Shock therapy

时间:2019-03-08 07:08:17166网络整理admin

By Nell Boyce in Washington DC PEOPLE with life-threatening food allergies may one day be able to eat what they like if an experimental oral DNA vaccine works as well in humans as it does in mice. In certain people, a mere trace of foods such as peanuts or shellfish can trigger an immune reaction that can result in fatal anaphylactic shock. Their only defences are to try to avoid the danger foods, and to carry a syringe of adrenaline in case this fails. It would be far better to prevent such reactions by desensitising the immune system. With some allergens, this can be done by injecting a series of increasing doses under the skin. But attempts to treat food allergies in this way have mostly failed. Now, Kam Leong and his colleagues at Johns Hopkins University in Baltimore have come up with a new approach. They took a loop of DNA that encodes for the protein from peanuts that is mainly responsible for the allergic response, and encapsulated it in a biodegradable and safe polysaccharide called chitosan. They fed the vaccine to mice predisposed to go into shock when exposed to the peanut protein. A marker gene in the DNA loop showed that it was being taken up by cells in the intestinal walls of the mice, which began producing the protein. When untreated mice were injected with the peanut protein they went into shock: their breathing became spasmodic, they failed to respond when prodded—and some died. But mice treated with the encapsulated DNA did not show such severe responses (Nature Medicine, vol 5, p 387). Feeding mice unencapsulated DNA didn’t work. The researchers are not sure why peanut protein expressed by the animals’ own cells leads to tolerance, when treating them with the allergen itself does not. They now want to expand the idea into other DNA vaccines. But William Cookson, an allergy specialist at the John Radcliffe Hospital in Oxford, cautions that that while the approach is interesting, it’s a long way from clinical use. Meanwhile, Hugh Sampson at the Mount Sinai School of Medicine in New York City is trying a different approach. He is subtly altering the main peanut allergen,