Objective—To determine expression of a transforming
gene (E5) of bovine papillomavirus in sarcoids,
other tumors, and normal skin samples collected
from horses with and without sarcoids.
Sample Population—23 sarcoids and 6 samples of
normal skin obtained from 16 horses with sarcoids, 2
samples of normal skin and 2 papillomas obtained
from horses without sarcoids, and 1 papilloma
obtained from a cow.
Procedure—Protein was extracted from tissue samples
collected from horses and incubated with
agarose beads covalently coupled to Staphylococcus
aureus protein A and an anti-E5 polyclonal antibody.
Following incubation, proteins were eluted from the
beads and electrophoresed on a 14% polyacrylamide
gel and transferred to a polyvinylidene difluoride
membrane. The E5 protein was detected by use of
western blot analysis, using a chemiluminescence
Results—All 23 sarcoids had positive results for
expression of E5 protein. Quantity of viral protein
appeared to vary among sarcoids. All other tissues
examined had negative results for E5 protein. Highest
expression for E5 protein was observed in biologically
aggressive fibroblastic variants of sarcoids, compared
with expression in quiescent tumors.
Conclusions and Clinical Relevance—This study
documented that activation and expression of the E5
gene is evident in sarcoids obtained from horses.
These data support the conclusion that infection with
bovine papillomavirus is important in the initiation or
progression of sarcoids in horses. Treatment strategies
designed to increase immune recognition of
virally infected cells are warranted. (Am J Vet Res