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Scientists are working to develop vaccines against food allergies. As this ScienCentral News video reports, allergy researchers are using genetics to help create those vaccines.
Food Fears
For people with severe food allergies, hospitalization or even death can be a peanut away. Food allergies cause a 150 deaths a year in the United States, with just six foods - milk, egg, peanuts, tree nuts, fish and shellfish - blamed for 90 percent of all allergic reactions to foods.
Since simply avoiding the culprit food isn't so simple, doctors also train food-allergic patients to carry around a life-saving injection, such as epinephrine, in case they begin to experience symptoms of anaphylaxis, which can be set off by mere traces of the allergic food.
"Basically right now, we can only try to help you prevent it, and give you medication in case you experience a reaction; we don't really have what we call an 'active' way to treat it," says Hugh Sampson, professor of pediatrics and immunology at Mount Sinai School of Medicine in New York.
People with food-allergies have emergency devices like this to administer an emergency injection of epinephrine.
But food allergy researchers like Sampson are working to change that, developing vaccines that could ease, or possibly even cure, food allergies. His lab genetically engineered bacteria to produce the proteins in peanuts that cause allergic reactions. "We've identified the genes in the peanut plant that make these proteins, we've altered those genes in such a way that this protein will no longer cause an allergic reaction when we give it to somebody, but it will turn off that patient's allergic response to peanut," he explains.
The bacteria they used were E. Coli like those normally found in our bodies. They killed the bacteria and put them into a suppository that they gave to mice with peanut allergy. As they wrote in the Journal of Allergy and Clinical Immunology, the killed bacteria triggered the immune systems' of the mice to react protectively when they were exposed ("challenged") to peanuts. That protective immune system reaction overwhelms the allergic reaction, the researchers say.
"When we challenge mice who are [allergic] to peanut, but who have been treated with a placebo, or a sham treatment, basically all the mice will have a fairly severe allergic reaction," says Sampson. "When we challenge the mice that receive what we call our 'high dose' of our therapy, of our vaccine therapy, virtually none of the mice have any reaction whatsoever."
"We always thought if it was a dirty environment that this was bad for health, so this was an astounding finding," says Frick. "And from there came these bacteria that actually do a good thing because it revs up the immune system."
Dogs that received the vaccine were able to eat 100 times more the amount of peanuts than dogs that did not.
Frick and other researchers at UCSF, University of California at Davis and Stanford University tested a different type of bacteria-based vaccine in dogs bred to have food allergies like people. They used a killed bacteria called listeria combined with the peanut allergy proteins. They also tested vaccines against milk and wheat allergies.
"The listeria is a very severe infection," Frick says, "but because of that, it gives a very, very strong protective antibody response," adding, "These listeria are heat-killed and they're cultured several times to make sure they really are killed."
They reported in the journal Allergy that dogs that normally react to eating half a peanut could tolerate as much as 100 times that amount for several months after one shot of the vaccine.
Frick explains that since the dogs have multiple allergies, they were their own control group. "Dogs that were allergic to beef and to ragweed, as well as peanuts, were protected against peanuts, but they still did react to beef and to ragweed," he says.
But the researchers say since listeria is so dangerous, they plan to refine the vaccine before planning any tests in people. "This needs to be broken down into single components of the heat-killed bactera that may work, instead of using the whole killed bacteria," explains Suzanne Teuber, associate professor at University of California, Davis School of Medicine.
Sampson says his lab chose E. Coli because it is likely to prove safer. "We're actually using a bacteria that's found normally in everybodys gastrointestinal tract," he says. "Delivering it there where it's in a heat-killed form amongst other similar bacteria, there's no safety concern."
Sampson says the drawback to the vaccines is that we need to make separate vaccines for each individual food. That may not seem like a big drawback compared to their ability to not just treat but possibly cure food allergies.
"We're hoping it will actually educate the immune system to turn it off permanently," he says, "and then hopefully it will be gone from that time forward."
And Teuber points out that even an increase in tolerance, like they saw in the dogs, would be a big boon for people. "If we can increase the amount of peanut that must be eaten before a person has a reaction, it could save lives," she says.
Volunteers Needed
Volunteers will have to be brave.
Sampson says the next step for his vaccine is human tests. But he points out it's not that easy to recruit volunteers.
"One of the problems whenever we do any trials like this, is we need to be able to show that people are getting significant protection, so to do that we have to have people who will volunteer to come into the hospital to actually undergo a peanut challenge," Sampson says. "So in essence we're feeding them peanut, starting with very small doses and increasing it to see what dose initiates their allergic symptoms. Then they are randomized to receive either the drug or a placebo."
After the treatment, the volunteers - who like the researchers would not know whether they received the drug or the placebo - would then come back and get another challenge, to see how much protection they have. And for somebody who has had a peanut allergy reaction, this can be a somewhat scary proposition.
Sampson's most recent study was published in the May 2004 issue of the Journal of Allergy and Clinical Immunology, and was funded by the NIH, the Sosen Foundation, and the Food Allergy Initiative. Frick et al's study was published in the November 2004 issue of the journal Allergy, and was funded in part by a grant from the Lucile Packard Foundation for Childrens Health, the NIH, and a gift from Howard and Susan Sosin.
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