In the largest retrospective study to date to access the safety of xenotransplantation, researchers have found no evidence of the porcine endogenous retrovirus in 160 patients who were treated with living pig tissue up to 12 years earlier.
Reporting on August 20 in Science (1999; 285:1236-1241), investigators from Imutran, the Cambridge-based branch of Novartis Pharma that studies xenotransplantation, and the Centers for Disease Control and Prevention in Atlanta said that the study group included 36 patients who were pharmacologically immunosuppressed and, therefore, presumed to have an increased risk of infection.
Twenty-three patients had clear evidence of circulating pig cells but no signs of infection, and some of these patients had been treated more than eight years previously. "This finding demonstrates that pig tissue can survive in the human body for long periods with no ill effects," Imutran said.
The study included patients who had been treated with pig skin grafts for severe burns, pig pancreatic islet cells for diabetes, or had had their blood perfused outside their body through pig spleens, kidneys, or livers. "These results support the use of closely monitored clinical trials as an approach to assessing the safety and efficacy of using porcine cells, tissues, or organs therapeutically in humans," author Khazal Paradis and colleagues wrote.
The study adds fuel to the debate over whether xenotransplantation is safe for humans. In reports in Nature Medicine (1997;3:282-286) and Nature (1997;389:681), researchers in London warned of the possibility of pig viruses spreading to humans. Fueled, in part, by these reports, in early 1998 some scientists called for a moratorium on xenotransplantation research.
Alexion Pharmaceuticals of New Haven, Connecticut, which develops porcine tissues and organs for human xenotransplantation, issued a news release expressing optimism over the new findings. "The current report provides the most comprehensive clinical evidence to date that such [porcine virus] transmission may be highly unlikely, suggesting that with the appropriate careful monitoring, pigs may represent a safe source of donor tissue for patients," the company said.
For Your Information:
Novartis news release:
www.info.novartis.com/media/press_notes_www/392a_1a6.htmScience
An editorial accompanies the new findings published in Science (1999;285:1221-1222). Science is online at www.sciencemag.org.
Please be aware that medical advice, diagnoses and physician references cannot be obtained from this site.