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

In January 2010, 18 months after excision of an ocular squamous cell carcinoma (SCC), a Connemara mare presented with anorexia and periorbital/parotideal lesions. Post mortem examination revealed these lesions as forming one entity, with 2 additional growths in the retropharyngeal region and the left jugular groove, respectively. The lesions were confirmed histopathologically as SCCs. Using PCR, peripheral blood mononuclear cells (PBMCs) from 2008 and 2010, tumour tissue, intact skin and vulval mucosa were screened for Equus caballus papillomavirus type 2 (EcPV-2) and bovine papillomavirus types 1 and 2 (BPV-1/2) DNA. Whereas PBMCs from 2008 scored negative, EcPV-2 DNA was present in PBMCs and SCCs from 2010. Furthermore, reverse transcription PCR revealed EcPV-2 E6 transcripts in these samples. BPV-1/2 DNA, but not RNA, was demonstrated in the periorbital/parotideal mass, the SCC of the jugular groove, vulval mucosa and intact skin, but not in the pharyngeal SCC and PBMCs. Sequencing revealed a 99% similarity of EcPV-2 amplicons with the published EcPV-2 sequence. BPV-1/2 amplicons corresponded to BPV type 1. This report is the first to describe co-presence of BPV-1 and EcPV-2 DNA in a pony affected by an uncommon form of nongenital SCC, and the detection of EcPV-2 transcripts in lesions and PBMCs.

Consistent detection of bovine papillomavirus in lesions, intact skin and peripheral blood mononuclear cells of horses affected by hoof canker.

REASONS FOR PERFORMING THE STUDY: Equine hoof canker is a chronic proliferative pododermatitis of as yet unknown aetiology. Like equine sarcoid disease, canker is a therapy-resistant disorder characterised by hyperkeratosis, acanthosis and a marked tendency to recur. HYPOTHESIS: There is an association of sarcoid-inducing bovine papillomaviruses of types 1 and 2 (BPV-1, BPV-2) with hoof canker disease. METHODS: Using PCR-based techniques, we assessed canker tissue, intact skin and/or peripheral blood mononuclear cells (PBMCs) of 25 canker-affected horses for the presence of sarcoid-associated BPV-1 and -2. RESULTS: Conventional PCR revealed BPV-1/-2 DNA in 24/24 canker, 12/13 skin and 10/11 PBMC DNA isolates. Using inverse PCR, full-length BPV episomes were detected in 1/5 canker specimens. Sequencing of viral early and late genes amplified from canker, intact skin and PBMC DNA of 2 cases revealed an overall identity of 98% to BPV-1. Viral DNA loads amounted to ≤16 copies per cell in canker tissue and intact skin, and to ≤0.35 copies per PBMC, as determined by quantitative PCR. Using RT-PCR, the viral major oncogene E5 was shown to be transcribed in 2/4 canker tissue specimens and 5/7 PBMC isolates. Immunocapture PCR from 7 canker and 6 skin extract supernatants revealed capsomere-associated viral DNA in one canker and one skin sample. Hoof tissue, skin and PBMCs collected from 13 individuals with no signs of canker or BPV-related malignancies scored negative throughout the experiments. CONCLUSION: These findings suggest that the observed presence of BPV-1/-2 in canker-affected horses is not coincidental but indicative of an active contribution to hoof canker disease. POTENTIAL RELEVANCE: The use of antivirals and/or immune modulators may help improving canker therapy.

Successful treatment of equine sarcoids by topical aciclovir application.

Based on the anecdotally reported eradication of a sarcoid using aciclovir cream, the curative potential of this ointment was investigated in 22 sarcoid-affected horses referred to the Equine Clinic Tillysburg, Austria, between 2006 and 2009. Sarcoid disease was diagnosed by clinical examination and bovine papillomavirus types 1 and 2 from intact skin and tumour tissue. As nine horses had more than one lesion, a total of 47 sarcoids were treated by daily topical application of aciclovir 5 per cent cream for a period of two to six months; in four horses, surgical tumour ablation was performed before treatment. Disease parameters, including the tumour type, number, location and size, were recorded before and after aciclovir therapy. All 47 (100 per cent) of the sarcoids responded to treatment, with complete tumour regression observed for 32 (68 per cent) lesions and no recurrences reported thus far. Incomplete resolution was observed for 15 (32 per cent) lesions, probably due to their thickness. Aciclovir is proposed to be routinely used for the treatment of mild-type sarcoids and as an adjuvant therapeutic agent in combination with surgery.

Equus caballus papillomavirus-2 (EcPV-2): an infectious cause for equine genital cancer?

REASONS FOR PERFORMING STUDY: The aetiology of genital squamous cell carcinoma (SCC) in horses remains unknown, but the similarity to the disease in man, for which papillomavirus infection has been shown to be a causal factor, requires to be investigated in horses. HYPOTHESIS: One or more novel papillomaviruses cause equine genital SCC and its associated premalignant lesions. METHODS: DNA was extracted from samples of equine genital SCC and performed rolling circle amplification, in order to identify closed circular DNA viral genomes within the samples. The amplified DNA was subcloned and sequenced and the DNA sequence compared to that of other papillomavirus genomes. Using PCR primers developed from these genomic DNA sequences, studies were then carried out in order to identify the frequency at which the viral DNA could be identified in equine genital cancer samples from horses in both the UK, Australia and Austria. Finally, in situ hybridisation using specific probes developed from this DNA sequence were used to confirm the presence of the viral RNA sequences in the neoplastic cells in these lesions. RESULTS: The full length genome of a novel papillomavirus species was characterised from the equine genital SCC tissue and termed Equus caballus papillomavirus-2 (EcPV-2). Viral DNA and RNA was identified in the genital tumour samples, but not in the adjacent histologically normal tissue. EcPV-2 DNA could not be identified in equine ocular or nasal carcinomas or within the scrotal skin or in most smegma samples obtained from tumour-free horses. Sequencing of amplicons, generated from the archived equine genital tumours, identified variations within E1 and E6 on DNA and predicted protein level. CONCLUSIONS: A novel papillomavirus, EcPV-2, is likely to play a causal role in the pathogenesis of equine genital epithelial tumours. POTENTIAL RELEVANCE: Identification of a papillomavirus causal for genital carcinomas in horses may lead to development of a vaccine that could be used to prevent this serious disease in horses. This would be analogous to man, where vaccination against oncogenic papillomavirus species is currently being used to help prevent cervical cancer.