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Evaluation of equine papillomas, aural plaques, and sarcoids for the presence of Equine papillomavirus DNA and Papillomavirus antigen.

ABSTRACT: Immunohistochemical (IHC) testing and electron microscopy have implicated Papillomavirus (PV) as the etiologic agent for equine papillomas and aural plaques, but Equine papillomavirus (EPV) DNA has yet to be demonstrated in these lesions by polymerase chain reaction (PCR). The purpose of this study was to evaluate formalin-fixed, paraffin-embedded tissues from naturally occurring cases of equine papillomas, aural plaques, and sarcoids for the presence of EPV DNA by means of PCR and for the presence of PV antigen by means of IHC testing. We used EPV-specific primers that amplified a region of 384 base pairs (bp) spanning the E4 and L2 genes of the EPV genome and consensus PV primers that amplified a 102-bp region of the L1 gene. Group-specific PV structural antigens were detected with the use of a streptavidin-biotin-alkaline phosphatase IHC stain. With IHC testing, 23 of 38 papillomas, 4 of 9 aural plaques, and 0 of 10 sarcoids were positive for PV antigen; EPV DNA was found in 20 of the 38 papillomas and 1 of the 10 sarcoids but 0 of the 9 aural plaques. The consensus primers did not amplify novel PV DNA in any of the tissues. Nucleotide sequencing of viral DNA from 7 papillomas amplified with EPV-specific primers revealed DNA fragments that were 96% to 99% identical to known EPV sequences. Some samples had nucleotide substitutions in common, which suggests infection with related strains. Together, EPV DNA or PV antigen (or both) was demonstrated in 26 (68%) of the 38 equine papillomas. Although aural plaques contained PV antigen, they were negative for EPV DNA; therefore, we hypothesize that aural plaques contain a PV distinct from EPV.

SUBMITTER: Postey RC

PROVIDER: S-EPMC1635997 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND: Bovine papillomaviruses (BPVs) types 1 and 2 are the only known papillomaviruses able to jump the species. In fact, BPVs 1/2 induce neoplasia in their natural bovine host but infection is also associated to neoplastic skin lesions in equids termed sarcoids. The equine sarcoid is considered to be the most common equine cutaneous tumour worldwide for which no effective therapy is available. Very little is known about the molecular mechanisms underlying tumourigenesis, although genes contributing to sarcoid development have been identified. Several studies associate the development of cancer to the loss of function of a number of oncosuppressor genes. In this study the putative role of O6-methylguanine-DNA methyltrasferase (MGMT) was investigated for sarcoids. The expression of the oncosuppressor protein was assessed in normal and sarcoid cells and tissues. In addition, the DNA methylation profile was analysed to assess the role of epigenetic mechanism in regulation of MGMT expression. RESULTS: A group of 15 equine sarcoids and two primary sarcoid cell lines (fibroblasts) were analyzed for the expression of MGMT protein by immunohistochemistry, immunofluorescence and Western blotting techniques. The sarcoid cell line EqSO4b and the tumour samples showed a reduction or absence of MGMT expression. To investigate the causes of deregulated MGMT expression, ten samples were analyzed for the DNA methylation profile of the CpG island associated to the MGMT promoter. The analysis of 73 CpGs encompassing the region of interest showed in 1 out of 10 (10%) sarcoids a pronouncedly altered methylation profile when compared to the control epidermal sample. Similarily the EqSO4b cell line showed an altered MGMT methylation pattern in comparison to normal fibroblasts. CONCLUSION: As previously demonstrated for the oncosuppressor gene FHIT, analysis of MGMT expression in sarcoid tissues and a sarcoid-derived fibroblast cell line further suggests that oncosuppressor silencing may be also involved in BPV-induced equine tumours. Abnormal DNA methylation seems to be one of the possible molecular mechanisms involved in the alteration of MGMT expression. Further studies are required to address other basic molecular mechanisms involved in reduced MGMT expression. This study underlines the possible role of DNA methylation in oncosuppressor inactivation in equine sarcoids.

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Evaluation of equine papillomas, aural plaques, and sarcoids for the presence of Equine papillomavirus DNA and Papillomavirus antigen.

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