Expression of a transforming gene (E5) of bovine papillomavirus in sarcoids obtained from horses

Objective To determine expression of a transforming gene (E5) of bovine pap illomavirus in sarcoids, other tumors, and normal skin samples collected fr om 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 f rom horses without sarcoids, and 1 papilloma obtained from a cow. Procedure-Protein was extracted from tissue samples collected from horses a nd incubated with agarose beads covalently coupled to Staphylococcus aureus protein A and an anti-E5 polyclonal antibody. Following incubation, protei ns were eluted from the beads and electrophoresed on a 14% polyacrylamide g el and transferred to a polyvinylidene difluoride membrane. The E5 protein was detected by use of western blot analysis, using a chemiluminescence det ection system. Results-All 23 sarcoids had positive results for expression of E5 protein. Quantity of viral protein appeared to vary among sarcoids. All other tissue s examined had negative results for E5 protein. Highest expression for E5 p rotein was observed in biologically aggressive fibroblastic variants of sar coids, compared with expression in quiescent tumors. Conclusions and Clinical Relevance This study documented that activation an d expression of the E5 gene is evident in sarcoids obtained from horses. Th ese data support the conclusion that infection with bovine papillomavirus i s important in the initiation or progression of sarcoids in horses. Treatme nt strategies designed to increase immune recognition of virally infected c ells are warranted.