Recipient Organization
NORTH DAKOTA STATE UNIV
1310 BOLLEY DR
FARGO,ND 58105-5750
Performing Department
(N/A)
Non Technical Summary
The vast genetic and antigenic variability of viruses like the porcine reproductive and respiratory disease syndrome virus (PRRSV) and influenza pose a long-standing challenge in the field of vaccinology. The phenomenon of antibody based immunodominance, wherein the infecting virus directs the immune system to produce wasteful rather than protective antibody responses to escape host immunity, also serves as a major confounding factor for effective vaccine development. Further, the early undermining of the immune response results in the amplification of the suboptimal response with every subsequent infection or booster vaccination, thus increasingly diminishing vaccine efficacy against newly emerging variants with age.Therefore, a major goal of this project is to rationally re-engineer the immunodominance patterns of selected PRRSV vaccine antigens to improve the quality of the antibody response of PRRSV vaccines. A secondary goal of the project is to develop the PRRSV vaccine as a delivery system for other swine viral vaccine antigens, to reduce the cost and effort associated with vaccination. Porcine circovirus type 3 is a newly emerged swine virus which also causes reproductive and respiratory disease in pigs. It is very frequently co-detected with PRRSV. Hence, the rationally designed PRRSV vaccine will be engineered to also deliver the PCV3 vaccine antigen simultaneously to vaccinated pigs. To test the dual PRRSV-PCV3 vaccine, groups of pigs will be vaccinated with the construct, while control pigs will either remain unvaccinated or receive a commercial vaccine. After allowing time for the development of the immune response, the vaccinated pigs will be exposed to PRRSV and PCV3 viruses. It is expected that vaccination will result in protection against PRRSV disease manifestations and elicit improved anti-PRRSV antibody responses, and that vaccinated pigs will also be protected against PCV3 replication and pathology. We expect that the project outcomes will significantly improve PRRSV vaccine performance, provide a template for improving current vaccines against genetically variable viruses and develop the PRRSV vaccine as a delivery system for multiple swine infections.
Animal Health Component
30%
Research Effort Categories
Basic
40%
Applied
30%
Developmental
30%
Goals / Objectives
Porcine reproductive and respiratory disease syndrome virus (PRRSV) and porcine circovirus type 3 (PCV3) are two economically important swine viruses that cause respiratory distress and reproductive failure in production swine. Both viruses are very frequently co-detected in cases of reproductive failure in the field. Currently, commercial PCV3 vaccines are not available. Despite significant investment, efficacy and safety of current PRRSV vaccines remain questionable. The primary goals of this project are to improve current PRRSV vaccine performance and use the improved PRRSV vaccine as a vector to also deliver a PCV3 vaccine antigen, to protect against both viruses simultaneously. Specifically, the PRRSV vaccine will consist of a rationally re-structured modified live vaccine (rsPRRSV -MLV) in which selected PRRSV antigens are modified to alter immuno-dominance patterns of antigenic epitopes in such a manner that antibody responses are refocused towards protective epitopes rather than immunodominant, decoy epitopes. Additionally, the PCV3 capsid protein will be cloned and expressed from the re-engineered PRRSV backbone, to develop a dual PCV3 and PRRSV vaccine (rsPRRSV-PCV3 MLV). Thus, the major goals of the project will be toAim1: To assess the efficacy of the rsPRRSV-PCV3 MLV in protection againstObjective 1.1: Restructuring PRRSV antigens: Selected mutations of the PRRSV GP5, GP3 and GP4 proteins and expression of the PCV3 capsid antigen from the PRRSV vaccine backbone will be undertaken to develop the rsPRRSV-PCV3 MLV.Objective 1.2: Immunization and challenge of pigs: The efficacy and safety of rsPRRSV-PCV3-MLV in preventing PRRSV will be evaluated using a piglet vaccination and challenge model. Objective 1.3: Antibody responses: The quality of the neutralizing antibody responses to rsPRRSV-PCV3-MLV will be evaluatedObjective 1.4: Cell mediated immune response: PRRSV-specific cell mediated immune responses will be evaluatedAim2: To assess the efficacy of the rsPRRSV-PCV3 MLV in protection against PCV3Objective 2.1: Immunization and challenge of pigs: The efficacy and safety of rsPRRSV-PCV3-MLV in preventing PCV3 or combined PRRSV+PCV3 infection will be evaluated using a piglet vaccination and challenge model.Objective 2.2: Immune responses to rsPRRSV-PCV3-MLV. PCV3-specific antibody and cell mediated immune responses to vaccination will be evaluated.
Project Methods
1.The rational re-engineering of the PRRSV vaccine will be achieved using a PRRSV infectious clone as the backbone and introduction of mutation by conventional site directed mutagenesis or overlap extension PCR. For difficult segments, the required sequence may be synthesized and cloned into the backbone by restriction digestion. Evaluation of the cloning process will be achieved by sequencing and assessing the reactivity to antibodies. The PCV3 capsid will be cloned by PCR and restriction digestion and evaluated by reactivity to antibodies.2 To assess vaccine efficacy and safety, groups of pigs will be vaccinated with either the experimental vaccine or a commercial control vaccine or remain as unvaccinated controls. Following a 4-week post vaccination period, the pigs will be challenged with PRRSV or PCV3 or both. The efficacy of the vaccine will be evaluated by measuring antibody responses, cell mediated immune responses, inhibition of viral replication and prevention of tissue pathology in comparison to the commercial vaccine and unvaccinated pigs.3.The improvement in the quality of the antibody response due to the re-engineering will be evaluated by epitope specific measurements of the quantity and quality of antibody responses to the specific epitopes by ELISA or Raman spectroscopy.