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Establishment of a method for evaluation of the efficacy of a classical swine fever virus subunit vaccine in rabbits

Zhi Cao DVM1,2, Heng Zhang MVSc2, Qian Yang DSc1, Hui Zhang MSc2, and Gencheng Fan DVM2
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  • 1 1Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, 266071 China.
  • | 2 2State Key Laboratory of Animal Genetic Engineering Vaccine, Yebio Bioengineering Co Ltd of Qingdao, Qingdao, 266114 China.

Abstract

OBJECTIVE

To establish a method for evaluation of the efficacy of a classical swine fever virus (CSFV) subunit vaccine in rabbits as determined via humoral immune responses to the virus.

ANIMALS

40 specific pathogen–free rabbits.

PROCEDURES

Rabbits were randomly assigned to 4 groups (10 rabbits/group) for SC injection of 0.05, 0.1, and 0.2 mL of a CSFV subunit E2 vaccine (representing 1.15, 2.3, or 4.6 μg of E2 protein/dose, respectively) or saline (0.9% NaCl) solution. Blood samples were collected 21 days after vaccination for measurement of the antibody response against CSFV via ELISA and virus neutralization methods. On the same day, the CSFV Chinese (C) strain was injected into an ear vein. Vaccine efficacy was determined by monitoring of rabbits for pyrexia for 4 days and measurement of viral copies in spleen lysates at the end of the study. Reproducibility of the antibody response was tested with 2 other batches of the vaccine at the minimum immunization dose identified for the initially tested batch.

RESULTS

The E2 protein dose of the initially tested vaccine was positively correlated with the antibody response and protection rate in rabbits. The identified minimum immunization dose per rabbit was 0.1 mL, representing an E2 protein content of approximately 2.3 μg, and reproducibility of the antibody response to vaccination with the 2 other batches at this dose was good.

CONCLUSIONS AND CLINICAL RELEVANCE

A method was established in rabbits for evaluation of the efficacy of a CSFV subunit vaccine that could help in the optimization of later large-scale vaccine production and quality control processes as well as in the clinical application of the vaccine.

Abstract

OBJECTIVE

To establish a method for evaluation of the efficacy of a classical swine fever virus (CSFV) subunit vaccine in rabbits as determined via humoral immune responses to the virus.

ANIMALS

40 specific pathogen–free rabbits.

PROCEDURES

Rabbits were randomly assigned to 4 groups (10 rabbits/group) for SC injection of 0.05, 0.1, and 0.2 mL of a CSFV subunit E2 vaccine (representing 1.15, 2.3, or 4.6 μg of E2 protein/dose, respectively) or saline (0.9% NaCl) solution. Blood samples were collected 21 days after vaccination for measurement of the antibody response against CSFV via ELISA and virus neutralization methods. On the same day, the CSFV Chinese (C) strain was injected into an ear vein. Vaccine efficacy was determined by monitoring of rabbits for pyrexia for 4 days and measurement of viral copies in spleen lysates at the end of the study. Reproducibility of the antibody response was tested with 2 other batches of the vaccine at the minimum immunization dose identified for the initially tested batch.

RESULTS

The E2 protein dose of the initially tested vaccine was positively correlated with the antibody response and protection rate in rabbits. The identified minimum immunization dose per rabbit was 0.1 mL, representing an E2 protein content of approximately 2.3 μg, and reproducibility of the antibody response to vaccination with the 2 other batches at this dose was good.

CONCLUSIONS AND CLINICAL RELEVANCE

A method was established in rabbits for evaluation of the efficacy of a CSFV subunit vaccine that could help in the optimization of later large-scale vaccine production and quality control processes as well as in the clinical application of the vaccine.

Contributor Notes

Address correspondence to Dr. Cao (cz_ndnxy@126.com).