Localization of Bovine papillomavirus in equine sarcoids and inflammatory skin conditions of horses using laser microdissection and two forms of DNA amplification

Abstract

Abstract. Equine sarcoids are the most common tumor of horses. Bovine papillomavirus (BPV) has been suggested as the cause of sarcoids. Studies have shown that BPV is present in swabs or biopsies from nonsarcoid-bearing equine skin. Skin biopsies from a variety of different conditions and normal skin from horses with no reported history of sarcoids were examined by polymerase chain reaction (PCR) for the presence of BPV, which was found in all different types of skin conditions as well as normal skin. Forty-one out of 86 skin biopsies from horses without sarcoids were found to contain BPV DNA. Laser microdissection, followed by DNA amplification through both PCR and isothermal loop-mediated amplification, was performed on these 41 biopsies and on 70 additional BPV-positive sarcoid biopsies to localize the virus. Location of BPV DNA was different between sarcoid and nonsarcoid groups. Nonsarcoid skin biopsies were more likely to have BPV within intact or inflamed epidermis than sarcoids (P = 0.016 and P = 0.007, respectively). Areas of inflammation within the dermis and epidermis were more likely to contain BPV than in noninflamed areas (P = 0.008 and P = 0.009, respectively). Bovine papillomavirus was also found in the epidermis of all types of sarcoids examined, more frequently in occult sarcoids than in fibroblastic and nodular types (P = 0.03 and P = 0.01, respectively). Results suggest that BPV is commonly found in normal and inflamed equine skin, and it is likely an important predisposing factor in the development of sarcoids.

Localization of Bovine Papillomavirus Nucleic Acid in Equine Sarcoids

“…1,19 Further work is necessary to understand how and when these events of the viral life cycle occur and their relationship to sarcoid development and/or maintenance. We propose, as have others, 8,37 that early in sarcoid development, there could be an early viral infection in the adnexa or surface epithelium that is undetectable later in the development of the tumor.…”

“…In these studies, BPV DNA was detected not only at high frequencies in the dermal tissue (fibroblasts), as we saw with ISH, but also, less prominently, in the epidermis. 8,11,37 Similarly, we specifically visualized BPV DNA in the sebocytes, hair follicle epithelium, and rarely epidermal cells. Detection in sebocytes has also been reported in related viruses, including Bandicoot papillomatosis carcinomatosis virus type 1, 7 human papillomaviruses, 16 and Micromys minutus papillomavirus.…”

“…single primer pair was used that amplifies a 244-bp (BPV1) and 248-bp (BPV2) product spanning a portion of the E2 gene, an intergenic region, and the E5 gene. 37 The full protocol is provided in the Supplemental Materials. To detect equine papillomavirus, EcPV1 (AF498323.1) and EcPV2 (EU503122.1) specific primers were designed to amplify the E1 region of the genome.…”

“…The most recent focus is on studies targeting examination of BPV specifically in the epithelium, where productive infections occur in natural hosts. Laser microdissection and PCR studies have identified BPV DNA in the epidermis in a subset of equine sarcoids, 8,11,37 although at a lower rate than in the dermis 8,37 and at a lower copy number. 8,11 To complement these studies and visualize the location of viral nucleic acid within equine sarcoids, we developed a sensitive colorimetric in situ hybridization (ISH) assay that allows single-molecule visualization by hybridization-based amplification.…”

Bovine papillomavirus: opening new trends for comparative pathology

“…However, in contrast to E2-TA, E2-TR activated transcription from a promoter-proximal position and partially inhibited P89, while E8E2 led to complete repression. In a recent study, viral DNA has also been found in the epidermis of horses with inflammatory skin conditions and in the epidermis overlying sarcoids, especially in early-stage, "occult", flat lesions [53]. Results suggest that a transient, productive infection may take place in the overlying epidermis during the early phases of sarcoid development [54][55].…”