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

The article investigates the relationship between equine papillomavirus type 2 (EcPV2) infection and the development of squamous cell carcinoma (SCC) in horses, focusing on SCCs of the head. The study used various tests and analyses on a range of sample types, and the results point toward the potential for the integration of EcPV2 into the horse’s cellular structure.

Introduction and Methodology

• The researchers studied the connection between EcPV2 and SCC in horses, particularly focusing on SCC in the horse’s head (HSCC).
• They tested 15 HSCC DNA samples, scrutinizing them for EcPV2 indicators using several methods, including E6/E7, E2, and Long Control Region (LCR) PCR, a technique used to amplify particular DNA sequences.
• The physical presence of EcPV2 in HSCC, genital lesions, and smegma in horses with SCC was further investigated using EcPV2 immunocapture PCR (IC/PCR) and E6 versus E2 quantitative PCR (qPCR) to evaluate potential viral integration into horse cells.

Results and Discussion

• The analysis found that four out of the 15 tested HSCC contained EcPV2 DNA and housed identified or new genetic variants of E6, E7, E2, and LCR.
• Further examination showed that around 51% of the tested extracts appeared to harbour EcPV2 virions, indicating the presence of the virus.
• E6/E2 qPCR analyses of tumor DNA exposed varying counts of E2/E6 per cell, with quantities fluctuating vastly.
• They also discovered that the smegma samples that tested positive contained higher copy numbers of E2 and E6, leading them to believe that smegma could serve as a significant reservoir of EcPV2.
• However, viral DNA amounts were considerably lower in HSCCs compared to most genital tumor and smegma DNA specimens.
• In most samples, more E6 DNA than E2 was found, suggesting that integration of the virus into the host cell genome may occur, though this wasn’t statistically significant and needs further investigation.

Research Implications

• This study contributes to the growing body of evidence that EcPV2 infection may promote the occurrence of SCC in horses.
• The findings set the stage for continued research into the mechanism of EcPV2 integration into host cells and its broader implications for SCC development.
• The identification of smegma as a possible EcPV2 reservoir, if confirmed, could have implications for disease prevention and control strategies.