Have virus, will donate

Viruses acquired from animal organ and tissue transplants can harm humans

Published: Friday 15 August 1997

 Scientists are questioning th transplantation of organs from humans has become a common medical procedure. But there are some serious issues involved in the practice. Some of these are primarily ethical, concerning the procedures in transplanting organs between humans. The numbers of patients in urgent need of organ transplants is constantly rising. Paucity of human donors has driven the attention of physicians towards animals - primarily the pig and the baboon - as possible sources for tissue or organ transplants.

Ethical considerations are consigned to the back-burner when it comes to the possible use of organs from animals. However, there are other problems associated with this. The risk of a virus, normally endemic in the animal, being transmitted to the human host and spreading through the population is a cause for concern.This risk has been highlighted by a finding made recently by Clive Patience and his team at the Institute of Cancer Research, London ( Nature Medicine , Vol 3, No 5).

The findings become alarming in the light of the widely-accepted theory for the origin of aids in human beings. The theory has it that the human immunodeficiency virus ( hiv) made the transition from a benign existence in African monkeys to the dire consequences that are only too well known now.

The normal genetic composition of many species, including humans, contains dna sequences that are related to retroviruses. Retroviruses, of which hiv is an example, can transfer their own genome into the host's dna for replication. This involves conversion of genetic material of the virus ( rna ) into the more common genetic material of living organisms ( dna ). It makes them likely invaders of possibly harmful foreign genomes.

Earlier research has shown that viruses that develop within the bodies of baboons, cats and mice (endogenous viruses) can infect human cells and multiply. Pig cells in culture that have the same genetic structure (cell lines) are known to release retroviruses but it was not believed that this could pose a risk to potential human hosts.

The research team from London has shown that dna from pig endogenous retrovirus ( perv ) can be transmitted to human cells in culture as an infection, and also to other pig cells. The human cells were exposed to a filtered extract of perv -producing cells and were also cultured with them. Tests revealed that the human kidney cell line became infected and was capable of transmitting perv. Foetal cells, a cancer cell line, and two immune system cell lines also became infected but did not allow perv to reproduce within them, preventing further infection.

The findings question the safety of transplantation of organs from animals. The possibility of an endogenous retrovirus (non-pathogenic in its normal host) acquiring harmful attributes after infecting a foreign host is very real.

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