Dr Stewart Jessamine, New Zealand

Xenotransplantation is the transplantation of living cells, tissues, or organs between species, while allotransplantation is the transplantation of cells or organs within species. Xenotransplantation is a new technology and there are many factors to be considered, such as physiology, immunology, microbiology and ethical issues.

In terms of public health implications, all xenografts contain endogenous retroviruses which can infect cultures of human cells. However, whether these endogenous retroviruses can infect human cells in vivo or can replicate in human cells, thus causing disease, is still unknown. WHO and several regulators have urged that xenotransplantation be treated with extreme caution as the consequences of any emergent new infection could be serious.

Since xenotransplantation is unlike other medical treatments, the standard approaches to regulation, informed consent and ethical review may be inadequate. WHO urges each regulator to make its own risk-benefit assessment of the associated ethical and cultural issues.

In New Zealand, the Gene Technology Advisory Committee and the Royal Commission on Genetic Modification have recommended that xenotransplantation should not proceed in New Zealand until extensive public consultation has occurred. The Medicines Act was amended to place a temporary control over three “restricted biotechnical procedures”, namely xenotransplantation, cloning and genetic modification of human embryos. A comprehensive new regulatory regimen will be developed in the next four years.

New Zealand has declined an application to conduct xenotransplantation; the applicant has since approached several nearby countries with less strict regulatory systems and offered incentives to these countries to allow patients from New Zealand to be flown there for treatment. This could be called xenotourism. However, all attempts were rejected by the governments of these countries. The international consensus is that it is ethically unacceptable for a country to allow xenotransplantation to proceed within its borders without regulatory oversight and control.