Date Full Report Received02/03/2014
Date Abstract Report Received02/03/2014
InvestigationInstitution: ARS, NADC, USDA
Primary Investigator: Kay S. Faaberg
Co-Investigators: Allyn Spear
Funded ByNational Pork Board
Many significant hurdles have complicated vaccine development for porcine reproductive and respiratory syndrome virus (PRRSV). This work utilized a naturally occurring byproduct of PRRSV replication called heteroclite RNA that has been shown to be packaged along with normal infectious virus. The first objective of this proposal was to engineer a heteroclite RNA to express proteins known to enhance the immune response. This modified RNA could then be used to augment a modified live vaccine (MLV). The second objective of this proposal was to assess the impact of these augmented MLV preparations in porcine alveolar macrophage (PAM) cells, the natural target cells for PRRSV replication.
The genes for the immune enhancing proteins were successfully cloned from swine tissues, and the PRRSV heteroclite RNAs were genetically modified to allow the insertion of the immune enhancing genes. Several trials were attempted using different methods to get infectious PRRSV MLV to take up the genetically modified heteroclite RNAs, however this proved to be very difficult. The MLV virus was able to generate its own heteroclites so rapidly that they overwhelmed the modified heteroclite RNAs, making the uptake very inefficient. Despite multiple experimental modifications, no protocol was ever able to achieve sufficient modified heteroclite uptake to allow testing in PAM cells. Continued efforts to develop a selection process to force uptake of heteroclite RNAs with immune enhancers are currently in progress. Should these current efforts succeed, this approach still has the potential to enhance the immune response to PRRSV MLV vaccines.