• Korean Journal of Animal Reproduction
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• v.21 no.4
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• pp.397-403
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• 1997

For the ultimate goal of efficient retrovirus vector-mediated transgenic animal production, we tried to increase virus titer by employing three methods: boosting virus production by treating virus-producing cells with sodium butyrate, concentration of virus stock by either filtration or ultracentrifugation. Compared to the control, applications of sodium butyrate (5 mM) treatment and filtration resulted in only 3 and 3. 6 folds of titer increases on bovine EBTr target cells, respectively. However, concentration of virus-containing medium by ultracentrifugation showed 12.5 folds of titer increase compared to the control (10${\times}$10$^5$ LacZ$^+$ TU Im), indicating the best method which can enhance retrovirus vector-mediated transgenic animal production.

• Korean Journal of Veterinary Research
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• v.50 no.3
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• pp.205-211
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• 2010

Fifty young calves, about five to six months old purchased from nation-wide were investigated with the prevelance of neutralizing antibody (Ab) of infectious bovine rhinotracheitis virus (IBRV), parainfluenza 3 virus ($PI_{3}V$), bovine viral diarrhea virus (BVDV) and bovine respiratory syncytial virus (BRSV). The positive detection ratio of neutralizing Ab against IBRV was only 3% and two of positive samples showed low antibody titer (below 2). Ab against BRSV showed 48% of positive ratio and among 24 positive samples, antibody titer of 23 samples were below 3. But in the case of BVDV, 68% of samples were positive and 23 samples appeared to possess high antibody titer, above 4 and the antibody titer of five samples were above 8. The highest positive result came from $PI_{3}V$. The positive ratio in the samples investigated in this study was 72%, but the antibody titer of positive samples were generally below 3 (77.8% in positive samples).

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.315-319
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• 2003

A novel method is developed to yield virus titers in 10 h, is easy to .perform using 96-well plates, and applicable to both any Autographa californica nucleopolyhyderovirus (AcNPV) and Bombyx mori nucleopolyhedrovirus (BmNPV)-based recombinant baculovirus. This assay uses an antibody to a DNA-binding protein to detect the infected cells via immune-staining. The titer is determined by counting foci produced due to infection of virus under a fluorescent microscopy. The required incubation period was shortened considerably because infected cells expressed viral antigens at the post infection time of 4 h. Therefore, 10 hours were enough to estimate the virus titer including virus infection time, insect cell culture, and estimation of virus titer.

• Journal of fish pathology
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• v.28 no.2
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• pp.113-116
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• 2015

A $0.45-{\mu}m$ membrane filter is generally used to remove bacterial contamination during virus extraction from fish samples. However, the number of fish viruses is drastically reduced after filtration with a $0.45{\mu}m$ filter. In this study, we investigated the effect of filters on virus infectivity titer and the change in virus titer and bacterial number following different centrifugation conditions to determine a suitable procedure for virus extraction from fish samples. $10^{4.05}$ and $10^{5.05}TCID_{50}/ml$ of infectious hematopoietic necrosis virus (IHNV) and $10^{4.05}$ and $10^{4.55}TCID_{50}/ml$ of Oncorhynchus masou virus (OMV) were not detectable after filtration with two types of $0.45-{\mu}m$ filters, except the IHNV titer was reduced by about 10 fold after filter use (company A). No significant difference was found in the virus titer following centrifugation at $880{\times}g$ (30 min) or $3,500{\times}g$ (30 min), whereas IHNV and OMV titers were reduced by about 10 and 10-1000 fold by centrifugation at $14,000{\times}g$ (30 min) and $14,000{\times}g$ (10 and 30 min), respectively. A total of 97.7-99.9% Escherichia coli were eliminated by centrifugation at $880 {\times}g$ (30 min) and $3,500{\times}g$ (30 min). These results show that fish viruses were affected by filtering, even though the effect differed by virus species and filter type. Therefore, centrifugation at $3,500{\times}g$ (30 min) and use of medium with antibiotics may be useful for virus extraction along with a reduction in bacteria.

• Korean Journal of Veterinary Service
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• v.20 no.1
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• pp.127-129
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• 1997

The cattle serum was investigated many cases of deformity calf in kyung-ju area. The serum antibody titer of Aino virus, which was not reported in domestic, was showed 3 cattle to ${\times}$2~64.

• Journal of Microbiology and Biotechnology
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• v.10 no.5
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• pp.728-732
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• 2000

Propagation of Anagrapha falcifera nuclear polyhedrosis virus(AfNPV) was investigated using well-plates and split-flow air-lift bioreactors. In well-plate experiments, the effects of pH, cell density at a point of infection, serum concentration, DEAE-dextran, and lipid on virus propagation were all closely examined. The AfNPV titer in well-plates was optimal at pH 6.8 and $3{\times}10^6$ cells/$cm^2$. The virus titer was not dramatically affected when the fetal bovine serum concentration was reduced from 10% to 5%. The addition of cholesterol at AfNPV infection of Sf21 cells enhanced the virus titer, whereas the addition of DEAE-dextran did not improve the titer. The AfNPV titer ($3.8{\times}10^7$ $TCID_{50}/ml$) at optimized conditions for well-plate experiments was 2.5-fold higher than for the control. In bioreactor experiments, the AfNPV titer showed its maximum level at air flow rates of 20-40 ml/min. In a split-flow air-lift bioreactor, AfNPV titer ($2.3{\times}10^7\;TCID_{50}/ml$) was 1.5-fold higher than the control when the culture was at pH 6.8 and supplemented with 0.34 mM cholesterol.

• Korean Journal of Veterinary Service
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• v.26 no.3
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• pp.215-219
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• 2003

This study was conducted to investigate the similarity between hemagglutination inhibition (HI) test and enzyme-linked immunosorbent assay(ELISA) titers and sample to positive ratio (S/P ratio) of Newcastle disease(ND) virus. To perform this study, the 372 sera of broiler chicks and 120 sera of layers and breed chicks were collected from slaughter house and farms, respectively. As a result of HI test out of different chicks, the positive percentage of ND antibody titer of broiler, layer and breeder, when a standard positive HI titer were '2', was 84.4%, 100% and 100%, respectively. The positive percentage of ND antibody titer by ELISA was shown 38.4%, 100% and 100% and S/P ratio were also shown 81.5%, 98.2% and 99.2%, respectively. The results of comparative survey with same sera by two experimental methods were as follows; In low HI titer, ELISA titer was not similar to HI titer, but S/P ratio was similar to it. In high HI titer, ELISA titer was not similar to HI titer. Therefore, HI titer was more similar to S/P ratio than ELISA titer.

• The Journal of Korean Society of Virology
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• v.29 no.1
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• pp.33-38
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• 1999

Retroviral vector provide a highly efficient method for gene transfer into eukaryotic cells. This vector system can be divided into two components; the retroviral vector itself and the retroviral packaging cell line. The key improvement in the design of these two components are, focused on two aspects; the reduction of helper virus production and high titer-virus. We used PA317 for retrovirus packaging cell line, for its high producibility of viral titer. To test the ability of the vectors to generate high titer-virus, we have chosen four different retroviral vectors; LN, LNSX, LNCX and LXSN. To test easily the viral titer, we have made recombinant construction with CD4 and CD8, checked their viral titer and stained their surface expression. LXSN which contain SV40 early promoter in front of neo gene showed best results in viral transient transfection assay, dot blot assay and surface expression. In addition, recombinant containing CD8 generally showed much higher viral titration and surface expression than CD4.

• Korean Journal of Veterinary Research
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• v.1 no.1
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• pp.36-53
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• 1961

This experiment was conducted on the fowl pox embryo vaccine for the production immunity, and stability, using an attenuated fowl pox virus (Nakano strin). Burnet's window method was applied, that is, 0.1 ml. of seed virus was inoculated on the chorioallantoic membrane of 12-day old chicken embryos, and incubated for 5 to 6 day, and then the result were read. Four kinds of suspensions of different embyo tissue were prepared and tested for the infectivity in chickens. Finally the suspension of chorioallantoic membrane was used as the vaccine throughout the experiment. Results obtained in this experiment are summarized as follows: (1) Of embryo tissue infected with the vaccine virus, chorioallantoic membrane had the highest virus titer of $10^{-5.4}$ $EID_{50}$, and albumen the lowest titer of $10^{-0.7}$ $EID_{50}$. (2) Suspensions of infected whole embryo with or without saline, and de-embryonated whole egg had about the same virus titer of $10^{-4.4}$ $EID_{50}$, whereas the chorioallantoic membrane had $10^{-5.7}$ EID 50 or higher. The virus titer droped one log from $EID_{50}$ when inoculated into chickens. Takes were observed 35.6% of 500 chickens by stick method and 89% of 500 chickens by brush method. (3) The chorioallantoic membrane conferred almost perfect immunity for chickens by 10 days after vaccination. (4) Satisfactory immunity was observed in the chickens when eruption in a single follicle. (5) Eight of 10 vaccinated chickens revealed durable immunity for 307 days following vaccination. (6) The vacuum-dried vaccine maintained its infectiviy for 899 days at $5^{\circ}C$ or below and maintained the vius titer of $10^{-3.6}$ $EID_{50}$. On the other hand, non-desiccated wet vaccine maintained the titer of $10^{-3.0}$ $EID_{50}$ for 50 days of preservation period at $5^{\circ}$. However, in 50% glycerin-saline the infectivtiy of the same wet vaccine dropped to $10^{-1.5}$ $EID_{50}$ (7) The vartation of virus titer of the vaccine before and after desiccation was $10^{-0.5}$ $EID_{50}$ on the average. (8) As suspending media, 0.85 per cent saline and distilled water showed nearly the same effect on the infectivity of the vaccine by retaining the titer $10^{-3.0}$ $EID_{50}$ after 50 days of preservation both at $5^{\circ}C$ and $20^{\circ}C$, while 50 percent cent glycerine-saline dropped the titer to $10^{-2.5}$ EID and $10^{-1.5}$ $EID_{50}$ respectively at $5^{\circ}C$ and $2^{\circ}C$ after the same period.

• The Journal of Korean Society of Virology
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• v.26 no.1
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• pp.67-76
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• 1996

The methods that make Hantavirus grow consist of inoculation into the experimental animals and cultured cells. The cultured cells, such as Vero-E6 and A549 cells, have been usually used for isolation of the virus and the animals, such as mice and rats, are used for large scale preparation of the virus so far. Furthermore, the cell can be used to maintain the virus and assay the infectivity and the animals can be used for the experiment of viral pathogenicity and challenge for assessment of vaccine. Apodemus mice, the own natural host of the virus, has been used for challenge test of Hantaan virus. However it has been pointed out to difficult handling and breeding the animal in laboratory. Therefore, we attempted to establish a new animal model for challenge test at the time of isolation of Maaji virus which is a new hantavirus similar but distinct to Hantaan virus. In suckling hamster, the titer of Maaji virus and the lethality to mice of the virus were increased gradually in the titer and lethality through passage by intracerebral (IC) inoculation. We tried to re-adapt this brain virus to lung of weanling hamster. The brain passaged virus was inoculated into weanling hamster intramuscularly. Again, the titer of the virus in lung was also increased by continuous passage of this virus. This facts could regarded as adaptation to new environment in which the virus proliferates. To identity the virus passaged in hamster with Maaji virus, both of the virus passaged in hamster brain and lung were compared with Maaji virus (MAA-I) and Hantaan virus (HTN 76-118) by means of restriction fragment length polymorphism (RFLP) and slingle strand conformation polymophism (SSCP). As a result, we conclude that Maaji virus could be adapted successfully to weanling hamster through this passage strategy. Utilizing this adapted Maaji virus strain, hamster model is able to be used for challenge test in hantaviral vaccinology and further experiments utilizing hamster system as a rather available and convenient lab animal are expected.