Talk urged on pig cell transplants

By SIMON COLLINS

The Ministry of Health has called for a national debate before there is any New Zealand-based research that involves transplanting living animal cells into humans.

The ministry's chief adviser on safety and regulation, Dr Bob Boyd, says it is "time more voices were added to the debate about the risks that might be faced by the public from a treatment designed for treating an individual".

He questions the ethics of a plan by Auckland-based diabetes research company Diatranz to run clinical trials in the Cook Islands after the ministry rejected its application to do the trials in New Zealand.

Diatranz medical director Dr Bob Elliott is due to brief the Cook Islands Cabinet today about his plan to transplant insulin-producing pig cells into the bodies of 24 Cooks diabetics.

In earlier trials in Mexico, the pig cells produced insulin in the bodies of some teenagers given them.

But Dr Boyd said the procedure's potential benefit for diabetics must be weighed against the risk of infecting the whole human population with pig "retroviruses", which can be transmitted to other individuals in body fluids.

"The most well-known example of a retrovirus is HIV/Aids," he said.

Dr Elliott has described this risk as only 0.001 per cent, saying he is "99.999 per cent certain" that any pig retrovirus transferred to his patients would be killed by their immune systems.

But Dr Boyd said: "While the risks may be considered small, they are considered real by most experts around the world."

The president of the Royal Society in London, Lord Robert May, urged scientists at a breakfast in Auckland yesterday not to hide their uncertainty, which was the essence of science.

He believed the public took a sensible approach to the risks and ethics involved in procedures such as transplanting animal cells into other species, or xenotransplantation.

Dr Boyd said the Gene Technology Advisory Committee, which considered Diatranz's bid to transplant pig cells into people in New Zealand, felt that further research was needed on animals before risking the procedure with humans.

A pioneer British transplant surgeon, Sir Roy Calne, said last month that more research on animals was needed in order to understand why sertoli cells taken from the testicles and inserted into the Mexican teenagers with the pig cells apparently helped to stop their immune systems rejecting the pig tissue.

Dr Elliott agreed that more research on animals was needed before repeating the Mexican experiment with sertoli cells, but said he did not plan to use the cells in the Cook Islands trial.

"There has been very little done with sertoli cells," he said.

"That is the problem. We don't know what to alter to improve things because we don't have those animal guidelines."

Instead, he plans to repeat the trial he conducted with six New Zealand diabetics in 1996 which enclosed the pig cells in a capsule so the body's immune system could not get at them, but where the insulin they produced could be released.