Testing GP4 in Protection of Swine from Porcine Reproductive and Respiratory Syndrome (PRRS)

Since its emergence in the 1980’s, porcine reproductive and respiratory syndrome (PRRS) has had a devastating effect on the swine production industry. The disease, caused by a small RNA virus, emerged simultaneously in the United States and Europe, and then proceeded to spread worldwide. The virus was first isolated in Lelystad, Netherlands in 1991. After isolation, researchers began characterizing the biological properties of PRRS virus with the hope of generating a vaccine. The first commercially available vaccine to control PRRS was made in 1994; however, protection is only against homologous viruses. Furthermore, this vaccine has been linked to viral infection in the field. Cutting edge technology has been used to develop vaccines using a variety of proteins from the virus, but their success is still limited. A proportion of experimental vaccines have focused on the highly immunogenic GP5 protein. However, immunological drawbacks with this protein are numerous and call for the investigation of other proteins as vaccine candidates. The role of minor viral glycoproteins in protection from PRRS is not well understood. We tested GP4 in protection of swine which, to our knowledge, has not yet been defined. A DNA vaccine and a replication-defective adenoviral vaccine, both expressing GP4, were administered separately or in combination before viral challenge with homologous virus. Under the experimental conditions used here, the vaccines failed to induce an antibody response and protection. Because of the lack of antibody induction, the role of GP4 in protection of swine from PRRS could not be ruled out