Amphibian and Piscine Iridoviruses Proposal for Nomenclature and Taxonomy Based on Molecular and Biological Properties

Abstract

We have compared a number of properties of the well-characterized iridovirus, frog virus 3, with two other iridoviruses from amphibia, bullfrog edema virus and Lucké triturus virus, and with a piscine iridovirus, goldfish virus (GFV), to provide information for developing taxonomic classification of these viruses and establishing their ecological niche. Purified virions had similar size and shape (icosahedral) for each virus, and the genomic DNAs of each virus were methylated by a virus-induced DNA methyltransferase. The three amphibian viruses replicated equally well in fish (FHM), hamster (BHK), and human (WI-38) cell monolayer with identical cytopathology, while GFV failed to replicate in these cell lines. However, GFV replicated albeit at a slow rate, in a goldfish cell line; there was no detectable replication by the amphibian viruses in these cells. The amphibian iridoviruses had virtually similar DNA sequences, while those of GFV were markedly different. Analyses of virus-induced polypeptides in infected cells corroborated the DNA analyses; the polypeptides of the amphibian viruses were similar and distinct from those of the fish virus. Nongenetic reactivation could only be accomplished between the three amphibian viruses but not with the piscine virus. Based on these data, we suggest taxonomic and nomenclature designations of amphibian and piscine iridoviruses.