• 한국어병학회지
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• 제22권2호
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• pp.173-177
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• 2009

Lymphocystis disease virus (LCDV) was detected from olive flounder Paralichthys olivaceus, painted glass fish Chanda baculis, gourami Trichogaster leeri and rockfish Sebastes schlegeli, and proteins of the viruses were compared. The major capsid protein (MCP) gene-specific primer sets successfully amplified approximately 1300 bp nucleotides from the olive flounder and 600 bp nucleotides from painted glass fish, gourami and rockfish isolates, respectively. In western blotting analysis using anti-LCDV mouse polyclonal serum, major antigenic proteins had 21, 26, 45, 50, 80, 110 and 120 kDa in olive flounder, 26, 47 and 80 kDa in painted glass fish, 26, 46, 80 and 92 kDa in gourami, 26, 44, 49, 80 and 105 in rockfish, respectively. All the marine and freshwater isolates showed only common antigens of approximately 26 kDa and 80 kDa. These results suggest that antigenic protein profiles of LCDVs may vary depending upon fish species.

• 한국어병학회지
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• 제23권3호
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• pp.273-280
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• 2010

To determine whether rock bream Oplegnathus fasciatus can be protected from rock bream iridovirus (RBIV) infection by intramuscular injection of long double-stranded RNAs (dsRNAs), we compared protective effect of virus-specific dsRNAs corresponding to major capsid protein (MCP), ORF 084, ORF 086 genes, and virus non-specific green fluorescent protein (GFP) gene. Furthermore, to determine whether the non-specific type I interferon (IFN) response was associated with protective effect, we estimated the activation of type I IFN response in fish using expression level of IFN inducible Mx gene as a marker. As a result, mortality of fish injected with dsRNAs and challenged with RBIV was delayed for a few days when comparing with PBS injected control group. However, virus-specific dsRNA injected groups exhibited no significant differences in survival period when compared to the GFP dsRNA injected group. Semi-quantitative analysis indicated that the degree of antiviral response via type I IFN response is supposedly equal among dsRNA injected fish. These results suggest that type I IFN response rather than sequence-specific RNA interference might involve in the lengthened survival period of fish injected with virus-specific dsRNAs.

• 수산해양교육연구
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• 제27권4호
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• pp.1184-1193
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• 2015

Monitoring for megalocytivirus infection was conducted for ten months from March to December in 2013 in 15 aquatic farms culturing, red sea bream, rock bream, rock fish and black sea bream around Tongyoung coastal area in Korea, to assess spatial and temporal variability of detection prevalence, and to explore possible links with seawater temperature. In nested-PCR targeted major capsid protein (MCP) gene, asymptomatic megalocytivirus infection was detected in the externally healthy farmed fish with a significant prevalence in range from 0 to 58.3% for ten months. Higher prevalence of megalocytivirus (46.7% - 57.1%) was observed in high water temperature season from September to November than that in other months with lower prevalence of 0.0% to 20.0%. Even though an acute infection of megalocytivirus was occurred in rock bream (positive in the first PCR) with high mortality in one of fifteen farms, there was no expansion or transmission of the disease to the rock fish and red sea bream culturing in net cage just proximal to the rock bream cage in which disease outbreaked. Nucleotide sequence analysis of the cloned MCP gene isolated asymptomatically infected rock fish revealed that the megalocytivirus in this study was clustered together with the rock bream iridovirus (RBIV) under the subgroup II of the genus megalocytivirus (Iridoviridae), which is known to be the major megalocytivirus strain in Korea. The typical histopathological signs were not found in the spleen of rock fish asymptomatically infected by megalocytivirus. Experimental infection of rock bream with the spleen homogenate of the rock fish infected asymptomatically did not induce any mortality unlike the homogenate of infected rock bream with hih mortlity. However, these results may suggest that the asymptomatic infection of megalocytivirus in other fish species can be a potential risk threatening aquaculture industries as a transmission factor of megalocytivirus to susceptible fish species, especially rock bream.

• 한국어병학회지
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• 제34권2호
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• pp.149-159
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• 2021

Genus Megalocytivirus cause red sea bream iridoviral disease (RSIVD) and scale drop disease (SDD). Based on the phylogeny of the major capsid protein (MCP) and adenosine triphosphatase (ATPase) genes, megalocytiviruses except for SDD virus (SDDV) could be three different genotypes, red sea bream iridovirus (RSIV), infectious spleen and kidney necrosis (ISKNV), and turbot reddish body iridovirus (TRBIV). In this study, primary cells derived from the caudal fin of rock bream (Oplegnathus fasciatus) grew at 25℃ in Leibovitz's medium supplemented with 10% (v/v) fetal bovine serum and primocin (100 ㎍/mL). Rock bream fin (RBF) cells exhibited susceptibility to infections by different genotypes of megalocytiviruses (RSIV, ISKNV and TRBIV) with the appearance of cytopathic effects with an increase in the viral genome copy number. Furthermore, compared to grunt fin (GF) cells, even though 10 times lower number of RSIV genome copies were inoculated in RBF cells, viral genome copy number produced on RBF cells were 44 times higher than that of GF cells at 7 d post-inoculation. As the isolated RBF cells are sensitive to different genotypes of megalocytiviruses (RSIV, ISKNV and TRBIV), they can be used for future studies regarding in vitro viral infection and subsequent diagnosis.

• Fisheries and Aquatic Sciences
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• 제24권11호
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• pp.351-359
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• 2021

The red sea bream iridovirus (RSIV) belonging to genus Megalocytivirus is responsible for red sea bream iridoviral disease (RSIVD) in marine and freshwater fishes. Although several diagnostic assays for RSIV have been developed, diagnostic sensitivity (DSe) and specificity (DSp) of real-time polymerase chain reaction (PCR) assays are not yet evaluated. In this study, we developed a TaqMan probe-based real-time PCR method and evaluated its DSe and DSp. To detect RSIV, the probe and primers were designed based on consensus sequences of the major capsid protein (MCP) genes from megalocytiviruses including RSIV, infectious spleen and kidney necrosis virus (ISKNV), and turbot reddish body iridovirus (TRBIV). The probe and primers were shown to be specific for RSIV, ISKNV, and TRBIV-types megalocytiviruses. A 95% limit of detection (LOD_95%) was determined to be 5.3 viral genome copies/µL of plasmid DNA containing the MCP gene from RSIV. The DSe and DSp of the developed real-time PCR assay for field samples (n = 112) were compared with those of conventional PCR assays and found to be 100% and 95.2%, respectively. The quantitative results for SYBR Green and TaqMan probe-based real-time PCR were not significantly different. The TaqMan probe-based real-time PCR assay for RSIV may be used as an appropriate diagnostic tool for qualitative and quantitative analysis.

• 한국어병학회지
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• 제37권1호
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• pp.25-36
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• 2024

In this study, we analyzed the phylogenetic classification, epitope prediction, and pathogenicity of red sea bream iridovirus (RSIV) isolated from rock bream between 2019 and 2023. Phylogenetics based on genes encoding MCP and ATPase indicated that all five RSIV isolates belonged to RSIV subtype II. The deduced amino acid sequence of the MCP for the amplicons (1362 bp) obtained from RSIV isolates had a length of 453 amino acids. Among these, the amino acid sequences of the RSIV-19, 21, 22, and 23 isolates showed 100% identity, while the RSIV-20 isolate showed 99.78% identity with one residue difference at position 306. As a result of antigenicity analysis based on amino acid sequence, the antigenicity score of the RSIV-20 isolate was 0.6386 and the other RSIV isolates were 0.6365. Additionally, the prediction of their antigenic determinants resulted in a total of 17 identical antigenic plots. When each RSIV was inoculated into rock bream, no significant differences were observed with 100% cumulative mortality in all groups. This study provides data on the potential for genetic variation of RSIV isolated in the same marine area over the past five years, and the antigenicity and pathogenicity results of each isolate are expected to be useful information for selecting future vaccine strains.