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September 9, 2009

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Scientists make case for insect drug tests

MOTHS, caterpillars and fruit flies could soon take the place of millions of mice used every year by scientists testing drugs, researchers said in Scotland yesterday.

Biologists have found that certain key cells in mammals and insects react the same way when attacked by infections and produce similar chemical reactions to fight them off.

The findings could mean up to 80 percent of the mice used for testing new pharmaceutical compounds may no longer be needed, offering drug firms sizeable time and cost savings.

"It is now routine practice to use insect larvae to perform initial testing of new drugs and then to use mice for confirmation tests," said Kevin Kavanagh, a biologist from the National University of Ireland, who presented his research at a Society for General Microbiology meeting in Edinburgh.

"This method of testing is quicker, as tests with insects yield results in 48 hours whereas tests with mice usually take four to six weeks. And it is much cheaper too."

Kavanagh and his colleagues found that neutrophils, white blood cells that form part of the mammalian immune system, and hematocytes, cells that carry out similar work in insects, react in the same way to infecting microbes.

Both the insect and mammalian cells produce chemicals with a similar structure which move to the surface of the cells to kill the invading microbe, they found. The immune cells then enclose the microbe and release enzymes to break it down.

"We used insects instead of mammals for measuring how pathogenic a bacterium or fungus is, and found a very good correlation between the results in mammals and insects," Kavanagh said in a telephone interview.

"The reason for this is that the innate immune system of mammals is almost 90 percent similar to that of insects."

Kavanagh said this meant insects such as fruit flies, moths and their caterpillars could be used to test new antimicrobial drugs or to judge how virulent fungal pathogens are.

About 85 percent of mammals used in experiments are rodents, most of them mice.

They are favored partly because they are small and relatively easy to study in laboratories, and breed rapidly so can show changes through generations relatively quickly.





 

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