Project Title:  Development of a Killed Subunit PRRS Vaccine

Institution:  Department of Animal Science, Iowa State University, Ames, IA

Outcome/Results:  A killed PRRS vaccine was able to cause an immune response, but more needs to be done to increase the response and provide protection from the disease.

The focus of our research funded by the National Pork Board was to develop killed PRRS vaccines.  The portion of the PRRS virus responsible for stimulating an antibody response to remove the virus from the body is hidden from the immune system in several strains.  Our research used enzymes to attempt to remove the agents hiding the virus area.  Once these agents are removed, the theory is that the immune system can respond to the exposed area to help remove the virus from the pig.  Evaluation of this immune response to remove the virus from the pig was carried out in test tubes using serum from the pigs and known PRRS virus amounts.  The hypothesis for this research was that a killed vaccine composed of virus particles without the hidden areas would develop a stronger antibody response and provide protection from disease.  Observations in our experiments yielded mixed results.  An immune response was seen in some pigs; however this specific type of response was relatively weak and did not provide protection from disease.  The positive result of these findings is that this special antibody response can be elicited with a killed vaccine.  A limitation in our research was the ability to determine how much of the killed PRRS virus each pig received.  When we increased the amount of this total protein within the vaccine we were able to detect an immune response earlier.  These results lay the ground work for future studies evaluating immune response and protection from disease utilizing known amounts of the proteins of the PRRS virus.