By Marie-Helene Jouvin
There is evidence that the prevalence of allergic diseases in the developed world has been increasing since the 1980’s. The mechanisms responsible for this change are unknown. One hypothesis that has been proposed is the hygiene hypothesis. This hypothesis is based on numerous observations showing a correlation between the environment in which children are raised and allergic diseases. For example, children raised on a farm or in a household with pets are less likely to develop allergies than children raised in a city or without pets. In developing countries where parasitic infestation is common, skin reactivity to allergens is low, but it rises after treatment with antiparasitic drugs.
Children are born with an immature immune system that matures during the first months/years of life. One feature of this maturation is the acquisition of tolerance (= lack of reactivity) towards harmless germs present in the environment, harmless bacteria present in the gut and foods. The hygiene hypothesis proposes that in children raised in too clean an environment this maturation of the immune system is altered in a way that leads to an increased risk of developing allergic and autoimmune diseases. Experiments performed in lab mice support this hypothesis. Note that the fact that in allergic individuals symptom flares are often triggered by infections does not contradict the hygiene hypothesis. According to the hypothesis allergic individuals have a skewed immune system and a low level of chronic inflammation, which can make them more susceptible to common infections and to allergic symptoms. In addition, the hypothesis does not propose that any infectious agent can promote immune maturation.
A therapy for allergies based on the hygiene hypothesis would need to be simple and safe, and work in individuals who are already allergic.
Epidemiological studies in humans and experimental studies in animals suggest that parasites of the helminth family have the capacity to protect against allergic diseases. In particular one member of the helminth family, Trichuris suis (T suis), appears to be an attractive candidate as a drug. Clinical trials have already been conducted with the eggs of T suis (T suis ova, TSO) in patients with inflammatory bowel diseases, such as Crohn’s disease and ulcerative colitis. They have shown that TSO is safe and effective in these patients.
Dr Kinet and myself, at the Beth Israel Deaconess Medical Center in Boston, are conducting a trial of TSO in individuals with peanut or tree nut allergy. Because TSO is an experimental drug, this trial is being conducted under the supervision of the FDA. We are running the safety phase of the study in which a few individuals will receive the drug and be monitored for any side effect. The cost of the study is covered by a grant from the Food Allergy Initiative foundation.
Subjects allergic to peanut or tree nuts and aged 18 to 64 may be eligible. All study visits will take place at the Allergy Clinic at Brigham and Women’s Hospital, 850 Boylston St. Chestnut Hill, MA. Eligible subjects will be asked to complete 10 outpatient visits over 4 months. Most visits will take approximately 30 minutes. Subjects will be reimbursed $20.00 per visit completed and up to $20 for parking or transportation for each visit.
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