A DOUBLE-BLIND-STUDY OF THE DISCONTINUATION OF RAGWEED IMMUNOTHERAPY

Background: Immunotherapy effectively treats the symptoms of allergic rhinitis and improves its pathophysiology. We studied whether the effe cts of immunotherapy on the early response to nasal challenge with ant igen and seasonal symptoms persist after discontinuation. Methods: Twe nty subjects with ragweed allergy who were receiving immunotherapy and who had nasal challenges performed before initiation of treatment wer e selected. The patients had been receiving maintenance therapy with a queous ragweed extract at a dose of 12 mu g of Amb a 1 equivalent for a minimum of 3 years, at which point they were randomized to receive e ither placebo injections or to continue with the maintenance dose. Nas al challenges were performed before and 1 year after randomization. Na sal challenges were monitored by counting the number of sneezes and me asuring histamine, N-alpha-tosyl-L-arginine methyl ester-esterase acti vity, and kinins in recovered nasal lavages. In the same year symptom diaries were collected during the ragweed season. Results: The initial immunotherapy significantly reduced responses to nasal challenge in b oth groups. The group continuing to receive active treatment showed no significant changes from the response before randomization. In contra st, the group randomized to placebo treatment showed a partial return of histamine, kinins, and N-alpha-tosyl-L-arginine methyl ester-estera se in nasal secretions and the numbers of sneezes. IgG antibodies to r agweed declined only in the group switched to placebo treatment, Seaso nal rises of IgE antibodies to ragweed did not return during the first season after treatment was stopped. Symptoms reported during the ragw eed season were not different between the groups. Conclusions: One yea r after discontinuation of ragweed immunotherapy, nasal challenges sho wed partial recrudescence of mediator responses even though reports du ring the season appeared to indicate continued suppression of symptoms .