Iowa State University Seeks to Develop Pig to Benefit Human Medical Therapies

Chris Tuggle portrait
Chris Tuggle

AMES, Iowa — A National Institutes of Health grant of $2.5 million will fund Iowa State University research to develop a line of pigs with an immune system that is uniquely suited to testing medical therapies for people.

Four years ago, in work that originated at Iowa State, scientists identified the first pigs with naturally occurring Severe Combined Immunodeficiency, known as SCID. Until this discovery the inherited disorder was only known to naturally affect humans, mice, horses and dogs.

Those born with SCID have an incomplete immune system that can’t adapt to pathogens. In the 1970s, a famous case was a young boy, known as the “bubble boy”, who suffered from the disorder and had to live in a sterile room to avoid germs.

“The pig is known to be an excellent model for human biology due to its similar size, physiology and genetic make-up, and this novel SCID pig model has been successfully engrafted with multiple human cancer cell lines. This shows it has high potential as a model for many areas of testing in regenerative medicine, a new medical specialty that repairs disease instead of treating symptoms,” said Christopher Tuggle, professor of animal science who will lead the research project.

Tuggle said there have been several inquiries about the pig from researchers who are familiar with Iowa State’s discovery. The research areas of these interested scientists spans many areas of regenerative medicine, from cardiac injury therapies to cartilage regeneration studies, to the use of stem cells for bone regeneration and wound repair, to improving the treatment of graft versus host disease in bone marrow transplants.

The SCID discovery arose from an Iowa State feed efficiency study on pigs led by animal scientist Jack Dekkers, a priority project for the pork industry because of the high cost of feed. As part of a collaborative study with Kansas State University, the pigs were exposed to a virus to determine if their feed efficient status affected immune response, and some were found to have severely affected immune organs.

“In the SCID pig, you have a biological ‘empty vessel’ that does not reject a pathogen or foreign cell,” Tuggle said. “It could be used to test if a therapeutic cell derived from stem cells can repair damaged tissue before you start clinical trials. You also can directly test whether new drugs can kill implanted cancer cells in an organism very similar to a human cancer patient.”

Tuggle also said scientists can transplant human bone marrow cells into the SCID pigs, in the same way that researchers have done with SCID mice, and attempt to create pigs with an immune system similar to humans. Such a pig could be used to test vaccines to human pathogens like HIV or virulent influenza, he said.

These pig models would have many advantages over mice used in such research, he added, because immune cells and immune protein sequences in the pig are more like humans.
Tuggle, who also serves as the National Swine Genome coordinator, said the SCID pig remains a valuable model to the livestock industry. The SCID pig can be used to study immune response to diseases that are important to the swine industry, such as Porcine Reproductive and Respiratory Syndrome and influenza.

Tuggle’s research team for this four-year project includes animal scientists Joan Cunnick, Jack Dekkers, Matthew Ellinwood and Jason Ross, and Mary Sauer, Iowa State’s attending veterinarian in the Office of the Vice President for Research.