Jamie Johansen
Dr. Randy Prather, Professor of Animal Science at the University of Missouri and Director of the National Swine Resource and Research Center (NSRRC)Our growing world population is dependent on thriving agriculture products. Science is at the center of what agriculture can accomplish when it comes to feeding our growing world. A true a game-changer for animal agriculture was announced in early December 2015 that brought science-based agriculture into a whole new realm of possibilities. With the use of gene editing, researchers have grown pigs completely resistant to one of the most economically costly diseases the industry has seen. What does this mean for our beef industry? Might we be able to raise cattle resistant to BRD, black leg or pink eye? Could we eliminate the need for vaccinations or antibiotics?
Dr. Randy Prather, Professor of Animal Science at the University of Missouri and Director of the National Swine Resource and Research Center (NSRRC), once swore he would never work with pigs and was fully committed to beef cattle research. While at the University of Wisconsin-Madison, Dr. Prather found beef research was flooded, but when an opening working with pigs was presented, he took it. Since then swine research has been his focus. He came to the University of Missouri in 1989 with his program centered on early embryo development. Dr. Prather has a long list of successful research trials in swine reproduction, but has spent over a decade putting the pieces together to finally provide an answer to the Porcine Reproductive and Respiratory Syndrome (PRRS) virus.
PRRS is a viral disease causing reproductive deficiency in breeding aged pigs and respiratory issues in pigs of any age. In fact, Dr. Prather estimates this disease costs the industry throughout North America and Europe about $6 million a day, but says it goes beyond being an economic issue. He believes it is an extreme animal welfare concern.
“The vaccines didn’t seem to be working well. It was a great candidate to try and use other technology to solve the problem,” said Dr. Prather.
Dr. Prather’s team first tried to knock out sialoadhesin in their fight against PRRS. Sialoadhesin is a cell adhesion molecule that is found on cells of the immune system called macrophages. Once they had pigs that didn’t produce that molecule in their cell surface they needed to find a location for the pigs to be challenged with the PRRS virus.
His team searched the country to find the best. They quickly found Dr. Bob Rowland’s team at Kansas State University who already had a system set up and had a long resume of researchers they had worked with. Unfortunately, those pigs without sialoadhesin got sick. That is when Dr. Prather and his team started working on CD163.
“We started using a new technique to edit the genome called a CRISPR cas9 system. We successfully used that and created some founder animals. We bred those together and had animals that had both alleles edited,” Dr. Prather said.
The CRISPR cas9 system simply creates a RNA-programmable method to resolve genome editing in mammals.
Those pigs with edited genes were also sent to K-State to be challenged with the PRRS virus. Even though these pigs were in a pen with other sick pigs. The CD163-free pigs showed no signs of fever and no coughing. They didn’t get sick.
Dr. Prather calls CD163 a gatekeeper. It provides a way for the virus to enter if it is there, but with the gene editing the protein doesn’t exist. Thus, closing the door for the virus.
Now that the molecule that is responsible for PRRS infection has been identified, Dr. Prather said they will wait to find out if these pigs will grow at the same rate as pigs with unedited genes.
“The next step is to recreate the same genetic edit on high-end animals that are consistent with what the pork industry is seeing right now in a production system to determine if they gain at the same rate and if there are any other adverse effects,” said Dr. Prather.
Right now Dr. Prather said the pigs look great and are growing fine. They reproduce like normal and they don’t anticipate any problems, but time will soon tell if this groundbreaking research can be mass-produced to revolutionize the pork industry.
Other phenotypes might be identified that are associated with PRRS that have not been anticipated. Since this is brand new, the regulatory process is also an unknown.
Another partner in this research has been Genus plc, a global leader in animal genetics. They provide producers with superior genetics, which enable them to produce high quality food animals. Genus have licensed this technology and are predicting it will be about five years before producers will see CD163-free pigs in their farrowing houses.
Dr. Prather said the genome is billions on letters long. This genetic editing simply changes a handful of those letters. The skies the limit when it comes to the possibilities of using this same application throughout animal agriculture.
Consumer confidence and consumer understanding is always key when it comes to produces food animals. Relaying trailblazing concept to the consumer will be key to their acceptance of the technology and not fear of it.
“I would urge the consumer to not immediately have a knee-jerk response. I look at the tremendous benefits that could come from this. What the consumer has to realize is this is really a different technology than they have thought about before,” Dr. Prather said.
Gene editing isn’t taking a gene for one species and putting it into another species. Dr. Prather reminds us they are just changing the letters in the genome and haven’t added anything.
“I would argue that consumers have a moral obligation to at least educate themselves and consider this as an option rather than flat out rejecting it,” said Dr. Prather.
Dr. Prather has spent a large portion of his career on PRRS. So, what’s next for the researcher? He said he has a whole list of genes they are interested in editing. At NSRRC, his team has made over 45 different modifications. Some transgenes, some knockouts and others gene edits like in PRRS. They also make pigs for human medicine because believe it or not, Dr. Prather said there is many interesting things pigs can be used for in treating humans with diseases.
Gene editing has opened up an entirely new area for people to research. Dr. Prather calls it a very exciting time to be a part of animal agriculture.
Originally published in Missouri Beef Cattlemen and on AgWired.com

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