A New Zealand biotech company began a trial Thursday of an experimental treatment for diabetes in which cells from newborn pigs will be implanted into eight human volunteers.

Living Cell Technologies hopes the cells may be able to delay the effects of Type 1 diabetes, including blindness, premature coronary illness and limb amputation resulting from poor blood circulation.

Prof. Bob Elliott, medical director of the company, acknowledged that, even in the best-case scenario, the treatment would not eliminate all symptoms.

Some scientists have warned that implanting pig cells has risks. Others say it is too soon to begin testing on humans because no animal trials were conducted.

One risk is that viruses that exist in animals but not in humans could jump species, potentially causing new illnesses and possible new pandemics. Scientists say there are more than 100 pig viruses that could potentially transfer to humans.

Elliott said Thursday that the possibility of a pig endogenous retrovirus — the virus thought to be most contagious for humans — infecting humans is largely "theoretical."

"There is no evidence of a risk" of a pig retrovirus infection, he said.

He said the piglets being used, recovered from 150 years of isolation on islands south of New Zealand, carried no known agent that could infect humans and are held in a fully closed, sterile environment.

Prof. Martin Wilkinson, past chairman of the New Zealand Bioethics Council, said pig islet cells pose "a very small risk" that "is low enough to be managed in human recipients."

"There is no conclusion that it (transplanting animal cells in humans) should be banned just because of the possibility of risk," Wilkinson, who is not involved in the trials, told reporters Thursday.

Elliott has run two previous trials, the first with six patients in New Zealand in 1995-1996. The other, in Russia with 10 patients, began in July 2007. He said he has seen increased insulin production in some subjects, while others rejected the pig cells or the implanted cells stopped producing insulin after a year.

A scientific paper on the trial is to be produced by the end of 2009, he said.

In Type 1 diabetes, the body mistakenly attacks and destroys cells in the pancreas that produce insulin, the hormone crucial to converting blood sugar to energy. It is different from the far more common Type 2 diabetes that is usually linked to obesity, in which the body produces insulin but gradually loses the ability to use it properly.