Monday, December 29, 2003


From the BBC for December 26 comes another cautionary tale from the world of gene splicing, recombinant DNA, GM foods, etc., etc.
A virulent form of tuberculosis was created in the laboratory by experts trying to alter its genetic structure.

The mutant form of the bug multiplied more quickly, and was more lethal than its natural counterpart.

Researchers from the University of California at Berkeley, US, had actually been trying to disable genes and make the bacterium less deadly. ...

The Berkeley study, published in the Proceedings of the National Academy of Sciences, concentrated on a particular collection of genes thought to give TB some of its virulence - its ability to infect.

They disabled these genes, and expected to find a weakened form of TB as a result. Instead, the organism grew in virulence.

It killed laboratory mice within seven months of exposure, while those infected with normal TB survived the experiment.

Further investigations suggested that the genetic changes had the unexpected effect of undermining the body's own immune response against TB.

Professor Lee Riley, who led the study, said: "These findings came as a complete surprise to us.

"We thought we had made a mistake, so we repeated the test several times, and we always got the same result."
The particular form of the bacteria is still treatable with antibiotics and in the natural world would probably be outcompeted by normal TB, since one of the things that gives the disease its persistence is that most people who carry the bacterium never get sick - that is, a mutation that quickly killed off its host would at the same time reduce its chances to reproduce and spread.

But it's a reminder that the Law of Unintended Consequences appears in all sorts of forms and guises and can't be cavalierly ignored, which is my main concern about genetic research of all types.

Footnote: The National Academy of Sciences website is here.

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