Immunotherapy with a depigmented, polymerized vaccine of Olea europaea pollen allergens. Significantly reduces specific bronchial and skin test reactivity in sensitized patients after one year of treatment.

Clinical manifestations after the inhalation of Olea europaea pollen are very frequent in Spain. Forty-five patients with a clinical history of asthma and sensitivity to O. europaea pollen were included in a randomized trial to evaluate the safety and the clinical efficacy of immunotherapy with a new chemically modified extract (depigmented and glutaraldehyde-polymerized) of Olea europaea. The study was conducted following good clinical practices and appropriate consent forms were signed. Patients were divided into three groups of 15 individuals: Group A received a maximum concentration of 44 micrograms/ml of the depigmented, polymerized allergen extract (equivalent to 100 HEPL of the native unmodified extract). Group B received 10 times less; Group C did not receive any specific immunotherapy. Any adverse event was recorded to assess safety. Efficacy was evaluated by measuring the amount of allergen needed to elicit a positive response in specific bronchial challenges before and after 12 months of immunotherapy. The treatment schedule consisted of an incremental phase of five injections and a maintenance dosage of 0.5 ml per month. Each patient received a total of 14 injections during this period. No moderate or serious adverse events related to immunotherapy were recorded. At the beginning of the study, no significant differences were observed between the three groups in specific bronchial hyperreactivity (p > 0.05). A significant difference (p < 0.05) was obtained after 12 months. Patients in Group A needed four times more native unmodified allergen than Group C to elicit the same degree of bronchoconstriction. The analysis of the individual groups before and after 12 months of treatment showed that patients in Groups B and C did not improve. Patients in Group A showed a significant improvement (p < 0.05) in specific bronchial hyperreactivity, and at the end of the study needed 5.5 times more native unmodified allergen to obtain the same degree of bronchial response as in the beginning. Depigmented and glutaraldehyde-polymerized vaccines of Olea europaea pollen are very safe for treating patients with asthma and clinical sensitivity to allergens of this pollen. The clinical efficacy of this new allergen vaccine seems to be dose-dependent as shown by specific bronchial challenges as well as by symptom and medication scores. These modified extracts induce protection against unmodified native allergens.