"We don't know that if we transplant pig organs with the viruses that they will transmit infections, and we don't know that the infections are unsafe", Fishman said.
Pig organs are the same size as human organs and function pretty much the same way but pig to human transplantation has always been an elusive goal for researchers due to fear of activating dormant viral diseases in the pig's cells.
The researchers, including famous Harvard geneticist George Church, used the powerful gene-editing tool CRISPR-Cas9 and the same technology used to clone Dolly the sheep to create healthy piglets that can't transmit harmful viruses.
Creating PERV-free pigs is the first step in a four-step process to ultimately create pig organs suitable for human transplant or "xenotransplantation", Dr. Luhan Yang, a co-founder of eGenesis and the company's chief science officer, explained to HuffPost.
Fears that pig organs would infect humans with weird retroviruses brought the research to a halt. Inactivating the virus could ease those concerns.
The world has a big organ shortage problem: nearly 120,000 people are now waiting for a transplant in the USA, and more than 20 people die each day waiting for a new organ.
The findings represent an important breakthrough in the potential for xenotransplantation, or the use of animal organs in humans. Remnants of ancient viral infections, genes from porcine endogenous retroviruses-known by their unfortunate acronym-are scattered throughout the pig genome, and could infect a person who one day receives a pig's heart, lung, or kidney as a replacement or temporary organ. One of the biggest problems with organ transplants is rejection: the body's immune system tends to recognize transplants as foreign. Those proved too challenging for a slew of researchers going after this subject in the 1990s.
That concern, particularly amid the HIV epidemic, has helped stall such research for the past couple decades (with the exception of pig heart valves that are used in humans-dead tissue that doesn't pose the same transmission risks). In a lab dish the pig viruses infected human cells, and those infected cells were able to infect other human cells that had not been directly exposed to pig cells.
These baby pigs were the first to be born without innate viruses in their DNA. Pig organs are quickly rejected by the body, causing severe immune reactions.
Now, the company can test the pig to make sure the organs are safe and effective, and eventually move the pig organs into clinical trials.
"The use of human organs for transplantation only meets a small percentage of the total and growing number of individuals in desperate need of organ transplantation".
Xenotransplantation using pigs has been singled out as a possible solution to the organ crisis because the organs of pigs and humans are similar in size and function.
"I think it's a good sign that the field has been revived", she told Business Insider. And the world's largest pork producer is exploring how to grow tissues and organs that could be used in human transplants.