London: Moths, caterpillars and fruit flies could soon take the place of millions of mice used every year by scientists testing drugs, researchers
said on Tuesday.
Biologists have discovered that certain key cells in mammals and insects react in the same way when attacked by infections and produce similar chemical reactions to fight them off.
Some 85% of all mammals used in experiments are rodents - most of them mice. They are favoured partly because they are small and relatively easy to study in laboratories, and breed rapidly so can show changes through generations relatively quickly. The findings could mean up to 80% 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.
"This method of testing is quicker, as tests with insects yield results in 48 hours whereas tests with mice usually take 4 to 6 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 haematocytes, 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. "The reason for this is that the innate immune system of mammals is almost 90 percent similar to that of insects."
"The cost of caring for, housing and feeding a mouse for use in experiments can reach between $80 to $130 per mouse, while a caterpillar, for example, costs as little as $0.16 to $0.32," Kavanagh said.
His research was carried out in conjunction with a drug discovery company in Britain, which needed to test some 700 potential new drug compounds. "That would have required about 14,000 mice," said Kavanagh. "But instead they carried out a lot of the screening work in insects, and narrowed down the number of compounds to around 35, which they subsequently tested in mice. That reduced the mount of mice by about 80%."