Ugly bugs make drugs

日期:2019-02-26 08:08:01 作者:喻呈 阅读:

By Andy Coghlan THE larvae of moths and butterflies that plague gardeners could soon be put to work making drugs to save lives. “Instead of larvae eating your cabbages, you can make pharmaceuticals in them,” says Alan Wood who heads the team at the Boyce Thompson Institute for Plant Research, at Cornell University in Ithaca, New York. The researchers infect the insects with viruses that trick them into making any protein they want. Wood and his colleague Patrick Hughes have experimented with the larvae of several moths and butterflies, including those of the monarch butterfly ( Danaus plexippus), the silkworm (Bombyx mori), the gypsy moth (Lymantria dispar) and the tobacco hornworm (Manduca sexta), which has larvae the size of cigars. But the highest yield so far has come from the larvae of the cabbage looper moth (Trichoplusia ni) —the scourge of cabbage farmers around the world. Large quantities of the proteins can be made and extracted within days at a fraction of the usual cost. A single incubator, the size of a suitcase, can take up to 9000 individual larvae, churning out 25 grams of a protein in just three days. Hughes discovered that he could cram the insects into such a tiny space by giving each individual a lollipop-shaped stick, to mimic a plant stem or leaf surface. The larvae crawl down their supports to a food tray at the base of the incubator. When they reached a certain point in their life cycle, the researchers spiked the food with a baculovirus engineered to carry the gene for making a pharmaceutical protein. These viruses only affect arthropods. The viruses carry the gene with them into every cell they infect, turning the larvae into miniature protein factories. The team freeze-dries the insects just before they succumb to the viral infection. The timing is critical —if the larvae die naturally, their bodies are flooded with enzymes that rapidly digest and destroy the key protein. Later the researchers defrost the larvae, squash them to a pulp and extract the protein by standard separation methods, such as chromatography. So far, the team has made “marker” proteins which show that the system works in principle. These include luciferase, an enzyme from fireflies which glows, and beta galactosidase, which turns blue when exposed to standard reagents. Now, the institute is working with drugs companies to test out the system for generating proteins that have proven medical value such as insulin or human growth factor. Wood says that he expects their technique to yield 10 to 100 times as much protein per gram of insect as a comparable system based on fermenters full of insect cells that have been genetically engineered to make a protein. “We expect costs to fall tenfold as well,