Three Closely Related Herpesviruses Are Associated with Fibropapillomatosis in Marine Turtles

Abstract

Green turtle fibropapillomatosis is a neoplastic disease of increasingly significant threat to the survivability of this species. Degenerate PCR primers that target highly conserved regions of genes encoding herpesvirus DNA polymerases were used to amplify a DNA sequence from fibropapillomas and fibromas from Hawaiian and Florida green turtles. All of the tumors tested (n = 23) were found to harbor viral DNA, whereas no viral DNA was detected in skin biopsies from tumor-negative turtles. The tissue distribution of the green turtle herpesvirus appears to be generally limited to tumors where viral DNA was found to accumulate at approximately two to five copies per cell and is occasionally detected, only by PCR, in some tissues normally associated with tumor development. In addition, herpesviral DNA was detected in fibropapillomas from two loggerhead and four olive ridley turtles. Nucleotide sequencing of a 483-bp fragment of the turtle herpesvirus DNA polymerase gene determined that the Florida green turtle and loggerhead turtle sequences are identical and differ from the Hawaiian green turtle sequence by five nucleotide changes, which results in two amino acid substitutions. The olive ridley sequence differs from the Florida and Hawaiian green turtle sequences by 15 and 16 nucleotide changes, respectively, resulting in four amino acid substitutions, three of which are unique to the olive ridley sequence. Our data suggest that these closely related turtle herpesviruses are intimately involved in the genesis of fibropapillomatosis.

Polymerase Chain Reaction(PCR) for the Detection of Herpesvirus in Tortoises.

“…But the nucleotide sequences showed little homogeneity when compared with DNA databases using a BLAST2.0.7 program [1]. The nucleotide sequences obtained in the present study also showed only 57% homogeneity with those reported in the cases of green turtle fibropapillomatosis [10]. This fact suggests that the sequence determined in the present study may be ascribed to a new type of tortoise herpesviral DNA, which most likely belongs to the alpha subfamilies of herpesviridae [11], judging from its amino acid sequence.…”

“…In the present study, analysis of the nucleotide sequence of the tortoise herpesviral DNA showed that the 230-bp sequence obtained in our study differed from that in a herpesvirus found in green turtle fibropapillomatosis [10], suggesting the possibility of a new type of tortoise herpesviral DNA, most likely belonging to the alpha subfamilies of herpesviridae [11], as mentioned above. The PCR method using a consensus primer may thus be another useful method for identifying herpesviral infections in tortoises, and especially effective in the diagnosis of early or latent infections in living tortoises.…”

“…Detection of intranuclear inclusion bodies by light microscopy and of viral particles by electron microscopy [7,12] have been the dominant methods used for the diagnosis of herpesviral infections in chelonians. Recently herpesviruses have been isolated from pharyngeal swabs in tortoises [8], and herpesviral DNAs extracted from tumor tissues in marine turtles have been amplified by PCR [10]. Virus isolation is another important method for the diagnosis of herpesviral infections in living chelonians, but usually it is difficult to obtain fresh materials for virus isolation, and to maintain the necessary cultured cell populations.…”

“…VanDevanter et al concluded that the consensus primer method targeted at herpesviral DNA polymerase may be useful for the detection of known herpesviruses using clinical samples. Quackenbush et al [10], using the same kind of primers as those of VanDevanter et al [14], amplified herpesviral DNA in tissue from fibropapillomatosis lesions in green turtles. Analysis of the nucleotide sequence showed that the 237-bp segment obtained was most similar to the DNA polymerases of bovine herpesvirus type 1 (BHV-1) and pseudorabies virus (PRV).…”

Establishment and characterization of 13 cell lines from a green turtle (Chelonia mydas) with fibropapillomas

“…The disease, which disrupts the daily activities of affected animals, is characterized by the formation of lobulated fibrous tumors, frequently around the neck, eye, mouth, flipper and/or oral cavity, and occasionally within visceral organs, such as lung, kidney, and heart. Recent studies have implicated viruses, notably a herpesvirus and retrovirus, as the potential cause of green turtle fibropapilloma (GTFP) (1,6,13,25). However, to date, no virus has been isolated in cell culture, and the pathogenetic role of herpesviruses or retroviruses has not been established (11).…”