Characterization of an iridovirus from the cultured pig frog Rana grylio with lethal syndrome

Abstract

Three virus isolates, RGV-9506, RGV-9807 and RGV-9808, were obtained from cultured pig frogs Rana grylio undergoing lethal infections. Previously, the first isolate, RGV-9506, was shown to be an iridovirus based on ultrastructural and morphological studies. In the present study, the original isolate, along with 2 recent ones, were more extensively characterized by experimental infection studies, histopathology, electron microscopy, serological reactivity, gel electrophoresis of viral polypeptides and DNA restriction fragments, PCR amplification, and nucleic acid sequence analysis of the major capsid protein (MCP) gene. The 3 isolates were shown to be identical to each other, and very similar to FV3, the type species of the genus Ranavirus (family Iridoviridae). These results suggest that RGV should be considered a strain of FV3, and indicate that FV3-like iridoviruses are capable of causing widespread, severe disease among cultured frogs. KEY WORDS: Rana grylio · Iridovirus · FV3 · Ranavirus · Viral disease Resale or republication not permitted without written consent of the publisherDis Aquat Org 48: [27][28][29][30][31][32][33][34][35][36] 2001 atic, and renal hematopoietic tissues. Moreover, although infection of redfin perch leads to high levels of mortality, EHNV infects other fish species with varying results (Langdon et al. 1986). In another example, localized die-offs of tiger salamanders Ambystoma tigrinum and largemouth bass Micropterus salmoides in North America have been linked to the presence of novel iridoviruses (Plumb et al. 1996, Jancovich et al. 1997, Bollinger et al. 1999. Finally, iridoviruses can infect not only different species within the same taxonomic class, but the same virus can infect animals from different classes (Mao et al. 1999a). Thus, an iridovirus isolated from the ornate burrowing frog Bohle iridovirus has been shown to cause mortality in barramundi fish following experimental infections (Moody & Owens 1994). The above observations indicate that iridoviruses infecting aquatic animals enjoy a worldwide distribution and are increasingly associated with serious disease (Ahne et al. 1997.Although some aspects of iridovirus biology have been examined (Willis et al. 1985, Hedrick et al. 1992, Zupanovic et al. 1998a,b, Bollinger et al. 1999, Mao et al. 1999a, additional work is needed to understand the ecology, epidemiology, and pathogenicity of iridovirus-host interaction. In this study, 3 RGV isolates linked to severe disease in cultured frogs were characterized by experimental infection, histopathology, electron microscopy, serological cross reactivity, gel electrophoresis of virion polypeptides and DNA restriction fragments, PCR amplification, and sequence analysis of the major capsid protein (MCP) gene. We found that the 3 isolates were essentially identical to each other and closely related to FV3. In view of this, it is likely that RGV is a strain of FV3. MATERIALS AND METHODSPreparation of RGV isolates. RGV isolates were prepared from tissues (liver, kidney and s...

Mitochondrion-mediated apoptosis induced by Rana grylio virus infection in fish cells

“…Apoptosis of fish cells can be also triggered by virus infection [14][15][16], but systematic studies on mitochondrial dynamics and the molecular mechanisms are very limited. In our previous studies, an iridovirus isolated from the cultured pig frog (Rana grylio), which is called Rana grylio virus (RGV), has been characterized [17], and a similar apoptotic process has been observed in RGV infected fish cells [18]. Electron microscopic observation displayed large clusters of mitochondria around the viromatrix in the infected cells [18].…”

Xenopus Laevis: A Possible Vector of Ranavirus Infection?

“…Ranaviruses (Iridoviridae) are becoming increasingly associated with diseases in wild and cultured fishes, frogs, salamanders, and reptiles (Cunningham et al, 1996;Zupanovic et al, 1998;Hyatt et al, 2000;Zhang et al, 2001;Chinchar, 2002;De Voe et al, 2004;Pearman et al, 2004;Greer et al, 2005). Frog virus 3 (FV3), the best-characterized member and type species of the Ranavirus genus, is a large (165-169 nm) double-stranded DNA icosahedral virus that was originally isolated from the North American leopard frog, Rana pipiens (Chinchar, 2002).…”

Cloning, expression and subcellular distribution of a Rana grylio virus late gene encoding ERV1 homologue

“…Propagation of RGV and isolation of the virus genomic DNA were performed as described previously [3]. Epithelioma papulosum cyprini (EPC) cell and Grass carp ovary (GCO) cells were maintained in TC199 medium supplemented with 10% fetal bovine serum (FBS) at 25°C.…”

“…RGV is a large DNA virus and is closely related to frog virus 3 (FV3), the type species of genus Ranavirus (family Iridoviridae) [2][3][4]. Iridoviruses display a complex gene regulation strategy in which genes are expressed in three main temporal stages: immediate early (IE) genes, early (E) genes and late (L) genes, which can be defined experimentally by using DNA replication and protein synthesis inhibitors [5][6][7][8].…”