A risky business.

While there are as yet no further xenotransplant organ experiments, transplants of pig cells to the human brain have been carried out in cases of stroke damage and Parkinson's disease. The procedures, which involve taking foetuses from a sow, removing certain of their brain cells and transplanting them to the patient's brain, are shown. Patients have shown improvement after this treatment. Prof. Robin Weiss (University College, London) explains, however, that the danger of virus transfer remains. Pig genes contain a slow-acting virus which does no harm to the animal but could have unforeseen effects if it combined with a human virus. Also, any harm might not be confined to the individual, but could create a public health risk. It was found that mice receiving transplanted pig pancreas also received the virus which lived on in their cells. Some mice eventually developed lymphoma and leukaemia - whether this was a result of the transplant is not yet certain. Further explorations in cell transplant aim to treat severe neurological disfunction such as damage to the spine. For this research, brain cells from pigs were transplanted to monkeys in order to repair the protective tissue (myolin) that forms a sheath around the nerves. The potential benefits of cell xenotransplant are great, but progress must be determined by continual risk assessment.