• Journal of Microbiology and Biotechnology
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• v.27 no.9
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• pp.1701-1710
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• 2017

Classical swine fever virus (CSFV) is the etiologic agent of classical swine fever, a highly contagious disease that causes significant economic losses to the swine industry. The lapinized C-strain, a widely used vaccine strain against CSFV, has low growth efficiency in cell culture, which limits the productivity in the vaccine industry. In this study, a recombinant virus derived from C-strain was constructed and subjected to continuous passaging in PK-15 cells with the goal of acquiring a high progeny virus yield. A cell-adapted virus variant, RecCpp80, had nearly 1,000-fold higher titer than its parent C-strain but lost the ability to induce fever in rabbits. Sequence analysis of cell-adapted RecC variants indicated that at least six nucleotide changes were fixed in RecCpp80. Further adaption of RecCpp80 variant in swine testicle cells led to a higher virus yield without additional mutations. Introduction of each of these residues into the wild-type RecC backbone showed that one mutation, M979R (T3310G), located in the C-terminal region of E2 might be closely related to the cell-adapted phenotype. Rabbit inoculation revealed that $RecCpp40_{+10}$ failed to induce fever in rabbits, whereas $RecCpp80_{+10}$ caused a fever response similar to the commercial C-strain vaccine. In conclusion, the C-strain can be adapted to cell culture by introducing specific mutations in its E2 protein. The mutations in RecCpp80 that led to the loss of fever response in rabbits require further investigation. Continuous passaging of the C-strain-based recombinant viruses in PK-15 cells could enhance its in vitro adaption. The non-synonymous mutations at 3310 and 3531 might play major roles in the enhanced capacity of general virus reproduction. Such findings may help design a modified C-strain for improved productivity of commercial vaccines at reduced production cost.

• Korean Journal of Veterinary Research
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• v.47 no.4
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• pp.429-435
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• 2007

The risk of an outbreak of classical swine fever (CSF) was evaluated in relation to the vaccination and seroprevalence of antibodies. Blood samples were collected from 60 piggeries throughout Korea and information regarding CSF vaccination habits was also obtained via in-person interviews with pig farmers. The results of the survey indicated that 51 out of 60 farms were regularly performing CSF vaccinations in reproductive herds. Farmers preferred to vaccinate their reproductive pigs before weaning (41 farms) than on (9 farms) or after weaning (1 farm). In growing herds, however, double vaccinations as recommended were implemented for only 40 farms (66.7%) and vaccine schedules were identified as being frequently ignored. Moreover, many farms (18/40) were found to vaccinate earlier or later than the recommended time. According to antibody seroprevalence levels, only 36 farms (60%) were considered to be safe regarding potential risk for a CSF outbreak. Among the remaining pig farms, 6 were at low-risk (10%), 12 were at medium-risk (20%), and another 6 were at high-risk (10%). Antibody levels were found to be consistent with vaccination status obtained from personal interview surveys. Our findings demonstrate the importance of vaccinations regarding the prevention of a CSF outbreak, suggesting that vaccinations must be promoted toward pig raisers and practitioners.

• Journal of Microbiology and Biotechnology
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• v.14 no.3
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• pp.490-497
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• 2004

Although the E. coli heat-labile enterotoxin B subunit (LTB) is known to be a potent mucosal adjuvant towards co-administrated unrelated antigens and immunoregulator in T-helper 1-type-mediated autoimmune diseases, a more efficient and useful LTB is still required for prospective vaccine adjuvants. To determine whether a novel chimeric LTB subunit would produce an enhanced mucosal adjuvant activity and immune response, a number of LTB subunits were genetically fused with chimeric proteins using the epitope genes of the envelope glycoprotein E2 (gp51-54) from the classical swine fever virus (CSFV). It was found that the total serum immunoglobulin (Ig) levels of BALB/c mice orally immunized with chimeric proteins containing an N-terminal linked LTB subunit (LE1, LE2, and LE3) were higher than those of mice immunized with LTB, E2 epitope, and chimeric proteins that contained a C-terminal linked LTB subunit. In particular, immunization with LE1 markedly increased both the total serum Ig and fecal IgA level compared to immunization with LTB or the E2 epitope. Accordingly, the current results demonstrated that the LTB subunit in a chimeric protein exhibited a strong mucosal adjuvant effect as a carrier molecule, while the chimeric protein containing the LTB subunit stimulated the mucosal immune system by mediating the induction of antigen-specific serum Ig and mucosal IgA. Consequently, an LE1-mediated mucosal response may contribute to the development of effective antidiarrhea vaccine adjuvants.

• Korean Journal of Veterinary Service
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• v.44 no.4
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• pp.283-290
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• 2021

This is a study on the improvement of the chemical treatment method of the livestock carcass treatment newly introduced in the livestock infectious disease prevention method in order to improve the problems of the existing burial-centered carcass treatment method when a livestock infectious disease occurs. It was conducted to establish detailed treatment standards for the chemical treatment method of pig carcasses based on the results of proof of the absence of infectious diseases in pigs. After inoculating pig carcasses with 10 pathogens (6 viruses [FMDV, ASFV, CSFV, PCV2, PRRSV, PEDV] and 4 bacteria [Lawsonia intracellularis, Clostridium perfringens type C, E. coli, Salmonella Typhimurium]) It was treated at 90℃ for 5 hours in a potassium hydroxide (KOH) liquid solution corresponding to 15% of the body weight. This method liquefies all cadaveric components and inactivates all inoculated pathogens. Based on these results, it was possible to prove that chemical treatment of pig carcasses is effective in killing pathogens and is a safe method without the risk of disease transmission. Although there are problems to be solved in the processing and operation of the chemical treatment products of livestock carcasses, the chemical treatment method of livestock carcasses can be suggested as an alternative to the current domestic burial-centered livestock carcass treatment method, preventing environmental pollution, and contributing to public health.