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New authority to monitor xenotransplantation experiments

The British government is to set up a regulatory authority to monitor all research into xeno-transplantation– the transplantation of animal tissue into humans. Human trials will not be allowed to go ahead until there has been more research into aspects of physiology, immunology, and the risk of infection.

View larger version (98K): [in this window] [in a new window]   Pigs would be ethically acceptable as a source material. IMUTRAN

Health secretary Stephen Dorrell accepted the main recommendations of the advisory group on the ethics of xeno-transplantation headed by Ian Kennedy, professor of medical law and ethics at King's College, London. He announced the establishment of the Xenotransplantation Interim Regulatory Authority, which will be chaired by Lord Habgood of Calverton. The authority will regulate developments until there is a suitable opportunity for primary legislation.

The advisory committee's report Animal Tissue into Humans concluded that xenotransplantation could be ethically acceptable if certain conditions were met. It states that it would not be ethically acceptable to use primates as a source of materials for xenotransplantation, mainly because they would be exposed to too much suffering.

Pigs, however, would be an acceptable source of material, provided that there is only limited genetic modification. Also, the genetic distance of pigs from humans means that fewer of the viruses present will be infectious to humans and so pose a much lower risk than if primates were used. The report is broadly in line with that produced by the Nuffield Council on Bioethics last year (16 March, p 65).

Attempts at xenotransplantation have been made sporadically over the past 100 years, but all have failed after a few months at most. The main stumbling block to progress has been hyperacute rejection. In the past seven years there have been major advances in this field, and laboratory evidence and some primate work have shown that this powerful immune reaction may be overcome. Although these breakthroughs have generated much media publicity, little research has been published in peer reviewed journals.

There are still many more hurdles remaining, and the report says that there needs to be more research on transplant function, organ growth, the functioning of the recipient's immune system, and other aspects of immunological rejection. The committee estimates that gathering this extra research information could take around 18 months.

The report says that the transfer of viruses to humans causes the most concern, particularly as some porcine viruses may not yet have been identified. Herb Sewell, professor of immunology at Queen's Medical Centre, Nottingham, and a member of the advisory committee, said that transplanting living tissue from animals to humans provided a "unique opportunity" for viruses to jump the species barrier. "Not only could this lead to particular infections in the patient, but the patient may pass on the infection to the rest of the public," he said.

In the United Kingdom the biotechnology company Immutran is developing genetically modified pigs for use as source animals for xenotransplantation, and it intends to move to human trials in the next 12 months. The company welcomed the report but urged swift progress on the establishment of the regulatory authority.

Xenotransplantation causes concern because living tissue is used; porcine insulin and heart valves can be used safely as they are extensively treated first. The interest in xenotransplantation stems from the large shortfall in the supply of donated organs for transplantation compared with the demand.

There will be a three month consultation period on the government's response (see p 242).

Animal Tissue into Humans is published by the Stationery Office (tel: 0171 873 0011).

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