Responses to ragweed-pollen nasal challenge before and after immunotherapy

To evaluate whether immunotherapy reduces mediator release after nasal challenge, we followed previously untreated patients with ragweed hay fever through 2 years (three seasons) of treatment. Eleven adult patients started immunotherapy after a season of symptom diaries and graded pretreatment challenges with 0.03, 0.3, 3.3, and 16.5 mg of ragweed pollen. Repeat challenges were performed when the treatment dosage reached 0.6, 12.4, and 24.8 μg of Amb a I (antigen E) equivalents per injection. After the 0.6 μg dose, there was little change, but after the larger doses, there was a significant reduction in histamine and tosylarginine methyl ester-esterase (TAME-esterase) release in two respects. More pollen was required before any mediator appeared, and the amount of mediator released at each stage of the challenge was reduced. There was no significant difference between the responses at the 12.4 and 24.8 μg treatment doses. Sneezing after challenge was not apparently changed after immunotherapy; however, patients' seasonal symptom-medication scores were reduced after treatment. These data set the optimal individual treatment dose of ragweed extract for immunotherapy at >0.6 μg, but probably not more than 12.4 μg in terms of Amb a I equivalents.