2019-03-07 12:12:01

By Andy Coghlan TRANSPLANTS of pig organs into human patients have edged closer following reassuring results from a long-awaited safety study. Patients treated with live pig tissue showed no signs of infection with porcine endogenous retroviruses (PERVs) Some doctors worried that the viruses might spread to people causing new infectious diseases. “Overall, we think the study is very good news,” says Corinne Savill of Imutran, the Cambridge-based company developing pig hearts and kidneys for “xenotransplantation”. Patients have routinely received pig heart valves since 1964, but these contain no live cells. Transplanted organs would still contain live pig cells potentially capable of transmitting viruses. To discover whether live pig tissue poses a threat, researchers from Imutran trawled the world for patients who had been treated with live pig tissue. Of the 160 patients they identified, 131 had undergone operations in which their blood had temporarily circulated through live pig tissue. A total of 14 patients were exposed to pig tissue for a year or more when they were given pig pancreatic islet cells, which manufacture insulin. Another 15 received grafts of pig skin that were in place for more than a week. Kaz Paradis of Imutran and his colleagues report no traces of PERV infection in any of the 160 patients (Science, vol 285, p 1236). One unexpected finding, however, was the survival of pig cells in 23 patients, one of whom was treated more than eight years ago. Savill says that the first xenotransplants are probably between two and five years away. Opponents of xenotransplantation are less reassured by the results, however. “They provide only limited confidence,” says Gill Langley, scientific adviser to the Dr Hadwen Trust for Humane Research, which is opposed to animal experiments. “It only takes one instance to create a disaster,