In 1987, Porcine Reproductive and Respiratory Syndrome (PRRS) virus was first detected in the U.S. Pigs that contract the disease to stop reproducing, do not gain weight, and have a high mortality rate. No vaccine has been effective, and the disease costs North American farmers more than $660 million annually. Now, a team of researchers from the University of Missouri, Kansas State University, and Genus plc have bred pigs that are not harmed by the disease.

Scientists have, for years, tried to determine how the PRRS virus infected the pigs, and how to stop it. They believed that the virus entered the pigs by being inhaled into the lungs, where it attaches to the protein sialoadhesin, but they found out that elimination of sialoadhesin had no effect on susceptibility to PRRS. A second protein, CD163, was thought to "uncoat" the virus and allow it to infect the pigs. In the current study the team worked to stop the pigs from producing CD163.

The team edited the gene that makes CD163 so the pigs will not produce it, and infected the pigs and the control pigs. They observed that while the pigs that didn't produce CD163 did not get sick, there were no other changes in their development compared to pigs that produce the protein.

For more details, read the news release at the University of Missouri News Bureau.