in the periocular and penile areas of horses. Both ultraviolet radiation and papillomaviruses have been implicated in the pathogenesis of SCC in various species, including the horse. This retrospective study used polymerase chain reaction (PCR) to detect papillomavirus DNA in archival biopsy samples from equine periocular and penile SCC from 3 different geographic areas (northeast, southeast, and central United States). Forty-two periocular SCCs were tested; none contained papillomavirus DNA. Twenty-two penile SCCs were tested, and papillomavirus DNA was identified in 10 (43%) cases. Sequencing of the PCR products revealed homology with Equus caballus papillomavirus 2 (EcPV-2). No geographic distribution in the detection of papillomavirus was identified. Penile SCCs were significantly more likely to be papillomavirus positive than the periocular SCCs ( P < 0.001). The role of papillomavirus in the development of penile SCC requires further investigation. The differing pathogeneses of periocular and penile SCC suggest that the tumors may respond differently to treatment.

Comparison of the levels of Equus caballus papillomavirus type 2 (EcPV-2) DNA in equine squamous cell carcinomas and non-cancerous tissues using quantitative PCR

Equus caballus papillomavirus type 2 (EcPV-2) infection has been associated with equine genital squamous cell carcinomas (SCCs). However, quantitative PCR (qPCR) has not been performed to determine viral copy numbers within these lesions. Additionally, the frequency with which EcPV-2 can be detected in other common sites of equine SCC development remains uncertain. The aim of this study was to develop a qPCR assay to estimate the viral load in a variety of equine tissue samples. These included 40 SCC lesions, 19 penile non-SCC or precursor disease lesions, and 222 tissues without observable lesions from SCC-prone sites on clinically normal horses. EcPV-2 DNA was present significantly more frequently, and in higher copy numbers, in equine penile SCC lesions than in either healthy penile mucosa or non-SCC penile lesions. This supports the hypothesis that EcPV-2 is involved in development of penile SCCs and suggests that penile EcPV-2 infection is rare in the absence of SCCs. Samples of normal vulval mucosa rarely contained EcPV-2 DNA and none of the nictitating membrane samples contained EcPV-2 DNA, indicating that asymptomatic EcPV-2 infection is uncommon at these sites. EcPV-2 DNA was detected in a proportion of both SCCs and normal samples from the oral cavity or pharynx, although there were no significant differences in the rate of infection or viral copy number between the SCCs and the normal mucosal samples. As such, the role of EcPV-2 in development of SCCs in this location remains to be established.

Four novel papillomavirus sequences support a broad diversity among equine papillomaviruses

Papillomaviruses appear to be species-specific pathogens, and it was suggested that each animal species might harbour its own set of papillomaviruses. However, all approaches addressing the underlying evolutionary phenomena still suffer from very limited data about animal papillomaviruses. In case of the horse for example, only three equine papillomaviruses (EcPVs) have been identified. To further address the situation in this host, suspected papillomavirus-associated lesions were tested for EcPV DNA. Four novel EcPV types were detected and their genomes entirely cloned and sequenced. They display the characteristic organization, with early (E) and late (L) regions harbouring the seven classical open reading frames divided by non-coding regions. They were named EcPVs 4, 5, 6 and 7, according to their dissimilarity to other papillomaviruses. Most L1 nucleotide identities were shared with EcPV2 in case of EcPV4 (62 %) and EcPV5 (60 %) or with EcPV3 in case of EcPV6 (70 %) and EcPV7 (71 %). Thus, EcPVs 4 and 5 may establish novel species within the genus Dyoiota, while EcPVs 6 and 7 might fit into the genus Dyorho and belong to the same species as EcPV3. They were found in genital plaques (EcPV4), aural plaques (EcPV5, EcPV6) or penile masses (EcPV7). Interestingly, PCR analysis revealed the DNA of EcPV2 and EcPV4 as well as of EcPV3 and EcPV6 together in the same tissue samples, respectively. In conclusion, the DNA of four novel EcPV types was identified and cloned. They cluster with the known types and support broad genetic EcPV diversity in at least two of the known clades. Furthermore, PCR assays also provide evidence for EcPV co-infections in horses.

Bovine papillomavirus type 2 infects the urinary bladder of water buffalo (Bubalus bubalis) and plays a crucial role in bubaline urothelial carcinogenesis

Bovine papillomavirus type 2 (BPV-2) has been shown to infect and play a role in urinary bladder carcinogenesis of buffaloes grazed on pastures with ferns from the Marmara and Black Sea Regions of Turkey. BPV-2 DNA has been found in both neoplastic and non-neoplastic lesions of the urinary bladder. Furthermore, this virus may be a normal inhabitant of the urinary bladder since BPV-2 DNA has also been detected in clinically normal buffaloes. The viral activation by fern immunosuppressant or carcinogen may trigger the urothelial cell transformation. The E5 oncoprotein was solely detected in urothelial tumours and appeared to be co-localized with the overexpressed and phosphorylated platelet derived growth factor (PDGF) β receptor in a double-colour immunofluorescence assay. Our results indicate that the E5-PDGF β receptor interaction also occurs in spontaneous tumours of the bubaline urinary bladder, revealing an additional role of BPV-2 in bladder carcinogenesis of buffaloes.

Phylogenetic and structural studies of a novel equine papillomavirus identified from aural plaques

Papillomaviruses (PVs) infect a wide range of animal species and show great genetic diversity. To date, excluding equine sarcoids, only three species of PVs were identified associated with lesions in horses: Equus caballus papillomavirus 1 (EcPV1-cutaneous), EcPV2 (genital) and EcPV3 (aural plaques). In this study, we identified a novel equine PV from aural plaques, which we designated EcPV4. Cutaneous samples from horses with lesions that were microscopically diagnosed as aural plaques were subjected to DNA extraction, amplification and sequencing. Rolling circle amplification and inverse PCR with specific primers confirmed the presence of an approximately 8 kb circular genome. The full-length EcPV4 L1 major capsid protein sequence has 1488 nucleotides (495 amino acids). EcPV4 had a sequence identity of only 53.3%, 60.2% and 51.7% when compared with the published sequences for EcPV1, EcPV2 and EcPV3, respectively. A Bayesian phylogenetic analysis indicated that EcPV4 clusters with EcPV2, but not with EcPV1 and EcPV3. Using the current PV classification system that is based on the nucleotide sequence of L1, we could not define the genus of the newly identified virus. Therefore, a structural analysis of the L1 protein was carried out to aid in this classification because EcPV4 cause lesion similar to the lesion caused by EcPV3. A comparison of the superficial loops demonstrated a distinct amino acid conservation pattern between EcPV4/EcPV2 and EcPV4/EcPV3. These results demonstrate the presence of a new equine PV species and that structural studies could be useful in the classification of PVs.