An alphaherpesvirus has been incriminated recently in the etiology of green turtle fibropapilloma (GTFP). Since the study of this naturally occurring model of presumed virus-induced tumorigenesis may provide insights into the cause and pathogenesis of HIV-associated malignancies and other human cancers, we have continued our effort to characterize putative candidate viruses. Thus, to further clarify the role of this newfound green turtle herpesvirus (GTHV) in the pathogenesis of this slow-growing tumor, various normal-appearing tissues and organs, including skin, eye, brain, heart, liver, spleen, intestine, lung, kidney, nerve, gonad, tongue, gall bladder, urinary bladder, thyroid and peripheral blood mononuclear cells (PBMC) and tumor tissues, from 19 green turtles (Chelonia mydas) with GTFP, and tissues from three turtles without GTFP, collected during 1997 to 1999 in the Hawaiian Islands, were tested for GTHV sequences by nested polymerase chain reaction (PCR), using GTHV-specific oligonucleotide primers. GTHV sequences were detected in all tumors (51/51) and most nontumor

tissues (133/167) of affected turtles (Figure 5). By contrast, such sequences were undetectable in tissues (0/28) of three non-tumored turtles. Analysis of GTHV sequences detected in different tissues and tumors revealed a low degree of genetic diversity (<1%). The uniform presence of this newfound herpesvirus in tumor tissues of affected green turtles, as well as the ability to detect such sequences in cell lines derived from tumor tissues, and its complete absence in tissues of non-tumored turtles argues for an etiologic role of GTHV in GTFP. In further support, herpesvirus-like particles have recently been detected in a cell line derived from tumor tissue (Figure 6). That said, the mechanism by which this alphaherpesvirus produces fibropapilloma, and the mode of transmission are unclear.

Figure 5. Detection of green turtle herpesvirus