• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.10a
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• pp.145-146
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• 2001

Despite a variety of development in fish farming during the last decades, fish diseases by bacteria, virus, and parasites are still major problems in aquaculture. Aquaculture of Hounder fish is widely performed around Korea as well as Jeju island, due to relatively stable seed production, short farming period, and a higher value in market. However, intensive feeding and environmental pollution in aquacutural farm act as a great limiting factor in economic aspect. (omitted)

• Journal of fish pathology
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• v.35 no.2
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• pp.247-250
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• 2022

About 6.7% mortality was reported in a starry flounder (Platichthys stellatus) aquaculture farm in 2022. Most of the diseased fish showed a loss of pectoral fin, hemorrhages on muscle and gills, pale gills, enlarged spleen, and nodules on kidney. Parasites, fungi or viruses (viral hemorrhagic septicemia virus and hirame novirhabdovirus) were not detected from diseased fish. However, numerous bacteria were isolated from liver, spleen and kidney. Nucleotide sequences of the A-protein-encoding virulence array protein gene (vapA) of the bacteria showed 99.93% identity with Aeromonas salmonicida subsp. masoucida. This study is the first report of isolation of atypical A. salmonicida in cultured starry flounder in Korea.

• Journal of fish pathology
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• v.34 no.2
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• pp.123-131
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• 2021

This study investigated the phylogenetic classification and pathogenicity of 6 infectious hematopoietic necrosis virus (IHNV) strains isolated from salmonid fish in Gangwon-do, Korea. Based on the nucleotide sequence of mid-G region, all six strains belong to J genotype, of which 5 are J-Nagano type and 1 J-Shizuoka type. In a challenge test, 5 isolates of J-Nagano type IHNV showed a various mortalities as 2 isolates induced a high mortality of 100% and the other 3 isolates induced mortalities of 50, 30, and 20% after intraperitoneal injection in rainbow trout (Oncorhynchus mykiss). Meanwhile no mortality was occurred by 1 isolate of J-Shizuoka type virus. Thus, it seems that there might be no relation between genotype and pathogenicity within IHNV J genotypes. This is contrary to previous studies where reported a higher pathogenicity of J-Shizuoka type virus than J-Nagano type virus in rainbow trout. Further examination will be required to clarify this since only one J-Shizuoka type virus was analyzed in this study.

• Journal of fish pathology
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• v.19 no.1
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• pp.65-72
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• 2006

Nervous necrosis virus (NNV) that causes severe mortality during seed production of red drum (Sciaenops ocellatus) is known to be vertically transmitted from infected spawners. This study was conducted to produce NNV free seeds by testing spawners for NNV infection and using virus free eggs for seed production. RT-PCR analysis of 40 spawners showed 18 positives and 22 negatives. NNV was not detected from eggs obtained from the negative spawners but was detected from those obtained from the positives. NNV was not detected from culturing seawater in tanks and Chlorella spp., Brachionus plicatilis., and Brine shrimp those were provided as live feed. The survival rates of fry from NNV positive and negative spawners were 80% and 85%, respectively by two weeks after hatching. The mortality increased from 25days after hatching and the final survival rate of seeds from NNV positive and negative spawners were 0% and 18.3%, respectively on 41 days after hatching. These results suggested that virus free red drum seeds can be obtained by using virus-free spawners.

• Journal of fish pathology
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• v.24 no.2
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• pp.75-84
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• 2011

The amino acid sequence of glycoprotein of Korean VHSV isolate (KR'01-1) was analyzed using the DNAStar Protean system. Based on the flexibility, hydrophilicity, antigenic index and surface probability, three regions (Gp1, Gp2 and Gp3) were selected as potential antigenic determinants. Three oligopeptides containing the amino acid sequences of the three regions were synthesized and polyclonal antibodies were raised against them. The activities of the antibodies were analyzed by Western blotting and virus neutralization test. The results showed that antibodies raised against oligopeptides Gp1 and Gp2 neutralized the infectivity of VHSV, suggesting that they can be possible candidates for subunit vaccines against VHS diseases in olive flounder.

• Journal of fish pathology
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• v.31 no.2
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• pp.81-85
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• 2018

Fetal bovine serum (FBS) is an essential element of cell growth and can also affect the viral replication. In this study, we tried to find out whether FBS concentration affects the viral infectivity titer of IHNV and IPNV. EPC cells were suspended with MEM supplemented with various concentrations of FBS (MEM0, MEM2, MEM5 and MEM10) and cultured in 96-well plate. Each virus was 10-fold diluted virus and inoculated in 96-well plate. The highest infectivity titer of IHNV was $10^{7.88}\;TCID_{50}/mL$ in 96-well plate using MEM5 and the lowest one was $10^{7.30}\;TCID_{50}/mL$ in 96-well plate using MEM10. The highest infectivity titer of IPNV was $10^{7.47}\;TCID_{50}/mL$ in 96-well plate using MEM5 and the lowest one was $10^{6.97}\;TCID_{50}/mL$ in 96-well plate using MEM10. This study showed that not only 0% FBS but 10% FBS leads low infectivity titer of IHNV and IPNV. Therefore, it is considered that the desirable concentration of FBS is 2% or 5% for measurement of infectivity titer of IHNV and IPNV.

• Korean Journal of Animal Reproduction
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• v.25 no.2
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• pp.171-180
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• 2001

Compared to other gene transfer system, the advantages of retrovirus-mediated gene transfer are technical ease, efficient expression and genetic stability. Despite the high potency of the retrovirus vector system in gene transfer, one of the drawbacks is a difficulty in concentration of virus stock. To overcome this problem, we tested a new retrovirus vector system producing the progeny retrovirus particles encapsidated with VSV-G (vesicular stomatitis virus G glycoprotein). The infectivity of this virus was not sacrificed by ultracentrifugal concentration and the host cell range extended from all mammalian to fish embryos. Virus titer after 1,000 x concentration was more than 10$^{8}$ CFU/ $m\ell$ on most of the target cell lines. We applied this pantropic viruses in transgenic chicken production by injecting the concentrated (100$\times$) stock into subgerminal cavity of stage X chicken embryos. The survival rate of chicken embryos after injection was about 20% and gene integration rate in surviving embryos was scored almost 100%. Analyses of RT-PCR and fluorescence microscopy, however, showed no evidence of the transgene expression.

• Journal of fish pathology
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• v.22 no.3
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• pp.283-291
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• 2009

This study was conducted to evaluate the effects of a commercial extruded pellet (EP) and raw fish moist pellet (MP) diet on disease prevalence and serum chemistry of olive flounder Paralichthys olivaceus grown in two commercial-scale aquaculture farms from July to December in 2008. The contents of serum GOT, GPT and glucose in fish fed EP diet (EP group) were higher than those of fish fed the MP diet (MP group). There were no distinct differences in survival rates and mean detection rates of fish pathogens among fish group fed the experimental diets. However, the mean detection rate of fish pathogens in MP group was higher than that of EP group from July to October which are high water temperature season. The dominant pathogens isolated in EP group were Dactylogyrus sp., E. tarda and red sea bream iridovirus (RSIV). On the other hand, Trichodina sp., Streptococcus spp., viral nervous necrosis virus (VNNV) were dominant in MP group.

• Journal of fish pathology
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• v.16 no.3
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• pp.175-181
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• 2003

VSNC is a viral disease causing significant economic losses in cultured carp Ciprinus carpio L. in Korea. Carps were immunized with prepared vaccines against VSNCV and examined specific and nonspecific immune responses. Carps were injected by O.2㎖ of formalin-killed vaccine (FKV), heat-killed vaccine (HKV) or E-MEM, respectively and dealt with boost with same way two weeks later. The lysozyme activity of serum and chemiluminescent reponses of head-kidney leucocytes showed increased responses during 2-7 days post-first injection (pfi) and post-boost (pb) in the vaccinated fish, and then decreased to the level of control. As measured by ELISA, vaccinated groups showed a significant increase in VSNCV-specific serum antibodies between 2 weeks pfi and 6weeks pb with a peak at 2 weeks pb. Results of the virus challenge showed that the fish vaccinated with FKV have induced protective immunity, while HKV injection hardly provided protection.

• Journal of Microbiology and Biotechnology
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• v.25 no.10
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• pp.1761-1767
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• 2015

Sevenband grouper, Epinephelus septemfasciatus, is becoming an important aquaculture species in Korea. However, viral nervous necrosis disease is a large problem causing mass mortality in sevenband grouper aquaculture. Recombinant protein vaccines are one of the best methods to reduce these economic losses. However, the cell-based expression method mainly produces inclusion bodies and requires additional procedures. In this study, we expressed a recombinant viral coat protein of sevenband grouper nervous necrosis virus (NNV) using a cell-free protein synthesis system. The purified recombinant NNV coat protein (rNNV-CP) was injected into sevenband grouper at different doses followed by a NNV challenge. Nonimmunized fish in the first trial (20 μg/fish) began to die 5 days post-challenge and reached 70% cumulative mortality. In contrast, immunized fish also starting dying 5 days postchallenge but lower cumulative mortality (10%) was observed. Cumulative morality in the second trial with different doses (20, 4, and 0.8 μg/fish) was 10%, 40%, and 50%, respectively. These results suggest that rNNV-CP can effectively immunize sevenband grouper depending on the dose administered. This study provides a new approach to develop a recombinant vaccine against NNV infection for sevenband grouper.