Animals to the rescue

WITH worldwide shortage of humanns for transplantation, xenotransrnt surgery is a welcome change. The Ift,Apinsfer of animal organs into humans prevent organ donors from being rived of an organ, and the right unt of money. If unlimited organs available, about 100,000 transplant cries would be conducted in the usestimates Daniel Salomon, transet immunologist at the Scrippsarch Institute in La Jolla, forriia, (The Economist, Vol 337, No,937).

In the last couple of years, several0-human and two baboon-toan transplants have taken place. Akaboon bone marrow transplant operaDan would be conducted on an AIDSti nt in San Francisco this year. Agz,esh biotech firm has bred pigs for thesole purpose of organ and tissue translants (Down To Earth, Vol 4, No 12).This would open up new vistas and50ing hope to millions waiting for an10 But for virologists like JonathanUan at the Southwest Foundation forOPT edical Research, xenotransplantanon is a medical nightmare. What if anirifections carried into the humanproliferate under suitable condition What if they are transmitted into:humans and spark a pandemic?

Organ transplant surgery requiresCression of the immune system, sothe organ is not rejected by thePrpient's immune system. Thus, theune response is controlled byUtaming a strict drug regimen. This@kes the organ recipients susceptibleU.;,-.ous health problems for the resttheir lives.

Virulence and 'new' disease arerelated. No one knows whichI;nism is likely to be harmful. Forple, the Macaque herpes is fatal forbbut not to macaques. The post effects of the organism on therMans can be known by outwardtoms only. The AIDS virus wasro'wn till it reached the developedd and research showed that Hiv wasr= from monkeys into humans.While the natural hosts have beenunaffected, the virus has created a pandemic.

There are also endogenousretroviruses present in all animalswhich are passed on passivelyfrom generation to generationthrough the host's DNA. Can theywreak havoc on contact with a forbody? While animalbreeding eigncan remove all known pathogens,eliminating endogenous retrovirusesrequires further research in genetics.

The proponents of xenotransplantthink the risks are few as they are concentrating on organs from baboons andpigs. While pigs are fast-breeding andcan be bred into pathogen-free colonieseasily, baboons are closely related tohumans, but are slow breeding animals.

Baboon bone marrow could helpdestroy or control the AIDS virus, saytransplant immunologists. The monkeys' immune system possibly has HIVfighting agents. Besides, baboon tissuesare to be used as a stop-gap arrangement which can be replaced by humantissues later, but even then, infectiousagents from the animal organ could betransmitted to the human body.

Pigs offer a safer option. Humanshave consumed pigs through the agesNew for old and both share some common diseaseslike influenza. As they breed fast, theycould be bred free of all diseases foundin pigs. But, as they are not closely related to humans, the human immune system has to be adapted to make it accepttheir organs.

The proponents feel minimisingrisks through known animal diseasesand keeping a close post-operativewatch on organ recipients, with theirconsent, would help. But this would notprevent a disease from passing onunknowingly to fellow human beings,argue the opponents. Till the problemsare ironed out, the solution lies withauthorities who can issue regulations. Iflaws dealing with taking organs fromthe newly dead could be implementedeasily, then there is still hope for many.