• Korean Journal of Veterinary Research
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• v.42 no.2
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• pp.241-251
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• 2002

Modified-live (ML) infectious laryngotracheitis (ILT) vaccines have been widely used as a preventive measure in Korea since the first outbreak of ITL. Recently, it has been observed that chickens vaccinated with the commercially available ML ILT vaccine have sometimes exhibited adverse clinical signs. In this study, we evaluated the quality of the vaccines by comparing titer of each vaccine batch and testing the stability of ILT virus (ILTV) in vaccine diluents and compared the safety and efficacy of vaccines in specific pathogen free (SPF) chickens. The ratio of maximum titer to minimum titer of vaccine produced by most manufacturers was 2 to 15. However, 2 out of 11 manufacturers produced vaccines of which the ratio was 74 to 478. Most vaccines examined were maintained vaccine titers suitable for national regulations within expiry date. However, some vaccines did not keep the titer required for the national regulations. In the test for stability of ILTV in various diluents, ILTV was highly stable in lactose-phosphate-glutamine-gelatin solution, sucrose-phophate-glutamine-albumin solution and some vaccine diluents produced by manufacturers. The safety of ML ILT vaccines was assessed in 10-day-old SPF chicks. Mortality in SPF chicks inoculated intratracheally with one dose of vaccine varied depending on vaccines and some vaccines produced 50-85% mortality. Seven-week-old SPF chickens were vaccinated intraocularly with ML ILT vaccines and then challenged intratracheally with ILT challenge virus 14 days after vaccination. The protection rate was assessed by clinical signs and reisolation of the ILT challenge virus from tracheas taken at day 4 after challenge. There were slight respiratory reactions in some vaccinated chickens after vaccination but these reactions disappeared within 5 days after vaccination. No further clinical signs and death were observed. Protection rate determined by clinical signs and mortality was 100% in all vaccinated groups. However, the challenge virus was isolated from all tracheas of chickens vaccinated with vaccine B or control groups. The challenge virus was also isolated in the trachea of one in five chickens vaccinated with either vaccine F or K, but not in tracheas of chickens vaccinated with other vaccines. In the present study, the stability of vaccine diluents, pathogenicity and protection rate based on reisolation test of the challenge virus were different depending on vaccines produced by eleven manufacturers.

• Korean Journal of Veterinary Service
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• v.35 no.3
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• pp.169-174
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• 2012

Japanese encephalitis virus (JEV) is one of the main causes of viral encephalitis in human and animals. For over 30 years, a live attenuated JEV vaccine strain has been used in the veterinary field, and it is required to conduct quality evaluation studies on the commercial vaccines. For the quality control of live attenuated JEV vaccine, we investigated the nucleotide sequence similarity of prME gene derived from five JEV vaccines commercially available in pigs in Korea. The Vero cells infected with JEV vaccines showed specific cytopathic effect, which was characterized by rounding and detached cells. In the phylogenetic analysis, all of the vaccine strains showed a close relationship with the original vaccine seed strain (Anyang 300) and clustered into the genotype 3. In comparison of the nucleotide and deduced amino acid sequences of prME genes with the original strain, all JEV vaccine strains showed high amino acid similarity ranging from 98.9% to 99.5%, but had several point mutations, probably due to high mutation rates of viral RNA polymerase by several virus passages. Even though the current JEV vaccine strains have been maintained and produced for a long period of time, the genetic characterization of them have been rarely changed. However, since the mid 1990's, molecular epidemiology of JEV has been changed sharply from genotype 3 to genotype 1 in Korea, further studies on new vaccine strains to genotype 1 is required for more effective prevention in the field.

• 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.

• 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 Service
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• v.16 no.1
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• pp.76-81
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• 1993

To evaluate the pathogenesis of live infectious laryngotracheitis vaccine, virus, virus and E.coli were inoculated in 4-weeks old intraorbitally and intraorally. Their pathology and serology were studied. The results were as follows. 1. thicks Inoculated with ILT vaccine alone showed no clinical sign. 2. Some of chicks inoculated with ILT vaccine followed by E.coli after 1day showed nasal discharge and cough. 3. Some of chicks inoculated with E. coli followed by ILT vaccine after 1 day and inoculated ILT vaccine and E.coli concurrently, showed nasal discharge. 4. Serum neutralization titers of chicks inoculated with ILT vaccine increased 3 weeks after Inoculation, peaked at 7 to 8 weeks and decreased. 5. Antibiotic sensitivity of E.coli were higher in Enrofloxacin (Baytril) and chloramphenical.

• Parasites, Hosts and Diseases
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• v.61 no.3
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• pp.231-239
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• 2023

Toxoplasma gondii is an intracellular parasitic organism affecting all warm-blooded vertebrates. Due to the unavailability of commercialized human T. gondii vaccine, many studies have been reported investigating the protective efficacy of pre-clinical T. gondii vaccines expressing diverse antigens. Careful antigen selection and implementing multifarious immunization strategies could enhance protection against toxoplasmosis in animal models. Although none of the available vaccines could remove the tissue-dwelling parasites from the host organism, findings from these pre-clinical toxoplasmosis vaccine studies highlighted their developmental potential and provided insights into rational vaccine design. We herein explored the progress of T. gondii vaccine development using DNA, protein subunit, and virus-like particle vaccine platforms. Specifically, we summarized the findings from the pre-clinical toxoplasmosis vaccine studies involving T. gondii challenge infection in mice published in the past 5 years.

• IMMUNE NETWORK
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• v.12 no.1
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• pp.8-17
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• 2012

Background: Respiratory syncytial virus (RSV) is a major cause of severe lower respiratory tract diseases in infancy and early childhood. Despite its importance as a pathogen, there is no licensed vaccine against RSV yet. The attachment glycoprotein (G) of RSV is a potentially important target for protective antiviral immune responses. Recombinant baculovirus has been recently emerged as a new vaccine vector, since it has intrinsic immunostimulatory properties and good bio-safety profile. Methods: We have constructed a recombinant baculovirus-based RSV vaccine, Bac-RSV/G, displaying G glycoprotein, and evaluated immunogenicity and protective efficacy by intranasal immunization of BALB/c mice with Bac-RSV/G. Results: Bac-RSV/G efficiently provides protective immunity against RSV challenge. Strong serum IgG and mucosal IgA responses were induced by intranasal immunization with Bac-RSV/G. In addition to humoral immunity, G-specific Th17- as well as Th1-type T-cell responses were detected in the lungs of Bac-RSV/G-immune mice upon RSV challenge. Neither lung eosinophilia nor vaccine-induced weight loss was observed upon Bac-RSV/G immunization and subsequent RSV infection. Conclusion: Our data demonstrate that intranasal administration of baculovirus-based Bac-RSV/G vaccine is efficient for the induction of protection against RSV and represents a promising prophylactic vaccination regimen.

• IMMUNE NETWORK
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• v.14 no.4
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• pp.207-218
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• 2014

Chronic virus infection leads to the functional impairment of dendritic cells (DCs) as well as T cells, limiting the clinical usefulness of DC-based therapeutic vaccine against chronic virus infection. Meanwhile, B cells have been known to maintain the ability to differentiate plasma cells producing antibodies even during chronic virus infection. Previously, ${\alpha}$-galactosylceramide (${\alpha}GC$) and cognate peptide-loaded B cells were comparable to DCs in priming peptide-specific $CD8^+$ T cells as antigen presenting cells (APCs). Here, we investigated whether B cells activated by ${\alpha}GC$ can improve virus-specific T cell immune responses instead of DCs during chronic virus infection. We found that comparable to B cells isolated from naïve mice, chronic B cells isolated from chronically infected mice with lymphocytic choriomeningitis virus (LCMV) clone 13 (CL13) after ${\alpha}GC$-loading could activate CD1d-restricted invariant natural killer T (iNKT) cells to produce effector cytokines and upregulate co-stimulatory molecules in both naïve and chronically infected mice. Similar to naïve B cells, chronic B cells efficiently primed LCMV glycoprotein (GP) 33-41-specific P14 $CD8^+$ T cells in vivo, thereby allowing the proliferation of functional $CD8^+$ T cells. Importantly, when ${\alpha}GC$ and cognate epitope-loaded chronic B cells were transferred into chronically infected mice, the mice showed a significant increase in the population of epitope-specific $CD8^+$ T cells and the accelerated control of viremia. Therefore, our studies demonstrate that reciprocal activation between ${\alpha}GC$-loaded chronic B cells and iNKT cells can strengthen virus-specific T cell immune responses, providing an effective regimen of autologous B cell-based therapeutic vaccine to treat chronic virus infection.

• IMMUNE NETWORK
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• v.5 no.2
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• pp.89-98
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• 2005

Background: DNA vaccination represents an anticipated approach for the control of numerous infectious diseases. Used alone, however, DNA vaccine is weak immunogen inferior to viral vectors. In recent, heterologous prime-boost vaccination leads DNA vaccines to practical reality. Methods: We assessed prime-boost immunization strategies with a DNA vaccine (minigene, $gB_{498-505}$ DNA) and recombinant vaccinia virus $(vvgB_{498-505})$ expressing epitope $gB_{498-505}$ (SSIEF ARL) of CD8+ T cells specific for glycoprotein B (gB) of herpes simplex virus (HSV). Animals were immunized primarily with $gB_{498-505}$ epitope-expressing DNA vaccine/recombinant vaccinia virus and boosted with alternative vaccine type expressing entire Ag. Results: In prime-boost protocols using vvgBw (recombinant vaccinia virus expressing entire Ag) and $vvgB_{498-505}$, CD8+ T cell-mediated immunity was induced maximally at both acute and memory stages if primed with vvgBw and boosted with $vvgB_{498-505}$ as evaluated by CTL activity, intracellular IFN-staining, and MHC class I tetramer staining. Similarly $gB_{498-505}$ DNA prime-gBw DNA (DNA vaccine expressing entire Ag) boost immunization elicited the strongest CD8+ T cell responses in protocols based on DNA vaccine. However, the level of CD8+ T cell-mediated immunity induced with prime-boost vaccination using DNA vaccine expressing epitope or entire Ag was inferior to those based on vvgBw and $vvgB_{498-505}$. Of particular interest CD8+ T cell-mediated immunity was optimally induced when $vvgB_{498-505}$ was used to prime and gB DNA was used as alternative boost. Especially CD7+ T cell responses induced by such protocol was longer lasted than other protocols. Conclusion: These facts direct to search for the effective strategy to induce optimal CD8+ T cell-mediated immunity against cancer and viral infection.

• The Journal of Korean Society of Virology
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• v.29 no.4
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• pp.211-219
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• 1999

Most of the currently licensed viral and bacterial vaccines produced in the world are in state of antigen suspension and the immunogenicity of vaccines could be maintained for one or two years only by keeping in the refrigerator, but without refrigeration vaccines would easily lose their immunogenicites. In this study, as a step to develope the method of increasing the stability of vaccines and maintaining the immunogenicity of vaccines for a long time at room temperature or higher temperature, trehalose, glucose and lactose at different concentration were added into the Hantaan virus vaccines and then kept at $37^{\circ}C$ for 12, 24, 48 hours and at room temperature for seven days respectively. Treated vaccines were then inoculated respectively into ICR mice and the titers of antibody against the antigen of Hantaan virus from the mice sera were evaluated. Vaccine without sugar lost immunogenicity completely in 24 hour at $37^{\circ}C$, but the vaccines containing trehalose could maintain some of the immunogenicity even after exposure at $37^{\circ}C$ for 48 hours and the best concentration of trehalose for maintaining the immunogenicities of vaccines was $7.5{\sim}10$ percent. The results suggest that addition of trehalose could increase the stability of Hantaan virus vaccine.