Location: Foreign Animal Disease Research
Project Number: 8064-32000-060-31-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Oct 1, 2019
End Date: Jul 31, 2022
Classical swine fever (CSF) is one of the most important viral diseases of swine and poses a major health and trade problem for the pig industry. Porcine circovirus 2 b (PCV2b) also has a major economic impact in many pig-producing countries of the world including the US. PCV2b alone, in general, causes only a sub clinical disease, however its seroprevalence is very high worldwide. Previous studies have found that Pseudorabies Virus (PRV) can be used as an effective vaccine vector. This research project seeks to evaluate CSF subunit vaccines using Pseudorabies Virus (PRV) in term of efficacy in protecting pigs against infection with virulent virus strains. Specific objectives include: 1. Determine the nasal virus shedding property of rPrvtm Cap-Erns*-E2 vaccine virus in pigs following reactivation of the latent virus. 2. Evaluate the protective efficacy of the rPrvtmv Cap-Erns*-E2 vaccine in piglets against PCV2b. 3. Evaluate the protective immune resonse and DIVA property of the rPrvtmv Cap-Erns*-E2 vaccine in pigs against CSFV. 4. Determine the vaccine efficacy of rPrvtmv Cap-Erns*E2 in pigs against a virulent CSFV virus challenge.
1. To determine the nasal virus shedding property of the rPrvtmv Cap-Erns*-E2 vaccine virus in pigs following reactivation of the latent vaccine virus reactivation of latent rPrvtmv Cap-Erns*-E2 in the TG will be tested by Dexamethasone treatment followed by nasal virus shedding. 2. An evaluation of the protective efficacy of the rPrvtmv Cap-Erns*-E2 vaccine in piglets against PCV2b will be conducted. Immunization/challenge experiments will be conducted in pigs to evaluate the protective efficacy of rPrV-vectored vaccine against PCV2b. Based on a recent pilot study, rPrvtmv Cap-Erns*-E2 vaccine virus is highly attenuated and induced a relatively high neutralizing antibody by 7 days post vaccination. In this project, vaccinated pigs will be challenged with a field PCV2b isolate and the protection against PCV2b challenge will be judged by viraemia, nasal virus shedding, viral load and granular lesions in the tonsil, mediastinal, mesenteric and inguinal lymph nodes. 3. An evaluation of the protective immune response and DIVA property of the rPrvtmv Cap-Erns*-E2 vaccine in pigs against CSFV will be conducted. Sera collected from rPrvtmv Cap-Erns*-E2 vaccinated pigs above will be tested for CSFV virus-specific immune response by neutralizing antibody and CSFV E2 and Erns-specific ELISA test. In addition, a commercially available NS3 competive NS3 ELISA kit based on BVDV NS3 (Prionics AG, ID Vet, Boehringer Ingelheim) will be used to determine DVA property of the rPrvtmv Cap-Erns*-E2 in the vaccinated pigs. If needed, we will develop our own CSFV NS3 based DIVA test and the sensitivity and specificity the commercial and in-house NS3 DIVA test will be compared and/or validated. 4. Vaccine efficacy of rPrvtmv Cap-Erns*-E2 in pigs against a virulent CSFV virus challenge will be determined. Immunization/challenge experiments will be conducted in pigs to evaluate the protective efficacy of rPrV-vectored vaccine against a virulent wt CSFV (Brescia strain) challenge. Protection will be judged by the absence of clinical disease and viremia following challenge in the vaccinated pigs, generation of protective levels of CSFV-E2 and Erns-specific neutralizing antibody titers and cellular immune responses by 7 and 21 days post vaccination.