Molecular characterization of iridoviruses isolated from sympatric amphibians and fish

Iridoviruses infect invertebrates (primarily insects and crustaceans) and e ctothermic vertebrates (fish, amphibians, and reptiles). Identical, or near ly identical viruses, have been isolated from different animals within the same taxonomic class, indicating that infection by a given virus is not lim ited to a single species. Although inter-class infections have been documen ted following experimental infection with vertebrate iridoviruses, it is no t clear whether such infections occur in nature. Here we report the isolati on of apparently identical iridoviruses from wild sympatric fish (the three spine stickleback, Gasterostelus aculeatus) and amphibians (the red-legged frog, Rana aurora). Viruses isolated from sticklebacks (stickleback virus, SBV) and from a red-legged frog tadpole (tadpole virus 2, TV2) replicated i n fathead minnow (FHM) cells and synthesized proteins which co-migrated wit h those of frog virus 3 (FV3). Following restriction endonuclease digestion of viral DNA with Hind III and Xba I, gel analysis showed that the profile s of SBV and TV2 were identical to each other and distinct from FV3. Using oligonucleotide primers specific for a highly conserved region of the irido virus major capsid protein, an similar to 500 nucleotide DNA fragment was a mplified from SBV and TV2. Sequence analysis showed that within this 500 nu cleotide region SBV and TV2 were identical to each other and to FV3. Taken together these results provide the first evidence that iridoviruses natural ly infect animals belonging to different taxonomic classes, and strengthen the suggestion that fish may serve as a reservoir for amphibian viruses or vice versa. (C) 1999 Elsevier Science B.V. All rights reserved.