Project Title: Rational Design of a New Generation of PRRSV Differential (Marker) Vaccines

Institution: Department of Veterinary and Biomedical Sciences, University of Nebraska-Lincoln

Outcome/Results: Important genes that are related to virulence have been identified.

We started this project with the conviction that the use of vaccines will always be a cost-efficient method and the preferred approach to control PRRSV infections. The capacity of PRRSV to infect cells and pigs and to cause serious pathologic changes is called virulence. This virulence is caused by the different genes and its proteins composing the PRRSV. Our technical approach to the improvement of PRRS live vaccines is based on the notion that mapping the genes causing virulence in PRRSV should provide information for the development of a differential PRRSV vaccine of unprecedented safety and efficacy. The main expected outcome of this research is changing the genes of the PRRS viruses to develop live attenuated/marker vaccine strains. Engineering of new live-attenuated PRRSV marker vaccines requires knowledge of the genetic make-up of PRRS virulence and identifying areas of the virus which do not affect the virus’ ability to infect the pig. During the 2005 year study, the first in this multi-year project, we have identified important genes that seem to be related to virulence as well as important small fragments of the PRRSV proteins that can be used, upon further testing, to prepare tests that would allow these vaccines to be used as marker vaccines. The best example of this type of product is the successful case with PRV. Our PRRSV work continues through 2006 thanks to the renewal of support by NPB. During 2006 we have looked more closely at the marker to be used for differentiation and determined that by changing certain genes we could also improve how protective the vaccine candidate may be by enhancing the vaccine response of the pig by having the immune system produce the antibodies that halt the effect of PRRSV.