The serological detection of Bovine papillomavirus’s E5 oncoprotein antibodies in horses

Abstract

Equine sarcoids (ES) are known globally as the most frequent skin tumour affecting horses. These tumours affect the horse’s monetary value, they can affect the horse’s welfare and can be difficult and expensive to treat. Bovine papillomavirus (BPV) is considered to be the aetiological agent of this tumour, as BPV 1, 2 and 13 have been detected in ES. This is the only known natural cross species infection by a papillomavirus. The BPV genome can be divided into two coding regions: The early region E which encodes the transforming proteins E5, E6 and E7 as well as the replication and transcription regulatory proteins E1 and E2 and the late region encoding the structural proteins of the virus L1 and L2. The E5 oncoprotein is believed to downregulate MHC 1 and as a result, escapes an immune reaction with affecting the cells cycle and eventually allows the viral affected cells to proliferate into ES. We have constructed an ELISA test by utilising the C terminal peptide of the E5 oncoprotein and explored the possibility of IgG antibodies existence in horses to the E5 oncoprotein. For this study we have examined 136 horses, some showing ES lesions (80 horses) and some without ES lesions (56 horses). By using our ELISA test, we have shown that antibodies to the E5 oncoprotein are in fact present and that from a certain level seem to be found only in ES positive horses. Therefore, proving that an immune response to this protein can be expected.