• Korean Journal of Veterinary Research
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• v.40 no.1
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• pp.110-116
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• 2000

Duck viral hepatitis is an acutic, highly infectious viral disease of young ducklings. The most practical means for controlling duck viral hepatitis is the vaccination of ducklings or of a breeding stock. We attempted to develop a vaccine strain of duck hepatitis virus (DHV) using a Korean isolate by serial chicken embryo passages. The propagation of DHV in chicken embryos was carried 140 passages. After the $50^{th}$ passage, of which the virus was non-pathogenic for ducklings, approximately every $20^{th}$ passage of the virus was tested for vaccinal efficacy. Both the $70^{th}$ and $90^{th}$ passage of the virus gave good protection against challenge infection to a DHV-DRL reference strain(type 1) and a virulent Korean isolate. The $110^{th}$, $125^{th}$ and $140^{th}$ passage of the virus were less protective than the $70^{th}$ and $90^{th}$ passage, which means that more than $110^{th}$ passage may lead to over-attenuation of the virus. Ducklings vaccinated with the chicken-embryo-adapted virus by oral, intramuscular or eye drop administration showed earlier resistance to challenge infection from 3 to 7 days postvaccination. Of the above methods, ducklings vaccinated intramuscularly presented the most rapid resistance against challenge. The minimum immune dose of the chicken-embryo-adapted virus in ducklings was also studied. Ducklings inoculated with a dose of $10^{2.0}\;ELD_{50}$ and below were not fully protected against challenge with a virulent DHV, showing a protection rate of 67% to 73%, but ducklings inoculated with a dose of $10^{3.0}\;ELD_{50}$ and over were completely protected. The virus yield of the chicken-embryo-adapted DHV was examined at 24hrs and 48hrs of the incubation time in the allantoic fluid, embryo head and embryo minus head of the embryonating egg. In all three components, the titer of the virus was higher at 48 hours than that at 24 hours after incubation. And the titer of the virus was higher in the embryo minus head, embryo head and the allantoic fluid, in order. Field trials for evaluating the efficacy of the attenuated DHV as a live vaccine were done in duck farms with about 25% mortality of flocks resulting from duck viral hepatitis. After the use of the experimental vaccine, the mortality due to duck viral hepatitis was dramatically reduced in the farms. These results indicated that the attenuated DHV using a Korean isolate could be a good candidate as a live vaccine strain of DHV in Korea.

• Korean Journal of Veterinary Research
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• v.61 no.2
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• pp.13.1-13.8
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• 2021

Mammalian reovirus (MRV) causes respiratory and intestinal disease in mammals. Although MRV isolates have been reported to circulate in several animals, there are no reports on Korean MRV isolates from wildlife. We investigated the biological and molecular characteristics of Korean MRV isolates based on the nucleotide sequence of the segment 1 gene. In total, 144 swabs from wild animals were prepared for virus isolation. Based on virus isolation with specific cytopathic effects, indirect fluorescence assays, electron microscopy, and reverse transcription-polymerase chain reaction, only one isolate was confirmed to be MRV from a Korean roe deer (Capreolus pygargus). The isolate exhibited a hemagglutination activity level of 16 units with pig erythrocytes and had a maximum viral titer of 10^5.7 50% tissue culture infectious dose (TCID₅₀)/mL in Vero cells at 5 days after inoculation. The nucleotide and amino-acid sequences of the partial segment S1 of the MReo2045 isolate were determined and compared with those of other MRV strains. The MReo2045 isolate had nucleotide sequences similar to MRV-3 and was most similar (96.1%) to the T3/Bat/Germany/342/08 strain, which was isolated in Germany in 2008. The MReo2045 isolate will be useful as an antigen for sero-epidemiological studies and developing diagnostic tools.

• BMB Reports
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• v.38 no.1
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• pp.34-40
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• 2005

GLPG (Ganoderma lucidum proteoglycan) was a bioactive fraction obtained by the liquid fermentation of the mycelia of Ganoderma lucidum, EtOH precipitation, and DEAE-cellulose column chromatography. GLPG was a proteoglycan with a carbohydrate: protein ratio of 10.4: 1. Its antiviral activities against herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) were investigated using a cytopathic inhibition assay. GLPG inhibited cell death in a dose-dependent manner in HSV-infected cells. In addition, it had no cytotoxic effect even at 2 mg/ml. In order to study the mode of action of the antiviral activity of GLPG, cells were treated with GLPG before, during, and after infection, and viral titer in the supernatant of cell culture 48 h post-infection was determined using a $TCID_{50}$ assay. The antiviral effects of GLPG were more remarkable before viral treatment than after treatment. Although the precise mechanism has yet to be defined, our work suggests that GLPG inhibits viral replication by interfering with the early events of viral adsorption and entry into target cells. Thus, this proteoglycan appears to be a candidate anti-HSV agent.

• Journal of Microbiology and Biotechnology
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• v.25 no.11
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• pp.1960-1965
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• 2015

Rabbit hemorrhagic disease virus (RHDV) is highly contagious and often causes fatal disease that affects both wild and domestic rabbits of the species Oryctolagus cuniculus. A highly pathogenic RHDV variant (RHDVa) has been circulation in the Korean rabbit population since 2007 and has a devastating effect on the rabbit industry in Korea. A highly pathogenic RHDVa was isolated from naturally infected rabbits, and the gene encoding the VP60 protein was cloned into a baculovirus transfer vector and expressed in insect cells. The hemagglutination titer of the Sf-9 cell lysate infected with recombinant VP60 baculovirus was 131,072 units/50 μl and of the supernatant 4,096 units/50 μl. Guinea pigs immunized twice intramuscularly with a trial inactivated RHDVa vaccine containing recombinant VP60 contained 2,152 hemagglutination inhibition (HI) geometric mean titers. The 8-week-old white rabbits inoculated with one vaccine dose were challenged with a lethal RHDVa 21 days later and showed 100% survival rates. The recombinant VP60 protein expressed in a baculovirus system induced high HI titers in guinea pigs and rendered complete protection, which led to the development of a novel inactivated RHDVa vaccine.

• The Journal of the Korean Society for Microbiology
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• v.21 no.2
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• pp.227-231
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• 1986

The hemagglutination activities of Hantaan virus and Seoul virus were demonstrated. The hemagglutinins were prepared by sucrose-acetone extraction method from suckling mouse brains infectecd with Hantaan and Seoul viruses. Hemagglutination of goose erythrocytes by these viral hemagglutinins was pH dependent in phosphate buffer system. Hantaan and Seoul viruses were distinguished by pH range of hemagglutination. 76/118 and 79/90 strains of Hantaan virus showed hemagglutination at the range of pH 5.75-6.4 and the optimal pH was 5.75 with the titer of 1:512 in 76/118 and 1:256 in 79/90. In contrast, KSNUSD 84/34 strain of Seoul virus revealed hemagglutination at the range of pH 6.2-6.4 and the optimal pH was 6.4 with the titer of 1 : 64.

• Journal of Veterinary Clinics
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• v.15 no.1
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• pp.46-55
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• 1998

This study was performed to verify the effect of modified live virus vaccine against canine parvovirus (CPV) infection. Serum hemagglutination inhibition (Hl) test, histopathological and immunohistochemical techniques and polymerase chain reaction were used. The results were as follows: 1. During the experimental terms after vaccination, serum Hl titer was stable. Geometric mean titer (GMT) after the 1st vaccination was 280. After virulent CPV was challenged, GMT was 1,306. 2. After challenge by virulent CPV, the vaccinated group was not shown clinical signs and gross and histopathological findings. 3. After challenge by virulent CPV, the vaccinated group was not detected viral antigens in the small intestine immunohistochemically. 4. After challenge by violent CPV, the vaccinated group was not shown virus shedding in feces. In conclusions the overall results confirmed that modified live virus vaccine was effective on prevention of canine parvovirus infection.

• The Journal of Korean Society of Virology
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• v.30 no.2
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• pp.113-124
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• 2000

We had isolated 8 viruses from 91 specimen collected at southwest Cheju Province during early spring 1998 and 2 viruses from 9 specimen collected at Chung Nam Province during early spring 1999. To perform cross-reactivity among 4 mumps vaccine strains and 10 wild-type mumps viruse isolates, we immunized mice and took antisera against each virus. There were no antibody titer differences by indirect immunofluorescence assay (IFA), but most isolated mumps viruses showed a little cross-reactivities with Jeryl Lynn and Rubini strains. It has shown similar result by haemagglutination-inhibition (HAI) test. These results show that 4 mumps strains used as vaccine have the protection ability against endemic wild-type mumps viruses. Also the SH gene analysis was performed to identify genotypes. Most isolated mumps viruses belonged to genotype D. These results indicate that endemic mumps viruses in Korea are different to ones isolated in Japan and China.

• Journal of Veterinary Science
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• v.22 no.4
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• pp.56.1-56.10
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• 2021

Background: Fluorescent antibody virus neutralization (FAVN) test is a standard assay for quantifying rabies virus-neutralizing antibody (VNA) in serum. However, a safer rabies virus (RABV) should be used in the FAVN assay. There is a need for a new method that is economical and time-saving by eliminating the immunostaining step. Objectives: We aimed to improve the traditional FAVN method by rescuing and characterizing a new recombinant RABV expressing green fluorescent protein (GFP). Methods: A new recombinant RABV expressing GFP designated as ERAGS-GFP was rescued using a reverse genetic system. Immuno-fluorescence assay, peroxidase-linked assay, electron microscopy and reverse transcription polymerase chain reaction were performed to confirm the recombinant ERAGS-GFP virus as a RABV expressing the GFP gene. The safety of ERAGS-GFP was evaluated in 4-week-old mice. The rabies VNA titers were measured and compared with conventional FAVN and FAVN-GFP tests using VERO cells. Results: The virus propagated in VERO cells was confirmed as RABV expressing GFP. The ERAGS-GFP showed the highest titer (10^8.0 TCID₅₀/mL) in VERO cells at 5 days post-inoculation, and GFP expression persisted until passage 30. The body weight of 4-week-old mice inoculated intracranially with ERAGS-GFP continued to increase and the survival rate was 100%. In 62 dog sera, the FAVN-GFP result was significantly correlated with that of conventional FAVN (r = 0.95). Conclusions: We constructed ERAGS-GFP, which could replace the challenge virus standard-11 strain used in FAVN test.

• Journal of Preventive Medicine and Public Health
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• v.20 no.2 s.22
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• pp.280-286
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• 1987

For evaluating the boosting (anamnestic) effects of the most recent commercially produced plasma derived heat-inactivated hepatitis B vaccine (A. Co.), 117 adults with naturally acquired antibody to hepatitis B surface antigen (anti-HBs) were selected at random. In addition, out of case immunized at zero and 1 month, and boosted at 6 months (primary boosting) by conventional vaccine (B. Co), inactivated by pepsin digestion and formalin treatment, 11 cases who showed elevated titer after primary boosting were also submitted to the study. The results were as follows: 1) Out of the 117 subjects with naturally acquired anti-HBs, 6(5.1%) showed isolated anti-HBs and the titers were below 10 ratio units (RU). Negative seroconversion was seen in 4(3.4%) of the 117 cases at 12 months after the screening and, of these cases, 3 showed isolated anti-HBs and the titers were below 10 RU. 2) Eighty-three percent of the cases with naturally acquired isolated anti-HBs below 10 RU did not respond to a booster injection with 3 us dose of A. Co. vaccine at all, but 90% of the other subjects responded. 3) The anti-HBs titers of all the 11 cases who showed a rise of more than 10 RU (increased GMT, 28.04) at one month after primary booster injection by $20{\mu}g$ dose of B. Co. vaccine decreased at 19 months after the primary booster. And 3 subjects (27.3%) of the 11 reached negative seroconversion. All of the 11 cases, who had secondary booster injection with $3{\mu}g$ dose of A. Co. vaccine at 19 months after primary boosting, showed increased anti-HBs titer at least 20 RU or more (increased GMT, 57. 72) at one month after the boosting. According to the above results in the anti-HBs screening survey for the purpose of immunization with hepatitis B vaccine, subjects with isolated anti-HBs below 10 RU should be regarded as being in an unimmunized state. In cases who are in risk circumstances, immunized primarily with a $20{\mu}g$ dose of B. Co. vaccine, a secondary booster injection should be given within 2 years after initiation of primary immunization and a $3{\mu}g$ booster dose of A. Co. vaccine can be reliably used.

• Toxicological Research
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• v.17
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• pp.157-166
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• 2001

Almost all currently available retroviral vectors based on murine leukemia virus (MLV) contain one or more viral coding sequences. Because these sequences are also present in the packaging genome, it has been suggested that homologous recombination may occur between the same nucleotide sequence in the packaging genome and the vector, resulting in the production of replication competent retrovirus (RCR). Up until now, it has been difficult to completely remove viral coding sequences since some were thought to be involved in the optimum function of the retroviral vector. For example, the gag coding sequence present in almost all available retroviral vectors has been believed to be necessary for efficient viral packaging, while the pol coding sequence present in the highly efficient vector MFG has been thought to be involved in achieving the high levels of gene expression. However, we have now developed a series of retroviral vectors that are absent of any retroviral coding sequences but produce even higher levels of gene expression without compromising viral titer. In these vectors, the intron and exon sequences from heterologous cellular or viral genes are present. When compared to the well known MLV-based vectors, some of these newly developed vectors have been shown to produce significantly higher levels of gene expression for a longer period. In an experimental system that can maximize the production of RCR, our newly constructed vectors produced an absence of RCR. These vectors should prove to be safer than other currently available retroviral vectors containing one or more viral coding sequences.