Infection Hazards of Xenotransplantation

Abstract

Zoonoses are a major area of concern, with the growing pressure to carry out clinical xenotransplantation, the grafting of animal cells, tissues and organs into humans.1–3 While the benefit of the xenograft to the individual patient might outweigh the risk of infection, it is the fear of setting off a new epidemic in the human population that distinguishes the infection hazards of xenotransplantation from the well-known infection hazards of allografts and of blood transfusion. Of course, animals have transmitted viruses and other infectious pathogens to humans ever since we learnt to hunt or husband them, yet we continue to meet nasty surprises. The AIDS pandemic is caused by viruses which have only recently jumped host species from chimpanzees (HIV-1) and sooty mangabey monkeys (HIV-2).4 New variant Creutzfeld–Jakob disease is linked to bovine spongiform encephalopathy. The current Malaysian epidemic of Nipah virus probably has a reservoir in fruitbats, but is spread by pigs.5 The lack of onward, humanto-human transmission of chicken H5N1 influenza virus was a fortunate, unpredictable feature of a zoonosis which killed 6 of 18 infected individuals. If zoonoses happen so readily, why should we be concerned over an added risk of this occurring through xenotransplantation? In fact, such zoonoses are fairly rare events, but xenotransplantation could increase the risk of occurrence for three reasons:-