• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.3
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• pp.237-241
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• 2002

This study was performed both to explore the host of nervous necrosis virus (NNV) between mariculturing fish species and to examine the phylogenic position of the NNV in Korea. NNV was confirmed on the basis of histopathological and molecular biological examination, then VNN infection was Preyed from either moribund or dead fishes including red drum, Sciaenops ocellatus; oblong rock fish, Sebastes oblongus and flounder, Paralichthys olivaceus. As a result of sequencing for a part of ms, virus from red drum was showed $98\%, $97\%, $86\% and $74\% homology with oblong rock fish, grouper, Japanese flounder and striped jack, respectively. On the other hand, NNV from oblong rock fish was demonstrated $96\%, $85\% and $72\% homology with grouper, Japanese flounder and striped jack, respectively. NNV from red drum and oblong rock fish was exhibited phylogenically distant from the representative NNV, SJNNV originated from striped jack. On the contrary, the viruses appeared to be similar species with Taiwan NNV isolated from culturing grouper.

• Journal of fish pathology
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• v.35 no.1
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• pp.121-128
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• 2022

Recent studies revealed that histone proteins are involved in innate immune responses during pathogen invasion as well as DNA packing. This study characterized the histone genes (H2A.V) of sevenband groupers and analyzed gene expression in NNV-infected sevenband groupers. The open reading frame (ORF) of H2A.V is 387 bp which encoded 128 amino acid residues. The deduced amino acid sequence of H2A.V harbor a highly conserved domain for H2A/H2B/H3 and H2A_C binding domain. Quantitative real-time PCR analysis showed that H2A.V had a high gene expression level in the brain and blood after being NNV-infected. An increase in extracellular histone protein in the blood has been identified as a biomarker for vascular function in humans. More research is required to understand histone's immune response at the protein level or in aquatic animals.

• Korean Journal of Veterinary Service
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• v.17 no.1
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• pp.67-80
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• 1994

8-10 week old ICR mice were infected intracerebrally and intraperitoneally with different encephalomyocarditis virus(K$_3$, $K_{11}$, ATT-VR 129) to observe histopathological and immunohistochemical change. Results obtained throuh the experiments were summarized as follows : 1. No differences in clinical signs by the virus strains and the inoculation routes were found. Mice infected with EMCV showed clinical signs after 3 days of inoculation. Main clinical signs were tremors, convulsions, circling movement, and uni or bilateral hindleg paralysis followed by death on the 3-8 days. In general, most of the infected animals died or recovered closely on the 8th day of postinoculation. 2. At necropsy, petechial and ecchymotic hemorrhages in lung were observed and no specific findings in other were observed. 3. In histopathological observation, neuroal cell degeneration perivascular mononucear cell in-filtration gliosis were appeared in central nervous system. Myocarditis with myocardial degeneration and necrosis, calcification were observed along with acinar cell necrosis of exocrine glands in pancreas, severe glomerulonephritis in kidney. Also, focal necrosis of hepatocytes and interstitial pneymonia hyperemia, hemorrhages in lungs were observed. 4. By immunohistochemical staining using ABCIT method, the positive cells were recognized in intracytoplasm of acinar cell in pancreas and intracytoplasm of neuronal cells in cerebrum.

• 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 Veterinary Research
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• v.30 no.1
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• pp.93-102
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• 1990

Thirty-day-old piglets were intranasally or subcutaneously inoculated with 2ml of Aujeszky's disease virus, NYJ-1 strain, at the titer of $10^{6.75}$ $TCID_{50}/0.1ml$, that was isolated from the diseased piglets in Korea, and histopathological studies were performed to elucidate the pathognomonic characters of the isolate. Results obtained through the experiments were as follows: 1. Major clinical signs on the 2nd and 3rd days post inoculation (p.i.) were fever, anorexia and dyspnea. On the 6th and 7th days p.i., nervous signs, severe dyspnea and salivation were observed in the group of intranasal inoculation, and one out of 3 piglets in this group died on the 7th day p.i.. General signs were more severe in the group of intranasal inoculation than the group of subcntaneous injection. Between the 8th and l0th days p.i., the signs subsided and the piglets were completely recovered from the illness. 2. Hematologically, most of the inoculated pigs showed a mild lymphocytopenia on the 5th and 6th days p.i.. 3. By necropsy, swelling and hemorrhagic lesions were observed in tonsil, central nervous system and lung. No specific changes were grossly found in other parenchymatous organs. 4. In histopathological study, degeneration and necrosis of nervous cells, non-suppurative meningoencephalitis, diffuse or focal gliosis, perivascular cutting and degeneration of ganglion cells were observed in central nervous system, and swelling and hemorrhagic changes were shown in the tissues of liver, lung and lymph nodes. 5. By indirect immunofluorescence antibody assay using ADV-monoclonal antibody, specific ADV antigens were detected in the tissues of tonsil, brain and spleen of the succumbed piglet. However, in the experimentally slaughtered piglets, the specific reactions were noted only in the tonsils.

• Korean Journal of Veterinary Research
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• v.34 no.2
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• pp.349-359
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• 1994

To elucidate pathogenicity to hamster of encephalomyocarditis virus $K_3$ strain that was isolated in Korea from the swine with reproductive failures, adult male syrian hamsters were experimentally infected intraperitoneally with the virus at $10^{7.0}\;TCID_{50}/0.1ml$ and pathological and immunohistochemical studies were performed. The results obtained through the experiment were as follows. 1. Clinical signs such as depression, unkempt hair and bilateral parlysis of hind limbs were observed. 2. At necropsy, mild congestion was observed in the cerebrum, liver, kidney and lung, and atrophy was evident in testis. 3. In microscopic observation, degeneration and necrosis of the nervous cells and perivascular mononuclear cell infiltration were manifested in central nerve system, and various degrees of degeneration and necrosis of parenchymal cells were detected in pancreas, lacrimal gland, liver, kidney and testis. 4. In immunohistochemical observation, strong positive reactions were observed in degenerated parenchymal cell of testis, and weak positive reactions, in hepatocytes.

• Korean Journal of Ichthyology
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• v.29 no.3
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• pp.157-164
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• 2017

In 2015, a nervous necrosis virus (NNV) was isolated from sevenband grouper, Epinephelus septemfasciatus, maintained in land-based aquaculture system at below $12^{\circ}C$ in winter. Mortality was up to 30% in brood fish, over 4 kg of body weight. Moribund fish showed clinical sings typical of viral encephalopathy and retinopathy (VER), also called viral nervous necrosis (VNN), such as uncoordinated, corkscrew-like swimming behavior, belly-up at rest, darkening of body, cloudy eyeball and hyperinflation of the swim bladder. Aetiology of the disease was confirmed by gross observation of clinical signs, histopathology and molecular diagnosis. Histological studies revealed severe vacuolation and necrosis in the brain. Molecular diagnosis by revere transcription-polymerase chain reaction (RT-PCR) specific to batanodavirus yielded a positive result. The nucleotide sequences of the PCR-amplified fragment were 99.48~100% similar to barfin flounder nervous necrosis virus (BFNNV) genotype and most closely aligned with Pacific cod betanodavirus (PCNNV). This is the first report of natural batanodavirus, NNV infection in sevenband grouper reared in low water temperature during winter (below $12^{\circ}C$) in Korea.

• Journal of fish pathology
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• v.11 no.2
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• pp.97-104
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• 1998

Since 1989, mass mortality has repeatly occurred in cage-cultured sevenband grouper, Epinephelus septemfasciatus along the southern coast of Korea in the summer season and usually reached over 80% within a few months. Diseased fish showed the clinical signs of anorexia, dark coloration, loss of eqilibrium, spinal swimming behaviour, vertebral deformity and inflation of swim bladder. Histopathologically, necrosis and/or vacuolation of the nerve cells in the brain and retina were observed. We previously reported that the causative agent was filtrable. The causative agent was not culturable in various fish cells; RTG-2, CHSE-214, BF-2, EPC and FHM. However, electron microscopic observation revealed unenveloped icosahedral viral particles with about 30 nm in diameter in the cytoplasm of nerve cells of the brain. The characteristics of the virus was tested by an artificial infection with the filtrate of the homogenate of diseased fish. The pathogenicity of the virus was retained after treatment with ether or heat ($50^{\circ}C$, 30 min) but partly lost by pH 3 or 11 treatment. These results suggest that the causative agent are similar to the fish nodavirus. In order to compare the causative agent with a fish nodavirus, Striped Jack Nervous Necrosis Virus (SJNNV), a polymerase chain reaction (PCR) was performed with primers specific to SJNNV. As a result, about 430 by PCR products were detected from the brain and the eye of both naturally and artificially infected sevenband grouper. All these results represent that the mass mortality in the cultured sevenband grouper is caused by the infection of a nodavirus similar to SJNNV and this is the first report of a fish nodavirus from the cultured sevenband grouper in Korea.

• Journal of fish pathology
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• v.34 no.1
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• pp.99-104
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• 2021

In this study, we investigated safety and efficacy of a low temperature immunization protocol with NNV in red spotted grouper, Epinephelus akaara and long tooth grouper, Epinephelus bruneus and seven band grouper, Hyporthodus septemfasciatus. Further, growth rate between immunized and naïve fish was evaluated during the experiment to check side effect of immunization. Three grouper species were immunized by immersion method with live NNV at 10^5.0 TCID₅₀/mL at 16.5℃ for 30 min and reared for 120 days at natural sea water temperature. To evaluate growth rate, total length and wet weight was measured 7 times after immunization. Immunized three grouper species were challenged by intramuscular inoculation with NNV at 10^4.2 TCID₅₀/100 µL/fish. Immunization at low temperature with live NNV did not show any clinical symptoms of infection, mortality and inhibition of growth. After challenge, cumulative mortality of naïve seven band grouper, red spotted grouper, long tooth grouper were 45, 10, 20 %, respectively. However no mortality was observed at immunized groupers. Thus, it was demonstrated that immunization at low temperature with live NNV are able to protect three different species of groupers without inhibition of growth.

• Journal of fish pathology
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• v.32 no.2
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• pp.59-67
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• 2019

We developed and subsequently characterized mouse antibodies (MAbs) against viral hemorrhagic septicemia virus (VHSV, genotype IVa), the causative agent of VHS. Five hybridoma clones secreting MAbs against VHSV were established. The MAbs recognized the glycoprotein (MAbs 2C10, 18H4, 23H6, and 30B7) and nucleocapsid protein (15E10) of VHSV by western blot analysis. All five MAbs reacted with VHSV-infected cells and tissue homogenates of VHSV-infected olive flounder (Paralichthys olivaceus) by western blot analysis. Whereas, no reactivity was observed in normal cells and tissue homogenates of normal olive flounder. Moreover, these MAbs reacted with VHSV, but did not react with other fish viruses (infectious hematopoietic necrosis virus, hirame rhabdovirus, spring viraemia of carp virus, infectious pancreatic necrosis virus, marine birnavirus, and nervous necrosis virus) by enzyme linked immunosorbent assay (ELISA). These results indicate that the MAbs are specific to VHSV and can be of value in VHSV detection.