Intralesional bovine papillomavirus DNA loads reflect severity of equine sarcoid disease.

The research paper investigates the relationship between viral DNA concentration of bovine papillomaviruses (BPV) in equine sarcoid tumors and severity of the disease in horses. Findings reveal a correlation between higher viral loads and greater disease severity, thereby indicating a possible marker for determining the severity of the disease and for developing treatment strategies.

Overview

The study focuses on equine sarcoid disease, a kind of non-metastasising but locally aggressive skin tumor that’s the most common neoplasm in equids (horses, donkeys, and zebras). Infection by bovine papillomaviruses types 1 and 2 (BPV-1, BPV-2) is a significant cause of the disease, but the relationship between the amount of virus present in the lesion and the severity of the disease has not been established.

Methodology

• The severity of the disease in 37 horses and one donkey was determined by examining tumour growth rates, the number of lesions, and the type of tumor they had.
• Viral load was estimated via quantitative real-time PCR (qPCR) of four genes (E2, E5, L1 and L2) in the BPV-1/-2 genome from one randomly selected lesion per horse.
• The measured viral load was then compared to the severity of the disease.

Results

• The qPCR indicated a range of concentrations of Viral DNA, from 0 to 556 copies per tumor cell.
• In horses with single, slowly growing tumors or multiple mild lesions, 15 out of 16 showed a viral load of up to 1.4 copies per cell.
• In contrast, all equids (22/22) with quickly growing and multiple aggressive sarcoids showed higher viral loads, between 3 and 569 copies per cell, irrespective of their clinical appearance.
• Similar findings were noted with qPCR testing against the other three genes (E5, L1 and L2).

Conclusions

The study concluded that there is a strong correlation between viral load in the lesion and the severity of equine sarcoid disease. It was also observed that tumors of the same clinical type carried variable virus load. Thus, while viral titre does not determine the clinical appearance, it can be a reliable marker for predicting disease severity. This information can also be used when creating a therapeutic strategy for controlling and treating the disease, potentially improving the prognosis for the affected equids.