PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME (PRRS) IS ONE OF THE MOST SIGNIFICANT VIRAL DISEASES AFFECTING SWINE PRODUCTION WORLDWIDE. THE DISEASE CAUSES REPRODUCTIVE FAILURE (ABORTIONS AND STILLBIRTHS) IN PREGNANT SOWS AND PNEUMONIA IN PIGLETS. STUDIES CONDUCTED BY THE NATIONAL PORK BOARD ESTIMATED THAT THE ANNUAL LOSSES CAUSED BY PRRSV TO THE U.S. SWINE INDUSTRY WERE $640 MILLION IN 2011. REDUCING THE ECONOMIC IMPACT OF PRRSV IS THE TOP PRIORITY TO THE SWINE INDUSTRY. ALTHOUGH PRRS VACCINES ARE COMMERCIALLY AVAILABLE, THE EFFICACY OF THE CURRENT PRRS VACCINES IS FAR FROM SATISFACTORY. ONE MAJOR LIMITATION OF THE CURRENT PRRS VACCINES IS THAT THEY DO NOT PROVIDE OPTIMAL LEVELS OF PROTECTION DUE TO THE SUBSTANTIAL GENETIC VARIATION AMONG PRRS VIRUS ISOLATES CIRCULATING IN THE FIELD. ADDITIONALLY, THE CURRENT PRRSV VACCINES DO NOT CONTAIN A DIVA MAKER (DIVA STANDS FOR DIFFERENTIATING INFECTED FROM VACCINATED ANIMALS). THEREFORE, ONCE CURRENT PRRS VACCINES ARE ADMINISTERED IN THE HERD, SWINE PRODUCERS CAN NO LONGER USE SEROLOGICAL TESTS TO DETECT VACCINATED PIGS THAT ARE SUBSEQUENTLY EXPOSED TO WILD-TYPE PRRS VIRUS ISOLATES. THE OVERALL OBJECTIVE OF THIS RESEARCH PROPOSAL IS TO GENERATE A NEW PRRS VACCINE THAT NOT ONLY CONFERS BROAD PROTECTION BUT ALSO PERMITS TRACKING OF THE CIRCULATION OF WILD-TYPE PRRS VIRUS IN VACCINATED HERDS, THUS, MAKING THE NEW VACCINE MORE EFFICACIOUS IN ERADICATION OF THE VIRUS. IF SUCCESSFUL, THIS VACCINE WILL PROVIDE SWINE PRODUCERS WITH THE MOST COST-EFFECTIVE TOOL FOR THE SUSTAINED ELIMINATION OF THE VIRUS FROM U.S. SWINE HERDS; THEREBY, ENHANCING THE SUSTAINABILITY OF THE U.S SWINE INDUSTRY.