Poison oak and poison ivy are plants that nearly everybody inNorth America loves to loathe. But for the workers who cannotavoid the rash-inducing weeds, Allergene Inc. thinks it has ananswer.
The private San Mateo, Calif., company is presenting resultstoday at the annual meeting of the American Association ofImmunologists in Denver showing how mice were able todown-regulate their allergic reaction after treatment with amonoclonal antibody (MAb) that is expected to work morerapidly in people than traditional desensitization shots. (Shotsof crude allergy extracts may take years to fully protectrecipients.)
"Allergies are an inappropriate response of the immunesystem," explained William Friedman, Allergene's chiefexecutive officer and chairman. "An anti-idiotypic antibody(such as the compound given the mice) is how the body rightsitself. We're providing nature's own shortcut."
When the immune system responds to allergy-provokingsubstances by producing antibodies and regulatory T cells, italso makes an image of the allergen in the anti-idiotypicantibody.
Long after the MAb based on this compound left thebloodstream of the treated mice, the animals still resistedrashes from poison ivy, Friedman said, indicating that thetreatment stimulated the rodents' immune response.
"We're not merely sopping up antigens," he said. Another studyshowed that the mice down-regulated their allergic reactioneven when they were injected with 1,000 times more antigenthan anti-idiotypic antibody.
The 3-year-old company focused on poison oak and poison ivybecause its president and science director, Vera Byers, hasstudied these allergens for years.
"We believe that (the MAb) ALG991 represents the first of anew class of antibodies that we term 'regulatory antibodies,' "she said. "In contrast to typical antibodies that bind to foreignsubstances and clear them from the body, regulatoryantibodies play a critical role in the allergic cascade by limitingthe body's response."
In the placebo-controlled study, mice were first made sensitiveto urushiol, the toxic oil in poison ivy (as well as poison oak,poison sumac, poison vine and even the lac plant that makeslacquer). The mice were treated, then re-challenged withpoison ivy after two weeks. Treated animals did not react tothe second exposure, while placebo-controlled mice had fullreactions.
A leading authority on poison ivy reaction, William Epstein,emeritus chairman of the Department of Dermatology of theUniversity of California, San Francisco, said the results areespecially important to fire fighters, telephone lineman,members of the military and Forest Service employees, whocannot avoid serious exposure.
"Available treatments today are either difficult to use or areonly effective after the rash develops," Epstein said.
Dale Robertson, chief of the U.S. Forest Service, estimated thatup to one-third of the agency's fire fighters are forced to leavethe line during a fire because of severe blistering rashes orother complications of exposure.
Allergene said it expects to enter clinical trials with a modifiedform of the antibody in about 18 months. The primary market,Friedman said, is the 100,000 to 200,000 outdoor workers whocannot avoid exposure. He anticipates that market willrepresent about $50 million in annual revenues.
A full 1.2 million Americans seek medical treatment annuallyfor exposure to poison oak or poison ivy, but might have lessincentive to seek the series of two or three injections thecompany forecasts will prevent reactions, he added.
Larger allergy markets targeted by Allergene include hay feverand asthma. Important allergens, such as dust mites, pollensand molds, incite irritated eyes and drippy noses in hay feverand spasmodic clamping of the airways in asthma, which alsocan be triggered by cold air, emotions or exercise.
"The same immune mechanisms are at work," Friedman said.The potential treatment involves allergen-specific compoundsmodeled on anti-idiotypic antibodies in these diseases, too.
Allergene is sponsoring research at the University ofNottingham, England, where MAb experts have collaborated onthe work being presented today in Denver.
-- Nancy Garcia Associate Editor
(c) 1997 American Health Consultants. All rights reserved.