Bovine papillomavirus DNA can be detected in keratinocytes of equine sarcoid tumors.

The study reports a potential process of Bovine papillomavirus (BPV) infection in horses, where the virus first infects keratinocytes (skin cells) before transitioning to deeper fibroblasts (cells that make the structural framework for tissues). The infection eventually leads to equine sarcoids, a common type of skin tumor in horses.

Research Context and Aim

• Bovine papillomavirus (BPV) 1 and 2 are associated with a skin tumor in horses called equine sarcoids. This condition is a significant concern in veterinary medicine.
• Previous research has found BPV DNA in fibroblasts, skin cells that provide the structural framework for tissues, but not keratinocytes, the primary type of cell found in the skin.
• However, this contrasts with behavior seen in normal equine skin latently infected with BPV, where infection leads to dysplastic epithelium without dermal changes – a characteristic of papillomavirus-induced lesions generally appearing in the epithelium.
• This study aimed to describe the characteristics of different stages of sarcoid development and to investigate if BPV can infect the skin’s outer cells.

Methodology and Findings

• Researchers used real-time PCR on laser-micro-dissected keratinocytes and fibroblasts to explore whether BPV could infect the skin’s epidermal cells.
• They found that normal skin samples with latent BPV infections showed signs of dysplasia in the epithelium, similar to early-stage sarcoids.
• BPV DNA was found in keratinocytes in 40% of samples with abnormal epithelial changes, while advanced sarcoids had BPV DNA only in fibroblasts.

Interpretation of Results

• The consistent presence of BPV DNA in keratinocytes suggests a previously unknown method of BPV infection, where the virus first infects skin cells before migrating towards the dermis (the second layer of skin) and infecting fibroblasts.
• This progression could explain the eventual transformation of fibroblasts into their final mutated form, which initiates sarcoid development.
• The researchers also found an instance where a skin lesion harbored a BPV-1 infection in the dermis and a BPV-2 infection in the epidermis, suggesting that horses can have more than one type of BPV infection simultaneously.

Significance of the Study

• This research gives valuable insights into how BPV infections might develop in horses.
• Understanding the progression of BPV infections can potentially guide the development of treatments for equine sarcoids, improving veterinary care for horses infected with BPV.
• The discovery also broadens the understanding of how BPV behaves and might influence further studies on other papillomavirus-induced conditions.