Abstract

Marine Turtle Fibropapillomatosis (FP) is an infectious tumor disease, affecting marine turtles. The prevalence of FP has risen from isolated cases in a single turtle species (Chelonia mydas), to epidemic proportions worldwide. The disease is lethal in most of the affected animals, and poses significant threat to endangered turtle species.

The etiology of FP is not known. Transmission studies with tumor extracts implicate an infectious, sub-cellular agent, most likely a virus. Using molecular and electron microscopic techniques, an alpha-herpes virus was reported to be associated with the tumors, but causality has not been demonstrated.

Representational Difference Analysis (RDA) is a subtractive technique used to detect differences in DNA sequences between tumor and normal tissues that allow the discovery of new pathogens. In this study, we applied RDA to screen for viral sequences specific for tumor tissue. We have identified three virus-related sequences in FP tumors, two from the herpes virus family, and one from the retrovirus family. The herpes viral sequences show significant homologies to a terminase and to the major capsid protein of members of the alpha-herpes virus subfamily. Our data demonstrate the tumor-specificity of the herpes viral DNA. The retrovirus-like sequence encodes a reverse transcriptase with tumor-specific RNA expression. In situ studies and subsequent analysis of differential gene expression levels by subtracting mRNA of tumor tissue from mRNA of normal tissue will be used to suggest the cellular mechanisms of tumor genesis. To the best of our knowledge, this is the first time that RDA has been applied to identify infectious agents in a wildlife disease.

Acknowledgements

This work was supported by NMFS, Honolulu Laboratory and by Wildlife Trust, NY.