Date Full Report Received12/01/2014
Date Abstract Report Received12/01/2014
Funded ByNational Pork Board
Porcine Reproductive and Respiratory Syndrome (PRRS) is a chronic and economically important viral disease of pigs. Currently used PRRS virus (PRRSV) vaccines have failed to completely protect against reinfections. In addition, reports of live virus vaccine acting as a source of revertant virus resulting in catastrophic consequences is a concern. Although available killed PRRSV vaccines are safe, but their efficacy is poor. Thus, there is a pressing need of developing a safe and protective killed PRRSV vaccine to protect pigs from PRRS outbreaks. Virus-like-particles (VLPs) constitutes a specific class of subunit vaccine that mimic the structure of authentic virus particles. The VLPs function as effective and safe antigens in the absence of viral genome and potentially toxic (immunosuppressive) viral gene products. Nanotechnology based vaccine delivery is one of the important research endeavors of the 21st century. Nanoparticles made of biodegradable and biocompatible polymers [e.g. PLGA [poly(lactide co-glycolide)] are approved by FDA to use in vaccine delivery systems. Our hypothesis is that delivery of PLGA nanoparticle-entrapped PRRSV-VLPs vaccine elicits cross-protective immune response in pigs, with increased clearance of challenged virulent heterologous PRRSV. Our three Objectives are: (i) To prepare PRRSV-VLPs to one each of North American and European PRRSV strains; (ii) To develop and characterize candidate PLGA nanoparticle-entrapped PRRS-VLPs vaccine; and (iii) To evaluate cross-protective efficacy of Nano-PRRSV-VLPs vaccine in pigs. Until now only two reports on PRRS-VLPs are available which made use of only two PRRSV membrane proteins, and their efficacy as a candidate vaccine was not evaluated in pigs. Since putative PRRSV neutralizing and T-cell epitopes and are not limited to two proteins, we believe that PRRS-VLPs comprising of 5-6 viral membrane proteins serve as a potent candidate vaccine. In our study, we cloned the six PRRSV membrane protein genes in to a baculovirus vector system and generated individual recombinant baculoviruses (rBVs). To generate PRRS-VLPs, we coinfected insect cells with different combinations of rBVs and observed VLPs of approximately 50nm size only when GP5-M and E protein are in the formulation. In a pilot pig vaccine trial, PRRS-VLPs entrapped in PLGA nanoparticles and coadministered intranasally twice with a potent mucosal adjuvant, Mycobacterium tuberculosis whole cell lysate, and challenged with a virulent heterologous PRRSV strain 1-4-4 was evaluated. Analysis of viremia suggested the reduced challenged viral RNA load and infectious virus in pigs received PRRS-VLPs irrespective of entrapment in NPs, while in the lungs without NPs encasing PRRS-VLPs helped to significantly reduce the viral load. In conclusion, we generated PRRS-VLPs containing all the six PRRSV membrane glycoproteins, and that could be a potential candidate vaccine when delivered with a potent adjuvant. Further, studies are required to confirm the dose-dependent vaccine efficacy and the degree of cross-protection against other heterologous PRRSV strains.
Contact: Renukaradhya J. Gourapura (Aradhya); Associate Professor, Food Animal Health Research Program, Ohio Agricultrual Research and Deverlopment Center, The Ohio State University, Phone: (330) 263-3748; Email: firstname.lastname@example.org