Date Full Report Received


Date Abstract Report Received



Primary Investigator:

We determined that the enzymatic activity of the first 215 amino acids of PRRSV nonstructural protein 2 (nsp2) varied considerably with the viral strain tested. This enzyme has been shown to be responsible for inhibiting interferon alpha (IFN) by deubiquitinating or deISGylating viral proteins that have been marked for degradation by the ubiquitin pathway (DUB) or other interferon stimulating genes (e.g. ISG15). Those strains with high in vitro enzymatic activity, as determined by biochemical assays, corresponded with the strains causing more pathogenesis in swine. We were able to model this enzyme and obtain data relating to actual enzyme structure. In so doing, we identified potential ramino acid residues in this enzyme domain related to DUB and deISGylation activities.
With this biochemical knowledge, we produced 8 PRRSV mutant constructs that should change the enzyme activity and characterized the viruses in vitro. In order to understand whether they would replicate in swine, we inoculated these 8 mutants into swine in a limited study of 5 days. We found that all mutants grew well in vivo when given at a relatively high dose. We are now preparing an extended study, due to take place this spring, to examine whether or not the mutations resulted in changes in the swine immune response. We hope to show that the mutations made will improve the swine response to HP-PRRSV JXwn06 and other virulent US strains. This knowledge may be used to improve vaccination regimens. Kay Faaberg (kay.faaberg@usda.gov), Kelly Lager (kelly.lager@usda.gov) and Scott Pegan (spegan@uga.edu).