Comparative study of tolerance between unmodified and high doses of chemically modified allergen vaccines of Dermatophagoides pteronyssinus.

BACKGROUND: The physiochemical modification of allergens to reduce allergenicity, while retaining immunogenicity, provides a chance for the administration of higher doses of immunotherapy, with a decreased risk of systemic reactions. OBJECTIVE: To evaluate the safety of doses of depigmented glutaraldehyde-polymerized vaccine of Dermatophagoides pteronyssinus increasing those used in normal clinical conditions in comparison with regular doses of a non-modified vaccine. MATERIALS AND METHODS: The study was double-blind, parallel and included two patient groups. Twenty-three patients were treated weekly during 9 visits for the build-up phase, followed by 2-weekly maintenance doses (a total of 11 injections per patient). Eleven patients (mean age 22 years) received immunotherapy with the standardized modified vaccine. The maximum dose used was the result of depigmenting and polymerizing 100 times the maximum dose used with the native extract. The maximum concentration used was 990 mug/ml of freeze-dried material. Twelve patients (mean age 24 years) received a standardized, unmodified allergenic extract. The maximum concentration used was 70 mug of freeze-dried material/ml, with a potency of 10 HEP(L)/ml. The tolerance was evaluated recording all the side reactions related to immunotherapy and graded following the recommendations of the European Academy of Allergology and Clinical Immunology. RESULTS: In both groups, all immediate local reactions were clinically not relevant. Patients treated with the native extract experienced 42 local immediate and 24 delayed reactions (1 of them had a diameter >10 cm), whereas patients treated with the modified extract experienced 30 local immediate and 21 delayed reactions (2 of them had a diameter >10 cm). Four systemic reactions in 2 patients, 1 immediate of grade 1 and 3 delayed of grade 2 were reported in the group treated with native extract and 1 delayed of grade 2 in the group treated with the modified preparation. CONCLUSIONS: The modified extract of D. pteronyssinus, used at concentrations which are 10 times higher than those regularly administered in clinical practice, demonstrated to be safe to treat D. pteronyssinus-sensitive patients. The majority of the local reactions (immediate and delayed) were clinically not relevant (diameter <5 cm). No systemic reactions of grade 3 or 4 were noted.