By ROBERT E. COIFMAN, M.D.
As an allergy practice we see patients with chronic and recurrent poison ivy. As there are no commercially available poison ivy allergy vaccines with standardized allergen content and proven effectiveness, we decided to make our own. We harvest fresh poison ivy leaves from a farm in Salem County and made our first three lots of vaccine according to a method provided by a scientist in Mississippi who worked with poison ivy in the past.
The vaccine we made using these methods is effective for the treatment of highly allergic patients but not strong enough to treat patients whose allergy is only moderate. We are working with scientists in the Department of Chemistry and Biochemistry at Rowan University to develop more highly purified and concentrated vaccines and hope to have vaccines capable of treating all levels of poison ivy allergy by the end of this year. Our first two lots of vaccine were assayed (which means to measure how much of the active ingredient is in the vaccine) by a scientist at the US Department of Agriculture who ran our samples together with those he was studying for a project to measure the effects of climate change on allergenic plants.
Poison ivy grown under the climate change condition of increased levels of carbon dioxide produces more allergen than under present environmental conditions. Our colleagues at Rowan now have their own assay, making it practical for us to study the stability of our vaccines over time.
Our first highly allergic patient was a tree trimmer. He was 15 times less sensitive to poison ivy after treatment than before, and he spent the first summer since he’s been in that business without any reactions from exposure in the course of his work. Our second highly allergic patient, a 15-year-old girl, was 22 times less sensitive after treatment than before, and was also less sensitive to natural contact.
The intensity of a patient’s sensitivity is evaluated with standardized skin tests, in which a small amount of the chemicals that cause a reaction in ivy is placed on the arm. The test starts with a very small amount, to prevent hurting the patient, and builds until a reaction occurs. That determines the amount of vaccine to use.
The whole idea is by putting something inside the body, we can train the body to tolerate the material. While there are sometimes reactions to the skin test, we have never seen a reaction from the treatment itself.
The traditional way to deliver allergy vaccines that aren’t soluble in water is to dissolve them in purified corn oil and inject them under the skin. We decided to dissolve our vaccine in alcohol and inject it into muscle, not because we had any reason to know in advance that it would be more effective, but simply because outside of an industrial setting it’s hard to sterilize a vaccine dissolved in corn oil while alcohol sterilizes itself. We were therefore pleasantly surprised to discover that injecting it into muscle in alcohol is about 200 times as effective at reducing allergic reactivity as injecting it under the skin in corn oil. Our Rowan chemistry colleagues are working on methods to prepare a formulation of peanut allergen with the same solubility properties as our poison ivy vaccine, and an immunology research professor at University of Pennsylvania will be working with us to study its ability to reverse peanut allergy in mice.