• Journal of fish pathology
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• v.19 no.3
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• pp.197-206
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• 2006

The distribution of iridoviruses in five freshwater ornamental fishes, pearl gourami (Trichogaster leeri), dwarf gourami (Colisa lalia), silver gourami (Trichogaster microlepis), blue gourami (Trichogaster trichopterus sumatranus) and freshwater angelfish (Pterophyllum scalare), imported from Singapore was examined in 2004 and 2005. The presence of iridoviruses in 56 sample groups was determined using PCR technique and showed PCR positive in 11 sample groups. The proportion of fish infected by iridovirus was differed depending upon species; 31.8% (7/22) for pearl gourami, 18.2% (2/11) for dwarf gourami, 16.7% (1/6) for blue gourami, 9.1% (1/11) for silver gourami and 0% (0/6) for angelfish. In quantitative comparison of viral DNAs isolated from infected tissues, the DNA concentration of iridovirus in pearl gourami was higher than that in dwarf gourami. Although pearl gourami infected naturally by iridovirus showed 100% mortality in keeping experiment for 3 weeks, only 57% of those was positive in PCR. In the comparison of nucleotide sequences of the PstⅠ fragment known as the most variable genomic region, both iridoviruses isolated from pearl gourami and dwarf gourami showed identity more than 99% with infectious spleen and kidney necrosis virus (ISKNV) isolated from mandarinfish (Siniperca chuatsi).

• Journal of Life Science
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• v.19 no.6
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• pp.720-727
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• 2009

Lyophilized powder (BP2FS) of soybeans fermented with Bacillus polyfermenticus KJS-2 (B. polyfermenticus KJS-2) exhibited in vitro antibacterial activities against eight pathogenic bacteria. BP2FS was used as a fodder additive for Oplegnathus fasciatus (0. fasciatus) culture. One group (UFD) of O. fasciatus was fed a commercial fodder, while another group (FD) was fed the same fodder, but including BP2FS ($6{\times}10^{4}$ cfu $g^{-1}$ fodder), two times daily for 120 days. The mean body weight of the FD group (67.29${\pm}$12.62 g) was higher than that of the UFD group (56.56${\pm}$8.21 g) after 120 days. The survival rate of FD was 80% compared to 40% for the UFD group. Cumulative mortalities in the FD and UFD groups were 18.95% and 60.98% respectively. B. polyfermenticus KJS-2 was isolated from the intestines of the FD group and the number of viable colonies was estimated to be $1.04{\times}10^{4}$ cfu $g^{-1}$. Iridovirus and Vibrio vulnificus was detected in the organs of the UFD group but not in the FD group. All of the infected fish showed typical clinical symptoms of hemorrhage in their tail fins. Dissection of the infected internal organs revealed liver congestion and spleen enlargement - typical symptoms caused by iridovirus infection. These results clearly show that BP2FS is highly beneficial in preventing O. fasciatus from iridovirus infection.

• Journal of fish pathology
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• v.21 no.3
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• pp.181-188
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• 2008

Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay was used to detect and identify four fish viruses, fish iridovirus, viral hemorrhagic septicaemia virus (VHSV), viral nervous necrosis virus (VNNV), hirame rhabdovirus (HRV). Four viruses were detected by PCR with each specific primers. Identification of iridovirus was achieved by digesting the PCR amplified fragment with a restriction enzyme ApaⅠ. It was possible to distinguish positive from false positive PCR amplicons of VHSV by RFLP of PstⅠ or HindⅢ restriction enzymes. VNNV was identified using RFLP of BamHⅠrestriction enzyme and HRV was identified by XbaⅠ restriction enzyme. This approach can be used for more rapid, simple and specific diagnosis of fish viral diseases.

• Journal of fish pathology
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• v.21 no.1
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• pp.13-20
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• 2008

This study evaluates the pathogenicity in striped beakperch, Oplegnathus fasciatus infected with red sea bream iridovirus (RSIV) at different water temperature (17°C, 20°C, 25°C and 27°C). When the fish group was infected with RSIV at 17°C and 20°C, cumulative mortality did not show any significant difference with control group. In contrast, the case at 25°C and 27°C, cumulative mortality reached more than 80%. However, RSIV was detected from all of the fish in each temperature. To confirm a relationship between temperature change and heat shock protein (HSP), partial HSP70 cDNA was isolated from striped beakperch.

• Development and Reproduction
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• v.21 no.4
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• pp.371-378
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• 2017

Interferon-stimulated gene 15 (ISG15) is known to interfere with viral replication and infection by limiting the viral infection of cells. Interferon-stimulated gene 15 (ISG15) interferes with viral replication and infectivity by limiting viral infection in cells. It also plays an important role in the immune response. In this study, tissue-specific expression of ISG15 in healthy rock bream samples and spatial and temporal expression analysis of rock bream ISG15 (RbISG15) were performed following rock bream iridovirus (RSIV) infection. RbISG15 expression was significantly higher in the eye, gill, intestine, kidney, liver, muscle, spleen, and stomach, but low in the brain. There were particularly high levels of expression in the liver and muscle. RbISG15 expression was also examined in several tissues and at various times following RSIV infection. ISG15 expression increased within 3 h in the whole body and decreased at 24 h after infection. In addition, temporal expression of several tissues following RSIV infection showed a similar pattern in the muscle, kidney, and spleen, increasing at 3 h and decreasing at 72 h. These results suggest that ISG15 plays an important role in the immune response of rock bream. Overall, this study characterizes the response of RbISG15 following RSIV infection.

• Journal of fish pathology
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• v.35 no.2
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• pp.141-155
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• 2022

Rock bream iridovirus (RBIV) causes high mortality and economic losses in the rock bream (Oplegnathus fasciatus) aquaculture industry in Korea. Viral open reading frames (ORFs) expression profiling at different RBIV infection stages was investigated using microarray approaches. Rock bream were exposed to the virus and held for 7 days at 23 ℃ before the water temperature was reduced to 17 ℃. Herein, 28% mortality was observed from 24 to 35 days post infection (dpi), after which no mortality was observed until 70 dpi (end of the experiment). A total of 27 ORFs were significantly up- or down-regulated after RBIV infection. In RBIV-infected rock bream, four viral genes were expressed after 2 dpi. Most RBIV ORFs (26 genes, 96.2%) were significantly elevated between 7 and 20 dpi. Among them, 12 ORF (44.4%) transcripts reached their peak expression intensity at 15 dpi, and 14 ORFs (51.8%) were at peak expression intensity at 20 dpi. Expression levels began to decrease after 25 dpi, and 92.6% of ORFs (25 genes) were expressed below 1-fold at 70 dpi. From the microarray data, in addition to the viral infection, viral gene expression profiles were categorized into three infection stages, namely, early (2 dpi), middle (7 to 20 dpi), and recovery (25 and 70 dpi). RBIV ORFs 009R, 023R, 032L, 049L, and 056L were remarkably expressed during RBIV infection. Furthermore, six ORFs (001L, 013R, 052L, 053L, 058L, and 061L) were significantly expressed only at 20 dpi. To verify the cDNA microarray data, we performed quantitative real-time PCR, and the results were similar to that of the microarray. Our results provide novel observations on broader RBIV gene expression at different stages of infection and the development of control strategies against RBIV infection.

• Journal of fish pathology
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• v.36 no.2
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• pp.213-228
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• 2023

We evaluated the transcriptional response of interferon (IFN)-related genes in rock bream iridovirus (RBIV)-infected rock bream under high-, low-, or no-mortality conditions induced by different stocking water temperatures. Under the high susceptibility condition (group A, water temperature 26℃, 100% mortality), only the Mx gene was expressed early, with prolonged expression, and with heavy viral loads of approximately 10⁶~10⁷ major capsid protein gene copies/μL from 4 to 10 days post infection (dpi). However, IRF1, IRF3, IRF8, STAT1, ISG15, PKR, Viperin, GVIN1, IFI44, and ISG56 were activated at later time points (8 dpi) and then quickly decreased (10 dpi). For the low susceptibility condition, the water temperature was set at 23℃ for 7 days (group B) and then reduced to 17℃. Group B exhibited a 28% mortality rate, in which persistent and effective antiviral responses were observed for long periods of time. In particular, at 20 and 22 dpi, when virus replication was peaked at approximately 10⁷/μL, the expressions of most of the IFN-related genes (IRF1, IRF3, IRF8, Mx, STAT1, ISG15, PKR, Viperin, GVIN1, IFI44, and ISG56) were significantly higher in group B than in the control group. Moreover, prolonged and higher levels of IRF3 (at least 30 dpi), IRF8 (at least 30 dpi), ISG15 (at least 30 dpi), PKR (at least 28 dpi), Viperin (at least 30 dpi), and IFI44 (at least 30 dpi) were also observed in the recovery stage of infection. Under the no-susceptibility condition at 17℃ (0% mortality), significantly elevated levels of IRF3, Mx, ISG15, and PKR were observed mostly until 20 dpi. The findings indicate that RBIV infection can induce an efficient IFN-mediated antiviral immune response in low- and no-susceptibility conditions. The findings could be valuable for effective control of viral pathogens in fish.

• Journal of fish pathology
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• v.37 no.1
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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.

• Proceedings of the Korean Aquaculture Society Conference
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• 2006.05a
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• pp.472-473
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• 2006

• Journal of fish pathology
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• v.34 no.2
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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.