• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.4
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• pp.403-410
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• 2015

Viral nervous necrosis (VNN) is a serious disease of sevenband grouper Epinephelus septemfasciatus in Korean aquaculture farms. However, we suggest the following preventative methods for hatcheries: 1) disinfecting rearing water, 2) selecting spawners via ELISA and PCR, 3) selecting eggs via PCR, 4) disinfecting fertilized eggs, and 5) proper facilities management. When these methods are implemented, nervous necrosis virus (NNV)-free fish are produced because vertical and horizontal transmission is prevented. However, horizontal transmission of NNV through rearing seawater sourced from the environment during grow-out stages in sea cages can still occur. Live NNV vaccines with a low rearing temperature or Poly(I:C) immunization are very effective at preventing horizontal transmission of NNV in rearing farms. Furthermore, even after VNN is contracted, fish mortality can be reduced by administering Poly(I:C).

• Journal of fish pathology
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• v.25 no.2
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• pp.111-116
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• 2012

Prevalence of viral nervous necrosis (VNN) in sevenband grouper Epinephelus septemfasciatus farms was investigated during the period of 2006-2008. The outbreak of the VNN was observed from August (water temperature: $24-26^{\circ}C$) to September or October ($20-25^{\circ}C$). The viral infection resulted in acute or chronic mortality of the host, where the mortality rate of juvenile fish was higher than that of the adult fish. Phylogenetic analysis based on partial RNA2 coat protein gene nucleotide sequences revealed that all the isolates from sevenband grouper were classified into the genotype redspotted grouper nervous necrosis virus (RGNNV). In conclusion, VNN of juvenile and adult sevenband groupers during the summer season (July to October, water temperature: about $24^{\circ}C$) was caused by virus belonging to the genotype RGNNV.

• 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.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.05a
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• pp.511-512
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• 2001

VNN(viral nervous necrosis)는 종묘단계 및 양성장의 해산어 양식장에서 발생하는 바이러스성 질병으로 외견적으로 척추만곡, 이상유영, 체색흑화와 조직학적으로는 뇌와 망막에 공포 및 괴사를 형성하고, 또한 매우 높은 폐사율을 나타내는 질병으로 보고되어 있다. 이러한 질병은 성공적인 종묘의 생산 및 보급을 위해서 반드시 해결해야 할 사항이다. (중략)

• Journal of fish pathology
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• v.14 no.2
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• pp.91-95
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• 2001

Mass mortalities occurred among red drum larvae, 20 to 30 days old, culturing at hatcheries on southern costal area. No specific external signs were observed except abnormal swimming and spinal deformity. It was, however, suspected as a viral etiology due to high mass mortalities so that histopathological and molecular biological study was performed to evaluate the agent. Both vacuoles and necrosis were observed on nerve cells of brain and eye by H-E staining, and viral particles were observed on electronmicroscopic examination. On the other hand, DNA fragment, approximately 426 bps, was amplified with RT-PCR. The above results were able to diagnosis the etiological agent of mass moralities in red drum larvae as VNN(viral nervous necrosis)virus.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.3
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• pp.328-331
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• 2018

We developed and subsequently characterized mouse monoclonal antibodies (MAbs) against nervous necrosis virus (NNV, RGNNV genotype). We established six hybridoma clones secreting MAbs against NNV antigen: 2B1, 2B11, 2C12, 13C1-1, 13C1-2 and 14D11. All six MAbs belonged to the IgG2a isotype with a kappa light chain and their reactivity recognized against the 41 kDa coat protein of NNV by Western blot analysis. The affinity constants of the six MAbs were measured by enzyme-linked immunosorbent assay (ELISA). All six MAbs reacted with two NNV isolates (SgNag05 and Gemunodo06), while no reactivity was observed with five know fish viruses, namely marine birnavirus, infectious pancreatic necrosis virus, viral hemorrhagic septicemia virus, hirame rhabdovirus, and infectious hematopoietic necrosis virus. Moreover, high ELISA optical density (OD) values (0.87-1.42) were observed in the brain tissues of NNV-infected sevenband grouper, while low OD values (less than 0.12) were recorded in the brain tissues of uninfected fish. These results suggest that these six MAbs are highly competent and useful for the detection of NNV with the RGNNV genotype.

• Journal of fish pathology
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• v.33 no.2
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• pp.103-109
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• 2020

In order to use nervous necrosis virus (NNV) virus-like particles (VLPs) as a delivery tool for heterologous antigens or plasmids, we attempted to produce red-spotted grouper nervous necrosis virus (RGNNV) VLPs displaying a partial region of viral hemorrhagic septicemia virus (VHSV) glycoprotein at the surface and VLPs that are harboring DNA vaccine plasmids within the VLP. A peptide encoding 105 amino acids of VHSV glycoprotein was genetically inserted in the loop region of NNV capsid gene, and VLPs expressing the partial part of VHSV glycoprotein were successfully produced. However, in the transmission electron microscope analysis, the shape and size of the partial VHSV glycoprotein-expressing NNV VLPs were irregular and variable, respectively, indicating that the normal assembly of capsid proteins was inhibited by the relatively long foreign peptide (105 aa) on the loop region. To encapsulate by simultaneous transformation with both NNV capsid gene expressing plasmids and DNA vaccine plasmids (having an eGFP expressing cassette under the CMV promoter), NNV VLPs containing plasmids were produced. The encapsulation of plasmids in the NNV VLPs was demonstrated by PCR and cells exposed to the VLPs encapsulating DNA vaccine plasmids showed fluorescence. These results suggest that the encapsulation of plasmids in NNV VLPs can be done with a simple one-step process, excluding the process of disassembly-reassembly of VLPs, and NNV VLPs can be used as a delivery tool for DNA vaccine vectors.

• Journal of fish pathology
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• v.30 no.2
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• pp.149-154
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• 2017

Mouse monoclonal antibodies (MAbs) were produced by using viral hemorrhagic septicemia virus (VHSV, genotype IVa) as an immunogen, isolated from diseased olive flounder (Paralichthys olivaceus). Four hybridoma clones secreting MAbs against VHSV were established. The MAbs were recognized the nucleoprotein (MAb 4), phosphoprotein (MAb 1) and matrix protein (MAbs 2 and 3) of VHSV by western blot analysis. Among them, the MAbs 1 and 4 strongly reacted with the VHSV-infected FHM cells, but not normal FHM cells. In enzyme linked immunosorbent assay, the four MAbs reacted with the VHSV, but not different six fish viruses (infectious hematopoietic necrosis virus, hirame rhabdovirus, spring viraemia of carp virus, infectious pancreatic necrosis virus, marine birnavirus and nervous necrosis virus). These results indicate that the MAbs are useful for diagnosis of VHSV infection.

• Korean Journal of Veterinary Research
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• v.28 no.2
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• pp.371-377
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• 1988

In order to know the effect of dexamethasone on the induction of the rabbit viral hepatitis, the pathological changes were observed in the native rabbits, 2 to 6 months old in age, that were injected by dexamethasone and liver emulsion of Angora rabbit naturally infected with viral hepatitis. The results were summarized as follows: The native rabbits injected by dexamethasone and liver emulsion were infected with viral hepatitis and died between 2 and 7 days after inoculation. Clinical signs and gross lesions were very similar to those of Angora rabbit naturally occurred, In microscopical findings, the hepatic lesions were characterized by peripheral necrosis of the lobules, and peripheral necrosis of the lobules with fatty changes of hepatic cells was occurred in a few cases. Perivascular lymphocytic infiltration in the central nervous system was observed in some cases, The lesions of the other organs were very similar to those of Angora rabbit naturally occurred. On the other hand, the native rabbits that were injected by only liver emulsion of Angora rabbit naturally infected with viral hepatitis were not infected with the disease except very few cases.

• Journal of fish pathology
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• v.12 no.2
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• pp.107-113
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• 1999

The pathogenicity of the fish nodavirus causing viral nervous necrosis (VNN) of sevenband grouper, Epinephelus septemfasciatus was examined in sevenband grouper and other marine fish by intramuscular injection. Sevenband groupers of 27~104 g in body weight were highly susceptible to the fish nodavirus, but yellowtail (537 g in body weight), red seabream (207 g), rock bream (43 g), flounder (41 g), tiger puffer (27 g) and rockfish (94 g) of the sizes used to this experiment were not. The pathogenicity of the viral agent to the sevenband grouper was high without regard to fish sizes at rearing water temperature over $20^{\circ}C$, but not at $15^{\circ}C$. Therefore, susceptibility of sevenband grouper to the viral agent causing VNN was thought to be water temperature-dependent rather than fish size (age-dependent). Compared to the infectivity of the viral agent to sevenband grouper with artificial infection methods, fish were successfully affected by intramuscular, intraperitoneal, oral, dipping and cohabitation administrations although there were slight differences in mortalities among infection methods. And survival sevenband grouper after infection with the fish nodavirus was resistant to the reinfection for a long time.