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Monday, 22 May, 2000, 16:44 GMT 17:44 UK
Monkeys genetically modified in the womb
BBC Wild
By BBC News Online science editor Dr David Whitehouse

The possibility of treating human genetic diseases before birth has been raised by a series of experiments on unborn monkeys.

The procedure, the first successful foetal gene transfer in a species closely related to humans, the macaque monkey, suggests that gene transfer can be accomplished in utero without causing genetic malformations in the offspring.

"The finding holds out the hope that gene therapy can be safely administered to human foetuses to treat genetic diseases, although such experiments are years away," said Dr Bruce A. Bunnell of the Children's Hospital, Columbus, Ohio, US.

Bunnell injected 14 macaque foetuses with a light-emitting marker gene derived from jellyfish. Connected to the jellyfish gene were one of two additional strands of DNA.

These were the murine leukaemia virus (Mlv), a virus commonly used in research, or the HIV-1 virus.

Delivered to term

HIV-1 was chosen because Mlv becomes incorporated only into rapidly dividing cells, whereas HIV-1 reaches the cells of such organs as the liver and brain that are less likely to divide.

Before injection, portions of the HIV-1 virus were deleted to render it harmless.

According to a report given at a research conference organised by the American Academy of Paediatrics, all of the monkeys were carried to term and delivered by caesarean section.

At birth, Dr Bunnell found that all 14 primate infants were healthy and normal, except that they expressed the introduced marker gene in every cell of their bodies.

However, Dr Bunnell reports that after about one month the monkeys stopped expressing the marker gene for reasons that are unexplained.

Ethical debate

The scientist said it may be that the macaques mounted an immune response to the foreign protein. Until this limitation is understood and overcome, foetal gene therapy cannot have long-term success, he added.

This work is important in developing gene therapy treatments for humans because the macaque foetal development is very similar to the human, except that it occurs slightly swifter.

Although macaques are more difficult to study, the data are more relevant to human genetic disease than data from other species.

The results are encouraging but it should be stressed that they represent just the start of a long series of experiments on animals before the possibility of trying out the procedure on humans could even be contemplated. An ethical debate would be necessary as well.

If sanctioned, however, it could be possible to repair inherited genetic defects before birth. Diseases such as cystic fibrosis and muscular dystrophy could one day be tackled this way.

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See also:

04 May 00 | Health
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27 Apr 00 | Sci/Tech
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