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...

This study determined whether cutaneous antibodies were present in excised skin explants of grass carp, Ctenopharyngodon idella, immune to Scophthalmus maximus rhabdovirus (SMRV). Culture fluid from immune skin explants were assayed by indirect enzyme-linked immunosorbent assay (iELISA), Western blot, indirect immunofluorescent assay (IFA) and flow cytometry (FCM). iELISA showed that cutaneous antibody titres were much lower (1:12) than antiserum titres (1:1458) from intraperitoneally immunized grass carp. The phosphoprotein and matrix protein antigens of purified SMRV proteins were recognized by cutaneous antibodies from skin culture fluid using Western blot. The skin culture fluid produced staining signals in viral assembly sites and cytoplasm of SMRV-infected epithelioma papulosum cyprini (EPC) cells by IFA. FCM showed that 4.39% SMRV-infected EPC cells were detected, while non-specific reaction was seen in 2% of control cells. This is the first description of cutaneous antibodies against SMRV in grass carp.