Bovine papillomavirus infection in equine sarcoids and in bovine bladder cancers.
Authors: Yuan Zhengqiang, Gallagher Alice, Gault Elizabeth A, Campo M Saveria, Nasir Lubna
Journal: Veterinary journal (London, England : 1997)
Summary
# Equine Sarcoids and Bovine Bladder Cancer: A Comparative Look at BPV Infection Bovine papillomavirus (BPV) drives tumour formation in two very different hosts—type 1 causes equine sarcoids whilst type 2 is implicated in bovine urinary bladder carcinomas—yet both infections share a curious feature: early viral proteins are expressed without producing infectious virions. Yuan and colleagues investigated whether the molecular mechanisms underlying these tumours might be similarly conserved by examining the physical form, quantity and genetic variability of BPV in both conditions. Using rolling circle amplification and real-time quantitative PCR, they demonstrated that both BPV-1 and BPV-2 persist as episomal double-stranded circular DNA in tumour tissue, with equine sarcoids harbouring substantially higher viral loads than bovine bladder cancers. Sequence analysis of the E5 open reading frame (which encodes proteins critical to transformation) revealed variation in BPV-1 but remarkable stability in BPV-2, though neither pattern correlated with viral DNA load in either tumour type. For equine practitioners, these findings suggest that sarcoid development may involve higher viral burden than previously recognised, whilst the genetic stability of BPV-2 contrasts intriguingly with BPV-1's variability—a distinction that may prove relevant to understanding resistance mechanisms and developing targeted interventions in the future.
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Practical Takeaways
- •Equine sarcoids harbour substantially more BPV-1 DNA than bovine bladder cancers harbour BPV-2, which may influence treatment approaches and viral shedding potential
- •The consistent lack of variation in BPV-2 E5 (unlike BPV-1) suggests different viral evolutionary pressures in cattle versus horses that may have implications for cross-species transmission risk
- •Understanding the episomal nature of BPV genomes in sarcoids supports investigation of therapies targeting viral DNA maintenance rather than integration
Key Findings
- •BPV-1 and BPV-2 genomes exist as episomal circular forms in both equine sarcoids and bovine bladder cancers
- •Equine sarcoids contained higher viral DNA loads compared to bovine bladder cancers
- •BPV-1 E5 ORF showed sequence variation while BPV-2 E5 ORF did not
- •E5 ORF variations had no apparent effect on viral DNA load in either tumour type